JP6437267B2 - Load cell - Google Patents

Description

  The present invention relates to a parallelogram type load cell used in various weighing devices such as a platform scale, a weighing tank, and a weighing hopper, and more particularly to a waterproof type load cell.

  A strain gauge, which is a type of strain sensor that detects the amount of strain, is attached to the strain generating body, and the amount of expansion / contraction of the strained portion due to the load is converted into an electrical signal due to a change in the resistance value of the strain gauge. In a load cell that generates a load signal proportional to the size, a waterproof load cell disclosed in Patent Document 1, for example, is provided to protect the strain gauge portion and the like from the external environment.

  FIG. 6 is a front view of the load cell of Patent Document 1, and FIG. 7 is a cross-sectional view taken along the line AA in FIG.

  The load cell 50 includes a movable portion 51 to which a receiving base for receiving a load is attached, a fixed portion 52 to be attached to a base such as a base of a weighing device, and upper and lower beam portions 53 and 54 that connect them.

  Between the movable part 51 and the fixed part 52 on both sides in the left-right direction, a first through-hole 55 is formed that penetrates in the front-rear direction (perpendicular to the plane of FIG. A, up-down direction in FIG. B). In addition, the periphery of the first through-hole 55 is deeply dug to form a cylindrical portion 55a, and at the center portion in the front-rear direction, a part of the outer periphery thereof is connected to the movable portion 51 and the fixed portion via the connecting portion 56. 52, respectively.

  A pair of second upper through-holes 66 and 67 having a smaller diameter than the first through-hole 55 are formed on the upper beam portion 53 side around the first through-hole 55 and a connecting groove 68 that connects them. In addition, a pair of second lower through holes 69 and 70 having a smaller diameter than the first through hole 55 are formed on the lower beam portion 54 side around the first through hole 55, and A connecting groove 71 that connects them is formed.

  The pair of second upper through-holes 66 and 67 on the upper beam portion 53 side form thin strain-generating portions 53 a and 53 b in the upper beam portion 53, while connecting the outer periphery of the first through-hole 55. In the portion 56, thin strain generating portions 56a and 56b are formed. The pair of second lower through-holes 69 and 70 on the lower beam portion 54 side form thin strain-generating portions 54 a and 54 b in the lower beam portion 54, while the outer periphery of the first through-hole 55. Thin connection portions 56c and 56d are formed in the connecting portion 56.

  Four strain gauges 57-60 are attached to the inner peripheral surface of the first through-hole 55 corresponding to the strain-inducing portions 56a-56d on the outer periphery of the first through-hole 55, and these strains In order to waterproof the portions of the gauges 57 to 60, cylindrical metal cylindrical seal members 61 are fitted, both ends of the cylindrical seal members 61 and the first through-holes 55 are welded, and strain gauges 57 to 60 are obtained. The part is sealed.

  In addition, the fixing portion 52 is formed with a storage chamber 62 in which wiring for connecting the strain gauges 57 to 60 to the outside, a circuit board, and the like are stored. The first through-hole 55 is connected to the inner peripheral surface of the first through-hole 55 via a connection hole 64 formed in the connecting portion 56. The strain gauges 57 to 60 are connected to the outside via the connection hole 64, the storage chamber 62, and the communication hole 63. The storage chamber 62 is waterproofed by welding a metal lid 65 to the opening.

  In the load cell 50, when a load is applied to the movable portion 51, the strain generating portions 53a, 53b; 54a, 54b of the upper and lower beam portions 53, 54 are bent and the outer peripheral connecting portion of the first through hole 55 is connected. The strain generating portions 56a to 56d of the 56 are bent and the stretching strain stress is detected by the strain gauges 57 to 60 attached to the inner peripheral surface of the first through-hole 55 where the strain stress is concentrated, and the load load becomes the load signal. Converted.

U.S. Pat. No. 4,488,611

  In the load cell of Patent Document 1, the strain generating portions 53 a and 53 b of the upper and lower beam portions 53 and 54; 54 a and 54 b (hereinafter referred to as “first strain generating portion”) and the outer peripheral connection portion of the first through hole 55. There are 56 strain generating portions 56a to 56d (hereinafter referred to as "second strain generating portions"), and the first strain generating portion and the second strain generating portion constitute a parallel spring. Is the sum of the spring constants of the first and second strain generating portions.

