JP2019156234A - Vehicle control device - Google Patents

Abstract

To provide a vehicle control device capable of suppressing the occurrence of an engine stall which is caused by a delay in the release of a lockup clutch.SOLUTION: A vehicle control device performs fuel cut of the engine during inertial running of the vehicle, locks up an engine output shaft and a transmission input shaft by a lockup clutch, and releases the lockup clutch when brake pressure is equal to or greater than a threshold value. The vehicle control device increases the release speed of the lockup clutch as the brake pressure is higher and the rotational speed of the transmission input shaft is lower.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a vehicle control device.

  Patent Document 1 discloses that in a vehicle control device, a lockup clutch is released when a predetermined operating condition such as a sudden brake operation is established during lockup.

JP 2009-236235 A

  However, in the vehicle control device disclosed in Patent Document 1, the occurrence of engine stall is suppressed by determining a sudden brake based on the brake pressure and releasing the lockup clutch. There is no mention about. For this reason, if the release speed is uniform, the lock-up clutch may not be released in time depending on the vehicle state, which may cause engine stall.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle control device capable of suppressing the occurrence of an engine stall without releasing the lockup clutch in time. is there.

  In order to solve the above-described problems and achieve the object, a vehicle control apparatus according to the present invention includes a fuel cut of an engine when the vehicle is coasting, and lockup of an engine output shaft and a transmission input shaft by a lockup clutch. In the vehicle control device that releases the lock-up clutch when the brake pressure is equal to or higher than a threshold value, the stronger the brake pressure and the lower the rotational speed of the transmission input shaft, It is characterized by increasing the release speed.

  In the vehicle control device according to the present invention, the stronger the brake pressure, the stronger the driver's intention to decelerate, and the lower the rotational speed of the transmission input shaft, the more likely the engine stalls. Change the release speed of the lockup clutch from the speed. As a result, the vehicle control apparatus according to the present invention suppresses the occurrence of the engine stall without releasing the lockup clutch in time by increasing the release speed of the lockup clutch as the engine stalls easily. There is an effect that can be done.

Drawing 1 is a mimetic diagram showing the composition of the control device of vehicles concerning an embodiment. FIG. 2 is a flowchart illustrating an example of lock-up clutch sudden release control performed by the control device according to the embodiment. FIG. 3 is a time chart for brake ON / OFF, master cylinder pressure, brake force, tire rotation speed, and tire rotation change rate ΔNO, showing an outline of the sudden stop determination performed by the control device according to the embodiment. is there. FIG. 4 is a graph showing a change in lockup hydraulic pressure in the lockup clutch sudden release control. FIG. 5 is a graph showing a change in the lockup hydraulic pressure in the lockup clutch normal release control.

  Hereinafter, an embodiment of a vehicle control apparatus according to the present invention will be described. In addition, this invention is not limited by this embodiment.

  Drawing 1 is a mimetic diagram showing composition of control device 1 of vehicle 100 concerning an embodiment. As shown in FIG. 1, the control device 1 according to the embodiment is mounted on a vehicle 100. The vehicle 100 includes an engine 101, a torque converter 102, an automatic transmission 103, a differential gear 104, and drive wheels 105 as main components.

  The engine 101 converts the combustion energy of the fuel into a rotational motion and outputs it to the torque converter 102. The torque converter 102 includes a pump impeller 102a, a turbine runner 102b, and a lockup clutch 102c. The pump impeller 102 a is connected to the engine 101 and rotates integrally with the rotation shaft of the engine 101. The turbine runner 102 b is connected to the input shaft of the automatic transmission 103 and rotates integrally with the input shaft of the automatic transmission 103.

  The lock-up clutch 102 c is a friction engagement type clutch device provided between the rotation shaft of the engine 101 and the input shaft of the automatic transmission 103. The engaged lockup clutch 102 c mechanically connects the engine 101 and the automatic transmission 103. Thereby, the pump impeller 102a and the turbine runner 102b rotate integrally. On the other hand, when the lock-up clutch 102c is in the released state, the pump impeller 102a and the turbine runner 102b transmit torque via the fluid.

