JP3853157B2

JP3853157B2 - Load sensor

Info

Publication number: JP3853157B2
Application number: JP2001001676A
Authority: JP
Inventors: 良一前田; 昭人三浦; 幸一高橋
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 2001-01-09
Filing date: 2001-01-09
Publication date: 2006-12-06
Anticipated expiration: 2021-01-09
Also published as: JP2002206974A

Description

【０００１】
【発明の属する技術分野】
本発明は、受圧部の荷重点に加わる荷重を歪検出素子を設けた起歪部の撓み具合によって検出する荷重センサに係り、特に、歪検出素子が起歪部に印刷形成される荷重センサに関する。
【０００２】
【従来の技術】
図１１はこの種の荷重センサの従来技術を示す平面図、図１２は図１１のＡ−Ａ線に沿う断面図である。これらの図において、符号１は荷重センサのベース体を総括的に示している。このベース体１は１枚の金属板を加工したもので、固定端側の取付部２と、この取付部２から隣接する開口３の両側縁に沿って延びる一対の起歪部４と、これら両起歪部４の自由端側を連結している連結部５と、この連結部５から開口３内へ舌状に突出している受圧部６とからなる。
【０００３】
ベース体１の片面は平坦な印刷面となっており、この印刷面上に、図示せぬ絶縁コート層と配線パターンとが印刷形成されている。また、各起歪部４は取付部２に近い部位４ａと連結部５に近い部位４ｂにおいて板厚が薄く形成されており、この肉薄な部位４ａ，４ｂ上の前記絶縁コート層上にはそれぞれ、厚膜抵抗体からなる歪検出素子７，８が印刷形成されている。なお、計４か所に配設されている歪検出素子７，８は、前記配線パターンにより結線されてホイートストンブリッジ回路を構成している。取付部２には一対の軸孔２ａが穿設されていて、各軸孔２ａにはボルト９が挿通されており、このボルト９の頭部で軸孔２ａの周縁部を加圧することによって、取付部２は外部の支持部材１０上に固定されている。舌状の受圧部６の先端部には荷重点６ａが設けられており、この荷重点６ａに外部から荷重が印加されると、各起歪部４の肉薄な部位４ａ，４ｂに逆向きの曲げモーメントが発生して、各起歪部４は緩やかなＳ字形状に撓む。つまり、荷重点６ａに上から荷重が加わると、起歪部４のうち取付部２に近い肉薄な部位４ａは上に凸な形状に撓むが、連結部５に近い肉薄な部位４ｂは下に凸な形状に撓むので、部位４ａ上の歪検出素子７は引っ張り応力を検出し、部位４ｂ上の歪検出素子８は圧縮応力を検出する。このように起歪部４に発生する歪を歪検出素子７，８によって検出すれば、その歪の大きさから、荷重点６ａに作用している荷重を求めることができる。
【０００４】
なお、歪検出素子を搭載した片持ち梁状の板状部材の先端部に荷重を加えるように構成した荷重センサも知られているが、このものは逆向きの曲げモーメントを発生する複数の場所で応力を検出することができないので、上述した構成のものに比べて精度の向上が図りにくいという難点がある。
【０００５】
【発明が解決しようとする課題】
図１１，１２に示すような従来の荷重センサは、ベース体１の平坦な印刷面に配線パターンや歪検出素子７，８等を印刷形成して製造するというものなので、量産しやすく低コスト化に好適である。しかしながら、ベース体１の印刷面側を受圧部６も含めてすべて同一平面内に位置させる設計になっているため、配線パターン等を印刷形成する際の加熱工程で舌状の受圧部６に反りが生じ、荷重点６ａを有する受圧部６の先端部が該印刷面よりも上に位置してしまうことがあった。その場合、受圧部６の先端部に干渉されて歪検出素子７，８の印刷が円滑に行えなくなるので、センシング精度が損なわれる恐れがあり、製造歩留まりも低下しやすくなる。
【０００６】
本発明は、このような従来技術の実情に鑑みてなされたもので、その目的は、受圧部の反りに起因する歪検出素子の印刷不良が回避でき、品質の安定化や製造歩留まりの向上に好適な荷重センサを提供することにある。