  Thus, since the first strain generating portion exists and has a large spring constant, the second strain generating portion, that is, the springs of the strain generating portions 56 a to 56 d of the connecting portion 56 on the outer periphery of the first through-hole 55. The constant must be reduced.

  Therefore, as described above, the periphery of the first through-hole 55 is deeply dug with a wide width to form a thin cylindrical portion 55a, and the length of the cylindrical portion 55a in the front-rear direction (vertical direction in FIG. 7). In addition, there is a problem that processing is short and the processing cost is high.

  The present invention has been made paying attention to the above-described actual situation, and an object thereof is to provide a waterproof load cell with reduced cost.

  In order to achieve the above object, the present invention is configured as follows.

(1) The load cell of the present invention includes a fixed portion on one end side in the left-right direction and a movable portion on the other end side, an upper beam portion connecting the upper portion of the fixed portion and the upper portion of the movable portion, and a lower portion of the fixed portion. And a strain body made of a metal material integrally having a lower beam part connecting the lower part of the movable part, and having a through-hole penetrating in the front-rear direction between the fixed part and the movable part, On the upper end surface of the strain body, a pair of upper arc-shaped grooves having an arc cross section so as to penetrate in the front-rear direction are formed so as to be close to the outer periphery of the through hole, and the upper end surface of the strain body A pair of lower arc-shaped grooves having a circular arc cross section so as to penetrate in the front-rear direction on the lower end surface of the strain body so as to be close to the outer periphery of the through-hole. opening is provided between the lower end surface of the strain generating body is formed into the The partial arc-shaped groove is formed so that a part of the circumference corresponding to the arc of the upper arc-shaped groove remains, and the remaining part of the circumference longer than the part is positioned in the strain body. On the other hand, the lower arc-shaped groove leaves a part of the circumference corresponding to the arc of the lower arc-shaped groove, and the remaining part of the circumference longer than the part is positioned in the strain body. A strain gauge is attached to a portion of the inner peripheral surface of the through hole corresponding to the thin strain generating portion where each arc-shaped groove and the through hole are close to each other. An annular groove for forming a welding peripheral wall on the outer periphery of the through hole is formed on one end face so as to surround the through hole, while the other end face in the front-rear direction has the through hole on the other end face. An annular groove for forming a peripheral wall for welding is formed on the outer circumference of the through hole so as to surround the through hole. One end of a metal cylindrical seal member that is attached and seals the strain gauge and the peripheral wall for welding formed on the end surface on the one side are welded, while the other seal member An end part and the said surrounding wall for welding formed in the said end surface of the said other side are welded.

  According to the present invention, between the fixed part and the movable part, there is a through-hole penetrating in the front-rear direction, and the upper end surface of the strain generating body has a pair of upper circles having a circular arc shape so as to penetrate in the front-rear direction. While the arc-shaped grooves are formed so as to be close to the outer periphery of the through hole, a pair of lower arc-shaped grooves having a circular arc shape so as to penetrate in the front-rear direction are close to the through-hole on the lower end surface. Since the four arc-shaped grooves are formed, thin strain-generating portions are formed at four positions close to the through holes.

  The upper arc-shaped groove is formed in the upper end surface in a circular arc shape and opened upward, and similarly, the lower arc-shaped groove is formed in the lower end surface in a cross-sectional arc shape and opened downward.

  Therefore, as in Patent Document 1 of FIG. 6, the upper and lower beam portions as in the case where the second through-holes 66, 67; 69, 70 having a circular cross section are formed in the vicinity of the periphery of the first through-hole 55 are formed. The strain generating portions 53a and 53b; 54a and 54b of 53 and 54 do not exist.

  That is, the load cell of the present invention functions as a parallelogram load cell having four thin-walled portions each having four arcuate grooves close to the through-holes as strain-generating portions, and has a large spring constant as in Patent Document 1. As shown in Patent Document 1, in order to reduce the spring constant of the strain-generating portions 56a to 56d of the first through-hole 55, there is no first strain-circulating portion 53a, 53b; A waterproof load cell that reduces the processing cost is obtained by deeply digging the periphery of the hole 55 with a wide width to form a thin cylindrical portion 55a and reducing the longitudinal length of the cylindrical portion 55a. Can be obtained.

