JP2013035513A - Electric parking brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric parking brake device capable of determining a load target value corresponding to the gradient of a road surface in a short period of time.SOLUTION: The electric parking brake device includes a parking brake, an actuator, a gradient sensor, a load sensor and a control section. The control section performs load value determination for determining an actuator target load value and driving control for controlling the actuator so that the load by the actuator reaches the actuator target load value on the basis of the output of the load sensor. The control section determines an inflection point in the time series of gradient values from the gradient sensor in the load value determination and performs filter processing for calculating an estimated gradient by estimating the convergent value of gradient values on the basis of time series of gradient values after the inflection point and a predetermined filter coefficient to determine the actuator target load value on the basis of the estimated gradients.

Description

  The present invention relates to an electric parking brake device having an actuator.

  The parking brake is used for braking the vehicle. An actuator is used as means for driving the parking brake (for example, Patent Document 1).

  The actuator supplies a load to the parking brake via a cable. When the actuator pulls the cable, the parking brake is activated, and a braking force corresponding to the supplied load is applied to the wheels of the vehicle. The vehicle can be kept stopped by the braking force of the parking brake.

  On the other hand, the parking brake is released when the actuator extends the cable.

JP 2006-306301 A

  The electric parking brake device drives a parking brake that performs braking when the vehicle is parked or stopped using an electric actuator such as a motor.

  In such a case, it is necessary to set a large braking force on a slope such as a slope to prevent the vehicle from starting to move.

  As such an electric parking brake device, there has been proposed an electric parking brake device having a control means for automatically pulling and operating a cable by an electric motor when a vehicle speed from a vehicle speed sensor is zero for a predetermined time. (For example, Patent Document 1).

  However, when additional pulling is performed, the cable is loaded by the additional load of the actuator, so the durability of the cable is required, and it is necessary to monitor the cable elongation. It is desirable to drive the actuator with a load of. In addition, since the parking brake may be activated immediately after the vehicle stops, the load value of the actuator cannot be determined before the operation of the electric parking brake device is completed. As a result, it becomes a discount.

  The present invention provides an electric parking brake device that can be operated by changing a load on a slope and can determine a load value before the operation of the electric parking brake device is completed.

  The electric parking brake device disclosed herein includes a parking brake that brakes the wheels of the vehicle, an actuator that operates or releases the parking brake, a gradient sensor, a load sensor, and a control unit that controls the actuator. .

  The control unit performs load value determination for determining the actuator target load value and drive control for controlling the actuator so that the load by the actuator reaches the actuator target load value based on the output of the load sensor.

  Further, in the load value determination, the control unit determines an inflection point in a time series of gradient values from the gradient sensor, and based on a time series of gradient values after the inflection point and a predetermined filter coefficient, A filter process for calculating the estimated gradient is performed by estimating the convergence value of the gradient value, and the actuator target load value is determined based on the estimated gradient.

  In this electric parking brake device, even if the variation of the gradient value continues, the convergence value of the gradient value is estimated and the estimated gradient is calculated. An actuator target load value is determined based on the estimated gradient. As a result, the actuator target load value suitable for the road surface gradient can be determined in a shorter time than when the actuator target load value is determined after the fluctuation of the gradient value is settled.

  As described above, even when the parking brake is operated immediately after the vehicle stops, the electric parking brake device can be driven by changing the load value on the slope without increasing or decreasing.

1 is a schematic configuration diagram of a vehicle equipped with an electric parking brake device according to an embodiment. It is the figure which showed the output value of the gradient sensor and the vehicle speed sensor. It is a schematic structure figure of an electric parking brake device concerning an embodiment. It is a block diagram of an electronic control unit. It is the flowchart which showed the operation | movement of estimation gradient determination. It is the figure which showed the time series of the output value of a gradient sensor. It is a block diagram of an infinite impulse response filter processing unit. It is the flowchart which showed operation | movement of the electric parking brake apparatus which concerns on embodiment. It is a time chart which showed operation of an electric parking brake device concerning an embodiment. It is the figure which showed the relationship between a gradient and an actuator target load value. It is the figure which showed the output value of the gradient sensor in a downhill.

  Embodiments will be described with reference to the drawings. However, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Configuration of electric parking brake device]
"overall structure"
The electric parking brake device according to the embodiment is mounted on a vehicle. As shown in FIG. 1, the vehicle 1 has an electric parking brake device 2 and wheels 3. The electric parking brake device 2 includes a parking brake 4, an actuator 5, a cable 6, a gradient sensor 7, a vehicle speed sensor 8, an operation switch 9, and an electronic control device 20.

  The parking brake 4 brakes the wheel 3. The parking brake 4 is attached to the left and right rear wheels of the wheels 3. In the present embodiment, the parking brake 4 is disposed so as to be able to contact a brake drum (not shown) and an inner peripheral surface of the brake drum, and is pressed against the brake drum by being pressed (not shown). And have. As long as the parking brake 4 can prevent the vehicle 1 from moving, another mechanism may be used.

  The actuator 5 activates or releases the parking brake 4. The actuator 5 supplies a load to the parking brake 4 via the cable 6. When the actuator 5 pulls the cable 6, the brake shoe of the parking brake 4 is pressed against the brake drum. Thereby, the parking brake 4 brakes the wheel 3. A state where the parking brake 4 is braking the wheel 3 is a state where the parking brake 4 is operated. On the other hand, when the actuator 5 extends or loosens the cable 6, the brake shoe of the parking brake 4 is separated from the brake drum. This state is a state in which the parking brake 4 is released.

  The cable 6 is a so-called Bowden cable, and transmits a load between the actuator 5 and the parking brake 4.

