A muffler for pulsating gases, especially exhaust gases of internal combustion engines, comprises a housing into which an inlet conduit enters, from which at least on outlet conduit exits and which is divided by at least one partition wall into at least two chambers. In this muffler the flow cross section of a flow path connecting two chambers and/or of an outlet conduit can be varied by means of an adjustable closure element. An actuating element acting on the closure element is provided in the region of the exit cross section of the inlet conduit.

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1. Field of the Invention
The invention relates to a muffler and more particularly to mufflers for pulsating gases, especially exhaust gases of internal combustion engines with variable sound absorbing characteristics!
2. Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98.
The invention relates to a muffler according to the preamble of claim 1. It therefore relates to mufflers for pulsating gases, especially exhaust gases of internal combustion engines, with variable sound-absorbing characteristic.
Legal noise reduction requirements are being introduced increasingly in all walks of life. This is particularly true for motor vehicles powered by internal combustion engines. The considerable improvement of sound absorption required for this application, even in the low speed range, is leading to longer flow paths inside the muffler system and thus to greater flow resistances. The greater energy expenditure must be supplied by the engine. To counter these drawbacks, the flow cross sections available to the pulsating gas must be increased, but the costs for the exhaust-gas system are greater for larger muffler volume. These circumstances are inconsistent with the challenge to the automobile manufacturers, which is to lower costs and decrease the size of the installation space.
One approach to resolving this conflict of objectives was proposed in the paper entitled xe2x80x9cActive sound absorptionxe2x80x94Possibilities for variable modulation of discharge noisexe2x80x9d [in German] (MTZ Motortechnische Zeitschrift 53 (1992) No. 7/8 p. 3). It relates to a rear muffler with two tailpipes. A closure element in the form of a throttle valve is disposed in one of the two tailpipes. This valve is closed when the engine is running at low speed. The exhaust gas flows along a longer flow path. Part of the muffler volume acts as a Helmholtz chamber. When the closure element is open, the exhaust gas flows through both tailpipes. The ratio of the pressure losses, frequently also known as backpressures, with the closure element closed and open corresponds approximately to the square of the reciprocal of the ratio of the free flow areas. The closure element is connected via a crank mechanism and a rod to a pressure cell as the actuating element. This negative-pressure cell is actuated via a control system comprising solenoid valve, vacuum accumulator, nonreturn valve and connecting lines by the intake section of an internal combustion engine, where negative pressure prevails. A control unit which evaluates the engine speed and the throttle-valve position acts on the solenoid valve.
Numerous further proposed solutions for mufflers with variable sound-absorbing characteristic have been formulated. They can be divided into two main groups, which are referred to as externally controlled and autonomous solutions depending on whether the signal for controlling the closure element originates from outside or from inside the muffler.
The example described in the introduction and those of DE-OS 4416739 and DE-OS 3835079 correspond to externally controlled solutions. Such solutions are also found as shutoff valves in other portions of an exhaust-gas system (see, for example, DE 19630164 A1 or DE 9413493 U1). These solutions have the advantage that switching processes can be initiated highly selectively and operate relatively independently of the flow processes in the muffler. A disadvantage of externally controlled solutions is that the switching element can be disposed for the most part only on one tailpipe, outside the muffler. In view of its heat resistance, the pneumatically operated actuating element has only a limited service range. A further critical disadvantage is found in the large number of necessary components: 1. The control system comprises solenoid valve, vacuum accumulator, nonreturn valve and connecting lines. 2. The actuating element is assembled from a diaphragm, housing and spring. 3. A gear mechanism converts the reciprocating motion into pivoting motion. 4. The closure element comprises a shaft, bearing arrangement and gasket ring. In addition, a secondary energy source such as a pneumatic system is needed.
To overcome these disadvantages, autonomous solutions have been proposed. These use selected flow parameters inside a muffler in order to initiate the switching process.
