Catalyst warm-up system

Abstract

To improve the combustion stability of the warmup of a catalyst, and to reduce vibration and noise.SOLUTION: A catalyst warmup system 100 comprises an engine 1, an intake pipe 2, an exhaust pipe 3, fuel supply devices 17, 18, a compressor 23 for supplying air to a combustion chamber 13 of the engine 1, a catalyst C arranged at the exhaust pipe 3, an ignition device P2 arranged at an upstream side with respect to the catalyst C in the exhaust pipe 3, and a control device 90 for controlling the engine 1. The control device 90 fixes an angle of a crankshaft CR of the engine 1, sends out an air-fuel mixture of fuel supplied to the fuel supply devices 17, 18 and air supplied by the compressor 23 to the exhaust pipe 3 from the combustion chamber 13 in a state that an exhaust port 16 of the engine 1 is opened, ignites the air-fuel mixture by the ignition device P2 in the exhaust pipe 3, and forms stationary flames in the exhaust pipe 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a catalyst warm-up system. [Background technology]

[0002] A vehicle may use a catalyst in the exhaust pipe of an engine to remove harmful substances from the exhaust gas. However, when the temperature of the catalyst is low, for example, immediately after starting the engine, the catalyst cannot efficiently remove harmful substances from the exhaust gas. Therefore, various methods have been disclosed for quickly warming up the catalyst in the exhaust pipe (see, for example, Patent Documents 1 to 3). According to the methods described in these documents, the catalyst is warmed up by combusting an air-fuel mixture once combusted in the engine again upstream of the catalyst in the exhaust pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-247655 [Patent Document 2] JP 2001-123825 A [Patent Document 3] Special Publication No. 6-508409 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned method, the start of ignition (SOI) may be delayed to generate a rich mixture for the purpose of accelerating the warm-up of the catalyst (retarded combustion). However, in this case, the combustion stability of the mixture in the exhaust pipe may deteriorate, and harmful substances in the exhaust gas may increase. In addition, in order to reduce the amount of harmful substances emitted, it is possible to increase the engine speed in order to shorten the warm-up time of the catalyst. However, in this case, vibration and noise may increase.

[0005] SUMMARY OF THE PRESENT DISCLOSURE In consideration of the above problems, an object of the present invention is to provide a catalyst warm-up system that can improve combustion stability during catalyst warm-up and reduce vibration and noise. [Means for solving the problem]

[0006] A catalyst warm-up system according to one aspect of the present invention includes an engine, an intake pipe connected to an intake port of the engine, an exhaust pipe connected to an exhaust port of the engine, a fuel supply device that supplies fuel to a combustion chamber of the engine, a compressor that supplies air to the combustion chamber of the engine, a catalyst provided in the exhaust pipe, an ignition device provided upstream of the catalyst in the exhaust pipe, and a control device that controls the engine, wherein the control device fixes the angle of the crankshaft of the engine and, with the exhaust port of the engine open, sends a mixture of fuel supplied by the fuel supply device and air supplied by the compressor from the combustion chamber to the exhaust pipe, ignites the mixture in the exhaust pipe by the ignition device, and emits air into the exhaust pipe. Continuous combustion The nozzle is configured to form a standing flame. Effect of the Invention

[0007] According to the present invention, it is possible to improve the combustion stability during catalyst warm-up and reduce vibration and noise. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a catalyst warm-up system according to an embodiment of the present invention; [Diagram 2] 2 is a flowchart showing an example of the operation of the catalyst warm-up system of FIG. 1. [Diagram 3] 2 is a flowchart showing an example of the operation of the catalyst warm-up system of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, values, etc. shown in the embodiment are merely examples for easy understanding, and do not limit the present invention unless otherwise specified. In the specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanation. In addition, elements not directly related to the present invention are not shown.

[0010] FIG. 1 is a schematic diagram showing a catalyst warm-up system 100 according to an embodiment of the present invention. The catalyst warm-up system 100 is applicable to various vehicles 500 equipped with an engine 1, and the vehicle 500 may be, for example, an HEV (Hybrid Electric Vehicle), a gasoline automobile, or a diesel automobile. In this embodiment, the vehicle 500 is described as an HEV equipped with the engine 1 and a motor 50. The catalyst warm-up system 100 includes the engine 1, the motor 50, and an ECU (Electronic Control Unit) 90 (control device). The catalyst warm-up system 100 may further include other components not shown.

