Catalyst cooling device for internal combustion engine

Abstract

To provide a catalyst cooling device for an internal combustion engine capable of cooling an exhaust emission control catalyst to a target temperature in a short time when the internal combustion engine is not in operation.SOLUTION: A catalyst cooling device for an internal combustion engine includes: an exhaust emission control catalyst 22 provided in an exhaust pipe 16 of the internal combustion engine 12; a first flow passage 26 that is connected to a portion downstream of the exhaust emission control catalyst in the exhaust pipe and in which exhaust gas discharged from the internal combustion engine flows; a heat exchanger 36 connected to the first flow passage to cool the exhaust gas; and a second flow passage 30 for returning the exhaust gas cooled by the heat exchanger to a portion upstream of the exhaust emission control catalyst in the exhaust pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a catalyst cooling device for an internal combustion engine. [Background technology]

[0002] The following Patent Document 1 discloses an internal combustion engine that uses vaporized LPG as fuel. This internal combustion engine includes an exhaust passage through which exhaust gas generated by combustion flows, an exhaust gas purification catalyst (three-way catalyst) provided in the exhaust passage, a first bypass passage that extracts part of the exhaust gas from a portion of the exhaust passage downstream of the exhaust gas purification catalyst and supplies it to a vaporizer, a condensed water storage section that stores condensed water generated by exhaust gas being supplied to the vaporizer, and a communication passage that supplies the condensed water stored in the condensed water storage section to a gap in a catalyst case that covers the exhaust gas purification catalyst. The catalyst case has an inner cylinder that covers the exhaust gas purification catalyst and an outer cylinder that forms the above-mentioned gap between the inner cylinder and the outer cylinder.

[0003] Condensed water generated during operation of the internal combustion engine is supplied to the gap in the catalyst case, thereby cooling the exhaust gas purification catalyst located on the inner circumferential side of the inner cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-200020 A Summary of the Invention [Problem to be solved by the invention]

[0005] The internal combustion engine of Patent Document 1 generates condensed water only when it is operating. Therefore, when the internal combustion engine is not operating, it cannot cool the exhaust gas purification catalyst. Furthermore, the condensed water of Patent Document 1 indirectly cools the exhaust gas purification catalyst via the inner cylinder, so it is difficult to achieve a large cooling effect.

[0006] SUMMARY OF THE PRESENT INVETION The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a catalyst cooling device for an internal combustion engine capable of cooling an exhaust gas purification catalyst to a target temperature in a short period of time while the internal combustion engine is not operating. [Means for solving the problem]

[0007] The catalyst cooling device for an internal combustion engine according to the invention described in claim 1 comprises an exhaust gas purification catalyst provided in an exhaust pipe of an internal combustion engine, a first flow path connected to a portion of the exhaust pipe downstream of the exhaust gas purification catalyst and through which exhaust gas discharged from the internal combustion engine flows, a heat exchanger connected to the first flow path and cooling the exhaust gas, and a second flow path returning the exhaust gas cooled by the heat exchanger to a portion of the exhaust pipe upstream of the exhaust gas purification catalyst.

[0008] The heat exchanger of the catalyst cooling device for an internal combustion engine according to the invention recited in claim 1 can cool exhaust gas even when the internal combustion engine is not operating. Therefore, exhaust gas cooled by the heat exchanger when the internal combustion engine is not operating is supplied to the exhaust gas purification catalyst via the second flow path and the exhaust pipe. Also, exhaust gas is directly supplied to the exhaust gas purification catalyst via the second flow path and the exhaust pipe. Therefore, the catalyst cooling device for an internal combustion engine according to the invention recited in claim 1 can cool the exhaust gas purification catalyst to a target temperature in a short time while the internal combustion engine is not operating. Effect of the Invention

[0009] The catalyst cooling device for an internal combustion engine according to the present invention is capable of cooling an exhaust gas purification catalyst to a target temperature in a short period of time while the internal combustion engine is not operating. [Brief description of the drawings]

[0010] [Figure 1] 1 is an overall view of an internal combustion engine testing system including a catalyst cooling device for an internal combustion engine according to an embodiment; [Diagram 2] FIG. 2 is a control block diagram of a control device. [Diagram 3] FIG. 2 is a functional block diagram of a control device. [Figure 4]1 is a flowchart showing a process executed by a CPU. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a catalyst cooling device for an internal combustion engine according to the present invention will be described with reference to the drawings.

