Vehicle control device

Abstract

To provide a vehicle control device that enables stop and start control to be actuated even when a tread force of a brake pedal is insufficient and even by a driver having a small tread force.SOLUTION: When a brake pedal 66 is stepped on and a vehicle 10 is in a stopped state, an electric control device 80 can increase a wheel cylinder brake hydraulic pressure Ph for controlling a brake force of a wheel brake 60. As a result, even when a tread force of the brake pedal 66 is insufficient and even by a driver having a small tread force, a brake force Bf of the wheel brake 60 for maintaining the stop state of the vehicle 10 is secured and stop and start control (idling stop control) can be actuated.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that performs stop-and-start control (idling stop control) that temporarily stops the engine when the vehicle comes to a stop. [Background technology]

[0002] Some vehicles are known to perform stop-and-start control (idling stop control), which temporarily stops the engine when the vehicle stops (hereinafter referred to as "idling stop") and restarts the engine when a recovery condition is met, including releasing the brake pedal or depressing the accelerator pedal. To prevent the vehicle from moving when the engine is restarted from an idling stop state and to prevent the vehicle from rolling back while in idling stop, a threshold is set for hydraulic pressure controlling the braking force of the brakes. The vehicle will not transition to an idling stop state unless the hydraulic pressure is equal to or greater than the threshold, i.e., unless the brake pedal is depressed until the hydraulic pressure reaches or exceeds the threshold. Patent Document 1 discloses a technology for appropriately setting the threshold according to the idling speed at the time of engine restart. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-344665 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, to transition to the idle stop state, the brake pedal must be depressed with a certain amount of force to raise the hydraulic pressure above the threshold. Therefore, if the brake pedal force is insufficient or the driver does not apply enough force, the stop-and-start control (idle stop control) cannot be activated.

[0005] The present invention was made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can activate stop-and-start control (idling stop control) even when the brake pedal force is insufficient or the driver has weak pedal force. [Means for solving the problem]

[0006] The gist of the present invention is (a) a control device for a vehicle that performs stop-and-start control, which temporarily stops the engine when the vehicle stops and restarts the engine when a recovery condition is met, including releasing the brake pedal or depressing the accelerator pedal, and (b) when the brake pedal is depressed and the vehicle is stopped, increases the hydraulic pressure that controls the braking force of the brakes. [Effects of the Invention]

[0007] The vehicle control device of the present invention increases the hydraulic pressure that controls the braking force of the brakes when the brake pedal is depressed and the vehicle is stopped. As a result, even if the brake pedal force is insufficient or the driver applies a weak brake pedal force, the braking force of the brakes is ensured to keep the vehicle stopped, and the stop-and-start control (idling stop control) can be activated. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating control functions and main parts of a control system for various controls in the vehicle. [Figure 2] 4 is an example of a flowchart illustrating a control operation of the electronic control device shown in FIG. 1 during stop-and-start control. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0010] Fig. 1 is a diagram illustrating a schematic configuration of a vehicle 10 to which the present invention is applied, and also illustrating the main parts of control functions for various controls in the vehicle 10. In Fig. 1, the vehicle 10 includes an engine 12 as a power source, wheels 14, and a power transmission device 16 provided in a power transmission path between the engine 12 and the wheels 14. The power transmission device 16 includes a torque converter 20, an automatic transmission 22, and the like, housed within a case 18. The power transmission device 16 also includes a propeller shaft 26 connected to a transmission output shaft 24, which is an output rotating member of the automatic transmission 22, a differential 28 connected to the propeller shaft 26, left and right drive shafts 30 connected to the differential 28, and the like.

[0011] The output torque of the engine 12 is controlled by an engine control device 40 provided in the vehicle 10 being controlled by an electronic control device 80, which will be described later.

[0012] The torque converter 20 is disposed in a power transmission path between the engine 12 and the automatic transmission 22, and is connected to the engine 12 via a crankshaft 32. The torque converter 20 includes a pump wheel 20p, a turbine wheel 20t, etc., and further includes a lock-up clutch (hereinafter referred to as an LU clutch) 36 that connects the pump wheel 20p and the turbine wheel 20t.

[0013] The automatic transmission 22 is connected to the engine 12 via the torque converter 20 and the input shaft 34. The automatic transmission 22 is a known planetary gear type stepped transmission that can select from a plurality of gear stages POSsh and that includes, for example, a plurality of sets of planetary gear devices and a plurality of hydraulic engagement devices CB such as clutches and brakes.

