JP2014238101A - Vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve, in a vehicle control device, running safety and drivability by satisfactorily performing the management of negative pressure for braking regardless of the running state of a vehicle.SOLUTION: There are provided an engine 11, a hydraulic brake device 31 for acting brake force to a vehicle in accordance with the operation of a driver, and a brake booster 34 for assisting the brake operation of the driver by negative pressure which is generated by driving of the engine 11. An ECU 21 can automatically stop the engine 11 in accordance with the operation state of the vehicle, can automatically start the engine 11 when, during automatic stop of the engine, the negative pressure of the brake booster 34 becomes lower than a predetermined negative pressure determination value which is set beforehand, and can change the negative pressure determination value in accordance with a change of vehicle speed of the vehicle during automatic stop of the engine 11.

Description

  The present invention relates to a vehicle control device.

  Various types of vehicle control devices have been proposed that enable an eco-run operation by automatically stopping the engine under predetermined driving conditions in the vehicle. In this eco-run operation, the fuel supply is stopped, so that the fuel consumption can be improved.

  As a conventional engine control device that enables such an eco-run operation, for example, there is one described in Patent Document 1 below. The engine automatic stop / start control device described in Patent Document 1 can automatically start the engine when the negative pressure value of the brake booster using the intake negative pressure of the engine as a negative pressure source decreases during the automatic stop of the engine. When the predetermined condition is satisfied, the engine speed is increased and the engine is automatically started. Specifically, when the driver tries to brake suddenly or performs a sudden steering operation, the engine is automatically started by increasing the rotational speed when the traveling road surface changes from a flat road to a downhill road. .

JP 2006-200370 A

  When the vehicle is equipped with a brake booster to which engine intake negative pressure is supplied, the negative pressure of the brake booster decreases when the engine is stopped and the eco-run operation is performed. Then, after restarting the engine, the brake operation of the driver cannot be sufficiently assisted by the brake booster, which may cause discomfort. In the conventional engine automatic stop / start control device described above, when the brake operation is performed such that the booster negative pressure is greatly consumed while the engine is stopped, that is, sudden brake operation, sudden handle operation, and downhill traveling. Sometimes, the engine automatic start determination value is changed, the engine speed is increased to automatically start the engine, and the booster negative pressure is recovered early.

  In this conventional engine automatic stop / start control device, when the vehicle is running in an eco-run with the engine stopped, negative pressure management of the brake booster when various operations are performed by the driver is sufficiently possible. However, when the vehicle reaches a downhill road and the speed increases, the driver applies a large braking force or a pumping brake. At this time, if the booster negative pressure is not sufficient, the brake operation by the driver cannot be fully assisted. Moreover, in the conventional engine automatic stop / start control device, although the booster negative pressure is managed when the vehicle is traveling on the downhill road, it is necessary to define the downhill road, that is, to set the inclination angle of the road surface. The control becomes complicated.

  The present invention has been made in view of the above-described circumstances, and improves vehicle safety and drivability by improving negative pressure management for braking regardless of the vehicle traveling state. An object is to provide a control device.

  In order to solve the above-described problems and achieve the object, the present invention provides a driving source for a vehicle, a braking device for applying a braking force to the vehicle, and a braking operation of a driver by a negative pressure generated by driving the driving source. A braking assist device for assisting the vehicle, an automatic stop means capable of automatically stopping the drive source in accordance with the driving state of the vehicle, and the negative pressure of the brake assist device becomes a predetermined condition during the automatic stop of the drive source. There are also provided automatic starting means for automatically starting the drive source, and condition changing means for changing the condition in accordance with a change in the vehicle speed of the vehicle since the drive source was automatically stopped.

  In the vehicle control apparatus, it is preferable that the condition changing unit changes the condition based on a change amount of a current vehicle speed with respect to a vehicle speed when the drive source is automatically stopped.

  The vehicle control device according to the present invention is configured so that the drive source can be automatically started when the negative pressure for braking becomes a predetermined condition during the automatic stop of the drive source. Since this condition can be changed according to the change in the vehicle speed of the vehicle, it is possible to improve the driving safety and improve the drivability by properly managing the brake negative pressure regardless of the driving state of the vehicle. There is an effect that can be.

