Load sensor and electric brake device equipped with same

Abstract

To provide a load sensor and the like that can obtain sufficient detection accuracy with a simple configuration.SOLUTION: A load sensor comprises a single sensor member 1, a displacement sensor 2, and a sensor target 3. The sensor member 1, in a vertical cross-section along a center axis C of the sensor member 1 parallel to an application direction F of a load, has a space S at which all of three directions and at least a portion of one direction among four directions that are forward and backward directions parallel to the center axis C and forward and backward directions perpendicular to the center axis C are enclosed by the sensor member 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a load sensor using a displacement sensor and an electric brake device including the same. [Background technology]

[0002] Conventionally, a load sensor that detects the load applied to a friction pad by minute displacement is used as a sensor for controlling the magnitude of the braking force of an electric brake device (see, for example, Patent Document 1). This load sensor includes two sensor members, a flange member and a support member, a magnetic sensor fixed to one of the two sensor members, and a magnetic target fixed to the other. When an axial load is applied to the flange member, the flange member bends, causing a relative displacement between the magnetic sensor and the magnetic target, and the magnitude of the load is detected based on the magnetic field detected by the magnetic sensor.

[0003] Here, the flange member is fixed to the mating portion of the support member by press-fitting or crimping, and the relative circumferential positions of the flange member and the support member are fixed by inserting a positioning pin while the axial pin holes formed in both members are aligned. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-032970 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration with two sensor elements as described above, hysteresis may occur in the correlation between load and displacement due to the influence of minute sliding friction with the fitting portion of the support element that occurs as the flange element deforms (deflects), and sufficient detection accuracy may not be achieved.

[0006] An object of the present invention is to provide a load sensor that can achieve sufficient detection accuracy with a simple configuration, and an electric brake device equipped with the same. [Means for solving the problem]

[0007] The load sensor of the present invention includes a single sensor member, a displacement sensor, and a sensor target, and when a load is applied to the sensor member from a load application side opposite a support side on which the sensor member is supported, the sensor member deforms and the displacement sensor and the sensor target are displaced relative to each other, and the magnitude of the load is detected based on the amount of relative displacement between the displacement sensor and the sensor target detected by the displacement sensor. Furthermore, in a longitudinal cross section along a central axis of the sensor member parallel to the direction in which the load is applied, the sensor member has a space surrounded by the sensor member in all three directions and at least a portion of one direction out of four directions: a front-rear direction parallel to the central axis and a front-rear direction perpendicular to the central axis.

[0008] In the load sensor of the present invention, the sensor element is single and has a shape with the above-mentioned space, so that the displacement sensor and the sensor target undergo a relatively large relative displacement, and sliding friction does not occur between the multiple sensor elements, so sufficient detection accuracy can be obtained with a simple configuration.

[0009] In the load sensor of the present invention, the sensor member may have an opening communicating with the space on the support side.

[0010] In the load sensor of the present invention, the sensor member may have a convex portion on the load application side that is in the shape of a hollow disk (also called a perforated disk or annular plate) and protrudes in the direction of the central axis, and in this case, the load may be applied to the end face of the convex portion.

[0011] The load sensor of the present invention preferably includes a stay member that is counter-fitted with the end face and inner circumferential surface of the convex portion, so that a load applied to the stay member is transmitted to the sensor member via at least the end face of the convex portion. In this case, counter-fitting of the stay member with the end face and inner circumferential surface of the convex portion of the sensor member suppresses radially inward displacement of the convex portion of the sensor member when a load is applied, thereby mitigating radial slippage between the sensor member and the stay member around the central axis. Furthermore, since the convex portion of the sensor member, which has a relatively low rigidity, elastically deforms, the rigidity of the stay member does not inhibit deformation of the sensor member. Therefore, detection accuracy can be improved while maintaining the required sensor sensitivity.

[0012] In the load sensor of the present invention, the load may be applied to an annular pressure region on the surface of the stay member, and the average radius of the convex portion from the central axis may be larger than the average radius of the pressure region from the central axis. In this case, the amount of elastic deformation at the contact position between the sensor member and the stay member is reduced, thereby further reducing sliding friction in the radial direction between the sensor member and the stay member and further improving detection accuracy.

[0013] In the load sensor of the present invention, the displacement sensor and the sensor target may be provided radially opposite to each other with respect to the central axis, and the displacement sensor may be disposed radially outward of the sensor target. In general use of a load sensor, a structure in which wiring is ultimately drawn out toward the outside of the displacement sensor is assumed, but if the displacement sensor is disposed radially outward of the sensor target, wiring of the displacement sensor is easy.

