JP4572738B2 - Brake device for vehicle - Google Patents

Description

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

Conventionally, there is an electric parking brake that uses an electric motor to operate the parking brake, and by providing a drive circuit that changes the output voltage to the electric motor according to the inclination angle of the vehicle body detected by the inclination switch, It has been proposed to generate a braking force without excess or deficiency according to the inclination angle (see Patent Document 1).
JP 2003-182545 A

However, in the conventional example described in Patent Document 1 above, since the braking force of the parking brake is changed according to the inclination angle of the vehicle body, if the road surface gradient changes between the wheel bases, Since the slope of the road surface on which the braking wheel is in contact and the inclination angle of the vehicle body are different, there is a possibility that the braking force as a parking brake will be excessive or insufficient.
Therefore, the present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to provide a vehicle brake device that can generate a braking force for maintaining a stopped state without excess or deficiency.

  In order to solve the above-described problems, the vehicle brake device according to the present invention detects a vehicle body inclination angle corresponding to a road surface gradient, and is necessary to maintain a stop state according to the detected vehicle body inclination angle. When the target braking force is applied to the wheel, it is determined whether there is a road gradient difference between the wheel bases at the stopped position, and when it is determined that there is a road gradient difference between the wheel bases, The target braking force is corrected.

  According to the vehicle brake device of the present invention, when it is determined that there is a road surface gradient difference between the wheel bases, the braking force for maintaining the stop state is generated without excess or shortage by correcting the target braking force. Can be made.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of the present invention. An electromagnetic induction type wheel speed sensor 1 for detecting the wheel speed Vwi (i = FL to RR) of each wheel, an acceleration sensor 2 capable of detecting a vehicle body inclination angle θ according to a road surface gradient, and an operation signal for a parking brake Is connected to the controller 8. The acceleration sensor 2 detects the uphill direction as a positive value and detects the downhill direction as a negative value. Further, the PKB switch 3 can be switched ON / OFF, for example, and activates the parking brake when ON, and deactivates the parking brake when OFF.

The controller 8 is composed of, for example, a microcomputer, and executes a gradient difference determination process and a PKB operation control process, which will be described later, based on various input signals, and drives the brake actuator 9 to control the parking brake. Activate / deactivate.
Here, the brake actuator 9 is interposed between the master cylinder 10 and each of the wheel cylinders 11FL to 11RR as shown in FIG.

The master cylinder 10 is a tandem type that produces two systems of hydraulic pressure according to the driver's pedaling force. The master cylinder 10 transmits the primary side to the front left and rear right wheel cylinders 11FL and 11RR, and the secondary side transmits the right front wheel and A diagonal split system is used for transmission to the left rear wheel cylinders 11FR and 11RL.
Each of the wheel cylinders 11FL to 11RR 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.

The brake actuator 9 uses a brake fluid pressure control circuit used for anti-skid control (ABS), traction control (TCS), stability control (VDC: Vehicle Dynamics Control), etc. Regardless, the hydraulic pressures of the wheel cylinders 11FL to 11RR can be increased, held and reduced.
The primary side has a normally open type first gate valve 12A capable of closing a flow path between the master cylinder 10 and the wheel cylinder 11FL (11RR), and a flow path between the first gate valve 12A and the wheel cylinder 11FL (11RR). A normally open type inlet valve 13FL (13RR) that can be closed, an accumulator 14 communicating between the wheel cylinder 11FL (11RR) and the inlet valve 13FL (13RR), and a flow path between the wheel cylinder 11FL (11RR) and the accumulator 14 are provided. A normally closed outlet valve 15FL (15RR) that can be opened and a flow path that communicates between the master cylinder 10 and the first gate valve 12A and between the accumulator 14 and the outlet valve 15FL (15RR) are opened. The normally closed type second gate valve 16A, the accumulator 14 and the outlet valve 15FL (15RR) are connected to the suction side, and the first gate valve 12A and the inlet valve 13FL (13RR) are connected to the discharge side. And a pump 17. A damper chamber 18 is disposed on the discharge side of the pump 17 to suppress pulsation of discharged brake fluid and weaken pedal vibration.

