Load sensor device

Abstract

To provide a load sensor device that can achieve both high accuracy of a detection value and excellent impact resistance.SOLUTION: A load sensor device comprises: a load sensor that has a pressure receiving portion; a housing that accommodates the load sensor; an elastic body that receives a load and presses against the load sensor; and a pressing member that is provided between the elastic body and the load sensor. The pressing member includes a rigid pressing portion capable of coming into contact with the pressure receiving portion, and an elastic support portion that supports the rigid pressing portion on the housing. A gap is provided between the rigid pressing portion and the pressure receiving portion in a state where the load is not applied to the elastic body. When the load is applied to the elastic body, the elastic support portion elastically deforms to reduce the gap between the rigid pressing portion and the pressure receiving portion, and the load sensor device includes a shock absorbing portion capable of alleviating elastic deformation of the elastic support portion.SELECTED DRAWING: Figure 2

Description

【Technical Field】 【0001】 The present invention relates to a load sensor device for detecting a load. 【Background Art】 【0002】 In recent years, load sensor devices for detecting loads have been widely used in electronic devices and the like. Patent Document 1 discloses a pressure-sensitive element having a pressure-sensitive surface on which a first electrode is formed and a second electrode, wherein an electrical physical property value between the first electrode and the second electrode changes according to a pressure acting on the pressure-sensitive surface; a pressurizing member having conductivity; and a support portion that supports the pressurizing member such that one end portion of the pressurizing member contacts the first electrode of the pressure-sensitive element when a load of a predetermined value or more in the direction of the first electrode of the pressure-sensitive element is applied to the pressurizing member. A pressure sensor is disclosed which is used in such a manner that it is determined whether or not a load is applied to the pressurizing member based on a measurement result of an electrical physical property value between the pressurizing member and the second electrode of the pressure-sensitive element. 【0003】 Patent Document 2 discloses a load detection device including a magnetostrictive load sensor that detects a load by flowing a current through a coil to magnetize a magnetic material, applying a load to the magnetic material to change its magnetic characteristics, and converting the change in the magnetic characteristics into a voltage change for output, wherein an overload prevention mechanism including an elastic body is provided in the magnetostrictive load sensor or a load detection system including the same. 【0004】 Patent Document 3 discloses a panel switch including a switch unit configured by bonding a diaphragm made of a springy metal concentrically and in contact with a horseshoe-shaped contact formed on an insulating substrate or insulating sheet and a substantially circular contact adjacent to the inside thereof using a tape; a button provided with a rod for pressing the central portion of the diaphragm on the lower surface; and a damper sheet made of silicon rubber or foaming material sandwiched between the diaphragm of the switch unit and the rod of the button. 【Prior Art Documents】 [Patent Documents] 【0005】 [Patent Document 1] Japanese Patent Publication No. 2015-152429 [Patent Document 2] Japanese Patent Publication No. 2001-281074 [Patent Document 3] Patent No. 2926970 [Overview of the Initiative] [Problems that the invention aims to solve] 【0006】 Load sensor devices that detect loads require high detection accuracy and linearity of the detected value with respect to load, and it is preferable that they have resistance to impacts that may be applied during the manufacturing process or use. 【0007】 This invention was made in view of these circumstances, and aims to provide a load sensor device that can achieve high accuracy in detected values ​​as well as excellent shock resistance. [Means for solving the problem] 【0008】 The inventors of this application, as a result of their studies from the perspective of improving the accuracy of detected values, found that it is desirable for the member that presses against the pressure-receiving part of the load sensor when a load is applied (pressing member) and the pressure-receiving part to be non-contact in the unloaded state. However, it also became clear that if they are non-contact in the unloaded state, the pressing member and the pressure-receiving part may collide when subjected to an external impact, and this collision may damage the load sensor. As a result of further studies, they found that by mitigating the excessive deformation and deformation rate of the member that elastically supports the rigid pressing member when the rigid pressing member is displaced toward the pressure-receiving part under a load, the possibility of the load sensor being damaged when subjected to the aforementioned impact can be reduced. 【0009】 Based on the above findings, the present invention, in one embodiment, comprises a load sensor having a pressure-receiving portion, a housing for housing the load sensor, an elastic body that receives a load and presses the load sensor, and a pressing member provided between the elastic body and the load sensor, wherein the pressing member has a rigid pressing portion that can contact the pressure-receiving portion and an elastic support portion that supports the rigid pressing portion in the housing, and when no load is applied to the elastic body, a gap is provided between the rigid pressing portion and the pressure-receiving portion, and when a load is applied to the elastic body, the elastic support portion elastically deforms to reduce the gap between the rigid pressing portion and the pressure-receiving portion, and is equipped with a buffer portion that can mitigate the elastic deformation of the elastic support portion. 【0010】 With this configuration, by giving elasticity to the pressing member, when the elastic body is pressed, the load can be transmitted from the elastic body to the pressure-receiving part via the elastic support part and the rigid pressing part. In this load sensor device, when an impact is applied to the pressing member, the cushioning part mitigates the elastic deformation of the elastic support part, thereby reducing the displacement velocity of the rigid pressing part and mitigating the impact force transmitted from the rigid pressing part to the pressure-receiving part. 【0011】 In the above-described load sensor device, the elastic support portion may have a leaf spring portion extending from the rigid pressing portion in a direction intersecting the load application direction. Alternatively, the leaf spring portion may be provided integrally with the rigid pressing portion. In this way, having a leaf spring portion extending from the rigid pressing portion in a direction intersecting the load application direction allows for more stable and space-saving support of the rigid pressing portion compared to a coil spring, and also facilitates the transmission of the load to the pressure receiving portion. 