[0011] The engine 1 can be, for example, a gasoline engine or a diesel engine. In this embodiment, the engine 1 is described as a gasoline engine. The engine 1 has a cylinder 11 and a piston 12. The cylinder 11 and the piston 12 define a combustion chamber 13. The piston 12 is connected to a crankshaft CR by a rod 14. A linear motion of the piston 12 is converted into a rotational motion of the crankshaft CR. A starter motor 40 is coupled to the crankshaft CR and is used, for example, when starting the engine 1. The starter motor 40 is communicatively connected to the ECU 90, and the operation of the starter motor 40 is controlled by the ECU 90. The angle of the crankshaft CR (i.e., the position of the piston 12) is detected by a crank position sensor S1. The crank position sensor S1 is communicatively connected to the ECU 90, and transmits data of the angle of the crankshaft CR to the ECU 90.

[0012] The engine 1 has an intake port 15 and an exhaust port 16. An intake valve 15a is provided in the intake port 15, and an exhaust valve 16a is provided in the exhaust port 16. The positions (openings) of the intake valve 15a and the exhaust valve 16a are controlled by, for example, a camshaft (not shown). The camshaft is rotated by a crankshaft CR via, for example, a rotating belt or the like. In this embodiment, the catalyst warm-up system 100 includes variable valve mechanisms 15b and 16b for the intake valve 15a and the exhaust valve 16a, respectively. The variable valve mechanisms 15b and 16b can change the angles of the cams of the intake valve 15a and the exhaust valve 16a relative to the camshaft, respectively, and thereby can change the openings of the intake valve 15a and the exhaust valve 16a independently of the angle of the camshaft. The variable valve mechanisms 15b and 16b can be, for example, hydraulic or electric. The variable valve mechanisms 15b, 16b are communicatively connected to the ECU 90, and the ECU 90 controls the opening degrees of the intake valve 15a and the exhaust valve 16a.

[0013] The engine 1 has a fuel (gasoline) injection port 17. The injection port 17 is provided in the combustion chamber 13, and fuel is injected from the injection port 17 into the combustion chamber 13 (so-called direct injection). An injection valve 18 for controlling the injection amount of fuel used in the engine 1 is connected to the injection port 17. In this embodiment, the fuel supply device includes the injection port 17 and the injection valve 18. The injection valve 18 is connected to the ECU 90 so as to be able to communicate with the ECU 90, and the injection amount of fuel is controlled by the ECU 90.

[0014] The engine 1 has a first spark plug P1. The first spark plug P1 is provided in the combustion chamber 13 and ignites a mixture of air and fuel in the combustion chamber 13. The first spark plug P1 is connected to the ECU 90 so as to be able to communicate with each other, and the operation of the first spark plug P1 is controlled by the ECU 90.

[0015] An intake pipe 2 is connected to the intake port 15. An air cleaner 21 is provided in the intake pipe 2, and air that has passed through the air cleaner 21 is supplied to the combustion chamber 13 via the intake port 15. A valve V1 for adjusting the amount of intake air is provided in the intake pipe 2. The valve V1 is connected to the ECU 90 so as to be able to communicate with the ECU 90, and the amount of intake air is controlled by the ECU 90.

[0016] In this embodiment, a branch pipe 22 is connected to the intake pipe 2, and a compressor 23 is provided in the branch pipe 22. In the catalyst warm-up system 100, even when the piston 12 is stopped, the compressor 23 can send air to the combustion chamber 13 of the engine 1. The compressor 23 is connected to the ECU 90, and the operation of the compressor 23 is controlled by the ECU 90. The compressor 23 includes a valve V2 for adjusting the flow rate of air. The valve V2 is disposed in, for example, the branch pipe 22. The valve V2 is connected to the ECU 90 so as to be able to communicate with the ECU 90, and the flow rate of air supplied from the compressor 23 to the combustion chamber 13 is controlled by the ECU 90.

[0017] An exhaust pipe 3 is connected to the exhaust port 16. A catalyst C for removing harmful substances from exhaust gas is disposed in the exhaust pipe 3. The catalyst C is, for example, a three-way catalyst. A temperature sensor S2 for measuring the temperature of the catalyst C is provided in the exhaust pipe 3. The temperature sensor S2 is connected to the ECU 90 so as to be able to communicate with the ECU 90, and transmits data on the temperature of the catalyst C to the ECU 90.