[0014] The vehicle 10 is further equipped with a wheel brake 60. The wheel brake 60 applies a braking force Bf to the wheel 14 according to a wheel cylinder braking hydraulic pressure Ph which is a composite of a master cylinder braking hydraulic pressure Pmc supplied from a brake master cylinder 62 (described later) and an automatic brake braking hydraulic pressure Pav supplied from an automatic brake control device 64 (described later). The wheel brake 60 corresponds to the "brake" in this invention, and the wheel cylinder braking hydraulic pressure Ph corresponds to the "hydraulic pressure" in this invention.

[0015] The brake master cylinder 62 generates a master cylinder braking hydraulic pressure Pmc corresponding to the depression force of the brake pedal 66 applied by the driver, and supplies the hydraulic pressure Pmc to the wheel brakes 60. The brake pedal 66 may use the depression amount instead of the depression force.

[0016] The automatic brake control device 64 generates automatic brake hydraulic pressure Pav to obtain braking force Bf required for ABS control, traction control, VSC control, hill hold control, cruise control, etc., which are performed when braking, starting, or turning the vehicle 10 on a low μ road, keeping the vehicle stopped on a slope, or maintaining a safe distance from a vehicle ahead, and supplies the generated hydraulic pressure to the wheel brakes 60. The automatic brake control device 64 is controlled by an electronic control device 80, which will be described later, to control the automatic brake hydraulic pressure Pav.

[0017] The vehicle 10 is equipped with an electronic control device 80 as a controller of the vehicle 10. Various signals based on detected values ​​from an engine rotation speed sensor 70, an output rotation speed sensor 72, an accelerator opening sensor 74, a brake master cylinder pressure sensor 76, and the like, which are provided in the vehicle 10, are respectively supplied to the electronic control device 80 (for example, engine rotation speed Ne (rpm), AT output rotation speed No (rpm) corresponding to vehicle speed V (Km / h), accelerator opening pap (%) indicating the amount of depression of accelerator pedal 68, master cylinder braking oil pressure Pmc (MPa) indicating the depression force of brake pedal 66, etc.).

[0018] The electronic control device 80 outputs various command signals (for example, an engine control command signal Se for controlling the engine 12, a brake control command signal Sb for controlling the automatic brake hydraulic pressure Pav of the automatic brake control device 64, a hydraulic control command signal Sat for controlling the operating state of the engagement device CB, a hydraulic control command signal Slu for controlling the operating state of the LU clutch 36, etc.) to the engine control device 40, the automatic brake control device 64, the hydraulic control circuit 50, etc., which are provided in the vehicle 10.

[0019] The electronic control unit 80 functionally comprises an engine control unit 82, a gear change control unit 84, a brake control unit 86, an LU clutch control unit 88, and an S&S control unit 90.

[0020] The engine control unit 82 controls the engine 12. The engine control unit 82 calculates a required driving force F by applying the accelerator opening pap and the vehicle speed V to a predetermined driving force map. The engine control unit 82 outputs an engine control command signal Se to the engine control device 40 to realize the required driving force F.

[0021] The shift control unit 84 executes shift control of the automatic transmission 22. For example, the shift control unit 84 determines the gear position POSsh of the automatic transmission 22 using, for example, a shift map, which is a predetermined relationship. The shift control unit 84 outputs a hydraulic control command signal Sat to the hydraulic control circuit 50 to switch the operating state of the engagement device CB so as to achieve the determined gear position POSsh.

[0022] The brake control unit 86 controls the braking force when ABS control, traction control, VSC control, hill hold control, cruise control, etc. When performing the various controls described above, the brake control unit 86 calculates an automatic brake hydraulic pressure Pav that realizes the required braking force Bf, and outputs a brake control command signal Sb to the automatic brake control device 64 so that the calculated automatic brake hydraulic pressure Pav is supplied from the automatic brake control device 64 to the wheel brakes 60.

[0023] The LU clutch control unit 88 applies the vehicle driving state represented by the vehicle speed V and accelerator opening pap to a predetermined lockup operation region map, and outputs a hydraulic control command signal Slu to the hydraulic control circuit 50 so that the LU clutch 36 is brought into a disengaged state (released state or engaged state).

[0024] The S&S control unit 90 performs stop and start (hereinafter referred to as S&S) control, which temporarily stops the engine 12 when the vehicle 10 stops, and restarts the engine 12 when a restoration condition is met, including the release of the brake pedal 66 and the depression of the accelerator pedal 68. In this embodiment, the temporary stop of the engine 12 resulting from the stop of the vehicle 10 is referred to as "idling stop." Furthermore, S&S control is synonymous with idling stop control.

