JP5999038B2 - EGR valve control device for internal combustion engine - Google Patents

Description

  The present invention relates to an EGR valve control device for an internal combustion engine, and more particularly to an EGR valve control device for an internal combustion engine applied to an internal combustion engine having an EGR valve device that controls the amount of EGR gas by energizing a step motor. .

  Conventionally, an EGR valve device provided in a passage that connects an exhaust system and an intake system of an internal combustion engine is controlled by energizing a step motor, thereby recirculating a part of the exhaust gas to the intake system. Circulation (EGR) is known. Many internal combustion engines that perform such EGR stop (cut) energization of the step motor not only when the internal combustion engine is stopped due to ignition off but also when the internal combustion engine is stopped due to idling stop in order to reduce power consumption.

  In this type of internal combustion engine, when the energization of the step motor is stopped, control is performed to move the EGR valve to a position that serves as a reference for the step number of the step motor. However, the internal combustion engine is restarted before the EGR valve movement is completed. When the engine is started, the stepping motor may be stepped out.

  Thus, for example, Patent Document 1 discloses a technique for controlling the step motor so that the EGR valve hits the reference position when the movement of the EGR valve is not completed at the start of energization of the step motor.

JP 2002-044993 A

  As an EGR valve device that opens and closes by energizing a stepping motor, for example, an EGR valve having a valve body and a shaft is provided so as to close an exhaust gas outlet formed in the motor housing from the outside of the housing, and the EGR valve is connected to the motor. A device connected to a step motor in a housing is known. In such an EGR valve device, the amount of EGR gas is controlled by changing the flow path opening area between the valve body of the EGR valve and the valve seat of the exhaust gas outlet by displacing the EGR valve by a step motor.

  However, such an EGR valve device may cause the following problems. That is, if the power supply to the step motor is cut when the internal combustion engine is stopped due to idling stop or the like, the temperature of the motor housing is lowered, which may cause the motor housing to shrink. On the other hand, since the EGR valve is usually made of a material having a low expansion coefficient, it hardly shrinks even when the temperature of the motor housing is lowered. For this reason, when the temperature of the motor housing decreases due to the cut off of the energization to the stepping motor, the zero point of the stepping motor may be displaced in the direction in which the EGR valve can be easily opened. In this case, since the EGR valve is likely to open earlier than expected, the amount of EGR gas recirculated to the intake system becomes larger than expected, and there is a problem that combustion is worsened by introducing a large amount of EGR gas.

  The present invention has been made in view of such a point, and an object of the present invention is to start energization of a step motor in an internal combustion engine including an EGR valve device that controls the amount of EGR gas by energizing the step motor. At this time, it is to provide a technique for suppressing the deterioration of combustion accompanying the introduction of EGR gas.

  In order to achieve the above object, in the present invention, when energization is performed after the energization cut to the stepping motor, the EGR gas amount is adjusted based on the fact that the motor housing is contracted.

  Specifically, the present invention is an EGR valve that is provided in an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine, and controls the amount of EGR gas flowing from the exhaust passage to the intake passage by energizing a step motor. The present invention is directed to an EGR valve control device for an internal combustion engine applied to an internal combustion engine equipped with the device.

The EGR valve control device cuts off the energization to the step motor while the internal combustion engine is stopped, and starts energizing the step motor at the start of introduction of EGR gas. When the elapsed time is short, the EGR gas amount reduction correction amount is increased as compared with the case where the elapsed time is long, and the EGR gas amount reduction correction amount is gradually decreased as the elapsed time becomes longer. It is characterized by making it.

  In the present invention, “when the introduction of EGR gas starts” means, for example, when the internal combustion engine is cold-started after the internal combustion engine is stopped due to ignition off, the cooling water temperature of the internal combustion engine becomes equal to or higher than a predetermined temperature. For example, when the internal combustion engine is restarted after the internal combustion engine is stopped due to idling stop, it means when the internal combustion engine is restarted.