  A differential gear 104 is connected to the output shaft side of the automatic transmission 103, and left and right drive wheels 105 are connected to the differential gear 104 via left and right drive shafts. When the engine 101 is driven, the driving force is output from the crankshaft and input to the input shaft of the automatic transmission 103 via the torque converter 102, where a predetermined shift is performed. Thereafter, the driving force is output from the output shaft of the automatic transmission 103 and transmitted to the left and right drive shafts via the differential gear 104. As a result, the left and right drive wheels 105 are driven to rotate.

  The automatic transmission 103 includes a C1 clutch (engine disconnecting clutch) 103a. The C1 clutch 103a is arranged in series with the lockup clutch 102c in the power transmission path between the engine 101 and the drive wheel 105. The C1 clutch 103a includes an engine side engaging element connected to the engine 101 side and a driving wheel side engaging element connected to the driving wheel 105 side.

  The C1 clutch 103a connects the power transmission path between the engine 101 and the drive wheel 105 by engaging the engine side engagement element and the drive wheel side engagement element. On the other hand, the C1 clutch 103a blocks the power transmission path between the engine 101 and the drive wheel 105 by opening the engine side engagement element and the drive wheel side engagement element. In other words, the C1 clutch 103a functions as a switching device that switches the state of the power transmission path between the engine 101 and the drive wheel 105 between a state where power transmission is possible and a state where power transmission is impossible. To do.

  The control device 1 includes an accelerator opening sensor 2, a brake pedal stroke sensor 3, a master cylinder pressure sensor 4, an engine speed sensor 5, a turbine speed sensor 6, an output shaft speed sensor 7, a vehicle speed sensor 8, and an ECU ( Electronic Control Unit) 9 is provided.

  The accelerator opening sensor 2 detects the accelerator opening according to the amount of depression of the accelerator pedal by the driver, and outputs an electric signal indicating the detected accelerator opening to the ECU 9. The brake pedal stroke sensor 3 detects the stroke amount of the brake pedal according to the depression amount of the brake pedal by the driver, and outputs an electric signal indicating the detected stroke amount to the ECU 9. The master cylinder pressure sensor 4 detects the master cylinder pressure (brake pressure) and outputs an electric signal indicating the detected master cylinder pressure (brake pressure) to the ECU 9. The engine speed sensor 5 detects the speed of the engine 101 and outputs an electrical signal indicating the detected speed of the engine 101 to the ECU 9. The turbine rotation speed sensor 6 detects the rotation speed of the turbine runner 102b, and outputs an electric signal indicating the detected turbine rotation speed NT, which is the rotation speed of the turbine runner 102b, to the ECU 9. The output shaft rotational speed sensor 7 detects the rotational speed of the output shaft of the automatic transmission 103 and outputs an electrical signal indicating the detected rotational speed of the output shaft to the ECU 9. The vehicle speed sensor 8 detects the speed (vehicle speed) of the vehicle 100 and outputs an electric signal indicating the detected vehicle speed to the ECU 9. Further, the ECU 9 calculates the tire rotation speed from the vehicle speed and the effective radius of the drive wheel 105.

  The ECU 9 is physically an electronic circuit mainly composed of a known microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an input / output interface. The function of the ECU 9 is to load an application program held in the ROM into the RAM and execute it by the CPU, thereby operating the controlled object under the control of the CPU and reading out data in the RAM or ROM. This is realized by writing.

  The ECU 9 controls the engine 101, the torque converter 102, and the automatic transmission 103. Specifically, the ECU 9 detects the operating state of the engine 101 and controls the fuel injection amount and injection timing by the injector, the ignition timing by the spark plug, and the like. Further, the ECU 9 controls the hydraulic mechanism of the automatic transmission 103 based on the detection result of the vehicle speed and the accelerator opening. Thereby, the automatic transmission 103 is shifted.