[0014] In the load sensor of the present invention, a first material part including a portion closer to the load application side than the space and a second material part including a portion closer to the support side than the space are joined without a boundary that allows separation into multiple members to form the sensor member, and the material of the first material part may have a higher yield stress than the material of the second material part. In this case, by applying a stronger material to the portion where the load is primarily applied, it is easier to balance strength with cost or weight.

[0015] In particular, the first material portion and the second material portion may be made of an iron-based material, and the material of the first material portion may have a higher carbon content. Generally, in forging, which can inexpensively produce parts made of an iron-based material, materials with a lower carbon content tend to have better workability and reduce manufacturing costs. Therefore, if the material of the first material portion has a higher carbon content, a stronger material is used in parts that are subject to greater loads, and a material with better workability is used in parts that are subject to relatively less loads, making it easier to balance strength and cost.

[0016] The present invention also includes an electric brake device that includes a caliper, a linear actuator having a linear moving part that moves linearly, a brake rotor, and friction pads, the linear moving part moving the friction pads toward and away from the brake rotor, and that includes any of the load sensors of the present invention described above and detects the load applied to the friction pads using the load sensor. The electric brake device of the present invention can achieve the same effects as the load sensor of the present invention described above. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a vertical cross-sectional view showing a load sensor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged vertical cross-sectional view of the load sensor. [Figure 3] FIG. 10 is a vertical cross-sectional view showing a modified example of the load sensor. [Figure 4] FIG. 4 is a vertical cross-sectional view showing a load sensor according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a vertical cross-sectional view showing a modified example of the load sensor. [Figure 6] 3 is a longitudinal sectional view showing an example of the formation of a sensor member in the load sensor of the first embodiment. FIG. [Figure 7] FIG. 10 is a vertical cross-sectional view showing another example of the sensor member. [Figure 8] FIG. 10 is a vertical cross-sectional view showing an electric brake device including a modified example of the load sensor of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] A load sensor according to a first embodiment of the present invention will be described with reference to the drawings. As shown in the longitudinal cross section of Fig. 1, this load sensor includes a single sensor member 1, a displacement sensor 2, and a sensor target 3, and is attached to a support portion 5 of an electric brake device, for example. When a load is applied to the sensor member 1 in an application direction F (downward in Fig. 1) from a load application side (upper side in Fig. 1) that faces a support side (lower side in Fig. 1) on which the sensor member 1 is supported, the sensor member 1 deforms and the displacement sensor 2 and the sensor target 3 are displaced relative to each other, and the magnitude of the applied load is detected based on the amount of relative displacement between the displacement sensor 2 and the sensor target 3 detected by the displacement sensor 2.

[0019] The sensor member 1 is a hollow disk (also called a perforated disk or annular plate) having a central axis C, and in a longitudinal section (cross section shown in FIG. 1) along the central axis C parallel to the load application direction F, the sensor member 1 has a space S surrounded by the sensor member 1 in all three directions (upward and downward in FIG. 1) and at least a part of one direction (downward in FIG. 1) out of four directions: the front-rear direction parallel to the central axis C (upward and downward in FIG. 1) and the front-rear direction perpendicular to the central axis C (left-right direction in FIG. 1). Specifically, the space S is also a hollow disk having the central axis C.

[0020] The sensor member 1 has an opening 1a on the support side that communicates with the space S, and the opening 1a is also a hollow disk shape having a central axis C. Therefore, in the vertical cross section of Fig. 1, the space S is not surrounded by the sensor member 1 only at the radially inner side in one direction (the downward direction in Fig. 1) out of the four directions. The opening 1a may also communicate with the radially outer side of the space S (see Fig. 3).

[0021] As shown in Fig. 6, the sensor member 1 can be formed by joining a first material part 1A including a portion on the load application side of the space S and a second material part 1B including a portion on the support side of the space S at an annular joining surface J perpendicular to the central axis C so that the sensor member 1 is not divided into multiple parts. When the first material part 1A and the second material part 1B are made of metal, laser welding, electron beam welding, diffusion welding, friction welding, etc. can be used as the joining method. As shown in Fig. 7, the joining surface J may be in the shape of a cylindrical side surface having the central axis C.

[0022] Here, if the material of the first material portion 1A has a higher yield stress than the material of the second material portion 1B, a stronger material can be used in the portion where the load is primarily applied, making it easier to balance strength with cost or weight. Furthermore, if the first material portion 1A and the second material portion 1B are made of iron-based materials and the carbon content of the first material portion 1A is higher, a stronger material can be used in the first material portion 1A where the load is primarily applied, and a material with excellent processability can be used in the portion where the load is relatively light, making it easier to balance strength with cost. Depending on the application of the load sensor, at least one of the materials of the first material portion 1A and the second material portion 1B may be made of a metal material other than iron-based, such as aluminum, or a resin material. In this case, it is easier to balance strength with cost or weight. Furthermore, particularly when a resin material is used, the joint can be easily joined by heating.

