JP3796930B2 - Electric brake device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem with a conventional electrically powered brake, i.e., a current always flows to a driving motor during the normal braking operation, leading to large consumption of electricity. SOLUTION: This electrically operated brake uses an electric actuator 6 that contains an irreversible mechanism (a worm gear 12 for the case shown in the figure). A pressure force sensor 15 is further installed for detecting a pressure force on a brake pad 5. When the condition that the absolute differential value corresponding to the output from the sensor 15 is less than the first threshold, and the output from a pedal effort sensor 2 or the pressure force sensor 15 is greater than the second threshold is proved, the power supply to a motor 11 is stopped, blocking the recovery of a brake piston 8 with a worm gear 12. Thus the braking force is kept. The keeping of the braking force is canceled when the absolute differential value of the output from the depression sensor 2 exceeds the third threshold.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric brake device for a vehicle (a so-called by-wire type brake device), and more particularly, to an electric brake device with an improved effect of reducing power consumption.
[0002]
[Prior art]
The electric brake device described above controls the electric actuator to generate a driving force according to the sensor output based on the output of the sensor that detects the brake operation force or the brake operation amount, and the friction material is transferred to the rotor by the electric actuator. The braking force is applied to the wheel by pressing.
[0003]
As a conventional example of this type of brake device, a vehicle state detector detects whether or not the vehicle is in a stopped state, and when stopped, the brake pad is returned by an irreversible mechanism incorporated in the power transmission unit of the electric actuator. The system disclosed in Japanese Patent Application Laid-Open No. 4-108058, which prevents the electric actuator from being turned on and stops the energization of the electric actuator, and the electric system by incorporating a mechanical brake operating mechanism in the electric actuator The brake actuator disclosed in Japanese Utility Model Laid-Open No. 5-22234, which maintains the braking function even in the event of failure and can also be used as a parking brake, or the electric actuator when the disc pressing force by the brake pad reaches a predetermined value Instead, the voltage is applied to the piezoelectric element and the increase in the required braking force is increased by the expansion force of the element. And the like apparatus of JP-A-7-89420 discloses a disclosure as cover.
[0004]
[Problems to be solved by the invention]
The system disclosed in Japanese Patent Laid-Open No. 4-108058 can stop energization of the electric actuator when the parking brake is applied, but it is necessary to always supply power to the electric actuator during braking during normal braking (when the vehicle is not stopped). , Power consumption can not be suppressed. An electric brake device using a motor as a drive source generally consumes several tens to several hundreds of watts, so that power consumption when the vehicle is not stopped increases. In addition, since a large current continues to flow through the motor during braking, there is still a problem in life (reliability).
[0005]
The same applies to the brake actuator disclosed in Japanese Utility Model Laid-Open No. 5-22234.
[0006]
In addition, the device disclosed in Japanese Patent Laid-Open No. 7-89420 solves the problem that a large current continues to flow to the motor during braking because the power supply to the motor stops when the pad pressing force exceeds a predetermined value. Since the piezoelectric element continues to be energized, this also has a problem in power consumption.
[0007]
Accordingly, an object of the present invention is to improve the power consumption of the electric brake device.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, the electric actuator is controlled based on the output of the first sensor that detects the brake operation force or the brake operation amount when the vehicle is stopped and when the vehicle is not stopped , and the friction material is controlled by the electric actuator. In the electric brake device for a vehicle that applies a braking force to the wheel by pressing the rotor, a second sensor that detects the braking force, a differential circuit of the first and second sensor outputs, and a differential value of the second sensor output circuit the absolute value variation range of the braking force is compared with the first threshold value is the absolute value of the derivative, which can be said to be constant, there is no need to hold the braking force to the output of the first sensor or the second sensor the third is the be the absolute value of the differential value intention of the absolute value of the braking force changes of the differential value of the output of the circuit and the first sensor to be compared with the output at which the second threshold is to have been made A circuit for comparing with a value, and an electric actuator when a condition that the absolute value of the differential value of the second sensor output is smaller than the first threshold value and the output of the first sensor or the second sensor is larger than the second threshold value is satisfied And a control circuit for issuing a braking force holding release command when the absolute value of the differential value of the first sensor output is greater than the third threshold, and further, the braking force holding by the electric actuator is At the same time, the electric actuator is not energized when the braking force is held, and the braking force is held when conditions for holding the braking force such as waiting for a signal are met.
