JP2014088911A - Electric linear motion actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric linear motion actuator capable of performing a stable controlling operation near an interface region between a load applying region and a non-load applying region for an object.SOLUTION: An electric linear motion actuator is constituted such that it comprises: a linear motion member A; motion converting mechanism B for converting a rotation of an electric motor 15 into a linear motion of the linear motion member A; displacement sensor 50 capable of detecting a displacement of the linear motion member A; and controller device 51 for calculating a converted load on the basis of the displacement of the linear motion member A detected by the displacement sensor 50, and a corresponding relation between the prescribed displacement and a load is set in such a way that the converted load is continuously changed between a negative load and a positive load when the linear motion member A moves over the load applying region and the non-load applying region.

Description

  The present invention relates to an electric linear actuator that converts rotation of a rotating shaft driven by an electric motor into linear motion of a linear motion member and applies a load to an object with the linear motion member.

  As a brake device for a vehicle, a hydraulic brake device that generates a braking force by pressing a friction pad against a brake disk with a hydraulic cylinder has been adopted. Recently, with the introduction of brake control such as ABS (anti-lock brake system). Electric brake devices that do not use a hydraulic circuit have attracted attention.

  The electric brake device uses an electric linear actuator that converts the rotation of the electric motor into linear movement of the linear member, and generates a braking force by pressing the friction pad against the brake disk with this electric linear actuator. is there.

  As such an electric brake device, for example, the one described in Patent Document 1 is known. The electric brake device of Patent Document 1 includes an electric motor, a linear motion member integrated with a friction pad provided so as to be linearly movable between a load load area and a no-load area on the brake disk, and rotation of the electric motor. It has a motion conversion mechanism that converts linear motion of the linear motion member, and a load sensor that detects the magnitude of the actual load when the linear motion member applies a load to the brake disc. The electric motor is controlled based on the actual load detected by the load sensor.

JP 2011-241851 A JP 2000-264186 A

  However, the electric brake device of Patent Document 1 has a problem in that unstable elements such as excessive overshoot and vibration occur near the boundary between the load-load area and the no-load area on the brake disk. That is, in the electric brake device, when the friction pad comes into contact with the brake disk and tries to apply a predetermined target load from a state where the friction pad is in a non-load region where the brake pad is not in contact with the brake disk, the friction pad is Since the magnitude of the actual load detected by the load sensor remains substantially zero before contacting the load, the difference between the actual load and the target load does not change. Therefore, the friction pad comes into contact with the brake disc while the electric motor rotates at a relatively high speed, and immediately after that, the actual load detected by the load sensor rises rapidly, and the actual load overshoots the target load excessively. There is a risk. Further, when the target load is small, the control is not stable near the boundary between the load load region and the no-load region, and there is a possibility that the vibration of the load occurs.

  On the other hand, an electric brake device described in Patent Document 2 is known as an electric brake device that hardly causes overshoot immediately after the friction pad contacts the brake disk. This electric brake device detects the magnitude of the actual load applied to the brake disk by the friction pad at the tip of the linear motion member based on the magnitude of the current supplied to the electric motor, and based on the magnitude of the actual load. The electric motor is controlled so that the load applied to the brake disk from the friction pad becomes the target load.

  And since the electric brake device of this patent document 2 suppresses the overshoot immediately after a friction pad contacts a brake disc, control of feedback control is carried out in the vicinity of the boundary of the load load area | region and no-load area | region to a brake disc. Control to set the gain to a small value. Further, when entering a load application region where a load is applied to the brake disc, control for switching the control gain of the feedback control to a large value is performed in order to ensure the response of the brake.

  However, in the electric brake device of Patent Document 2, when the target load is set in the vicinity of a region where the control gain of the feedback control is switched, a situation where the control gain of the feedback control is frequently switched between a small value and a large value. This may impair control stability. In addition, the configuration of the controller and the control law for switching the control gain of feedback control become complicated.

  The problem to be solved by the present invention is to provide an electric linear actuator capable of performing stable control in the vicinity of the boundary between a load-load region and a no-load region on an object.

In order to solve the above problems, the inventors of the present application employ the following configuration for the electric linear actuator.
An electric motor;
A linear motion member provided so as to be linearly movable between a load-load area and a no-load area on the object;
A motion conversion mechanism that converts rotation of the electric motor into linear movement of the linear motion member;
A displacement sensor capable of detecting the displacement of the linear member over both the load-load region and the no-load region;
Based on the displacement of the linear motion member detected by the displacement sensor and a correspondence relationship between the preset displacement and load, a converted load corresponding to the displacement of the linear motion member is calculated, and the calculated converted load And a control device for controlling the electric motor based on
The correspondence relationship between the preset displacement and the load is such that the converted load is continuously between a negative load and a positive load when the linear motion member moves across the load load region and the no load region. Is set to change.

