Title of Invention: Gas sensor, gas sensor cap, and gas sensor unit Abstract: The invention presents a gas sensor low in cost and easy to form a terminal member, a gas sensor cap connected to the gas sensor for sending an output signal to an external device, and a gas sensor unit capable of holding a stable electrically connected state between the terminal member of the gas sensor and the gas sensor cap. The gas sensor 100 of the invention includes a gas detecting element 120 and a terminal member 150. The terminal member 150 is made of a plate material bent and processed into a predetermined shape, and includes a tubular output-side terminal portion 151 electrically connected to a cap terminal 211 for sending an output signal of the gas detecting element 120, which is the output-side terminal portion 151 expanding elastically in diameter when connected to the cap terminal 211, and a tubular element-side terminal portion 153 connected electrically to an inside electrode 112, which is the element-side terminal portion 153 inserted into the gas detecting element 120 while contracting elastically in diameter. Detailed Description: Part general_description_paragraphs: Part TECHNICAL FIELD: The present invention relates to a gas sensor having a ceramic gas detecting element, a gas sensor cap put on the gas sensor for transmitting the output from the gas sensor to outside, and a gas sensor unit combining them. Part BACKGROUND ART: Hitherto, various devices have been proposed as gas sensors having ceramic gas detecting elements. These gas sensors have gas detecting elements made of zirconia ceramics of oxygen ion conductivity, for example, and are installed in exhaust pipes of an internal-combustion engine for detecting the oxygen concentration in the emission (see, for example, patent document 1 and patent document 2). [Patent document 1] Unexamined utility model application publication No. S53 (1978)-95884 [Patent document 2] Unexamined utility model application publication No. S53 (1978)-95886 Part DISCLOSURE OF THE INVENTION: Part Problem to be Solved by the Invention: The gas sensors disclosed in patent document 1 and patent document 2 have ceramic gas detecting elements in a tubular form with a bottom, and tubular terminal members for sending output signals from the gas detecting elements to outside. The terminal members are formed by processing a bar metal element (bar material or pipe material), and is hence expensive. Further, the terminal member has a high rigidity, and an elastic conductive packing is interposed between the terminal member and the gas detecting element so as to improve the electric connection with the inside electrode formed on the inner surface of the gas detecting element. As a result, the gas sensors disclosed in patent document 1 and patent document 2 are much more expensive. In patent document 1 and patent document 2, nothing is mentioned about a connecting cord for electrically connecting the gas sensor and an external device (for example, ECU), but there was a risk of causing noise due to momentary disconnection between terminal member of gas sensor and terminal of connecting cord by the influence of vibration or the like. Accordingly, there has been a desire for development of a gas sensor, an electric connection parts such as a connecting cord (a gas sensor cap) and a gas sensor unit comprising them, which are capable of holding a stable electric connection state between terminal member of gas sensor and external terminal (cap terminal) provided in connecting cord (gas sensor cap). The invention is devised in the light of such present circumstances, and it is hence an object thereof to present a gas sensor with a terminal member to be formed easily at low cost, a gas sensor cap being connectable to the gas sensor for transmitting an output signal to outside device, and a gas sensor unit capable of holding stable electric connection state between the terminal member of gas sensor and gas sensor cap. Part Means for Solving the Problem: The solving means is a gas sensor comprising: a gas detecting element, and a terminal member connected to an electrode formed on the gas detecting element, the terminal member being connectable to an external terminal for sending an output signal from the gas detecting element to outside, wherein the terminal member includes: an output-side terminal portion engageable and electrically connectable with the external terminal for sending the output signal, the output-side terminal portion having a plurality of contact points at which the output-side terminal portion elastically contacts with the external terminal to hold the external terminal in a direction orthogonal to a moving direction that moves at least either the external terminal or the output-side terminal portion relatively when the terminal member is connected with the external terminal, and an element-side terminal portion electrically connected to the electrode. In the gas sensor of the present invention, the output-side terminal portion of the terminal member has a plurality of contact points elastically contacting with the external terminal in the direction orthogonal to the moving direction. Therefore, when the external terminal and the output-side terminal portion of the terminal member are connected, the output-side terminal portion contacts with the external terminal at the plural contact points and also elastically presses the external terminal and is electrically connected thereto. That is, conduction between the gas sensor and the external terminal can be assured through the plural contact points, and each contact point is pressed elastically. It hence lowers the risk of causing noise or the like (risk of decline of gas detection accuracy) due to momentary disconnection between the external terminal and the output-side terminal portion by the effects of vibration or the like. Moreover, since the output-side terminal portion of the gas sensor is elastically connected to the external terminal in the orthogonal direction, it is easy to attach to or detach from the output-side terminal portion by moving the external terminal relatively in the moving direction. Furthermore, it is the role of the output-side terminal portion to elastically contact with and hold the external terminal at the plural contact points in the orthogonal