[0012] An internal combustion engine testing system 10 (hereinafter, system 10) equipped with a catalyst cooling device for an internal combustion engine of this embodiment is a system for acquiring various data related to an internal combustion engine 12 during test operation in which the rotation speed and torque are changed. This data includes, for example, the concentration and mass of a predetermined component of exhaust gas discharged from an exhaust pipe 16 of the internal combustion engine 12. As shown in FIG. 1, the system 10 includes the internal combustion engine 12, an exhaust gas recirculation device 25, an air refrigerant supply device 40, and a control device 45.

[0013] The internal combustion engine 12 includes an internal combustion engine body 14, an exhaust pipe 16, and a catalytic device 18. The internal combustion engine 12 operates by burning gasoline or the like as fuel. The internal combustion engine body 14 includes a cylinder block, a cylinder head, a piston, an intake valve, an exhaust valve, a connecting rod, and a crankshaft connected to the piston via a connecting rod. One end of an exhaust pipe 16 is connected to the internal combustion engine body 14. Exhaust gas generated in the combustion chamber flows from the combustion chamber into the exhaust pipe 16.

[0014] A catalytic device 18 is provided in the middle of the exhaust pipe 16. The catalytic device 18 has a cylindrical catalyst case 20 with a heat insulating function, an exhaust gas purification catalyst 22 (hereinafter referred to as catalyst 22) provided inside the catalyst case 20, and a temperature sensor 23 provided inside the catalyst case 20. The catalyst 22 has a catalyst carrier that functions as a three-way catalyst. The internal space of the catalyst case 20 communicates with the internal space of the exhaust pipe 16 in an airtight state. The temperature sensor 23 detects the temperature of the catalyst 22.

[0015] An exhaust gas circulation device 25 is connected to the exhaust pipe 16 at a portion downstream and upstream of the catalytic device 18. The exhaust gas circulation device 25 includes a first bypass pipe (first flow path) 26, a first valve 28, a second bypass pipe (second flow path) 30, a second valve 32, an electric pump 34, a heat exchanger 36, a refrigerant supply device 38, and a communication pipe 39.

[0016] One end of a first bypass pipe 26 is airtightly connected to a portion of the exhaust pipe 16 downstream of the catalytic converter 18. A first valve 28, which is a normally closed solenoid valve, is provided in the first bypass pipe 26. One end of a second bypass pipe 30 is airtightly connected to a portion of the exhaust pipe 16 upstream of the catalytic converter 18. A second valve 32, which is a normally closed solenoid valve, and an electric pump 34 are provided in the second bypass pipe 30.

[0017] A heat exchanger 36 is provided between the other end of the first bypass pipe 26 and the other end of the second bypass pipe 30. A refrigerant supply device 38 is connected to the heat exchanger 36 via a communicating pipe 39. Inside the refrigerant supply device 38, there are provided a refrigerant storage section that stores refrigerant, a cooler that cools the refrigerant, which is at least one of a liquid and a gas, in the refrigerant storage section, and an electric pump that sends the refrigerant in the refrigerant storage section to an internal flow path (not shown) provided inside the heat exchanger 36 via the communicating pipe 39. When the electric pump is operated, the refrigerant circulates among the refrigerant supply device 38, the communicating pipe 39, and the heat exchanger 36.

[0018] An air refrigerant supply device 40 is provided around the catalytic converter 18. The air refrigerant supply device 40 includes a heat insulating case 41, a communication pipe 42, and a cold air supply device 43. The heat insulating case 41 is a member provided on the outer periphery of the catalytic converter 18. The exhaust pipe 16 passes through two through holes 41b provided in two side plates 41a of the heat insulating case 41. Furthermore, the inner surface of each through hole 41b contacts the outer periphery of the exhaust pipe 16 at the two locations in an airtight state. A heat insulating material is provided on the inner surface of the heat insulating case 41. The heat insulating case 41 is provided with a normally closed release valve 41c that opens only when the pressure inside the heat insulating case 41 becomes equal to or higher than a predetermined value. One end of the communication pipe 42 is airtightly connected to the heat insulating case 41. The other end of the communication pipe 42 is airtightly connected to the cold air supply device 43. A cooler and an electric pump (both not shown) are provided inside the cold air supply device 43. The cold air supply device 43 introduces air around the cold air supply device 43 into the cold air supply device 43, and then sends the air cooled by a cooler to the internal space of the heat-insulating case 41 through a connecting pipe 42 by using an electric pump.

[0019] 3, the control device 45 includes a CPU (Central Processing Unit) 45A, a ROM 45B, a RAM 45C, a storage 45D, a communication I / F 45E, and an input / output I / F 45G. These components are connected to each other so as to be able to communicate with each other via an internal bus 45Z.

