Load sensing apparatus with pressing member having elastic member and rigid pressing portion
A load sensing apparatus according to an aspect of the present invention includes a load sensing element including a pressure sensing portion, a housing that houses the load sensing element, and a pressing member supported by the housing, wherein the pressing member includes an elastic member that receives a load, a stiff pressing portion that is to come into contact with the pressure sensing portion, and an elastic supporting portion that supports the stiff pressing portion in the housing. When no load is applied to the pressing member, a gap is formed between the stiff pressing portion and the pressure sensing portion.
1 . A load sensing apparatus comprising:
a load sensing element including a pressure sensing portion;
a housing that houses the load sensing element; and
a pressing member supported by the housing, the pressing member including:
an elastic member configured to receive a load applied thereto;
a stiff pressing portion made of a material harder than the elastic member, the stiff pressing portion being configured to come into contact with the pressure sensing portion; and
an elastic supporting portion that supports the stiff pressing portion in the housing,
wherein, when no load is applied to the pressing member, a gap is formed between the stiff pressing portion and the pressure sensing portion,
and wherein the elastic supporting portion includes a plate spring having an arm.
2 . The load sensing apparatus according to claim 1 , wherein the elastic supporting portion is integrally formed with the stiff pressing portion.
3 . The load sensing apparatus according to claim 1 , wherein the pressing member further includes:
a rigid plate provided between the elastic member and the stiff pressing portion.
4 . The load sensing apparatus according to claim 1 , wherein the load sensing element further includes:
a displacement portion configured to be displaced in accordance with the load received by the pressure sensing portion; and
a plurality of piezoresistive elements configured to electrically detect an amount of displacement of the displacement portion.
5 . The load sensing apparatus according to claim 1 , wherein the stiff pressing portion is made of metal.
6 . The load sensing apparatus according to claim 1 , wherein the stiff pressing portion is made of silicon.
7 . The load sensing apparatus according to claim 1 , wherein the elastic member is made of metal.
8 . The load sensing apparatus according to claim 1 , wherein the elastic member includes:
a first contact portion including a first contact point configured to receive the load;
a second contact portion including a second contact point configured to come into contact with the stiff pressing portion; and
a vertical portion extending from the first contact portion toward the second contact portion such that a space is formed between the first contact portion and the second contact portion,
and wherein the second contact portion is further configured to elastically deformed toward the first contact portion via the space by resistance from the stiff pressing portion when the load is applied to the pressing member.
9 . The load sensing apparatus according to claim 8 , wherein the first contact portion, the second contact portion, and the vertical portion are integrally formed of a single piece of metal plate.
10 . The load sensing apparatus according to claim 1 , further comprising:
an integrated circuit housed in the housing, the integrated circuit having the load sensing element thereon.
11 . The load sensing apparatus according to claim 1 , wherein the housing includes:
a restricting portion configured to restrict movement of the stiff pressing portion in a direction perpendicular to a pressing direction.
12 . The load sensing apparatus according to claim 1 , further comprising:
a cover disposed over the pressing member on an opposite side from the housing, the load being applied to the elastic member via the cover.
13 . The load sensing apparatus according to claim 12 , wherein the cover includes:
a protruding portion configured to come into contact with the elastic member.
14 . The load sensing apparatus according to claim 13 , wherein the elastic member is integrated with the protruding portion.
15 . The load sensing apparatus according to claim 12 , further comprising:
a stopper configured to restrict a decrease in a relative distance between the cover and the housing.
16 . The load sensing apparatus according to claim 13 , wherein the elastic member is connected to the protruding portion.
17 . The load sensing apparatus according to claim 1 , wherein the stiff pressing portion has an elastic modulus higher than that of the elastic member.
18 . The load sensing apparatus according to claim 1 , wherein the stiff pressing portion has such a stiffness that the pressure sensing portion is not pressed into the stiff pressing portion beyond a contact surface when the load is applied to the elastic member.