direction, and the shape of the output-side terminal portion can be selected so properly as to effectively have the plural contact points in accordance with the shape of the external terminal. The shape of the output-side terminal portion should be different depending on the shape (form) of the external terminal, but, for example, a plate material may be rolled into tubular shape with a substantially C-shaped section orthogonal to the axial direction. A plate material may also be rolled into a tube by overlapping in part. In these forms, the output-side terminal portion elastically winds around the outer surface of the external terminal from its outside, or elastically presses to the inner surface of the tubular external terminal from the inside in the radial direction and expands it, thereby connecting with the external terminal. Accordingly, the output-side terminal portion has the plurality of contact points in surface or line contact with the outer surface or the inner surface of the external terminal depending on the form of the external terminal. Or plural contact points may be formed by contacting with protrusions formed the outer surface or inner surface of the external terminal. In the output-side terminal portion of these forms, the moving direction is the direction along the axis of the output-side terminal portion, and the orthogonal direction is the radial direction of the output-side terminal portion. In the output-side terminal portion formed by winding the plate material like a tube with a C-shaped section orthogonal to the axial direction or winding the plate material like a tube by overlapping in a part, further, one or plural protrusions may be formed so as to contact with the external terminal. The output-side terminal portion may be formed in circular, polygonal or other shape in the sectional form orthogonal to the axial direction. Further, the portion enclosed by two slits extending in the direction along the axial direction formed at the side surface of the cylindrical or tubular main body may protrude in arcuate shape toward the radially outer or inner side, and slit protrusions elastically movable in the radial direction may be scattered and disposed in plural positions along the periphery of the tubular main body. Moreover, on the side surface of cylindrical or tubular main body, leading ends of tongue portions formed by a U-shaped slit may protrude, obliquely toward the radially outer or inner side, and the tongue-like protrusions movable elastically in the radial direction may be scattered and disposed in plural positions along the periphery of the cylindrical main body. In the output-side terminal portion of the gas sensor mentioned above, the plural contact points may be disposed on a virtual cylinder passing them, and the plural contact points may be designed to move so as to expand or contract the diameter of the virtual cylinder in diameter when connected to the external terminal. In the gas sensor of the invention, the plurality of contact points of the output-side terminal portion is disposed on a virtual cylinder passing them, and the contact points move so as to expand or contract a diameter of the virtual cylinder when the output-side terminal portion is connected to the external terminal. Therefore, when the external terminal and the output-side terminal portion of the terminal member are connected, the output-side terminal portion contacts with the external terminal at plural contact points, and is electrically connected with the external terminal while elastically pressing the external terminal to the radially outer or inner side of the virtual cylinder. That is, the contact points conducting between the gas sensor and external terminal are elastically pressing from the radially outer or inner side. Hence, momentary disconnection between the external terminal and the output-side terminal portion by vibration and the like can be prevented, attaching to or detaching from the external terminal is easy. Furthermore, when the output-side terminal portion and the external terminal are connected, the output-side terminal portion and external terminal can be connected from any direction without depending on connection directions around the axis of the virtual cylinder and thereby be installed more easily. The virtual cylinder is formed by axially extending a virtual circle of a specific diameter, and the plural contact points are disposed on this virtual cylinder. When the plural contact points are positioned on one virtual circle, these plural contact points are same in the positions in the axial direction on the virtual cylinder, and are disposed at different positions in the peripheral direction. In the form of the output-side terminal portion having plural contact points elastically contacting with the external terminal, and disposed on the virtual cylinder, and moving the contact points so as to expand or contract the diameter of the virtual cylinder when connected to the external terminal, though variable with the shape (form) of the external terminal, same as mentioned above, for example, a plate material may be wound like a tube, and the section orthogonal to the axial direction may be formed in a C form, or a plate material may be wound like a tube by overlapping in part. When the output-side terminal portion of these forms is connected to the external terminal of solid bar or hollow tube with a cylindrical outer surface, the output-side terminal portion contacts with the external terminal as if winding around the cylindrical outer periphery of the external terminal. In this case, therefore, it is in surface or line contact with the outer periphery of the external terminal and multiple contact points are present. These contact points are disposed on the virtual cylinder coinciding with the outer periphery of the external terminal. On the other hand, when the output-side terminal portion of these forms is not connected to the external terminal but is in free state, the contact points (positions planned to be contact points) are disposed on a virtual cylinder of smaller diameter than mentioned above. That is, in these output-side terminal portions, when connected to the external terminal, the contact points move so as to expand the diameter of the virtual cylinder. Using similar output-side terminal portions, when connected