[0018] In the exhaust pipe 3, the catalyst C Upstream A second spark plug (ignition device) P2 is provided in the exhaust pipe 3. The second spark plug P2 ignites an air-fuel mixture in the exhaust pipe 3, thereby forming a standing flame (continuous combustion) in the exhaust pipe 3 (details will be described later). The symbol F indicates the flame front of the standing flame. The second spark plug P2 is connected to the ECU 90 so as to be able to communicate with it, and the operation of the second ignition plug P2 is controlled by the ECU 90.

[0019] In the exhaust pipe 3, a mesh 6 is provided upstream of the second ignition plug P2. The mesh 6 prevents the flame from flowing into the combustion chamber 13. The mesh 6 can be made of a metal such as stainless steel, and has a mesh size that allows gas to pass through but prevents the flame from passing through.

[0020] A flame sensor S3 for detecting the position of a flame is provided in the exhaust pipe 3. In this embodiment, the flame sensor S3 has a first temperature sensor S3a and a second temperature sensor S3b. The first temperature sensor S3a and the second temperature sensor S3b are disposed on either side of the second spark plug P2 in the flow direction of the exhaust gas.

[0021] Specifically, the first temperature sensor S3a is provided downstream of the second ignition plug P2 and upstream of the catalyst C. Preferably, the first temperature sensor S3a is provided closer to the catalyst C within a range where the catalyst C is not damaged by heat from the flame. In another aspect, the first temperature sensor S3a is provided downstream of the intended position of the flame. When the flame is located upstream of the first temperature sensor S3a as intended, the first temperature sensor S3a is exposed to the flame or the combustion gas. In this case, the first temperature sensor S3a measures the temperature of the flame or the combustion gas. In contrast, when the flame is located downstream of the first temperature sensor S3a, the first temperature sensor S3a is not exposed to the flame or the combustion gas. In this case, the first temperature sensor S3a measures the temperature of the unburned mixed gas.

[0022] From the above, by determining whether the temperature measured by the first temperature sensor S3a is equal to or higher than the first temperature T1 (for example, 1000K), which is the temperature of the combustion gas, it is possible to determine whether the flame is located upstream of the first temperature sensor S3a. When the flame is located downstream of the first temperature sensor S3a, the flow rate of the mixture is greater than the combustion speed of the flame. Therefore, when the flame is located downstream of the first temperature sensor S3a (when the temperature measured by the first temperature sensor S3a is lower than the first temperature T1), the flow rate of the mixture from the combustion chamber 13 to the exhaust pipe 3 is reduced in order to move the flame further upstream (described in detail later). Note that the above numerical value of the first temperature T1 is merely an example and is not limited thereto. For example, the first temperature T1 can be determined in advance by experiment or analysis.

[0023] The second temperature sensor S3b is provided upstream of the second spark plug P2 and downstream of the mesh 6. Preferably, the second temperature sensor S3b is provided between the second spark plug P2 and the mesh 6, closer to the second spark plug P2. In another aspect, the second temperature sensor S3b is provided upstream of the intended position of the flame. When the flame is located downstream of the second temperature sensor S3b as intended, the second temperature sensor S3b is not exposed to the flame or the combustion gas. In this case, the second temperature sensor S3b measures the temperature of the unburned mixed gas. In contrast, when the flame is located upstream of the second temperature sensor S3b, the second temperature sensor S3b is exposed to the flame or the combustion gas. In this case, the second temperature sensor S3b measures the temperature of the flame or the combustion gas.

[0024] From the above, by determining whether the temperature measured by the second temperature sensor S3b is equal to or lower than the second temperature T2 (for example, 50°C), which is the temperature of the unburned mixed gas, it is possible to determine whether the flame is located downstream of the second temperature sensor S3b. When the flame is located upstream of the second temperature sensor S3b, the combustion speed of the flame is greater than the flow rate of the mixture. Therefore, when the flame is located upstream of the second temperature sensor S3b (when the temperature measured by the second temperature sensor S3b is higher than the second temperature T2), the flow rate of the mixture from the combustion chamber 13 to the exhaust pipe 3 is increased in order to move the flame further downstream (described in detail later). Note that the above-mentioned numerical value of the second temperature T2 is merely an example and is not limited thereto. For example, the second temperature T2 can be determined in advance by experiment or analysis.