  In this way, when the linear motion member is moved from the state where the linear motion member is in the no-load region and the load is applied to the object, Since the converted load changes according to the movement of the moving member, the electric motor can be controlled based on the same control law in the vicinity of the boundary between the load-loaded area and the no-load area on the object, and the control is stabilized. Can be achieved.

A load sensor for detecting the magnitude of the actual load when the linear motion member is applying a load to the object;
When the magnitude of the actual load detected by the load sensor or a differential value thereof coincides with a preset calibration threshold, the control device is preset with a displacement detected by the displacement sensor. It is preferable that the detection value of the displacement sensor is calibrated so as to obtain a calibration value.

  In this way, for example, even when the correspondence relationship between the displacement of the linear motion member and the actual load changes due to wear of the friction pad or the like, it is calculated based on the displacement of the linear motion member detected by the displacement sensor. It is possible to prevent the converted load from deviating from the actual load, and it is possible to control the load with high accuracy.

  The control device is configured to switch the control of the electric motor from the control based on the converted load to the control based on the actual load when the actual load becomes larger than a preset control switching threshold value. can do. In this way, it is possible to control the load with high accuracy even in a region where the load is large.

  When the actual load is smaller than a preset control switching threshold, the control device feedback-controls the electric motor based on a deviation between the converted load and a target load, and the actual load is preset. When the threshold value is larger than the control switching threshold value, the electric motor can be feedback-controlled based on the deviation between the actual load and the target load. In this way, it is possible to control the load with high accuracy even in a region where the load is large.

  The load sensor includes a magnetic target that generates a magnetic field and a magnetic sensor that is arranged so that a relative position with respect to the magnetic target changes according to a load applied to the object from the linear motion member. Can be adopted.

  As the displacement sensor, it is possible to employ a linear sensor that detects the position of the linearly moving member in the linear movement direction. However, the displacement sensor detects the rotation angle of the electric motor, and the rotation sensor detects it. If a conversion circuit that converts the rotation angle of the electric motor into the displacement of the linear motion member is adopted, the displacement of the linear motion member can be detected with high resolution, and the load can be controlled with high accuracy. It becomes possible to do.

  In the electric linear actuator according to the present invention, the linear motion member enters the load load region when the linear motion member is moved from the state where the linear motion member is in the no-load region to load the object. Since the converted load changes according to the movement of the linear motion member, the electric motor can be controlled based on the same control law in the vicinity of the boundary between the load load area and the no load area on the object. Stable control can be performed.

Sectional drawing which shows the electric brake device incorporating the electric type linear actuator of embodiment of this invention Fig. 1 is an enlarged sectional view of the vicinity of the electric linear actuator Sectional view along line III-III in FIG. Sectional view along line IV-IV in FIG. FIG. 2 is an enlarged sectional view in the vicinity of the load sensor. The block diagram of the control apparatus which controls the electric motor shown in FIG. The figure which shows the correspondence of the actuator displacement and conversion load which were preset in the control apparatus shown in FIG. Enlarged sectional view of an electric linear actuator showing an example in which a ball screw mechanism is used as a motion conversion mechanism An enlarged cross-sectional view of an electric linear actuator showing an example in which a ball ramp mechanism is adopted as a motion conversion mechanism Sectional view along line XX in FIG. 9A is a diagram showing the relationship between the ball and the inclined groove shown in FIG. 9, and FIG. 9B is a diagram showing a state in which the rotation disk and the linear motion disk are relatively rotated from the state shown in FIG. Figure

  FIG. 1 shows an electric brake device for a vehicle using an electric linear actuator 1 according to an embodiment of the present invention. This electric brake device includes a caliper body 6 having a shape in which opposed pieces 3 and 4 that are opposed to each other with a brake disk 2 that rotates integrally with a wheel interposed therebetween by a bridge 5, and a pair of left and right friction pads 7 and 8. Have. The electric linear motion actuator 1 is incorporated in a housing hole 9 that opens on the surface of the opposing piece 3 facing the brake disk 2.

  The friction pads 7 and 8 are provided between the opposing pieces 3 and 4 and the brake disc 2, respectively, and are brake discs against a mount (not shown) fixed to a knuckle (not shown) that supports the wheels. 2 is supported so as to be movable in the axial direction. The caliper body 6 is also supported by the mount so as to be slidable in the axial direction of the brake disc 2.