【０００７】
【課題を解決するための手段】
上述した目的を達成する解決手段として、本発明は、外部機器に固定される一端側の取付部と、この取付部に隣接する開口と、前記取付部から前記開口の側縁に沿って他端側へ延び、少なくとも片面を平坦な印刷面となした起歪部と、前記他端側で前記起歪部に連結されて前記開口内へ舌状に突出する受圧部と、前記起歪部の前記印刷面に印刷形成され、前記受圧部に印加される荷重に応じて生じる該起歪部の歪を検出する歪検出素子とを備え、前記受圧部に荷重が印加されていない状態で、該受圧部の先端部が前記印刷面を含む平面よりも板厚方向下側に位置するように構成した。
【０００８】
このように、荷重点を有する受圧部の先端部を予め起歪部の印刷面を含む平面よりも板厚方向下側に位置させておけば、製造時の加熱工程で受圧部に反りが生じた場合にも、受圧部が起歪部の印刷面よりも上に位置してしまう心配がなくなるので、受圧部の反りに起因する歪検出素子の印刷不良が回避できる。
【０００９】
なお、起歪部の印刷面を含む平面に対して受圧部の先端部を予め下げておくためには、例えば、受圧部の先端側の板厚を基端側の板厚よりも薄く形成したり、あるいは、板厚が均一な受圧部をその先端側が印刷面を含む平面から漸次離反するように折曲させておけばよい。
【００１０】
【発明の実施の形態】
以下、発明の実施の形態について図面を参照して説明すると、図１は第１の実施形態例に係る荷重センサの側面図、図２は図１に示す荷重センサの平面図、図３は図１，２に示す荷重センサの製造時の印刷工程図、図４は図１〜図３に示す受圧部の変形例を示す断面図、図５は第２の実施形態例に係る荷重センサの斜視図、図６は図５に示す荷重センサの要部平面図、図７は図６のＣ−Ｃ線に沿う断面図、図８は第３の実施形態例に係る荷重センサの斜視図、図９は図８に示す荷重センサの受圧部の断面図、図１０は図８，９に示す受圧部の変形例を示す断面図である。なお、これらの図において、従来技術の説明に用いた図１１，１２と対応する部分には同一符号を付してある。
【００１１】
まず、図１〜図３を参照しつつ第１の実施形態例について説明すると、図中の符号１は荷重センサのベース体、１１はベース体１上に印刷形成された絶縁コート層、１２は絶縁コート層１１上に印刷形成された配線パターンを示している。ベース体１はＳＵＳ等の１枚の金属板を加工したもので、固定端側の取付部２と、この取付部２から隣接する開口３の両側縁に沿って延びる一対の起歪部４と、これら両起歪部４の自由端側を連結している連結部５と、この連結部５から開口３内へ舌状に突出している受圧部６とからなり、受圧部６の先端部は測定対象物の荷重が印加される荷重点６ａとなっている。図１に示すように、この受圧部６は荷重点６ａが設けられた面を傾斜面とすることにより、その先端側が漸次肉薄になるように形成されており、したがって、荷重が印加されていない無負荷状態で受圧部６の先端部は開口３内に没入した位置に配置されることとなる。また、ベース体１のうち、各起歪部４は他の部分よりも板厚が薄く形成され、撓みやすくなっている。
【００１２】
図３（ａ）に示すように、このベース体１の片面（図１の上面）には絶縁コート層１１が印刷形成されており、図３（ｂ）に示すように、この絶縁コート層１１上には配線パターン１２が印刷形成されている。さらに、図３（ｃ）に示すように、各起歪部４上の所定位置には厚膜抵抗体からなる歪検出素子７，８が印刷形成されている。そして、計４か所に形成されている歪検出素子７，８が、配線パターン１２により結線されてホイートストンブリッジ回路を構成している。また、取付部２には軸孔２ａ（図３参照）が穿設されており、この軸孔２ａに挿通したボルト９が外部の支持部材１０のねじ孔に強い締結力で螺着させてある。つまり、ボルト９の頭部で軸孔２ａの周縁部を加圧することにより、取付部２が外部の支持部材１０上に固定されている。ただし、軸孔２ａの中心Ｐと開口３内とを通過する直線群が図２中の角度θの範囲内に限定されることを考慮して、この範囲内に歪検出素子７，８を印刷形成し、ボルト９を強く締め付けても歪検出素子７，８の特性に悪影響が及ばないようにしてある。
【００１３】
