JP4419913B2 - Brake device for vehicle - Google Patents

Description

  The present invention relates to a vehicle brake device that maintains a stopped state.

  In general, in brake-by-wire, in which the brake hydraulic circuit is driven and controlled by an electronic control unit, when the brake-by-wire is executed, the hydraulic pressure corresponding to the driver's brake operation is closed with the hydraulic pressure path from the master cylinder to the wheel cylinder closed. Is transmitted to the wheel cylinder by a pump or the like, and the hydraulic pressure path from the master cylinder to the stroke simulator is opened to produce pedal stroke and pedal reaction force. On the other hand, when the brake-by-wire is not executed, the hydraulic pressure path from the master cylinder to the stroke simulator is closed, and the hydraulic pressure path from the master cylinder to the wheel cylinder is opened. Is transmitted to the cylinder.

In the brake-by-wire as described above, even when the ignition switch is OFF, when the driver performs a brake operation, the electronic control device is activated to apply a braking force according to the pedal stroke and the master cylinder pressure. Some have generated and executed brake-by-wire (see Patent Document 1).
JP 2005-35387 A

However, if a quick brake operation is performed with the ignition switch OFF, the master cylinder pressure increases by the stroke of the brake pedal, then the hydraulic pressure path to the wheel cylinder is closed and the hydraulic pressure to the stroke simulator is The route is released. At this time, the stroke amount of the brake pedal does not decrease, but the master cylinder pressure decreases. Therefore, if braking force is generated according to the pedal stroke and master cylinder pressure in this state, the braking force also decreases. Therefore, there is a possibility that the braking force desired by the driver cannot be obtained.
Accordingly, the present invention has been made paying attention to the above-described problem, and an object thereof is to provide a vehicle brake device that can generate a braking force desired by a driver.

In order to solve the above-described problems, a vehicle brake device according to the present invention includes a master cylinder that generates a fluid pressure corresponding to a driver's brake operation, and a wheel cylinder that can generate a braking force by the fluid pressure of the master cylinder. A first valve capable of closing the flow path between the master cylinder and the wheel cylinder, a stroke simulator capable of absorbing the fluid pressure of the master cylinder, and a second valve capable of opening the flow path between the master cylinder and the stroke simulator. With a valve,
The braking force control means is activated under a predetermined condition, calculates the target braking force according to the stroke amount of the brake operation by the driver and the fluid pressure of the master cylinder, closes the first valve, and In controlling the braking force of the vehicle by transmitting the fluid pressure corresponding to the target braking force to the wheel cylinder with the valve opened,
When it is determined that the relationship between the stroke amount of the brake operation and the fluid pressure of the master cylinder deviates from the predetermined relationship, and the fluid pressure of the master cylinder with respect to the stroke amount of the brake operation decreases relatively, only the stroke amount of the brake operation The target braking force is calculated accordingly.
That is, when the braking force control means is activated in a state where the first valve is opened, the second valve is closed, and the driver is performing a braking operation, only the stroke amount of the braking operation is obtained. The target braking force is calculated accordingly.

  According to the vehicle brake device of the present invention, when the relationship between the stroke amount of the brake operation and the fluid pressure of the master cylinder deviates from the predetermined relationship, the fluid pressure of the master cylinder with respect to the stroke amount of the brake operation relatively decreases. When the determination is made, it is possible to generate a braking force desired by the driver by calculating the target braking force according to only the stroke amount of the brake operation.

  That is, when the braking force control means is activated in a state where the first valve is opened, the second valve is closed, and the brake operation is performed by the driver, the hydraulic pressure path to the wheel cylinder When the valve is closed by the first valve and the hydraulic pressure path to the stroke simulator is opened by the second valve, the fluid pressure of the master cylinder is reduced even though the stroke amount of the brake operation is not reduced. However, in this case, the braking force as desired by the driver can be generated by calculating the target braking force according to only the stroke amount of the brake operation.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a brake system. When a pedal depression force is input to one end of the brake pedal 1 that is braked by the driver, the brake pedal 1 rotates around the other end to advance the push rod 3 of the master cylinder 2.
The master cylinder 2 converts the pedal depression force input via the push rod 3 into two systems of hydraulic pressure, transmits the primary side to the rear left and right wheel cylinders 6RL and 6RR, and transmits the secondary side to the front left and right wheel cylinders 6FL. -It is transmitting to 6FR. Here, a front / rear split system in which the brake system is divided by front and rear wheels is adopted, but of course, a diagonal split system in which the brake system is divided by front left and rear right and front right and rear left may be adopted.