[0020] The CPU 45A is a central processing unit, and executes various programs and controls each part. The CPU 45A reads out a program from the ROM 45B or the storage 45D, and executes the program using the RAM 45C as a working area. The CPU 45A controls each component and performs various arithmetic processing according to the program recorded in the ROM 45B or the storage 45D. The ROM 45B stores various programs and various data. The RAM 45C temporarily stores programs or data as a working area. The storage 45D is composed of a storage device such as an HDD or SSD, and stores various programs and various data. The communication I / F 45E is an interface for communicating with a control device other than the control device 45. The input / output I / F 45G is an interface for communicating with various devices. The first valve 28, the second valve 32, the coolers and electric pumps of the electric pumps 34 and 38, and the cooler and electric pump of the cold air supply device 43 are connected to the input / output I / F 45G.

[0021] The control device 45 has, as its functional components, an operation determination unit 451, an exhaust gas circulation control unit 452, and an air refrigerant control unit 453. These are realized by the CPU 45A reading and executing the programs stored in the ROM 45B.

[0022] The operation feasibility determination unit 451 determines whether or not a predetermined operation signal has been input to the control device 45. For example, when the internal combustion engine 12 finishes a test run, the manager of the system 10 can input the operation signal using an input device (not shown) connected to the control device 45. Also, when the test run of the internal combustion engine 12 ends, the operation signal may be automatically input from the input device to the control device 45. When an operation signal is input to the control device 45, the operation feasibility determination unit 451 performs an operation determination.

[0023] Furthermore, the manager compares information about the temperature of the catalyst 22 detected by the temperature sensor 23 with a predetermined temperature threshold. The temperature sensor 23 is connected to the input device, and the detection result of the temperature sensor 23 is displayed on the display of the input device. The temperature threshold is, for example, 600°C. When the temperature of the catalyst 22 is equal to or lower than the temperature threshold, the manager inputs a stop signal using the input device. As a result, a stop signal is transmitted from the input device to the control device 45, and the operation feasibility determination unit 451 performs a stop determination.

[0024] When the above-mentioned operation signal is input to the control device 45, the exhaust gas circulation control unit 452 transmits a valve open signal to the first valve 28 and the second bypass pipe 30, and transmits an operation signal to the electric pump 34. Furthermore, when the operation feasibility determination unit 451 makes a stop determination, the exhaust gas circulation control unit 452 stops transmitting the valve open signal to the first valve 28 and the second bypass pipe 30, and stops transmitting the operation signal to the electric pump 34.

[0025] When an operation signal is input to the control device 45, the air refrigerant control unit 453 transmits an operation signal to the cooler and the electric pump of the cold air supplying device 43. In addition, when the operation possibility determination unit 451 makes a stop determination, the air refrigerant control unit 453 stops transmitting the operation signal to the cooler and the electric pump of the cold air supplying device 43.

[0026] Among the components described above, the catalyst device 18, the exhaust gas circulation device 25, the air coolant supply device 40, and the control device 45 are components of a catalyst cooling device 50 for an internal combustion engine.

[0027] Next, the process executed by the CPU 45A will be described. The CPU 45A repeatedly executes the process of the flowchart shown in Fig. 4 every time a predetermined time has elapsed. It is assumed that the internal combustion engine 12 is performing a test operation. It is also assumed that the electric pump of the refrigerant supply device 38 is operating, and the refrigerant is circulating between the refrigerant supply device 38, the communication pipe 39, and the heat exchanger 36.

[0028] In step S10 (hereinafter, the word "step" will be omitted), the CPU 45A determines whether or not the above-mentioned operation determination has been performed. That is, the CPU 45A determines whether or not the internal combustion engine 12 has finished the test operation. When the determination in S10 is Yes, the CPU 45A proceeds to S11.

[0029] In S11, the CPU 45A sends a valve opening signal to the first valve 28 and the second bypass pipe 30 of the exhaust gas circulation device 25, and also sends an operation signal to the electric pump 34. As a result, the exhaust gas (inert gas) discharged from the internal combustion engine body 14 to the exhaust pipe 16 and purified by passing through the catalyst 22 is returned to a portion of the exhaust pipe 16 upstream of the catalytic device 18 via the first bypass pipe 26, the heat exchanger 36, and the second bypass pipe 30. This exhaust gas is cooled when passing through the heat exchanger 36. Therefore, the cooled exhaust gas is supplied to the catalyst 22 from a portion of the exhaust pipe 16 upstream of the catalytic device 18.