to the external terminal having plural protrusions projecting toward the radially outer side on the outer periphery, the output-side terminal portions contact with the external terminal so as to wind around the outer periphery of the external terminal, but the plural portions abutting with the peaks of protrusions of the external terminal become the contact points, and the contact points are disposed on the virtual cylinder. In free state, on the other hand, these contact points are disposed on the virtual cylinder of smaller diameter. Also in this case, in these output-side terminal portions, when connected to the external terminal, the contact points move so as to expand the virtual cylinder. Further, the slit protrusions may be scattered and disposed at plural positions in the peripheral direction of the cylindrical main body, or the tongue-like protrusions may be scattered and disposed at plural positions in the peripheral direction of the cylindrical main body. In the gas sensor as set forth in claim 1 or claim 2, the gas detecting element is composed of ceramics, having a tubular form with a bottom closed at a leading end side in an axial direction of the gas detecting element, the electrode is an inside electrode formed on an inner surface of the gas detecting element, the terminal member is made of a plate material bent and formed in a predetermined shape, the output-side terminal portion is tubular, and is elastically expanded or contracted in diameter when connected to the external terminal, and the element-side terminal portion is tubular, and inserted as being elastically contracted in diameter in the gas detecting element, the element-side terminal portion being electrically connected to the inside electrode. The gas sensor of the invention has the tubular output-side terminal portion being elastically expanded or contracted in diameter when connected to the external terminal. Therefore, when the external terminal and output-side terminal portion are connected, the output-side terminal portion is electrically connected while pressing the external terminal to the radially outer or inner side. It hence lowers the risk of causing noise or the like (risk of decline of gas detection accuracy) due to momentary disconnection between the external terminal and the output-side terminal portion by the effects of vibration or the like. Moreover, since the output-side terminal portion of the gas sensor is connected to the external terminal by its own (plate material) elasticity, it is easy to detach from or attach to the external terminal. It further comprises a tubular element-side terminal portion which is elastically contracted in diameter when inserted into the gas detecting element, and electrically connected to the inside electrode. In this gas detecting element, therefore, the element-side terminal portion is electrically connected to the inside electrode while pressing the inside electrode from the inside to the radially outer side. It hence lowers the risk of causing noise or the like due to momentary disconnection between the two by the effects of vibration or the like. Moreover, since the element-side terminal portion is elastically contracted, it can be connected directly to the inside electrode. Thus, as compared with the conventional case of using an elastic conductive packing, since the conductive packing is not needed, the number of parts is curtailed, and the cost is reduced. The terminal member having such output-side terminal portion and element-side terminal portion is formed of a plate material bent and processed into a predetermined shape. Hence, the terminal member itself is easy to form and low in cost. The terminal member of the invention may be formed by connecting plural members of bent and processed plate materials by a welding or other method, but preferably it should be formed by using a single metal plate, and processing the output-side terminal portion and element-side terminal portion into a tubular form respectively. The tubular form of the output-side terminal portion and element-side terminal portion is obtained by, for example, forming the section orthogonal to the axial direction in a C-form. Or the plate material may be wound in a tubular form by overlapping in part. The sectional form orthogonal to the axial direction is not limited to the C-form, but may include circular or polygonal shape. In the gas sensor, preferably, the inside of the gas detecting element and the outside of the gas sensor should communicate with each other through the inside of the output-side terminal portion and element-side terminal portion of the terminal member. As mentioned herein, the terminal member of the invention is formed of a bent and processed plate member, and has tubular output-side terminal portion and element-side terminal portion. Through the inside (in the tube) of the output-side terminal portion and element-side terminal portion, the inside (in the tube) of the gas detecting element and the outside of the gas sensor communicate with each other. In other words, the terminal member composes a ventilation passage for introducing reference gas (outer air) into the inside of the gas detecting element. Hence, in the gas sensor of the invention, it is not needed to form ventilation passage specially for introducing reference gas (outer air) into the inside of the gas detecting element, and the terminal member does not require an extra process of forming ventilation passage (for example, piercing process), so that the cost is lowered. In the gas sensor, preferably, the element-side terminal portion of the terminal member is positioned at the leading end side in the axial direction from the output-side terminal portion. By defining such configuration relation of the output-side terminal portion and element-side terminal portion, it is easy to form the terminal member, and the cost of the gas sensor is lowered. Moreover, since the ventilation passage formed by this terminal element is extended in the axial direction, it is easier to introduce the reference gas (outer air) into the inside of the gas detecting element. In any one of the gas sensors mentioned above, the output-side terminal portion is elastically contracted in diameter when inserted in the external terminal and connected thereto, and the output-side terminal portion has