Catalyst warming-up control device for engine

Abstract

To provide a catalyst warming-up control device for an engine capable of suppressing deterioration of exhaust gas performance while securing brake performance.SOLUTION: When negative pressure within a negative pressure chamber of a brake booster runs short (S5), an ECU stops catalyst warming-up control for controlling an operating state of an engine so that a catalyst device is warmed up by exhaust gas of the engine (S6). While the catalyst warming-up control is being stopped, when the negative pressure within the negative pressure chamber recovers (S8), the ECU resumes the catalyst warming-up control (S9).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a catalyst warm-up control device for an engine. [Background technology]

[0002] Conventionally, in a vehicle equipped with a brake booster that uses the engine's intake vacuum as a boosting source, a technology is proposed in Patent Document 1 in which the engine ignition timing is retarded to warm up the catalyst, and if a lack of vacuum in the brake booster is detected while the retard control is being performed, the retard control is stopped to ensure braking performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-355494 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional technology described above has the problem that when a lack of negative pressure in the brake booster is detected, the catalyst is not warmed up by retard control, which means that it takes time for the catalyst to become active, resulting in a decrease in exhaust gas performance.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide an engine catalyst warm-up control device that can suppress a decline in exhaust gas performance while maintaining braking performance. [Means for solving the problem]

[0006] The engine catalyst warm-up control device of the present invention is provided in a vehicle having an engine, a catalytic device that purifies the engine's exhaust gas, a brake booster that increases braking force by using the engine's intake negative pressure, and a control unit that executes catalyst warm-up control that controls the operating state of the engine so that the catalytic device is warmed up by the engine's exhaust gas, and the control unit is configured to stop the catalyst warm-up control when the negative pressure in the negative pressure chamber of the brake booster is insufficient, and to resume the catalyst warm-up control when the negative pressure in the negative pressure chamber is restored while the catalyst warm-up control is stopped. [Effects of the Invention]

[0007] The present invention can provide a catalyst warm-up control device for an engine that can suppress a decrease in exhaust gas performance while ensuring braking performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with an engine catalyst warm-up control device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing the catalyst warm-up control operation of the engine catalyst warm-up control device according to one embodiment of the present invention. [Figure 3] FIG. 3 is a timing chart showing a first example of the state of each part when the catalyst warm-up control operation of the engine catalyst warm-up control device according to one embodiment of the present invention is executed. [Figure 4] FIG. 4 is a timing diagram showing a second example of the state of each part when the catalyst warm-up control operation of the engine catalyst warm-up control device according to one embodiment of the present invention is executed. DETAILED DESCRIPTION OF THE INVENTION

[0009] An engine catalyst warm-up control device according to one embodiment of the present invention is provided in a vehicle having an engine, a catalytic converter that purifies engine exhaust gas, a brake booster that increases braking force by using engine intake negative pressure, and a control unit that executes catalyst warm-up control that controls the operating state of the engine so that the catalytic converter is warmed up by the engine exhaust gas, and is characterized in that the control unit stops the catalyst warm-up control when the negative pressure in the negative pressure chamber of the brake booster is insufficient, and resumes the catalyst warm-up control when the negative pressure in the negative pressure chamber is restored while the catalyst warm-up control is stopped. As a result, the engine catalyst warm-up control device according to one embodiment of the present invention can suppress a deterioration in exhaust gas performance while maintaining braking performance. [Example]

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle equipped with an engine catalyst warm-up control device according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0011] As shown in Fig. 1, a vehicle 1 includes an engine 2, a brake booster 3, and an ECU (Electronic Control Unit) 4. The engine 2 has a plurality of cylinders. In this embodiment, the engine 2 generates power by performing a series of four strokes for each cylinder, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0012] The engine 2 is provided with an intake manifold 10 for introducing a mixture of air and fuel or air mixed with fuel into the combustion chamber of the engine 2, and an exhaust manifold 11 for discharging exhaust gas generated in the combustion chamber of the engine 2 to the outside of the vehicle.

[0013] The intake manifold 10 is provided with an air cleaner 20 that purifies the air taken in by the engine 2, a throttle body 21 that houses a throttle valve for adjusting the flow rate of air introduced into the combustion chamber of the engine 2, and a surge tank 22 that suppresses pulsation and interference of the air introduced into the combustion chamber of the engine 2.