【0012】 In the above-described load sensor device, the buffer portion may have a first soft elastic member positioned on the side of the pressing member facing the load sensor. This allows the elastically deformable elastic support portion to come into contact with the first soft elastic member when an impact is applied to the pressing member, thereby mitigating the elastic deformation of the elastic support portion. 【0013】 In the above-described load sensor device, it is preferable that the first soft elastic member has a first through-hole, and that when a load is applied to the elastic body, the rigid pressing portion and the pressure receiving portion can come into contact through the first through-hole. This allows the rigid pressing portion to come into direct contact with the pressure receiving portion through the first through-hole, even if the first soft elastic member is provided on the side of the pressing member facing the load sensor, and the load of the pressing member can be transmitted to the pressure receiving portion without the first soft elastic member being interposed. 【0014】 In the above load sensor device, the buffer portion may have a second soft elastic member positioned on the side opposite to the elastic body of the leaf spring portion. This allows the elastically deformable elastic support portion to come into contact with the second soft elastic member when an impact is applied to the pressing member, thereby mitigating the elastic deformation of the elastic support portion. 【0015】 In the above load sensor device, the second soft elastic member has a second through hole, and it is preferable that when a load is applied to the elastic body, the elastic body or the member placed between the elastic body and the rigid pressing part and the rigid pressing part come into contact through the second through hole. As a result, even if the second soft elastic member is provided on the side of the leaf spring facing the elastic body, the elastic body or the member placed between the elastic body and the rigid pressing part and the rigid pressing part can come into direct contact through the second through hole, and the load can be transmitted from the elastic body to the pressing member without the second soft elastic member being interposed. 【0016】 In the above-described load sensor device, the buffer portion may have a portion made of a fluid material having buffering properties within the housing. This reduces the displacement velocity of the rigid pressing portion by the portion made of the fluid material, thereby mitigating the impact force transmitted from the rigid pressing portion to the pressure receiving portion. 【0017】 In the above-described load sensor device, the housing may have a stopper that restricts the amount of deformation of the elastic body in the direction of the applied load when a load is applied to the elastic body. This allows the amount of deformation of the elastic body to be restricted by the stopper when an overload is applied to the elastic body, thereby protecting the load sensor from overload. 【0018】 In the above load sensor device, the peripheral edge of the pressing member may be fixed to the housing. This allows the peripheral edge of the pressing member to be supported by the housing, and the central portion of the pressing member to be displaced so as to flex with the peripheral edge of the pressing member as a fulcrum. 【0019】 In the above-described load sensor device, it is preferable that, when viewed from the direction of load application, the rigid pressing portion overlaps entirely with the elastic load receiving portion, and the pressure receiving portion overlaps entirely with the rigid pressing portion. This allows the load received by the elastic load receiving portion to be applied directly to the pressure receiving portion of the load sensor via the rigid pressing portion in the direction of load application. 【0020】 In the above-described load sensor device, the load sensor may have a displacement part that is displaced by the load received by the pressure-receiving part, and a plurality of piezoresistive elements that electrically detect the amount of displacement of the displacement part. In a load sensor using such a plurality of piezoresistive elements, the balance of the detected values ​​by the plurality of piezoresistive elements is easily disrupted when an impact is applied to the pressure-receiving part. As described above, by mitigating the elastic deformation of the elastic support part with the buffer part and mitigating the impact force transmitted from the rigid pressing part to the pressure-receiving part, it becomes easier to maintain the balance of the detected values ​​by the plurality of piezoresistive elements even when an impact is applied. 【0021】 In the above-described load sensor device, it is preferable that the buffer portion is provided in contact with the elastic support portion. This allows the buffer portion to effectively mitigate the elastic deformation when the elastic support portion undergoes elastic deformation. 【0022】 In the above-described load sensor device, the buffer portion includes a gel-like resin that adheres to the elastic support portion. This allows the gel-like resin to effectively mitigate the elastic deformation of the elastic support portion when it undergoes elastic deformation. 【0023】 In the above-described load sensor device, a rigid plate portion may be provided between the elastic body and the rigid pressing portion. By providing such a rigid plate portion, the escape of load transmitted from the elastic body to the rigid pressing portion can be suppressed, thereby improving measurement accuracy. 【Advantages of the Invention】 【0024】 According to the present invention, it becomes possible to provide a load sensor device capable of obtaining excellent shock resistance while improving the accuracy of detection values. 【Brief Description of the Drawings】 【0025】 [Figure 1] It is a perspective view illustrating the configuration of the load sensor device according to the first embodiment. [Figure 2] It is a cross-sectional view taken along the line A-A of FIG. 1 illustrating the configuration of the load sensor device according to the first embodiment. [Figure 3] It is an exploded perspective view of the load sensor device according to the first embodiment. [Figure 4] It is a plan view illustrating the displacement portion of the load sensor. [Figure 5] It is a perspective view illustrating the arrangement of the buffer portion of the load sensor device according to the first embodiment. [Figure 6] (a) and (b) are diagrams illustrating the operation of the load sensor device according to the present embodiment. [Figure 7] It is an exploded perspective view of the load sensor device according to the second embodiment. [Figure 8] It is a cross-sectional view illustrating the configuration of the load sensor device according to the second embodiment. [Figure 9] It is an exploded perspective view of the load sensor device according to the third embodiment. [Figure 