a rear end portion inwardly bent and positioned at a rear end side in the axial direction. The terminal member formed of a bent plate material tends to be lower in rigidity as compared with one formed by processing a bar metal element. Of the terminal members, in particular, the output-side terminal portion connecting to the external terminal is likely to be loaded by effects of external vibrations, and lowering of rigidity is not preferred. In the gas sensor of the invention, by contrast, the rear end portion of the output-side terminal portion is bent inside, and the rear end is tapered to be smaller in diameter toward the end. Hence, the output-side terminal portion can be elastically contracted, and the rigidity is enhanced. Another solving means is the gas sensor as set forth in claim 1 or claim 2, in which the gas detecting element is composed of ceramics, having a tubular form with a bottom closed at a leading end side in an axial direction of the gas detecting element, the electrode is an inside electrode formed on an inner surface of the gas detecting element, the gas sensor further comprises a tubular enclosure made of insulating ceramics and surrounding the gas detecting element and the terminal member, the terminal member is made of a plate material bent and formed in a predetermined shape, the output-side terminal portion is tubular, and is elastically expanded in diameter when the external terminal is inserted in the output-side terminal portion for connection, thereby reducing a gap between an outer surface of the output-side terminal portion and an inner surface of the tubular enclosure than before insertion, and the element-side terminal portion is tubular, and inserted as being elastically contracted in diameter in the gas detecting element, the element-side terminal portion being electrically connected to the inside electrode. The terminal member of the gas sensor of the invention has the output-side terminal portion being elastically expanded in diameter when the external terminal is inserted in and connected to the terminal member, thereby reducing the gap between the outer surface of the output-side terminal portion and the inner surface of the enclosure smaller than before insertion of the external terminal. Therefore, when the external terminal is connected to the gas sensor of the invention, the gap between the inner surface of the enclosure and the outer surface of the output-side terminal portion is smaller than before connecting. Accordingly, in the gas sensor of the invention, the output-side terminal portion surrounded by the enclosure hardly oscillates in the radial direction even when it receives effects of external vibrations during use. This makes it possible to suppress fatigue rupture (crack, breakage, etc.) at the position between the output-side terminal portion and element-side terminal portion of the terminal member due to effects of vibrations. The terminal member of the gas sensor of the invention is also made of a plate material bent and processed into predetermined shape. Hence, the terminal member itself is easy to form and is low in cost. In the gas sensor, the element-side terminal portion of the terminal member may also be positioned at the leading end side in the axial direction from the output-side terminal portion. By defining such configuration relation of the output-side terminal portion and the element-side terminal portion, it is easier to form the terminal element, and hence the gas sensor is inexpensive. Further, the ventilation passage formed by this terminal member is extended in the axial direction, and it is easier to introduce reference gas (outer air) into the inside of the gas detecting element. In any gas sensor mentioned above, preferably, the terminal portion is made of a single plate material formed integrally. The gas sensor of the invention uses a terminal member formed integrally from a single plate material. Such terminal member is easy to form, and is hence low in cost. In any one of the gas sensors described above, preferably, the output-side terminal portion of the terminal member has a C-shape in section orthogonal to the axis of the output-side terminal portion. The gas sensor of the invention has the output-side terminal portion having a C-shape in the section orthogonal to the axis. Such output-side terminal portion is easy to form, and is wide in deformation region, and hence an output-side terminal portion having elasticity of relatively large coefficient of elasticity is realized, so that the external terminal can be held firmly. Another solving means is a gas sensor cap connectable to a gas sensor having a gas detecting element and a terminal member having an output-side terminal portion for sending an output signal from the gas detecting element to outside, for transmitting the output signal to an external device, the gas sensor cap comprising: a cap terminal engageable and electrically connectable with the output-side terminal portion, a cover made of insulating rubber and formed to cover the cap terminal, and a lead wire connected electrically to the cap terminal for transmitting the output signal to the external device, wherein the cap terminal has enough rigidity to move a plurality of contact points of the output-side terminal portion elastically contacting with the cap terminal so that a virtual cylinder passing the contact points is expanded or contracted in diameter when the cap terminal is connected to the output-side terminal portion. The cap terminal of the gas sensor of the invention has enough rigidity to move the plurality of contact points of the output-side terminal portion elastically contacting with the cap terminal so that a virtual cylinder passing the contact points is expanded or contracted in diameter when the cap terminal is connected to the output-side terminal portion. Therefore, when the output-side terminal portion and the cap terminal are connected (engaged), the contact points of the output-side terminal portion are electrically connected to the cap terminal while elastically pressing the cap terminal to the radially outer or inner side. It hence lowers the risk of causing noise or the like (risk of lowering the gas detection accuracy) by momentary disconnection between output-side terminal portion and cap terminal due to effects of