[0014] The exhaust manifold 11 is provided with a catalytic converter 25 that purifies harmful substances in the exhaust gas. The catalytic converter 25 has a three-way catalyst that removes harmful substances such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. The three-way catalyst oxidizes HC to water and carbon dioxide, oxidizes CO to carbon dioxide, and reduces NOx to nitrogen.

[0015] The brake booster 3 increases the operating force of the brake pedal 16, thereby increasing the braking force of the vehicle 1. The operating force of the brake pedal 16 increased by the brake booster 3 is transmitted to the brake device of the vehicle 1 via a hydraulic circuit (not shown).

[0016] The brake booster 3 is formed with a negative pressure chamber 3a that is connected to the surge tank 22 and stores negative pressure, and an atmospheric pressure chamber 3b to which atmospheric pressure is applied. The brake booster 3 amplifies the operating force applied to the brake pedal 16 by the pressure difference between the pressure in the negative pressure chamber 3a and the pressure in the atmospheric pressure chamber 3b.

[0017] The ECU4 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

[0018] The ROM of this computer unit stores various constants, various maps, etc., as well as a program for causing the computer unit to function as the ECU 4. That is, the CPU executes the program stored in the ROM using the RAM as a work area, causing the computer unit to function as the ECU 4 in this embodiment.

[0019] The input port of the ECU 4 is connected to various sensors, including a vehicle speed sensor 30 that detects the vehicle speed, a brake switch 31 that detects the operation state of the brake pedal 16, a negative pressure sensor 32 that detects the pressure in the negative pressure chamber 3a of the brake booster 3, and a catalyst temperature sensor 33 that detects the temperature of the catalyst device 25.

[0020] The output port of the ECU 4 is connected to various control objects including an injector 40 that supplies fuel to the engine 2 and an ignition plug 41 that ignites in the combustion chamber of the engine 2. The ECU 4 controls the various control objects connected to the output port based on information obtained from various sensors connected to the input port.

[0021] The ECU 4 functions as a control unit 50 that executes catalyst warm-up control to control the operating state of the engine 2 so that the catalytic converter 25 is warmed up by the exhaust gas of the engine 2. In this embodiment, the ECU 4 executes the catalyst warm-up control by retarding the ignition timing of the spark plug 41.

[0022] When the engine 2 starts, the ECU 4 determines that the conditions for operating the catalyst warm-up control are met, and executes the catalyst warm-up control until the temperature detected by the catalyst temperature sensor 33 becomes equal to or higher than a predetermined temperature Tc. The predetermined temperature Tc is determined in advance based on the activation temperature of the catalytic converter 25.

[0023] If the pressure detected by the negative pressure sensor 32 becomes higher than a first threshold value TH1 while the catalyst warm-up control is being executed, the ECU 4 determines that the negative pressure in the negative pressure chamber 3a is insufficient and stops the catalyst warm-up control. The first threshold value TH1 is determined in advance based on the upper limit of the pressure in the negative pressure chamber 3a at which the brake booster 3 can function.

[0024] In this embodiment, the ECU 4 stops the catalyst warm-up control if all three conditions (hereinafter simply referred to as "catalyst warm-up control stop conditions") are met: a first condition that the vehicle speed detected by the vehicle speed sensor 30 is higher than a predetermined speed Vth; a second condition that the brake pedal 16 is detected by the brake switch 31 to be in an ON state (hereinafter simply referred to as "brake ON"); and a third condition that the pressure detected by the negative pressure sensor 32 is higher than a first threshold value TH1; and if none of the catalyst warm-up control stop conditions are met, the ECU 4 does not stop the catalyst warm-up control.

[0025] If a catalyst warm-up control resumption condition is met during the period when the catalyst warm-up control is stopped, that is, the pressure detected by the negative pressure sensor 32 becomes equal to or lower than a second threshold value TH2 that is lower than the first threshold value TH1, the ECU 4 resumes the catalyst warm-up control. The second threshold value TH2 is predetermined based on a value at which it is determined that the negative pressure in the negative pressure chamber 3a has recovered to an extent that allows the brake booster 3 to function sufficiently.

