JP4650282B2 - Brake device for vehicle - Google Patents

Description

The present invention relates to a vehicle brake device that performs brake-by-wire.

Patent Document 1 proposes that a target braking force is calculated based on the master cylinder pressure and the brake pedal stroke, and the braking force of the vehicle is controlled according to the target braking force. Here, the contribution degree of the master cylinder pressure and the pedal stroke with respect to the target braking force is changed according to at least one of the master cylinder pressure and the pedal stroke. In particular, at the initial stage of the pedal depression, the contribution degree of the pedal stroke is greater. I try to get bigger. This has a general tendency for the driver to mainly adjust the pedal stroke in the region where the desired deceleration is low, and conversely to adjust the pedal effort mainly in the region where the desired deceleration is high. Because.
JP 11-301434 A

In general, the relationship between the master cylinder pressure and the pedal stroke is different between when the brake pedal is depressed and when the brake pedal is returned due to hysteresis characteristics of the master cylinder and the brake pedal.
Therefore, in the conventional example described in Patent Document 1, even if the respective degrees of contribution can be optimized according to the master cylinder pressure and the pedal stroke when the pedal is depressed, the optimal state will be lost when the pedal is returned. Become. As a result, there is a possibility that the target braking force does not coincide with the driver's braking operation, for example, the target braking force does not decrease even though the brake pedal is returned.
It is an object of the present invention to perform braking force control that reliably reflects the driver's intention in both the brake operation invocation process and the release process.

  In order to solve the above problems, a vehicle brake device according to the present invention includes a brake operator operated by a driver, and a master cylinder that generates fluid pressure when the brake operator is operated. The degree of contribution of both the operation amount and the fluid pressure is set according to at least one of the operation amount of the brake operator and the fluid pressure of the master cylinder, and the target braking force is set according to the operation amount, the fluid pressure, and the contribution degree. And the braking force is controlled in accordance with the calculated target braking force, and the contribution degree is fixed when the driver's braking operation is in the release process.

  According to the vehicle brake device of the present invention, when the driver's brake operation is in the release process, the contribution degree is fixed, so that the driving is performed in both the activation process and the release process in the driver's brake operation. Braking force control that reliably reflects the intention of the person. In other words, when the driver's brake operation is in the process of activation, the contribution degree is optimized, but when the shift is made to the release process, the contribution degree is fixed (change is prohibited), so that the brake operation is in the release process. It is possible to avoid a situation in which the target braking force does not coincide with the driver's braking operation, for example, the target braking force does not decrease.

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. A master cylinder 2 that converts a driver's pedal depression force input to the brake pedal 1 (brake operator) into hydraulic pressure is communicated with the rear left and right wheel cylinders 3RL and 3RR on the primary side, and the front left and right wheel cylinders 3FL on the secondary side. -It communicates with 3FR. 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 3FL to 3RR 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, a gate valve 4r that can close the flow path between the master cylinder 2 and the wheel cylinders 3RL and 3RR, and an inlet valve that can close the flow path between the gate valve 4r and the wheel cylinder 3RL (3RR) 5RL (5RR), an outlet valve 6RL (6RR) capable of opening a flow path connecting between the inlet valve 5RL (5RR) and the wheel cylinder 3RL (3RR) and the reservoir tank 2a of the master cylinder 2, and an outlet valve 6RL, 6RR and the reservoir tank 2a, and the pump 7r which connected the discharge side between the gate valve 4r and the inlet valves 5RL and 5RR.

  Here, the gate valve 4r, the inlet valves 5RL and 5RR, and the outlet valves 6RL and 6RR are two-port two-position switching / spring offset type electromagnetic operation valves, respectively. The gate valve 4r and the inlet valves 5RL and 5RR are The flow path is opened at the non-excited normal position, and the outlet valves 6RL and 5RR are configured to close the flow path at the non-excited normal position. Each valve only needs to be able to open and close the flow path. Therefore, the gate valve 4r and the inlet valves 5RL and 5RR open the flow path at the excited offset position, and the outlet valves 6RL and 6RR are excited. The flow path may be closed at the position.

The pump 7r is configured 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 5RL (5RR) and the outlet valve 6RL (6RR) are kept in a non-excited normal position by exciting and closing the gate valve 4r and driving the pump 7r, whereby the reservoir tank The brake fluid of 2a is sucked and the hydraulic pressure of the wheel cylinder 3RL (3RR) can be increased by the discharge pressure.