  According to this configuration, the power supply to the step motor is cut off not only when the internal combustion engine is stopped due to ignition off but also when the internal combustion engine is stopped due to idling stop, so that power consumption can be reduced and fuel consumption can be improved. .

  However, if the power supply to the step motor is cut off while the internal combustion engine is stopped, the temperature of the motor housing of the EGR valve device is reduced and the motor housing is contracted, so that the zero point of the step motor tends to open the EGR valve. The EGR valve may be easily opened quickly. Immediately after starting the energization of the step motor, the amount of contraction of the motor housing is large, so that the amount of EGR gas passing through the EGR valve is greatly increased from the target amount of EGR gas, and the combustion deteriorates. There is a fear.

  In this regard, according to the above configuration, when the elapsed time after the start of energization is short, the correction amount for reducing the EGR gas amount is increased as compared with the case where the elapsed time is long, so the amount of contraction of the motor housing is large. Immediately after the start of energization, it is possible to suppress the deterioration of combustion associated with the introduction of EGR gas.

  On the other hand, when the temperature of the motor housing rises after a certain amount of time has elapsed since the start of energization, the amount of shrinkage of the motor housing decreases. According to the above configuration, when the elapsed time after the start of energization is long, the EGR gas amount Therefore, the amount of EGR gas can be made appropriate.

  As described above, according to the EGR valve control apparatus for an internal combustion engine according to the present invention, it is possible to suppress the deterioration of combustion associated with the introduction of EGR gas when starting to energize the step motor.

It is a schematic structure figure showing an example of an engine concerning an embodiment of the present invention. It is a block diagram which shows the control system of an engine. It is a map figure which shows the relationship between the time after energization return, and the EGR opening degree correction amount. It is a flowchart which shows an example of the reduction | decrease correction control of an EGR gas amount.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

-Engine-
FIG. 1 is a schematic configuration diagram showing an example of an engine 1 to which the present invention is applied.

  The engine (internal combustion engine) 1 of this example is a multi-cylinder gasoline engine, and includes a piston 1b that forms a combustion chamber 1a and a crankshaft 15 that is an output shaft. The piston 1b is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1b is converted into rotation of the crankshaft 15 by the connecting rod 16.

  A signal rotor 17 having a plurality of protrusions (teeth) 17 a... 17 a on the outer peripheral surface is attached to the crankshaft 15. A crank position sensor (engine speed sensor) 36 is disposed near the side of the signal rotor 17. The crank position sensor 36 is, for example, an electromagnetic pickup, and generates a pulsed signal (output pulse) corresponding to the protrusion 17a of the signal rotor 17 when the crankshaft 15 rotates.

  A spark plug 3 is disposed in the combustion chamber 1 a of the engine 1. The ignition timing of the spark plug 3 is adjusted by the igniter 4. The igniter 4 is controlled by an ECU (electronic control unit) 100 described later. A water temperature sensor 31 that detects an engine water temperature (cooling water temperature) Tw is disposed in the cylinder block 1 c of the engine 1.

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 a of the engine 1. An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1a. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1a are communicated or blocked. Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1a. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1a are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft and the exhaust camshaft to which the rotation of the crankshaft 15 is transmitted.

In the intake passage 11, an air cleaner 7, a hot-wire air flow meter 32 for detecting the intake air amount, an intake air temperature sensor 33 (incorporated in the air flow meter 32) for detecting the intake air temperature, and an intake air amount into the combustion chamber 1a An electronically controlled throttle valve 5 for adjusting the intake pressure, an intake pressure sensor 34 for detecting an intake pressure (absolute pressure) that is the pressure of the intake air, and the like are disposed. The throttle valve 5 is driven by a throttle motor 6. The opening degree of the throttle valve 5 is detected by a throttle position sensor 37. In the exhaust passage 12 of the engine 1, an O ₂ sensor 35 that detects the oxygen concentration in the exhaust gas, a three-way catalyst 8 that purifies the exhaust gas discharged to the exhaust passage 12, and the like are disposed.