この荷重センサは、受圧部６の先端部の荷重点６ａに荷重が印加されると、肉薄な各起歪部４が撓む。このとき、各起歪部４は緩やかなＳ字形状に撓んで、取付部２の近傍と連結部５の近傍とが逆向きの曲げモーメントを発生するので、取付部２の近傍の歪検出素子７は引っ張り応力を検出し、連結部５の近傍の歪検出素子８は圧縮応力を検出する。したがって、これら歪検出素子７，８により検出した歪の大きさから、荷重点６ａに作用している荷重を高精度に求めることができる。しかも、この荷重センサの場合、荷重点６ａから歪検出素子７までの距離と歪検出素子８までの距離とが略同等に設定してあるので、歪検出素子７の検出する引っ張り応力の値と歪検出素子８の検出する圧縮応力の値とが略同等になる。それゆえ、歪検出素子７，８を含むホイートストンブリッジ回路は簡素な構成となっている。
【００１４】
上述したように、本実施形態例においては、荷重点６ａを有する受圧部６の先端部を予め開口３内に没入させてあるので、絶縁コート層１１や配線パターン１２を印刷形成する際の加熱工程で舌状の受圧部６に反りが生じた場合にも、受圧部６の先端部が起歪部４の印刷面を含む平面Ｂ（図１参照）よりも上に位置してしまうことはなく、それゆえ、受圧部６の反りに起因する歪検出素子７，８の印刷不良が発生する心配はない。すなわち、歪検出素子７，８は受圧部６に干渉されることなく常に円滑に印刷することができ、製造歩留まりが向上し、歪検出素子７，８のセンシング精度が損なわれる心配もない。また、本実施形態例では、各起歪部４上に印刷形成された歪検出素子７，８と取付部２の軸孔２ａの中心Ｐとの間に開口３の一部が介在するように設計してあるので、軸孔２ａの周縁部を加圧するボルト９の強い締め付け力に起因するゆがみが、開口３に遮られて歪検出素子７，８には直接影響しないように配慮されている。その結果、歪検出素子７，８の特性が製品ごとにばらつかず、信頼性の高い荷重センサとなっている。
【００１５】
なお、本実施形態例では受圧部６の板厚を先端側が漸次肉薄となるように形成しているが、図４に示すように、板厚が一様な受圧部６を起歪部４の印刷面を含む平面Ｂから漸次離反するように折曲させることにより、受圧部６の先端部を予め該平面Ｂよりも下に位置させておく構成としてもよい。
【００１６】
また、本実施形態例では、ベース体１が金属板からなる場合について説明しているが、ベース体１が絶縁基板であってもよく、その場合、ベース体１上に絶縁コート層１１を形成する必要はなくなる。
【００１７】
次に、図５〜図７に示す第２の実施形態例について説明すると、これらの図に示す荷重センサでは、舌状の受圧部６の表裏両面を傾斜面となし、板厚がくさび状に先細りの受圧部６を開口３内に突出させている。したがって、この受圧部６の先端部も第１の実施形態例と同様に、荷重が印加されていない無負荷状態で開口３内に没入した位置に配置されることになり、製造時の加熱工程で受圧部６に反りが生じたとしても、受圧部６の先端部が、起歪部４の印刷面よりも上に位置して歪検出素子７，８の印刷に支障をきたす恐れはない。
【００１８】
なお、この第２の実施形態例では、ベース体１の形状が第１の実施形態例と若干異なっている。すなわち、図５，６に示すベース体１では、各起歪部４が長手方向中間部でくびれた形状にしてある。このような形状にすると、荷重が印加されたときに各起歪部４が大きく撓んで、歪検出素子７，８が大きな歪を検出することになるので、検出精度を一層向上させることができる。
【００１９】
次に、図８，９に示す第３の実施形態例について説明する。これらの図に示す荷重センサでは、舌状の受圧部６の板厚が基端側（連結部５側）のみで厚く、他はすべて肉薄に形成されている。したがって、この受圧部６も第１および第２の実施形態例と同様に、荷重が印加されていない無負荷状態で、受圧部６の先端部が開口３内に没入した位置に配置されることになり、受圧部６の反りに起因する歪検出素子７，８の印刷不良が回避できる。
【００２０】
また、図１０に示す変形例のように、受圧部６の先端部の表裏両面に板厚方向へ突出する突起６ｂ，６ｃを設け、これらの突起６ｂ，６ｃの頂部を荷重点６ａとなしておけば、表裏いずれの側にある測定対象物にも対応させることができるので、荷重センサの使い勝手が向上すると共に、測定対象物と荷重センサとの相対位置が板面方向に多少ずれても、測定対象物の荷重を確実に荷重点６ａに加えることができるので、荷重センサの取付位置に若干の誤差があっても動作不良が回避しやすくなる。