Similarly to the primary side, the secondary side also has a first gate valve 12B, an inlet valve 13FR (13RL), an accumulator 14, an outlet valve 15FR (15RL), a second gate valve 16B, a pump 17, A damper chamber 18.
The first gate valves 12A and 12B, the inlet valves 13FL to 13RR, the outlet valves 15FL to 15RR, and the second gate valves 16A and 16B are two-port, two-position switching, single solenoid, and spring offset type electromagnetic operations, respectively. The first gate valves 12A and 12B and the inlet valves 13FL to 13RR open the flow path at a non-excited normal position, and the outlet valves 15FL to 15RR and the second gate valves 16A and 16B are non-excited. The flow path is closed at the normal position.

The accumulator 14 is a spring-type accumulator in which a compression spring is opposed to a cylinder piston.
The pump 17 is 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 primary side will be described as an example. When the first gate valve 12A, the inlet valve 13FL (13RR), the outlet valve 15FL (15RR), and the second gate valve 16A are all in the non-excited normal position. Then, the hydraulic pressure from the master cylinder 2 is transmitted as it is to the wheel cylinder 11FL (11RR) and becomes a normal brake.

  Even when the brake pedal is not operated, the first gate valve 12A is excited and closed while the inlet valve 13FL (13RR) and the outlet valve 15FL (15RR) are kept in the non-excited normal position. The second gate valve 16A is excited and opened, and the pump 17 is further driven to suck the liquid in the master cylinder 2 through the second gate valve 16A and discharge the liquid pressure to the inlet valve 13FL (13RR). The pressure can be transmitted to the wheel cylinder 11FL (11RR) through the pressure to increase the pressure.

  If the inlet valve 13FL (13RR) is excited and closed when the first gate valve 12A, the outlet valve 15FL (15RR), and the second gate valve 16A are in the non-excited normal position, the wheel cylinder 11FL (11RR) is closed. ) To the master cylinder 2 and the accumulator 14 are blocked, and the hydraulic pressure of the wheel cylinder 11FL (11RR) is maintained.

  Further, when the first gate valve 12A and the second gate valve 16A are in the non-excited normal position, the inlet valve 13FL (13RR) is excited and closed, and the outlet valve 15FL (15RR) is excited and opened. The hydraulic pressure in the wheel cylinder 11FL (11RR) flows into the accumulator 14 and is reduced. The hydraulic pressure flowing into the accumulator 14 is sucked by the pump 17 and returned to the master cylinder 2.

Also on the secondary side, the normal braking, pressure increasing, holding, and pressure reducing operations are the same as the operations on the primary side, and detailed description thereof will be omitted.
Therefore, the controller 8 controls each wheel by drivingly controlling the first gate valves 12A and 12B, the inlet valves 13FL to 13RR, the outlet valves 15FL to 15RR, the second gate valves 16A and 16B, and the pump 17. The fluid pressure in the cylinders 11FL to 11RR can be increased, held, and reduced.

  However, in this embodiment, the braking force is applied only to the rear wheel cylinders 11RL and 11RR as the parking brake, the parking brake is operated by increasing and maintaining the wheel cylinder pressure, and the parking brake is applied by reducing the pressure. Shall be released. Therefore, the rear wheel is a braking wheel on which the parking brake is operated, and the front wheel is a non-braking wheel on which the parking brake is not operated.

Next, the gradient difference determination process of the first embodiment executed by the controller 8 will be described based on the flowchart of FIG.
This gradient difference determination process is executed as a timer interruption process every predetermined time (for example, 10 msec). First, in step S1, the vehicle speed V is calculated based on each wheel speed Vwi. In this embodiment, the vehicle speed V is calculated based on each wheel speed Vwi. However, the present invention is not limited to this, and the longitudinal acceleration of the vehicle body is detected by an acceleration sensor, and this longitudinal acceleration is taken into account. The vehicle speed V may be calculated.