  As shown in FIG. 2, the electric linear actuator 1 is disposed so as to surround the rotating shaft 10, a plurality of planetary rollers 11 that are in rolling contact with the outer peripheral cylindrical surface of the rotating shaft 10, and the planetary rollers 11. The outer ring member 12, the carrier 13 that holds the planetary roller 11 so as to be capable of rotating and revolving, and a load sensor 14 disposed rearward in the axial direction of the outer ring member 12.

  The rotary shaft 10 is rotationally driven by the rotation of the electric motor 15 shown in FIG. The rotating shaft 10 is inserted into the receiving hole 9 with one end protruding from an opening on the rear side in the axial direction of the receiving hole 9 formed so as to penetrate the opposing piece 3 in the axial direction. The gear 16 is spline fitted to prevent rotation. The gear 16 is covered with a lid 18 fixed with a bolt 17 so as to close an opening on the rear side in the axial direction of the accommodation hole 9. A bearing 19 that rotatably supports the rotary shaft 10 is incorporated in the lid 18.

  As shown in FIG. 3, the planetary roller 11 is in rolling contact with the outer peripheral cylindrical surface of the rotating shaft 10, and the planetary roller 11 is caused by friction between the planetary roller 11 and the rotating shaft 10 when the rotating shaft 10 rotates. Also comes to rotate. A plurality of planetary rollers 11 are provided at regular intervals in the circumferential direction.

  As shown in FIG. 2, the outer ring member 12 is accommodated in an accommodation hole 9 provided in the facing piece 3 of the caliper body 6, and is supported so as to be slidable in the axial direction on the inner periphery of the accommodation hole 9. An engagement recess 21 is formed at the front end in the axial direction of the outer ring member 12 to engage with an engagement protrusion 20 formed on the back surface of the friction pad 7. Thus, the outer ring member 12 is prevented from rotating with respect to the caliper body 6.

  A spiral ridge 22 is provided on the inner periphery of the outer ring member 12, and a circumferential groove 23 that engages with the spiral ridge 22 is provided on the outer periphery of the planetary roller 11, and when the planetary roller 11 rotates. The spiral ridge 22 of the outer ring member 12 is guided by the circumferential groove 23 so that the outer ring member 12 moves in the axial direction. In this embodiment, the circumferential groove 23 having a lead angle of 0 degrees is provided on the outer periphery of the planetary roller 11, but a spiral groove having a lead angle different from that of the spiral protrusion 22 may be provided instead of the circumferential groove 23. .

  The carrier 13 includes a carrier pin 13A that rotatably supports the planetary roller 11, an annular carrier plate 13C that maintains a constant circumferential interval at the axial front end of each carrier pin 13A, and an axial direction of each carrier pin 13A. And an annular carrier body 13B that maintains a constant circumferential interval at the rear end. The carrier plate 13C and the carrier body 13B face the planetary roller 11 in the axial direction, and are connected via a connecting rod 24 disposed between the planetary rollers 11 adjacent in the circumferential direction.

  The carrier body 13 </ b> B is supported on the rotary shaft 10 via the sliding bearing 25 and is rotatable relative to the rotary shaft 10. A thrust bearing 26 is incorporated between the planetary roller 11 and the carrier body 13B to block the rotation of the planetary roller 11 from being transmitted to the carrier body 13B. The thrust bearing 26 supports the planetary roller 11 so that it can rotate.

  Each carrier pin 13A is urged radially inward by a reduced diameter ring spring 27 mounted so as to circumscribe a plurality of carrier pins 13A arranged at intervals in the circumferential direction. By the urging force of the diameter-reduced ring spring 27, the outer periphery of the planetary roller 11 is pressed against the outer periphery of the rotating shaft 10, and slippage between the rotating shaft 10 and the planetary roller 11 is prevented. In order to apply the urging force of the reduced diameter ring spring 27 over the entire axial length of the planetary roller 11, reduced diameter ring springs 27, 27 are provided at both ends of the carrier pin 13A.

