WO2017154790A1

WO2017154790A1 - Linear actuator

Info

Publication number: WO2017154790A1
Application number: PCT/JP2017/008565
Authority: WO
Inventors: 山崎　達也; 村松　誠
Original assignee: Ntn株式会社
Priority date: 2016-03-09
Filing date: 2017-03-03
Publication date: 2017-09-14
Also published as: JP6621689B2; JP2017159782A

Abstract

Provided is a linear actuator capable of eliminating problems in terms of layout and inhibiting fade phenomena and the like when the linear actuator is mounted on a vehicle or the like. An abnormality determination means (108) determines if there is an abnormality in each load detection means (Sa, Sb). When the two load detection means (Sa, Sb) are both normal, a normality control unit (110) controls a motor (30) using the summed value of loads detected by the two load detection means (Sa, Sb). If it is determined that one of the load detection means Sa (Sb) is abnormal, an abnormality control unit (111) estimates the load being produced in two linear motion mechanisms from the motor rotation angle, the motor current, and the load detected by the normal load detection means Sb(Sa). The abnormality control unit (111) controls the motor (30) using the estimated load values.

Description

Linear actuator

Related applications

This application claims the priority of Japanese Patent Application No. 2016-045735 filed on Mar. 9, 2016, which is incorporated herein by reference in its entirety.

The present invention relates to a linear actuator applied to, for example, an electric brake device for an automobile.

An electric brake device that controls a motor according to a target pressing force of a brake determined from a brake operation amount and an actual pressing force value acquired by a pressing force sensor has been proposed (Patent Document 1).

JP 2000-213575 A

In Patent Document 1, the friction pad is pressed against the brake disk by one actuator. For this reason, when the required brake load is large, the radial dimension of the actuator (linear motion mechanism) becomes large, which causes a problem in layout. In addition, even if the required pressing force can be generated by a linear motion mechanism with a small radial dimension, the pressure does not act evenly on the entire friction pad, thereby inducing a fade phenomenon or promoting the progress of wear of the friction pad. There are things to do. Patent Document 1 does not disclose a control method when one friction pad is pressed by two actuators.

An object of the present invention is to provide a linear motion actuator for an electric brake device that can eliminate layout problems and suppress a fade phenomenon or the like when the electric brake device is mounted on a vehicle or the like. .

Hereinafter, in order to facilitate understanding, description will be made with reference to the reference numerals of the embodiments.

The linear actuator 31 according to the first configuration of the present invention includes:
One motor 30;
Two

linear motion mechanisms

33a and 33b, each including one piston 26a (26b), and two

linear motion mechanisms

33a and 33b for converting the rotational motion of the motor 30 into the linear motion of the piston 26a (26b). 33b,
A control device 100 for controlling the motor 30;
Two load detection means Sa and Sb, each of which detects the axial load of the corresponding linear motion mechanism 33a (33b) of the two

linear motion mechanisms

33a and 33b. , Sb,
The control device 100 controls the motor 30 using the total value of the loads detected by the two load detection means Sa and Sb.

According to this configuration, the rotational motion of one motor 30 is converted into linear motion of the two

pistons

26a and 26b of the two

linear motion mechanisms

33a and 33b. The two load detection means Sa and Sb detect the axial loads of the two

linear motion mechanisms

33a and 33b, respectively. The control device 100 controls the motor 30 using the total value of the loads detected by the load detection means Sa and Sb. In this way, more accurate load control can be performed by controlling the motor 30 based on the total value of the loads detected by the two load detecting means Sa and Sb.

In the case of a one-motor, two-piston type linear motion actuator, if only one piston load is detected, the timing at which the load is generated by the two pistons may differ, so accurate load control can be performed. Can not. On the other hand, according to this configuration, the control device 100 performs, for example, feedback control that causes the load value detected by the two load detecting means Sa and Sb to follow the given command value. More accurate load control can be performed. The feedforward control may be performed when the detected values such as the vehicle speed and the motor current satisfy the predetermined conditions. The predetermined condition is an arbitrary condition determined by design or the like, and is determined, for example, by obtaining an appropriate condition by one or both of a test and a simulation.

When this linear motion actuator 31 is applied to an electric brake device, more accurate load control can be performed, so that a fade phenomenon or the like can be suppressed. Since the direct acting actuator 31 is of a single motor type or a two piston type, for example, it is possible to reduce the size in the radial direction as compared with a structure in which two pistons are respectively driven by two motors. Therefore, it is possible to solve the layout problem when the linear actuator 31 is mounted on the vehicle.