  The gradient sensor 7 is a device for detecting the gradient of the road surface on which the vehicle 1 rides. The gradient sensor 7 outputs a gradient value. The slope value includes road surface slope information. In the present embodiment, the gradient sensor is an acceleration sensor and outputs a time series of signals corresponding to the detected acceleration. Here, the gradient sensor 7 of the present embodiment does not directly measure the gradient of the road surface, but indirectly detects the gradient of the road surface by detecting the inclination of the vehicle 1 with respect to the vertical direction. The gradient sensor 7 only needs to be able to detect the gradient of the road surface, and may be a device other than the acceleration sensor. For example, the gradient sensor 7 may detect the inclination of the vehicle 1 using a gyro, or may detect the inclination of the vehicle 1 from the position of the surface of the liquid sealed in the container.

  The vehicle speed sensor 8 detects the speed of the vehicle 1. In the present embodiment, the vehicle speed sensor 8 detects the vehicle speed by measuring the rotational speed of the axle. Note that the speed of the vehicle 1 may be detected by individually measuring the rotational speed of each wheel based on the rotational speeds of the front, rear, left, and right wheels 3.

  The operation switch 9 receives an operation for instructing the operation or release of the parking brake 4. The operation switch 9 is disposed at a position where the driver can easily operate. When a predetermined operation is input to the operation switch 9, a process for operating or releasing the parking brake 4 is started. In this embodiment, the operation switch 9 has a lever, and the lever is arranged at the ON position, the OFF position, or the intermediate position. When the lever is disposed at the ON position, the operation of the actuator 5 is instructed to operate the parking brake 4. When the lever is arranged on the OFF side, a process for releasing the parking brake 4 is started. When the lever is arranged at the intermediate position, the parking brake 4 is kept stopped.

  The electronic control device 20 controls the operation of the electric parking brake device 2. The operation of the electronic control unit 20 will be described later. An actuator 5, a gradient sensor 7, a vehicle speed sensor 8, and an operation switch 9 are connected to the electronic control device 20. Note that information detected by each sensor as an analog signal is converted into a digital signal so that processing in the electronic control unit 20 is possible.

《Gradient sensor output value》
Here, an output value of the gradient sensor 7 when the vehicle 1 stops on a road surface with a gradient (that is, a slope) will be described. When the vehicle 1 is decelerated by the foot brake (main brake), the vehicle 1 eventually stops. When the driver who determines that the vehicle 1 has stopped turns on the operation switch 9, the actuator 5 is activated and the parking brake 4 brakes the wheel 3. At this time, the braking force applied to the wheel 3 by the parking brake 4 needs to be large enough to maintain the stop state of the vehicle 1. That is, in order to stop the vehicle 1 that is about to move along the road surface having the gradient S, a braking force larger than the braking force required on a flat road is required.

  Therefore, in order to prevent the vehicle 1 from starting to move on a road surface having a gradient, it is conceivable to set the target value of the load supplied to the parking brake 4 to a large value. The magnitude of the load supplied at this time is determined on the assumption of the largest gradient among the actually assumed gradients of the road surface. That is, when the vehicle 1 is on a flat road or a road surface with a small gradient, an extra load is supplied to the parking brake 4. Thereby, even if it is a case where the vehicle 1 stops on the road surface with a gradient, the movement start of the vehicle 1 can be prevented.

  It is also conceivable to control the load supplied to the parking brake 4 in two stages. For example, when the vehicle 1 starts to move, a load is additionally supplied to the parking brake 4 to brake the vehicle 1. In such control, in order to supply an additional load to the parking brake 4, it is necessary to rapidly increase the tensile force acting on the cable 6.

  In these controls, the actuator 5 applies an extra or additional tensile force to the cable 6 in order to supply an extra load to the parking brake 4. This operation of the actuator 5 is referred to as additional pulling. By performing the additional pulling, a large tensile force is applied to the cable 6. Therefore, the extension of the cable 6 is larger than when no additional pulling is performed. The elongation of the cable 6 is an irreversible deformation caused by repeatedly applying a tensile force to the cable 6. Comparing the case where the extension of the cable 6 is large and the case where the extension is small, in order to supply the same load to the parking brake 4, the actuator 5 needs to pull the cable 6 having a large extension excessively by the difference in elongation. Similarly, when the parking brake 4 is released, it is necessary to consider the extension amount of the cable 6. Therefore, in the case of adopting a mechanism mainly composed of additional pulling, the extension of the cable 6 is monitored and the operation of the actuator 5 is controlled according to the amount of extension, and the control of the actuator 5 becomes complicated.

  On the other hand, only a necessary load may be supplied from the actuator 5 to the parking brake 4 according to the gradient of the road surface. Thereby, the frequency of the extra pull can be reduced. In order to set a necessary load, it is necessary to detect the gradient of the road surface using the gradient sensor 7.

  Here, the behavior of the output value of the gradient sensor 7 when the vehicle 1 stops will be described with reference to FIG. In FIG. 2, the horizontal axis corresponds to time, the left vertical axis corresponds to the output value of the gradient sensor 7, and the right vertical axis corresponds to the output value of the vehicle speed sensor 8. The reference value F is an output value of the gradient sensor 7 when the vehicle 1 is stationary on a flat road. The value U is the output value of the gradient sensor 7 when the vehicle 1 is stationary on the road surface having the gradient S.

  As shown in FIG. 2, it is determined that the time when the vehicle speed becomes zero is the time when the vehicle 1 stops. When the vehicle speed becomes zero, the vehicle 1 stops in the traveling direction, but since inertia works, the vehicle 1 temporarily takes a forward leaning posture. The vehicle 1 continues to shake for a while until it settles in a stable posture. At this time, the gradient sensor 7 detects the shaking of the vehicle 1. That is, the output value of the gradient sensor 7 varies according to the shake of the vehicle 1. Specifically, the output value of the gradient sensor 7 fluctuates around a value U corresponding to the gradient S. The output value of the gradient sensor 7 converges to a value U (hereinafter also referred to as a convergence value U) as the stop state continues and the shaking of the vehicle 1 stops.