  Here, the outer ring member 12 and the friction pad 7 shown in FIG. 1 and FIG. 2 are a load-load region where the friction pad 7 contacts the brake disk 2 and loads the load, and the friction pad 7 does not contact the brake disk 2. The linear motion member A that moves linearly with the no-load region is configured. Further, the rotating shaft 10 to which the rotation of the electric motor 15 is input, the plurality of planetary rollers 11 that are in rolling contact with the cylindrical surface of the outer periphery of the rotating shaft 10, and the plurality of planetary rollers 11 are held so as to be capable of rotating and revolving. The carrier 13 whose movement in the axial direction is restricted, the outer ring member 12 disposed so as to surround the plurality of planetary rollers 11, the spiral ridge 22 provided on the inner periphery of the outer ring member 12, and the spiral ridge The circumferential groove 23 provided on the outer periphery of each planetary roller 11 so as to engage with the motor 22 is a motion that converts the rotation of the electric motor 15 into a linear motion of the linear motion member A (the outer ring member 12 and the friction pad 7). It functions as the conversion mechanism B.

  The load sensor 14 includes an annular plate-shaped flange member 30 and a support member 31 that are opposed to each other at an interval in the axial direction, a magnetic target 32 that generates a magnetic field, and a magnetic sensor 33 that detects the strength of the magnetic field. Then, the support member 31 is fitted into the accommodation hole 9 so as to be positioned behind the flange member 30 in the axial direction.

  As shown in FIGS. 4 and 5, the flange member 30 has a cylindrical portion 34 that protrudes toward the support member 31. The outer diameter surface of the cylindrical portion 34 faces the inner diameter surface of the support member 31 in the radial direction, and the magnetic target 32 is fixed to a chamfered portion 35 formed on the outer diameter surface of the cylindrical portion 34, so A magnetic sensor 33 is fixed to an axial groove 36 formed on the inner diameter surface. The flange member 30 and the support member 31 are formed of a magnetic material.

  The support member 31 has an annular protrusion 38 on the outer diameter side portion of the surface facing the flange member 30, and supports the outer diameter side portion of the flange member 30 with the annular protrusion 38. Hold the interval.

  The magnetic target 32 is composed of two permanent magnets 39 magnetized in the radial direction so as to have magnetic poles at the radially inner end and the radially outer end. The two permanent magnets 39 are arranged adjacent to each other so that magnetic poles having opposite polarities (that is, N pole and S pole) are aligned in the axial direction.

  When a neodymium magnet is used as the permanent magnet 39, a strong magnetic field is generated in a space-saving manner, so that the disassembly performance of the load sensor 14 can be increased. May be. When a samarium cobalt magnet or an alnico magnet is used, it is possible to suppress a decrease in the magnetic field accompanying the temperature increase of the permanent magnet 39. Also, a praseodymium magnet or a samarium iron nitride magnet can be used.

  The magnetic sensor 33 is disposed in the vicinity of the boundary between adjacent magnetic poles of the two permanent magnets 39 so as to face the magnetic target 32 in the direction perpendicular to the axis (radial direction in the drawing). As the magnetic sensor 33, it is possible to use a magnetoresistive element (so-called MR sensor) or a magneto-impedance element (so-called MI sensor). However, using a Hall IC is advantageous in terms of cost and has a heat resistance. Since a high Hall IC is commercially available, it is suitable for an electric brake application in which high frictional heat is generated.

  As shown in FIG. 2, positioning grooves 40 and 41 extending in the axial direction are formed on the outer periphery of the flange member 30 and the outer periphery of the support member 31, and a common key member 42 is fitted into the positioning grooves 40 and 41. The flange member 30 and the support member 31 are positioned in the circumferential direction so that the circumferential position of the magnetic target 32 matches the circumferential position of the magnetic sensor 33.

  A spacer 43 that revolves integrally with the carrier 13 and a thrust bearing 44 that transmits an axial load between the spacer 43 and the flange member 30 are incorporated between the carrier 13 and the flange member 30. A rolling bearing 45 that rotatably supports the rotary shaft 10 is incorporated in the inner periphery of the flange member 30.

  The load sensor 14 is restricted from moving forward and backward in the axial direction by locking the outer peripheral edge of the support member 31 with retaining rings 46 and 48 attached to the inner periphery of the accommodation hole 9. The load sensor 14 supports the carrier body 13 </ b> B in the axial direction via the spacer 43 and the thrust bearing 44, thereby restricting the movement of the carrier 13 in the rearward direction in the axial direction. Further, the carrier 13 is also restricted from moving forward in the axial direction by a retaining ring 47 attached to the front end of the rotating shaft 10 in the axial direction. Therefore, the movement of the carrier 13 in both the axial front and the axial rear is restricted, and the planetary roller 11 held by the carrier 13 is also restricted in the axial movement.