In a subsequent step S2, it is determined whether or not the vehicle speed V is greater than zero. When the determination result is V = 0, it is determined that the vehicle is stopped, and the process proceeds to step S15 described later. On the other hand, when the determination result is V> 0, it is determined that the vehicle is moving, and the process proceeds to step S3.
In step S3, it is determined whether or not the change amount Δθ (= | θ _(n-1) −θ _(n) |) of the tilt angle θ from one sampling before is larger than a predetermined value. When the determination result is Δθ> predetermined value, the process proceeds to step S8 described later. On the other hand, when the determination result is Δθ ≦ predetermined value, the process proceeds to step S4.

In step S4, the initial inclination angle α representing the inclination angle immediately before the change in the inclination angle θ of the vehicle body during movement of the vehicle is reset to zero.
In the subsequent step S5, the control flag f _M is reset to “0”.
In the subsequent step S6, the cumulative movement distance Da representing the movement distance of the vehicle from the point where the inclination angle θ of the vehicle body has changed is reset to zero.

In the subsequent step S7, the control flag f _C is reset to “0” and then the process returns to the predetermined main program.
On the other hand, in step S8 which shifts from step S3, it is determined whether or not the control flag f _M is reset to “0”. When the determination result is f _M = 0, it is determined that the inclination angle θ has just changed, and the process proceeds to step S9.

In step S9, the inclination angle θ _(n−1) before one sampling is stored as the initial inclination angle α.
In the subsequent step S10, the control flag f _M is set to “1”, and then the process proceeds to step S11. On the other hand, when the determination result in step S8 is f _M = 1, the process proceeds to step S11.

In step S11, as shown in the following equation (1), the moving distance D of the vehicle from before one sampling is calculated. Here, V is a vehicle speed and T is a calculation cycle.
D = V × T (1)
In the subsequent step S12, as shown in the following equation (2), the cumulative movement distance Da of the vehicle from the point where the inclination angle θ of the vehicle body changes is calculated.

Da _(n) = Da _(n-1) + D (2)
In the subsequent step S13, it is determined whether or not the cumulative travel distance Da is equal to or greater than the vehicle wheel base L. When the determination result is Da ≧ L, it is determined that there is no road surface gradient difference between the wheel bases, and the process proceeds to step S7. On the other hand, when the determination result is Da <L, it is determined that there is a road gradient difference between the wheel bases, and the process proceeds to step S14.

In step S14, the control flag f _C is set to “1”, and then the process returns to the predetermined main program.
On the other hand, in step S15, which shifts from step S2, as shown in the following equation (3), after calculating the cumulative travel distance Da of the vehicle from the point where the inclination angle θ of the vehicle body has changed, the flow shifts to step S13. .

Da _(n) = Da _(n-1) (3)
Next, the PKB operation control process executed by the controller 8 will be described based on the flowchart of FIG.
This PKB operation control process is executed as a timer interrupt process for every predetermined time (for example, 10 msec). First, in step S21, it is determined whether or not the PKB switch 3 is set to ON. Here, when the PKB switch 3 is set to OFF, the process proceeds to step S22.

In step S22, the drive control of the brake actuator 9 is deactivated, so that the parking brake is deactivated and then the process returns to the predetermined main program.
On the other hand, when the PKB switch 3 is set to ON in step S21, the process proceeds to step S23.
In step S23, as shown in the following equation (4), a target braking force Ft corresponding to the vehicle body inclination angle θ (hereinafter referred to as γ in the first embodiment) is calculated. Here, m is the vehicle weight and g is the gravitational acceleration.

Ft = m × g × sinγ (4)
In the subsequent step S24, it is determined whether or not the control flag f _C set in the gradient difference determination process of FIG. 3 has been reset to “0”. When the determination result is f _C = 0, it is determined that there is no road surface gradient difference between the wheel bases, and the process proceeds to step S25.
In step S25, the brake actuator 9 is driven and controlled so that the target braking force Ft is applied to the wheel cylinders 11RL and 11RR of the rear wheels, so that the parking brake is actuated before returning to a predetermined main program.