10] It is a cross-sectional view illustrating the configuration of the load sensor device according to the third embodiment. [Figure 11] It is an exploded perspective view of the load sensor device according to the fourth embodiment. [Figure 12] It is a cross-sectional view illustrating the configuration of the load sensor device according to the fourth embodiment. [Figure 13] It is a cross-sectional view illustrating the configuration of the load sensor device according to the fifth embodiment. [Figure 14] It is a diagram illustrating the result of the load test of Example 1 of the present invention. [Figure 15]This figure illustrates the results of a load test according to Example 2 of the present invention. [Figure 16] This figure illustrates the results of a load test according to Example 3 of the present invention. [Figure 17] This figure shows the results of the load tests in Examples 1 to 3 of the present invention. [Figure 18] This figure shows the results of the load tests in Examples 4 to 6 of the present invention. [Figure 19] This figure illustrates the results of a load test for a comparative example. [Figure 20] This figure illustrates the results of a load test for a comparative example. [Figure 21] This figure shows the results of the load tests in Reference Examples 1 and 2. [Modes for carrying out the invention] 【0026】 Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description, the same reference numerals will be used for identical components, and components that have already been described will be omitted from the description as appropriate. 【0027】 (First Embodiment) Figure 1 is a perspective view illustrating the configuration of a load sensor device according to the first embodiment. Figure 2 is a cross-sectional view along line AA in Figure 1, illustrating the configuration of the load sensor device according to the first embodiment. Figure 3 is an exploded perspective view of the load sensor device according to the first embodiment. Figure 4 is a plan view illustrating the displacement section of a load sensor. Figure 5 is a perspective view illustrating the arrangement of the buffer section of the load sensor device according to the first embodiment. 【0028】 The load sensor device 1 according to the first embodiment is a device that receives an external load and outputs a signal corresponding to that load. The load sensor device 1 comprises a load sensor 10, a housing 20 that houses the load sensor 10, an elastic body 31 that receives the load and presses the load sensor 10, and a pressing member 30 provided between the elastic body 31 and the load sensor 10. In the description of the embodiment, the direction normal to the mounting surface of the load sensor 10 in the housing 20 is the Z direction, one of the directions perpendicular to the normal direction (Z direction) is the X direction, and the other one is the Y direction. 【0029】 The load sensor 10 comprises a pressure-receiving section 11 and a sensor substrate 12. The pressure-receiving section 11 is provided projecting, for example, in a cylindrical shape from the upper surface of the sensor substrate 12 and is the part that receives external loads. The pressure-receiving section 11 is made of a silicon compound or silicon (the same material as the sensor substrate 12). 【0030】 The sensor substrate 12 has a displacement section 121 that is displaced by the load received by the pressure receiving section 11, and a plurality of piezoresistive elements 122 that electrically detect the amount of displacement of the displacement section 121. The sensor substrate 12 is bonded to the base substrate 13, for example, by diffusion bonding of Au, and the base substrate 13 is connected to the housing 20 by die bond resin 14. The displacement section 121 is the part that is displaced by the load received by the pressure receiving section 11, and is provided on the side of the sensor substrate 12 opposite to the pressure receiving section 11. 【0031】 The piezoresistive element 122 is an element that electrically detects the amount of displacement of the displacement section 121. Multiple piezoresistive elements 122 are provided on the displacement section 121. The multiple piezoresistive elements 122 are arranged along the periphery of the displacement section 121, with adjacent elements having a phase difference of 90° (a mutually orthogonal positional relationship). When the displacement section 121 is displaced by the load received by the pressure receiving section 11, the electrical resistance of the multiple piezoresistive elements 122 changes according to the amount of displacement, and the midpoint potential of the bridge circuit formed by these multiple piezoresistive elements 122 changes, and this midpoint potential becomes the sensor output. 【0032】 The housing 20 is formed, for example, in a box shape and has an edge portion 21 and a storage portion 22 which is a central recess. The edge portion 21 is the uppermost surface of the housing 20 and acts as a stopper to restrict the amount of deformation of the elastic body 31 in the direction of load application (Z direction) when subjected to an external load. 【0033】 The load sensor 10 is housed in the storage compartment 22. The storage compartment 22 is provided with a pad, and the housed load sensor 10 and the pad are electrically connected by a bonding wire 15. A resin (not shown) may be embedded inside the storage compartment 22 for the purpose of protecting the bonding wire 15 and other components. 【0034】 A stepped portion 23 is provided on the inside of the edge portion 21 so as to surround the storage portion 22. The cushioning portion 50 and the rigid pressing portion 32 of the pressing member 30, which will be described later, are placed on the stepped portion 23. 【0035】 The pressing member 30 has a rigid pressing portion 32 that contacts the pressure receiving portion 11 and an elastic support portion 33 that supports the rigid pressing portion 32 on the housing 20. An elastic body 31 that receives external loads is provided on the pressing member 30. The elastic body 31 has a protruding portion 311 and a flange portion 312. The elastic body 31 is formed of, for example, rubber. The protruding portion 311 is provided in a cylindrical shape, for example, and the flange portion 312 has a surface for placing the protruding portion 311 on the rigid pressing portion 32. 【0036】 The rigid pressing portion 32 is a plate-shaped member and is made of a material harder than the elastic body 31. For example, a stainless steel plate about 0.2 mm thick is used for the rigid pressing portion 32. Silicon, ceramics, glass, aluminum, etc. may also be used for the rigid pressing portion 32. The elastic modulus of the rigid pressing portion 32 is higher than that of the elastic body 31, and a preferred elastic modulus is 60 GPa or higher. 【0037】 When viewed from the load application direction (Z direction), it is preferable that the entire rigid pressing portion 32 overlaps with the load receiving portion of the elastic body 31, and the entire pressure receiving portion 11 overlaps with the rigid pressing portion 32. This allows the load received by the load receiving portion of the elastic body 31 to be applied directly to the pressure receiving portion 11 of the load sensor 10 via the rigid pressing portion 32 in the load application direction. 