Directly controlled systems rely on the concept, known from reciprocating pump and compressor design, of directly activating valves by fluid flow. Thus they directly utilize the gas stream to be influenced for actuation of the closure element; the actuating element and closure element are combined. Pertinent prior art can be found in particular in DE 19729666 A1, WO 95/13460, DE 19520157 A1, DE 19720410 A1, DE 19540716 C1, DE 19503322 A1, U.S. Pat. Nos. 5,821,474, 5,801,343, 5,739,483, 5,723,827, 5,709,241, 5,708,237, 5,614,699, 4,971,166, 4,484,569, EP 0902171 A1, DE 9207838.9 U1, DE 9405771.0 U1, DE 9406200.5 U1, DE 29803183 U1. Usually spring elements (WO 95/13460) or/and magnets (DE 19520157 A1) are used to generate the restoring forces. The proposed solutions have a critical disadvantage: in general they do not permit stable operating behavior.
When the closure element in one of the parallel flow paths is closed, a relatively large pressure drop develops, depending on the resistance of the free flow path. If the force from the pressure difference is larger than the force of the spring holding the closure element closed, the closure element opens the second flow path. The differential pressure decreases immediately the further the second flow path is released. The opening force vanishes. The spring opposing the force of pressure causes the previously released flow path to close. The useful life of the system is adversely influenced by these unstable switching conditions.
Even systems with all components involved favorably matched, such that the closure elements can occupy intermediate positions depending on flow condition, are not free of disadvantages. In contrast to the externally controlled systems, they must satisfy the prerequisite of a well defined pressure drop in order that a switching process can be initiated. This also explains their poorer acoustic effect, however, compared with externally controlled systems. Bistable switching positions are difficult to adjust. The variability of the acoustic system is limited. In addition, some of the proposed solutions are technically complex.
A more advantageous solution appears to be one proposed in DE 19619173 C1. The incoming flow to the muffler takes place via a venturi nozzle. A negative pressure is generated in the narrowest cross section and, via connecting lines, acts on one side of a pneumatic switching element. The pressure in the inlet conduit upstream from the venturi nozzle acts on the other side. The pressure difference causes opening of the closure element.
Since on the one hand the total mass flow of the incoming flow is used to establish the negative pressure in the venturi nozzle and on the other hand the positive pressure in the inlet conduit upstream from the venturi nozzle is used to open the closure element, although the closure element releases precisely this positive pressure region as the flow path, this solution can be classified among the semi-directly acting systems. This classification will become clearer upon closer examination of the mechanism of action. Upon release of the second flow path upstream from the venturi nozzle, the total pressure difference vanishes, as is necessary to accelerate the exhaust gas to a velocity sufficient to generate negative pressure in the venturi nozzle.
Even in this solution the instability explained hereinabove is not eliminated. Furthermore, extremely high velocities must be achieved in the venturi nozzle in order to establish the necessary negative pressure. As is known, high velocities lead to undesired hydrodynamic noise.
U.S. Pat. Nos. 5,744,762, 5,723,829 and EP 0733785 A2 describe proposed solutions with indirect control. The static (U.S. Pat. No. 5,723,829) or dynamic plus static (U.S. Pat. No. 5,744,762 and EP 0733785) positive pressure in the muffler acts via a tubular line on an externally disposed piston, which actuates a throttle valve via a crank mechanism. With increasing positive pressure the piston is displaced in longitudinal direction, and the throttle valve opens a second flow path. This solution also is highly complex, and does not allow for the fact that, with release of the second flow path, the internal pressure in the muffler also decreases and thus acts against the intended process of opening of the throttle valve.
The technical solutions which guarantee good acoustic functionality are extremely complex. They need an extensive control system, actuating elements which are alternately loaded pneumatically and by spring action, and a gear mechanism for motion transmission. When functional elements are combined, either they become very complex or they lead to flow conditions which are unstable or/and act in opposing manner. Furthermore, the geometric options of the muffler are limited.
A need therefore exists for a muffler with variable sound-absorbing characteristic which resolves the conflict of objectives described in the introduction, which corresponds in its acoustic effect to externally controlled systems and which nevertheless has a more cost-effective and weight-saving design comprising few components.