  Furthermore, a strain gauge is attached to the inner peripheral surface of the through hole corresponding to the four strain-generating portions, and a metal cylindrical seal member for sealing the strain gauge is attached and welded in the through hole. However, an annular groove is formed on each end surface on one side and the other side in the front-rear direction so as to surround the through-hole, thereby forming a peripheral wall for welding at the periphery of the through-hole, and one end of the cylindrical seal member. The part and the other end are welded to each welding peripheral wall formed on each end face.

  By forming an annular groove so that the size of the peripheral wall for welding corresponds to one end and the other end of the seal member that is the welding partner, heat from the welding peripheral wall and the seal is sealed. It can be transmitted evenly to the end of the member, and the strain gauge can be completely sealed and waterproofed without causing poor welding.

  Further, the annular groove is only for forming the peripheral wall for welding and may be formed thin and shallow, and the influence of the annular groove on the spring constant of the strain generating portion is extremely small and can be ignored. That is, processing for reducing the spring constant is not necessary, and the annular groove can be formed only by processing that considers welding.

(2) load cell Le of the present invention includes a movable portion of the stationary portion and the other end in the lateral direction of the one end side, and the upper beam portion for connecting the upper and upper portion of the movable portion of the fixed portion, the fixed portion A strain body made of a metal material integrally having a lower part and a lower beam part connecting the lower part of the movable part, and having a through-hole penetrating in the front-rear direction between the fixed part and the movable part The upper end surface of the strain body is formed with a pair of upper arc-shaped grooves having an arc cross section so as to penetrate in the front-rear direction so as to be close to the outer periphery of the through hole, and on the upper side of the strain body While an open portion is provided between the end surface and the lower end surface of the strain generating body, a pair of lower arc-shaped grooves having an arc cross section so as to penetrate in the front-rear direction are close to the outer periphery of the through-hole. And an open part is provided between the lower end surface of the strain generating body and the A strain gauge is attached to a portion of the inner peripheral surface of the through hole corresponding to the thin strained portion where each arc-shaped groove and the through hole are close to each other. An annular groove for forming a welding peripheral wall on the outer periphery of the hole is formed so as to surround the through hole, and a welding peripheral wall is formed on the outer periphery of the through hole on the other end surface in the front-rear direction. An annular groove is formed to surround the through hole, and is attached to the through hole and seals the strain gauge with one end of a metal cylindrical seal member, and the one end face The welding peripheral wall formed on the other side is welded, while the other end of the seal member and the welding peripheral wall formed on the other end surface are welded, and the penetration The hole is circular, and the upper arc-shaped groove and the lower arc-shaped groove are formed from the through-hole. It has a small-diameter cross-sectional arc shape, the seal member is cylindrical, and the annular groove has a narrow width less than the distance between the through-hole and the arc-shaped groove adjacent to the through-hole, and the through-hole And an arcuate groove adjacent to the through hole so as to surround the through hole.

According to the present invention , the through hole is circular, and processing is easier than in the case of an oval shape. Further, since the width of the annular groove is a narrow width less than the distance between the through hole and the arc-shaped groove adjacent to the through hole, the influence on the spring constant of the strain generating portion is extremely small. The annular groove is formed between the annular groove and the through hole because the annular groove is formed so as to surround the through hole through a region between the through hole and the arc-shaped groove adjacent to the through hole. The width of the peripheral wall for welding can be reduced.

  (3) In another embodiment of the load cell of the present invention, the one end portion and the other end portion of the cylindrical sealing member have a large diameter portion larger in diameter than the remaining portion, and the annular groove is The large-diameter portion is shallowly formed with a depth within the length along the front-rear direction.

  According to this embodiment, since the annular groove is formed shallow at a depth within the length along the front-rear direction of the large-diameter portion of the cylindrical seal member, the influence on the spring constant of the strain-generating portion is extremely small. Moreover, the height of the peripheral wall for welding formed between the annular groove and the through hole can be reduced.

  (4) In another embodiment of the load cell of the present invention, the large-diameter portion has a joint portion extending along the front-rear direction, and the welding peripheral wall and the joint portion are welded, The height is substantially equal to the length along the front-rear direction of the joint.