FIG. 1 is a block diagram showing a vehicle control apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart showing a flow of processing of engine restart control by the vehicle control device of the present embodiment. FIG. 3 is a schematic diagram showing changes in the running state of the vehicle. FIG. 4 is a graph showing a correction coefficient of a negative pressure determination value with respect to an increase amount of kinetic energy.

  Hereinafter, an embodiment of a vehicle control device according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment, and when there are a plurality of embodiments, it includes those configured by combining the embodiments.

  FIG. 1 is a block diagram illustrating a vehicle control device according to an embodiment of the present invention, FIG. 2 is a flowchart illustrating a flow of processing of engine restart control by the vehicle control device of the present embodiment, and FIG. FIG. 4 is a graph showing a correction coefficient of a negative pressure determination value with respect to an increase amount of kinetic energy.

  In the vehicle control apparatus of this embodiment, as shown in FIG. 1, an engine 11 as a power source has a torque converter 12 connected to a crankshaft, and a stepped automatic transmission on a drive shaft 13 of the torque converter 12. 14 are connected. A propeller shaft 15 is connected to the automatic transmission 14, left and right drive shafts 17 are connected to the propeller shaft 15 via a differential gear 16, and left and right drive wheels 18 are connected to the drive shaft 17.

  Therefore, when the engine 11 is driven, the driving force is output from the crankshaft and input to the input shaft of the automatic transmission 14 via the torque converter 12, where the speed is reduced to a predetermined gear ratio. Then, the driving force after deceleration is output from the output shaft of the automatic transmission 14 to the propeller shaft 15 and transmitted from the propeller shaft 15 to the left and right drive shafts 17 via the differential gear 16 to drive the left and right drive wheels 18. Can rotate.

  A clutch 19 is interposed between the torque converter 12 and the automatic transmission 14. The clutch 19 has an actuator 20, and the actuator 20 can disable transmission of driving force and braking force between the engine 11 side and the driving wheel 18 side.

  An engine control unit (ECU) 21 is mounted on the vehicle, and the ECU 21 can control driving of the engine 11. That is, an air flow sensor 22 that measures the intake air amount, an accelerator position sensor 24 that detects the amount of depression of the accelerator pedal 23 (accelerator opening), a throttle position sensor 25 that detects the throttle opening in the electronic throttle device, and the rotation of the engine 11 An engine speed sensor 26 for detecting the number is provided. The ECU 21 controls the fuel injection amount by the injector, the fuel injection timing, the ignition timing by the spark plug, and the like based on the detection results detected by the sensors 22, 24, 25, and 26.

  The automatic transmission 14 is hydraulically controlled by a transmission hydraulic pressure control unit 27. The ECU 21 can perform shift control by controlling the transmission hydraulic pressure control unit 27 to hydraulically control the automatic transmission 14. That is, an input shaft rotational speed sensor 28 for detecting the input shaft rotational speed and a shift position sensor 30 for detecting a shift position by the shift lever device 29 operated by the driver are provided. The ECU 21 controls the transmission hydraulic pressure control unit 27 based on the detection results detected by the sensors 24, 28, and 30 and controls the automatic transmission 14 to control the transmission timing and the like. In this case, the ECU 21 controls the driving force of the vehicle by controlling the engine 11 and the automatic transmission 14.

  The vehicle is provided with a hydraulic brake device (braking device) 31 corresponding to the drive wheel 18. The ECU 21 can perform brake (braking) control by controlling the brake hydraulic pressure control unit 32 and hydraulically controlling the hydraulic brake device 31. In this case, the brake pedal 33 is connected to a brake booster (brake booster) 34. The brake booster 34 is operated by the supplied negative pressure, and the driver operates the brake using the negative pressure. Assist. The brake booster 34 has a negative pressure chamber (not shown) connected to the intake pipe of the engine 11, and a predetermined negative pressure in the negative pressure chamber is accumulated. A brake pedal stroke sensor 35 that detects the amount of depression of the brake pedal 33 (brake pedal stroke) and a negative pressure sensor 36 that detects negative pressure acting on the negative pressure chamber of the brake booster 34 are provided. Based on the detection result detected by the brake pedal stroke sensor 35, the ECU 21 controls the brake hydraulic pressure control unit 32 and hydraulically controls the hydraulic brake device 31, whereby a predetermined braking force (braking oil pressure) is applied to the drive wheels 18. ).

