JP6621689B2 - Linear actuator - Google Patents

Description

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

  There has been proposed 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 (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 actuator (linear motion mechanism) becomes large in the radial direction, which causes a problem in layout. In addition, even if the required pressing force can be generated with a small linear motion mechanism in the radial direction, the pressure does not act evenly on the entire friction pad, thereby inducing a fade phenomenon or the progress of wear of the friction pad ("fade" Sometimes referred to as “phenomenon etc.”).
In addition, a control method in the case where one friction pad is pressed by two actuators is not disclosed.

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

The linear motion actuator 31 according to the present invention includes a single motor 30 and two pistons 26a and 26b. The linear motion actuators 33a and 33b convert the rotational motion of the motor 30 into the linear motion of the two pistons 26a and 26b. 33b and a control device 100 for controlling the motor 30,
Two load detecting means Sa and Sb for detecting axial loads of the two linear motion mechanisms 33a and 33b, respectively;
The control device 100 controls the motor 30 by using a total value of 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 may differ between the two pistons. In this case, accurate load control cannot be performed.
According to this configuration, the control device 100 performs, for example, feedback control that causes the estimated value estimated from the sum of the loads 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 by obtaining an appropriate condition by one or both of a test and a simulation, for example.
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 and 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; and rotation angle detection 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 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 it is determined by the abnormality determination means 108 that one of the load detection means Sa, (Sb) is abnormal, the load detected by the other load detection means Sb, (Sa) not determined as abnormal, Axial directions respectively generated in the two linear motion mechanisms 33a and 33b according to predetermined conditions from the motor current detected by the current detection means Sc and the motor rotation angle detected by the rotation angle detection means Sd. The abnormal-time control unit 111 that controls the motor 30 based on the estimated value may be included.
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 this configuration, the abnormality determination means 108 determines the abnormality of each load detection means Sa, 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 and (Sb) is abnormal, the abnormality control unit 111 detects the load, motor current detected by the other load detection means Sb and (Sa) which are normal. And the load generated in each of the two linear motion mechanisms 33a and 33b is estimated from the motor rotation angle. 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 detection means Sb, (Sa). Thus, even if an abnormality occurs in one of the load detection means Sa and (Sb), the abnormality occurs in the two linear motion mechanisms 33a and 33b based on the values of the normal load detection means Sb and (Sa). The load can be estimated and the redundancy is improved.

  The abnormal-time control unit follows a given value obtained by adding the estimated values estimated from the axial loads generated by the two linear motion mechanisms 33a and 33b with respect to the given command value. Feedback control may be performed. In this case, more accurate load control can be performed.

  The electric brake device according to the present invention includes any one of the direct acting actuators 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.

  A linear motion actuator according to the present invention includes one motor, two linear motion mechanisms that include two pistons and convert the rotational motion of the motor into linear motion of the two pistons, and a control device that controls the motor. And two load detection means for detecting axial loads of the two linear motion mechanisms, respectively, and the control device uses the sum of the loads detected by the two load detection means, respectively. Therefore, when this linear motion actuator is mounted on a vehicle or the like, the layout problem can be solved, and the fade phenomenon or the like can be suppressed.

1 is a front view of an electric brake device according to an embodiment of the present invention. It is a left view of the same electric brake device. 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 same electric brake device. It is a block diagram of a control system of the electric brake device. It is a block diagram which shows the detailed structure of the control apparatus of the same electric brake device. It is a figure which shows the relationship between the input shaft angle and piston load in one piston of the electric brake device. It is a figure which shows the relationship between the input shaft torque and piston load in the same piston. It is a figure which shows the relationship between the motor angle of each electric brake device, and each piston load. It is a flowchart which shows each process of the control apparatus in steps. It is a figure which shows the relationship between the motor angle and each piston load of the electric brake device which concerns on other embodiment of this invention.

  A linear actuator according to an 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. As shown in FIG. 1, the electric brake device includes a caliper 6, an electric linear actuator 31, a brake rotor 1, and friction pads 7 and 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 friction pad 7 (FIG. 5) 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 claw portion 22 and the piston housing portion 23 are disposed so as to face each other in the axial direction with the friction pads 7 and 8 on the inboard side and the outboard side interposed therebetween.