The object of the invention is to provide a muffler of the class in question with variable sound-absorbing characteristics, the switching elements of which operate without external control and without secondary energy sources, exhibit only slight structural complexity and cause only small pressure losses, wherein the arrangement of components does not cause opposing effects but permits bistable operating conditions and simultaneously a large diversity of alternative configurations based on the boundary conditions of acoustics, geometry and hydrodynamics, which muffler can be equipped with one or two tailpipes if necessary depending on the customer""s wish.
According to the invention, the object is achieved by a muffler, for pulsating gases, especially exhaust gases of internal combustion engines. The muffler comprises a housing into which an inlet conduit enters and at least one outlet conduit exits and is divided by at least one partition wall and at least two chambers. The flow cross section of a flow path connecting chambers and/or of an outlet conduit is variable by an adjustable closure element. An actuating element acts on the closure element and is downstream from the exit cross section of the inlet conduit. The actuating element comprises a movable plate-type element upon which the pulsating gas is incident.
According to the invention, the object is achieved by a muffler with the features of claim 1.
A closure element for varying the sound-absorbing characteristic is also used in the present invention. The closure element is associated with one of two parallel flow paths. When the closure element is open, both flow paths are released, but when it is closed, the exhaust gas flows only via one flow path.
This closure element is associated either with a second tailpipe or with an internal flow conduit of the muffler, especially an inner pipe or an opening of a partition wall. The closure element is moved by an actuating element.
According to the invention, the actuating element is disposed in the region of the exit cross section of the inlet conduit. In an especially preferred embodiment it is disposed at a distance downstream from the exit opening of the inlet conduit. The closure element and actuating element are connected pivotally to one another via a gear mechanism, preferably via a common shaft. According to a preferred improvement of the invention, the actuating element can then have the form of a plate-type element, which in particular can be plane, convex or angled.
The principle of operation of the invention is as follows:
The exhaust-gas stream flows without being split through the inlet conduit. It is only in this arrangement that the exhaust-gas stream can be correlated with the engine speed. The pressure level in the muffler then plays a subordinate role. A restoring device holds the actuating element in a first rest position at low engine speed and thus low exhaust-gas mass flow. In this rest position the closure element closes the second flow path in the muffler or closes the second tailpipe. In this position the muffler has better sound-absorbing properties than when the closure element is open. The exhaust gas flows without hindrance around the actuating element, without actuating or even substantially influencing it.
As the engine speed becomes greater, the exhaust-gas mass flow increases commensurately. The velocity-dependent forces (impulse force, drag force and buoyant force) also increase.
Tests have shown that there exists a medium engine-speed range which from the viewpoint of switching technology can be regarded as the transition region. In this transition region it is immaterial whether the closure element is open or closed. This transition region extends over a speed range of about 300 to 500 rpm and begins at an engine speed of about 2500 rpm in the case of the test arrangement used. Above this region the muffler has better sound-absorbing properties with the closure element open.
The initial tension of a restoring device, preferably in the form of a spring element, is preferably chosen such that the actuating element occupies its first rest position under the transition region. The spring constant is expediently adjusted such that the actuating element occupies its second rest position above the transition region and the closure element releases the second flow path.
Depending on the actual configuration of the mufflerxe2x80x94which is guided not only by the engine-specific characteristics but also by the geometric free space in the bottom region of a motor vehicle as well as by the customer""s wishesxe2x80x94free choice of the hydrodynamic forces acting on the actuating element is also advantageously possible. If impulse force is chosen, the actuating element can be constructed as a plane plate-type element. If it is wished to intensify the impulse force, the plate-type element can be provided with a deflector plate. The deflector plate can be fastened directly on the actuating element such that it is disposed at a specified distance therefrom. In one advantageous construction a cylindrical deflector plate is used. This surrounds the actuating element. The flow follows the movement of the actuating element.
A further preferred arrangement provides an actuating element with aerodynamic surface profile. In the first rest position the drag force acts on the actuating element, and in its second rest position the buoyant force acts thereon. The buoyant force can be intensified by disposing at a distance from the second rest position, parallel to the plate-type element having airfoil-like convexity or a curved surface of the actuating element, a deflector plate such that the gas flowing between actuating element and deflector plate generates a negative pressure and holds the actuating element stably in the second position. It is also possible to shape the actuating element as the blade of a turbine, preferably of a Pelton turbine. In this way the impulse force can be efficiently utilized.