  This load sensor 14 detects the magnitude of the actual load when the friction pad 7 is in contact with the brake disk 2 and is applying a load. That is, when the brake disk 2 is pressed by the friction pad 7, the outer ring member 12 receives a reaction force of a load that presses the brake disk 2, and the reaction force is the planetary roller 11, the carrier 13, the spacer 43, and the thrust bearing 44. It transmits to the flange member 30 via. The flange member 30 is deflected axially rearward by the reaction force, and the relative position between the magnetic target 32 and the magnetic sensor 33 changes. At this time, since the output signal of the magnetic sensor 33 changes in accordance with the change in the relative position, the magnitude of the load that presses the brake disk 2 can be detected based on the output signal of the magnetic sensor 33.

  Here, the amount of change in the relative position between the magnetic target 32 and the magnetic sensor 33 when the brake disk 2 is pressed by the friction pad 7 is extremely small. For example, when the magnitude of the load that presses the brake disk 2 is 30 kN, the amount of change in the relative position between the magnetic target 32 and the magnetic sensor 33 is as small as about 0.1 mm in the axial direction. The plurality of permanent magnets 39 are arranged so that the opposite magnetic poles are aligned in the relative displacement direction of the magnetic target 32 and the magnetic sensor 33, and the magnetic sensor 33 is arranged near the boundary between the adjacent magnetic poles. The output signal 33 changes sharply with respect to the change in the relative position between the magnetic target 32 and the magnetic sensor 33, and the amount of change in the relative position between the magnetic target 32 and the magnetic sensor 33 can be detected with high accuracy. In addition, since the load sensor 14 detects the magnitude of the load by using a change in the relative position of the magnetic target 32 and the magnetic sensor 33 that are arranged in non-contact with each other, an impact load or a shear load is input to the load sensor. Even if it is done, a sensor is hard to break down and high durability can be secured.

  As shown in FIG. 6, the electric linear actuator 1 includes a displacement sensor 50 that detects a displacement (hereinafter referred to as “actuator displacement”) of the linear member A (the outer ring member 12 and the friction pad 7).

  The displacement sensor 50 can be composed of, for example, a rotation sensor that detects the rotation angle of the electric motor 15 and a conversion circuit that converts the rotation angle of the electric motor 15 detected by the rotation sensor into actuator displacement. In converting the rotation angle of the electric motor 15 into the actuator displacement, the correspondence relationship between the rotation angle of the electric motor 15 and the actuator displacement is as follows: the reduction ratio between the electric motor 15 and the rotation shaft 10, the diameter of the rotation shaft 10, the planetary roller 11, the inner diameter of the outer ring member 12, the lead angle of the spiral protrusion 22, and the like. As a rotation sensor for detecting the rotation angle of the electric motor 15, a resolver or a Hall element incorporated in the electric motor 15 can be adopted, and the rotation angle is estimated based on a line voltage for supplying electric power to the electric motor 15. It is also possible to employ a power supply device that does this.

  The displacement sensor 50 can detect the actuator displacement over both a load load region where the friction pad 7 contacts the brake disk 2 and applies a load, and a non-load region where the friction pad 7 does not contact the brake disk 2. it can.

  The electric motor 15 is controlled by the control device 51 shown in FIG. The control device 51 includes a controller 52 that drives the electric motor 15 and a feedback calculator 53. The feedback calculator 53 calculates the current load based on the detection signals of the load sensor 14 and the displacement sensor 50 and feeds back the load to the controller 52. The controller 52 controls the electric motor 15 based on the deviation between the load fed back from the feedback calculator 53 and the target load (load command value input from a brake control device not shown). Here, the controller 52 is a series compensator that performs at least one operation among proportionality, integral, and differentiation with respect to the deviation.

  The load calculated by the feedback calculator 53 is an actual load based on the detection signal of the load sensor 14 and a converted load based on the detection signal of the displacement sensor 50. As shown by the chain line in FIG. 7, the actual load remains almost zero regardless of the actuator displacement in the no-load region to the brake disk 2, and enters the load-load region where the brake disk 2 is loaded. As the actuator displacement increases, the actual load also increases and changes to take a positive value. Here, the actual load never becomes smaller than zero.

  On the other hand, the converted load is a pseudo load set so as to change corresponding to the actuator displacement. As shown by the solid line in FIG. It is calculated based on the detected actuator displacement. Here, the converted load takes a negative value that gradually changes to zero in the no-load region, becomes zero at the boundary between the no-load region and the load-load region, and enters the load-load region and is a positive value corresponding to the actual load. It changes smoothly to take the value of. That is, the converted load is set so as to continuously change between a negative load and a positive load when the linear motion member A moves across the load load region and the no-load region. When the correspondence relationship between the displacement and the load is set in advance, the correspondence relationship between the actuator displacement and the converted load in the load load region can be set based on the rigidity of the brake disk 2 so that the actual load and the converted load coincide with each other. .