  In the present embodiment, an engine (internal combustion engine) 11 is applied as a drive source of a vehicle, and a hydraulic brake device 31 is applied as a brake device that applies a braking force to the vehicle in accordance with a driver's operation, and is generated by driving the drive source. The brake booster 34 is applied as a braking assist device that assists the driver's braking operation with the negative pressure. The ECU 21 can automatically stop the engine 11 in accordance with the driving state of the vehicle and can be automatically started. Here, the ECU 21 functions as an automatic stop unit and an automatic start unit.

  Specifically, the ECU 21 automatically stops the engine 11 when an engine automatic stop condition (for example, the accelerator pedal 23 by the driver is not depressed for a predetermined time) is satisfied during traveling of the vehicle. Further, the ECU 21 automatically starts the engine 11 when an engine automatic start condition (for example, depression of the accelerator pedal 23 by the driver) is satisfied during the traveling of the vehicle in which the engine 11 is automatically stopped. When the ECU 21 automatically stops the engine 11, fuel supply to the engine 11 and ignition are stopped and the clutch 19 is disengaged. In this way, the inertial running (free run) in which the engine 11 is automatically stopped and the vehicle is driven by inertia (inertial force), and the inertial running is stopped by automatically starting the engine 11 from this inertial running and returning the vehicle. When driving force is not required even during traveling, practical fuel efficiency can be earned by stopping the engine 11 and allowing the vehicle to coast.

  Further, the ECU 21 automatically starts the engine 11 when the negative pressure acting on the negative pressure chamber of the brake booster 34 falls below a predetermined negative pressure determination value (condition) set in advance while the engine 11 is automatically stopped. When the engine 11 is stopped by inertia running, the negative pressure in the negative pressure chamber of the brake booster 34 decreases when the driver depresses the brake pedal 33 several times. In this case, because the engine 11 is stopped, negative pressure does not act on the negative pressure chamber from the intake pipe of the engine 11. Therefore, if the negative pressure in the negative pressure chamber of the brake booster 34 is reduced, the brake booster 34 may not be able to assist the driver's brake operation due to the negative pressure. Therefore, the ECU 21 automatically starts the engine 11 when the negative pressure in the negative pressure chamber of the brake booster 34 falls below the negative pressure determination value while the engine 11 is automatically stopped, and a predetermined negative pressure is secured in the negative pressure chamber. I try to do it.

  In the present embodiment, the ECU 21 changes the negative pressure determination value (condition) according to the kinetic energy of the vehicle that travels while the engine 11 is automatically stopped. Here, the ECU 21 functions as a condition changing unit. In this case, the ECU 21 calculates kinetic energy based on the weight and speed of the vehicle. In this case, a vehicle speed sensor 37 that detects the traveling speed of the vehicle is provided, and the ECU 21 determines the vehicle speed based on the weight of the vehicle obtained by adding the weight of the occupant to the weight of the vehicle body and the vehicle speed detected by the vehicle speed sensor 37. Calculate kinetic energy.

  Further, the ECU 21 changes the negative pressure determination value based on the current increase in the vehicle kinetic energy relative to the vehicle kinetic energy when the engine 11 is automatically stopped. The ECU 21 changes the negative pressure determination value according to the amount of negative pressure necessary for decelerating or stopping the vehicle running while the engine 11 is automatically stopped.

  Further, the brake pedal stroke sensor 35 is applied as a braking operation amount detection means for detecting a braking operation amount by the driver when the vehicle travels with the engine automatically stopped, and the ECU 21 detects the braking operation detected by the brake pedal stroke sensor 35. The negative pressure determination value is changed in accordance with the amount, specifically, the integrated value of the number of braking operations by the driver, the integrated value of the brake pedal stroke, or the like.