Each of the wheel cylinders 6FL to 6RR is incorporated in a disc brake that presses a disc rotor with a brake pad to generate a braking force, or a drum brake that generates a braking force by pressing a brake shoe against the inner peripheral surface of the brake drum. Yes.
In the hydraulic system on the primary side, the gate valve 7r (corresponding to the “first valve”) that can close the flow path between the master cylinder 2 and the wheel cylinders 6RL and 6RR, and the gate valve 7r and the wheel cylinder 6RL (6RR) Inlet valve 8RL (8RR) capable of closing the flow path between them, and an outlet valve capable of opening the flow path communicating between inlet valve 8RL (8RR) and wheel cylinder 6RL (6RR) and reservoir tank 2a of master cylinder 2 9RL (9RR), and a pump 10r having a suction side communicating between the outlet valves 9RL and 9RR and the reservoir tank 2a and a discharge side communicating between the gate valve 7r and the inlet valves 8RL and 8RR.

  Here, the gate valve 7r, the inlet valves 8RL and 8RR, and the outlet valves 9RL and 9RR are two-port, two-position switching, spring-offset electromagnetic operation valves, respectively. The gate valve 7r and the inlet valves 8RL and 8RR are The flow path is opened at the non-excited normal position, and the outlet valves 9RL and 9RR are configured to close the flow path at the non-excited normal position. Since each valve only needs to be able to open and close the flow path, the gate valve 7r and the inlet valves 8RL and 8RR open the flow path at the excited offset position, and the outlet valves 9RL and 9RR are excited. The flow path may be closed at the position.

Further, the pump 10r is constituted by a positive displacement pump such as a gear pump or a piston pump that can ensure a substantially constant discharge amount regardless of the load pressure.
With the above configuration, the reservoir valve tank 8r (8RR) and the outlet valve 9RL (9RR) are kept in a non-excited normal position, the gate valve 7r is excited and closed, and the reservoir tank is driven by driving the pump 10r. The brake fluid of 2a is sucked and the hydraulic pressure of the wheel cylinder 6RL (6RR) can be increased by the discharge pressure.

Further, with the outlet valve 9RL (9RR) in the non-excited normal position, the gate valve 7r and the inlet valve 8RL (8RR) are energized to close each, so that the reservoir tank 2a and the wheel tank 6RL (6RR) Each flow path to the pump 10r can be blocked, and the hydraulic pressure of the wheel cylinder 6RL (6RR) can be maintained.
Further, the outlet valve 9RL (9RR) is excited and opened, and the gate valve 7r and the inlet valve 8RL (8RR) are excited to close each other, whereby the hydraulic pressure of the wheel cylinder 6RL (6RR) is reduced to the reservoir tank 2a. And can be decompressed.

Furthermore, the hydraulic pressure from the master cylinder 2 is transmitted to the wheel cylinder 6RL (6RR) by setting all of the gate valve 7r, the inlet valve 8RL (8RR), and the outlet valve 9RL (9RR) to the non-excited normal position. Become a normal brake.
The secondary hydraulic system is also provided with the same gate valve 7f, inlet valves 8FL and 8FR, outlet valves 9FL and 9FR, and pump 10f as the primary side, and each operation is the same as the primary side. Detailed description thereof will be omitted.

  A stroke simulator 11 is connected between the master cylinder 2 and the gate valve 7r on the primary side. The stroke simulator 11 is composed of a spring-type accumulator having a compression spring 11a interposed between the bottom of the cylinder and a piston. When the compression spring 11a elastically contracts as the hydraulic pressure increases, Cylinder pressure can be absorbed.

  A gate valve 12 (corresponding to a “second valve”) is interposed between the master cylinder 2 and the stroke simulator 11. This gate valve 12 is a two-port, two-position switching, spring offset type electromagnetically operated valve, and is configured to close the flow path at a non-excited normal position. Since the gate valve 12 only needs to be able to open and close the flow path, the flow path may be closed at the excited offset position.