Current detection means Sc for detecting the current of the motor 30;
Rotation angle detecting means Sd for detecting the rotation angle of the motor 30;
The control device 100 includes:
An abnormality determination means 108 for determining whether or not each of the two load detection means Sa and Sb is abnormal according to a predetermined condition;
When it is determined by the abnormality determination means 108 that the two load detection means Sa and Sb are not abnormal, the motor 30 is used by using the sum of the loads detected by the two load detection means Sa and Sb, respectively. A normal control unit 110 for controlling
When the abnormality determination unit 108 determines that one of the load detection units Sa (Sb) is abnormal, the load detected by the other load detection unit Sb (Sa) that is not determined to be abnormal, the current Axial directions respectively generated in the two

linear motion mechanisms

33a and 33b according to a predetermined condition based on the motor current detected by the detection means Sc and the motor rotation angle detected by the rotation angle detection means Sd. And an abnormal-time control unit 111 that controls the motor 30 using a total value of the estimated loads.

Instead of the motor rotation angle detected by the rotation angle detection means Sd, the rotation angle of the first or second rotation shaft 32a (32b) of the first or second linear motion mechanism 33a (33b) is detected. The input shaft angle θ _A (θ _B ) of the first or second piston 26a (26b) detected by the first or second rotation angle sensor Se (Sf) may be used for load estimation.

The predetermined condition in the abnormality determination unit 108 and the predetermined condition in the abnormality control unit 111 are conditions arbitrarily determined by design or the like, for example, by one or both of a test and a simulation. Determined for the appropriate conditions.

According to these configurations, the abnormality determination means 108 determines the abnormality of each load detection means Sa and Sb. When the two load detection means Sa and Sb are both normal, the normal control unit 110 controls the motor 30 using the total value of the loads detected by the two load detection means Sa and Sb. When it is determined that any one of the load detection means Sa (Sb) is abnormal, the abnormality control unit 111 detects the load detected by the other normal load detection means Sb (Sa), the motor current, and From the motor rotation angle, the load generated in each of the two

linear motion mechanisms

33a and 33b is estimated. The abnormal time control unit 111 controls the motor 30 by using the estimated value of the total load. That is, the abnormal time control unit 111 controls the entire actuator using the normal load detecting means Sb (Sa), the motor current and the motor rotation angle. In this way, even if an abnormality occurs in one of the load detection means Sa (Sb), the load generated in each of the two

linear motion mechanisms

33a and 33b is obtained using the value of the normal load detection means Sb (Sa). Can be estimated, and redundancy is improved.

A command value may be input to the control device, and the abnormal time control unit may perform feedback control that causes the sum of the estimated loads to follow the command value. In this case, more accurate load control can be performed.

An electric brake device according to one configuration of the present invention includes the linear actuator 31. In this case, the electric brake device can be mounted on a vehicle having a large required brake load. In addition, the layout problem can be solved and the fade phenomenon and the like can be suppressed.

Any combination of at least two configurations disclosed in the claims and / or the specification and / or drawings is included in the present invention. In particular, any combination of two or more of each claim in the claims is included in the present invention.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims. In the accompanying drawings, the same reference numerals in a plurality of drawings indicate the same or corresponding parts.
It is a front view of the electric brake device concerning a 1st embodiment. It is a side view from the paper left side of the electric brake device of FIG. It is the III-III sectional view taken on the line of FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is the VV line end view of FIG. It is the VI-VI line end view of FIG. It is the VII-VII sectional view taken on the line of FIG. It is the VIII-VIII sectional view taken on the line of FIG. It is a figure which shows schematically an example of the load detection means of the electric brake device of FIG. It is a block diagram of the control system of the electric brake device of FIG. It is a block diagram which shows the detailed structure of the control apparatus of the electric brake device of FIG. It is a graph which shows the relationship between the input shaft angle and piston load in one piston of the electric brake device of FIG. It is a graph which shows the relationship between the input shaft torque and piston load in the piston of FIG. It is a figure which shows the relationship between the motor rotation angle of each electric brake device of FIG. 1, and each piston load. It is a flowchart which shows each process of the control apparatus of FIG. 11 in steps. It is a figure which shows the relationship between the motor rotation angle and each piston load of the electric brake device which concerns on 2nd Embodiment.

A linear actuator according to a first embodiment of the present invention and an electric brake device including the linear actuator will be described with reference to FIGS. This electric brake device is mounted on a vehicle. An electric brake device is provided for each wheel of the vehicle. As shown in FIG. 1, each electric brake device includes a caliper 6, an electric linear actuator 31, a brake rotor 1, an inboard side friction pad 7, and an outboard side friction pad 8. The linear actuator 31 includes a control device 100. The vehicle is provided with a caliper 6 so as to surround the outer peripheral portion of the brake rotor 1 for each wheel. The linear motion actuator 31 drives the inboard friction pad 7 to contact and separate from the brake rotor 1.