[0023] In the load sensor of the first embodiment, the sensor member 1, the space S, and the opening 1a are in the shape of a hollow disk (also called a perforated disk or annular plate), but depending on the application of the load sensor, they may also be in the shape of a perforated polygonal plate.

[0024] 1, for example, a magnetic sensor and a permanent magnet can be fixed to the sensor member 1. The magnetic sensor can be a Hall element, an MI element, an MR element, or the like, and the permanent magnet can be a first permanent magnet 3a with an N pole on the displacement sensor 2 side and a second permanent magnet 3b with an S pole on the displacement sensor 2 side, lined up in the direction of the central axis C (see FIG. 2). The up-down relationship of the first permanent magnet 3a and the second permanent magnet 3b can be reversed from that in FIG. 2.

[0025] Depending on the application of the load sensor, an inductance measurement sensor and an inductance varying shape portion in which the inductance measured varies with displacement in the direction of the central axis C may be used as the displacement sensor 2 and the sensor target 3. The inductance varying shape portion may be a stepped portion or an inclined portion in the direction of the central axis C. Also, depending on the application of the load sensor, a capacitance sensor or an optical sensor may be used as the displacement sensor 2.

[0026] The displacement sensor 2 and the sensor target 3 are disposed in the opening 1a of the sensor member 1, facing each other in the radial direction with respect to the central axis C, with the displacement sensor 2 disposed radially outward of the sensor target 3. In general use of a load sensor, it is assumed that the wiring will ultimately be drawn outward from the displacement sensor, but if the displacement sensor 2 is disposed radially outward of the sensor target 3, wiring of the displacement sensor 2 is easy. Note that multiple sets of displacement sensors 2 and sensor targets 3 may be disposed circumferentially in the opening 1a of the sensor member 1 to improve detection accuracy and redundancy. In this case, the first permanent magnet 3a and the second permanent magnet 3b in FIG. 2 may each be connected in the shape of a hollow disk having the central axis C.

[0027] As described above, in the load sensor of the first embodiment, the sensor member 1 is single and has a shape having the space S as described above, so that the displacement sensor 2 and the sensor target 3 undergo a relatively large relative displacement, and no sliding friction occurs between the multiple sensor members, so that sufficient detection accuracy can be obtained with a simple configuration.

[0028] A load sensor according to a second embodiment of the present invention will be described with reference to the drawings, focusing on only the differences from the load sensor according to the first embodiment. As shown in the longitudinal cross section of Figure 4, in the load sensor according to the second embodiment, the sensor member 1 has a hollow disc-shaped protrusion 1b on the load application side that protrudes in the direction of the central axis C.

[0029] This load sensor further includes a stay member 4a that fits snugly onto the end face and inner circumferential surface of the convex portion 1b (fitting snugly against the inner circumferential surface of the convex portion 1b and abutting against the end face of the convex portion 1b), and a load applied to the stay member 4a is transmitted to the sensor member 1 via at least the end face (top surface in Figure 4) of the convex portion 1b. The stay member 4a also serves as the fixed raceway of the thrust cylindrical roller bearing 4 attached to the sensor member 1, and the thrust cylindrical roller bearing 4 has the fixed raceway 4a, rolling elements 4b which are cylindrical rollers, a cage 4c, and a rotating raceway 4d. Note that a stay member made of inexpensive general steel may also be used, and a fixed raceway of the thrust cylindrical roller bearing 4 may be provided separately from the stay member.

[0030] In this configuration, the stay member 4a is counter-fitted onto the end face and inner peripheral surface of the protrusion 1b of the sensor member 1, thereby suppressing radial inward displacement of the protrusion 1b of the sensor member 1 when a load is applied, thereby mitigating radial slippage between the sensor member 1 and the stay member 4a around the central axis C. Furthermore, because the protrusion 1b of the sensor member 1 has a relatively low rigidity, it is possible for the rigidity of the stay member 4a to prevent the deformation of the sensor member 1 from being hindered. This makes it possible to improve detection accuracy while maintaining the required sensor sensitivity.

[0031] In this load sensor, a load applied to the rotating raceway 4d of the thrust cylindrical roller bearing 4 is applied to an annular pressure area P, which is the raceway surface of the cylindrical rollers 4b, on the surface of the stay member 4a, which is the fixed raceway, and the average radius r1 of the protrusions 1b from the central axis C is equal to the average radius r2 of the pressure area P from the central axis C. This configuration can sufficiently increase the rigidity of the stay member 4a against the load. However, as a modified example, as shown in FIG. 5, the average radius r1 of the protrusions 1b from the central axis C may be larger than the average radius r2 of the pressure area P from the central axis C. This configuration further reduces the amount of elastic deformation at the contact position between the sensor member 1 and the stay member 4a, thereby further reducing sliding friction in the radial direction between the sensor member 1 and the stay member 4a and further improving detection accuracy.