On the other hand, when the determination result in step S24 is f _C = 1, it is determined that there is a road surface gradient difference between the wheel bases, and the process proceeds to step S26.
In step S26, it is determined whether the stop position is an ascending gradient or a descending gradient based on the inclination angle of the vehicle body. Here, when it is a downward slope, it transfers to step S32 mentioned later. On the other hand, when it is a climbing slope, the process proceeds to step S27.

In step S27, it is determined whether or not the initial inclination angle α set in the gradient difference determination process of FIG. 3 is larger than the current inclination angle γ. When the determination result is α> γ, the process proceeds to step S28.
In step S28, as shown in the following equation (5), a correction amount ΔF of the target braking force Ft is calculated.

ΔF = m × g × sin α−m × g × sin γ (5)
In subsequent step S29, as shown in the following equation (6), the target braking force Ft is corrected by adding the correction amount ΔF, and then the process proceeds to step S25.
Ft ← Ft + ΔF (6)
On the other hand, when the determination result in step S27 is α ≦ γ, the process proceeds to step S30.

In step S30, as shown in the following equation (7), a correction amount ΔF of the target braking force Ft is calculated.
ΔF = m × g × sin γ−m × g × sin α (7)
In subsequent step S31, as shown in the following equation (8), the target braking force Ft is corrected by subtraction of the correction amount ΔF, and then the process proceeds to step S25.

Ft ← Ft−ΔF (8)
On the other hand, in step S32 which moves from step S26, it is determined whether or not the initial inclination angle α is smaller than the current inclination angle γ. When the determination result is α <γ, the process proceeds to step S33.
In step S33, a correction amount ΔF of the target braking force Ft is calculated as shown in the following equation (9).

ΔF = | m × g × sin α−m × g × sin γ | (9)
In the subsequent step S34, as shown in the following equation (10), the target braking force Ft is corrected by subtraction of the correction amount ΔF, and then the process proceeds to step S25.
Ft ← Ft−ΔF (10)
On the other hand, when the determination result in step S32 is α ≧ γ, the process proceeds to step S35.

In step S35, as shown in the following equation (11), a correction amount ΔF of the target braking force Ft is calculated.
ΔF = | m × g × sin γ−m × g × sin α | (11)
In the subsequent step S36, as shown in the following equation (12), the target braking force Ft is corrected by adding the correction amount ΔF, and then the process proceeds to step S25.

Ft ← Ft + ΔF (12)
From the above, the acceleration sensor 2 corresponds to “inclination angle detection means”, the PKB operation control process in FIG. 4 corresponds to “stop state maintaining means”, and the gradient difference determination process in FIG. 3 becomes “gradient difference determination means”. It corresponds.
Next, operations and effects of the first embodiment will be described.

  Now, assume that the vehicle stops on an uphill road with a constant road gradient as shown in FIG. 5, and the driver sets the PKB switch 3 to ON (determination in step S21 is “Yes”). At this time, a target braking force Ft necessary for maintaining the stop state is calculated according to the inclination angle γ of the vehicle body (step S23), and the target braking force Ft is applied to the braking wheel (rear wheel). Thus, the parking brake is operated by drivingly controlling the brake actuator 9 (step S25).

As a result, a braking force F1 equal to the downward force F0 (= m × g × sinγ) acting on the braking wheel is generated in the rear wheel cylinders 11RL and 11RR. A braking force without deficiency can be generated.
That is, since the target braking force Ft increases as the road surface gradient increases, it is possible to avoid a situation in which the braking force as a parking brake is insufficient and the vehicle slides down even when the road surface gradient is steep. Conversely, the smaller the road surface gradient, the smaller the target braking force Ft. Therefore, when the road surface gradient is gentle or substantially flat, the braking force as a parking brake is not increased unnecessarily, and the length of the brake actuator 9 is increased. Life can be extended.