[0009]
The second sensor may be a pressing sensor that detects the pressing pressure of the friction material. As this pressure sensor, one using a piezoelectric element or a load cell is well known, and these elements can be used.
[0010]
Since the second sensor output varies depending on the output of the first sensor, a device configuration that substitutes the differential value of the first sensor output instead of the differential value of the second sensor output may be adopted. Since this device does not require the second sensor, it is effective when there is no second sensor or when it is difficult to employ the second sensor. For example, the response of the electric actuator is slow or the command signal changes. Because it may hold the braking force before the actual braking force stabilizes due to reasons such as being too early, it is not suitable for use in applications that require low-response electric actuators or high-speed control. .
[0011]
As a method of holding the braking force, an irreversible actuator is used to prevent the pressing member (for example, a brake piston described later) from returning, and a reversible actuator is accompanied by an electromagnetic brake. A method of stopping the movement of the actuator and preventing the pressing member from returning can be considered.
[0012]
The irreversible actuator is an irreversible mechanism built into the power transmission unit that prevents the return due to the pressing reaction force of the pressing member when the drive motor is stopped, and allows the return when the motor is reverse. Say. Further, the reversible actuator refers to an actuator that allows the return of the pressing member when the motor is stopped.
[0013]
There are two types of electromagnetic brakes, the non-excitation operation type and the excitation operation type. You can choose either one, but in terms of fail-safe, the excitation operation type is more than the non-excitation operation type that locks the braking force when the power supply stops. Is considered better.
[0014]
This electromagnetic brake may be either one that restricts the movement of the rotating shaft of the motor integrally with the motor of the actuator or one that restricts the movement of the power transmission element provided in the operation transmission path from the motor.
[0015]
When an irreversible actuator is used, energization of the irreversible actuator is stopped by a braking force holding command, and energization of the irreversible actuator is started by a braking force holding release command.
[0016]
When a non-excitation actuating electromagnetic brake and a reversible actuator are used in combination, the deenergization actuating electromagnetic brake and the reversible actuator are de-energized with a braking force hold command and de-energized with a brake force hold release command. When energizing the actuating electromagnetic brake and the reversible actuator is started, on the other hand, when using the excitation actuating electromagnetic brake and the reversible actuator in combination, the energizing electromagnetic brake is energized with a braking force holding command, In addition, the energization of the reversible actuator is stopped, the energization of the excitation actuated electromagnetic brake is stopped by the brake force holding release command, and the energization of the reversible actuator is started.
[0017]
[Action]
Since the differential value of the second sensor output represents the amount of change in braking force, when this value is smaller than a certain threshold value (first threshold value), it can be said that the braking force is constant within the variation range, and the braking force retention is not. It seems possible. In the present invention, this braking force is held mechanically to suppress power consumption.
[0018]
The conventional device consumes electric power while the braking force is constant. On the other hand, the device according to the present invention consumes almost no electric power while holding the braking force for the device that holds the braking force using an irreversible actuator and the device that uses a reversible actuator with a non-excitation actuating electromagnetic brake. In addition, since the energization to the motor is stopped during that time, the actuator life is also improved.
[0019]
Moreover, what hold | maintains braking force using the reversible actuator with an excitation action | operation type electromagnetic brake should just energize an electromagnetic brake. When holding the braking force by energizing the electric actuator, the electric energy of several hundred W is consumed, but the power consumption of the electromagnetic brake is about several tens W, which is much smaller. Reduction can be achieved.
[0020]
In addition, with irreversible actuators, control is complicated because the braking force is increased / decreased by forward / reverse rotation of the motor, which may cause problems with responsiveness and control accuracy. The problem is also solved.
[0021]
If no braking force is generated, it is not necessary to maintain the braking force. Therefore, the output of the first sensor representing the braking operation force or the amount of braking operation or the output of the second sensor representing the braking force is a constant threshold (second Only when greater than (threshold), the braking force holding system constituted by the elements characterizing the invention is activated. In addition, when the absolute value of the differential value of the first sensor output exceeds a certain threshold value (third threshold value), the intention to change the braking force is displayed, so that the holding of the braking force is released. .