Further, by energizing the gate valve 4r and the inlet valve 5RL (5RR) while closing the outlet valve 6RL (6RR) in the non-excited normal position, the reservoir tank 2a and the reservoir tank 2a and the wheel cylinder 3RL (3RR) are closed. Each flow path to the pump 7r can be blocked, and the hydraulic pressure of the wheel cylinder 3RL (3RR) can be maintained.
Further, the outlet valve 6RL (6RR) is excited and opened, and the gate valve 4r and the inlet valve 5RL (5RR) are excited to close each other, whereby the hydraulic pressure of the wheel cylinder 3RL (3RR) is reduced to the reservoir tank 2a. And can be decompressed.

Further, the hydraulic pressure from the master cylinder 2 is transmitted to the wheel cylinder 3RL (3RR) by setting all of the gate valve 4r, the inlet valve 5RL (5RR), and the outlet valve 6RL (6RR) to the non-excited normal position. It becomes a normal brake.
The secondary side hydraulic system also includes the same gate valve 4f, inlet valves 5FL and 5FR, outlet valves 6FL and 6FR, and pump 7f as the primary side, and each operation is the same as the primary side. Detailed description thereof will be omitted.

  A stroke simulator 8 is connected to the secondary side of the master cylinder 2 in order to produce an appropriate pedal stroke and pedal reaction force for the driver's brake operation. The stroke simulator 8 is a single-acting cylinder that elastically strokes according to the hydraulic pressure from the master cylinder 2. That is, it is composed of a spring-type accumulator having a compression spring 8a interposed between the bottom of the cylinder and the piston. When the compression spring 8a elastically contracts as the hydraulic pressure increases, Power is produced.

  The above-described gate valves 4f and 4r, inlet valves 5FL to 5RR, outlet valves 6FL to 6RR, and pumps 7f and 7r are driven and controlled by the controller 9. The controller 9 normally detects the pedal stroke Ss detected by the stroke sensor 10 and the pressure sensor 11 in a state where the gate valves 4f and 4r are closed by executing a braking force control process shown in FIG. The brake-by-wire is executed based on the master cylinder pressure Pm. Further, at the time of fail-safe such as a pump failure, the gate valves 4f and 4r are opened, and the hydraulic pressure from the master cylinder 2 is transmitted to the wheel cylinders 3FL to 3RR to form a normal brake.

Next, the braking force control process executed by the controller 9 will be described based on the flowchart of FIG. This process is executed by timer interruption every predetermined time (for example, 10 msec).
First, in step S1, the pedal stroke Ss and the master cylinder pressure Pm are read.
In the subsequent step S2, the pedal depression force Fs is calculated according to the pedal stroke Ss with reference to the control map of FIG. In this control map, the horizontal axis represents the pedal stroke Ss and the vertical axis represents the pedal depression force Fs. When the pedal stroke Ss increases, the pedal depression force Fs increases. As the pedal stroke Ss increases, the increase rate of the pedal depression force Fs increases. Is set to

In the subsequent step S3, the pedal depression force Fp is calculated according to the master cylinder pressure Pm with reference to the control map of FIG. This control map is set so that the horizontal axis represents the master cylinder pressure Pm, the vertical axis represents the pedal depression force Fp, and the pedal depression force Fp increases in proportion to the increase in the master cylinder pressure Pm.
In the subsequent step S4, the contribution degree α of the pedal effort Fs and Fp is calculated according to the master cylinder pressure Pm with reference to the control map of FIG. This control map is set such that the horizontal axis is the master cylinder pressure Pm and the vertical axis is the contribution degree α, and the contribution degree α increases in the range of 0 to 1 as the master cylinder pressure Pm increases.

In subsequent step S5, it is determined whether or not the pedal stroke Ss is larger than a predetermined value S _OFF . When the determination result is “Ss ≦ S _OFF ”, it is determined that the brake operation has been released, and the process proceeds to step S6. On the other hand, when the determination result is “Ss> S _OFF ”, it is determined that the brake operation has not been released, and the process proceeds to step S7.
In step S6, as shown in the following equation (1), the contribution degree α _(n−1) used in the previous calculation process is updated to 0 and stored.
α _(n-1) ← 0 ……… (1)

In step S7, as shown in the following equation (2), by selecting high between the contribution degree α _(n) calculated in step S4 and the contribution degree α _(n−1) used in the previous calculation process, The final contribution degree α is calculated.
α = max [α _(n) , α _(n-1) ] (2)
In the subsequent step S8, as shown in the following equation (3), the final pedal depression force F is calculated according to the pedal depression forces Fs and Fp and the contribution degree α.
F = α × Fp + (1−α) Fs (3)

  Here, according to the above equation (3), “α” represents the contribution degree of the pedal depression force Fp (or master cylinder pressure Pm), and “1-α” represents the contribution degree of the pedal depression force Fs (or pedal stroke Ss). Represents. That is, as α increases, the contribution degree of the master cylinder pressure Pm to the final pedal depression force F increases, and the contribution degree of the pedal stroke Ss decreases. Conversely, as α is smaller, the contribution degree of the master cylinder pressure Pm to the final pedal depression force F becomes smaller and the contribution degree of the pedal stroke Ss becomes larger.