【0038】 The elastic support portion 33 has a frame portion 331 and an arm portion 332. The elastic support portion 33 is connected to the rigid pressing portion 32 by a connecting portion 332a provided between the arm portion 332 and the rigid pressing portion 32. The frame portion 331 is provided with a positioning hole 331h. The stepped portion 23 of the housing 20 on which the frame portion 331 is placed is provided with a positioning projection 23a. When the frame portion 331 is placed on the stepped portion 23, the projection 23a fits into the positioning hole 331h, determining the placement position of the elastic support portion 33. 【0039】 The arm portion 332 is a leaf spring portion 330 that extends from the rigid pressing portion 32 in a direction intersecting the load application direction. The rigid pressing portion 32 is supported by the elastic deformation of the arm portion 332 with a predetermined spring constant. This spring constant is adjusted by the material of the arm portion 332, as well as its width, thickness, length, and shape. For example, the spring constant of the arm portion 332 of the elastic support portion 33 becomes smaller as the width of the connecting portion 332a narrows, making it easier to obtain a soft pre-stroke feeling. On the other hand, the wider the width of the connecting portion 332a, the larger the spring constant of the arm portion 332, making it easier to obtain a pressing feeling. 【0040】 The symmetrical arrangement of the arm portion 332 in a leaf spring shape around the rigid pressing portion 32 facilitates the transmission of the load from the elastic body 31 to the pressure receiving portion 11 directly below. Furthermore, supporting the rigid pressing portion 32 with the leaf spring portion 330 (arm portion 332) extending in a direction intersecting the load application direction allows for more stable and space-saving support of the rigid pressing portion 32 compared to supporting it with a coil spring extending in the load application direction. The leaf spring portion 330 may be provided integrally with the rigid pressing portion 32. 【0041】 Furthermore, by giving elasticity to the pressing member 30, when the elastic body 31 is pressed, the load can be transmitted from the elastic body 31 to the pressure-receiving part 11 of the load sensor 10 via the elastic support part 33 and the rigid pressing part 32. In this case, since the rigid pressing part 32 that contacts the pressure-receiving part 11 is made of a highly rigid material (such as metal or silicon), the escape of the load is suppressed, and the detection sensitivity can be increased. 【0042】 In a configuration where the load sensor 10 obtains output using a bridge circuit with multiple piezoresistive elements 122, it is necessary to efficiently displace the displacement part 121 by receiving the load with the convex pressure receiving part 11. For this reason, when transmitting the load from the pressing member 30 to the pressure receiving part 11, if the rigidity of the member in contact with the pressure receiving part 11 is low, the load cannot be effectively transmitted to the pressure receiving part 11. In this embodiment, the pressure receiving part 11 is pressed by the rigid pressing part 32, which suppresses the escape of the load from the outside and allows the load to be efficiently transmitted to the pressure receiving part 11. 【0043】 In the load sensor device 1, when no load (including impact) is applied to the elastic body 31 (no-load state), a gap d is provided between the rigid pressing part 32 and the pressure receiving part 11. When a load is applied to the elastic body 31, the elastic support part 33 elastically deforms to reduce the gap d between the rigid pressing part 32 and the pressure receiving part 11. As the rigid pressing part 32 and the pressure receiving part 11 come into contact, the load applied to the elastic body 31 is transmitted to the load sensor 10. 【0044】 In such a load sensor device 1, a buffer portion 50 is provided that can mitigate the elastic deformation of the elastic support portion 33. The buffer portion 50 plays a role in reducing the displacement speed when the rigid pressing portion 32 is displaced due to the elastic deformation of the elastic support portion 33. 【0045】 The buffer portion 50 has a first soft elastic member 51 positioned on the side of the pressing member 30 facing the load sensor 10. The first soft elastic member 51 is made of an impact-absorbing material with a large loss tangent (tanδ) as a dynamic viscoelastic property, such as silicone, synthetic rubber, urethane, or gel-like resin. 【0046】 The first soft elastic member 51 may be provided in constant contact with the elastic support portion 33, or it may be provided so as to contact the elastic support portion 33 when it undergoes elastic deformation. As a result, when an impact is applied to the pressing member 30, the elastically deforming elastic support portion 33 comes into contact with the first soft elastic member 51, mitigating the elastic deformation of the elastic support portion 33 and reducing the displacement speed of the rigid pressing portion 32. 【0047】 The first soft elastic member 51 has a first through hole 51h. As a result, when a load is applied to the elastic body 31, the rigid pressing portion 32 and the pressure receiving portion 11 can come into contact through the first through hole 51h. In other words, even if the first soft elastic member 51 is provided on the side of the pressing member 30 facing the load sensor 10, when the rigid pressing portion 32 comes into contact with the pressure receiving portion 11, the rigid pressing portion 32 and the pressure receiving portion 11 can come into direct contact through the first through hole 51h, and the load of the pressing member 30 can be transmitted to the pressure receiving portion 11 without the interposition of the first soft elastic member 51. 【0048】 In the load sensor device 1 according to this embodiment, when an impact is applied to the pressing member 30, the cushioning portion 50 can reduce the displacement speed of the rigid pressing portion 32, thereby mitigating the impact load applied to the pressure receiving portion 11 of the load sensor 10. This increases the impact load resistance of the load sensor 10. Furthermore, when a normal load is applied, the rigid pressing portion 32 and the pressure receiving portion 11 come into direct contact through the first through-hole 51h, allowing the load to be efficiently transmitted to the pressure receiving portion 11 and enabling highly accurate load detection. 【0049】 (Assembly of load sensor device) In the above configuration, the load sensor 10 is housed in the storage section 22 of the housing 20, and the load sensor 10 and the pad of the storage section 22 are connected by a bonding wire 15. A sheet-like first soft elastic member 51, which is a buffer section 50, is placed in the stepped section 23 of the storage section 22. The first through hole 51h of the first soft elastic member 51 is positioned to overlap with the pressure receiving section 11 when viewed in the Z direction. The pressing member 30 is placed on the first soft elastic member 51. Furthermore, an elastic body 31 is placed on the rigid pressing section 32. 