As shown in FIG. 2, the caliper 6 has a claw portion 22, a piston housing portion 23, and an outer shell portion 24. The outer portion 24 connects the claw portion 22 and the piston housing portion 23 on the outer diameter side of the brake rotor 1. As shown in FIG. 7, the inboard side friction pad 7 and the outboard side friction pad 8 are arranged between the claw portion 22 and the piston housing portion 23 so as to face each other in the axial direction.

In this specification, in a state where this electric brake device is mounted on a vehicle, the outer side in the vehicle width direction of the vehicle is referred to as the outboard side, and the central side in the vehicle width direction of the vehicle is referred to as the inboard side.

As shown in FIG. 1, a claw portion 22 is provided at the end portion of the caliper 6 on the outboard side. The claw portion 22 faces the side surface on the outboard side of the brake rotor 1 in the axial direction. The outboard side friction pad 8 is supported by the claw portion 22.

As shown in FIG. 4, the piston housing portion 23 is provided with first and second

piston housing holes

25a and 25b. These

piston accommodation holes

25a and 25b are provided at predetermined intervals in the circumferential direction of the brake rotor 1, as shown in FIG. As shown in FIG. 4, the first and

second pistons

26a and 26b are accommodated in the first and second

piston accommodation holes

25a and 25b, respectively.

The first and

second pistons

26a and 26b are arranged in parallel so as to press the friction pad 7 on the inboard side at two locations separated in the circumferential direction of the brake rotor 1 (FIG. 2). As shown in FIG. 1, the inboard friction pad 7 faces the inboard side surface of the brake rotor 1 in the axial direction.

As shown in FIG. 1, a mount 10 is supported on a knuckle 2 in a vehicle. As shown in FIGS. 2 and 3,

pin support pieces

11 and 11 are provided at both ends in the longitudinal direction of the mount 10. Slide pins 5 and 5 extending in parallel with each other in the axial direction are provided at the respective ends of the

pin support pieces

11 and 11. The caliper 6 is supported by these

slide pins

5 and 5 so as to be slidable in the axial direction.

As shown in FIG. 6, during braking, the linear actuator 31 is driven by driving the motor 30, so that the inboard side friction pad 7 comes into contact with the brake rotor 1 as shown in FIG. Is pressed in the axial direction. The caliper 6 slides to the inboard side by the reaction force of the pressing force. As a result, the outboard friction pad 8 supported by the claw portion 22 of the caliper 6 contacts the brake rotor 1. The outboard side friction pad 8 and the inboard side friction pad 7 strongly hold the brake rotor 1 from both sides in the axial direction, so that a braking force is applied to the brake rotor 1.

As shown in FIG. 4, the linear actuator 31 includes one motor 30, a distribution gear mechanism 34, two (first and second)

linear motion mechanisms

33 a and 33 b, and two (first and first). 2) load detecting means Sa and Sb, and a control device 100 (FIG. 1) for controlling the motor 30. A portion of the linear motion actuator 31 excluding the control device 100 (FIG. 1) is attached to the caliper 6. The control device 100 (FIG. 1) is installed in, for example, a vehicle body, but may be mounted on the caliper 6 as long as sufficient durability and environmental performance can be guaranteed. The rotational motion of the motor 30 is transmitted to the two

linear motion mechanisms

33a and 33b via the distribution gear mechanism 34, and is converted into linear motion by the

linear motion mechanisms

33a and 33b, respectively. As a result, the friction pads 7 and 8 (FIG. 1) abut against and separate from the brake rotor 1 (FIG. 1).

A gear case 41 that accommodates the distribution gear mechanism 34 is fixed to the inboard side end of the caliper 6. The motor 30 is fixed to the side plate 42 of the gear case 41. The motor 30 is disposed such that a motor shaft 37 of the motor 30 is parallel to first and second

rotating shafts

32a and 32b described later. Further, as shown in FIG. 3, the motor 30 is a region radially outward of the brake rotor 1 (FIG. 2) from the position of a straight line L connecting the center of the first rotating shaft 32a and the center of the second rotating shaft 32b. Placed in.

As shown in FIG. 4, the distribution gear mechanism 34 has an input gear 35, a first reduction gear train 36a, and a second reduction gear train 36b. The input gear 35 is concentrically connected to the motor shaft 37 and rotates integrally with the motor shaft 37. The first reduction gear train 36a decelerates the rotation of the input gear 35 and transmits it to the first rotation shaft 32a. The second reduction gear train 36b decelerates the rotation of the input gear 35 and transmits it to the second rotation shaft 32b.

The first reduction gear train 36a includes a first distribution gear 38a that meshes with the input gear 35, a first output gear 40a that is concentrically fixed to the first rotation shaft 32a, a first distribution gear 38a, and a first distribution gear 38a. And an intermediate gear 39a that transmits rotation between the output gears 40a. The input gear 35, the first distribution gear 38a, the intermediate gear 39a, and the first output gear 40a have different numbers of teeth. The first reduction gear train 36a sequentially transmits the rotation input from the motor 30 to the input gear 35 to the input gear 35, the first distribution gear 38a, the intermediate gear 39a, and the first output gear 40a. The speed is reduced, and the reduced speed rotation is output from the first output gear 40a to the first rotation shaft 32a.