Incidentally, the correspondence between the actuator displacement and the actual load may change due to wear of the friction pads 7 and 8 or the like. Therefore, when the magnitude of the actual load detected by the load sensor 14 or the differential value thereof coincides with the preset calibration threshold Th ₀ , the feedback calculator 53 sets the actuator displacement at that time in advance. The detected value of the displacement sensor 50 is calibrated so as to obtain a corrected value. Thereby, it is possible to prevent the conversion load calculated based on the actuator displacement from deviating from the actual load due to wear of the friction pads 7 and 8 or the like.

The controller 52 controls the electric motor 15 based on the converted load near the boundary between the load load region and the no load region, and enters the load load region and the actual load becomes greater than the control switching threshold Th ₁ . Sometimes, the control of the electric motor 15 is switched from the control based on the converted load to the control based on the actual load. That is, the electric motor 15, when the actual load than the control switching threshold Th ₁ is small, is feedback-controlled based on the deviation of the converted load and target load, is large actual load than the control switching threshold Th ₁ In some cases, feedback control is performed based on the deviation between the actual load and the target load. Here, control switching threshold Th ₁ is a preset positive value. Control switching threshold Th ₁ may be the same value as the calibration threshold Th _0.

  Next, an operation example of the electric linear actuator 1 described above will be described.

  When the electric motor 15 is operated, the rotating shaft 10 rotates and the planetary roller 11 revolves around the rotating shaft 10 while rotating around the carrier pin 13A. At this time, the outer ring member 12 and the planetary roller 11 move relative to each other in the axial direction by the engagement of the spiral ridge 22 and the circumferential groove 23, but the planetary roller 11 is restricted from moving in the axial direction together with the carrier 13. The roller 11 does not move in the axial direction, and the outer ring member 12 moves in the axial direction. In this way, the electric linear actuator 1 converts the rotation of the rotary shaft 10 driven by the electric motor 15 into a linear motion of the outer ring member 12, and the opposing piece provided on the outer ring member 12 and the caliper body 6. 4, the friction pads 7 and 8 are pressed against the brake disc 2 to generate a braking force of the electric brake device.

  By the way, in the electric brake device, when the friction pad 7 moves from the no-load area to the brake disk 2 to the load-load area, the load is detected by the load sensor 14 before the friction pad 7 contacts the brake disk 2. Since the load remains almost zero, the difference between the actual load and the target load does not change. Therefore, when the electric motor 15 is controlled based on the actual load, the friction pad 7 contacts the brake disk 2 while the electric motor 15 rotates at a relatively high speed, and the actual load detected by the load sensor 14 immediately thereafter. May suddenly rise and the actual load may overshoot the target load excessively. In addition, when the target load is small, the control is not stable near the boundary between the load load region and the no-load region, and there is a risk of vibration of the load.

  Therefore, the control device 51 makes it possible to perform stable control in the vicinity of the boundary between the load load area and the no-load area for the brake disk 2. In the vicinity of the boundary, the electric motor 15 is controlled based on the converted load.

That is, when the friction pad 7 moves from the no-load region to the brake disk 2 to the load-bearing area, in the no-load region, the actual load is less than the control threshold value for switching Th _1, based on the terms of the load electric The motor 15 is feedback controlled. Here, the converted load changes in accordance with the actuator displacement in the no-load region as well as in the load load region, so that the deviation between the converted load and the target load also changes in accordance with the actuator displacement in the no-load region. Therefore, it is possible to prevent the friction pad 7 from coming into contact with the brake disk 2 while the electric motor 15 is rotated at a high speed, and it is difficult for excessive overshoot to occur.

In load bearing region, when the actual load is greater than the control threshold value for switching Th _1, control of the electric motor 15 is switched from control based on the converted load control based on the actual load, the actual load and the target load The electric motor 15 is feedback-controlled based on the deviation. By switching from the converted load to the actual load in this way, the load can be controlled with high accuracy even in a region where the load is large.

  In the electric brake device, when the friction pad 7 is not in contact with the brake disk 2 and the friction pad 7 is brought into contact with the brake disk 2 to apply a load, the friction pad 7 contacts the brake disk 2. Even before, the converted load changes according to the actuator displacement, so that the same control system (that is, the control system having the same feedback control gain) is set near the boundary between the load load area and the no-load area on the brake disk 2. The electric motor 15 can be controlled based on this, and the control can be stabilized.