  According to this embodiment, the peripheral wall for welding at the periphery of the through hole having the strain gauge attached to the inner peripheral surface, and the seal member that is attached and welded to the inner periphery of the through hole to seal the strain gauge. Because the length of the weld is approximately equal, the heat during welding is evenly transferred to the peripheral wall for welding and the joint, so that welding can be reliably performed without causing poor welding, and the strain gauge is completely It can be sealed to be waterproof.

  (5) In the embodiment of the above (4), the width of the peripheral wall for welding may be substantially equal to the width of the joint portion.

  According to this embodiment, the peripheral wall for welding at the periphery of the through hole having a strain gauge attached to the inner peripheral surface, and the joint portion of the seal member that is mounted and welded in the through hole to seal the strain gauge, Since the lengths and widths of these are made substantially equal, the heat of welding is transmitted more evenly, and more reliable welding is possible.

  (6) In a preferred embodiment of the present invention, the seal member is made of the same type of metal material as the strain body.

  According to this embodiment, since the strain body constituting the welding peripheral wall and the seal member which is the welding counterpart are made of the same type of metal material, the mechanical properties of different materials are different as in the case of welding different materials. The characteristics of the load cell are not deteriorated due to the difference in properties.

  As described above, according to the load cell of the present invention, the four arc-shaped grooves have four thin-walled portions close to the through-holes as the strain-generating portions, and are large other than the periphery of the through-holes as in the conventional patent document 1. Since there is no strain-generating portion having a spring constant, as in Patent Document 1, in order to reduce the spring constant of the strain-generating portion around the through-hole, the periphery of the through-hole is deeply dug into a wide width and thin. It is not necessary to form a cylindrical part and to shorten the length of the cylindrical part in the front-rear direction, and it is only necessary to apply a shallow and narrow simple process to enable normal welding, thus reducing costs. A waterproof load cell can be obtained.

  Furthermore, the welding peripheral wall on the outer periphery of the through hole is formed in a size corresponding to the end of the cylindrical seal member for sealing the strain gauge, so that the heat during welding is sealed with the peripheral wall for welding. It can be transmitted evenly to the end of the member, and welding can be reliably performed without causing poor welding, whereby the strain gauge can be completely sealed and waterproofed.

FIG. 1 is a front view of a load cell according to an embodiment of the present invention. FIG. 2 is a plan view of the load cell of FIG. 3 is an enlarged cross-sectional view taken along the line BB in FIG. 4 is an enlarged cross-sectional view taken along the line CC in FIG. FIG. 5 is a front view of a load cell according to another embodiment of the present invention. FIG. 6 is a front view of a conventional example. 7 is a cross-sectional view taken along the line AA in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a front view of a load cell according to an embodiment of the present invention, and FIG. 2 is a plan view thereof.

  The load cell 1 of this embodiment includes a strain generating body 2 made of a stainless steel, or a rectangular metal elastic body such as aluminum or iron. The load cell 1 is formed between a fixed portion 3 on one end side in the left-right direction (the left-right direction in FIGS. 1 and 2) which is a horizontal direction, a movable portion 4 on the other end side, and both the portions 3 and 4. A circular through-hole 5 having a diameter R that penetrates in the thickness direction of the strain body 2 (perpendicular to the plane of FIG. 1, the vertical direction in FIG. 2) and the upper end surface of the strain body 2 are formed. A pair of upper arc-shaped grooves 6 and 7 having an arc shape extending so as to penetrate in the front-rear direction, and a lower circle having a cross-section arc shape extending in the front-rear direction formed in the lower end surface of the strain body 2 Arc-shaped grooves 8 and 9, a wiring connection chamber 10 formed on the fixed portion 3 side for connecting and storing wiring, a lid 11 for sealing the opening, and the like are provided.

  The load cell 1 of this embodiment is a waterproof type, and is an enlarged cross-sectional view described later in order to seal the strain gauges 12a to 12d attached to four locations on the inner peripheral surface of the through-hole 5 as shown in FIG. As shown in FIG. 4, a cylindrical metal cylindrical seal member 13 is fitted into the through-hole 5 and is sealed by welding.

  As shown in FIG. 1, a screw hole 14 for fixing the load cell 1 to a base such as a base 26 of the weighing device is formed on the lower surface side of the fixed portion 3. On the end face, there is formed a screw hole 16 for attaching a weighing table fitting 15a for supporting the weighing table 15 on which an object to be weighed is placed.