  That is, the ECU 21 automatically stops the engine 11 when the engine automatic stop condition is satisfied while the vehicle is traveling, and the vehicle travels inertially. At this time, when the road on which the vehicle travels is a downhill road, since the engine 11 is stopped in the vehicle, the engine brake does not act and the vehicle speed increases. Then, the driver depresses the brake pedal 33 strongly or depresses the brake pedal 33 many times to pump the brake pedal 33 in order to decrease the vehicle speed. In this case, since the driver performs a braking operation larger than usual and the depression operation of the brake pedal 33, the brake booster 34 requires a large negative pressure.

  However, as described above, when the vehicle is coasting, the engine 11 is stopped. Therefore, negative pressure cannot be supplied to the negative pressure chamber of the brake booster 34, and negative pressure is reduced. As a result, the brake booster 34 may not be able to sufficiently assist the driver's brake operation even if the vehicle speed increases when the vehicle traveling inertially travels downhill. Therefore, the ECU 21 changes the negative pressure determination value so as to increase according to the kinetic energy of the vehicle running while the engine 11 is automatically stopped, automatically starts the engine 11 earlier than usual, and causes a large negative pressure in the negative pressure chamber. Pressure is secured.

  Further, the ECU 21 determines a negative pressure determination value according to an integrated value of the number of braking operations, an integrated value of the brake pedal stroke, or the like when the driver performs many braking operations in a vehicle that travels while the engine 11 is automatically stopped. The engine 11 is automatically started earlier than usual so that a large negative pressure is secured in the negative pressure chamber.

  When the engine 11 is automatically stopped, changing the ECU 21 so that the negative pressure determination value becomes higher according to the kinetic energy of the traveling vehicle means that the vehicle speed at this time is maintained and the vehicle speed is constant. The negative pressure determination value is changed according to the braking force necessary to achieve this.

  Hereinafter, the control by the vehicle control apparatus of this embodiment will be described in detail with reference to the flowchart of FIG.

  In the vehicle control apparatus of the present embodiment, as shown in FIG. 2, in step S11, the ECU 21 determines whether or not the engine 11 is in an automatic stop state in the traveling vehicle. Here, if it is determined that the engine 11 is not in the automatic stop state, this routine is exited without doing anything. On the other hand, if it is determined that the engine 11 is in the automatic stop state, the current kinetic energy of the vehicle is calculated in step S12. In this case, the ECU 21 calculates the initial kinetic energy of the vehicle when the engine 11 automatically stops and starts inertial running, and stores this initial kinetic energy. In addition, the ECU 21 constantly calculates the kinetic energy of the vehicle that is coasting with the engine 11 automatically stopped.

Here, a method for calculating the kinetic energy of the vehicle will be described. When the mass (weight) of the vehicle is m and the speed of the vehicle is v, the kinetic energy K of the vehicle can be obtained by the following formula.
K = (1/2) mv ²
In this case, the mass (weight) m of the vehicle may be obtained by measuring the weight of the vehicle body in advance and adding the weight for the number of passengers. The vehicle speed v may be the detection result of the vehicle speed sensor 37.

In step S13, the ECU 21 determines whether the kinetic energy of the vehicle has increased. As shown in FIG. 3, when the vehicle 11a travels on a flat road 201 and the engine 11 automatically stops and reaches coasting, the initial kinetic energy at this time is calculated and stored. When the vehicle 100b that is traveling inertial reaches the downhill road 202, the speed of the vehicle 100b increases and the kinetic energy increases. That is, the increase k of the kinetic energy can be obtained by the following formula. Here, v1 is a vehicle speed when the vehicle starts coasting, and v2 is a vehicle speed when traveling on a downhill road at present.
k = (1/2) × m × (v2 ² −v1 ² )

For example, if m is 1500 kg, v1 is 30 km / h (8.3 m / s), and v2 is 500 km / h (13.9 m / s), the kinetic energy increase k1 at this time is as follows.
k1 = (1/2) × 1500 × (13.9 ² −8.3 ² ) = 93240