  The ECU 9 executes free-run control when a predetermined free-run start condition is satisfied while the vehicle 100 is traveling. Free-run control is control in which the vehicle 100 travels with the drive of the engine 101 stopped and the C1 clutch 103a opened. By executing the free-run control, the inertial travel distance of the vehicle 100 can be extended and the fuel consumption can be improved. On the other hand, the ECU 9 drives the engine 101 and engages the C1 clutch 103a when the predetermined free-run return condition is satisfied during the free-run control, thereby changing the state of the vehicle 100 to the free-run control state. To return to the normal control state. In a normal control state, the vehicle 100 can be accelerated by the power of the engine 101.

  The free-run start condition is that the state where the accelerator opening detected by the accelerator opening sensor 2 is zero continues for a predetermined time or more, and the stroke amount of the brake pedal detected by the brake pedal stroke sensor 3 is zero. In addition, a plurality of conditions are included such that the vehicle speed detected by the vehicle speed sensor 8 satisfies a predetermined condition. The free-run return condition is that the accelerator opening detected by the accelerator opening sensor 2 is greater than or equal to a predetermined value, the stroke amount of the brake pedal detected by the brake pedal stroke sensor 3 is greater than or equal to a predetermined value, etc. It can be illustrated.

  The ECU 9 can execute idle-on fuel cut control (hereinafter abbreviated as fuel cut control) that temporarily reduces the fuel injection amount to the engine 101 while the vehicle 100 is traveling. The fuel cut control can be executed, for example, during coasting where the accelerator opening is zero and the engine speed is equal to or greater than a predetermined value. During the execution of the fuel cut control, the lockup clutch 102c and the C1 clutch 103a are engaged and configured to avoid engine stall.

  The fuel cut control cannot be performed when the vehicle speed is a predetermined value or less in order to avoid the occurrence of engine stall. When the vehicle speed is reduced to the predetermined value during execution of the fuel cut control, the ECU 9 resumes fuel injection to the engine 101 and returns the vehicle 100 from the fuel cut control. The ECU 9 also engages the lockup clutch 102c when the fuel cut control is performed particularly during deceleration, and opens the lockup clutch 102c when returning from the fuel cut control.

  The ECU 9 controls the hydraulic mechanism of the lockup clutch 102c based on the detection result of the vehicle speed and the accelerator opening. The engagement state of the lockup clutch 102c is controlled by adjusting the hydraulic pressure in the hydraulic mechanism, and the lockup clutch 102c is engaged or released, and further, slip control is performed with a predetermined slip amount. When the lock-up clutch 102c is slip-controlled, the pump impeller 102a and the turbine runner 102b have a rotational speed difference corresponding to the slip amount.

  FIG. 2 is a flowchart illustrating an example of lock-up clutch sudden release control performed by the control device 1 according to the embodiment.

  First, the control device 1 determines whether lock-up control is being performed (step S1). If it is determined that lock-up control is not being performed (No in step S1), the control device 1 ends a series of controls. On the other hand, when it is determined that the lockup control is being performed (Yes in step S2), the control device 1 determines that the master cylinder pressure detected by the master cylinder pressure sensor 4 is equal to or greater than a preset master cylinder pressure determination threshold value. (Step S2). If it is determined that the master cylinder pressure determination threshold value is not exceeded (No in step S2), the control device 1 repeats the process until the master cylinder pressure detected by the master cylinder pressure sensor 4 becomes equal to or greater than the master cylinder pressure determination threshold value. The determination of S2 is performed. And when it is judged that it is more than a master cylinder pressure judging threshold (it is Yes at Step S2), control device 1 starts lockup clutch sudden release control (Step S3). When the lock-up clutch 102c is released, the lock-up clutch rapid release control is terminated (step S4), and a series of control is terminated.

  FIG. 3 is a time chart for brake ON / OFF, master cylinder pressure, brake force, tire rotation speed, and tire rotation change rate ΔNO, showing an outline of the sudden stop determination performed by the control device 1 according to the embodiment. It is.