  In this way, the output value of the gradient sensor 7 can be acquired at the time when the shake of the vehicle 1 is almost settled, and the road surface gradient can be detected based on the output value. However, since it takes time for the output value of the gradient sensor 7 to stabilize to the convergence value, the output value of the gradient sensor 7 may not be stable to the convergence value when the driver turns on the operation switch 9. . In this case, the presence or absence and the magnitude of the gradient cannot be accurately detected. At this time, one of the possible methods for reliably braking the vehicle 1 is to perform additional pulling in order to supply a load assuming a maximum gradient to the parking brake 4.

  Therefore, in order to operate the parking brake 4 immediately after the vehicle 1 stops and avoid the extra pull, it is necessary to detect the gradient of the road surface in a short time. In order to solve this problem, the electric parking brake device 2 according to the embodiment has a configuration described below.

《Peripheral configuration》
As shown in FIG. 3, in addition to the above-described configuration, the electric parking brake device 2 includes a motor rotation sensor 11, a load sensor 12, a vehicle CAN (Controller Area Network) control communication bus 13, an operation lamp 14, have. The actuator 5 has an electric motor 10.

  The motor 10 drives the cable 6. When the motor 10 pulls the cable 6 in the operation direction, a load is supplied to the parking brake 4. Further, the parking brake 4 is released when the motor 10 extends the cable 6 in the releasing direction. The operation of the motor 10 is controlled by the electronic control unit 20.

  The motor rotation sensor 11 counts the number of rotations of the motor 10. The number of rotations counted by the motor rotation sensor 11 is input to the electronic control unit 20 and used for controlling the motor 10.

  The load sensor 12 detects the load supplied to the parking brake 4. In the present embodiment, the load supplied to the parking brake 4 means the magnitude of the tensile force applied to the cable 6. The load detected by the load sensor 12 is input to the electronic control unit 20 and used for controlling the motor 10.

  The vehicle CAN control communication bus 13 performs data transfer between devices and control signal transfer. The vehicle CAN control communication bus 13 is connected to the gradient sensor 7, the vehicle speed sensor 8, and the electronic control device 20. The operation lamp 14 is turned on or off according to the state of the parking brake 4. When the parking brake 4 is in an activated state, the operation lamp 14 is turned on. When the parking brake 4 is released, the operation lamp 14 is turned off.

<< Configuration of electronic control unit >>
FIG. 4 is a block diagram of the electronic control unit 20. The electronic control device 20 includes a control unit 30 and a nonvolatile storage unit 40. The control unit 30 includes a low-pass filter processing unit 31, a memory unit 32, an inflection point detection unit 33, an infinite impulse response filter processing unit 34, an estimated gradient determination unit 35, and a target value determination unit 36. A motor control unit 37, a vehicle speed determination unit 38, and a mode determination unit 39. In the following, the infinite impulse response is also expressed as IIR (Infinite Impulse Response).

  The control unit 30 is an arithmetic device and executes processing for realizing the functions of the electronic control device 20. In the present embodiment, the control unit 30 is a CPU (Central Processing Unit), and executes a process defined in the program by reading a predetermined program.

  The non-volatile storage unit 40 is a non-volatile storage device that stores setting data of the electronic control device 20 and a program executed by the control unit 30. In the present embodiment, the nonvolatile storage unit 40 is a ROM (Read Only Memory).

  The low-pass filter processing unit 31 processes the output value of the gradient sensor 7 and removes high-frequency components such as noise. The memory unit 32 temporarily stores data processed by the control unit 30. For example, the memory unit 32 temporarily stores the output value of the gradient sensor 7 processed by the low-pass filter processing unit 31. In the present embodiment, the memory unit 32 is a RAM (Random Access Memory). The inflection point detection unit 33 detects an inflection point in the time series of the output values of the gradient sensor 7. The IIR filter processing unit 34 performs IIR filter processing using the output value of the gradient sensor 7 and a predetermined filter coefficient. The estimated gradient determination unit 35 acquires the calculated value output from the IIR filter processing unit 34, and evaluates the fluctuation range of the calculated value within a predetermined time. Further, the estimated gradient determination unit 35 determines an estimated gradient.

  The target value determination unit 36 determines an actuator target load value. The actuator target load value is a target value of the load supplied from the actuator 5 to the parking brake 4. The motor control unit 37 controls the motor 10. The number of rotations of the motor 10 is counted by the motor rotation sensor 11 and input to the motor control unit 37. Further, the load value detected by the load sensor 12 and the actuator target load value determined by the target value determination unit 36 are input to the motor control unit 37.

  The motor control unit 37 performs drive control in order to operate the parking brake 4. That is, the motor control unit 37 included in the control unit 30 controls the actuator 5 so that the load reaches the actuator target load value. In the drive control, the motor control unit 37 controls the actuator 5 based on the load value detected by the load sensor 12, the rotation speed of the motor 10, and the actuator target load value. Specifically, when the parking brake 4 is operated, the motor 10 is controlled by the motor control unit 37 so that the actuator target load value is supplied from the actuator 5 to the parking brake 4. On the other hand, when the parking brake 4 is released, the motor 10 is controlled by the motor control unit 37 so that the cable 6 is fed out in the release direction.

  The vehicle speed determination unit 38 determines the vehicle speed of the vehicle 1 based on the output value of the vehicle speed sensor 8. The mode determination unit 39 determines whether or not to calculate an estimated gradient described later.

  In this embodiment, the inflection point detection unit 33, the IIR filter processing unit 34, the estimated gradient determination unit 35, and the target value determination unit 36, that is, the load value determination for determining the actuator target load value by the control unit 30 is executed. The These functional blocks work in concert to perform the load value determination.

[Method of determining the estimated gradient]
Next, a method of determining the estimated gradient from the output value of the gradient sensor 7 will be described using FIG.