A further preferred construction of the actuating element provides for equipping it with openings. The exhaust gas moves partly through and around the actuating element, creating a drag force. With increasing incident velocity the drag force increases, until the actuating element leaves the first rest position and moves to the second end position.
Pressure oscillations superposed on the main flow pass without being influenced through the openings in the actuating element and/or the free surface between it and the exit cross section of the inlet conduit.
The advantages of the inventive solution are that fluctuations not caused primarily by the typical principle of operation of an internal combustion engine (pulsations) are eliminated.
The gear mechanism which transmits the movement of the actuating element to the closure element is advantageously constructed as a simple shaft. Nevertheless, different forms of movement transmission can be designed depending on application. For example, it may be advantageous to mount the actuating element and closure element separately and to bring about movement in opposite directions via a toothed gear or lever-type linkage.
The ensemble of actuating element, gear mechanism, preferably a common shaft, closure element and restoring device has very simple structure, few moving parts and low weight, and permits an extremely variable configuration of the muffler.

Muffler with variable sound-absorbing characteristics


A device and method for recovery from address errors is described. When an address error is detected on a local channel, such as a local bus, the coherency states of one or more lines of cache memory associated with the local channel are read, and actions are taken in response. Reading of coherency states ranges from a complete and active interrogation of all cache lines, to a selective and passive interrogation, such as in responding to snoop requests. If the data state consistency is unknown, such as when the MESI state is Modified (M) or Exclusive (E), then the corresponding data in main memory is poisoned. Poisoning may be accomplished by writing a detectable but unrecoverable error pattern in the main memory. Alternatively, the same effect may be accomplished by signaling a hard error on the system bus. If the data state consistency of an interrogated cache line is Shared (S) or Invalid (I), the line may be ignored or the line marked invalid. If the state of the cached line is valid and consistent, such as the xe2x80x9cModified uncachedxe2x80x9d (Mu) state in a MuMESI protocol, then the line may be written to main memory or provided to a snoop requester.

The invention relates to computers and processor systems. More particularly, the invention relates to recovery from address channel errors in a multiprocessor computing system having cache memory.
In a computer system, the interface between a processor and memory is critically important to the performance of the system. Because fast memory is very expensive, memory in the amount needed to support a processor is generally much slower than the processor. In order to bridge the gap between fast processor cycle times and slow memory access times, cache memory was developed. A cache is a small amount of very fast, zero wait state memory that is used to store a copy of frequently accessed data and instructions from main memory. The microprocessor can operate out of this very fast memory and thereby reduce the number of wait states that must be interposed during memory accesses. When the processor requests data from memory and the data resides in the cache, then a cache read xe2x80x9chitxe2x80x9d takes place, and the data from the memory access can be returned to the processor from the cache without incurring wait states. If the data is not in the cache, then a cache read xe2x80x9cmissxe2x80x9d takes place, and the memory request is forwarded to the system and the data is retrieved from main memory, as would normally be done if the cache did not exist. On a cache miss, the data that is retrieved from the main memory is provided to the processor and is also written into the cache due to the statistical likelihood that this data will be requested again by the processor.
The individual data elements stored in a cache memory are referred to as xe2x80x9clines.xe2x80x9d Each line of a cache is meant to correspond to one addressable unit of data in the main memory. A cache line thus comprises data and is associated with a main memory address in some way. Schemes for associating a main memory address with a line of cache data include direct mapping, full association and set association, all of which are well known in the art.
The presence of caches should be transparent to the overall system, and various protocols are implemented to achieve such transparency, including write-through and write-back protocols. In a write-through action, data to be stored is written to a cache line and to the main memory at the same time. In a write-back action, data to be stored is written to the cache and only written to the main memory later when the line in the cache needs to be displaced for a more recent line of data or when another processor requires the cached line. Because lines may be written to a cache exclusively in a write-back protocol, precautions must be taken to manage the status of data in a write-back cache, as described in greater detail below.