【００２１】
【発明の効果】
本発明は、以上説明したような形態で実施され、以下に記載されるような効果を奏する。
【００２２】
荷重点を有する受圧部の先端部を予め起歪部の印刷面を含む平面よりも板厚方向下側に位置させたため、製造時の加熱工程で受圧部に反りが生じた場合にも、受圧部の先端部が起歪部の印刷面よりも上に位置してしまうことはなく、それゆえ受圧部の反りに起因する歪検出素子の印刷不良が回避でき、品質の安定化や製造歩留まりの向上が図れる荷重センサを提供できる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態例に係る荷重センサの側面図である。
【図２】図１に示す荷重センサの平面図である。
【図３】図１，２に示す荷重センサの製造時の印刷工程図である。
【図４】図１〜図３に示す受圧部の変形例を示す断面図である。
【図５】本発明の第２の実施形態例に係る荷重センサの斜視図である。
【図６】図５に示す荷重センサの要部平面図である。
【図７】図６のＣ−Ｃ線に沿う断面図である。
【図８】本発明の第３の実施形態例に係る荷重センサの斜視図である。
【図９】図８に示す荷重センサの受圧部の断面図である。
【図１０】図８，９に示す受圧部の変形例を示す断面図である。
【図１１】従来例に係る荷重センサの平面図である。
【図１２】図１１のＡ−Ａ線に沿う断面図である。
【符号の説明】
１ベース体
２取付部
２ａ軸孔
３開口
４起歪部
５連結部
６受圧部
６ａ荷重点
７，８歪検出素子
９ボルト
１０支持部材
１１絶縁コート層
１２配線パターン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a load sensor that detects a load applied to a load point of a pressure receiving portion by a bending state of a strain generating portion provided with a strain detecting element, and particularly relates to a load sensor in which the strain detecting element is printed and formed on the strain generating portion. .
[0002]
[Prior art]
FIG. 11 is a plan view showing the prior art of this type of load sensor, and FIG. 12 is a sectional view taken along the line AA of FIG. In these drawings, reference numeral 1 generally indicates a base body of the load sensor. The base body 1 is formed by processing a single metal plate, and includes a mounting end 2 on a fixed end side, a pair of strain-generating portions 4 extending from both sides of the opening 3 adjacent to the mounting portion 2, and these It comprises a connecting part 5 that connects the free ends of both strain-generating parts 4 and a pressure receiving part 6 that projects from the connecting part 5 into the opening 3 in a tongue shape.