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the electric brake device of the present invention will be described.
[0023]
FIG. 1 is a cross-sectional view of the device of the first embodiment. In FIG. 1, reference numeral 1 denotes a brake pedal, and reference numeral 2 denotes a pedal force sensor (first sensor) that detects a pedal force applied to the brake pedal 1. The pedal force sensor 2 may be replaced with a stroke sensor that detects the depression amount of the brake pedal. Reference numeral 3 denotes an electronic control unit that inputs information from various sensors to control the electric actuator 6. Reference numeral 4 denotes a disc rotor. Reference numeral 5 denotes a brake pad (friction material) that presses against both end surfaces of the disc rotor 4 with the electric actuator 6.
[0024]
The electric actuator 6 is inserted into the cylinder hole of the caliper 7 (the floating type in the figure) and is prevented from rotating by the brake pad 5 (the rotation can be prevented by the caliper). The brake piston 8 and the ball fixed to the brake piston 8 The main element is a nut 9, a screw shaft 10 screwed into the ball nut 9, an electric motor 11, and a worm gear 12 including a worm 12 a and a worm wheel 12 b, and the motive power of the motor 11 passes through the worm gear 12. Then, the screw shaft 10 is rotated, and the brake piston 8 is propelled by the rotation of the screw shaft so that the brake pad 5 is pressed against the disc rotor 4. In the figure, 13 is a housing for housing the worm gear 12, 14 is a bearing for supporting the screw shaft 10, and the housing 13 is fixed to the caliper 7.
[0025]
The electric actuator 6 is the same as that disclosed in Japanese Patent Laid-Open No. 4-108025, and the reverse rotation of the screw shaft 10 is prevented by the worm gear 12 when the motor 11 is stopped, whereby the brake piston 8 is pressed. Hold on point. Since this actuator 6 is an irreversible actuator having the worm gear 12 as an irreversible mechanism, the braking force is released or reduced by reversing the motor 11 with a reverse voltage mark.
[0026]
The electric brake device shown in the figure is provided with a pressing sensor 15 for detecting the pressing pressure of the brake pad 5 between the brake piston 8 and the inner brake pad 5 pressed by the brake piston 8. The pressure sensor 15 may be provided between the outer claw of the caliper 7 and the brake pad on the outer side.
[0027]
In the electronic control unit 3, as shown in FIG. 3, the absolute values of the differential values of the differential circuits 21 and 22 for differentiating the outputs of the pedal force sensor 2 and the pressure sensor 15 and the output of the pressure sensor 15 are controlled. The output of the circuit 23 and the treading force sensor 2 (which may be the pressing sensor 15) to be compared with a first threshold value that is a criterion for determining whether or not the power is constant is a criterion for determining whether or not braking is being performed. 2 The circuit 24 for comparing with the threshold value , the absolute value of the differential value of the pedal force sensor 2 is compared with the third threshold value as a reference for confirming the intention to change the braking force, and the absolute value of the differential value of the output of the pressure sensor 15 It is determined whether or not a condition that the value is smaller than the first threshold value and the output of the pedal force sensor 2 (or the press sensor 15) is larger than the second threshold value is satisfied, and the electric actuator 6 shown in FIG. Command to hold power and The control circuit 26 issues a release command of the braking force holding is provided when the absolute value of the differential value of the output of the sensor 2 is greater than the third threshold value.
[0028]
In the apparatus of FIG. 1, when a braking force holding command signal is output, the motor 11 is deenergized, and this state is maintained until a braking force holding release command is issued.
[0029]
FIG. 2 shows an apparatus according to the second embodiment. This electric brake device uses a reversible actuator (shown in Japanese Utility Model Publication No. 5-22234) for transmitting the rotation of the motor 11 to the screw shaft 10 through the pinion gear 16 and the spur gear 17 as the electric actuator 6. The movement of the actuator is stopped by the electromagnetic brake 18 to prevent the return of the brake piston 8.