[0026] The ECU 4 prohibits the execution of catalyst warm-up control when the cumulative time during which the catalyst warm-up control is stopped (hereinafter simply referred to as the "catalyst warm-up cumulative stop time") exceeds a predetermined time S. The predetermined time S is set in advance to a time during which the warm-up of the catalytic converter 25 is sufficiently completed.

[0027] In other words, when the cumulative catalyst warm-up stop time reaches or exceeds a predetermined time S, the ECU 4 determines that some malfunction has occurred in the vehicle 1, prioritizes safety, and prohibits the execution of catalyst warm-up control to ensure that the brake booster 3 functions reliably.

[0028] Once the ECU 4 has prohibited the execution of catalyst warm-up control, it continues to prohibit the execution of catalyst warm-up control until the driving cycle ends. In other words, once the ECU 4 has prohibited the execution of catalyst warm-up control, it continues to prohibit the execution of catalyst warm-up control until the ignition switch is turned off.

[0029] When the next driving cycle is started while the execution of catalyst warm-up control is prohibited, the ECU 4 permits the execution of catalyst warm-up control because there is a possibility that the malfunction occurring in the vehicle 1 will be resolved. That is, when the ignition switch is turned on, the ECU 4 permits the execution of catalyst warm-up control and resets the cumulative catalyst warm-up stop time to 0.

[0030] The catalyst warm-up control operation performed by the ECU 4 configured as above will be described with reference to Fig. 2. The catalyst warm-up control operation described below is repeatedly executed while the ECU 4 is in operation.

[0031] First, in S1, the ECU 4 determines whether or not the engine 2 has started. If it is determined in S1 that the engine 2 has started, the ECU 4 executes the process of S2. If it is determined in S1 that the engine 2 has not started, the ECU 4 ends the catalyst warm-up control operation.

[0032] In S2, the ECU 4 executes catalyst warm-up control. After executing the process of S2, the ECU 4 executes the process of S3. In S3, the ECU 4 determines whether the vehicle speed detected by the vehicle speed sensor 30 is higher than a predetermined speed Vth.

[0033] If it is determined in S3 that the vehicle speed detected by the vehicle speed sensor 30 is higher than the predetermined speed Vth, the ECU 4 executes the process of S4. If it is determined in S3 that the vehicle speed detected by the vehicle speed sensor 30 is not higher than the predetermined speed Vth, the ECU 4 executes the process of S10.

[0034] In S4, the ECU 4 determines whether or not the brake switch 31 has detected that the brake is ON. If it is determined in S4 that the brake switch 31 has detected that the brake is ON, the ECU 4 executes the process of S5. If it is determined in S4 that the brake switch 31 has not detected that the brake is ON, the ECU 4 executes the process of S10.

[0035] In S5, the ECU 4 determines whether the pressure detected by the negative pressure sensor 32 is higher than the first threshold value TH1. If it is determined in S5 that the pressure detected by the negative pressure sensor 32 is higher than the first threshold value TH1, the ECU 4 executes the process of S6. If it is determined in S5 that the pressure detected by the negative pressure sensor 32 is not higher than the first threshold value TH1, the ECU 4 executes the process of S10.

[0036] In S6, the ECU 4 stops the catalyst warm-up control. After executing the process of S6, the ECU 4 executes the process of S7. In S7, the ECU 4 determines whether the cumulative catalyst warm-up stop time is less than a predetermined time S.

[0037] If it is determined in S7 that the cumulative catalyst warm-up stop time is less than the predetermined time S, the ECU 4 executes the process of S8. If it is determined in S7 that the cumulative catalyst warm-up stop time is not less than the predetermined time S, the ECU 4 executes the process of S12.

[0038] In S8, the ECU 4 determines whether the pressure detected by the negative pressure sensor 32 is equal to or less than the second threshold value TH2. If it is determined in S8 that the pressure detected by the negative pressure sensor 32 is equal to or less than the second threshold value TH2, the ECU 4 executes the process of S9. If it is determined in S8 that the pressure detected by the negative pressure sensor 32 is not equal to or less than the second threshold value TH2, the ECU 4 executes the process of S7.

[0039] In S9, the ECU 4 resumes the catalyst warm-up control. After executing the process of S9, the ECU 4 executes the process of S10. In S10, the ECU 4 determines whether the temperature detected by the catalyst temperature sensor 33 has reached or exceeded a predetermined temperature Tc.