  The intake passage 11 is provided with an injector (fuel injection valve) 2 for injecting fuel into a communication portion between the intake passage 11 and the combustion chamber 1a, that is, the intake port 11a. Fuel of a predetermined pressure is supplied from the fuel tank to the injector 2 by a fuel pump, and the fuel is injected into the intake passage 11. This injected fuel is mixed with intake air to form an air-fuel mixture and introduced into the combustion chamber 1a of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 1a is ignited by the spark plug 3 and burns and explodes. The piston 1b reciprocates due to combustion / explosion of the air-fuel mixture in the combustion chamber 1a, and the crankshaft 15 rotates. The operating state of the engine 1 is controlled by the ECU 100.

-EGR mechanism-
Further, in the engine 1, a part of the exhaust gas (EGR gas) discharged to the exhaust passage 12 is recirculated to the intake passage 11 and supplied again to the combustion chamber 1a, thereby reducing the combustion temperature, thereby generating NOx. An EGR mechanism 20 is provided that reduces the pumping loss by opening the throttle valve 5 to reduce the amount and to generate the same torque as compared with the case where the EGR gas is not recirculated. The EGR mechanism 20 is introduced into the intake passage 11 from the exhaust passage 12, the EGR passage 21 connecting the intake passage 11 and the exhaust passage 12, the EGR cooler 22 for cooling the EGR gas passing through the EGR passage 21. An EGR valve device 23 that adjusts the amount of EGR gas that is generated, and an EGR gas temperature sensor 24 that detects the temperature of the EGR gas are provided.

  The EGR passage 21 branches from the exhaust passage 12 upstream of the three-way catalyst 8 and is connected to the EGR valve device 23. The second passage 21b connects the EGR valve device 23 and the EGR cooler 22 to each other. And a third passage 21c extending from the EGR cooler 22 and branchingly connected to the intake passage 11 downstream of the throttle valve 5.

  The EGR valve device 23 includes an EGR valve 25, a step motor 26, an aluminum motor housing 27 that houses the step motor 26, and a support 28 that supports the EGR valve 25. In addition to the above, the EGR valve device 23 includes a spring or the like for biasing the EGR valve 25, but is not shown here for convenience.

  The motor housing 27 is formed with an exhaust gas inlet 27a communicating with the first passage 21a and an exhaust gas outlet 27b communicating with the second passage 21b.

  The step motor 26 is not shown by causing the drive circuit to pass a current through each phase winding in accordance with a pulse signal output from the ECU 100 for switching between energization and non-energization of each phase winding of the step motor 26. The rotor is configured to rotate accurately at a constant step angle. As described above, the step motor 26 is rotated by the energization controlled by the ECU 100, and thereby the motor shaft 29 on which the male screw is formed rotates.

  The EGR valve 25 has a valve body 25 a and a shaft 25 b, and the shaft 25 b is connected to a motor shaft 29 of the step motor 26 via a support body 28. The support 28 is formed with a female screw, and the motor shaft 29 of the step motor 26 is screwed to the female screw. As a result, when the motor shaft 29 rotates at a constant step angle, the support 28 and the EGR are rotated. The valve 25 is displaced in the motor shaft direction.

  In the EGR valve device 23 configured as described above, the step motor 26 is driven through the energization control by the ECU 100 to rotate the motor shaft 29, and the EGR valve 25 moves to move the valve body 25a and the valve seat of the exhaust gas outlet 27b. The opening degree of the EGR valve 25 is adjusted by changing the flow path opening area between the two. When the EGR valve 25 is opened, a part of the exhaust gas discharged to the exhaust passage 12 flows to the intake passage 11 via the EGR passage 21 and the opening degree of the EGR valve 25 is controlled to control the intake passage. The amount of exhaust gas recirculated to 11 (EGR gas amount) is controlled. The opening degree of the EGR valve 25 is based on the operating state of the engine 1 (for example, based on the intake air amount and the engine speed Ne, and for example, the engine speed Ne and the opening degree of the throttle valve 5). Controlled).