[0032] According to the load sensor of the second embodiment, in addition to the effects of the load sensor of the first embodiment, the effects of the additional configuration described above are exerted.

[0033] The present invention also includes an electric brake device that uses any of the load sensors of the present invention described above to control the magnitude of braking force. As an example, FIG. 8 shows a longitudinal cross-sectional view of an electric brake device equipped with a modified version of the load sensor of the second embodiment. This electric brake device includes a caliper 11, a linear actuator 12 that uses, for example, an electric motor 12b as a rotational drive source to linearly move a linear moving part 12a, a brake rotor 10, and friction pads 13 and 14. The linear moving part 12a moves the friction pads 13 and 14 toward and away from the brake rotor 10. The modified version of the load sensor of the second embodiment, which includes a single sensor member 1, a displacement sensor 2, sensor targets 3a and 3b, etc., is attached to a support part 5 of the electric brake device. In the following description, when the electric brake device is mounted on a vehicle, the outer side of the vehicle in the vehicle width direction is referred to as the outboard side OS, and the center side of the vehicle in the vehicle width direction is referred to as the inboard side IS.

[0034] In this electric brake device, during braking, the friction pads 14 on the inboard side IS come into contact with the brake rotor 10 due to the drive of the linear actuator 12, i.e., the linear motion of the linear motion portion 12a, and press the brake rotor 10 in the direction of the central axis C. A reaction force from this pressing force causes the caliper 11, which is integrated with the housing of the linear motion actuator 12 and is slidable in the direction of the central axis C, to slide to the inboard side IS. As a result, the friction pads 13 on the outboard side OS, which are supported by the caliper 11, come into contact with the brake rotor 10. The friction pads 13, 14 on the outboard side OS and inboard side IS tightly grip the brake rotor 10 from both sides in the direction of the central axis C, and a braking force is applied to the brake rotor 10. At this time, the load sensor detects the load applied to the friction pads 13, 14. The electric brake device of the present invention illustrated above provides the same effects as the load sensor of the present invention described above. [Explanation of symbols]

[0035] 1. Sensor component 1a opening 1b Convex part 1A 1st Materials Department 1B 2nd Material Department 2. Displacement Sensor 3 Sensor Target 4a Stay member 10 Brake rotor 11 Caliper 12 Linear Actuator 12a Linear motion section 13,14 Friction pads C center axis F Load application direction P pressure area r1 Average radius of the convex part r2 Average radius of the pressure area S space

Claims

1. a single sensor member, a displacement sensor, and a sensor target; When a load is applied to the sensor member from a load application side opposite to a support side on which the sensor member is supported, the sensor member is deformed and the displacement sensor and the sensor target are displaced relative to each other, a load sensor that detects the magnitude of the load based on a relative displacement amount between the displacement sensor and the sensor target detected by the displacement sensor, the sensor member has a space surrounded by the sensor member in all three directions and at least a part of one direction among four directions, i.e., a front-rear direction parallel to the central axis and a front-rear direction perpendicular to the central axis, in a longitudinal cross section along the central axis of the sensor member parallel to the load application direction, and has a hollow disk-shaped convex portion on the load application side that protrudes in the direction of the central axis, the load sensor includes a stay member that is counter-fitted onto the end surface and the inner circumferential surface of the protrusion, A load sensor in which a load applied to the stay member is transmitted to the sensor member via at least an end face of the convex portion.

2. The load sensor according to claim 1, The sensor member has an opening communicating with the space on the support side.

3. The load sensor according to claim 1, the load is applied to an annular pressure region on the surface of the stay member, A load sensor in which the average radius of the convex portion from the central axis is larger than the average radius of the pressure region from the central axis.

4. The load sensor according to any one of claims 1 to 3, The displacement sensor and the sensor target are provided to face each other in a radial direction with respect to the central axis, and the displacement sensor is disposed radially outward of the sensor target.

5. The load sensor according to any one of claims 1 to 4, a first material part including a portion on the load application side of the space and a second material part including a portion on the support side of the space are joined together without a boundary that allows separation into a plurality of members to form the sensor member, A load sensor wherein the material of the first material portion has a higher yield stress than the material of the second material portion.

6. The load sensor according to claim 5, A load sensor in which the first material portion and the second material portion are made of iron-based materials, and the material of the first material portion has a higher carbon content.

7. An electric brake device comprising: a caliper; a linear actuator having a linear motion part that moves linearly; a brake rotor; and a friction pad; wherein the linear motion part brings the friction pad into contact with and separates the brake rotor, An electric brake device comprising the load sensor according to any one of claims 1 to 6, wherein the load sensor detects a load applied to the friction pad.

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