[0040] If it is determined in S10 that the temperature detected by the catalyst temperature sensor 33 is equal to or higher than the predetermined temperature Tc, the ECU 4 executes the process of S11. If it is determined in S10 that the temperature detected by the catalyst temperature sensor 33 is not equal to or higher than the predetermined temperature Tc, the ECU 4 executes the process of S3. In S11, the ECU 4 ends the catalyst warm-up control. After executing the process of S11, the ECU 4 ends the catalyst warm-up control operation.

[0041] In S12, the ECU 4 prohibits the execution of catalyst warm-up control. After executing the process of S12, the ECU 4 ends the catalyst warm-up control. Note that if the execution of catalyst warm-up control is prohibited in S12, the ECU 4 does not execute the catalyst warm-up control operation until the driving cycle ends.

[0042] The action of the catalyst warm-up control operation described above will be explained with reference to Figures 3 and 4. Figures 3 and 4 show, from top to bottom, examples of the vehicle speed detected by the vehicle speed sensor 30, the operation state of the brake pedal 16 detected by the brake switch 31 (simply referred to as "BRAKE" in the figures), the pressure in the negative pressure chamber 3a detected by the negative pressure sensor 32 (simply referred to as "booster negative pressure value" in the figures), the operating state of the catalyst warm-up control, and the cumulative catalyst warm-up stop time in chronological order.

[0043] 3, when the engine 2 starts at time t0, catalyst warm-up control is initiated by the ECU 4. At time t1, when all three conditions are met (i.e., catalyst warm-up control stop conditions), namely, a first condition that the vehicle speed detected by the vehicle speed sensor 30 is higher than a predetermined speed Vth, a second condition that the brake is ON by the brake switch 31, and a third condition that the pressure detected by the negative pressure sensor 32 is higher than a first threshold value TH1), the ECU 4 stops the catalyst warm-up control and starts accumulating the cumulative catalyst warm-up stop time.

[0044] At time t2, when the catalyst warm-up control resumption condition is met in which the pressure detected by the negative pressure sensor 32 becomes equal to or lower than the second threshold value TH2, the ECU 4 resumes catalyst warm-up control and stops accumulating the cumulative catalyst warm-up stop time.

[0045] At time t3, when the catalyst warm-up control stop condition is met, the ECU 4 stops the catalyst warm-up control and starts accumulating the cumulative catalyst warm-up stop time. At time t4, when the catalyst warm-up control restart condition is met, the ECU 4 restarts the catalyst warm-up control and stops accumulating the cumulative catalyst warm-up stop time. At time t5, when the temperature detected by the catalyst temperature sensor 33 becomes equal to or higher than the predetermined temperature Tc, the ECU 4 ends the catalyst warm-up control.

[0046] 4, when the engine 2 starts at time t10, catalyst warm-up control is started by the ECU 4. When the catalyst warm-up control stop condition is met at time t11, the catalyst warm-up control is stopped by the ECU 4, and the accumulation of the cumulative catalyst warm-up stop time is started.

[0047] At time t12, when the catalyst warm-up control resumption condition is met, that is, the pressure detected by the negative pressure sensor 32 becomes equal to or lower than the second threshold value TH2, the ECU 4 resumes the catalyst warm-up control and stops accumulating the cumulative catalyst warm-up stop time.

[0048] At time t13, when the catalyst warm-up control stop condition is met, the ECU 4 stops the catalyst warm-up control and starts accumulating the cumulative catalyst warm-up stop time. At time t14, when the cumulative catalyst warm-up stop time reaches or exceeds a predetermined time S, the ECU 4 prohibits the execution of the catalyst warm-up control. Therefore, after time t14, the catalyst warm-up control is not resumed even if the catalyst warm-up control resumption condition is met.

[0049] As described above, the engine catalyst warm-up control device according to this embodiment can ensure braking performance by stopping catalyst warm-up control when the negative pressure in the negative pressure chamber 3a of the brake booster 3 becomes insufficient.

[0050] Furthermore, the catalyst warm-up control device for an engine according to this embodiment resumes catalyst warm-up control when the negative pressure in the negative pressure chamber 3a is restored while the catalyst warm-up control is stopped, thereby reducing the time required for catalyst activation and suppressing a deterioration in exhaust gas performance. Therefore, the catalyst warm-up control device for an engine according to this embodiment can suppress a deterioration in exhaust gas performance while ensuring braking performance.