However, when the target braking force Ft is simply changed according to the inclination angle γ of the vehicle body, as shown in FIGS. 6 and 7, if the road surface gradient changes between the wheel bases, the road surface on which the braking wheels are in contact Therefore, when the parking brake is operated, the braking force may be excessive or insufficient.
That is, in the case of FIG. 6, the road surface gradient α in contact with the braking wheel is larger than the road surface gradient β in contact with the non-braking wheel, and α> γ. The force F0 ′ (= m × g × sin α) is greater than F0 (= m × g × sin γ). Accordingly, the braking force equal to F0 cannot maintain the stopped state, and the vehicle may slide down.

On the other hand, in the case of FIG. 7, the road surface gradient α in contact with the braking wheel is smaller than the road surface gradient β in contact with the non-braking, and α <γ. The force F0 ′ (= m × g × sin α) is smaller than F0 (= m × g × sin γ). Therefore, a braking force equal to F0 may result in an excessive braking force for maintaining the stop state.
Therefore, in the present embodiment, it is determined whether or not there is a road surface gradient difference between the wheel bases at the stopped position (steps S2 to S14), and when it is determined that there is a road surface gradient difference between the wheel bases ( If the determination in step S24 is “No”), the target braking force Ft is corrected (steps S26 to S36). Thereby, when operating a parking brake, the braking force for maintaining a stop state can be generated without excess and deficiency.

  First, as shown in FIG. 8, when the stop position is an ascending slope (the determination in step S26 is “Yes”), and the road surface slope α in contact with the braking wheel is larger than the inclination angle γ of the vehicle body (step When the determination in S27 is “Yes”, a correction amount ΔF (= m × g × sin α−m × g × sin γ) is calculated (step S28), and the target braking force Ft is corrected by adding the correction amount ΔF (step S28). S29). As a result, when the parking brake is operated, it is possible to avoid a situation in which the vehicle slides down due to insufficient braking force, and to reliably maintain the stopped state. This correction processing is performed when the front wheel at the stop position exceeds the point P where the climb gradient changes (decreases) from α to β, and the rear wheel does not exceed the point P, that is, the climbing direction of the vehicle body. This is executed when the inclination angle γ (positive value) to is smaller than α and larger than β.

  On the other hand, as shown in FIG. 9, when the road surface gradient α in contact with the braking wheel is smaller than the inclination angle γ of the vehicle body (the determination in step S27 is “No”), the correction amount ΔF (= m × g × sinγ−m × g × sinα) is calculated (step S30), and the target braking force Ft is corrected by subtraction of the correction amount ΔF (step S31). Thereby, when operating a parking brake, the useless increase of braking force can be prevented reliably. This correction processing is performed when the front wheel at the stop position exceeds the point P where the climb gradient changes (increases) from α to β and the rear wheel does not exceed the point P, that is, the climbing direction of the vehicle body. This is executed when the inclination angle γ (positive value) to is greater than α and smaller than β.

  Further, as shown in FIG. 10, when the stop position is a downward slope (the determination in step S26 is “No”), and the road surface slope α in contact with the braking wheel is smaller than the inclination angle γ of the vehicle body (step When the determination in S32 is “Yes”), a correction amount ΔF (= | m × g × sin α−m × g × sin γ |) is calculated (step S33), and the target braking force Ft is corrected by subtraction of the correction amount ΔF. (Step S34). Thereby, when operating a parking brake, the useless increase of braking force can be prevented reliably. This correction processing is performed when the front wheel at the stop position exceeds the point P where the downward gradient changes (increases) from α to β and the rear wheel does not exceed the point P, that is, the downhill of the vehicle body This is executed when the inclination angle γ (negative value) in the direction is larger than α and smaller than β.