《Determination method flow》
In step S101, the vehicle speed determination part 38 determines whether the speed of the vehicle 1 is 2 km / h or less. The vehicle speed determination unit 38 acquires the output value of the vehicle speed sensor 8 and determines the vehicle speed. When the vehicle speed is 2 km / h or less, it is determined that the vehicle 1 has sufficiently decelerated, and the flow proceeds to step S102. On the other hand, if the vehicle speed is not 2 km / h or less, the process proceeds to step S105.

  In step S <b> 102, the memory unit 32 starts saving the output value of the gradient sensor 7. Here, in the activated state of the electric parking brake device 2, the gradient sensor 7 always detects the inclination of the vehicle 1 and outputs an output value to the electronic control device 20. The output value of the gradient sensor 7 is processed by the low-pass filter processing unit 31. When it is determined in step S101 that the speed of the vehicle 1 is 2 km / h or less, the memory unit 32 starts saving the output value of the gradient sensor 7. That is, the time series of the output value of the gradient sensor 7 is processed by the low-pass filter processing unit 31 and then stored in the memory unit 32.

  In step S103, the vehicle speed determination part 38 determines whether the stop state of the vehicle 1 is continuing. Specifically, the vehicle speed determination unit 38 measures the duration of the state where the vehicle speed is 0 km / h (that is, the state where the vehicle speed is zero), and when the duration reaches a specified time, the vehicle 1 is stopped. It is determined that it continues. Here, the vehicle speed determination unit 38 determines that the vehicle speed is 0 km / h when the output value of the vehicle speed sensor 8 is below a predetermined threshold value. If the stop state of the vehicle 1 continues, the flow proceeds to step S104, otherwise the flow returns to step S101.

  In step S104, the mode determination unit 39 enables the gradient determination mode.

  In step S105, the mode determination unit 39 invalidates the gradient determination mode. That is, when the vehicle speed does not become 2 km / h or less, the gradient determination mode becomes invalid.

  In step S106, the control unit 30 determines whether the gradient determination mode is valid. If the gradient determination mode is valid, the flow proceeds to step S107. On the other hand, when the gradient determination mode is invalid, the estimated gradient is not determined and the flow ends.

  In step S107, the inflection point detector 33 determines an inflection point in the time series of the output value of the gradient sensor 7. If an inflection point is detected, the flow proceeds to step S108. If the inflection point is not detected, the flow proceeds to step S109, and the output value of the gradient sensor 7 is acquired by the control unit 30 and stored in the memory unit 32. Thereafter, the flow returns to step S107, and the inflection point is determined. Steps S107 and S109 are repeatedly executed until an inflection point is detected.

  In step S108, the IIR filter processing unit 34 executes IIR filter processing. The IIR filter processing unit 34 performs filter processing on the time series after the inflection point in the time series of the output values of the gradient sensor 7 and outputs the calculated value. The output value of the gradient sensor 7 is read from the memory unit 32 and subjected to filter processing. The calculated value output from the IIR filter processing unit 34 is stored in the memory unit 32.

In step S <b> 110, the estimated gradient determination unit 35 determines the stability of the calculated value output from the IIR filter processing unit 34. Specifically, the estimated gradient determination unit 35 acquires a time series of calculated values from the memory unit 32 and determines whether or not the calculated values satisfy a stability condition. In the present embodiment, the stability condition is that the state where the fluctuation range of the calculated value is smaller than 0.3 m / s ² continues for 100 milliseconds or longer. The fluctuation range is derived by calculating the difference between the maximum value and the minimum value of the calculated values stored in the memory unit 32. If the stability condition is satisfied, the flow proceeds to step S112. If the condition is not satisfied, the flow proceeds to step S111.

  In step S <b> 111, the control unit 30 acquires the output value of the gradient sensor 7 and stores it in the memory unit 32. Thereafter, the flow returns to step S108 again. Steps S108 and S111 are repeatedly executed until the stability condition is satisfied in step S110.

  In step S112, the estimated gradient determination unit 35 determines an estimated gradient. The latest calculated value output from the IIR filter processing unit 34 is adopted as the estimated gradient. Since the estimated gradient adopted is a value that satisfies the stability condition, the convergence value U of the output value of the gradient sensor 7 is approximated. That is, the estimated gradient approximates the output value of the gradient sensor 7 when the vehicle 1 has stopped shaking. As described above, the control unit 30 including the IIR filter processing unit 34 and the estimated gradient determination unit 35 estimates the convergence value U of the gradient value that is the output value of the gradient sensor 7.

The estimated gradient is used to evaluate the presence and magnitude of the gradient. Specifically, by performing a predetermined conversion on the estimated gradient, an amount representing the ratio between the vertical distance and the horizontal distance can be obtained. Note that the estimated gradient may be zero. For example, when the calculated value of the IIR filter processing unit 34 is below a predetermined threshold value, the estimated gradient is determined to be zero.
As described above, the estimated gradient is determined.

<Calculation method of estimated gradient>
Here, the method for calculating the estimated gradient will be described in more detail with reference to FIGS. 6 and 7.

  As shown in FIG. 6, among the time series of the output values of the gradient sensor 7, the time series after the inflection point I is used for calculating the estimated gradient.

  The inflection point I is a point that appears first after the vehicle speed reaches 2 km / h or less, among the points where the time series of the output value of the gradient sensor 7 changes from decrease to increase or from increase to decrease. The inflection point I appears as the vehicle 1 stops. When the vehicle 1 stops, the vehicle 1 swings forward due to inertia, and the time series of the output value of the gradient sensor 7 varies greatly due to this swing. As a result, the inflection point I appears. The inflection point I is detected by monitoring the time series of the output value of the gradient sensor 7. In order to detect the inflection point I, the output value of the gradient sensor 7 is stored in the memory unit 32 from the time when the vehicle speed reaches 2 km / h or less as described above. However, the control unit 30 acquires the output value of the gradient sensor 7 at a constant sampling period ST regardless of the vehicle speed. In this embodiment, this sampling period ST is 20 milliseconds.