The above-described gate valves 7f and 7r, inlet valves 8FL to 8RR, outlet valves 9FL to 9RR, pumps 10f and 10r, and gate valve 12 are driven and controlled by the controller 13.
When executing the brake-by-wire, the controller 13 closes the gate valves 7f and 7r and opens the gate valve 12, and supplies the hydraulic pressure corresponding to the brake operation amount of the driver to the wheel cylinders 6FL to 6f by the pumps 10f and 10r. 6RR is transmitted to control the braking force of the vehicle. At this time, since the hydraulic pressure generated in the master cylinder is absorbed by the stroke simulator 11, an appropriate pedal stroke and pedal reaction force can be produced with respect to the driver's brake operation.

On the other hand, when brake-by-wire is not executed due to fail-safe such as a pump failure, the hydraulic pressure from the master cylinder 2 is transmitted to the wheel cylinders 6FL to 6RR by opening the gate valves 7f and 7r and closing the gate valve 12. And normal braking.
The controller 13 has a master cylinder pressure P detected by the pressure sensor 14, a stroke amount S of the brake pedal 1 detected by the stroke sensor 15, and an operation signal of an ignition switch (hereinafter referred to as IGN switch) 16. Entered.

Next, the braking force control process executed by the controller 13 will be described based on the flowchart of FIG.
The controller 13 is activated when the IGN switch 16 is turned on, or when the brake pedal 1 is depressed even when the IGN switch 16 is turned off, and the braking force control process of FIG. 2 is performed for a predetermined time (for example, 10 msec). This is executed as timer interrupt processing for each time.

First, in step S1, it is determined whether or not it is a start-up time. If it is not the time of starting, it will transfer to step S6 mentioned later. On the other hand, when it is a start time, the process proceeds to step S2.
In step S2, it is determined whether or not the stroke amount S of the brake pedal 1 is greater than zero. When the determination result is S = 0, the process proceeds to step S3. On the other hand, when the determination result is S> 0, the process proceeds to step S4.

In step S3, the control flag f is reset to “0”, and then the process proceeds to step S6 described later.
In step S4, it is determined whether or not the gate valve 7r is opened and the gate valve 12 is closed. Here, when the gate valve 7r is closed and the gate valve 12 is opened, the process proceeds to step S3 described above. On the other hand, when the gate valve 7r is opened and the gate valve 12 is closed, the process proceeds to step S5.

In step S5, the control flag f is set to “1”, and then the process proceeds to step S6.
In step S6, it is determined whether or not the stroke amount S of the brake pedal 1 is greater than zero. When the determination result is S = 0, the process proceeds to step S12 described later. On the other hand, when the determination result is S> 0, the process proceeds to step S7.
In step S7, a target braking force Fp ^* corresponding to the master cylinder pressure P is calculated with reference to a control map as shown in the figure. The control map, the horizontal axis of the master cylinder pressure P, the vertical axis represents the target braking force Fp ^*, in proportion to the increase of the master cylinder pressure P target braking force Fp ^* is set to increase.

In the following step S8, a target braking force Fs ^* corresponding to the stroke amount S of the brake pedal 1 is calculated with reference to a control map as shown in the figure. The control map, the horizontal stroke of the shaft S, the vertical axis represents the target braking force Fs ^*, together with target braking force Fs ^* is increased according to the increase of the stroke amount S, the target braking force with respect to the stroke amount S Fs ^* of The rate of increase is set to gradually increase.

In the subsequent step S9, the control map as shown in the figure is referred to, and the contribution α (0 <α <1) of Fp ^* to the final target braking force F ^* is determined as the control flag f, the master cylinder pressure P, and the like. Calculate according to In this control map, the horizontal axis represents the master cylinder pressure P, the vertical axis represents the contribution α, and when the control flag is f = 0, the contribution α increases as the master cylinder pressure P increases, The increase rate of the contribution α to the master cylinder pressure P is set to be gradually reduced. On the other hand, when the control flag is f = 1, the contribution degree α is set to maintain 0.