[0003]
One surface of the base body 1 is a flat printing surface, and an insulating coat layer and a wiring pattern (not shown) are printed on the printing surface. In addition, each strain generating portion 4 is formed thin in a portion 4a close to the attachment portion 2 and a portion 4b close to the connecting portion 5, and on the insulating coat layer on the thin portions 4a and 4b, respectively. The strain detection elements 7 and 8 made of thick film resistors are printed. The strain detection elements 7 and 8 arranged in a total of four locations are connected by the wiring pattern to constitute a Wheatstone bridge circuit. A pair of shaft holes 2a are formed in the mounting portion 2, and bolts 9 are inserted into the respective shaft holes 2a. By pressurizing the peripheral portion of the shaft hole 2a with the head of the bolt 9, The attachment portion 2 is fixed on an external support member 10. A load point 6a is provided at the tip of the tongue-shaped pressure receiving portion 6. When a load is applied to the load point 6a from the outside, the thin portions 4a and 4b of the strain-generating portions 4 are opposed to each other. A bending moment is generated, and each strain generating portion 4 is bent into a gentle S-shape. That is, when a load is applied to the load point 6a from above, the thin portion 4a near the mounting portion 2 in the strain generating portion 4 bends to a convex shape upward, but the thin portion 4b close to the connecting portion 5 is below Therefore, the strain detecting element 7 on the part 4a detects tensile stress, and the strain detecting element 8 on the part 4b detects compressive stress. Thus, if the distortion which generate | occur | produces in the strain generation part 4 is detected by the strain detection elements 7 and 8, the load which is acting on the load point 6a can be calculated | required from the magnitude | size of the distortion.
[0004]
A load sensor configured to apply a load to the tip of a cantilevered plate-like member on which a strain detection element is mounted is also known, but this sensor has a plurality of locations that generate reverse bending moments. Therefore, it is difficult to improve the accuracy as compared with the above-described configuration.
[0005]
[Problems to be solved by the invention]
The conventional load sensor as shown in FIGS. 11 and 12 is manufactured by printing and forming a wiring pattern, strain detection elements 7 and 8 on the flat printed surface of the base body 1, and is easy to mass-produce and cost-effective. It is suitable for. However, since the printing surface side of the base body 1 including the pressure receiving portion 6 is designed to be located in the same plane, the tongue-shaped pressure receiving portion 6 is warped in the heating process when a wiring pattern or the like is printed. In some cases, the tip of the pressure receiving portion 6 having the load point 6a is positioned above the printing surface. In that case, the strain detection elements 7 and 8 cannot be smoothly printed due to interference with the tip of the pressure receiving portion 6, so that the sensing accuracy may be impaired, and the manufacturing yield is likely to decrease.
[0006]
The present invention has been made in view of the situation of the prior art as described above, and its purpose is to avoid printing defects of the strain detection element due to warping of the pressure receiving portion, to stabilize quality and to improve manufacturing yield. It is to provide a suitable load sensor.
[0007]
[Means for Solving the Problems]
As a means for achieving the above-described object, the present invention provides an attachment portion on one end side fixed to an external device, an opening adjacent to the attachment portion, and the other end from the attachment portion along the side edge of the opening. A strain-generating portion extending to the side and having at least one surface formed as a flat printing surface; a pressure receiving portion connected to the strain-generating portion on the other end side and protruding in a tongue shape into the opening; and A strain detecting element that is printed on the printing surface and detects a strain of the strain-generating portion generated according to a load applied to the pressure receiving portion, and in a state where no load is applied to the pressure receiving portion, The front end portion of the pressure receiving portion is configured to be located on the lower side in the plate thickness direction than the plane including the printing surface.