  The output value of the gradient sensor 7 at the inflection point I is X (1), and the number of output values (sampling number) of the gradient sensor 7 acquired after the inflection point I is N (N is an integer of 1 or more). And At this time, the output value of the gradient sensor 7 after the inflection point I is X (n) (where n = 1, 2,..., N), the time series of output values {X (1), X (2 ), X (3),. . . , X (N)} is represented as {X (N)}. For example, in the example illustrated in FIG. 6, the output values X (1) to X (6) are acquired from the gradient sensor 7 at the sampling times P1 to P6, respectively. In this case, since N = 6, {X (6)} = {X (1), X (2), X (3), X (4), X (6)}. Based on the time series {X (N)} and a predetermined filter coefficient, the IIR filter processing unit 34 executes IIR filter processing.

FIG. 7 shows a block diagram of the IIR filter processing unit 34. The IIR filter processing unit 34 includes an adder 51, a multiplier 52, a delay unit 53, and a multiplier 54.
The adder 51 outputs the sum of input values. The multiplier 52 outputs a product of the input value and 1 / n. The delay unit 53 outputs the input value with a delay of one round. The multiplier 54 outputs the product of the input value and n-1.

The IIR filter processing unit 34 calculates a calculated value Y (n) (where n = 1, 2,...) Based on a time series {X (N)} of output values of the gradient sensor 7 and a predetermined filter coefficient. ., N). Specifically, the output equation of the IIR filter processing unit 34 is expressed as (Equation 1).

Further, based on (Expression 1), Y (n) is also expressed as (Expression 2).

  Similar to the time series {X (N)}, a sequence of calculated values Y (n) is expressed as a calculated value sequence {Y (N)}. As shown in (Expression 1) and (Expression 2), the filter coefficient multiplied by {X (N)} is determined in advance. The filter coefficient in this embodiment is (n-1) / n and 1 / n in (Expression 1) or 1 / n in (Expression 2). Here, “predetermined” filter coefficient means that the filter coefficient is determined according to a predetermined relationship. Therefore, the predetermined filter coefficient is a concept including not only a constant but also a filter coefficient defined by the mathematical formula (n−1) / n or 1 / n.

  A time series {X (N)} of output values of the gradient sensor 7 is processed by the low-pass filter processing unit 31 and stored in the memory unit 32. Each time the sampling cycle ST elapses, the sampling number N increases by one. When the output value of the gradient sensor 7 is newly acquired, the output value is added to the time series {X (N)}. The calculated value Y (N) is calculated using the time series {X (N)} stored in the memory unit 32. In the present embodiment, the time series {X (N)} is arithmetically averaged by filter processing, and Y (N) is calculated. In this way, by repeating the acquisition of the output value of the gradient sensor 7 and the calculation of the calculated value Y (N), a calculated value sequence {Y (N)} as a time series is obtained. The calculated value sequence {Y (N)} is stored in the memory unit 32.

[Operation of the electric parking brake device]
Next, the overall operation of the electric parking brake device 2 will be described with reference to FIG. The electric parking brake device 2 is in an activated state and is waiting for an operation of the operation switch 9.

<Operation flow>
In step S201, the control unit 30 determines whether the operation switch 9 is ON. If it is determined that the operation switch 9 is ON, the flow proceeds to step S202. If the operation switch 9 is not ON, the electric parking brake device 2 ends its operation and returns to a state of waiting for the operation of the operation switch 9 again. At this time, the parking brake 4 returns to the released state.

  In step S202, the actuator 5 operates. Specifically, the motor control unit 37 controls the motor 10 of the actuator 5 to rotate the motor 10. When the motor 10 rotates, the cable 6 is pulled in the operating direction, and a load is supplied to the parking brake 4.

  At this time, the target value determination unit 36 acquires an initial value stored in advance in the nonvolatile storage unit 40 and sets it as an actuator target load value. The motor control unit 37 controls the motor 10 so that the load supplied to the parking brake 4 reaches the initial value.

  In step S203, the target value determination unit 36 determines whether the estimated gradient has already been determined. Specifically, the target value determination unit 36 determines whether or not the determined estimated gradient is stored in the memory unit 32. If the estimated gradient has already been determined, the flow proceeds to step S204. On the other hand, if the estimated gradient has not been determined, the flow proceeds to step S207.

  In step S204, the target value determination unit 36 determines whether or not there is a gradient. The target value determination unit 36 acquires the estimated gradient from the memory unit 32 and determines whether the estimated gradient is zero. If the estimated gradient is zero, it is determined that there is no gradient on the road surface, and the flow proceeds to step S206. If the estimated gradient has a value other than zero, it is determined that there is a gradient, and the flow proceeds to step S205.

  In step S205, the target value determination unit 36 sets an actuator target load value. The target value determination unit 36 determines an actuator target load value based on the determined estimated gradient. Here, information indicating the relationship between the estimated gradient and the actuator target load value is stored in advance in the nonvolatile storage unit 40, and the actuator target load value is determined based on the estimated gradient. Specifically, a plurality of actuator target load values are stored in the nonvolatile storage unit 40 as gradient target load values. Furthermore, according to the magnitude of the estimated gradient, the estimated gradient and a specific target load value at the time of gradient are associated with each other, and a target load value at the time of gradient corresponding to the estimated gradient is determined. The target value determination unit 36 acquires the estimated gradient from the memory unit 32 and acquires the gradient target load value corresponding to the estimated gradient from the nonvolatile storage unit 40. Then, the target value determining unit 36 sets the obtained gradient target load value as the actuator target load value.