In the subsequent step S10, as shown in the following equation (1), the final target braking force F ^* is calculated according to the target braking force Fp ^* , the target braking force Fs ^*, and the contribution degree α.
F ^* = α · Fp ^* + (1−α) Fs ^* (1)
In subsequent step S11, the gate valves 7f and 7r, the inlet valves 8FL to 8RR, the outlet valves 9FL to 9RR, the pumps 10f and 10r, and the gate valve 12 are driven and controlled so that the target braking force F ^* is achieved. Even if the target braking force F ^* is 0, the gate valve 7r is closed and the gate valve 12 is opened in preparation for the subsequent brake operation.
On the other hand, in step S12, the control flag f is reset to “0”.
In the subsequent step S13, the target braking force F ^{* is set} to 0, and then the process proceeds to step S11.
From the above, the braking force control process of FIG. 2 corresponds to the “braking force control means”.

Next, the operation and effects of the one embodiment will be described.
Now, it is assumed that the driver depresses the brake pedal 1 even when the IGN switch 16 is turned on or the IGN switch 16 is turned off. Thereby, the controller 13 is started and the braking force control process of FIG. 2 is started.
If the driver does not depress the brake pedal 1 at the time of activation (step S2 is “No”), the target braking force F ^* is 0 (step S13), but the gate valve 7r is closed, and The gate valve 12 is opened to stand by for a subsequent brake operation.

Thereafter, when the driver depresses the brake pedal 1 (determination in step S6 is “Yes”), the control flag f is reset to “0”, so that it corresponds to the pedal stroke S and the master cylinder pressure P. The inlet valves 8FL to 8RR, the outlet valves 9FL to 9RR, and the pumps 10f and 10r are driven and controlled so that the target braking force F ^* is generated (steps S7 to S11). By performing the braking force control with the two parameters of the pedal stroke S and the master cylinder pressure P, it is possible to execute a highly accurate brake-by-wire with excellent controllability.

At this time, the pedal stroke S and the master cylinder pressure P are in a predetermined relationship in which the master cylinder pressure P is determined according to the pedal stroke S due to the structure of the stroke simulator 11, so as shown in FIG. The target braking force F ^* is also determined according to S.
On the other hand, it is assumed that the driver has already depressed the brake pedal 1 at the time of activation. In this case, with the gate valve 7r opened and the gate valve 12 closed, the brake pedal 1 is stroked and the master cylinder pressure is generated.

  In this state, when the gate valve 7r is closed and the gate valve 12 is opened, as shown in FIG. 4, the stroke amount S of the brake pedal 1 does not decrease, but the master cylinder pressure P is absorbed by the stroke simulator 11. It will decline. That is, the relationship between the pedal stroke S and the master cylinder pressure P deviates from a predetermined relationship when the pedal operation is started with the gate valve 7r closed and the gate valve 12 opened, and the master cylinder with respect to the stroke amount S The pressure P decreases relatively.

Accordingly, when the target braking force F ^* corresponding to the pedal stroke S and the master cylinder pressure P is calculated in this state, the target braking force F ^* also decreases as the master cylinder pressure P decreases as shown in FIG. Therefore, there is a possibility that the braking force desired by the driver cannot be obtained.
Therefore, in this embodiment, when it is determined that the master cylinder pressure P is relatively decreased with respect to the stroke amount S, that is, in a state where the gate valve 7r is opened, the gate valve 12 is closed, and the brake operation is performed. When the controller 13 is activated (Steps S1, S2, and S4 are determined as “Yes”, respectively), the control flag f is set to “1” (Step S5), and the target braking force F ^* corresponding to only the pedal stroke S is set ^. Is calculated (steps S7 to S10).

Thus, even when the brake pedal 1 is depressed in a state where the gate valve 7r is opened and the gate valve 12 is closed, and then the gate valve 7r is closed and the gate valve 12 is opened, FIG. As shown, the braking force desired by the driver can be generated.
Further, if cranking and brake operation are performed at the same time, it is considered that the gate valve 7r / 12 is delayed in opening and closing due to the voltage drop, and the relative decrease in the master cylinder pressure P with respect to the stroke amount S is conspicuous. Therefore, as shown in FIG. 7, for example, when parking on a hill, when cranking and quick brake depression are performed at the same time, and then the parking brake is released, the braking force is insufficient. May be invited. However, the vehicle can be prevented from slipping by reliably generating the braking force desired by the driver as in the present embodiment.