The second reduction gear train 36b includes a second distribution gear 38b that meshes with the input gear 35, a second output gear 40b that is concentrically fixed to the second rotation shaft 32b, a second distribution gear 38b, and a second distribution gear 38b. And an intermediate gear 39b for transmitting rotation between the two output gears 40b. The input gear 35, the second distribution gear 38b, the intermediate gear 39b, and the second output gear 40b have different numbers of teeth. The second reduction gear train 36b sequentially transmits the rotation input from the motor 30 to the input gear 35 to the input gear 35, the second distribution gear 38b, the intermediate gear 39b, and the second output gear 40b. The speed is reduced, and the reduced speed rotation is output from the second output gear 40b to the second rotation shaft 32b.

The first linear motion mechanism 33a will be described.
Since the second linear motion mechanism 33b has the same configuration as that of the first linear motion mechanism 33a, the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

As shown in FIGS. 7 and 8, the first linear motion mechanism 33a includes a first piston 26a, a plurality of planetary rollers 50, a carrier 51, and a first rotating shaft 32a. The first piston 26a is formed in a cylindrical shape and is provided concentrically with the first rotating shaft 32a. The plurality of planetary rollers 50 are provided at intervals in the circumferential direction between the inner periphery of the first piston 26a and the outer periphery of the first rotating shaft 32a. The carrier 51 holds each planetary roller 50 so that it can rotate and revolve.

Each planetary roller 50 is in rolling contact with the outer periphery of the first rotating shaft 32a. When the first rotation shaft 32a rotates, each planetary roller 50 revolves around the first rotation shaft 32a along the inner periphery of the first piston 26a while rotating around the roller shaft 52.

The first piston 26a is supported by the first piston accommodation hole 25a of the caliper 6 and can slide in parallel with the axial direction. On the inner periphery of the first piston 26a, there is provided a spiral ridge 53 extending obliquely at a predetermined lead angle with respect to the circumferential direction. On the outer circumference of each planetary roller 50, a plurality of circumferential grooves 54 that mesh with the spiral ridges 53 are formed at intervals in the axial direction. The interval between the circumferential grooves 54 adjacent to each other in the axial direction on the outer periphery of each planetary roller 50 is the same as the pitch of the spiral ridges 53. Here, the circumferential groove 54 having a lead angle of 0 degrees is provided on the outer periphery of the planetary roller 50, but instead of the circumferential groove 54, a spiral groove having a lead angle different from that of the spiral protrusion 53 may be provided. .

As shown in FIG. 7, a shaft support member 65 is provided on the inboard side of the first piston accommodation hole 25a of the caliper 6. The shaft support member 65 includes a boss portion and a flange portion extending radially outward from the boss portion. A plurality of rolling bearings 66 are fitted into the boss portions, and the first rotary shaft 32 a is fitted to the inner ring inner diameter surface of each rolling bearing 66. The first rotary shaft 32 a is rotatably supported by the shaft support member 65 via a plurality of rolling bearings 66.

The carrier 51 has a pair of

disks

55 and 56, a connecting portion 57, and a plurality of roller shafts 52. The pair of

disks

55 and 56 oppose each other with a predetermined interval in the axial direction with the planetary roller 50 or the like interposed in the axial direction. The connecting portion 57 connects the pair of

disks

55 and 56. The disc 56 on the inboard side is rotatably supported by the first rotary shaft 32a by a slide bearing 58 fitted between the first rotary shaft 32a. A shaft insertion hole is formed in the center of the disc 55 on the outboard side, and a slide bearing 58 is fitted in this shaft insertion hole. The disc 55 on the outboard side is rotatably supported by the first rotary shaft 32a by a slide bearing 58.

The plurality of roller shafts 52 are supported on the pair of

disks

55 and 56 at regular intervals in the circumferential direction, and support the planetary rollers 50 so as to be rotatable. A plurality of shaft insertion holes 59 are formed in the

disks

55 and 56, respectively. Each shaft insertion hole 59 is a long hole extending in the radial direction. Both end portions of each roller shaft 52 in the axial direction are inserted into the respective shaft insertion holes 59, and the roller shafts 52 are supported so as to be movable in the radial direction within the range of the respective shaft insertion holes 59.

An elastic ring 60 that urges the roller shafts 52 inward in the radial direction is stretched between both ends of the plurality of roller shafts 52 in the axial direction. Each planetary roller 50 is pressed against the outer peripheral surface of the first rotating shaft 32a by the urging force of the elastic ring 60. As the first rotating shaft 32a rotates, each planetary roller 50 in contact with the outer peripheral surface of the first rotating shaft 32a rotates due to contact friction.