  In the control device 1 according to the embodiment, at time T1, the vehicle 100 is switched from brake OFF to brake ON, and a master cylinder pressure that is increased according to the depression amount of the brake pedal by the driver is set in advance. A sudden stop determination is made at time T2 when the master cylinder pressure determination threshold is reached, and lockup clutch sudden release control is started. As a result, the lockup clutch 102c can be suddenly released earlier than when the sudden stop determination is made at time T3 when the tire rotation change rate ΔNO reaches a preset ΔNO determination threshold. Therefore, in the control device 1 according to the embodiment, when the engine is suddenly stopped under a condition in which engine stall during fuel cut control is likely to occur, the determination of the sudden stop is made based on the master cylinder pressure instead of the tire rotation change rate ΔNO. By predicting the operation intention and suddenly releasing the lock-up clutch 102c, the occurrence of engine stall can be suppressed.

  FIG. 4 is a graph showing a change in lockup hydraulic pressure in the lockup clutch sudden release control. FIG. 5 is a graph showing a change in the lockup hydraulic pressure in the lockup clutch normal release control.

  In the control device 1 according to the embodiment, a plurality of master cylinder pressure determination threshold values are set stepwise in order to suppress the occurrence of engine stall in the panic brake and improve the drivability in a sudden stop other than the panic brake. Then, during panic braking, lockup clutch sudden release control is performed to suddenly release the lockup clutch 102c by lowering the lockup hydraulic pressure as shown in FIG. 4 to the value at the time of releasing the lockup clutch. On the other hand, during a sudden stop other than the panic brake, lockup clutch normal release control as shown in FIG. 5 is performed. In the end-time control in the lockup clutch normal release control, the sweep control is performed at a sweep rate that is variable according to the turbine speed NT and the master cylinder pressure so that the lockup hydraulic pressure approaches the value at the time of lockup clutch release. Do.

  Specifically, as shown in Table 1 below, a plurality of the sweep rates are set according to the turbine rotational speed NT and the master cylinder pressure, and the stronger the master cylinder pressure, the lower the turbine rotational speed NT. The release speed of the lockup clutch 102c is increased accordingly.

  The magnitude relationship of the sweep rate in Table 1 is (4) <(5) <(6) <(1) <(2) <(3). If the turbine speed NT is low, engine stall will occur. Since it is easy to reach, the sweep rate is relatively larger than when the turbine speed NT is high.

  In the control device 1 according to the embodiment, the higher the master cylinder pressure (brake pressure), the stronger the driver's intention to decelerate, and the lower the turbine speed NT (rotational speed of the transmission input shaft), the more likely the engine stalls. The release speed of the lockup clutch 102c is changed based on the master cylinder pressure (brake pressure) and the turbine speed NT (rotational speed of the transmission input shaft). As a result, the control device 1 according to the embodiment suppresses the engine stall and increases the release speed of the lock-up clutch 102c in a situation where the engine stall is likely to occur, thereby suppressing the occurrence of engine stall and the driver by sudden release of the lock-up clutch 102c. It is possible to achieve both suppression of deterioration of the performance.

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Accelerator opening degree sensor 3 Brake pedal stroke sensor 4 Master cylinder pressure sensor 5 Engine speed sensor 6 Turbine speed sensor 7 Output shaft speed sensor 8 Vehicle speed sensor 9 ECU
DESCRIPTION OF SYMBOLS 100 Vehicle 101 Engine 102 Torque converter 102a Pump impeller 102b Turbine runner 102c Lock-up clutch 103 Automatic transmission 104 Differential gear 105 Drive wheel

Claims (1)

In a vehicle control device that performs engine fuel cut during inertial running of a vehicle, locks up an engine output shaft and a transmission input shaft by a lock-up clutch, and releases the lock-up clutch when a brake pressure is equal to or greater than a threshold value.
The vehicle control device characterized in that the higher the brake pressure and the lower the rotational speed of the transmission input shaft, the faster the release speed of the lockup clutch.

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