  Returning to FIG. 2, if it is determined in step S13 that the kinetic energy of the vehicle has not increased, the process proceeds to step S14, where the current negative pressure determination value is maintained and it is determined that the kinetic energy of the vehicle has increased. Then, the process proceeds to step S15, and the negative pressure determination value is changed. In this case, as shown in FIG. 4, the ECU 21 stores in advance a graph (map) representing a correction coefficient of the negative pressure determination value with respect to the increase amount of kinetic energy, and the calculated increase amount k (k1) of kinetic energy. ) To obtain a correction coefficient. From this map, if the increase k of kinetic energy is 0 (or 0 or less), the correction coefficient is 1. As described above, if the amount of increase in kinetic energy k1 = 93240, the correction coefficient is 1.3. That is, in step S15, the ECU 21 sets a new negative pressure determination value (for example, 65 kPa) by multiplying the current negative pressure determination value (for example, 50 kPa) by the correction coefficient 1.3.

  Returning to FIG. 2, in step S <b> 16, the ECU 21 determines whether an automatic start condition (restart condition) of the engine 11 is satisfied. Here, if it is determined that the automatic start condition of the engine 11 is not satisfied, this routine is exited without doing anything. On the other hand, if it is determined that the automatic start condition of the engine 11 is established, the ECU 21 automatically starts (restarts) the engine 11 in step S17. That is, the ECU 21 starts fuel supply and ignition to the engine 11 and puts the clutch 19 in a connected state.

  In the present embodiment, a negative pressure determination value is adopted as the automatic start condition of the engine 11, and the ECU 21 determines that the current negative pressure in the negative pressure chamber of the brake booster 34 detected by the negative pressure sensor 36 is a negative pressure determination. It is determined whether or not the pressure has fallen below the value. If it is determined that the current negative pressure has dropped below the negative pressure determination value, the engine 11 is automatically started. In this case, since the negative pressure determination value is changed to a higher value when the vehicle traveling on inertia reaches a downhill road, the engine 11 is automatically started earlier than when traveling on a flat road, and the negative pressure of the brake booster 34 is reduced. A large negative pressure is secured in the pressure chamber, and the brake booster 34 can sufficiently assist the driver's braking operation.

  At this time, the ECU 21 may change the negative pressure determination value higher according to the amount of brake operation by the driver while the engine 11 is automatically stopped and the vehicle is coasting.

  As described above, in the vehicle control device of the present embodiment, the engine 11, the hydraulic brake device 31 that applies a braking force to the vehicle according to the operation of the driver, and the negative pressure generated by driving the engine 11, A brake booster 34 for assisting the braking operation is provided, and the ECU 21 can automatically stop the engine 11 according to the driving state of the vehicle, and the negative pressure of the brake booster 34 is set in advance during the automatic engine stop. The engine 11 can be automatically started when the negative pressure determination value falls below the negative pressure determination value, and the negative pressure determination value can be changed according to the kinetic energy of the vehicle that travels while the engine 11 is automatically stopped.

  Therefore, by changing the negative pressure determination value according to the kinetic energy of the vehicle that travels while the engine 11 is automatically stopped, the negative pressure of the brake booster 34 can be maintained at the optimum value according to the traveling state of the vehicle. Therefore, it is possible to improve the driving safety by improving the negative pressure management for braking regardless of the driving state of the vehicle, and to improve the drivability by enabling the brake booster 34 to perform a good brake assist. Can do.

  In the vehicle control device of the present embodiment, the ECU 21 calculates kinetic energy based on the weight and speed of the vehicle. Therefore, by calculating the kinetic energy based on the weight and speed of the vehicle, the kinetic energy can be easily obtained with high accuracy, and the complication of the apparatus can be suppressed.