The load detection means will be described.
As shown in FIG. 10, the first and second load detecting means Sa and Sb detect the axial loads of the first and second

linear motion mechanisms

33a and 33b (FIG. 4), respectively. The first and second load detection means Sa and Sb have the same configuration, and are provided at the same location in each of the

linear motion mechanisms

33a and 33b (FIG. 4). Therefore, only the first load detection means Sa will be described, and the description of the second load detection means Sb will be omitted.

As shown in FIG. 9, the first load detection means Sa includes, for example, a magnetic sensor 12 and a magnetic target 13. The magnetic target 13 includes, for example, two

permanent magnets

13a and 13a. As shown in FIG. 7, when the friction pad 8 presses the brake rotor 1 in the axial direction, a reaction force to the inboard side acts on the first linear motion mechanism 33a. The first load detection means Sa is provided on the shaft support member 65.

As shown in FIG. 9, the first load detecting means Sa including the sensor 12 and the magnetic target 13 magnetically detects the reaction force of this braking force as an axial displacement amount. As the magnetic sensor 12 for detecting a change in the magnetic field, a cheap Hall IC with a variable dynamic range is preferable. Hall IC is commercially available and has excellent availability. As the magnetic sensor 12, in addition to the Hall IC, for example, a magnetoresistive element or a magnetic impedance element may be applied.

The control device will be described.
FIG. 10 is a block diagram of a control system of this electric brake device. The control device 100 includes an ECU 101 and an inverter device 102. For example, an electric control unit that controls the entire vehicle is applied as the ECU 101 that is a higher-level control unit of the inverter device 102. The brake force command means 101a of the ECU 101 generates and outputs a target brake force command value according to the output of the brake sensor 103a that detects the operation amount of the brake pedal 103. Based on the command value of this braking force, each

linear motion mechanism

33a, 33b (FIG. 4) is driven by the inverter device 102.

As shown in FIG. 11, the inverter device 102 includes a power circuit unit 104, a motor control unit 105 that controls the power circuit unit 104, a warning signal output unit 106, and a current detection unit Sc.

The motor control unit 105 includes a computer, a program executed on the computer, and an electronic circuit. The motor control unit 105 gives a current command to the power circuit unit 104 in accordance with the command value of the brake force given from the brake force command unit 101a. The motor control unit 105 has a function of outputting information about the motor 30 such as detection values and control values to the ECU 101.

The power circuit unit 104 includes an inverter 104b that converts the DC power of the power source Bt into three-phase AC power used to drive the motor 30, and a PWM control unit 104a that controls the inverter 104b. The motor 30 is a three-phase synchronous motor or the like. The motor 30 is provided with a rotation angle detecting means Sd for detecting a rotation angle (motor rotation angle) of a rotor (not shown). The inverter 104b includes a plurality of semiconductor switching elements (not shown), and the PWM control unit 104a performs pulse width modulation on the input current command and gives an on / off command to each of the semiconductor switching elements.

The motor control unit 105 includes a motor drive control unit 107 as a basic control unit and an abnormality determination unit 108. In principle, the motor drive control unit 107 converts the current command based on the voltage value in accordance with the command value of the brake force described above, and gives the motor operation command value including the current command to the PWM control unit 104a of the power circuit unit 104. The motor drive control unit 107 obtains a motor current flowing from the inverter 104b to the motor 30 from the current detection means Sc with respect to the command value of the brake force, and performs current feedback control on the brake command value. Further, the motor drive control unit 107 obtains the motor rotation angle from the rotation angle detection unit Sd, and gives a current command to the PWM control unit 104a so that efficient motor driving according to the motor rotation angle can be performed.

The abnormality determination unit 108 determines whether or not each load detection unit Sa, Sb is abnormal. The abnormality determination means 108 has pad wear amount estimation means 109. This pad wear amount estimating means 109 is a correlation between the current input shaft angle of the first piston 26a (FIG. 4) and the axial load (piston load) of the first linear motion mechanism 33a (FIG. 4). Is compared with a predetermined correlation between the input shaft angle and the piston load when the corresponding friction pads 7 and 8 (FIG. 1) are new (when not worn). The pad wear amount estimation means 109 estimates the wear amount of the friction pads 7 and 8 (FIG. 1) at the present time corresponding to the first piston 26a (FIG. 4) based on the comparison result. The input shaft angle theta _A first piston 26a (Fig. 4), for example, provided by the first rotational angle sensor Se for detecting the rotational angle of the first rotary shaft 32a (FIG. 4). The piston load is a sensor output given from the first load detecting means Sa.