[0008]
In this way, if the tip of the pressure receiving part having the load point is previously positioned below the plane including the printing surface of the strain generating part in the plate thickness direction, the pressure receiving part is warped in the heating process during manufacturing. Also in this case, since there is no concern that the pressure receiving portion is positioned above the printing surface of the strain generating portion, it is possible to avoid printing failure of the strain detection element due to warping of the pressure receiving portion.
[0009]
In order to lower the tip end of the pressure receiving portion in advance with respect to the plane including the printing surface of the strain generating portion, for example, the plate thickness on the tip end side of the pressure receiving portion is made thinner than the plate thickness on the base end side. Alternatively, the pressure receiving portion having a uniform plate thickness may be bent so that the tip side gradually separates from the plane including the printing surface.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 is a side view of a load sensor according to a first embodiment, FIG. 2 is a plan view of the load sensor shown in FIG. 1, and FIG. FIG. 4 is a sectional view showing a modification of the pressure receiving portion shown in FIGS. 1 to 3, and FIG. 5 is a perspective view of the load sensor according to the second embodiment. FIG. 6, FIG. 6 is a plan view of an essential part of the load sensor shown in FIG. 5, FIG. 7 is a sectional view taken along the line CC of FIG. 6, and FIG. 8 is a perspective view of the load sensor according to the third embodiment. 9 is a sectional view of the pressure receiving portion of the load sensor shown in FIG. 8, and FIG. 10 is a sectional view showing a modification of the pressure receiving portion shown in FIGS. In these drawings, parts corresponding to those in FIGS. 11 and 12 used for explaining the prior art are denoted by the same reference numerals.
[0011]
First, the first embodiment will be described with reference to FIGS. 1 to 3. Reference numeral 1 in the figure denotes a load sensor base body, 11 denotes an insulating coating layer printed on the base body 1, and 12 denotes A wiring pattern printed on the insulating coating layer 11 is shown. The base body 1 is obtained by processing a single metal plate such as SUS, and includes a mounting portion 2 on the fixed end side, and a pair of strain generating portions 4 extending from both sides of the opening 3 adjacent to the mounting portion 2. The connecting portion 5 that connects the free ends of the two strain-generating portions 4 and the pressure receiving portion 6 that protrudes in a tongue shape from the connecting portion 5 into the opening 3, the tip of the pressure receiving portion 6 is The load point 6a is applied with the load of the measurement object. As shown in FIG. 1, the pressure receiving portion 6 is formed so that the tip side is gradually thinned by making the surface on which the load point 6a is provided an inclined surface, and therefore no load is applied. In the unloaded state, the tip of the pressure receiving portion 6 is disposed at a position immersed in the opening 3. Further, in the base body 1, each strain-generating portion 4 is formed thinner than the other portions and is easily bent.
[0012]
As shown in FIG. 3 (a), an insulating coat layer 11 is printed on one surface (the upper surface of FIG. 1) of the base body 1, and as shown in FIG. 3 (b), the insulating coat layer 11 is printed. A wiring pattern 12 is printed on the top. Further, as shown in FIG. 3C, strain detection elements 7 and 8 made of thick film resistors are printed at predetermined positions on each strain generating portion 4. The strain detection elements 7 and 8 formed in a total of four locations are connected by the wiring pattern 12 to constitute a Wheatstone bridge circuit. Further, a shaft hole 2a (see FIG. 3) is formed in the mounting portion 2, and a bolt 9 inserted through the shaft hole 2a is screwed into the screw hole of the external support member 10 with a strong fastening force. . That is, the attachment portion 2 is fixed on the external support member 10 by pressurizing the peripheral portion of the shaft hole 2 a with the head of the bolt 9. However, considering that the straight line group passing through the center P of the shaft hole 2a and the opening 3 is limited to the range of the angle θ in FIG. 2, the strain detection elements 7 and 8 are printed in this range. Even if the bolts 9 are formed and tightened strongly, the characteristics of the strain detection elements 7 and 8 are not adversely affected.