  In step S206, the target value determination unit 36 sets an actuator target load value. However, since there is no gradient, the target value determination unit 36 sets the standard target load value as the actuator target load value. The standard target load value is stored in advance in the nonvolatile storage unit 40 as the actuator target load value when there is no gradient, and is read by the target value determination unit 36.

  In step S207, the target value determination unit 36 sets an actuator target load value. However, since the estimated gradient is not determined, the target value determination unit 36 sets the maximum load value as the actuator target load value. The maximum load value is stored in advance in the nonvolatile storage unit 40 and is read by the target value determination unit 36.

  In step S208, the motor control unit 37 determines whether or not the load supplied from the actuator 5 to the parking brake 4 has reached the actuator target load value. A signal representing the load supplied to the parking brake 4 is input from the load sensor 12 to the control unit 30, more specifically to the motor control unit 37. Based on the signal input from the load sensor 12, the motor control unit 37 compares the value of the load supplied to the parking brake 4 with the actuator target load value and makes a determination. If the supplied load has reached the actuator target load value, the flow proceeds to step S209; otherwise, the flow returns to step S201.

  In step S209, the motor control unit 37 stops the actuator 5. That is, the motor control unit 37 stops the motor 10 of the actuator 5. Thereby, drive control of the actuator 5 by the control part 30 is completed. In this state, the parking brake 4 is operated, and the wheel 3 is braked by the parking brake 4. When the drive control of the actuator 5 is completed, the control unit 30 turns on the operation lamp 14. The driver can know that the parking brake 4 is operating by confirming that the operation lamp 14 is lit. When the parking brake 4 is released, the control unit 30 turns off the operation lamp 14.

<Operation and time lapse>
Next, an example of the operation of the electric parking brake device 2 will be described over time using FIG. FIG. 9A shows the vehicle speed. FIG. 9B shows the output value of the gradient sensor 7. FIG. 9C shows the calculated value output from the IIR filter processing unit 34. FIG. 9D shows the sampling number N. FIG. 9E shows the state of the operation switch 9. FIG. 9F shows the state of the actuator 5.

  At time t0, the vehicle speed determination unit 38 determines that the vehicle speed has reached 2 km / h or less. The output value of the gradient sensor 7 after the time t0 is stored in the memory unit 32.

  At time t1, the vehicle speed determination unit 38 determines that the vehicle speed has reached 0 km / h.

  At time t2, an inflection point I appears in the time series of the output of the gradient sensor 7. Also, time t2 is the starting point for counting N samples.

  At time t3, the gradient determination mode is validated by the mode determination unit 39. The vehicle speed determination unit 38 detects that the state of the vehicle speed of 0 km / h continues for a predetermined specified time V1 from time t1. Based on the detection result of the vehicle speed determination unit 38, the mode determination unit 39 validates the gradient determination mode. Further, the IIR filter processing unit 34 starts IIR filter processing.

  At time t4, the control unit 30 detects that the operation switch 9 is turned on. Further, the actuator 5 is operated by being controlled by the motor control unit 37.

At time t5, the control unit 30 determines the estimated gradient. An actuator target load value is determined based on the estimated gradient. Here, the estimated gradient determination unit 35 determines the stability of the calculated value output from the IIR filter processing unit 34 during the period V2 immediately before time t5. That is, it is detected that a state where the fluctuation range of the calculated value is smaller than the reference value W continues for at least the period V2. As described above, in the present embodiment, the reference value W of the fluctuation range is 0.3 m / s ² and the period V2 is 100 milliseconds.

  After time t5, the processing by the IIR filter processing unit 34 is not executed. However, in FIG. 9C and FIG. 9D, the case where the IIR filter processing is continuously executed after time t5 is indicated by a two-dot chain line.

  At time t6, the actuator 5 is stopped by being controlled by the motor control unit 37.

<Target actuator load value>
Here, the actuator target load value will be described with reference to FIG. FIG. 10 is a graph schematically showing the relationship between the road surface gradient and the actuator target load value. The horizontal axis in FIG. 10 represents the slope of the road surface. The gradient here is represented by the ratio of the horizontal distance to the vertical distance. T0 is an initial value, T1 is a standard target load value, and T4 is a maximum load value. T2 and T3 are gradient target load values and are intermediate values between T1 and T4. T1 and T4 are also target load values at the time of gradient.

  At the time when the actuator 5 operates, the initial value T0 is set as the actuator target load value. When it is determined that there is no gradient, the target value determination unit 36 sets the standard target load value T1 as the actuator target load value. If it is determined that there is a gradient, any one of the gradient target load values T1, T2, T3, and T4 is set as the actuator target load value according to the magnitude of the gradient.

  Specifically, when the gradient derived from the estimated gradient is greater than 6% and equal to or less than 12%, the target value determination unit 36 selects a gradient target load value T2 corresponding to the gradient in this range. Read from the nonvolatile storage unit 40. Then, the target value determining unit 36 sets the read gradient target load value T2 as the actuator target load value.

[Effects of Embodiment]
The above embodiment can be expressed as follows.

  (1) The electric parking brake device 2 controls the parking brake 4 that brakes the wheels 3 of the vehicle 1, the actuator 5 that operates or releases the parking brake 4, the gradient sensor 7, the load sensor 12, and the actuator 5. And a control unit 30. The control unit 30 performs load value determination for determining the actuator target load value and drive control for controlling the actuator 5 so that the load from the actuator 5 reaches the actuator target load value based on the output of the load sensor 12. In determining the load value, the control unit 30 determines the inflection point I in the time series of the output value of the gradient sensor 7 and is predetermined as the time series {X (N)} of the output values after the inflection point I. Based on the filter coefficient, filter processing for calculating an estimated gradient by estimating a convergence value of the output value is performed, and an actuator target load value is determined based on the estimated gradient.