【0050】 Then, the frame 40 is placed over the housing 20 in this state. The frame 40 is secured by hooking it onto hooks 25 provided on the side of the housing 20. A hole 40h is provided in the center of the frame 40, and when the frame 40 is placed over the housing 20, the protruding portion 311 protrudes upward from the hole 40h. The elastic body 31 is pressed down by the frame 40 at the flange portion 312. As a result, the pressing member 30 is fixed to the housing 20. 【0051】 In the load sensor device 1 assembled in this manner, when no load is applied to the pressing member 30, a gap d is provided between the rigid pressing portion 32 and the pressure receiving portion 11. That is, the surface of the pressure receiving portion 11 on the rigid pressing portion 32 does not come into contact with the pressure receiving portion 11. The gap d between the rigid pressing portion 32 and the pressure receiving portion 11 allows for tolerances to be provided during assembly. 【0052】 In other words, if the rigid pressing part 32 and the pressure receiving part 11 are in contact, or are so close that they are about to contact, there is a possibility that the rigid pressing part 32 and the pressure receiving part 11 may collide due to dimensional errors in each part or misalignment during assembly. If a highly rigid part like the rigid pressing part 32 collides with the pressure receiving part 11, it may adversely affect the load sensor 10. As in this embodiment, by providing a gap d between the rigid pressing part 32 and the pressure receiving part 11, collisions during assembly can be actively avoided and the load sensor 10 can be protected. 【0053】 (Operation of the load sensor device) Figures 6(a) and 6(b) illustrate the operation of the load sensor device according to this embodiment. Figure 6(a) shows an example of the state in which a load is applied to the load sensor device 1, and Figure 6(b) shows an example of the output of the load sensor. In Figure 6(b), the horizontal axis represents the stroke of the plate 90 in the Z direction, and the vertical axis represents the output value (relative value). 【0054】 As shown in Figure 6(a), a load is applied to the elastic body 31 of the pressing member 30 of the load sensor device 1 via the plate 90. When a load is applied to the elastic body 31 from the plate 90 in the Z direction, the rigid pressing part 32, which is supported by the spring action of the elastic support part 33, is pushed in the Z direction. 【0055】 Here, since a gap d is provided between the rigid pressing part 32 and the pressure receiving part 11 of the load sensor 10, no load is applied to the pressure receiving part 11 until the rigid pressing part 32 comes into contact with the pressure receiving part 11. 【0056】 Therefore, as shown in Figure 6(b), no output is generated on the load sensor device 1 until a predetermined stroke S1 is reached after the load has been applied. This region is called the pre-stroke region R1. In the pre-stroke region R1, when a load is applied, the elastic support portion 33 elastically deforms, and the pressing member 30 strokes until the rigid pressing portion 32 contacts the pressure receiving portion 11. However, the load is not transmitted to the pressure receiving portion 11, and the output value does not increase. The length of the pre-stroke region R1 can be set by the gap d. The load required for pre-stroke can also be set by the spring constant of the elastic support portion 33. 【0057】 Next, when a load is applied beyond the pre-stroke region R1, the output value increases in proportion to the stroke. This region is called the force-receiving region R2. In the force-receiving region R2, the rigid pressing part 32 is in contact with the pressure-receiving part 11, so the load is transmitted from the elastic body 31 to the pressure-receiving part 11 via the rigid pressing part 32. Due to the rigidity of the rigid pressing part 32 in contact with the pressure-receiving part 11, the output value from the load sensor 10 increases in proportion to the magnitude of the stroke (load). The output value increases up to V1 in proportion to the stroke. 【0058】 The force-receiving region R2 continues until the edge 21 of the housing 20 acts as a stopper. That is, as the pressing member 30 is pushed in, when the plate 90 hits the edge 21 of the housing 20, it is not pushed in any further. As a result, the stroke of the pressing member 30 stops at S2, the output value does not increase any further, and overloading of the load sensor 10 is prevented. 【0059】 (Second Embodiment) Figure 7 is an exploded perspective view of the load sensor device according to the second embodiment. Figure 8 is a cross-sectional view illustrating the configuration of a load sensor device according to the second embodiment. In the load sensor device 1B according to the second embodiment, the buffer portion 50 has a second soft elastic member 52. That is, the buffer portion 50 has a second soft elastic member 52 that is positioned on the side of the elastic support portion 33, which is a leaf spring portion 330, that faces the elastic body 31. In the second embodiment, the buffer portion 50 has both a first soft elastic member 51 and a second soft elastic member 52, but it may also have only a second soft elastic member 52. Alternatively, the second soft elastic member 52 and the elastic body 31 may be molded together. 【0060】 Because the cushioning portion 50 has a second soft elastic member 52, when an impact is applied to the pressing member 30, the elastically deformable elastic support portion 33 comes into contact with the second soft elastic member 52, thereby mitigating the elastic deformation of the elastic support portion 33. 【0061】 The second soft elastic member 52 has a second through hole 52h. As a result, when a load is applied to the elastic body 31, the elastic body 31 or the member placed between the elastic body 31 and the rigid pressing part 32 comes into contact with the rigid pressing part 32 through the second through hole 52h. In other words, even if the second soft elastic member 52 is provided on the side of the leaf spring facing the elastic body 31, the elastic body 31 or the member placed between the elastic body 31 and the rigid pressing part 32 can come into direct contact with the rigid pressing part 32 through the second through hole 52h, and the load can be transmitted from the elastic body 31 to the pressing member 30 without the second soft elastic member 52 being interposed. 【0062】 (Third embodiment) Figure 9 is an exploded perspective view illustrating the configuration of a load sensor device according to the third embodiment. Figure 10 is a cross-sectional view illustrating the configuration of a load sensor device according to the third embodiment. The load sensor device 1C according to the third embodiment includes a rigid plate portion 60 between the elastic body 31 and the rigid pressing portion 32, in addition to the configuration of the load sensor device 1 according to the first embodiment. The rigid plate portion 60 is a member having the same rigidity as the rigid pressing portion 32, and may be made of stainless steel or the like, just like the rigid pressing portion 32. 