  The pair of upper arcuate grooves 6 and 7 are close to the through-hole 5 so as to penetrate in the front-rear direction, that is, from one end face (front face) to the other end face (back face) in the front-rear direction. Formed. An open portion is provided between the upper end surface of the strain body 2.

  Similarly, the pair of lower arc-shaped grooves 8 and 9 penetrates in the front-rear direction, that is, extends from one end surface (front surface) to the other end surface (rear surface) in the front-rear direction. 5 is formed in the vicinity. An open portion is provided between the lower end surface of the strain generating body 2.

  The arc diameters r of the arc-shaped grooves 6 to 9 are equal to each other and smaller than the diameter R of the through-hole 5. Each of the arc-shaped grooves 6 to 9 is formed in parallel to the through-hole 5 along the front-rear direction. In the case of the load cell 1 of FIG. 1, the open portion refers to a portion where a part of the circumference of the arc-shaped grooves 6, 7, 8, 9 is interrupted by the upper surface and the lower surface of the strain body 2.

  The movable part 4 and the fixed part 3 have a pair of upper beam portions 17 between a pair of upper arcuate grooves 6 and 7 on the upper side of the through-hole 5 and a pair of lower sides of the through-hole 5. The lower arcuate grooves 8 and 9 are connected to each other via a lower beam portion 18. The upper arc-shaped grooves 6 and 7 are formed at symmetrical positions with the upper beam portion 17 in between, and the lower arc-shaped grooves 8 and 9 are formed at symmetrical positions with the lower beam portion 18 in between.

  The upper arc-shaped grooves 6 and 7 and the through-hole 5 form thin strain-generating portions 19a and 19b in the upper beam portion 17, while the lower arc-shaped grooves 8 and 9 and the through-hole 5 The beam portion 18 is formed with thin strain-generating portions 19c and 19d.

  The distances a from the through-hole 5 to the upper and lower arc-shaped grooves 6, 7; 8, 9 are all equal, and are the thicknesses of the strain-generating portions 19 a to 19 d. Strain gauges 12 a to 12 d are attached to the inner peripheral surface of the through-hole 5 corresponding to the strain generating portions 19 a to 19 d that generate strain corresponding to the load, at the center portion in the front-rear direction. The diameter R of the through-hole 5 is a size necessary for attaching the strain gauges 12a to 12d and performing wiring work.

  When a load is applied from the weighing table 15 to the movable portion 4, the four thin portions formed between the four arc-shaped grooves 6-9 and the through-hole 5 are referred to as strain-generating portions 19a-19d. As a parallelogram type load cell, the connecting portion between the upper upper arc-shaped grooves 6 and 7 is the upper beam portion 17 and the connecting portion between the lower lower arc-shaped grooves 8 and 9 is the lower beam portion 18. Function.

  That is, when a load is applied to the load cell 1 via the weighing table 15 to the movable portion 4, the strain-generating portions 19 a to 19 d on the outer periphery of the through-hole 5 are bent, and a strain gauge on the inner peripheral surface of the through-hole 5 is deformed. The stretching strain stress is detected by 12a to 12d, the load load is converted into a load signal, and the load load applied to the weighing table 15 is calculated by calculating the load signal.

  3 is an enlarged sectional view taken along the line BB in FIG. 1, and FIG. 4 is an enlarged sectional view taken along the line CC in FIG.

  In the load cell 1 of this embodiment, a cylindrical seal member 13 having a cylindrical shape is fitted into the through-hole 5 in order to completely seal the strain gauges 12 a to 12 d attached to the inner peripheral surface of the through-hole 5. , TIG welding and laser welding.

  The cylindrical seal member 13 is made of metal, and both end portions thereof are slightly large-diameter flange portions 13a. The flange portion 13a includes an inclined portion 13a1 inclined outward and a joint portion extending in the front-rear direction. 13a2.

  In this welding, the through-hole 5 and the joint portion 13a2 of the cylindrical seal member 13 are melted and joined. In order to make the heat transfer characteristics and heat capacity of the joined portions substantially equal, the following configuration is adopted. Yes.