vibrations. Preferably, the cap terminal is engageable with the output-side terminal portion of the terminal member of the gas sensor, and when engaged with the output-side terminal portion, it should have enough rigidity to move the plural contact points of the output-side terminal portion so as to expand or contract the diameter of the virtual cylinder on which the contact points are disposed, and it may be formed, for example, in circular columnar or cylindrical form. Although the outside diameter is changed in the axial direction, a cap terminal in the form of a solid bar or hollow tube, which has a taper shape, a reverse taper shape, or a small diameter in the middle of the axial direction, may be also used. Or a cap terminal of bell shape closed at one end may be also used. Another solving means is a gas sensor cap as set forth in claim 8, in which the output-side terminal portion of the terminal member in the gas sensor is tubular and capable of being elastically expanded or contracted in diameter, and the cap terminal is tubular, having enough rigidity for expanding or contracting, without deforming itself, the output-side terminal portion in diameter when the cap terminal is connected to the output-side terminal portion. The gas sensor cap of the invention has a tubular cap terminal having enough rigidity for elastically expanding or contracting the diameter of the output-side terminal portion of the terminal member without deforming itself when connected to the gas sensor. Therefore, when the output-side terminal portion and the cap terminal are connected (engaged), the output-side terminal portion is electrically connected to the cap terminal while elastically pressing the cap terminal to the radially outer or inner side. It hence lowers the risk of causing noise or the like (risk of lowering the gas detection accuracy) by momentary disconnection between the output-side terminal portion and the cap terminal due to effects of vibrations or the like. Besides, since the cap terminal and the output-side terminal portion of the terminal member are designed to be connected by the elastic force of the output-side terminal portion, detaching or attaching property of cap terminal in the output-side terminal portion of the terminal member may be enhanced. Another solving means is a gas sensor cap connectable to any one of the gas sensors mentioned above for transmitting the output signal to an external device, in which the external terminal is a tubular cap terminal engageable and electrically connectable with the output-side terminal portion, and includes: a cover made of insulating rubber and formed to cover the cap terminal, and a lead wire connected electrically to the cap terminal for transmitting the output signal to the external device, and the cap terminal has enough rigidity for moving the plurality of contact points of the output-side terminal portion for expanding or contracting the virtual cylinder in diameter when the cap terminal is connected to the output-side terminal portion. The gas sensor cap of the invention also has enough rigidity for moving the plurality of contact points of the output-side terminal portion disposed on the virtual cylinder for expanding or contracting the diameter of the virtual cylinder when the cap terminal is connected to the output-side terminal portion of the connection terminal of the gas sensor. Therefore, when the output-side terminal portion and the cap terminal are connected (engaged), the output-side terminal portion is electrically connected to the cap terminal while elastically pressing the cap terminal to the radially outer or inner side. It hence lowers the risk of causing noise or the like (risk of lowering the gas detection accuracy) by momentary disconnection between the output-side terminal portion and the cap terminal due to effects of vibrations or the like. Besides, since the cap terminal and the output-side terminal portion of the terminal member are designed to be connected by the elastic force of the output-side terminal portion, detaching or attaching property of cap terminal in the output-side terminal portion of the terminal member may be enhanced. Another solving means is a gas sensor unit comprising a gas sensor including a gas detecting element and a terminal member that is connected to an electrode formed in the gas detecting element and also is connected to an external terminal for sending an output signal from the gas detecting element to outside, and a gas sensor cap having a cap terminal serving as the external terminal connected to the terminal member of the gas sensor for transmitting the output signal to an external device, wherein the terminal member includes: an output-side terminal portion engaged and connected electrically with the cap terminal to send the output signal, the output-side terminal portion having a plurality of contact points at which the output-side terminal portion is elastically connected with the cap terminal along a direction orthogonal to a moving direction for relatively moving either the cap terminal or the output-side terminal portion when connected to the cap terminal. The gas sensor unit of the invention has a gas sensor and a gas sensor cap. The output-side terminal portion of the terminal member of the gas sensor has the plurality of contact points at which the output-side terminal portion is elastically connected with the cap terminal of the gas sensor cap along the orthogonal direction when connected (engaged) with the cap terminal. Since the output-side terminal portion has such configuration, in the gas sensor unit of the invention, the plural contact points of the output-side terminal portion are electrically connected to the cap terminal while elastically pressing the same. It hence lowers the risk of causing noise or the like (risk of lowering the gas detection accuracy) by momentary disconnection between output-side terminal portion and cap terminal due to effects of vibrations or the like. Besides, since the cap terminal and the output-side terminal portion of the terminal member are designed to be connected by the elastic force of the output-side terminal portion along the orthogonal direction, detaching or attaching property of cap terminal in the output-side terminal portion of the terminal member may be enhanced when attaching to or detaching from