Cache management is generally performed by a device referred to as a cache controller. A principal cache management objective is the preservation of cache coherency. In computer systems where independent bus masters can access memory, there is a possibility that a bus master, such as another processor, network interface, disk interface, or video graphics card might alter the contents of a main memory location that is duplicated in the cache. When this occurs, the cache is said to hold stale or invalid data. In order to maintain cache coherency, it is necessary for the cache controller to monitor the system bus when the processor does not own the system bus to see if another bus master accesses main memory. This method of monitoring the bus is referred to as xe2x80x9csnooping.xe2x80x9d
The cache controller must monitor the system bus during memory reads by a bus master in a write-back cache design because of the possibility that a previous processor write may have altered a copy of data in the cache that has not been updated in main memory. This is referred to as read snooping. On a xe2x80x9cread snoop hit,xe2x80x9d where the cache contains data not yet updated in main memory, the cache controller generally provides the respective data to main memory, and the requesting bus master generally reads this data en route from the cache controller to main memory, this operation being referred to as xe2x80x9csnarfing.xe2x80x9d The cache controller must also monitor the system bus during memory writes because another bus master may write to or alter a memory location that resides in the cache. This is referred to as write snooping. On a xe2x80x9cwrite snoop hit,xe2x80x9d the cache entry is either marked invalid in the cache directory by the cache controller, signifying that this entry is no longer correct, or the cache is updated along with main memory. Therefore, when another bus master reads or writes to main memory in a write-back cache design, or writes to main memory in a write-through cache design, the cache controller must latch the system address and perform a cache look-up to see if the main memory location being accessed also resides in the cache. If a copy of the data from this location does reside in the cache, then the cache controller takes the appropriate action depending on whether a read or write snoop hit has occurred. This prevents incoherent data from being stored in main memory and the cache, thereby preserving cache coherency.
Another consideration in the preservation of cache coherency is the handling of processor writes to memory. When the processor writes to main memory, the memory location must be checked to determine if a copy of the data from this location also resides in the cache. If a processor write hit occurs in a write-back cache design, then the cache location is updated with the new data and main memory may be updated with the new data at a later time or should the need arise. In a write-through cache, the main memory location is generally updated in conjunction with the cache location on a processor write hit. If a processor write miss occurs, the cache controller may ignore the write miss in a write-through cache design because the cache is unaffected in this design. Alternatively, the cache controller may perform a xe2x80x9cwrite-allocatexe2x80x9d whereby the cache controller allocates a new line in a cache in addition to passing the data to the main memory. In a write-back cache design, the cache controller generally allocates a new line in the cache when a processor write miss occurs. This generally involves reading the remaining entries to fill the line from main memory before or jointly with providing the write data to the cache. Main memory is updated at a later time should the need arise.
Caches may be designed independently of the microprocessor, in which case the cache is placed on the local bus of the microprocessor and interfaced between the processor and the system bus during the design of the computer system. However, as the density of transistors on a process chip has increased, processors may be designed with one or more internal caches in order to decrease further memory access times. The internal cache used in these processors is generally small, an exemplary size being 8 k (8192 bytes) in size. In computer systems that utilize processors with one or more internal caches, an external cache is often added to the system to further improve memory access time. The external cache is generally much larger than the internal cache(s), and, when used in conjunction with the internal cache(s), provides a greater overall hit rate than the internal cache(s) would provide alone.
In systems that incorporate multiple levels of caches, when the processor requests data from memory, the internal or first level cache is first checked to see if a copy of the data resides there. If so, then a first level cache hit occurs, and the first level cache provides the appropriate data to the processor. If a first level cache miss occurs, then the second level cache is then checked. If a second level cache hit occurs, then the data is provided from the second level cache to the processor. If a second level cache miss occurs, then the data is retrieved from main memory. This process continues through higher levels of caches, if present. Write operations are similar, with mixing and matching of the operations discussed above being possible.