-ECU-
The ECU 100 includes a CPU 101, a ROM 102, a RAM 103, and a backup RAM 104 as shown in FIG. The ROM 102 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 101 executes arithmetic processing based on various control programs and maps stored in the ROM 102. The RAM 103 is a memory that temporarily stores calculation results of the CPU 101, data input from each sensor, and the like. The backup RAM 104 is a non-volatile memory that stores data to be saved when the engine 1 is stopped. is there. These ROM 102, CPU 101, RAM 103, and backup RAM 104 are connected to each other via a bus 107, and are connected to an external input circuit 105 and an external output circuit 106.

The external input circuit 105 of the ECU 100 includes a water temperature sensor 31, an air flow meter 32, an intake air temperature sensor 33, an intake air pressure sensor 34, an O ₂ sensor 35, a crank position sensor 36, a throttle position sensor 37, an EGR gas temperature sensor 24, and Various sensors such as a fuel pressure sensor 38 for detecting the fuel pressure of the fuel supplied to the injector 2 are connected. In addition to these, the external input circuit 105 includes an accelerator opening sensor 39, an ignition switch 40, a brake opening sensor 41 that outputs a signal corresponding to a depression amount of a brake pedal (not shown), and a wheel speed sensor 42. , And a shift position sensor 43 that outputs a signal corresponding to a shift position of a shift lever (not shown) is connected. On the other hand, to the external output circuit 106, the injector 2, the igniter 4 of the spark plug 3, the throttle motor 6 of the throttle valve 5, the step motor 26 of the EGR valve device 23, and the like are connected.

  The ECU 100 includes, based on the outputs of the various sensors described above, the engine 1 including drive control (fuel injection control) of the injector 2, ignition timing control of the spark plug 3, and drive control of the throttle motor 6 of the throttle valve 5. Perform various controls. Further, the ECU 100 controls the energization of the step motor 26 based on the energization control program stored in the ROM 102.

-Idling stop control-
In the present embodiment, when the vehicle is temporarily stopped, such as waiting for a signal at an intersection, the engine 1 is automatically stopped while the engine 1 is returned from the automatic stop state (idling stop state). It is like that.

  The ECU 100 is configured to automatically stop the engine 1 when the idling stop condition is satisfied, and to restart the engine 1 when the idling stop cancellation condition is satisfied. Specifically, when the idling stop condition is satisfied, ECU 100 stops the fuel supply from injector 2 to intake port 11a (fuel cut). On the other hand, when the idling stop cancellation condition is satisfied, the ECU 100 restarts fuel supply from the injector 2 to the intake port 11a and transmits a start control signal to a starter motor (not shown).

  The idling stop condition is, for example, that the brake pedal is depressed (detected by the brake opening sensor 41) and the wheel speed sensor 42 detects that the ignition signal from the ignition switch 40 is ON. The vehicle speed V calculated from the wheel speed is “0 km / h”. The idling stop condition may include, for example, that the accelerator opening degree ACC is “0%” (detected by the accelerator opening degree sensor 39).

  On the other hand, the idling stop cancellation condition is, for example, that the brake pedal depressing release operation (detected by the brake opening sensor 41) is performed in a state where the idling stop condition is satisfied and the engine 1 is automatically stopped. included. Note that the idling stop cancellation condition may include, for example, that the D position is selected by the operation of the shift lever (detected by the shift position sensor 43).

-EGR gas amount reduction correction control-
In the present embodiment, as described above, the ECU 100 controls the energization of the step motor 26, whereby the opening degree of the EGR valve 25 is adjusted, and the EGR gas amount is controlled. The ECU 100 automatically stops the engine 1 when the idling stop condition is satisfied. However, if the energization of the step motor 26 is continued even though the engine 1 is stopped, the power consumption increases and the fuel consumption deteriorates. Will be invited. Therefore, the ECU 100 is configured to cut off the power supply to the step motor 26 not only when the engine is stopped due to ignition off but also when the engine is automatically stopped due to idling stop.