the output-side terminal portion by moving the cap terminal relatively in the moving direction, and thereby the gas sensor cap can be detached from or attached to the gas sensor smoothly. In the gas sensor unit described above, preferably, the plurality of contact points of the output-side terminal portion of the terminal member is disposed on a virtual cylinder passing them, and the contact points move so as to expand or contract a diameter of the virtual cylinder when the output-side terminal portion is connected to the cap terminal. In the gas sensor unit of the invention, the output-side terminal portion of the terminal member has the plurality of contact points elastically contacting with the cap terminal, being disposed on the virtual cylinder, and moves to expand or contract the diameter of the virtual cylinder passing these contact points when contacting with the cap terminal. Since the output-side terminal portion has such configuration, in the gas sensor unit of the invention, the plural contact points of the output-side terminal portion are electrically connected to the cap terminal while elastically pressing the same to the radially outer side or radial inner side. Hence, momentary disconnection between the output-side terminal portion and the cap terminal due to vibrations or the like can be prevented, and the cap terminal can be detached from or attached to easily the output-side terminal portion of the terminal member, and moreover when connecting the output-side terminal portion to the cap terminal, there is no dependence on connection direction around the axis of the virtual cylinder, and the output-side terminal portion and the cap terminal can be connected from any direction, and it is further easier to install the gas sensor and gas sensor cap in this gas sensor unit. In the gas sensor unit, preferably, the output-side terminal portion of the terminal member is tubular, and is elastically expanded or contracted in diameter when connected to the cap terminal, and the cap terminal is tubular, and is engaged with the output-side terminal portion by expanding or contracting the output-side terminal portion in diameter without deforming itself. The gas sensor unit of the invention mentioned above comprises a gas sensor and a gas sensor cap. Specifically, the terminal member of the gas sensor has a tubular output-side terminal portion which is elastically expanded or contracted in diameter when connected to the cap terminal of the gas sensor cap. The gas sensor cap is engaged with the output-side terminal portion by expanding or contracting the diameter of the output-side terminal portion without deforming itself. Therefore, in the gas sensor unit of the invention, the output-side terminal portion is connected electrically to the cap terminal while elastically pressing the same in the radially outer or inner side. It hence lowers the risk of causing noise or the like (risk of lowering the gas detection accuracy) by momentary disconnection between the output-side terminal portion and the cap terminal due to effects of vibrations or the like. Since the cap terminal and the output-side terminal portion of the terminal member are connected by the elastic force of the output-side terminal portion, it is easy to detach or attach the cap terminal from or to the output-side terminal portion of the terminal member, and hence the detaching and attaching property of gas sensor cap in the gas sensor can be enhanced. In the gas sensor unit as set forth in claim 11 or claim 12, preferably, the gas sensor has a tubular enclosure made of insulating ceramics and surrounding the gas detecting element and the terminal member, the output-side terminal portion of the terminal member is tubular, and is elastically expanded in diameter when the cap terminal is inserted in of the output-side terminal portion, and the cap terminal has enough rigidity to expand the output-side terminal portion in diameter without deforming itself when inserted in and connected with the inside of the output-side terminal portion, and the cap terminal is inserted in and connected with an inside of the output-side terminal portion, the output-side terminal portion being elastically expanded in diameter, providing a smaller gap than before insertion between an outer surface of the output-side terminal portion and an inner surface of the tubular enclosure. In the gas sensor unit of the invention, when the cap terminal is inserted in and connected to the output-side terminal portion, the output-side terminal portion is expanded elastically, and the gap between the outer surface of the output-side terminal portion and the inner surface of the enclosure becomes smaller than before insertion of the cap terminal. Hence, in the gas sensor unit of the invention, the output-side terminal portion surrounded by the enclosure hardly oscillates in the radial direction even when it receives effects of external vibrations. This makes it possible to suppress the fatigue rupture (crack, breakage, etc.) at the position between the output-side terminal portion and element-side terminal portion of the terminal member due to effects of vibrations. In the gas sensor unit of the invention, since the cap terminal and the output-side terminal portion of the terminal member are connected by the elastic force of the output-side terminal portion, the cap terminal can be easily detached from or attached to the output side terminal of the terminal member, so that the detaching and attaching property of the gas sensor cap in the gas sensor is enhanced. In any one of the gas sensor units described above, the gas detecting element is composed of ceramics, and has a tubular shape with a bottom closed at the leading end side in an axial direction of the gas detecting element, and the electrode is an inside electrode formed on the inner surface of the gas detecting element, and the terminal member is made of a plate material bent and formed in a predetermined shape and has a tubular element-side terminal portion inserted as being elastically contracted in diameter in the gas detecting element, the element-side terminal portion being electrically connected to the inside electrode. The gas sensor unit of the invention has a tubular element-side terminal portion which is inserted in the tubular gas detecting element with a bottom