【0063】 In the load sensor device 1 described earlier, the elastic body 31 directly presses against the rigid pressing part 32. However, in the load sensor device 1C, the load received by the elastic body 31 is transmitted to the rigid pressing part 32 via the rigid plate part 60. The rigid plate part 60 has a protrusion 61 on the side facing the rigid pressing part 32, and can transmit force to the central part of the rigid pressing part 32 without interfering with other members. Therefore, the load received by the elastic body 31 is more easily transmitted to the load sensor 10, and sensitivity can be improved. 【0064】 (Fourth Embodiment) Figure 11 is an exploded perspective view illustrating the configuration of a load sensor device according to the fourth embodiment. Figure 12 is a cross-sectional view illustrating the configuration of a load sensor device according to the fourth embodiment. The load sensor device 1D according to the fourth embodiment includes, in addition to the configuration of the load sensor device 1B according to the second embodiment, a rigid plate portion 60 between the elastic body 31 and the rigid pressing portion 32, similar to the third embodiment. Since the protrusion 61 of the rigid plate portion 60 is positioned inside the second through hole 52h of the second soft elastic member 52, the protrusion 61 is in direct contact with the rigid pressing portion 32. As a result, similar to the load sensor device 1C according to the third embodiment, in the load sensor device 1D, the load received by the elastic body 31 is efficiently transmitted to the rigid pressing portion 32 via the rigid plate portion 60. Therefore, the load received by the elastic body 31 is easily transmitted to the load sensor 10, and sensitivity can be improved. 【0065】 (Fifth embodiment) Figure 13 is a cross-sectional view illustrating the configuration of a load sensor device according to the fifth embodiment. In the load sensor device 1E according to the fifth embodiment, the buffer portion 50 has a portion (fluid material portion 53) made of a buffering fluid material inside the housing 20. For example, silicone gel, silicone oil, elastomer, or gel-like or oil-like resin can be used for the fluid material portion 53. The fluid material portion 53 may also be formed by filling the storage portion 22 of the housing 20 with the above-mentioned gel or resin. 【0066】 The fluid material portion 53 may be provided in constant contact with the elastic support portion 33, or it may be provided so as to come into contact with the elastic support portion 33 when the elastic support portion 33 undergoes elastic deformation. This allows the elastic support portion 33 to come into contact with the fluid material portion 53 when an impact is applied to the pressing member 30, thereby mitigating the elastic deformation of the elastic support portion 33 and reducing the displacement speed of the rigid pressing portion 32. 【0067】 (Effects of the buffer) Next, the effects of the buffer section 50 applied in the load sensor device 1 according to this embodiment will be explained. To investigate the effect of the buffer section 50, a load test was conducted on the load sensor device. The load test involved dropping a weight onto the load sensor device from a height of approximately 9.2 cm to apply a load (impact load), and then measuring the change in the output of the load sensor device in relation to a normal load. In the load test, the weights of the dropped weights were 30g, 50g, 80g, and 100g. The initial value represents the state when no impact load is applied by the weights. 【0068】 The parameters measured in the load test were the sensitivity (mV / V / N), offset (mV / V), and the relative value of the offset to the initial value of the output of the load sensor device. Here, sensitivity is the output per unit load. Offset is the output under no-load conditions. This load test was performed on the load sensor device according to this embodiment equipped with a buffer section 50 (Examples 1 to 6 of the present invention), a load sensor device according to a comparative example without a buffer section 50 (Comparative Example), and a load sensor device according to a reference example (Reference Example). 【0069】 Table 1 shows the configurations and load test values ​​for Examples 1 to 3 of the present invention. Table 2 shows the configurations and load test values ​​for Examples 4 to 6 of the present invention. 【0070】 [Table 1] 【0071】 [Table 2] 【0072】 In the configuration of the load sensor devices according to Examples 1 to 3 of the present invention shown in Table 1, the hardness of the elastic body 31 is 80 (Shore A hardness; the notation for hardness is the same hereafter), and the die bond resin 14 is epoxy. Furthermore, the load sensor devices according to Examples 1 to 3 of the present invention are equipped with a rigid plate portion 60 between the elastic body 31 and the rigid pressing portion 32. The configuration of the load sensor device according to Example 1 of the present invention corresponds to the configuration of the load sensor device 1C according to the third embodiment (see Figures 9 and 10). In other words, in Example 1 of the present invention, only the first soft elastic member 51 is provided as the buffer portion 50, and its hardness is 30. The configurations of the load sensor devices according to Examples 2 and 3 of the present invention correspond to the configuration of the load sensor device 1D according to the fourth embodiment (see Figures 11 and 12). In other words, in Example 2 of the present invention, a first soft elastic member 51 and a second soft elastic member 52 are provided as a buffer portion 50, with the hardness of the first soft elastic member 51 being 20 and the hardness of the second soft elastic member 52 being 30. Also, in Example 3 of the present invention, a first soft elastic member 51 and a second soft elastic member 52 are provided as a buffer portion 50, with the hardness of the first soft elastic member 51 being 20 and the hardness of the second soft elastic member 52 being 20. 【0073】 In the configurations of the load sensor devices according to Examples 4 to 6 of the present invention shown in Table 2, the hardness of the elastic body 31 is 50. Regarding other configurations, Example 4 is the same as Example 1, Example 5 is the same as Example 2, and Example 6 is the same as Example 3. 【0074】 Figure 14 illustrates the results of a load test according to Example 1 of the present invention. Figure 15 illustrates the results of a load test according to Example 2 of the present invention. Figure 16 illustrates the results of a load test according to Example 3 of the present invention. In Figures 14-16, the horizontal axis represents the normal load applied to the load sensor device, and the vertical axis represents the output of the load sensor device. As shown in Figures 14-16, when impact loads of 30g, 50g, and 80g were applied, the output change (slope and output value) was almost the same as the initial value. On the other hand, when an impact load of 100g was applied, the slope of the output change for a normal load was almost the same as the initial value, but it could be seen that the output value was offset in the direction of decreasing. Therefore, the result was that even when subjected to an impact load of up to 80g, the cushioning effect of the buffer section 50 reduces the displacement velocity of the rigid pressing section 32 and mitigates the impact force transmitted to the pressure receiving section 11. 