[0025] The first temperature T1 and the second temperature T2 may be stored, for example, in the storage device 92 of the ECU 90. The first temperature sensor S3a and the second temperature sensor S3b are communicatively connected to the ECU 90 and transmit data of the measured temperatures to the ECU 90.

[0026] An air-fuel ratio sensor (A / F sensor) S4 is provided in the exhaust pipe 3 downstream of the flame sensor S3 and upstream of the catalyst C. The A / F sensor S4 measures the air-fuel ratio of the mixture flowing through the exhaust pipe 3. In other words, the A / F sensor S4 can measure whether the mixture flowing through the exhaust pipe 3 is rich or lean. The A / F sensor S4 is connected to the ECU 90 so as to be able to communicate with the ECU 90, and transmits data of the measured air-fuel ratio to the ECU 90.

[0027] The ECU 90 includes components such as a processor 91 (such as a CPU) and a storage device 92 (such as a ROM and a RAM). The ECU 90 may further include other components. For example, the operation of the ECU 90 described below may be realized by the processor 91 executing a program stored in the storage device 92. The ECU 90 and the above components communicating with the ECU 90 are connected to the ECU 90 independently of each other by wiring such as a wire harness. The ECU 90 has a catalyst warm-up mode for warming the catalyst C and a flame front control mode for controlling the position of the flame front F (described in detail later).

[0028] Next, the operation of the catalyst warm-up system 100 will be described.

[0029] Fig. 2 is a flowchart showing an example of the operation of the catalyst warm-up system 100 of Fig. 1, illustrating a catalyst warm-up mode. The catalyst warm-up mode is started when, for example, the driver presses the start / stop button of the engine 1 to instruct the start of the engine 1.

[0030] The ECU 90 fixes the angle of the crankshaft CR (step S100). For example, the ECU 90 controls the starter motor 40 to rotate the crankshaft CR to a predetermined first angle and fix the crankshaft CR at the angle. For example, the first angle may be stored in the storage device 92 of the ECU 90. For example, when the engine 1 has a plurality of cylinders 11, the ECU 90 may fix the crankshaft CR to an angle at which the sizes of the combustion chambers 13 of all the cylinders 11 are the same. For example, when the engine 1 has four cylinders 11, the ECU 90 may fix the crankshaft CR to 90 degrees. In this case, the sizes of the combustion chambers 13 of all the cylinders 11 are the same, and therefore, the fuel injection amount and the air flow rate can be made the same for all the cylinders.

[0031] Next, the ECU 90 controls the variable valve mechanisms 15b, 16b to open the intake valve 15a and the exhaust valve 16a (step S102).

[0032] Next, the ECU 90 drives the compressor 23 including the valve V2 so as to continuously compress air into the combustion chamber 13 through the open intake port 15 (step S104). The ECU 90 also controls the injection valve 18 so as to continuously inject fuel into the combustion chamber 13 (step S106). As a result, a mixture of air and fuel is continuously generated in the combustion chamber 13. Also, since the exhaust valve 16a is opened in step S102, the mixture in the combustion chamber 13 is continuously supplied to the exhaust pipe 3 through the open exhaust port 16. In steps S104 and S106, the ECU 90 controls the compressor 23 including the valve V2 and the injection valve 18 so as to obtain a mixture of air and fuel with a theoretical air-fuel ratio.

[0033] Next, the ECU 90 ignites the mixture in the exhaust pipe 3 by the second ignition plug P2 (step S108). This causes the mixture in the exhaust pipe 3 to combust and form a flame. As described above, the mixture is continuously supplied to the exhaust pipe 3, so that a standing flame (continuous combustion) is formed in the exhaust pipe 3.

[0034] Next, the ECU 90 determines whether the temperature of the catalyst C is equal to or higher than a predetermined third temperature T3 based on the temperature measured by the temperature sensor S2 (step S110). The third temperature T3 is, for example, a temperature at which the catalyst C begins to perform its intended function. The third temperature T3 may be stored in the storage device 92 of the ECU 90, for example. Note that the above-mentioned third temperature T3 is merely an example and is not limited thereto.

[0035] If it is determined in step S110 that the temperature of the catalyst C is equal to or higher than the third temperature T3 (YES), the ECU 90 controls the injection valve 18 to stop the fuel (step S112) and controls the compressor 23 to stop the air (step S114), and ends the catalyst warm-up mode. When the catalyst warm-up mode ends, the ECU 90 rotates the crankshaft CR and operates the engine 1 normally.