In the subsequent step S9, the target deceleration G is calculated according to the pedal depression force F with reference to the control map of FIG. This control map is set so that when the pedal depression force F increases, the target deceleration G increases in proportion to the pedal depression force F on the horizontal axis and the target deceleration G on the vertical axis.
In the subsequent step S10, as shown in the following formula (4), the target hydraulic pressure Pi (i = FL, FR, RL, RR) of each wheel cylinder is calculated according to the target deceleration G and the coefficient k. Here, the coefficient k is determined by vehicle weight, brake rotor effective diameter, tire moving radius, brake pad friction coefficient, road surface friction coefficient, vehicle attitude, and the like.
Pi = k × G (4)

In the following step S11, the gate valves 4f and 4r, the inlet valves 5FL to 5RR, the outlet valves 6FL to 6RR, and the pumps 7f and 7r are driven and controlled so that the target hydraulic pressure Pi is generated in each wheel cylinder. Return to the main program.
From the above, the processing in steps S4 to S7 corresponds to “setting means”, the processing in steps S2, S3, and S8 to S10 corresponds to “calculation means”, and the processing in step S11 corresponds to “control means”. Yes.

Next, the operation and effects of the one embodiment will be described.
Suppose now that normal brake-by-wire is performed. That is, with the gate valves 4f and 4r closed, the inlet valves 5FL to 5RR, the outlet valves 6FL to 6RR, and the pumps 7f and 7r are driven and controlled to control the braking force according to the driver's brake operation.
First, the pedal depression force Fs based on the pedal stroke Ss and the pedal depression force Fp based on the master cylinder pressure Pm are calculated (steps S2 and S3), and the target deceleration is determined according to the pedal depression force Fs and Fp and the contribution degree α. G is calculated (steps S8 and S9), and braking force control is performed according to the target deceleration G (steps S10 and S11).

  The driver tends to adjust the pedal stroke mainly in the region where the desired deceleration is low, and conversely, the driver tends to adjust the pedal effort mainly in the region where the desired deceleration is high. Therefore, at the initial stage of pedal depression, α is set small so that the degree of contribution of the pedal stroke Ss to the target deceleration G is large (step S4). As a result, when the brake operation is in the process of being activated, that is, when the pedal is depressed, it is possible to perform the braking force control that reliably reflects the driver's intention.

By the way, generally, the relationship between the master cylinder pressure Pm and the pedal stroke Ss differs depending on the hysteresis characteristics of the master cylinder 2 and the brake pedal 1 when the brake pedal is depressed.
Therefore, even when the respective contribution degrees α can be optimized according to the master cylinder pressure Pm and the pedal stroke Ss when the pedal is depressed, the optimal state will be lost when the pedal is returned. That is, as shown in FIG. 7A, when the brake pedal 1 is returned, the contribution degree α calculated according to the master cylinder pressure Pm decreases from 1 to 0. At this time, if the target deceleration assuming that “F = α × Fp” is Gp and the target deceleration assuming “F = (1−α) Fs” is Gs, the target deceleration Gp is While it decreases to 0, the target deceleration Gs increases from 0, and the magnitude relationship between the two reverses at a certain point in time. At this time, if the selection high of Gp and Gs is set to the actual target deceleration G, the target deceleration G is determined to be equal to the driver's brake operation, for example, the target deceleration G does not decrease although the brake operation is in the release process. It will not match.

Therefore, in the present embodiment, until the brake operation is released (the determination in step S5 is “Yes”), α _(n) calculated according to the master cylinder pressure Pm and the previous value α _(n−1) The degree of contribution is set by the select high (step S7).
As a result, when the pedal depressing operation is shifted to the pedal returning operation, as shown in FIG. 7B, the decrease in the contribution degree α is prevented, that is, the state set immediately before (α = 1 in the drawing) is set. Since it can be maintained and fixed, the target deceleration G can be matched with the driver's braking operation. That is, it is possible to perform the braking force control that reliably reflects the driver's intention even in the process of releasing the brake operation. FIG. 7B shows an example in which α = 1 is maintained and fixed. However, α = 1 is not always fixed.

  Further, according to the hysteresis characteristic, when the pedal is returned, the master cylinder pressure Pm starts to decrease earlier than the pedal stroke Ss (FIG. 7). Therefore, fixing α to a large value increases the contribution degree of the master cylinder Pm, so that the target deceleration G can be quickly reduced with respect to the pedal return operation, and the response is excellent. However, as pedal feeling, there is a case where hysteresis having a large hysteresis, that is, a characteristic in which the braking force does not decrease even if the pedal depression force is slightly loosened is preferred. In this case, the pedal depression force F or the target deceleration is intentionally used. A hysteresis characteristic can also be produced by adding only the hysteresis amount to G.