【0075】 The "relative offset value" in Tables 1 and 2 is the relative value obtained by dividing the offset amount for each weight by the initial offset amount. As shown in Tables 1 and 2, in Invention Examples 1 to 4 and 6, the relative offset value was approximately 1 when the weight was less than 100g, and the relative offset value deviated from 1 only when the weight was 100g. In Invention Example 5, the relative offset value was approximately 1 in all cases up to 100g of weight. 【0076】 Figure 17 shows the results of the load tests in Examples 1 to 3 of the present invention, corresponding to Table 1. Figure 18 shows the results of the load tests in Examples 4 to 6 of the present invention, corresponding to Table 2. In Figures 17 and 18, the horizontal axis represents the weight of the load test, and the vertical axis represents the offset. In all of Examples 1 to 6 of the present invention, it can be seen that there is almost no change in the offset of the output value even when subjected to an impact load of up to 80g. Furthermore, in Example 6 of the present invention, there is almost no change in the offset even when an impact load of 100g is applied. 【0077】 Table 3 shows the configuration and load test values ​​for the comparative example. 【0078】 [Table 3] 【0079】 In the configuration of the load sensor device according to the comparative example shown in Table 3, the hardness of the elastic body 31 is 80, and the die bond resin 14 is epoxy. The load sensor device according to the comparative example does not include either the first soft elastic member 51 or the second soft elastic member 52 in the buffer section 50. 【0080】 Figures 19 and 20 illustrate the results of load tests for comparative examples. In Figure 19, the horizontal axis represents the normal load applied to the load sensor device, and the vertical axis represents the output of the load sensor device. In Figure 20, the horizontal axis represents the weight of the load test weight, and the vertical axis represents the offset. As shown in Figures 19 and 20, in the comparative example load sensor device, when an impact load was applied with weights of 30g, 50g, 80g, and 100g, it can be seen that the output value is offset in the direction of decreasing as the weight increases. In Table 3, even with a weight of 30g, the relative offset value deviates significantly from 1, and a tendency for the relative offset value to increase as the weight increases was confirmed. 【0081】 From the results of the above load tests, it was confirmed that the load sensor devices according to Examples 1 to 6 of the present invention, which are equipped with a buffer portion 50, have superior impact resistance compared to the load sensor device according to the comparative example, which is not equipped with a buffer portion 50. This is thought to be because the buffer portion 50 mitigates the elastic deformation of the elastic support portion 33 when an impact load is applied, reducing the displacement speed of the rigid pressing portion 32, and thus preventing the rigid pressing portion 32 from making sudden contact (collision) with the pressure receiving portion 11. 【0082】 On the other hand, in the comparative example load sensor device that does not have a buffer section 50, an offset in the output value occurs even with a relatively small impact load. In particular, when the output is obtained by a bridge circuit using multiple piezoresistive elements 122 as the load sensor 10, the balance of the resistance values ​​of the bridge circuit is easily disrupted when an impact load is applied to the pressure receiving section 11. For this reason, in the comparative example load sensor device that does not have a buffer section 50, even a small impact load causes significant damage to the bridge circuit, and it is thought that the offset in the output value is pronounced. 【0083】 Table 4 shows the configuration and load test values ​​for Reference Examples 1 and 2. 【0084】 [Table 4] 【0085】 In the load sensor devices according to Reference Examples 1 and 2 shown in Table 4, the die bond resin 14 is silicone. The load sensor devices according to Reference Examples 1 and 2 do not include either the first soft elastic member 51 or the second soft elastic member 52 in the buffer section 50. In Reference Example 1, the hardness of the elastic body 31 is 80. In Reference Example 2, the hardness of the elastic body 31 is 50. 【0086】 Figure 21 shows the results of the load tests in Reference Examples 1 and 2, which correspond to Table 4. In Figure 21, the horizontal axis represents the weight of the load test weight, and the vertical axis represents the offset. In both of the reference examples 1 and 2, it can be seen that the offset of the output value hardly changes even when subjected to an impact load up to a weight of 80g. This result may indicate that by constructing the die bond resin 14 from a soft material, the same effect (improved impact resistance) as when a buffer section 50 is provided can be obtained. 【0087】 As described above, according to this embodiment, it is possible to provide load sensor devices 1, 1B, 1C, 1D, and 1E that can achieve high accuracy of detected values ​​as well as excellent shock resistance. 【0088】 Although the embodiments described above are examples, the present invention is not limited to these examples. For example, any additions, deletions, or design modifications of components to the aforementioned embodiments, or combinations of the features of the configuration examples of each embodiment, as appropriate by those skilled in the art, are also included within the scope of the present invention, as long as they retain the essence of the present invention. [Explanation of symbols] 【0089】 1, 1B, 1C, 1D, 1E... Load sensor devices 10... Load sensor 11...Pressure receiving section 12…Sensor board 13…Base board 14…Daibond resin 15…Bonding wire 20… Housing 21... Edge 22...Storage compartment 23... Stepped section 23a...Protrusion 25... Hook 30…Pressing member 31...Elastic body 32…Rigid pressing section 33...Elastic support section 40...frames 40h…hole 50...Buffer section 51...First soft elastic member 51h…1st through hole 52...Second soft elastic member 52h…Second through hole 53...Fluid substance part 60… Rigid plate section 61…Convex part 90... Plate 121...Displacement section 122... Piezoresistive element 311...Protruding part 312...Flange section 330... Leaf spring section 331...frame section 331h…hole 332...Arm section 332a…Connection part R1... Pre-stroke area R2…Receiving force area S1, S2... Stroke d...gap

Claims