In many instances where multilevel cache hierarchies exist with multiple processors, a property referred to as multilevel inclusion is desired in the hierarchy. Multilevel inclusion provides that a second level (e.g., external) cache is guaranteed to have a copy of what is inside a first level (e.g., internal) cache. In this case, the second level cache holds a superset of the first level cache. Multilevel inclusion obviates the need for all levels of caches to snoop the system bus and thus enables the caches to perform more efficiently. Multilevel inclusion is most popular in multiprocessor systems, where the higher level caches can shield the lower level caches from cache coherency problems and thereby prevent unnecessary snoops that would otherwise occur in the lower level caches if multilevel inclusion were not implemented.
In a multiprocessor system where each processor utilizes a multilevel cache system with inclusion, there may be, for example, a Level 1 (L1) write-through cache associated with each processor and a larger, slower Level 2 (L2) write-back cache, which is still much faster than the main memory. The L2 and L1 caches utilize the MESI (pronounced xe2x80x9cmessyxe2x80x9d) protocol for managing the state of each cache line as follows: For each cache line, there is an M, E, S, or I state that indicates the current state of the cache line in the system. According to this well-known protocol, the Exclusive (E) bit indicates that the line only exists in this cache, the Shared (S) bit indicates that the line can be shared by multiple users at one time, the Invalid (I) bit indicates that the line is not available in the cache, and the Modified (M) bit indicates that the line has been changed or modified since it was first written to the cache. This management system improves system performance because unmodified lines need not be written back to the system""s main memory.
The L1 cache does not require the Exclusive (E) bit in systems where it is the L2 cache""s responsibility to manage line MESI state changes. Thus, the L1 cache may be said to implement the MSI protocol. In these systems, a line marked Exclusive (E) in L2, would be marked Shared (S) in L1. If another processor wants to share a copy of this line, the L2 cache would indicate via its snoop response that the line is Shared (S) and change the state of the L2 copy of the line to Shared (S). Because the L1 line state did not need to be changed, the L1 cache did not need to be involved in the line state change, thus improving performance.
In a multiprocessor environment, snoop latency may be fixed, which means that when a processor makes a storage request on the system bus, all other processors, or bus devices, must respond within a fixed period of time. In the event the storage request is a line read, other processors or devices which have a copy of the line are allowed to respond only with Shared (S) or Modified (M). A processor is not allowed to keep exclusive ownership of the line in this case. If the snoop response is Modified (M), the processor owning the current state of the line must provide the current copy to the requester, and change the state of its copy of the line to Shared (S) or Invalid (I), depending on the snoopy bus protocol. In systems where the L1 cache cannot be snooped, or the L1 cache snoop response cannot meet the fixed response time requirement of the snoopy bus, the L2 cache must mark a line as Modified (M) prior to any processor store to that line.
An alternative to snoopy protocols are directory based cache coherency protocols. In a directory based coherency scheme, the system typically contains a single directory having one entry for every address in main memory. Each directory entry identifies the ownership and data state information of each line of main memory. That is, the directory contents are tags. The data states tracked in a directory coherency system may be similar to the data states tracked in a snoopy system (e.g., MESI-based states or something similar).
An objective of the present invention is to exploit cache coherency information in a multiprocessor computing system in reaction to an address error.
One of the most serious types of errors in a computer system is an address error on a computer bus. On a typical computer bus, which contains a separate address bus (as well as a data bus and control lines), as address buses are designed in greater widths, the specter of address errors becomes more threatening. An address error is serious because a bus agent that reports the error must be assumed to have no idea what the true memory address target was. The result might be a memory controller providing the wrong data, or worse yet, writing the right data to the wrong memory location. When an address error occurs in a multiprocessor system, one or more processors may have inconsistent views of memory. In order to avoid the continued processing of corrupted data, most computers respond to an address error by generating a fatal error, which in turn causes an immediate failure of the operating system. This is disadvantageous because it does not permit graceful shutdown of applications.
Non-graceful shutdowns cause significant increases in recovery time for applications such as databases. In particular, non-graceful shutdowns may occur before the system has an opportunity to flush open buffers and close open files. As a result, storage files that reside on I/O (input/output) devices may be corrupt and inconsistent. Returning a computer file system to a known good state may require a great deal of time and effort. Typically, archival backups and/or update logs of the storage system are needed. Further, some data that has been entered since the last backup needs to be recreated, if that is even possible.