[0030] After completing the process of S11, the CPU 45A proceeds to S12 and sends an operation signal to the cooler and the electric pump of the cold air supply device 43. As a result, air cooled by the cooler is supplied by the electric pump from the cold air supply device 43 to the inside of the heat-insulating case 41. When the pressure inside the heat-insulating case 41 reaches or exceeds a predetermined value, the release valve 41c opens.

[0031] After completing the process of S12, the CPU 45A proceeds to S13 and determines whether or not a stop determination has been made. That is, the CPU 45A determines whether or not the temperature of the catalyst 22 has become equal to or lower than the temperature threshold value. In other words, the CPU 45A determines whether or not the temperature of the catalyst 22 has become low enough to allow the catalyst 22 to perform a sufficient purification function.

[0032] If the determination in S13 is Yes, the CPU 45A proceeds to S14. On the other hand, if the determination in S13 is No, the CPU 45A returns to S11.

[0033] In S14, the CPU 45A stops sending a valve open signal to the first valve 28 and the second bypass pipe 30 of the exhaust gas circulation device 25, and stops sending an operation signal to the electric pump 34. This stops the supply of exhaust gas (inert gas) purified by the catalyst 22 to the exhaust pipe 16 via the heat exchanger 36.

[0034] After completing the process of S14, the CPU 45A proceeds to S15 and stops sending operation signals to the cooler and the electric pump of the cold air supply device 43. This stops the supply of cooled air from the cold air supply device 43 to the heat-insulating case 41.

[0035] When the result of the determination in S10 is No or when the process of S15 is completed, the CPU 45A temporarily ends the process of the flowchart in FIG.

[0036] As described above, the heat exchanger 36 of the exhaust gas circulation system 25 is capable of cooling the exhaust gas (inert gas) supplied via the first bypass pipe 26 when the internal combustion engine 12 is not performing a test operation. Therefore, the exhaust gas cooled by the heat exchanger 36 when the internal combustion engine 12 is not performing a test operation is directly supplied to the catalyst 22 via the second bypass pipe 30 and the exhaust pipe 16.

[0037] Furthermore, cooled air is supplied from the cold air supply device 43 of the air refrigerant supply device 40 into the heat-insulating case 41. A heat insulating material is provided on the inner surface of the heat-insulating case 41, and the inner surfaces of the through holes 41b of each side plate 41a are in airtight contact with the outer circumferential surface of the exhaust pipe 16 at two locations. Therefore, the catalyst case 20 is effectively cooled by the cooled air, and the catalyst 22 is effectively cooled by the cooled catalyst case 20.

[0038] Therefore, the catalyst cooling device 50 for an internal combustion engine can cool the catalyst 22 to a target temperature (temperature threshold) or lower in a short time while the internal combustion engine 12 is not performing a test operation. Therefore, the test operation of the internal combustion engine 12 can be resumed a short time after the internal combustion engine 12 has once ended the test operation.

[0039] Furthermore, since the inert gas is supplied to the catalyst 22, there is little risk that the state of the catalyst 22 will change.

[0040] Although the catalyst cooling device for an internal combustion engine according to the embodiment has been described above, the design thereof can be appropriately modified without departing from the gist of the present invention.

[0041] For example, an inert gas cylinder capable of generating an inert gas may be connected to the first bypass pipe 26. Also, a high-purity inert gas generator for inactivating exhaust gas may be connected to a branch pipe (not shown) branched off from the first bypass pipe 26, and the inert gas purified by this high-purity inert gas generator may be returned to the first bypass pipe 26 via the branch pipe. According to this modification, high-purity inert gas can be supplied to the catalyst 22 via the exhaust pipe 16. [Explanation of symbols]

[0042] 12 Internal combustion engine 16 Exhaust pipe 22 Exhaust gas purification catalyst 26 First bypass pipe (first flow path) 30 Second bypass pipe (second flow path) 36 Heat exchanger 50 Catalyst cooling device for internal combustion engine

Claims

[Claim 1] an exhaust gas purification catalyst provided in an exhaust pipe of an internal combustion engine; a first flow passage connected to a portion of the exhaust pipe downstream of the exhaust gas purification catalyst, through which exhaust gas discharged from the internal combustion engine flows; a heat exchanger connected to the first flow path and configured to cool the exhaust gas; a second flow passage that returns the exhaust gas cooled by the heat exchanger to a portion of the exhaust pipe upstream of the exhaust gas purification catalyst; A catalyst cooling device for an internal combustion engine comprising:

Images