while elastically contracting, and connected electrically to the inside electrode. Therefore, in the gas detecting element in this gas sensor unit, the element-side terminal portion is connected electrically to the inside electrode while pressing the inside electrode from the inside to the radially outer side. It hence lowers the risk of causing noise or the like due to momentary disconnection of the two due to effects of vibrations or the like. Moreover, since the element-side terminal portion is elastically contracted in diameter, it can be connected directly to the inside electrode. As compared with the conventional method of inserting an elastic conductive packing, this conductive packing is not needed, and the number of parts is curtailed and the cost is reduced. The terminal member of the gas sensor unit of the invention is made of plate material bent and processed into predetermined shape. The terminal member is easy to form and is low in cost. In the gas sensor unit, preferably, the gas sensor cap has an inside space communicating with outside, and inside of the gas detecting element and the inside space of the gas sensor cap are in communication with each other through inside of the output-side terminal portion and inside of the element-side terminal portion of the terminal member. As described herein, the terminal member of the invention is made of a bent and processed plate material, and has a tubular output-side terminal portion and element-side terminal portion. Through the inside (in the tube) of the output-side terminal portion and element-side terminal portion, the inside (in the tube) of the gas detecting element and the inside space of the gas sensor cap communicate with each other. Further, the inside space of the gas sensor cap communicates with the outside. Therefore, in the gas sensor unit of the invention, the terminal member forms a ventilation passage for introducing outer air as reference gas into the inside of the gas detecting element by way of the inside space of the gas sensor cap. Hence, the gas sensor unit of the invention does not require particular ventilation passage for introducing the reference gas (outer air) into the inside of the gas detecting element, and the terminal member does not require the process (for example, piercing) of forming the ventilation passage, and hence the cost is lower. In any one of the gas sensor units, the terminal member is made of a single plate material formed integrally. The gas sensor unit of the invention uses a terminal member formed integrally from a single plate material. Such terminal member is easy to form, and is hence low in cost. In any one of the gas sensor units described above, the output-side terminal portion of the terminal member of the gas sensor has a C-shape in section orthogonal to its axis. In the gas sensor unit of the invention, the output-side terminal portion of the terminal member of the gas sensor has a C-shape in the section orthogonal to the axis. Such output-side terminal portion is easy to form, and is wide in deformation region, and hence an output-side terminal portion having elasticity of relatively large coefficient of elasticity is easily realized, so that the external terminal can be held firmly, and a reliable gas sensor unit is obtained. In any gas sensor unit, preferably, the gas sensor has a tubular enclosure made of insulating ceramics and placed to surround the gas detecting element and terminal member, the gas sensor cap has a cover made of insulating rubber and formed to cover the cap terminal, and this cover includes an enclosure cover portion covering at least part of the tubular enclosure of the gas sensor connected with the gas sensor cap. The gas sensor composing the gas sensor unit has an insulating ceramic enclosure surrounding the gas detecting element and terminal member. Hence, in a gas sensor unit having its enclosure exposed to outside, the ceramic enclosure may be broken when a foreign matter collides from outside. By contrast, in the gas sensor unit of the invention, the cover of the gas sensor cap, made of insulating rubber, includes the enclosure cover portion covering at least part of the enclosure when the gas sensor cap and gas sensor are connected. Hence, if a foreign matter collides against the enclosure from outside, the portion of the enclosure covered with the rubber enclosure cover portion can be protected from breakage. In the gas sensor unit, preferably, the enclosure cover portion of the gas sensor cap has an annular close-contact portion held circumferentially in close contact with an outer surface of the tubular enclosure, and the close-contact portion is in contact with an outer surface of a rear end portion of the tubular enclosure positioned at a rear end side in the axial direction thereof when the gas sensor cap is connected to the gas sensor. In the gas sensor unit of the invention, the enclosure cover portion made of rubber has an annular close-contact portion capable of making contact with the outer surface of the enclosure along the peripheral direction (360 degrees) thereof. Hence, invasion of water into the gas sensor unit from the gap of the gas sensor and gas sensor cap can be prevented. Incidentally, the gas sensor unit of the invention is, for example, installed in an exhaust pipe of an internal-combustion engine, and can be used for detecting the oxygen concentration in the emission. In this case, the gas detecting element is exposed to high temperature, and the gas detecting element and the metal casing surrounding the radial direction of the gas detecting element are heated to high temperature by the exhaust heat, and this heat is transmitted to the enclosure cover. By the effect of exhaust heat, the rubber enclosure cover portion (cover) may deteriorate. By contrast, in the gas sensor unit of the invention, the close-contact portion of the enclosure cover portion contacts with the outer periphery at the rear end portion positioned at the rear end in the axial direction of the enclosure when the gas sensor cap and gas sensor are connected. Therefore, the close-contact portion covers and protects the enclosure, and contacts (closely contacts) with the enclosure at a position remote from the gas detecting element at high temperature. Hence, the gas sensor unit of the invention lowers the risk of