[0013]
In this load sensor, when a load is applied to the load point 6a at the tip of the pressure receiving portion 6, each thin strain-generating portion 4 bends. At this time, each strain generating portion 4 is bent into a gentle S-shape, and a bending moment is generated in the vicinity of the mounting portion 2 and the vicinity of the connecting portion 5, so that the strain detecting element in the vicinity of the mounting portion 2 7 detects tensile stress, and the strain detection element 8 in the vicinity of the connecting portion 5 detects compressive stress. Therefore, the load acting on the load point 6a can be obtained with high accuracy from the magnitude of the strain detected by the strain detection elements 7 and 8. In addition, in the case of this load sensor, the distance from the load point 6a to the strain detection element 7 and the distance to the strain detection element 8 are set to be approximately equal, so that the value of the tensile stress detected by the strain detection element 7 is The value of the compressive stress detected by the strain detection element 8 is substantially the same. Therefore, the Wheatstone bridge circuit including the strain detection elements 7 and 8 has a simple configuration.
[0014]
As described above, in the present embodiment, the tip portion of the pressure receiving portion 6 having the load point 6a is immersed in the opening 3 in advance, so that heating when the insulating coat layer 11 and the wiring pattern 12 are formed by printing is performed. Even when the tongue-shaped pressure receiving portion 6 is warped in the process, the tip of the pressure receiving portion 6 is positioned above the plane B (see FIG. 1) including the printing surface of the strain generating portion 4. Therefore, there is no concern that printing defects of the strain detection elements 7 and 8 due to warping of the pressure receiving portion 6 will occur. That is, the strain detection elements 7 and 8 can always be printed smoothly without being interfered with the pressure receiving portion 6, the manufacturing yield is improved, and there is no fear that the sensing accuracy of the strain detection elements 7 and 8 is impaired. Further, in this embodiment, a part of the opening 3 is interposed between the strain detection elements 7 and 8 printed on each strain generating portion 4 and the center P of the shaft hole 2a of the mounting portion 2. Since it is designed, it is considered that the distortion caused by the strong tightening force of the bolt 9 that presses the peripheral edge of the shaft hole 2a is blocked by the opening 3 and does not directly affect the strain detection elements 7 and 8. . As a result, the characteristics of the strain detection elements 7 and 8 do not vary from product to product, and the load sensor is highly reliable.
[0015]
In this embodiment, the thickness of the pressure receiving portion 6 is formed so that the tip side is gradually thinner. However, as shown in FIG. It is good also as a structure which positions the front-end | tip part of the pressure receiving part 6 below the plane B beforehand by making it bend so that it may gradually separate from the plane B containing a printing surface.
[0016]
In this embodiment, the case where the base body 1 is made of a metal plate has been described. However, the base body 1 may be an insulating substrate, and in this case, the insulating coat layer 11 is formed on the base body 1. There is no need to do it.
[0017]
Next, the second embodiment shown in FIGS. 5 to 7 will be described. In the load sensor shown in these drawings, the front and back surfaces of the tongue-shaped pressure receiving portion 6 are inclined surfaces, and the plate thickness is wedge-shaped. A tapered pressure receiving portion 6 is projected into the opening 3. Accordingly, the tip portion of the pressure receiving portion 6 is also disposed at a position immersed in the opening 3 in a no-load state where no load is applied, as in the first embodiment, and a heating process during manufacturing is performed. Even if the pressure receiving portion 6 is warped, the tip portion of the pressure receiving portion 6 is located above the printing surface of the strain generating portion 4 and there is no possibility that the printing of the strain detecting elements 7 and 8 will be hindered.
[0018]
In the second embodiment, the shape of the base body 1 is slightly different from that in the first embodiment. That is, in the base body 1 shown in FIGS. 5 and 6, each strain generating portion 4 is constricted at the middle portion in the longitudinal direction. With such a shape, when the load is applied, each strain generating portion 4 is greatly bent and the strain detection elements 7 and 8 detect a large strain, so that the detection accuracy can be further improved. .