In this specification, in the state where this electric brake device is mounted on a vehicle, the vehicle width direction outer side of the vehicle is referred to as an outboard side, and the vehicle width direction center side of the vehicle is referred to as an inboard side.
As shown in FIG. 1, a claw portion 22 is provided at an 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 claw portion 22 supports the friction pad 8 on the outboard side.

  As shown in FIG. 4, the piston housing part 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 friction pad 7 faces the side surface on the inboard side of the brake rotor 1 in the axial direction.
As shown in FIG. 1, a mount 10 is supported by 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, when braking, the linear actuator 31 is driven by driving the motor 30 so that the friction pad 7 on the inboard side comes into contact with the brake rotor 1 as shown in FIG. 1 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 friction pad 8 on the outboard side supported by the claw portion 22 of the caliper 6 contacts the brake rotor 1. A braking force is applied to the brake rotor 1 by strongly holding the brake rotor 1 from both sides in the axial direction by the friction pads 8 and 7 on the outboard side and the inboard side.

  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, for example, on the vehicle body, but may be mounted on the caliper 6 as long as sufficient durability and environmental resistance 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. 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 includes 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 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 is slidable 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 a spiral groove having a lead angle different from that of the spiral protrusion 53 may be provided instead of the circumferential groove 54. .

  As shown in FIG. 7, a shaft support member 65 is provided on the inboard side of the first piston accommodation hole 25 a 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 includes 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 at regular intervals in the circumferential direction across the pair of disks 55 and 56, and support the planetary rollers 50 in a rotatable manner. 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 axial ends of the plurality of roller shafts 52. 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 a magnetic sensor 12 for detecting a change in a magnetic field, a Hall IC having a variable dynamic range and being inexpensive is commercially available, and is highly available. 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 101 a of the ECU 101 generates and outputs a target brake force command value according to the output of the sensor 103 a that changes according to 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 for driving 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 in response to the command value of the braking force, and performs current feedback control. 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. The pad wear amount estimation means 109 calculates the friction between the 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). The current friction pad corresponding to the first piston 26a (FIG. 4) compared to the predetermined correlation between the input shaft angle and the piston load when the pads 7 and 8 (FIG. 1) are new (when not worn). 7 and 8 (Fig. 1) are estimated. The input shaft angle theta _A first piston 26a (Fig. 4), for example, given by the rotation 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 calculates the 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). The correlation was compared with the predetermined correlation between the input shaft angle and the piston load when the friction pads 7 and 8 (FIG. 1) are new (non-wearing) and corresponded to the second piston 26b (FIG. 4). The current wear amount of the friction pads 7 and 8 (FIG. 1) is estimated. The input shaft angle θ _B of the second piston 26b (FIG. 4) is given by, for example, a 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. Note that 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 separate rotation sensors Se, Sf, etc. May not be provided.

  Here, FIG. 12 is a diagram showing the relationship between the input shaft angle and the piston load in one piston of the 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 caliper and the linear motion actuator have substantially linear rigidity, and are substantially known without changing even during continuous use of the brake. 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 estimation means 109 changes the correlation between the input shaft angle and the piston load when the friction pads 7 and 8 (FIG. 1) are new and the current input shaft angle and the piston load. Thus, the wear amount of the friction pads 7 and 8 (FIG. 1) can be estimated. 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 illustrating a relationship between input shaft torque and piston load in one piston. The input shaft torque is substantially proportional to the brake force command value and the motor current, so that, for example, the command value given from the brake force command means 101a (FIG. 11) or the motor given from the current detection means Sc (FIG. 11). It is obtained according to the relationship defined from the current. 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 reverse efficiency characteristic when the braking force is decreased differ in the inclination 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. However, 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 angle of the electric brake device and each piston load. 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. On the other hand, in the linear motion actuator 31, the relations of the expressions (1) and (2) are established.

Expression (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 ) = f _A ′ (T _A )
F _B = f _B (θ _B ) = f _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

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 angle T _M : Motor torque

As shown in FIG. 11 and FIG. 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 abnormality of the first and second load detection means Sa and Sb is determined from the relationship between the motor angle and each piston load. Can be detected. Abnormality determining means 108, for a motor angle theta _M, first, second load detection means Sa, Sb of the sensor output F _A, when out of the set range in which F _B was determined, out of the set range The other load detection means Sa, (Sb) is determined to be abnormal. The motor drive control unit 107 includes a normal control unit 110 and an abnormal time control unit 111.