deterioration of rubber enclosure cover portion (cover) due to effects of exhaust heat. As the insulating rubber for composing the cover, a fluorine rubber is preferred. By using fluorine rubber, while having good heat-resistance, tight contact with the enclosure is assured. Part EXPLANATION OF REFERENCE NUMERALS: 100, 400 Gas sensor 112 Inside electrode 120 Gas detecting element 130, 430 Enclosure 150, 450, 750, 850 Terminal member 151, 451, 751, 851 Output-side terminal portion 153, 453 Element-side terminal portion 200, 500 Gas sensor cap 210, 510 Cap terminal member 211, 511 Cap terminal (external terminal) 220, 520 Cover 221, 521 Enclosure cover portion 221c, 521c Close-contact portion 230 Lead wire 300, 600 Gas sensor unit Part BEST MODE FOR CARRYING OUT THE INVENTION: Part Embodiment 1 : A first embodiment of the invention is described below while referring to the accompanying drawings. FIG. 1 is a partial sectional view of a gas sensor 100 in the first embodiment. The gas sensor 100 comprises a gas detecting element 120, an outside electrode 111, an inside electrode 112, an enclosure 130, a terminal member 150, and a casing 160. The casing 160 has a main body fitting 161 and a protector 162. The main body fitting 161 is made of SUS430, and is formed in a cylindrical shape. The main body fitting 161 has an inner peripheral supporting portion 161e for supporting a flange portion 120e of the gas detecting element 120 described below, that is, the tapered inner peripheral supporter 161e expanding in diameter toward the rear end is disposed on the periphery to protrude from the inner surface toward the radial inner side. Outside of this main body fitting 161, a threaded portion 161b is formed for fixing the gas sensor 100 in an exhaust pipe 10 (see FIG. 4), and in the rear end side of the threaded portion 161b has a hexagonal portion 161d for engaging with a mounting tool for screwing the threaded portion 161b into the exhaust pipe is formed. The protector 162 is a metal cylindrical tube, and has vent holes 162b for introducing the emission in the exhaust pipe 10 into the gas sensor 100. The gas detecting element 120 is composed of a solid electrolyte having oxygen ion conductivity, and has a cylindrical shape extending in axis C direction, having a bottom and closed at the leading end 120b. The flange portion 120e protruding outward in the radial direction is provided on the outer surface of the gas detecting element 120, and a metal packing 142 is inserted between the leading end of the flange portion 120e and the inner peripheral supporter 162e of the main body fitting 161, and the gas detecting element 120 is disposed in the main body fitting 161. As the solid electrolyte composing the gas detecting element 120, a representative example is ZrO2 with solid solution of Y2O3 or CaO, but a solid solution of ZrO2 with other oxide such as alkaline earth metal or rare earth metal may be used. Further, HfO2 may be contained. In this embodiment, the leading end 120b side in the axis line C direction of the gas detecting element 120 is the leading end side, and the opposite side is the rear end side. This relation is the same in the other embodiments. The outside electrode 111 is a porous material of Pt or Pt alloy, and is provided to cover the outer side 120c of the leading end 120b of the gas detecting element 120. The outside electrode 111 is disposed up to the leading end of the flange portion 120e, and is electrically connected to the main body fitting 161 by way of the packing 142. The inside electrode 112 is also a porous material of Pt or Pt alloy, and is provided to cover the inner surface 120d of the gas detecting element 120. The enclosure 130 is made of insulating ceramics (specifically, alumina), and has a cylindrical shape. The leading end portion 131 of the enclosure 130 is supported between the gas detecting element 120 and main body fitting 161, together with ceramic powder 141 formed of talc, in a manner to surround the periphery of the rear end portion of the gas detecting element 120. The terminal member 150 is made of, for example, SUS304, formed in a tubular shape as shown in FIG. 2, and has an output-side terminal portion 151, an element-side terminal portion 153, and a joint portion 152 for coupling them. The output-side terminal portion 151 has a tubular form in C-shaped section (see FIG. 2 (c)) orthogonal to its axis line 151AX (axis line 150AX of terminal member), and is designed to expand elastically when a cap terminal 211 (see FIG. 3) of a cap terminal member 210 is relatively moved in the direction along the axis line 150AX (in the vertical direction in FIG. 1), and inserted and connected into the inside. Further, at three positions in the peripheral direction of the rear end side (above in the diagram) of the output-side terminal portion 151, bumps 151b protruding in the radial inner side are formed. As shown in FIG. 2(c), the inside peaks of these three bumps 151b are contact points CP elastically abutting against the cap terminal 211 along its radial direction. Diameter E of a virtual circle and virtual cylinder HC (broken lines in FIG. 2(b), (c)) making contact with the contact points CP of the three bumps 151b is the inside diameter of the output-side terminal portion 151. Of the output-side terminal portion 151, three peripheral positions corresponding to the bumps 151b have an inside bent portions 151c folded at the radial inner side by blanking the wall surface, and outside bent portions 151d folded at the radially outer side. The inside bent portion 151c is formed to deflect elastically to the radially outer side when connected by inserting the cap terminal 211 (see FIG. 3) of the cap terminal 210 into the inside of the output-side terminal portion 151. The outside bent portion 151d, as shown in FIG. 1, abuts against the leading end surface of a shoulder 130b of the enclosure 130 when the terminal member 150 is assembled in the gas sensor 100, and prevents the output-side terminal portion 151 (terminal member 150) from slipping out. The element-side terminal portion 153 has a
{'bibliographic_information': "{'country': 'US', 'doc-number': '10558113', 'kind': 'B2', 'date': '20040531', 'invention_title': 'Gas sensor, gas sensor cap, and gas sensor unit'}", 'source_file': './grant/2007/ipg070529.xml', 'source_data': 'USPTO-Grant'}