  On the other hand, the ECU 100 is configured to start energization of the step motor 26 so as to adjust the opening degree of the EGR valve 25 based on the operating state of the engine 1 at the start of EGR gas introduction. Specifically, the ECU 100 starts energization to the step motor 26 when the engine water temperature Tw becomes equal to or higher than a predetermined temperature and the introduction of EGR gas is started, for example, at the time of cold start after the engine is stopped due to ignition off. To do. For example, when the engine is restarted from the idling stop state, the ECU 100 starts energizing the step motor 26 when the engine is restarted.

  However, if the energization cut to the step motor 26 is performed when the engine is stopped or automatically stopped, the following problems may occur. That is, when the step motor 26 is energized, the temperature of the motor housing 27 rises and the motor housing 27 extends in the motor shaft direction and the like. On the other hand, when the step motor 26 is de-energized, the temperature of the motor housing 27 decreases. Then, the motor housing 27 contracts in the motor axial direction or the like. On the other hand, since the EGR valve 25 is made of a material having a low expansion rate, even when the temperature of the motor housing 27 changes, the deformation amount (expansion / contraction) is small. For this reason, when the motor housing 27 extends in the motor axial direction, the valve body 25a and the valve seat of the exhaust gas outlet 27b are in close contact with each other, and the EGR valve 25 is difficult to open. On the other hand, when the motor housing 27 is contracted in the motor axial direction, the zero point of the step motor 26 may be displaced in a direction in which the EGR valve 25 is easily opened.

  Further, the ECU 100 controls the opening degree of the EGR valve 25 based on the operating state of the engine 1 based on the warm time (a state in which the motor housing 27 is at a high temperature). Therefore, if the opening degree of the EGR valve 25 is controlled while the motor housing 27 is contracted due to the power cut, the EGR valve 25 opens quickly, so that the amount of EGR gas recirculated to the intake passage 11 increases unexpectedly. In addition, there is a possibility that combustion may deteriorate due to the introduction of a large amount of EGR gas.

  Therefore, the ECU (EGR valve control device) 100, when starting introduction of EGR gas, if the elapsed time after the start of energization to the step motor 26 (hereinafter also referred to as the time after energization return) tr is short, the energization return. Compared with the case where the later time tr is long, the reduction correction amount of the EGR gas amount is increased.

Specifically, the ROM102 of ECU 100, as shown in FIG. 3, map to correspond to the EGR opening correction amount D _A the after power recovery time tr are stored. Then, the ECU 100 obtains the time tr after the return of energization by counting the elapsed time after the start of energization simultaneously with the start of energization of the step motor 26 at the start of introduction of EGR gas. Then, ECU 100 calculates the EGR opening correction amount D _A based on the obtained after power recovery time tr and the map and. Then, ECU 100 from the target EGR opening Et corresponding to the target EGR gas amount determined in accordance with the operating condition of the engine 1, the calculated EGR opening correction amount D _A subtraction was corrected target EGR opening degree E And the opening degree of the EGR valve 25 is controlled so as to coincide with the corrected target EGR opening degree E.

As shown in FIG. 3, according to the EGR opening correction amount D _A, together if after power recovery time tr is short is set to be larger, after power recovery time tr is long, EGR opening correction amount The initial value _DAI is set to decrease stepwise. Therefore, immediately after the start of energization in which the amount of contraction of the motor housing 27 is large, the EGR gas amount is corrected to decrease by the large EGR opening correction amount D _A (EGR opening correction amount initial value D _AI ). It is possible to suppress the deterioration of combustion accompanying the introduction of. On the other hand, when the temperature of the motor housing 27 rises after a certain period of time after the start of energization and the contraction amount of the motor housing 27 decreases, the EGR gas amount is corrected to decrease by the small EGR opening correction amount D _A. The amount of EGR gas can be made appropriate.

Here, and EGR opening correction amount initial value D _AI at the start of energization (after power recovery time tr = 0), or stepwise decrease in any proportion of the EGR opening correction amount D _A is experiments Can be set empirically.