[0030]
Since this apparatus uses a reversible actuator, when the energization to the motor 11 is stopped when the electromagnetic brake 18 is not operating, the brake piston 8 is pushed back by reversing the screw shaft 10. The braking force can be released without performing reverse rotation control, and control is easier than in the apparatus of FIG. 1 employing an irreversible actuator, and responsiveness and control accuracy are easily improved. The other configuration is substantially the same as that of the apparatus shown in FIG. 1 except that the ball nut 9 is inserted into the brake piston 8 so as to be slidable in the axial direction and not relatively rotatable. The ball nut 9 can move in the brake piston 8 to a position where the sleeve 19 compresses the spring 20 and hits the end wall of the brake piston 8.
[0031]
In the case where a non-excitation operation type is used as the electromagnetic brake 18, this device stops the energization of the motor 11 and the electromagnetic brake 18 when a command for holding the braking force is issued from the electronic control unit 3, and the braking force is maintained. The energization of both is resumed by the release command. Further, when using the electromagnetic brake 18 of the excitation operation type, energization to the electromagnetic brake 18 is started by a command for holding the braking force, and energization to the motor 11 is stopped. Keep the state back.
[0032]
The example apparatus uses a motor with an electromagnetic brake that restrains the movement of the rotating shaft of the motor 11 with an electromagnetic brake, but the electromagnetic brake 18 is provided at the left end of the screw shaft 10 in FIG. You may make it restrain rotation of this.
[0033]
The electric brake device of the present invention may detect whether the vehicle is stopped or not using a wheel speed sensor or the like, and may perform the following control based on this detection signal.
[0034]
(1) When the vehicle is stopped, the first threshold value is made larger than the value when the vehicle is not stopped in order to make the braking force holding system work even if the braking force varies to some extent.
(2) When the vehicle is stopped, if the differential value of the first sensor output is negative (depressurization side), the braking force holding system is activated, and when the first sensor output becomes lower than a certain threshold value, or the accelerator pedal is operated by the accelerator sensor. Stops the function of the braking force holding system when a stepping on is detected.
[0035]
A device using an irreversible actuator and a device using a reversible actuator with a non-excitation actuating type electromagnetic brake consume zero power while holding the braking force, and therefore can apply a parking brake for a long time.
[0036]
The control circuit of the apparatus of this system, for example, operates the electric actuator 6 using the engine off signal as a command signal, and holds the braking force when the output of the pressing sensor 15 reaches a predetermined value, and the engine is turned on or the accelerator is operated. The parking brake can be automatically applied by providing a function of releasing the holding of the braking force by a pedal depression signal. When the parking brake is applied by such a method, it is preferable that the power is automatically shut off by a timer signal or the like when the braking force is maintained.
[0037]
1 and 2, when the pressure sensor 15 is not provided, the differential value of the output of the pedal force sensor 2 (or stroke sensor) can be substituted for the differential value of the output of the sensor 15. it can.
[0038]
【The invention's effect】
As described above, the electric brake device of the present invention holds the braking force by mechanically restraining the movement of the electric actuator when the conditions capable of holding the braking force are satisfied. In addition, it is possible to suppress power consumption by operating the braking force holding system even during normal braking.
[0039]
Particularly, those using an irreversible actuator and those using a combination of a non-excitation actuating type electromagnetic brake and a reversible actuator have a great effect of improving power consumption because the power consumption during holding of the braking force is almost zero. In addition, since the electric actuator is not energized while the braking force is maintained, the life of the actuator is improved and the reliability is increased.
[0040]
In addition, a combination of a reversible actuator and an electromagnetic brake is superior in response and control accuracy compared to a combination of using an irreversible actuator.
[0041]
Furthermore, the combination of the excitation actuated electromagnetic brake and the reversible actuator consumes electric power due to the electromagnetic brake while holding the braking force, but this device also does not need to energize the motor while holding the braking force. Compared with, an effect of reducing power consumption can be obtained. In addition, this device does not lock the braking force when the power fails, and is superior to a device using a non-excitation operation type electromagnetic brake in terms of fail-safe.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of an electric brake device according to the present invention. FIG. 2 is a sectional view of another embodiment. FIG. 3 is a block diagram of a circuit provided in an electronic control unit.