[0036] When it is determined in step S110 that the temperature of the catalyst C is lower than the third temperature T3 (NO), the ECU 90 starts the flame front control mode described below.

[0037] FIG. 3 is a flow chart illustrating an example of the operation of the catalyst warm-up system 100 of FIG. 1, illustrating the flame front control mode.

[0038] The ECU 90 determines whether the air-fuel ratio measured by the A / F sensor S4 is within a range r1-r2 including the stoichiometric air-fuel ratio (for example, 14.7 when the fuel is gasoline) (step S200). The range r1-r2 may be a range that is considered to be approximately the stoichiometric air-fuel ratio, and may be, for example, 13-16 when the fuel is gasoline. The range r1-r2 may be stored in the storage device 92 of the ECU 90, for example. Note that the above numerical values ​​of the range r1-r2 are merely examples and are not limited to these.

[0039] If it is determined in step S200 that the air-fuel ratio is within the range r1 to r2 (YES), the ECU 90 determines whether the temperature measured by the second temperature sensor S3b is equal to or lower than a second temperature T2 (for example, 50° C.) (step S202).

[0040] In step S202, if it is determined that the temperature measured by the second temperature sensor S3b is equal to or lower than the second temperature T2 (YES), it is determined that the flame is downstream of the second temperature sensor S3b. Next, the ECU 90 determines whether the temperature measured by the first temperature sensor S3a is equal to or higher than the first temperature T1 (e.g., 1000 K) (step S204).

[0041] If it is determined in step S204 that the temperature measured by the first temperature sensor S3a is higher than the first temperature T1 (YES), it is determined that the flame is downstream of the second temperature sensor S3b and upstream of the first temperature sensor S3a (i.e., the intended position of the flame). Then, the ECU 90 returns to step S110 in FIG. 2 and again determines whether the temperature of the catalyst C is equal to or higher than the third temperature T3.

[0042] Referring to FIG. 3, if it is determined in step S200 that the air-fuel ratio is not within the range r1-r2 (NO), the ECU 90 determines whether the air-fuel ratio is less than the lower limit r1 (that is, whether the mixture is lean) (step S206).

[0043] If it is determined in step S206 that the air-fuel ratio is less than the lower limit r1 (that is, the mixture is lean) (YES), the ECU 90 controls the injection valve 18 to increase fuel (step S208) and returns to step S200.

[0044] If it is determined in step S206 that the air-fuel ratio is not less than the lower limit r1 (NO), the air-fuel ratio is not in the range r1-r2 and is not less than the lower limit r1, so the air-fuel ratio is determined to be higher than r2 (i.e., the mixture is rich). Therefore, the ECU 90 controls the injection valve 18 to reduce the fuel (step S210), and returns to step S200.

[0045] In step S202, if it is determined that the temperature measured by the second temperature sensor S3b is higher than the second temperature T2 (NO), it is determined that the flame is upstream of the second temperature sensor S3b. Therefore, the ECU 90 controls the compressor 23 including the valve V2 and the injection valve 18 to increase the air and fuel in order to increase the flow rate of the mixture so as to move the flame further downstream (step S212). Since it is determined in the above step S200 that the mixture is approximately at the stoichiometric air-fuel ratio, the ECU 90 controls the compressor 23 and the injection valve 18 to increase the air and fuel while maintaining the air-fuel ratio. Then, the ECU 90 returns to step S202.

[0046] In step S204, when it is determined that the temperature measured by the first temperature sensor S3a is less than the first temperature T1 (NO), it is determined that the flame is downstream of the first temperature sensor S3a. Therefore, the ECU 90 controls the compressor 23 including the valve V2 and the injection valve 18 to reduce the air and fuel in order to reduce the flow rate of the mixture in order to move the flame further upstream (step S214). The ECU 90 controls the compressor 23 and the injection valve 18 to reduce the air and fuel while maintaining the air-fuel ratio. Then, the ECU 90 returns to step S202.

[0047] During the catalyst warm-up mode and the flame front control mode as described above, the crankshaft CR is fixed, and therefore the ECU 90 controls the motor 50 so that the vehicle 500 runs using the power from the motor 50.