  That is, the peripheral wall 21 for welding is formed in the periphery of the through-hole 5 so that it may become a magnitude | size substantially equal to the junction part 13a2 of the cylindrical seal member 13 in the front-back direction (up-down direction of FIG. 3, FIG. 4). Is done.

  In order to form the peripheral wall 21 for welding, as shown in FIG. 1, an annular groove 20 passing through a region between the through-hole 5 and the respective arc-shaped grooves 6 to 9 adjacent to the through-hole 5 is formed. Forming.

  The annular groove 20 of this embodiment has a rectangular cross section, and its width W is a narrow width less than the distance a between the through-hole 5 and each of the arc-shaped grooves 6 to 9 adjacent to the through-hole 5. It is. As shown in FIG. 3, the depth D of the annular groove 20 is shallower than a length L <b> 1 along the front-rear direction of the large-diameter flange portion 13 a of the cylindrical seal member 13. In other words, the welding peripheral wall 21 may have a low height because the extremely short portion of the tip where the peripheral wall 21 for welding and the cylindrical seal member 13 are contacted with each other is melted by small amounts.

  Therefore, the welding peripheral wall 21 formed between the through-hole 5 and the annular groove 20 is thin and low. In this embodiment, the width and height of the welding peripheral wall 21 are the same as those of the cylindrical seal member 13. It is formed to be approximately equal to the thickness and length of the joint portion 13a2.

  Thereby, the heat transfer characteristic and heat capacity of the peripheral wall 21 for welding of the periphery of the through-hole 5 and the joint part 13a2 of the cylindrical seal member 13 can be made substantially equal, and the heat at the time of TIG (TIG) welding is The welding peripheral wall 21 and the joint portion 13a2 are transmitted substantially evenly, and the welding peripheral wall 21 and the joint portion 13a2 can be melted and joined to each other evenly.

  Accordingly, there is no occurrence of imbalance in heat conduction, and either one of them quickly melts and welding failure does not occur, and the welding peripheral wall 21 and the cylindrical seal member 13 can be reliably joined.

  By joining the peripheral wall 21 for welding and the cylindrical seal member 13, an airtight chamber 22 is formed in which the inner peripheral surface of the through-hole 5 to which the strain gauges 12 a to 12 d are attached is completely sealed by the cylindrical seal member 13. The

  Furthermore, in this embodiment, the cylindrical seal member 13 is made of the same type of metal material as that of the strain body 2 constituting the peripheral wall 21 for welding at the periphery of the through-hole 5.

  In this way, the joining portion 13a2 of the cylindrical seal member 13 made of the same type of metal material and the welding peripheral wall 21 at the periphery of the through-hole 5 are melted and welded to each other so that different materials are used. In addition, the characteristics of the load cell are not deteriorated due to differences in mechanical properties of different materials. Moreover, since it has the same thermal conductivity, it melts at the same timing, which is convenient.

  As described above, since the strain gauges 12 a to 12 d on the inner peripheral surface of the through-hole 5 are present in the airtight chamber 22, they have waterproof performance. Further, the load signal detection wiring also has waterproof performance, and therefore, as shown in FIGS. 1 and 2, the inner peripheral surface of the through-hole 5 and the wiring connection chamber 10 are connected inside the fixed portion 3. While the wiring hole 23 is formed, a connection hole 24 for connecting the wiring connection chamber 10 and the outside is formed at the end of the fixed portion 3. The wiring drawn out from the hermetic chamber 22 is connected to the wiring introduced from the outside of the load cell 1 through the waterproof connector 25 in the wiring connection chamber 10. The circular opening is covered with a thin metal lid 11 with a flange on the outer periphery so that the wiring connection chamber 10 also has waterproof performance, and the periphery of the opening and the flange of the lid 11 are covered. The wiring connection chamber 10 is joined by TIG welding or the like and is completely sealed and has high waterproof performance.

  As described above, according to the present embodiment, the four thin-walled portions where the four arc-shaped grooves 6 to 9 are respectively close to the through-hole 5 are the strain-generating portions 19a to 19d, and the upper arc-shaped grooves 6 and 7 are used. Since the upper side of the lower arc-shaped grooves 8 and 9 are open, the strain generating portions 53a and 53b; 54a and 54b having a large spring constant as in the conventional patent document 1 of FIG. There is no need to make the strain generating portions 19a to 19d thin in the front-rear direction, that is, in order to reduce the spring constant of the strain generating portions 56a to 56d of the first through-hole 55 as in Patent Document 1. In addition, the periphery of the first through-hole 55 is deeply dug with a wide width to form a thin cylindrical portion 55a, and it is not necessary to shorten the length in the front-rear direction of the cylindrical portion 55a, thereby reducing the processing cost. A waterproof load cell 1 can be obtained.