DESCRIPTION OF SYMBOLS 1 Brake pedal 2 Treading force sensor 3 Electronic controller 4 Disc rotor 5 Brake pad 6 Electric actuator 7 Caliper 8 Brake piston 9 Ball nut 10 Screw shaft 11 Motor 12 Worm gear 13 Housing 14 Bearing bearing 15 Press sensor 16 Pinion gear 17 Spur gear 18 Electromagnetic brake 19 Sleeve 20 Spring 21, 22 Differentiation circuit 23-25 Comparison circuit 26 Control circuit

Claims (5)

The electric actuator (6) is controlled based on the output of the first sensor (2) for detecting the brake operation force or the brake operation amount when the vehicle is stopped and when the vehicle is not stopped , and the friction material (5) is moved by the electric actuator (6). In the vehicle electric brake device that applies a braking force to the wheels by pressing against the rotor (4),
Wherein a second sensor for detecting a braking force (15), first and second sensor (2, 15) the output of the differentiating circuit (21, 22), the absolute value of the second sensor (15) a differential value of the output The output of the circuit (23), the first sensor (2) or the second sensor (15) for comparing with the first threshold value, which is the absolute value of the differential value, which can be said to have a constant braking force variation range, is used as the braking force. The absolute value of the differential value of the output of the circuit (24) and the first sensor (2) that is compared with the second threshold value that is the output that is not required to be held is said to indicate the intention to change the braking force. The absolute value of the differential value of the output of the second sensor (15) and the circuit (25) that compares with the third threshold value that is the absolute value of the differential value is smaller than the first threshold value, and the first sensor or the second sensor When the condition that the output is larger than the second threshold is satisfied, the electric actuator (6) A control circuit (26) for issuing a power holding command, and for issuing a braking force holding release command when the absolute value of the differential value of the first sensor output is greater than the third threshold, and further, a control by the electric actuator (6). An electric brake device for a vehicle characterized in that power is held mechanically and the electric actuator (6) is not energized when the braking force is held . The electric actuator (6) is controlled based on the output of the first sensor (2) for detecting the brake operation force or the brake operation amount when the vehicle is stopped and when the vehicle is not stopped , and the friction material (5) is moved by the electric actuator (6). In the vehicle electric brake device that applies a braking force to the wheels by pressing against the rotor (4),
The differential circuit (21) of the output of the first sensor (2) and the absolute value of the differential value of the output of the first sensor (2) are the absolute values of the differential values that can be said that the variation range of the braking force is constant . It is not necessary to hold the braking force for the output of the first sensor (2) and the circuit for comparing the first threshold value and the third threshold value, which is the absolute value of the differential value for which the intention to change the braking force is indicated. than the being is a circuit for comparing the output a of the second threshold value, the absolute value of the first sensor (2) the differential value of the output is smaller than the first threshold value, and the first sensor (2) output a second threshold value When a large condition is satisfied, a braking force holding command is issued to the electric actuator (6). When the absolute value of the differential value of the first sensor (3) output is larger than the third threshold value, a braking force holding cancellation command is issued. And a control circuit for providing an electric actuator (6). Braking force holding vehicle electric braking device is characterized in that so as not energized in the electric actuator when the braking force holding together is done mechanically (6).  3. An irreversible actuator is used as the electric actuator (6), the energization of the irreversible actuator is stopped by a braking force holding command, and the energizing of the irreversible actuator is started by a braking force holding release command. The electric brake device for vehicles as described.  A reversible actuator with a non-excitation actuating electromagnetic brake (18) is used as the electric actuator (6), and energization of the non-exciting actuating electromagnetic brake (18) and the reversible actuator (6) is stopped by a braking force holding command. The vehicle electric brake device according to claim 1 or 2, wherein energization of the non-excitation actuating electromagnetic brake (18) and the reversible actuator (6) is started by a release command for holding the braking force.  As the electric actuator (6), a reversible actuator with an excitation actuating electromagnetic brake (18) is used, and the excitation actuating electromagnetic brake (18) is energized by a braking force holding command, and the reversible actuator (6) is energized. The vehicle electric brake according to claim 1 or 2, wherein the energization of the excitation actuated electromagnetic brake (18) is stopped by the brake force holding release command and the energization of the reversible actuator (6) is started. apparatus.

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