The electric brake system, when the actual load is greater than the control threshold value for switching Th _1, the control of the electric motor 15, is switched from control based on the converted load control based on the actual load, the load is large area The load can be controlled with high accuracy.

  As the displacement sensor 50 for detecting the actuator displacement, a linear sensor for detecting the position of the friction pad 7 or the outer ring member 12 in the linear movement direction can be adopted. However, as in the above embodiment, the electric motor 15 By adopting a configuration comprising a rotation sensor that detects the rotation angle and a conversion circuit that converts the rotation angle of the electric motor 15 detected by the rotation sensor into an actuator displacement, the actuator displacement can be detected with high resolution. It is possible to control the load with high accuracy.

  In the above embodiment, the control system in which the controller 52 is provided in the series part of the feedback control system has been described as an example. However, the present invention can also be applied to a control system in which the controller 52 is provided in the feedback part. The present invention can also be applied to a control system in which the controller 52 is provided in both the series part and the feedback part.

  In the above embodiment, as the motion conversion mechanism B that converts the rotation of the electric motor 15 into the linear motion of the linear motion member A (the outer ring member 12 and the friction pad 7), the rotary shaft 10 to which the rotation of the electric motor 15 is input, A plurality of planetary rollers 11 that are in rolling contact with the outer peripheral cylindrical surface of the rotary shaft 10, a carrier 13 that holds the plurality of planetary rollers 11 so as to be capable of rotating and revolving, and whose axial movement is restricted, and a plurality of planetary rollers 11 is provided on the outer periphery of each planetary roller 11 so as to be engaged with the outer surface of the outer ring member 12, the spiral protrusion 22 provided on the inner periphery of the outer ring member 12, and the spiral protrusion 22. The planetary roller type motion conversion mechanism B having the circumferential groove 23 has been described as an example, but the present invention is similarly applied to an electric linear actuator that employs the motion conversion mechanism B having another configuration. To do Kill.

  For example, FIG. 8 shows an example of an electric linear actuator that employs a ball screw type motion conversion mechanism B as the motion conversion mechanism B. Hereinafter, portions corresponding to the above embodiment are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 8, the linear actuator includes a rotating shaft 10 to which rotation of the electric motor 15 is input, a screw shaft 60 provided integrally with the rotating shaft 10, and a nut 61 provided so as to surround the screw shaft 60. A plurality of balls 64 incorporated between a screw groove 62 formed on the outer periphery of the screw shaft 60 and a screw groove 63 formed on the inner periphery of the nut 61, and a ball from the end point of the screw groove 63 of the nut 61 to the start point A return tube (not shown) for returning 64 and a load sensor 14 disposed behind the nut 61 in the axial direction are provided.

  The nut 61 is accommodated in an accommodation hole 9 provided in the opposing piece 3 of the caliper body 6 so as to be slidable in the axial direction while being prevented from rotating with respect to the caliper body 6. A spacer 43 that rotates integrally with the screw shaft 60 is provided at the axially rear end of the screw shaft 60, and the spacer 43 is supported by the load sensor 14 via a thrust bearing 44. Here, the load sensor 14 supports the nut 61 in the axial direction through the spacer 43, the thrust bearing 44, and the screw shaft 60, thereby restricting the movement of the nut 61 in the axial rearward direction.

  In this electric linear actuator, by rotating the rotary shaft 10, the screw shaft 60 and the nut 61 are rotated relative to each other to move the nut 61 forward in the axial direction, and the nut 61 is opposed to the caliper body 6. A braking force is generated by pressing the friction pads 7 and 8 against the brake disk 2 by the piece 4. At this time, the screw shaft 60 receives a reaction force in the rearward direction in the axial direction, and the reaction force is transmitted to the load sensor 14 via the spacer 43 and the thrust bearing 44.

  FIG. 9 shows an example in which an electric linear actuator using a ball ramp type motion conversion mechanism B is applied as the motion conversion mechanism B.

  In FIG. 9, the linear motion actuator includes a rotary shaft 10, a rotary disk 70 that is prevented from rotating on the outer periphery of the rotary shaft 10, a linear motion disk 71 that faces the front of the rotary disk 70 in the axial direction, A plurality of balls 72 sandwiched between the disk 70 and the linear motion disk 71, and a load sensor 14 disposed behind the linear motion disk 71 in the axial direction.