  As shown in FIG. 11, when the abnormality control unit 108 determines that the first and second load detection units Sa and Sb are not abnormal, the normal control unit 110 first and second load detection units. The motor 30 is controlled using the total value of the loads detected at Sa and Sb. 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, a detection value such as a vehicle speed or a motor current satisfies 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 any one of the load detection units Sa and (Sb) is abnormal, the abnormal-time control unit 111 determines that the relationship between the expressions (1) and (2) From the load detected by the detection 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 ( Each axial load in FIG. 4) is estimated. The abnormal time control unit 111 controls the motor 30 based on the estimated value. For example, the abnormal-time control unit 111 performs feedback control for causing the brake force estimated value calculated from each estimated value to follow the command value of the brake force 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 both the first and second load detection units Sa and Sb are abnormal.

  The warning signal output unit 106 outputs a warning signal to the ECU 101 when it is determined from the abnormality determination unit 108 that one or both of the load detection units 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 the steps of the control device in stages. 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), and the motor. Current and motor angle are detected (step S3).

  Next, the abnormality determination unit 108 determines whether or not each load detection unit Sa, Sb is abnormal (step S4). When it is determined that the first and second load detection means Sa and Sb are both abnormal (step S4: yes), 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 and (Sb) is abnormal (step S4: no), the shafts in the first and second pistons 26a and 26b (FIG. 4) are controlled by the abnormality control unit 111. Each directional load is estimated (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 detection 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 respectively 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 and (Sb) is abnormal, the abnormality control unit 111 detects the load, motor current detected by the other load detection means Sb and (Sa) which are normal. And the load generated in each of the two linear motion mechanisms 33a and 33b is estimated from the motor rotation angle. 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 detection means Sb, (Sa). Thus, even if an abnormality occurs in one of the load detection means Sa and (Sb), the abnormality occurs in the two linear motion mechanisms 33a and 33b based on the values of the normal load detection means Sb and (Sa). The load can be estimated and the redundancy is improved.

Another embodiment will be described.
The linear actuator may have a configuration in which a differential device that drives two pistons with a single motor and distributes torque to the power transmission path is provided. The relationship between the motor angle and the load generated on each piston in the linear actuator provided with this differential device is shown in FIG. In this case, since the motor torque is evenly distributed to the two (first and second) pistons, the loads generated in the pistons always coincide with each other, and the above equations (1) and (3) are It 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 and (Sb), the abnormality determination means 108 detects the motor torque and the sensor output of each load detection means Sa 1 and Sb. By comparing these, it is possible to identify the load detection means Sa, (Sb) where the abnormality has occurred. In this case, the abnormality 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 other than the magnetic type, an eddy current type, or a capacitance type sensor.
As shown in FIG. 10, the ECU 101 may estimate the vehicle body speed in 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, 26b ... 1st and 2nd piston 30 ... Motor 31 ... Linear motion actuators 33a, 33b ... 1st, 2nd linear motion mechanism 100 ... Control device 108 ... Abnormality determining means 110 ... Normal control unit 111 ... Abnormality Control units Sa, Sb, first and second load detection means Sd, rotation angle detection means

Claims (4)

One motor, two linear motion mechanisms that include two pistons and convert the rotational motion of the motor into linear motion of the two pistons, and a control device that controls the motor,
Comprising two load detection means for detecting axial loads of the two linear motion mechanisms,
The linear motion actuator, wherein the control device controls the motor using a total value of loads detected by the two load detecting means. The linear motion actuator according to claim 1, further comprising: current detection means for detecting current of the motor; and rotation angle detection means for detecting a rotation angle of the motor,
The controller is
Abnormality determining means for determining whether or not each of the 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 it is determined by the abnormality determination means that one of the load detection means is abnormal, the load detected by the other load detection means not determined to be abnormal, the motor current detected by the current detection means, And the axial load generated by each of the two linear motion mechanisms according to a predetermined condition from the motor rotation angle detected by the rotation angle detection means, and the motor is controlled based on the estimated value. An abnormal time control unit,
A linear actuator.   The linear motion actuator according to claim 2, wherein the abnormal time control unit adds each estimated value estimated from an axial load generated by each of the two linear motion mechanisms to a given command value. A linear actuator that performs feedback control to follow up the total value obtained.   An electric brake device comprising the linear motion actuator according to any one of claims 1 to 3.

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