  Furthermore, a cylindrical seal member 13 for sealing the strain gauges 12a to 12d on the inner peripheral surface of the through-hole 5 is fitted into the through-hole 5 and welded. By forming the annular groove 20 so as to surround the hole 5, a welding peripheral wall 21 having a size substantially equal to the joint portion 13 a 2 of the cylindrical seal member 13 is formed on the periphery of the through-hole 5. And the joint portion 13a2 of the cylindrical seal member 13 are welded, so that heat during welding can be evenly transmitted to the peripheral wall 21 for welding and the joint portion 13a2 of the cylindrical seal member 13, resulting in poor welding. Without generating, reliable welding becomes possible, and the strain gauges 12a to 12d can be completely sealed to achieve airtightness and waterproofing.

  Further, the annular groove 20 is only for forming the peripheral wall 21 for welding, and may be processed thinly and shallowly. The processing is easy and the influence on the spring constant of the strain generating portions 19a to 19d is extremely high. Small and can be ignored. In other words, the spring constants of the strain generating portions 19a to 19d may be determined depending on the thickness between the through-hole 5 and the arc-shaped grooves 6 to 9.

  In the load cell 1 of the present embodiment, even if the rated capacity is small, it is not necessary to reduce the thickness in the front-rear direction of the strain-generating portions 19a to 19d around the through-hole 5 as in the case of Patent Document 1, That is, it is not necessary to dig deeply around the through-hole 5, and the annular groove 20 may be shallow and narrow as a dedicated groove for forming the peripheral wall 21 for welding.

  FIG. 5 is a front view of a load cell according to another embodiment of the present invention, and portions corresponding to the above-described embodiment are denoted by the same reference numerals.

  In the load cell 1a of this embodiment, in order to increase the response speed, that is, to increase the natural frequency, the angle α formed by each neutral line of the strain generating portions 19a to 19d with the horizontal line is less than 30 degrees (α <30 °). In FIG. 5, the angle α is shown only for the strain generating portions 19a and 19b, but the same applies to the strain generating portions 19c and 19d.

  In this way, the distance L2 between the strain-generating portions 19b, 19d on the fixed portion 3 side called the moment arm and the strain-generating portions 19a, 19c on the movable portion 4 side can be shortened. The amount of bending of the strained portions 19a to 19d is reduced, that is, the spring constant is increased, the natural frequency of the load cell 1a is increased, and high-speed response is possible.

  Other configurations are the same as those in the above embodiment.

  In each of the above embodiments, the width W of the annular groove 20 is less than the distance a between the through-hole 5 and each of the arc-shaped grooves 6 to 9 adjacent to the through-hole 5, but the distance a is equal to or greater than the distance a. It is good.

  Further, the depth D of the annular groove 20 is not more than the length L1 along the front-rear direction of the large-diameter flange portion 13a of the cylindrical seal member 13, but may be a depth exceeding the length L1.

The cross-sectional shape of the annular groove 20 is not limited to a rectangle, but may be a V shape or other shapes.
Although the through-hole 5 is circular, it may be oval. In this case, an oval cylindrical seal member may be used.

DESCRIPTION OF SYMBOLS 1,1a Load cell 2 Strain body 3 Fixed part 4 Movable part 5 Through-circular hole 6,7 Upper circular arc groove 8,9 Lower circular arc groove 9,10 Lower through-circular hole 12a-12d Strain gauge 13 Cylindrical seal member 13a Flange Part (large diameter part)
13a2 Joint portion 17 Upper beam portion 18 Lower beam portion 19a to 19d Strain portion 20 Annular groove 21 Welding peripheral wall

Claims (6)