  Specifically, the ECU 21 changes the negative pressure determination value based on the current increase in vehicle kinetic energy relative to the vehicle kinetic energy when the engine 11 is automatically stopped. In this case, the negative pressure determination value is changed according to the amount of negative pressure necessary to decelerate or stop the vehicle traveling while the engine 11 is automatically stopped. Accordingly, the negative pressure determination value is changed to a high level based on the increase in kinetic energy, and when the engine 11 automatically stops and the vehicle speed increases, the engine 11 is easily started automatically, and sufficient braking is always performed. The assist force, that is, the braking force can be ensured to decelerate or stop the vehicle.

  Further, in the vehicle control device of the present embodiment, when the engine 11 automatically stops and the vehicle travels inertially, the ECU 21 changes the negative pressure determination value to a high value according to the brake operation amount by the driver. Accordingly, when the driver frequently depresses the brake pedal 33, the degree of decrease in the negative pressure of the brake booster 34 is large. At this time, the engine 11 can be easily started automatically by changing the negative pressure determination value to a higher value. Thus, a sufficient brake assist force, that is, a braking force for decelerating or stopping the vehicle can be ensured at all times.

  In addition, the vehicle control device of the present invention assists the driver's braking operation with the engine 11, the hydraulic brake device 31 that applies a braking force to the vehicle according to the driver's operation, and the negative pressure generated by driving the engine 11. The brake booster 34 is provided, and the ECU 21 can automatically stop the engine 11 according to the driving state of the vehicle, and a predetermined negative pressure determination value in which the negative pressure of the brake booster 34 is set in advance during the automatic stop of the engine. When the engine 11 is further lowered, the engine 11 can be automatically started, and the negative pressure determination value can be changed in accordance with the braking force necessary to maintain the speed of the vehicle that travels while the engine 11 is automatically stopped.

  Therefore, by changing the negative pressure determination value according to the braking force necessary to maintain the speed of the vehicle that travels while the engine 11 is automatically stopped, the negative pressure of the brake booster 34 is reduced according to the traveling state of the vehicle. It is possible to maintain the optimum value, and it is possible to improve the driving safety by performing the negative pressure management for braking well regardless of the driving state of the vehicle, and also to provide a good brake assist by the brake booster 34. The drivability can be improved as possible.

  In the above-described embodiment, the torque converter 12 is connected to the engine 11 as a power source via the clutch 19, and the stepped automatic transmission 14 is connected to the torque converter 12. It is not limited to. For example, instead of the clutch 19, the torque converter 12, and the automatic transmission 14, a clutch and a manual transmission may be used, or instead of the stepped automatic transmission 14, a continuously variable transmission (CVT) or a dual clutch transmission (DCT) ) May be applied. In this embodiment, the brake device is the hydraulic brake device 31 and is operated by the driver operating the brake pedal 33. However, the ECU 21 may be an automatic brake device that operates the hydraulic brake device 31 according to the running state of the vehicle. Good.

  As described above, the vehicle control device according to the present invention changes the condition for automatically starting the drive source in accordance with the change in the vehicle speed of the vehicle since the drive source automatically stopped, thereby Regardless of this, the negative pressure management for braking is performed satisfactorily to improve running safety and drivability, which is useful for a device that controls the running of a vehicle.

11 Engine (drive source)
14 Automatic transmission 19 Clutch 21 ECU (automatic stopping means, automatic starting means, condition changing means)
31 Hydraulic brake device (braking device)
32 Brake hydraulic control unit 33 Brake pedal 34 Brake booster (braking assist device)
35 Brake pedal stroke sensor (braking operation amount detection means)
36 Negative pressure sensor 37 Vehicle speed sensor

Claims (2)

  A vehicle drive source, a braking device that applies a braking force to the vehicle, a braking assistance device that assists a driver's braking operation by negative pressure generated by driving the drive source, and the drive source according to a driving state of the vehicle Automatic stopping means capable of automatically stopping the driving source, automatic starting means for automatically starting the driving source when the negative pressure of the braking assist device reaches a predetermined condition during automatic stopping of the driving source, and the driving source And a condition changing means for changing the condition according to a change in the vehicle speed of the vehicle since the automatic stop. The vehicle control device according to claim 1, wherein the condition changing unit changes the condition based on a change amount of a current vehicle speed with respect to a vehicle speed when the drive source automatically stops.

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