[0019]
Next, a third embodiment shown in FIGS. 8 and 9 will be described. In the load sensors shown in these figures, the plate-like pressure receiving portion 6 is thick only on the base end side (connecting portion 5 side), and all others are thin. Therefore, similarly to the first and second embodiments, the pressure receiving portion 6 is disposed at a position where the tip end of the pressure receiving portion 6 is immersed in the opening 3 in a no-load state where no load is applied. Thus, printing defects of the strain detection elements 7 and 8 due to the warp of the pressure receiving portion 6 can be avoided.
[0020]
Further, as in the modification shown in FIG. 10, projections 6b and 6c projecting in the thickness direction are provided on both the front and back surfaces of the tip of the pressure receiving portion 6, and the tops of these projections 6b and 6c serve as load points 6a. If it is possible, it can correspond to the measurement object on either side of the front and back, so the usability of the load sensor is improved, and even if the relative position of the measurement object and the load sensor is slightly shifted in the plate surface direction, Since the load of the measurement object can be reliably applied to the load point 6a, it is easy to avoid malfunction even if there is a slight error in the load sensor mounting position.
[0021]
【The invention's effect】
The present invention is implemented in the form as described above, and has the following effects.
[0022]
Since the tip of the pressure receiving part having the load point is positioned in advance in the thickness direction lower than the plane including the printing surface of the strain generating part, the pressure receiving part can be received even when the pressure receiving part warps during the heating process during manufacturing. The tip of the part is not positioned above the printing surface of the strain generating part, and therefore printing failure of the strain detecting element due to warping of the pressure receiving part can be avoided, and the quality is stabilized and the production yield is reduced. A load sensor that can be improved can be provided.
[Brief description of the drawings]
FIG. 1 is a side view of a load sensor according to a first embodiment of the present invention.
FIG. 2 is a plan view of the load sensor shown in FIG.
FIG. 3 is a printing process diagram at the time of manufacturing the load sensor shown in FIGS.
4 is a cross-sectional view showing a modification of the pressure receiving portion shown in FIGS. 1 to 3. FIG.
FIG. 5 is a perspective view of a load sensor according to a second embodiment of the present invention.
6 is a plan view of the main part of the load sensor shown in FIG. 5. FIG.
7 is a cross-sectional view taken along the line CC of FIG.
FIG. 8 is a perspective view of a load sensor according to a third embodiment of the present invention.
9 is a cross-sectional view of a pressure receiving portion of the load sensor shown in FIG.
FIG. 10 is a cross-sectional view showing a modification of the pressure receiving portion shown in FIGS.
FIG. 11 is a plan view of a load sensor according to a conventional example.
12 is a cross-sectional view taken along line AA in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base body 2 Attachment part 2a Shaft hole 3 Opening 4 Strain part 5 Connection part 6 Pressure receiving part 6a Load point 7,8 Strain detection element 9 Bolt 10 Support member 11 Insulation coat layer 12 Wiring pattern

Claims

A mounting portion on one end fixed to an external device, an opening adjacent to the mounting portion, and extending from the mounting portion to the other end side along the side edge of the opening, at least one surface being a flat printing surface A strain generating portion, a pressure receiving portion connected to the strain generating portion on the other end side and protruding in a tongue shape into the opening, printed on the printing surface of the strain generating portion, and applied to the pressure receiving portion A strain detecting element for detecting the strain of the strain generating portion generated according to the load to be applied, and in a state where no load is applied to the pressure receiving portion, the tip portion of the pressure receiving portion is more than a plane including the printing surface. A load sensor configured to be positioned on the lower side in the thickness direction.

2. The load sensor according to claim 1, wherein the pressure receiving portion has a shape in which a plate thickness on a distal end side thereof is thinner than a plate thickness on a proximal end side.

2. The load sensor according to claim 1, wherein the pressure receiving portion is bent so that a tip end side thereof is gradually separated from a plane including the printing surface.