Similarly to the above, the pad wear amount estimating means 109 is configured so that the current input shaft angle of the second piston 26b (FIG. 4) and the axial load (piston load) of the second linear motion mechanism 33b (FIG. 4) are the same. ) Is compared with a predetermined correlation between the input shaft angle and the piston load when the corresponding friction pads 7 and 8 (FIG. 1) are new (when not worn). The pad wear amount estimation means 109 estimates the wear amount of the friction pads 7 and 8 (FIG. 1) at the present time corresponding to the second piston 26b (FIG. 4) based on the comparison result. The input shaft angle θ _B of the second piston 26b (FIG. 4) is given by, for example, a second rotation angle sensor Sf that detects the rotation angle of the second rotation shaft 32b (FIG. 4). The piston load is a sensor output given from the second load detection means Sb. When the distribution gear mechanism 34 as shown in FIG. 4 is used, the rotation angles of the first rotation shaft 32a and the second rotation shaft 32b coincide with the angle of the motor 30, and therefore the first and second rotations. One of the sensors Se and Sf can be omitted.

FIG. 12 is a graph showing the relationship between the input shaft angle and the piston load in one piston of this electric brake device. This will be described with reference to FIG. 11 as appropriate. The correlation between the input shaft angle and the piston load is mainly governed by the caliper stiffness, the friction pad compression stiffness, and the linear actuator stiffness. Among these, the rigidity of the caliper and the linear motion actuator does not change during continuous use of the brake and is almost constant, and its value is known. In general, the amount of wear of the brake rotor is small relative to the amount of wear of the friction pad, and the amount of compressive deformation of the brake rotor is extremely small compared to the rigidity of the entire brake. Is almost nothing.

On the other hand, the compression stiffness of the friction pad is very low compared to the brake rotor, etc., and the impact on the overall brake stiffness is large. Therefore, as the friction pad wear progresses and the friction pad stiffness increases, the overall stiffness of the brake Becomes higher. Therefore, the pad wear amount estimating means 109 changes the correlation between the current input shaft angle and the piston load with respect to the predetermined correlation between the input shaft angle and the piston load when the friction pads 7 and 8 (FIG. 1) are new. The wear amount of the friction pads 7 and 8 (FIG. 1) can be estimated based on the above. As shown in FIG. 12, when the friction pad is new, non-linearity appears strongly in the correlation between the input shaft angle and the piston load. When the friction pad is fully worn (when the wear limit is reached), the correlation approaches linear.

FIG. 13 is a diagram showing the relationship between input shaft torque and piston load in one piston. The input shaft torque is substantially proportional to the command value of the braking force and is also substantially proportional to the motor current. For this reason, for example, the input shaft torque is obtained from the command value given from the brake force command means 101a (FIG. 11) or the motor current given from the current detection means Sc (FIG. 11) according to the determined proportionality coefficient.

In this electric brake device, hysteresis loss occurs mainly due to the influence of frictional forces such as the first and second

linear motion mechanisms

33a and 33b (FIG. 4). Specifically, the positive efficiency characteristic when the braking force is increased and the inverse efficiency characteristic when the braking force is decreased differ in the inclination (proportional relationship) of the piston load with respect to the input shaft torque. When the pressure is increased by depressing the brake pedal, the piston load gradually increases with respect to the input shaft torque than when the pressure is reduced. When the brake pedal is released and the pressure is reduced, the piston load decreases more rapidly than when the input shaft torque is increased. Therefore, as indicated by the broken line arrows in FIG. 13, the piston load does not change even if the input shaft torque changes between the solid lines on the pressure increasing side and the pressure reducing side.

FIG. 14 is a diagram showing the relationship between the motor rotation angle of the motor 30 (FIG. 4) and each piston load in this electric brake device. As shown in FIGS. 4 and 14, in the direct acting actuator 31 in which one motor 30 and the first and second

direct acting mechanisms

33a and 33b are directly connected, the first piston 26a and the second piston 26b are used. The timing at which the load is generated may be different.

In the linear actuator 31, the following expressions (1) and (2) are satisfied. Here, as described above, the timing at which the load is generated may be different between the first piston 26a and the second piston 26b. Therefore, the following equations (1) and (2) Each second piston 26b is represented by a separate function.

Formula (1): In the linear actuator 31 that directly drives the first and

second pistons

26a and 26b by a single motor 30, the piston (linear motion mechanism) input shaft angle, input shaft torque, and generated load An expression that shows the relationship.
F _A = f _A (θ _A ) = g _A (T _A )
F _B = f _B (θ _B ) = g _B (T _B )

here,
F _A : Axial load on the first piston (sensor output of the first load detecting means)
F _B : Axial load on the second piston (sensor output of the second load detecting means)
T _A : Input shaft torque at the first piston T _B : Input shaft torque at the second piston θ _A : Input shaft angle at the first piston θ _B : Input shaft angle at the second piston

_{_{Incidentally, f A (θ A),}} f B (θ B), g A (T A) and _g B _{(T B),} respectively, represent a function that depends on θ _{_A,} θ _B, _T _A and _{T B} .