  In the electric parking brake device 2, the convergence value U of the gradient value is estimated and the estimated gradient is calculated even if the output value of the gradient sensor 7 continues to fluctuate. Then, an actuator target load value is calculated based on the estimated gradient. As a result, the actuator target load value suitable for the road surface gradient can be determined in a shorter time than when the actuator target load value is determined after the fluctuation of the gradient value is settled.

  Therefore, even when the actuator 5 is actuated immediately after the vehicle 1 stops, the parking brake 4 can be actuated by changing the actuator target load value in accordance with the gradient of the road surface without increasing or decreasing.

  (2) In the electric parking brake device 2, the control unit 30 executes the IIR filter process in the filter process.

  As a result, the calculated value obtained by the IIR filter process can be brought close to the convergence value U in a short time while reducing the number of used configuration blocks.

  (3) The electric parking brake device 2 includes a vehicle speed sensor 8 that detects the speed of the vehicle 1. The control unit 30 determines the inflection point I in the time series of the output value of the gradient sensor 7 after the speed of the vehicle 1 detected by the vehicle speed sensor 8 reaches 2 km / h or less.

  Here, when the vehicle 1 is sufficiently decelerated, the acceleration of the vehicle 1 does not change abruptly under normal circumstances. That is, the time series of the output value of the gradient sensor 7 changes relatively slowly. When the vehicle 1 stops in such a state, the inflection point I generally appears significantly in the time series of the output values of the gradient sensor 7. Thereby, in the state which the vehicle 1 fully decelerated, the determination of the inflection point I can be performed more reliably. As a result, the accuracy of determining the estimated gradient is improved.

  (4) In this electric parking brake device 2, the control unit 30 sets an initial value T0 in advance as the actuator target load value, determines the presence or absence of a gradient based on the estimated gradient, and if there is a gradient, the estimated gradient The gradient target load value T1, T2, T3, or T4 corresponding to is determined, the gradient target load value T1, T2, T3, or T4 is set as the actuator target load value, and if there is no gradient, the actuator As the target load value, a standard target load value T1 that is a value when there is no gradient is set.

  Thus, by setting the initial value T0 in advance as the actuator target load value of the load, some value is set as the actuator target load value. Since the actuator target load value is set, the actuator 5 can be controlled. That is, the actuator 5 can be operated even when the estimated gradient is not determined. Thereby, the time from when the vehicle 1 is stopped until the actuator 5 is operated can be shortened. Specifically, the actuator 5 can be operated even when the estimated gradient is not determined when the operation switch 9 is turned on by the driver.

  In addition, since an appropriate actuator target load value is selected according to the presence or absence and magnitude of the gradient, the frequency of the extra pull can be reduced.

  (5) In the electric parking brake device 2, the drive control is completed after the actuator target load value is determined based on the estimated gradient. Thereby, the actuator 5 is driven and controlled in accordance with the presence or absence and the magnitude of the gradient, so that the frequency of the extra pull can be reduced.

[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention. In particular, a plurality of embodiments and modifications described in this specification can be arbitrarily combined as necessary.

  (1) Each value in the above-described embodiment can be replaced with another value whose characteristics are correlated. For example, in the above-described embodiment, the output value of the vehicle speed sensor 8 is an hourly speed, but the rotational speed of the axle may be used as a value representing the vehicle speed. In the above-described embodiment, the output value of the gradient sensor 7 is acceleration, but an angle may be used as an amount representing the inclination of the vehicle 1.

  (2) In the above-described embodiment, in order to determine the stability of the calculated value output from the IIR filter processing unit 34, the period V2 for monitoring the fluctuation range of the calculated value is provided. However, as a method for determining the stability of the calculated value, a method other than providing the period V2 may be used.

For example, the stability may be determined using two calculated values that are continuous in the time direction. Specifically, when the calculated value Y (N) is obtained next to the calculated value Y (N−1), the difference between Y (N−1) and Y (N) is calculated. When the difference is a predetermined value (for example, 0.3 m / s ² ) or less, it may be determined that the calculated value is stable.

  (3) In the above-described embodiment, the estimated gradient is calculated using the time series starting from the inflection point I among the time series of the output values of the gradient sensor 7. However, it is also possible to calculate the estimated gradient using a time series starting from a time different from the inflection point I.

  FIG. 11 shows a time series of output values of the gradient sensor 7, a time series of output values of the vehicle speed sensor 8, a time series C1, and a time series C2 when the road surface is a downhill. The time series C1 is a time series of calculated values output from the IIR filter processing unit 34 in the electric parking brake device 2 according to the above-described embodiment. On the other hand, the time series C2 is a time series of calculated values output from the IIR filter processing unit 34 in the electric parking brake device according to another embodiment. The value D (hereinafter also referred to as the convergence value D) is an output value of the gradient sensor 7 corresponding to the downhill on which the vehicle 1 rides.

  In the electric parking brake device according to another embodiment, the IIR filter process is executed using only the output values after the start point I2 among the output values of the gradient sensor 7. That is, the inflection point I1 and the output value of the gradient sensor 7 acquired between the inflection point I1 and the start point I2 are not used for the IIR filter processing. Even when such processing is performed, the time series C2 can be converged to the convergence value D earlier than the time series of the output values of the gradient sensor 7. Thereby, since the estimated gradient can be determined in a shorter time, the determination of the actuator target load value can be accelerated.

  As shown in FIG. 11, the time series C2 fluctuates more violently than the time series C1, and the convergence to the convergence value D is slower than the time series C1. From this, in order to obtain a more advantageous effect, the time series starting from the inflection point I1 (or I) that appears first when the vehicle 1 stops among the time series of the output values of the gradient sensor 7 is used. Preferably used to perform IIR filtering.