[0051] In addition, the catalyst warm-up control device for the engine of this embodiment can suppress a decline in exhaust gas performance by maximizing catalyst warm-up control within the range that ensures braking performance even in environments with low atmospheric pressure, thereby reducing the time required for catalyst activation.

[0052] In addition, the catalyst warm-up control device of the engine in this embodiment determines that the negative pressure in the vacuum chamber 3a is insufficient when the pressure in the vacuum chamber 3a becomes higher than a first threshold value TH1, and determines that the negative pressure in the vacuum chamber 3a has recovered when the pressure in the vacuum chamber 3a becomes equal to or lower than a second threshold value that is lower than the first threshold value, thereby preventing the occurrence of vibrations in the vehicle body due to hunting, which occurs when the catalyst warm-up control is stopped and restarted frequently and repeatedly in a short period of time.

[0053] In addition, the catalyst warm-up control device for the engine according to this embodiment prohibits the execution of catalyst warm-up control when the cumulative catalyst warm-up stop time reaches or exceeds a predetermined time S, thereby prioritizing braking performance and ensuring the safety of passengers.

[0054] In this embodiment, the ECU 4 executes the catalyst warm-up control by retarding the ignition timing of the spark plug 41. However, the ECU 4 may execute the catalyst warm-up control by other means as long as the catalyst warm-up control involves an increase in the amount of intake air of the engine 2.

[0055] For example, if vehicle 1 is configured as a vehicle having VVT (Variable Valve Timing), ECU 4 may perform catalyst warm-up control by advancing the opening timing of the exhaust valve of engine 2 to increase the temperature of the exhaust gas.

[0056] Furthermore, if the vehicle 1 is configured as a vehicle having a VVT, the ECU 4 may execute catalyst warm-up control by delaying the closing timing of the exhaust valve of the engine 2 to raise the temperature of the exhaust gas.

[0057] In addition, in this embodiment, an example has been described in which, when the ECU 4 determines that the operating conditions for catalyst warm-up control are met, it executes catalyst warm-up control until the temperature detected by the catalyst temperature sensor 33 becomes equal to or higher than the predetermined temperature Tc.

[0058] In contrast, when the ECU 4 determines that the conditions for operating the catalyst warm-up control are met, it may execute the catalyst warm-up control until the cumulative value of the amount of air taken into the engine 2 since the engine 2 started exceeds a predetermined value Sa.

[0059] In this case, the predetermined value Sa is determined in advance so as to increase as the activation temperature of the catalyst device 25 increases. By configuring in this manner, the catalyst temperature sensor 33 can be omitted from the configuration of the vehicle 1.

[0060] While the present invention has been described with reference to an embodiment, it will be apparent that modifications may be made thereto without departing from the spirit and scope of the present invention, and the present invention is disclosed with the understanding that equivalents of such modifications are intended to be encompassed within the scope of the appended claims. [Explanation of symbols]

[0061] 1 vehicle 2 engines 3 Brake booster 3a Negative pressure chamber 25 Catalytic converter 50 control section

Claims

1. The engine and a catalytic converter for purifying exhaust gas from the engine; a brake booster that increases braking force by using the intake negative pressure of the engine; a control unit that executes catalyst warm-up control to control the operating state of the engine so that the catalytic device is warmed up by exhaust gas from the engine, The control unit When the negative pressure in the negative pressure chamber of the brake booster becomes insufficient, the catalyst warm-up control is stopped, When the negative pressure in the negative pressure chamber is restored while the catalyst warm-up control is stopped, the catalyst warm-up control is resumed. A catalyst warm-up control device for an engine.

2. The control unit When the pressure in the negative pressure chamber becomes higher than a first threshold value, it is determined that the negative pressure in the negative pressure chamber is insufficient, When the pressure in the negative pressure chamber becomes equal to or lower than a second threshold value that is lower than the first threshold value, it is determined that the negative pressure in the negative pressure chamber has recovered.

2. The catalyst warm-up control device for an engine according to claim 1.

3. The control unit When the cumulative time during which the negative pressure in the negative pressure chamber is insufficient reaches or exceeds a predetermined time, execution of the catalyst warm-up control is prohibited.

3. The catalyst warm-up control device for an engine according to claim 1 or 2.

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