Expression 2: Expression showing the relationship between the input shaft of the first and

second pistons

26a, 26b and the angle and torque of the motor 30.
θ _M = θ _A = θ _B
T _M = T _A + T _B
here,
θ _M : Motor rotation angle T _M : Motor torque

As shown in FIGS. 11 and 14, the abnormality determining means 108, as described above, wears the friction pads 7, 8 (FIG. 7) corresponding to the first and

second pistons

26a, 26b (FIG. 4). If an abnormality occurs in the first and second load detection means Sa and Sb, the relationship between the motor rotation angle and each piston load is used to determine the first and second load detection means Sa and Sb. Abnormalities can be detected. When the abnormality determination means 108 is out of a predetermined setting range, at least one of the sensor outputs F _A and F _B of the first and second load detection means Sa and Sb with respect to a certain motor rotation angle θ _M , One load detection means Sa (Sb) outside the set range or both load detection means Sa and Sb outside the set range are determined to be abnormal.

As shown in FIG. 11, the motor drive control unit 107 includes a normal control unit 110 and an abnormal time control unit 111. When the abnormality determining unit 108 determines that the first and second load detecting units Sa and Sb are not abnormal, the normal control unit 110 is detected by the first and second load detecting units Sa and Sb, respectively. The motor 30 is controlled using the total load value. The normal control unit 110 performs, for example, feedback control in which a brake force estimated value estimated from the sum of the loads follows a brake force command value given from the brake force command unit 101a. Note that the normal control unit 110 may perform feedforward control when, for example, the detection values such as the vehicle speed and the motor current satisfy a predetermined condition. The predetermined condition is an arbitrary condition determined by design or the like, and is determined, for example, by obtaining an appropriate condition by one or both of a test and a simulation.

When the abnormality determination unit 108 determines that one of the load detection units Sa (Sb) is abnormal, the abnormal-time control unit 111 detects the relationship between the expressions (1) and (2) and the normal other load. From the load detected by the means Sb (Sa), the motor current detected by the current detection means Sc, and the motor rotation angle detected by the rotation angle detection means Sd, the first and

second pistons

26a, 26b (FIG. 4). ) In the axial direction.

The abnormality control unit 111 controls the motor 30 based on the estimated value. The abnormal time control unit 111 performs, for example, feedback control in which a brake force estimated value calculated from each estimated axial load is followed with respect to a brake force command value given from the brake force command unit 101a. The abnormality control unit 111 may perform feedforward control when the abnormality determination unit 108 determines that the first and second load detection units Sa and Sb are both abnormal.

The warning signal output means 106 outputs a warning signal to the ECU 101 when it is determined from the abnormality determination means 108 that one or both of the load detection means Sa and Sb are abnormal. When the warning signal is input from the warning signal output unit 106, the ECU 101 causes the warning display etc. output unit 112 to output a warning display or the like. This can alert the driver. For example, a console panel or the like in the vehicle is provided with an output means 112 such as a warning display or a warning display such as an audio output device.

FIG. 15 is a flowchart showing step by step each process of the control device. This will be described with reference to FIG. This process is started under the condition that the main power supply of the vehicle equipped with the electric brake device is turned on, and the motor control unit 105 acquires the command value of the brake force from the brake force command unit 101a (step S1). Next, the motor control unit 105 acquires the axial loads in the first and

second pistons

26a and 26b (FIG. 4) from the first and second load detection means Sa and Sb, respectively (step S2). Further, the motor current is acquired from the current detection means Sc, and the motor rotation angle is detected from the rotation angle detection means Sd (step S3).

Next, the abnormality determination means 108 determines whether or not each load detection means Sa, Sb is abnormal (step S4). When it is determined that the first and second load detection means Sa and Sb are both abnormal (yes in step S4), the normal control unit 110 is detected by the first and second load detection means Sa and Sb, respectively. An operation for adding the loads is performed (step S5), and then the process proceeds to step S6. When it is determined that any one of the load detection means Sa (Sb) is abnormal (no in step S4), the abnormal direction control unit 111 performs axial directions in the first and

second pistons

26a and 26b (FIG. 4). The loads are estimated and added together (step S7). Thereafter, the process proceeds to step S6. In step S6, the load control by the normal control unit 110 or the abnormal time control unit 111 is executed. Thereafter, this process is terminated.

According to the linear motion actuator 31 described above, the normal control unit 110 controls the motor 30 using the total value of the loads detected by the first and second load detecting means Sa and Sb, respectively. In this way, more accurate load control can be performed by controlling the motor 30 based on the total value of the loads detected by the two load detecting means Sa and Sb. By applying this linear actuator 31 to the electric brake device, more accurate load control can be performed, so that a fade phenomenon or the like can be suppressed. Since the direct acting actuator 31 is of a single motor type or a two piston type, for example, it is possible to reduce the size in the radial direction as compared with a structure in which two pistons are driven by two motors. Therefore, it is possible to solve the layout problem when the linear actuator 31 is mounted on the vehicle.