For example, when the EGR valve device 23 is hot because the temperature of the engine room is high, or when the engine housing 27 is restarted immediately after the engine is automatically stopped due to idling stop, the motor housing 27 is not contracted (step motor 26 0 points, when the EGR valve 25 is not displaced in the direction of easy opening) may be set not the EGR gas amount of weight loss correction using the EGR opening correction amount D _a.

-EGR gas amount reduction correction control routine-
Next, the procedure of the EGR gas amount reduction correction control according to the present embodiment will be described with reference to the flowchart of FIG.

  First, in step S1, the energization to the step motor 26 that has been cut due to the engine stop by ignition off or the automatic engine stop by idling stop is restored. In the case of a cold start after the engine is stopped due to the ignition off, the engine water temperature Tw detected by the water temperature sensor 31 is equal to or higher than a predetermined temperature, or the engine is restarted from the idling stop state. The time when the engine is restarted is the energization return timing.

Next, in step S2, the ECU 100 acquires the time tr after energization return by counting the elapsed time after the start of energization. In step S3, the ECU 100 is based on the time tr after energization return and the map shown in FIG. Te to calculate the EGR opening correction amount D _a.

In the next step S4, the ECU 100 calculates a target EGR gas amount based on, for example, the intake air amount detected by the air flow meter 32 and the engine speed Ne calculated based on the output pulse of the crank position sensor 36, the EGR opening correction amount D _a from the target EGR opening Et corresponding to the target EGR gas amount is subtracted to calculate the corrected target EGR opening degree E.

  In the next step S5, the ECU 100 adjusts the opening of the EGR valve 25 by controlling the energization of the step motor 26 so that the corrected target EGR opening E calculated in step S4 is obtained. As a result, an appropriate amount of EGR gas taking into account the amount of contraction of the motor housing 27 is supplied again to the combustion chamber 1a.

In the next step S6, ECU 100 is, EGR opening correction amount D _A calculated in the step S3 determines whether a 0. This in the case determination is NO in step S6, the process returns to step S2, and continues the EGR gas amount of weight loss correction using the EGR opening correction amount D _A. On the other hand, if the determination in step S6 is YES, the END is performed as it is, and thereafter, the opening of the EGR valve 25 is adjusted based on the target EGR opening Et corresponding to the target EGR gas amount.

(Other embodiments)
The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

  In the above embodiment, the case where the present invention is applied to a multi-cylinder gasoline engine has been described. However, the present invention is not limited thereto, and the present invention may be applied to, for example, a diesel engine.

  The EGR valve device 23 in the above embodiment is an example, and the EGR gas amount is controlled by energizing the step motor 26, and the zero point of the step motor 26 is set in a direction in which the EGR valve 25 is easily opened by the energization cut. The present invention can be applied to any structure that can be displaced.

  As described above, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  According to the present invention, when the energization of the step motor is started, the deterioration of combustion accompanying the introduction of the EGR gas can be suppressed. Therefore, the internal combustion engine provided with the EGR valve device that controls the EGR gas amount by energizing the step motor. It is extremely beneficial to apply to.

1 engine (internal combustion engine)
11 Intake passage 12 Exhaust passage 21 EGR passage 23 EGR valve device 26 Step motor 100 ECU (EGR valve control device)

Claims (1)

The present invention is applied to an internal combustion engine provided with an EGR valve device that is provided in an EGR passage that connects an exhaust passage and an intake passage of the internal combustion engine, and controls the amount of EGR gas flowing from the exhaust passage to the intake passage by energizing a step motor. An EGR valve control device for an internal combustion engine,
While the internal combustion engine is stopped, the energization to the step motor is cut, while the energization to the step motor is started at the start of introduction of EGR gas,
When the elapsed time after the start of energization to the step motor is short, the EGR gas amount reduction correction amount is increased and the EGR gas amount is increased as the elapsed time becomes longer than when the elapsed time is long. An EGR valve control apparatus for an internal combustion engine, characterized in that the amount of reduction correction of the engine is reduced stepwise .

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