A fixed portion on one end side in the left-right direction and a movable portion on the other end side, an upper beam portion connecting the upper portion of the fixed portion and the upper portion of the movable portion, a lower portion of the fixed portion, and a lower portion of the movable portion are connected. Comprising a strain body made of a metal material integrally having a lower beam portion;
Between the fixed part and the movable part, there is a through-hole penetrating in the front-rear direction,
On the upper end surface of the strain body, a pair of upper arc-shaped grooves having an arc cross section so as to penetrate in the front-rear direction are formed so as to be close to the outer periphery of the through hole, and the upper end surface of the strain body A pair of lower arc-shaped grooves having a circular arc cross section so as to penetrate in the front-rear direction on the lower end surface of the strain body so as to be close to the outer periphery of the through-hole. And an open portion is provided between the lower end surface of the strain generating body and
The upper arc-shaped groove is formed so that a part of the circumference corresponding to the arc of the upper arc-shaped groove remains, and the remaining part of the circumference longer than the part is positioned in the strain body. On the other hand, the lower arcuate groove leaves a part of the circumference corresponding to the arc of the lower arcuate groove, and the remaining part of the circumference longer than the part is in the strain body. Formed to be located,
A strain gauge is attached to a portion of the inner peripheral surface of the through hole corresponding to the thin strain generating portion where each arc-shaped groove and the through hole are close to each other,
On one end surface in the front-rear direction, an annular groove for forming a welding peripheral wall on the outer periphery of the through-hole is formed so as to surround the through-hole, while on the other end surface in the front-rear direction, An annular groove for forming a peripheral wall for welding on the outer periphery of the through hole is formed so as to surround the through hole,
One end of a metal cylindrical sealing member that is mounted in the through hole and seals the strain gauge, and the welding peripheral wall formed on the one end surface are welded, The other end of the seal member and the peripheral wall for welding formed on the end surface on the other side are welded.
A load cell characterized by that. A fixed portion on one end side in the left-right direction and a movable portion on the other end side, an upper beam portion connecting the upper portion of the fixed portion and the upper portion of the movable portion, a lower portion of the fixed portion, and a lower portion of the movable portion are connected. Comprising a strain body made of a metal material integrally having a lower beam portion;
Between the fixed part and the movable part, there is a through-hole penetrating in the front-rear direction,
On the upper end surface of the strain body, a pair of upper arc-shaped grooves having an arc cross section so as to penetrate in the front-rear direction are formed so as to be close to the outer periphery of the through hole, and the upper end surface of the strain body A pair of lower arc-shaped grooves having a circular arc cross section so as to penetrate in the front-rear direction on the lower end surface of the strain body so as to be close to the outer periphery of the through-hole. And an open portion is provided between the lower end surface of the strain generating body and
A strain gauge is attached to a portion of the inner peripheral surface of the through hole corresponding to the thin strain generating portion where each arc-shaped groove and the through hole are close to each other,
On one end surface in the front-rear direction, an annular groove for forming a welding peripheral wall on the outer periphery of the through-hole is formed so as to surround the through-hole, while on the other end surface in the front-rear direction, An annular groove for forming a peripheral wall for welding on the outer periphery of the through hole is formed so as to surround the through hole,
One end of a metal cylindrical sealing member that is mounted in the through hole and seals the strain gauge, and the welding peripheral wall formed on the one end surface are welded, The other end of the seal member and the peripheral wall for welding formed on the other end surface are welded.
The through hole is circular;
The upper arc-shaped groove and the lower arc-shaped groove have a cross-sectional arc shape having a smaller diameter than the through hole,
The sealing member is cylindrical;
The annular groove has a narrow width less than the distance between the through-hole and the arc-shaped groove adjacent to the through-hole, and passes through a region between the through-hole and the arc-shaped groove adjacent to the through-hole. Formed to surround the through hole,
A load cell characterized by that . The one end part and the other end part of the cylindrical sealing member have a large diameter part larger in diameter than the remaining part,
The annular groove is formed shallow with a depth within a length along the front-rear direction of the large diameter portion.
The load cell according to claim 1 or 2. The large-diameter portion has a joint portion extending along the front-rear direction,
The peripheral wall for welding and the joint are welded,
The height of the peripheral wall for welding is substantially equal to the length along the front-rear direction of the joint,
The load cell according to claim 3. The width of the peripheral wall for welding is substantially equal to the width of the joint portion.
The load cell according to claim 4. The seal member is made of the same type of metal material as the strain body,
The load cell according to any one of claims 1 to 5.

Images