[0048] The catalyst warm-up system 100 as described above includes an engine 1, an intake pipe 2 connected to an intake port 15 of the engine 1, an exhaust pipe 3 connected to an exhaust port 16 of the engine 1, an injection port 17 and an injection valve 18 that supply fuel to a combustion chamber 13 of the engine 1, a compressor 23 that supplies air to the combustion chamber 13 of the engine 1, a catalyst C provided in the exhaust pipe 3, a second ignition plug P2 provided upstream of the catalyst C in the exhaust pipe 3, and an ECU 90 that controls the engine 1. The ECU 90 is configured to fix the angle of the crankshaft CR of the engine 1 and open the exhaust port 16 of the engine 1, send a mixture of fuel supplied by the injection port 17 and the injection valve 18 and air supplied by the compressor 23 from the combustion chamber 13 to the exhaust pipe 3, and ignite the mixture in the exhaust pipe 3 by the second ignition plug P2 to form a standing flame in the exhaust pipe 3. In this way, in the catalyst warm-up system 100, a standing flame is formed in the exhaust pipe 3, so that the combustion stability during catalyst warm-up can be improved. Therefore, the catalyst warm-up time can be shortened. Also, in the catalyst warm-up system 100, the crankshaft CR is fixed during catalyst warm-up, so that the vibration and noise caused by the rotation of the crankshaft CR can be reduced.

[0049] Moreover, in the catalyst warm-up system 100, the compressor 23 is provided in a branch pipe 22 connected to the intake pipe 2, and supplies air from the intake port 15 of the engine 1 to the combustion chamber 13 through the branch pipe 22 and the intake pipe 2. Therefore, there is no need to form an opening for the compressor 23 in the cylinder 11, and the intake port 15 and the intake pipe 2 can be used.

[0050] The catalyst warm-up system 100 also includes a flame sensor S3 that is provided in the exhaust pipe 3 and detects the position of the flame in the exhaust pipe 3. Therefore, the flame sensor S3 can detect whether or not the flame is formed at the intended position, and therefore it is possible to prevent components such as the catalyst C from being damaged by the flame.

[0051] In the catalyst warm-up system 100, the flame sensor S3 includes a first temperature sensor S3a that is provided downstream of the second point or plug P2 in the exhaust pipe 3. Therefore, the position of the flame can be confirmed by the first temperature sensor S3a. Therefore, for example, the catalyst C can be protected from damage caused by heat from the flame.

[0052] Moreover, in the catalyst warm-up system 100, the flame sensor S3 further includes a second temperature sensor S3b that is provided upstream of the second ignition plug P2 in the exhaust pipe 3. Therefore, the position of the flame can be further confirmed by the second temperature sensor S3b.

[0053] In addition, in the catalyst warm-up system 100, the ECU 90 determines whether the temperature measured by the second temperature sensor S3b is equal to or lower than the second temperature T2, which is the temperature of the unburned mixed gas, and controls the injection valve 18 and the compressor 23 to increase the flow rate of the mixture when it is determined that the temperature measured by the second temperature sensor S3b is higher than the second temperature T2. As described above, when the temperature measured by the second temperature sensor S3b is higher than the second temperature T2, the second temperature sensor S3b is exposed to the flame or the combustion gas, and therefore the flame is located upstream of the second temperature sensor S3b. In this case, in the catalyst warm-up system 100, the flow rate of the mixture is increased to move the flame downstream, so that the flame can be moved downstream of the second temperature sensor S3b (i.e., to the intended position of the flame).

[0054] In addition, in the catalyst warm-up system 100, the ECU 90 determines whether the temperature measured by the first temperature sensor S3a is equal to or higher than the first temperature T1, which is the temperature of the combustion gas, and controls the injection valve 18 and the compressor 23 to reduce the flow rate of the mixture when it is determined that the temperature measured by the first temperature sensor S3a is lower than the first temperature T1. As described above, when the temperature measured by the first temperature sensor S3a is lower than the first temperature T1, the first temperature sensor S3a is not exposed to the flame or the combustion gas, and therefore the flame is located downstream of the first temperature sensor S3a. In this case, in the catalyst warm-up system 100, the flow rate of the mixture is reduced to move the flame upstream, so that the flame can be moved upstream of the first temperature sensor S3a (i.e., to the intended position of the flame).