Further, when the contribution degree α is fixed, it is conceivable to determine the pedal return operation from the pedal stroke Ss and fix it to the contribution degree α at the time when the pedal return operation is detected. There is a risk that the accuracy may decrease due to an error, a determination delay of the pedal return operation, or the like.
Therefore, the change of the contribution degree α is peak-held by the select high for each calculation cycle (step S7). As a result, it is possible to reliably fix the contribution degree α at the time when the brake operation has shifted from the activation process to the release process, and thus it is possible to prevent the above-described decrease in accuracy.

Further, when the brake operation is completely cancelled until the operation amount is zero (the determination in Step S5 is “No”), the contribution degree α _(n−1) used in the previous calculation process is updated to 0 and stored (Step S5). S6). As a result, the peak held contribution degree α can be reset. Therefore, when the driver starts to step on the pedal again (the determination in step S5 is “Yes”), the optimum contribution according to the master cylinder pressure Pm is achieved. The degree α can be set (step S7), and the braking force control that reliably reflects the driver's intention can be performed.

  In the above-described embodiment, as shown in FIG. 7A, the contribution degree α is fixed immediately after the driver's brake operation shifts to the release process. However, the present invention is not limited to this. Absent. In short, it is only necessary to avoid a situation in which the target deceleration G does not decrease even though the brake operation is in the release process. For example, as shown in FIG. 8, the magnitude relationship between the target deceleration Gp and Gs is reversed. The contribution degree α may be fixed from the point of time.

  In the above embodiment, as shown in FIG. 7B, the target deceleration G is calculated according to the pedal depression force Fp by fixing the contribution degree α to 1, but the present invention is not limited to this. Is not to be done. In short, it is only necessary to avoid a situation in which the target deceleration G does not decrease even though the brake operation is in the release process. For example, as shown in FIG. If Fs and Fs match, the target deceleration G may be calculated according to the pedal effort Fs by fixing the contribution degree α to 0.

In the above-described embodiment, the contribution degree α is changed continuously and continuously in accordance with the master cylinder pressure Pm. However, the contribution degree α is not limited to this, and is stepped in accordance with the master cylinder pressure Pm. The contribution degree α may be changed, and may be only one stage.
In the above-described embodiment, the sum of the contribution degree of Pm and the contribution degree of Ss is always set to be constant. However, the present invention is not limited to this. For example, the setting may be such that the sum of the contribution degrees changes such that one contribution degree increases and the other contribution degree remains unchanged.

In the above embodiment, the degree of contribution α is calculated according to only the master cylinder pressure Pm. However, the present invention is not limited to this. That is, the contribution degree α may be calculated according to only the pedal stroke Ss, or the contribution degree α may be calculated according to both the stroke amount α and the master cylinder pressure Pm.
Furthermore, 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 may be used as long as it has an electronically controllable energy source such as a regenerative motor brake.

It is a schematic structure of a brake system. It is a flowchart which shows a braking force control process. It is a control map used for calculation of pedal effort Fs. It is a control map used for calculation of pedal effort Fp. It is a control map used for calculating the contribution degree α. 4 is a control map used for calculating a target deceleration G. It is a time chart explaining the subject of a prior art and the effect of this application. It is a time chart explaining another Example. It is a time chart explaining another Example.

Explanation of symbols

1 Brake pedal (brake operator)
2 Master cylinder 3FL to 3RR Wheel cylinder 4f and 4r Gate valve 5FL to 5RR Inlet valve 6FL to 6RR Outlet valve 7f and 7r Pump 8 Stroke simulator 9 Controller 10 Stroke sensor 11 Pressure sensor 12 Flow path

Claims (3)

According to at least one of a brake operation element operated by a driver, a master cylinder that generates fluid pressure when the brake operation element is operated, an operation amount of the brake operation element, and a fluid pressure of the master cylinder Setting means for setting a contribution degree of both the operation amount and the fluid pressure; a calculation means for calculating a target braking force according to the contribution amount set by the operation amount and the fluid pressure and the setting means; A vehicle brake device comprising: control means for controlling the braking force according to the target braking force calculated by the calculating means;
The setting device fixes the degree of contribution when the driver's brake operation is in a release process.   The vehicle brake device according to claim 1, wherein the setting unit fixes the contribution degree when the driver's brake operation is in a release process by peak-holding the contribution degree.   3. The vehicle brake device according to claim 1, wherein the setting unit stops fixing the contribution degree when the driver's brake operation is released to an operation amount of zero. 4.

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