[0025] The S&S control unit 90 operates the S&S control, i.e., transitions to an idle-stop state, on the conditions that the vehicle 10 is stopped and that the wheel cylinder braking hydraulic pressure Ph synthesized in the wheel brakes 60 is equal to or greater than the threshold value Ps. In other words, control is performed so that transition to the idle-stop state is not performed unless the wheel cylinder braking hydraulic pressure Ph is equal to or greater than the threshold value Ps. The threshold value Ps is set in advance by design or experimentation as a value that ensures that the braking force Bf of the wheel brakes 60 is sufficient to prevent the vehicle 10 from moving when the engine 12 is restarted from the idle-stop state and that prevents the vehicle 10 from rolling down during the idle-stop state.

[0026] In the conventional example, when the vehicle 10 is stopped, the wheel cylinder braking hydraulic pressure Ph is the same as the master cylinder braking hydraulic pressure Pmc supplied from the brake master cylinder 62 (Ph = Pmc). Therefore, in order to transition to an idle-stop state, the master cylinder braking hydraulic pressure Pmc needs to be equal to or greater than the threshold value Ps, and the brake pedal 66 needs to be depressed with a certain amount of force or more. Therefore, there has been a problem in that the S&S control cannot be activated when the brake pedal 66 is not depressed with sufficient force or when the driver does not exert enough force.

[0027] In this embodiment, even if the depression force on the brake pedal 66 is insufficient, the S&S control is activated by the control operation described later in Fig. 2. Fig. 2 is an example of a flowchart illustrating the control operation performed by the S&S control unit 90, which is functionally provided in the electronic control unit 80, when the S&S control is activated, i.e., when transitioning to idling stop. Hereinafter, the control operation will be described in accordance with the processing steps in Fig. 2.

[0028] First, in step S10 (hereinafter, "step" will be omitted), it is determined whether or not other S&S control activation conditions are met, other than the master cylinder braking oil pressure Pmc (determined in S20) and the vehicle speed V (determined in S30). For example, it is confirmed whether or not the S&S control can be activated, such as whether the temperature of the engine 12 or the charge amount of the battery is equal to or greater than a predetermined value. If the determination in S10 is negative, this routine is terminated.

[0029] If the determination in S10 is affirmative, then in S20 it is determined whether the master cylinder braking oil pressure Pmc is greater than 0, i.e., whether the brake pedal 66 is depressed. If the determination in S20 is negative, this routine is terminated.

[0030] If the determination in S20 is positive, i.e., if the brake pedal 66 is depressed, then in S30 it is determined whether the vehicle speed V is 0, i.e., whether the vehicle 10 is stopped. If the determination in S30 is negative, this routine is terminated.

[0031] If the determination in S30 is positive, i.e., if the vehicle 10 is stopped, the wheel cylinder braking hydraulic pressure Ph is increased in S40. The wheel cylinder braking hydraulic pressure Ph is increased by increasing the automatic brake braking hydraulic pressure Pav. For example, an automatic brake braking hydraulic pressure Pav is calculated so that the wheel cylinder braking hydraulic pressure Ph, which is a combination of the master cylinder braking hydraulic pressure Pmc and the automatic brake braking hydraulic pressure Pav, is equal to or greater than the threshold value Ps, and a brake control command signal Sb is output to the automatic brake control device 64 to achieve this automatic brake braking hydraulic pressure Pav. This ensures that the braking force Bf of the wheel brakes 60 is sufficient to keep the vehicle 10 stopped even during an idle stop or when the engine 12 is restarted. Then, in S50, an engine control command signal Se is output to the engine control device 40, causing the vehicle 10 to transition to an idle stop state, and this routine is terminated.

[0032] According to the electronic control device 80 of this embodiment, when the brake pedal 66 is depressed and the vehicle 10 is stopped, the wheel cylinder braking hydraulic pressure Ph that controls the braking force of the wheel brake 60 is increased. As a result, even when the depression force on the brake pedal 66 is insufficient or the driver applies a weak depression force, the braking force Bf of the wheel brake 60 that keeps the vehicle 10 stopped is ensured, and S&S control can be activated.

[0033] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0034] For example, in the above-described embodiment, the vehicle 10 is a vehicle powered only by the engine 12, but the present invention can also be applied to a hybrid vehicle that has both the engine 12 and an electric motor as power sources.

[0035] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0036] 10: Vehicle 12: Engine 60: Wheel brake (brake) 66: Brake pedal 68: Accelerator pedal 80: Electronic control unit (control unit) Ph: Wheel cylinder braking hydraulic pressure (hydraulic pressure)

Claims

[Claim 1] A control device for a vehicle that performs stop-and-start control, which temporarily stops an engine when the vehicle stops and restarts the engine when a restoration condition including releasing a brake pedal or depressing an accelerator pedal is satisfied, When the brake pedal is depressed and the vehicle is stopped, the hydraulic pressure that controls the braking force of the brake is increased. A vehicle control device characterized by:

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