  In addition, as shown in FIG. 11, the time series of the output values of the gradient sensor 7 includes the first inflection point I3, the second inflection point I4, and the inflection points after the inflection point I1. Three inflection points I5 appear. The time series C1 substantially converges to the convergence value D between the second inflection point I4 and the third inflection point I5. Therefore, in order to calculate the estimated gradient, it is preferable to use a time series {X (N)} including at least the output value of the gradient sensor 7 after the second inflection point I4.

  (4) In the above-described embodiment, the processing in the IIR filter processing unit 34 is completed when the stability of the calculated value is detected. However, the IIR filter processing unit 34 may be controlled using conditions other than the stability of the calculated value.

  For example, the sampling number N may be determined in advance. The number of samplings at this time is a fixed value M (M is an integer of 1 or more). The IIR filter processing unit 34 outputs the calculated value Y (M) when M times of processing are completed. The output Y (M) is determined as the estimated gradient. At this time, the fixed value M is determined so that Y (M) becomes a value close to the convergence value U. As described above, even if a configuration in which IIR filter processing is performed only a predetermined number of times is used, it is possible to estimate the convergence value of the output value of the gradient sensor 7.

  Further, when the number of samplings is determined in advance, the process of (Equation 2) may be realized by a finite impulse response filter process.

  (5) In the above-described embodiment, whether the gradient determination mode is valid or invalid is determined based on only the vehicle speed in step S101, but other conditions may be used as a reference.

  For example, when a state in which the output value of the gradient sensor 7 is not input to the electronic control device 20 continues for a certain period of time, it may be determined that a problem has occurred in the gradient sensor 7 and the gradient determination mode may be invalidated.

Further, the validity / invalidity of the gradient determination mode may be determined based on the output value of the gradient sensor 7. For example, in the time series of output values of the gradient sensor 7 stored in the memory unit 32, the difference between the maximum value and the minimum value of the output values acquired before the inflection point I is calculated. When the difference is 0.3 m / s ² or more, the gradient determination mode is invalidated. Under this condition, it is possible to exclude the case where the output value of the gradient sensor 7 fluctuates excessively, so that the reliability of the estimated gradient can be improved.

  In the above-described embodiment, the vehicle speed in step S101 is 2 km / h. However, it is only necessary to confirm that the vehicle 1 has decelerated. I do not care. For example, a value in the range of 2 km / h to 5 km / h can be used as a reference.

  (6) In the above embodiment, when it is determined that there is no gradient, the standard target load value T1 is set as the actuator target load value. In this case, the initial value T0 is set as the actuator target load value. It may be set. That is, in this configuration, even when it is determined that there is no gradient, the target value determination unit 36 maintains a state where the initial value T0 is set as the actuator target load value.

  In the present embodiment, the initial value T0 is the minimum actuator target load value, but the initial value T0 may not be smaller than the gradient target load values T1 to T4. For example, the initial value T0 may be a value between the standard target load value T1 and the gradient target load value T2, or the initial value T0 may be equal to the maximum load value T4.

  (7) Each process of the above-described embodiment may be realized by hardware, or may be realized by software (including a case where it is realized together with an OS (Operating System), middleware, or a predetermined library). Good. Furthermore, each process of the above-described embodiment may be realized by a mixed process of software and hardware.

  For example, the inflection point detection unit 33, the IIR filter processing unit 34, the estimated gradient determination unit 35, and the target value determination unit 36, which are functional blocks that determine the load value, are used as a load value determination unit by a single hardware or device. It may be realized. And you may implement | achieve the motor control part 37 which performs drive control with one hardware or apparatus as a drive control part.

  Needless to say, when the processing in the above-described embodiment is realized by hardware, it is necessary to adjust timing for performing each processing. In the above-described embodiment, for the convenience of explanation, details of timing adjustment of various signals that occur in actual hardware design are omitted.

  Further, the execution order of the processing methods in the above-described embodiments is not necessarily limited to the description of the above-described embodiments, and the execution order may be changed without departing from the gist of the invention.

  The electric parking brake device disclosed herein can set the load supplied to the parking brake to a value suitable for the slope of the road surface even when the actuator is operated immediately after the vehicle stops. Since the frequency can be reduced, it is useful in the field of an electric parking brake device having an actuator.

2 Electric parking brake device 4 Parking brake 5 Actuator 7 Gradient sensor 8 Vehicle speed sensor 12 Load sensor 30 Control unit

Claims (5)

An electric parking brake device comprising: a parking brake that brakes wheels of a vehicle; an actuator that operates or releases the parking brake; a gradient sensor; a load sensor; and a control unit that controls the actuator.
The control unit performs load value determination for determining an actuator target load value, and drive control for controlling the actuator so that a load from the actuator reaches the actuator target load value based on an output of the load sensor. Done
In the load value determination, the control unit determines an inflection point in a time series of gradient values from the gradient sensor, and determines a time series of the gradient values after the inflection point and a predetermined filter coefficient. On the basis of performing a filtering process for calculating an estimated gradient by estimating a convergence value of the gradient value, and determining the actuator target load value based on the estimated gradient;
An electric parking brake device characterized by that. The control unit performs infinite impulse response filter processing in the filter processing.
The electric parking brake device according to claim 1. A vehicle speed sensor for detecting the speed of the vehicle;
The control unit performs the determination of the inflection point in the time series of the gradient value from the gradient sensor after the vehicle speed detected by the vehicle speed sensor reaches a predetermined speed or less.
The electric parking brake device according to claim 1 or 2. The controller sets an initial value for the actuator target load value in advance, determines the presence or absence of a gradient based on the estimated gradient, and if there is a gradient, sets a target load value at the time of gradient corresponding to the estimated gradient. The target load value at the time of gradient is set as the actuator target load value, and when there is no gradient, the standard target load value or the initial value that is a value when there is no gradient is used as the actuator target load value. Set
The electric parking brake device according to any one of claims 1 to 3. The controller completes the drive control after the actuator target load value is determined based on the estimated gradient.
The electric parking brake device according to any one of claims 1 to 4.