An advantage of the present invention is a higher likelihood of either avoiding the need for bringing the system down as a result of an address error or providing a window of opportunity in which to conduct a more orderly shutdown of critical operations, in response to an address error.
This invention is based upon the recognition that the property of inclusion, offered by an inclusive cache, coherency directory or other coherency filter provides unique opportunities for error recovery. In traditional bus-based MESI coherency systems, only the owner of a cache line knows that he owns it. Thus, if the owner dies or his connection to the system fails, the correct state of memory is totally unknown. The data structures used by inclusive systems to track inclusion (address tags for caches, and directory entries for directories) contain redundant information about the ownership of lines and, in some cases, up-to-date copies of modified data. The present invention is sometimes capable of providing enough data about the state of memory to allow applications to recover from address errors, such as parity errors. The information provided may be sufficient to allow a complete recovery, but more often, the information provided will allow the system to avoid corrupt data and run long enough to permit graceful shutdown of mission critical applications.
According to a method of the present invention, an address error is detected on a local channel, such as a local bus. The coherency states of one or more lines of cache memory associated with the local channel are then read, and actions are taken in response. Reading of coherency states ranges from a complete and active interrogation of all cache lines, to a selective and passive interrogation, such as in responding to snoop requests. If the data state consistency is unknown, such as when the MESI state is Modified (M) or Exclusive (E), then the corresponding data in main memory is poisoned. Poisoning may be accomplished by writing a detectable but unrecoverable error pattern in the main memory. Alternatively, the same effect may be accomplished by signaling a hard error on the system bus. If the data state consistency of an interrogated cache line is Shared (S) or Invalid (I), the line may be ignored or the line marked invalid. If the state of the cached line is valid and consistent, such as the xe2x80x9cModified uncachedxe2x80x9d (Mu) state in a MuMESI protocol, then the line may be written to main memory or provided to a snoop requester.

System and method for recovery from address errors


A disposable absorbent article that includes a frangible bonding agent for maintaining the absorbent article in a predetermined configuration. The frangible bonding agent may be disposed on a fastening system in order to maintain one or more portions of the fastening system in a particular position during manufacturing but still provide an easy-to-open fastener when used by a consumer.

Wearable absorbent articles (e.g., taped diapers, pull-on diapers, training pants, sanitary napkins, panty liners, incontinence briefs, and bandages) typically offer the benefit of receiving and containing the bodily exudates of a wearer. Disposable varieties of such absorbent articles are commonly known, and are typically mass produced on a high speed production line. Some disposable absorbent articles include a mechanical fastening system (e.g., hook/loop or tab/slot) for maintaining the article in a desired position or configuration prior to, during, and/or after use of the article. Such fastening systems may include one or more elements that extend laterally outwardly beyond the side edges of the article, such as commonly known fastening tabs. These laterally outwardly extending portions of the fastening system may increase the risk of contamination or damage to the article, an article element, and/or the manufacturing equipment during a high speed manufacturing process. Repositioning the outwardly extending portions of the fastening system (e.g., by folding the portion laterally inward) may reduce the likelihood of damage or contamination, but the folded fastening system element may not remain suitably folded for a desired amount of time (e.g., the duration of the manufacturing process) due to the high speed nature of the manufacturing process.