  On the other hand, as shown in FIG. 11, when the road surface gradient α in contact with the braking wheel is larger than the inclination angle γ of the vehicle body (the determination in step S32 is “No”), the correction amount ΔF (= | m × g * Sinγ-m * g * sinα |) is calculated (step S35), and the target braking force Ft is corrected by adding the correction amount ΔF (step S36). As a result, when the parking brake is operated, it is possible to avoid a situation in which the vehicle slides down due to insufficient braking force, and to reliably maintain the stopped state. This correction processing is performed when the front wheel at the stop position exceeds the point P where the downward gradient changes (decreases) from α to β and the rear wheel does not exceed the point P, that is, the downhill of the vehicle body This is executed when the inclination angle γ (negative value) in the direction is smaller than α and larger than β.

  As described above, when it is determined that there is a road surface gradient difference between the wheel bases, when the road surface gradient α on the braking wheel side is larger than the road surface gradient β on the non-braking wheel side (the determination in step S27 is “Yes”). "Or S32 is" No "), the target braking force Ft is corrected in the increasing direction, and when the road surface gradient α on the braking wheel side is smaller than the road surface gradient β on the non-braking wheel side (determination in step S27). Is "No" or the determination of S32 is "Yes"), by correcting the target braking force Ft in the decreasing direction, when operating the parking brake, the braking force for maintaining the stop state is generated without excess or deficiency. be able to.

  Further, a correction amount ΔF is calculated according to the difference between the initial inclination angle α immediately before the vehicle body inclination angle changes during the movement of the vehicle and the inclination angle γ at the stop position, and the correction amount ΔF is added or subtracted. Since the target braking force Ft is corrected (steps S28 to S31, S33 to S36), when operating the parking brake, the braking force for maintaining the stop state can be accurately generated without excess or deficiency.

  Whether there is a road surface gradient difference between the wheel bases at the position where the vehicle is stopped is determined when the vehicle body inclination angle changes during the movement of the vehicle (both determinations in steps S2 and S3 are “Yes”). The accumulated travel distance Da of the vehicle from the vehicle is calculated (steps S12 and S15), and when the accumulated travel distance Da is shorter than the wheel base L (determination in step S13 is “No”), the road surface gradient between the wheel bases is calculated. It is determined that there is a difference (step S14). Conversely, when the cumulative movement distance Da is longer than the wheel base L (the determination in step S13 is “Yes”), it is determined that there is no road surface gradient difference between the wheel bases (step S7). Thus, the presence or absence of a road surface gradient difference between wheel bases can be easily and reliably determined.

  In the first embodiment, the present invention is applied to a configuration in which the rear wheel is a braking wheel and the front wheel is a non-braking wheel. However, the present invention is not limited to this, and the front wheel is a braking wheel and the rear wheel. The present invention can also be applied to a configuration in which a non-braking wheel is used. In addition, all the wheels may be brake wheels. In this case, a reduction in braking force may be corrected for a wheel with excessive braking force, and an increase in braking force may be corrected for a wheel with insufficient braking force.

  In the first embodiment, the present invention is applied to a system that operates the parking brake only when the PKB switch 3 is set to ON. However, the present invention is not limited to this, and the vehicle stops. The system that automatically activates the parking brake when the specified time has elapsed or the shift position of the automatic transmission is set to the parking range or neutral range and the brake pedal is depressed. The present invention can be applied.

  Further, in the first embodiment described above, a hydric brake using a hydraulic pressure as a transmission medium is employed as a braking mechanism for applying a brake, but the present invention is not limited to this. For example, by driving and controlling a cable, a link, or a braking mechanism that uses air pressure as a transmission medium, or an electric actuator, the disc rotor is clamped by a brake pad or a brake shoe is pressed against the inner peripheral surface of a brake drum. Any other braking mechanism such as an electric brake may be employed.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, whether or not there is a road gradient difference between the wheel bases is determined based on a load difference applied to the front wheel axle and the rear wheel axle.
Therefore, in the second embodiment, a load sensor capable of detecting the load Wf _D applied to the front wheel axle and the load Wr _D applied to the rear wheel axle is provided, for example, in the suspension, and the gradient difference determination process in FIG. Except for the change to the difference determination process, the same process as in the first embodiment is executed, and the detailed description of the same part is omitted.