In addition, the target braking force F ^* is calculated according to the stroke amount S and the master cylinder pressure P (see FIG. 3), and the target braking force F ^* is calculated only according to the stroke amount S (see FIG. 3). 2), the relationship between the stroke amount S and the target braking force F ^* is substantially the same. Therefore, since both braking force characteristics are also approximated, the driver does not feel uncomfortable.
Further, referring to a control map showing the relationship between the stroke amount S and the target braking force Fs ^*, since the calculated target braking force Fs ^* from the stroke amount S, which can be easily calculated.

Then, after the brake operation is released (determination in step S6 is “No”), the control flag f is reset to “0” (step S13), and according to the pedal stroke S and the master cylinder pressure P. A target braking force F ^* is calculated. Thereby, it is excellent in controllability and a highly accurate brake-by-wire can be performed.
In the above-described embodiment, the hydraulic brake using the hydraulic pressure as the transmission medium is employed. However, the present invention is not limited to this, and an air brake using the compressed air as the transmission medium may be employed. .

  Moreover, in said one Embodiment, although the brake-by-wire using a fluid pressure is performed, it is not limited to this. Since it is only necessary to be able to control the braking force for the brake-by-wire, an electric brake that clamps the disc rotor with the brake pad or presses the brake shoe against the inner peripheral surface of the brake drum by controlling the driving of the electric actuator. Any brake that can be electronically controlled may be used.

It is a schematic block diagram of a brake system. It is the flowchart which showed the braking force control process. It is the graph which showed the relationship between the pedal stroke S and the target braking force F ^* . 3 is a graph showing the relationship between pedal stroke S and master cylinder pressure P. It is a graph explaining the subject of a prior art. It is a time chart explaining the operation effect of the present invention. It is a time chart explaining the other effect in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brake pedal 2 Master cylinder 3 Push rod 6FL-6RR Wheel cylinder 7f-7r Gate valve 8FL-8RR Inlet valve 9FL-9RR Outlet valve 10f / 10r Pump 11 Stroke simulator 11a Compression spring 12 Gate valve 13 Controller 14 Pressure sensor 15 Stroke sensor 16 Ignition switch

Claims (4)

A master cylinder that generates a fluid pressure according to the driver's brake operation, a wheel cylinder that can generate a braking force by the fluid pressure of the master cylinder, and a flow path that can close a flow path between the master cylinder and the wheel cylinder. 1 valve, a stroke simulator capable of absorbing the fluid pressure of the master cylinder, a second valve capable of opening a flow path between the master cylinder and the stroke simulator,
It is activated under a predetermined condition, calculates the target braking force according to the stroke amount of the brake operation by the driver and the fluid pressure of the master cylinder, closes the first valve and opens the second valve In a vehicle brake device comprising: a braking force control means for controlling a braking force of a vehicle by transmitting a fluid pressure corresponding to the target braking force to the wheel cylinder in a state where
When the braking force control means determines that the relationship between the stroke amount of the brake operation and the fluid pressure of the master cylinder deviates from a predetermined relationship, the fluid pressure of the master cylinder with respect to the stroke amount of the brake operation decreases relatively In addition, the target braking force is calculated according to only the stroke amount of the brake operation. Before SL braking force control means, said first valve is opened, the second valve is closed, when starting in a state where the brake operation is started and by the driver, the stroke of the brake operation 2. The vehicle brake according to claim 1, wherein a relationship between the master cylinder and the fluid pressure of the master cylinder deviates from a predetermined relationship, and the fluid pressure of the master cylinder with respect to a stroke amount of a brake operation is relatively decreased. apparatus.   The braking force control means refers to a control map showing a relationship between a stroke amount of a brake operation by a driver and the target braking force, and calculates the target braking force from the stroke amount of the brake operation. The vehicle brake device according to claim 1 or 2.   The braking force control means calculates the target braking force according to the stroke amount of the braking operation by the driver and the fluid pressure of the master cylinder after the braking operation by the driver is released. The brake device for vehicles as described in any one of Claims 1-3.

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