A fastening system that includes a mechanical fastener having commonly known hooks or other similar features may be maintained in a folded configuration by engaging the mechanical fastener with a complementary element of the fastening system, such as loops or a nonwoven portion. Such mechanical fastening systems are generally engaged by entangling the hooks or other similar feature with the complementary element. However, an engaged mechanical fastening system still may not provide sufficient bonding strength to maintain the fastening system in the desired folded configuration during a high speed manufacturing process. Therefore, in order to increase the bond strength of the mechanical fastener, a bonding agent such as an adhesive may be applied to one or more portions of the mechanical fastener prior to folding and/or engaging the fastening system. Conventional adhesives such as commonly known pressure sensitive adhesives generally form permanent bonds. The bond strength provided by at least some permanent bonding agents such as commonly known hot-melt adhesives typically remain substantially constant or may even increase between the time the absorbent article is made and the time it is purchased and/or used by a consumer. For example, during shipping and/or storage of disposable absorbent articles, the articles may be subjected to a wide variety of temperature and/or humidity conditions. Periods of increased temperature (e.g., 50° C. or more) may cause conventional hot-melt adhesives to exhibit an undesirable increase in bond strength when the article is to be used by a consumer. It is believed, without being limited by theory, that at higher temperatures the flowability of the hot-melt adhesive increases enough for it to penetrate further into the pores or capillaries of the substrate. Then, when the adhesive cools, it requires more force to separate the joined surfaces.
While permanent bonds may provide the desired bond strength during a high speed manufacturing process, the increased bond strength and/or infrangibility of the adhesive may be undesirable at other times such as when a consumer attempts to use the article or fastening system and it becomes necessary to break the bond. In order for a disposable absorbent article to be used as intended by a consumer, it may be necessary or desirable to unfold or reposition the fastening system or other portion of the article. The increased bond strength and/or infrangible bond provided by a permanent bonding agent may result in an undesirably difficult unfolding or repositioning experience. In addition, mechanical fastening systems are typically configured to be refastenable (i.e., the fastener can be fastened and unfastened more than once without substantial loss of fastening capability). Applying a permanent bonding agent to the mechanical fastener may undesirably reduce the refastenability of the mechanical fastener, for example, by covering up the engageable portions of the mechanical fastener.
One way to address the high bond strength problems described above may be to use a temporary bonding agent such as a temporary strength adhesive to maintain the fastening system in a folded configuration. Temporary strength adhesives, sometimes referred to as "fugitive" adhesives, are known (see, e.g., U.S. Publication No. 2006/0027320, filed by Kueppers, et al., on Jun. 20, 2005). However, fugitive adhesives are typically used to create temporary, frangible paper-to-paper bonds, for example, for joining cardboard containers and/or portions thereof to one another or for use with envelopes, labels, and the like. Typically, when the bond provided by a fugitive adhesive is broken, the adhesive is no longer tacky and does not readily adhere to anything. Fugitive adhesives are not known in the art for use in the fastening system of an absorbent article such as a disposable diaper. One reason for this may be the difference in materials used in absorbent articles (which typically include at least some polymeric materials as opposed to only paper). Another reason may be that the fastening system for an absorbent article is generally intended to provide a permanent bond or, in the case of a refastenable fastening system, a quasi-permanent bond to maintain the article in the desired position and/or configuration on a wearer. In other words, one goal of the fastening system is to provide sufficient bond strength to prevent the article from undesirably coming unfastened during the intended use of the article, and a temporary bonding agent will typically not help achieve this goal.
In addition, known fugitive adhesives may not form a strong enough initial bond to make them capable of temporarily holding folded portions of absorbent articles in place during a high speed manufacturing process where the folded portions of the absorbent articles could come in to contact with other objects in the manufacturing process. Water-based fugitive adhesives, which are typically used in labeling and envelope applications, have relatively low bond strengths when wet (i.e., when applied). This may be sufficient for use in bonding paper to paper, but it is generally not sufficient for the absorbent article applications described herein. Further, in order for conventional fugitive adhesives to lose strength, they may require active heating, radiation, or the like to reduce their strength, all of which are impractical for use with absorbent articles. Other known fugitive adhesives are solvent cross-linked materials, which may not be suitable for use in the absorbent articles described herein.
Accordingly, it would be desirable to provide a disposable absorbent article comprising a frangible bonding agent for maintaining the article in a particular configuration during a high speed manufacturing process. It would also be desirable to provide a fastening system that is relatively easy to open by a consumer. It would further be desirable to provide a fastening system comprising a frangible bonding agent, which does not impair the fastenability or refastenability of a fastening system.

This patent is subject to a terminal disclaimer.

Disposable absorbent article having a frangible bonding agent