First, in step S41, the vehicle speed V is calculated based on each wheel speed Vwi.
In a succeeding step S42, it is determined whether or not the vehicle speed V is zero. When this determination result is V> 0, it is determined that the vehicle is moving, and the process proceeds to step S43.
In step S43, the control flag f _C is reset to “0” and then the process returns to the predetermined main program.

On the other hand, when the determination result in step S42 is V = 0, it is determined that the vehicle is stopped, and the process proceeds to step S44.
In step S44, as shown in the following equation (13), the load Wf _E applied to the front wheel axle and the load Wr _E applied to the rear wheel axle are estimated according to the inclination angle θ of the vehicle body, and the following equation (14) is applied. As shown, a load difference ΔW _E applied to the front wheel axle and the rear wheel axle is calculated from the difference between the estimated loads Wf _E and Wr _E. Here, W is the vehicle weight, L is the wheel base, x is the distance between the front wheel axle and the center of gravity, and H is the height of the center of gravity.

Wf _E = W {(L−x) cos θ−H × sin θ} / L
Wr _E = W (x × cos θ + H × sin θ} / L (13)
ΔW _E = | Wf _E −Wr _E | (14)
In step S45, as shown in the following equation (15), calculates the load difference [Delta] W _D according to the front axle and the rear wheel axle from the difference between the load Wf _D and Wr _D detected by the load sensor.

ΔW _D = | Wf _D −Wr _D | (15)
In subsequent step S46, it is determined whether or not a value (ΔW _D −ΔW _E ) obtained by subtracting the load difference ΔW _E estimated according to the inclination angle θ from the load difference ΔW _D detected by actual measurement is equal to or less than a predetermined value. . When the determination result is (ΔW _D −ΔW _E ) ≦ predetermined value, it is determined that there is no road surface gradient difference between the wheel bases, and the process proceeds to step S43. On the other hand, when the determination result is (ΔW _D −ΔW _E )> predetermined value, it is determined that there is a road gradient difference between the wheel bases, and the process proceeds to step S47.

In step S47, the control flag f _C is set to “1” and then the process returns to the predetermined main program.
Instead of judging based on the difference between the estimated value and the detected value of the load difference between the front and rear wheels, it may be judged based on the difference between the estimated value and the detected value of one or both of the front and rear wheels.
Here, the gradient difference determination process of FIG. 12 corresponds to “gradient difference determination means”.

As described above, whether or not there is a road surface gradient difference between the wheel bases at the stop position is detected by estimating the load difference applied to the front wheel axle and the rear wheel axle according to the inclination angle θ and by measuring. (Steps S44 and S45), and when the estimated load difference ΔW _E and the detected load difference ΔW _D are different from each other by a predetermined value or more (the determination in Step S46 is “No”), there is a road surface gradient difference between the wheel bases. It is determined that there is (step S47). Conversely, when the shift amount between the load difference [Delta] W _D detected and estimated load difference [Delta] W _E is less than a predetermined value (determination of step S46 is "Yes"), it is determined that the road surface slope difference is not between the wheelbase (Step S43). Thus, the presence or absence of a road surface gradient difference between wheel bases can be easily and reliably determined. In addition, since the cumulative travel distance Da of the vehicle is not calculated, it is possible to determine the presence or absence of a road surface gradient difference between the wheel bases even at extremely low speeds where the wheel speed sensor cannot detect.

A correction amount ΔF is calculated according to a deviation amount (ΔW _D −ΔW _E ) between the estimated load difference ΔW _E and the detected load difference ΔW _D, and the target braking force Ft is obtained by adding or subtracting the correction amount ΔF. It may be corrected. Also by this, when operating the parking brake, it is possible to generate the braking force for maintaining the stop state accurately without excess or deficiency.
Other operational effects and the application range of the embodiment are the same as those of the first embodiment described above.