When it is determined that any one of the load detection means Sa (Sb) is abnormal, the abnormality control unit 111 detects the load detected by the other normal load detection means Sb (Sa), the motor current, and From the motor rotation angle, the load generated in each of the two

linear motion mechanisms

33a and 33b is estimated. The abnormal time control unit 111 controls the motor 30 based on the estimated value. That is, the abnormal time control unit 111 controls the entire actuator using the normal load detecting means Sb (Sa). Thus, even if an abnormality occurs in one of the load detection means Sa (Sb), the load generated in each of the two

linear motion mechanisms

33a and 33b based on the output value of the normal load detection means Sb (Sa). Can be estimated and the redundancy is improved.

A second embodiment will be described.
The linear actuator may have a configuration in which a differential device is provided in which two pistons are driven by one motor and torque is distributed to the power transmission path. FIG. 16 shows the relationship between the motor rotation angle and the load generated on each piston in the linear motion actuator provided with this differential device. In this case, since the motor torque is evenly distributed to the two (first and second) pistons, the load generated in each piston always coincides, and the above-described formula (1) and the following formula (3) ) Is established.

Expression (3): Relationship between the input shaft of each piston, the angle of the motor, and the torque in a linear actuator provided with a differential device that drives two pistons with one motor and distributes torque to the power transmission path An expression showing
θ _M = θ _A + θ _B
T _M / 2 = T _A = T _B

As shown in FIGS. 11 and 16, when an abnormality occurs in any one of the load detection means Sa (Sb), the abnormality determination means 108 detects the sensor of each load detection means Sa, Sb with respect to the motor torque. By determining whether the output is within the predetermined range, it is possible to identify the load detection means Sa (Sb) in which an abnormality has occurred when the output is not within the range. In this case, the abnormal-time control unit 111 can control the entire linear motion actuator using the normal load detection means Sb (Sa).

As the first and second load detection means Sa and Sb, it is also possible to apply an optical type sensor other than the magnetic type, an eddy current type sensor, or a capacitance type sensor.

As shown in FIG. 10, the ECU 101 may estimate the vehicle body speed of this vehicle using each wheel speed sensor Sh and acceleration sensor Sg provided for each wheel. Further, the ECU 101 is provided with an anti-lock control function unit (not shown), and the anti-lock control function unit has an excessive number of wheels during braking from the estimated vehicle body speed and the wheel speed detected by the wheel speed sensor Sh. The braking force for preventing the locking may be determined by wheel speed feedback control or brake pressure reduction control accompanying determination of the locking tendency, and may intervene in the control as necessary.

As mentioned above, although the form for implementing this invention based on embodiment was demonstrated, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

26a ... 1st piston 26b ... 2nd piston 30 ... Motor 31 ... Linear motion actuator 33a ... 1st linear motion mechanism 33b ... 2nd linear motion mechanism 100 ... Control device 108 ... Abnormality determination means 110 ... Normal control part 111: Abnormal control unit Sa ... First load detection means Sb ... Second load detection means Sd ... Rotation angle detection means

Claims

One motor,
Two linear motion mechanisms, each including one piston, and converting the rotational motion of the motor into linear motion of the piston;
A control device for controlling the motor;
Two load detection means, each comprising two load detection means for detecting the axial load of the corresponding linear motion mechanism of the two linear motion mechanisms,
The control device is a linear motion actuator that controls the motor using a total value of loads detected by the two load detection means.
The linear actuator according to claim 1, further comprising:
Current detecting means for detecting the current of the motor;
Rotation angle detection means for detecting the rotation angle of the motor,
The controller is
An abnormality determination means for determining whether each of the two load detection means is abnormal according to a predetermined condition;
When it is determined by the abnormality determination means that the two load detection means are not abnormal, a normal control unit that controls the motor using a total value of loads detected by the two load detection means,
When one of the load detection means is determined to be abnormal by the abnormality determination means, the load detected by the other load detection means not determined to be abnormal, the motor current detected by the current detection means, Based on the motor rotation angle detected by the rotation angle detection means, the axial load generated in each of the two linear motion mechanisms is estimated according to a predetermined condition, and the total value of the estimated loads is estimated. An abnormal-time control unit for controlling the motor using
A linear actuator.
3. The linear motion actuator according to claim 2, wherein a command value is input to the control device, and the abnormal time control unit performs feedback control for causing the commanded value to follow the total value of the estimated loads. Linear actuator.
An electric brake device comprising the linear motion actuator according to any one of claims 1 to 3.