  The linear motion disk 71 is accommodated in the accommodation hole 9 provided in the opposing piece 3 of the caliper body 6 so as to be slidable in the axial direction while being prevented from rotating with respect to the caliper body 6. A spacer 43 that rotates integrally with the rotating disk 70 is provided at the rear end in the axial direction of the rotating disk 70, and the spacer 43 is supported by the load sensor 14 via a thrust bearing 44. Here, the load sensor 14 supports the rotation disk 70 in the axial direction via the spacer 43 and the thrust bearing 44, thereby restricting the movement of the rotation disk 70 in the axial direction rearward.

  As shown in FIGS. 10 and 11, an inclined groove 73 whose depth gradually decreases along one circumferential direction is formed on the surface 70 a of the rotating disk 70 facing the linearly moving disk 71. An inclined groove 74 whose depth gradually decreases along the other direction in the circumferential direction is formed on the surface 71a facing the rotating disk 70. As shown in FIG. 11 (a), the ball 72 is incorporated between the inclined groove 73 of the rotary disk 70 and the inclined groove 74 of the linear motion disk 71. As shown in FIG. When the rotating disk 70 rotates relative to the disk 71, the balls 72 roll in the inclined grooves 73 and 74, and the interval between the rotating disk 70 and the linearly moving disk 71 is increased.

  In this electric linear actuator, by rotating the rotating shaft 10, the linearly moving disk 71 and the rotating disk 70 are rotated relative to each other to move the linearly moving disk 71 forward in the axial direction. A braking force is generated by pressing the friction pads 7 and 8 against the brake disc 2 by the opposing piece 4 provided on the body 6. At this time, the linear motion disk 71 receives a reaction force in the rearward direction in the axial direction, and the reaction force is transmitted to the load sensor 14 via the spacer 43 and the thrust bearing 44.

DESCRIPTION OF SYMBOLS 1 Electric linear actuator 2 Brake disk 7 Friction pad 14 Load sensor 15 Electric motor 32 Magnetic target 33 Magnetic sensor 50 Displacement sensor 51 Controller A Linear motion member B Motion conversion mechanism Th ₀ Calibration threshold Th ₁ Control switching threshold value

Claims (7)

An electric motor (15);
A linear motion member (A) provided so as to be linearly movable between a load-loaded region and a no-load region on the object (2);
A motion conversion mechanism (B) for converting rotation of the electric motor (15) into linear movement of the linear motion member (A);
A displacement sensor (50) capable of detecting the displacement of the linear motion member (A) over both a load-load region and a no-load region;
The converted load corresponding to the displacement of the linear motion member (A) based on the displacement of the linear motion member (A) detected by the displacement sensor (50) and the correspondence between the preset displacement and the load. And a control device (51) for controlling the electric motor (15) based on the calculated converted load,
The correspondence relationship between the preset displacement and the load is that the conversion load is between a negative load and a positive load when the linear motion member (A) moves across the load load region and the no load region. Electric linear actuator that is set to change continuously. A load sensor (14) for detecting the magnitude of the actual load when the linear motion member (A) is applying a load to the object (2);
When the magnitude of the actual load detected by the load sensor (14) or a differential value thereof matches a preset calibration threshold value (Th ₀ ), the control device (51) The electric linear actuator according to claim 1, wherein the detected value of the displacement sensor (50) is calibrated so that the displacement detected by the sensor (50) becomes a preset calibration value. The control device (51) controls the electric motor (15) from the control based on the converted load when the actual load becomes larger than a preset control switching threshold (Th ₁ ). The electric linear actuator according to claim 2, wherein the control is switched to control based on an actual load. When the actual load is smaller than a preset control switching threshold value (Th ₁ ), the control device (51) controls the electric motor (15) based on a deviation between the converted load and the target load. Feedback control is performed, and when the actual load is larger than a preset control switching threshold (Th ₁ ), the electric motor (15) is feedback-controlled based on a deviation between the actual load and a target load. Item 4. The electric linear actuator according to Item 2 or 3.   The load sensor (14) has a magnetic target (32) that generates a magnetic field and a relative position with respect to the magnetic target (32) that changes according to a load applied to the object (2) from the linear motion member (A). The electric linear motion actuator according to any one of claims 2 to 4, comprising a magnetic sensor (33) arranged so as to.   The displacement sensor (50) is a rotation sensor that detects a rotation angle of the electric motor (15), and a rotation angle of the electric motor (15) detected by the rotation sensor is a displacement of the linear motion member (A). 6. The electric linear actuator according to claim 1, further comprising a conversion circuit for conversion.   The electric linear actuator according to any one of claims 1 to 5, wherein the displacement sensor (50) is a linear sensor that detects a position of the linear motion member (A) in a linear movement direction.

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