It is a schematic structure figure showing an embodiment of the present invention. It is a hydraulic circuit of a brake actuator. It is a flowchart which shows the gradient difference judgment process of 1st Embodiment. It is a flowchart which shows a PKB operation | movement control process. It is a figure explaining the target braking force when a road surface gradient is constant. It is a figure explaining the subject in case there is a road surface gradient difference between wheel bases (α> γ). It is a figure explaining the subject in case there is a road surface gradient difference between wheel bases (α <γ). It is a figure explaining correction amount (DELTA) F when there exists a road surface gradient difference between wheel bases at the stop position on an uphill road ((alpha)> (gamma)). It is a figure explaining correction amount (DELTA) F when there exists a road surface gradient difference between wheel bases at the stop position on an uphill road ((alpha) <gamma). It is a figure explaining correction amount (DELTA) F when there exists a road surface gradient difference between wheel bases in the stop position on a downhill road ((alpha) <gamma). It is a figure explaining correction amount (DELTA) F when there exists a road surface gradient difference between wheel bases at the stop position on a downhill road ((alpha)> (gamma)). It is a flowchart which shows the gradient difference judgment process of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel speed sensor 2 Acceleration sensor 3 PKB switch 8 Controller 9 Brake actuator 10 Master cylinder 11FL-11RR Wheel cylinder 12A, 12B 1st gate valve 13FL-13RR Inlet valve 14 Accumulator 15FL-15RR Outlet valve 16A, 16B 2nd gate valve 17 Pump 18 damper room

Claims (7)

Inclination angle detection means for detecting the inclination angle of the vehicle body according to the road surface gradient, and a target braking force necessary to maintain the stop state according to the inclination angle of the vehicle body detected by the inclination angle detection means is applied to the wheels. A vehicle brake device comprising: a stop state maintaining means;
A slope difference judging means for judging whether or not there is a road surface slope difference between the wheel bases at a stopped position;
The vehicle stop device, wherein the stop state maintaining means corrects the target braking force when the gradient difference determining means determines that there is a road surface gradient difference between the wheel bases.   The stop state maintaining means applies the target braking force to either one of the front wheels or the rear wheels, and the target braking force is determined when the gradient difference determining means determines that there is a road surface gradient difference between the wheel bases. 2. The target braking force is corrected in an increasing direction when a road surface gradient on the braking wheel side to which the target braking force is applied is larger than a road surface gradient on the non-braking wheel side to which no braking force is applied. The brake device for vehicles as described in.   The stop state maintaining means applies the target braking force to either one of the front wheels or the rear wheels, and the target braking force is determined when the gradient difference determining means determines that there is a road surface gradient difference between the wheel bases. 2. The target braking force is corrected in a decreasing direction when the road surface gradient on the braking wheel side to which the target braking force is applied is smaller than the road surface gradient on the non-braking wheel side on which no braking force is applied. Or the brake device for vehicles of 2.   The gradient difference determining means calculates a moving distance of the vehicle from a point where the inclination angle of the vehicle body detected by the inclination angle detecting means changes during the movement of the vehicle, and the moving distance is shorter than the wheel base. The vehicle brake device according to any one of claims 1 to 3, wherein it is determined that there is a road surface gradient difference between the wheel bases.   The stopping state maintaining means corrects the target braking force in accordance with a difference between an initial inclination angle immediately before a vehicle body inclination angle changes during movement of the vehicle and an inclination angle at a stop position. Item 5. The vehicle brake device according to Item 4.   The gradient difference determining means estimates the load applied to at least one of the front axle and the rear axle according to the inclination angle of the vehicle body detected by the inclination angle detection means, and detects and estimates by actual measurement. The vehicle brake device according to any one of claims 1 to 4, wherein when the load and the detected load are different from each other by a predetermined value or more, it is determined that there is a road surface gradient difference between the wheel bases. . The vehicle brake device according to claim 6, wherein the stop state maintaining unit corrects the target braking force in accordance with a deviation amount between the estimated load and the detected load.

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