[0055] The catalyst warm-up system 100 further includes an air-fuel ratio sensor S4 that is provided downstream of the catalyst C in the exhaust pipe 3 and measures the air-fuel ratio of the mixture, and the ECU 90 controls the injection valve 18 and the compressor 23 based on the measurement result of the air-fuel ratio sensor S4 so that the air-fuel ratio of the mixture is within a predetermined range r1 to r2 including the stoichiometric air-fuel ratio. In this way, the mixture having the stoichiometric air-fuel ratio or approximately the stoichiometric air-fuel ratio is burned in the exhaust pipe 3. In the catalyst warm-up system 100, the fuel flows from the combustion chamber 13 to the second ignition plug P2 in the exhaust pipe 3, so that time for the fuel to vaporize can be secured. Therefore, harmful substances in the combustion gas can be reduced.

[0056] Although the embodiment has been described above with reference to the accompanying drawings, the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that such modifications and alterations naturally fall within the technical scope of the present invention. In addition, the steps of the ECU 90 in the above embodiment do not have to be performed in the above order, and may be performed in a different order as long as no technical contradiction occurs.

[0057] For example, in the above embodiment, the fuel nozzle 17 is provided in the engine 1. However, in other embodiments, the nozzle 17 may be provided in the intake pipe 2 (so-called premixed).

[0058] Also, in the above embodiment, the vehicle 500 is described as an HEV. However, in other embodiments, the vehicle 500 may be a vehicle other than an HEV, such as a gasoline vehicle. For example, if the vehicle 500 is a gasoline vehicle, the ECU 90 may move the vehicle 500 after the catalyst warm-up mode is completed.

[0059] In the above embodiment, the air-fuel ratio sensor S4 is used. However, in other embodiments, an O2 sensor, for example, may be used instead of the air-fuel ratio sensor S4.

[0060] Also, in the above embodiment, the compressor 23 is connected to the intake pipe 2 via the branch pipe 22. However, in other embodiments, the compressor 23 may be connected directly to the combustion chamber 13 without via the intake pipe 2. For example, the compressor 23 may be connected to the combustion chamber 13 via a pipe connected to the cylinder 11 at a position above the top dead center. [Explanation of symbols]

[0061] 1 Engine 3. Exhaust pipe 13 Combustion chamber 16 Exhaust port 16a Exhaust valve 18 Injection valve 23 Compressor 90 ECU (control unit) 100 Catalyst warm-up system C catalyst CR crankshaft P2 Second spark plug (ignition device) S3 Flame Sensor S3a 1st Temperature Sensor S3b Second temperature sensor

Claims

1. The engine, an intake pipe connected to an intake port of the engine; an exhaust pipe connected to an exhaust port of the engine; a fuel supply device for supplying fuel to a combustion chamber of the engine; a compressor for supplying air to a combustion chamber of the engine; A catalyst provided in the exhaust pipe; an ignition device provided in the exhaust pipe upstream of the catalyst; A control device for controlling the engine; Equipped with The control device includes: a crankshaft angle of the engine is fixed and the exhaust port of the engine is open, a mixture of fuel supplied by the fuel supply device and air supplied by the compressor is sent from the combustion chamber to the exhaust pipe, and the mixture is ignited by the ignition device in the exhaust pipe to form a standing flame, which is continuous combustion, in the exhaust pipe; A catalyst warm-up system configured as follows.

2. 2. The catalyst warm-up system according to claim 1, wherein the compressor is provided in a branch pipe connected to the intake pipe, and supplies air from the intake port of the engine to the combustion chamber through the branch pipe and the intake pipe.

3. 3. The catalyst warm-up system according to claim 1, further comprising a flame sensor provided in the exhaust pipe for detecting a position of the standing flame within the exhaust pipe.

4. 4. The catalyst warm-up system according to claim 3, wherein the flame sensor comprises a first temperature sensor provided in the exhaust pipe downstream of the ignition device and upstream of the catalyst.

5. 5. The catalyst warm-up system according to claim 4, wherein the flame sensor further comprises a second temperature sensor provided in the exhaust pipe upstream of the ignition device.

6. Further comprising a catalyst temperature sensor provided in the exhaust pipe and measuring a temperature of the catalyst, 6. The catalyst warm-up system according to claim 5, wherein the control device controls the fuel supply device and the compressor based on the detection results of the first temperature sensor and the second temperature sensor when the temperature of the catalyst measured by the catalyst temperature sensor is lower than a predetermined temperature, and performs flame front control to form the standing flame between the first temperature sensor and the second temperature sensor.

7. A catalyst warm-up system as described in any one of claims 1 to 6, wherein a mesh is provided upstream of the ignition device to prevent the standing flame from flowing into the combustion chamber.

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