[Claim 1] A load sensor having a pressure-receiving part, A housing for the load sensor, An elastic body that receives a load and presses against the load sensor, A pressing member provided between the elastic body and the load sensor, Equipped with, The pressing member is, A rigid pressing portion that can contact the pressure-receiving portion, The rigid pressing portion is supported by an elastic support portion that supports the housing, When no load is applied to the elastic body, a gap is provided between the rigid pressing portion and the pressure receiving portion. When a load is applied to the elastic body, the elastic support portion elastically deforms to reduce the gap between the rigid pressing portion and the pressure receiving portion. The elastic support portion is equipped with a buffer that can mitigate the elastic deformation of the elastic support portion, A load sensor device characterized in that the rigid pressing portion and the pressure receiving portion can come into direct contact with each other. [Claim 2] A load sensor having a pressure receiving part, A housing for the load sensor, An elastic body that receives a load and presses against the load sensor, A pressing member provided between the elastic body and the load sensor, Equipped with, The pressing member is, A rigid pressing portion that can contact the pressure-receiving portion, The rigid pressing portion is supported by an elastic support portion that supports the housing, When no load is applied to the elastic body, a gap is provided between the rigid pressing portion and the pressure receiving portion. When a load is applied to the elastic body, the elastic support portion elastically deforms to reduce the gap between the rigid pressing portion and the pressure receiving portion. A buffer portion capable of mitigating the elastic deformation of the elastic support portion is provided on the side of the elastic support portion facing the elastic body, A load sensor device characterized in that the elastic body and the rigid pressing portion can come into direct contact. [Claim 3] A load sensor having a pressure receiving part, A housing for the load sensor, An elastic body that receives a load and presses against the load sensor, A pressing member provided between the elastic body and the load sensor, Equipped with, The pressing member is, A rigid pressing portion that can contact the pressure-receiving portion, The rigid pressing portion is supported by an elastic support portion that supports the housing, When no load is applied to the elastic body, a gap is provided between the rigid pressing portion and the pressure receiving portion. When a load is applied to the elastic body, the elastic support portion elastically deforms to reduce the gap between the rigid pressing portion and the pressure receiving portion. The elastic support portion is equipped with a buffer that can mitigate the elastic deformation of the elastic support portion, The buffer portion has a first soft elastic member positioned on the side of the pressing member facing the load sensor. The first soft elastic member has a first through hole, A load sensor device characterized in that, when a load is applied to the elastic body, the rigid pressing portion and the pressure receiving portion can come into contact through the first through-hole. [Claim 4] A load sensor having a pressure receiving part, A housing for the load sensor, An elastic body that receives a load and presses against the load sensor, A pressing member provided between the elastic body and the load sensor, Equipped with, The pressing member is, A rigid pressing portion that can contact the pressure-receiving portion, The rigid pressing portion is supported by an elastic support portion that supports the housing, When no load is applied to the elastic body, a gap is provided between the rigid pressing portion and the pressure receiving portion. When a load is applied to the elastic body, the elastic support portion elastically deforms to reduce the gap between the rigid pressing portion and the pressure receiving portion. The elastic support portion is equipped with a buffer that can mitigate the elastic deformation of the elastic support portion, The elastic support portion has a leaf spring portion extending from the rigid pressing portion in a direction intersecting the load application direction, The cushioning portion has a second soft elastic member positioned on the side of the leaf spring portion facing the elastic body, The second soft elastic member has a second through hole, A load sensor device characterized in that, when a load is applied to the elastic body, the elastic body or a member disposed between the elastic body and the rigid pressing portion and the rigid pressing portion are in contact through the second through hole. [Claim 5] The load sensor device according to any one of claims 1, 2, and 4, wherein the buffer portion has a first soft elastic member disposed on the side of the pressing member facing the load sensor. [Claim 6] The load sensor device according to any one of claims 1 to 3, wherein the elastic support portion has a leaf spring portion extending from the rigid pressing portion in a direction intersecting the load application direction. [Claim 7] The load sensor device according to claim 6, wherein the leaf spring portion is provided integrally with the rigid pressing portion. [Claim 8] The load sensor device according to claim 6 or 7, wherein the buffer portion has a second soft elastic member disposed on the side of the leaf spring portion facing the elastic body. [Claim 9] The load sensor device according to any one of claims 1 to 8, wherein the housing has a stopper that restricts the amount of deformation of the elastic body in the direction of the applied load when a load is applied to the elastic body. [Claim 10] The load sensor device according to any one of claims 1 to 9, wherein the peripheral edge of the pressing member is fixed to the housing. [Claim 11] A load sensor device according to any one of claims 1 to 10, wherein, when viewed from the direction of load application, the rigid pressing portion overlaps entirely with the load receiving portion of the elastic body, and the pressure receiving portion overlaps entirely with the rigid pressing portion. [Claim 12] The aforementioned load sensor is A displacement part that is displaced by the load received by the pressure receiving part, A load sensor device according to any one of claims 1 to 11, comprising a plurality of piezoresistive elements for electrically detecting the amount of displacement of the displacement portion. [Claim 13] The load sensor device according to any one of claims 1 to 12, wherein the buffer portion is provided in contact with the elastic support portion. [Claim 14] The load sensor device according to claim 13, wherein the buffer portion includes a gel-like resin that adheres to the elastic support portion. [Claim 15] A load sensor device according to any one of claims 1 to 14, wherein a rigid plate portion is provided between the elastic body and the rigid pressing portion. [Claim 16] The load sensor device according to any one of claims 1 to 15, wherein the buffer portion has a portion made of a buffering fluid material within the housing.

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