JPH0387622A - Force sensor and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a sensor element, to enhance the output sensitivity, and also, to eliminate the need of secondary working of a pressure pin and a cylinder by fixing plural strain gauges to the bottom face of the inside of the cylinder for fixing a sensor supporting part and forming a bridge circuit. CONSTITUTION:In the case of a sensor element 1 and a pressure pin 106 come into contact with each other and a constant-voltage is supplied to the sensor element 1, a bridge circuit formed by a diffused resistor (not shown in the figure) is well-balanced. However, when external force is applied to the pressure pin 106, a deflection is generated in the sensor element 1, the balance of the diffused resistor is lost and an output voltage is varied. When the external force is further increased, the deflection quantity of the sensor element 1 is also increased, and in the end, a plate spring 105 comes into contact with the upper face of a cylinder 102 and the maximum output is obtained. Moreover, when a larger load is applied, a deflection is generated on the upper face of the cylinder 102, and the sensor element 1 is broken down. Therefore, in the case of deflection is generated on the upper face of the cylinder 102, an output is obtained by the bridge circuit constituted of a strain gauge 103, and a double damage preventive structure of the sensor element 1 is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a force sensor that detects an external load by applying an external load to a sensor element via a pressure pin, and a method for manufacturing the same. The present invention relates to a force sensor that detects an external load applied to a pressurizing pin by converting mechanical displacement of a diaphragm portion of a single crystal substrate being pressurized into an electrical signal, and a method for manufacturing the same.

[Conventional technology]

A conventional force sensor will be explained with reference to cross-sectional views in FIGS. 2 and 3.

FIG. 2 is a sectional view showing an example of a conventional force sensor, and FIG. 3 is a sectional view showing a case where the end face of the pressure pin 5 shown in FIG. 2 is processed. A silicon diaphragm type sensor element (hereinafter abbreviated as sensor element) 1 is joined to a base 2, and the sensor element 1
and the stand 2 are connected by a wire 3. Base 2 is the middle tube 4
The pressure pin 5 slides inside the cylinder 6, and the spring 7 cushions the shock transmitted from the pressure pin 5 to the sensor element 1.

The sensor element 1 has a diaphragm structure, and when a large force is applied, the deflection limit of the diaphragm portion is exceeded and damage occurs. Therefore, in order to prevent the pressure pin 5 that contacts the sensor element 1 from applying pressure to the sensor element 1 beyond the deflection limit of the diaphragm portion, it is necessary to limit the amount of movement of the pressure pin 5. In the conventional force sensor, on the premise that the contactor (not shown) that applies an external load is larger than the outer diameter of the end surface of the pressure pin 5, the force is applied from the end surface of the cylinder 6 within the diaphragm damage limit. The tip of the pressure pin 5 was made to protrude slightly.

To explain the manufacturing process for making the tip of the pressure pin 5 slightly protrude in this way, as shown in FIG.
Processing spacer 8. having a thickness equivalent to the dimension in which the tip thereof protrudes from the end surface of the cylinder 6. and pressurizing pins 5 are sequentially inserted into cylinder 6, and using pressurizing tightening screws 9, pressurizing pins 5. and fix the processing spacer 8. Next, in this state, secondary processing by cutting or grinding is performed until the end face of the tip of the pressure pin 5 and the end face of the cylinder 6 become flush with each other. When finally mounting the pressure pin 5, the pressure tightening screw 9 is loosened and the machining spacer 8 is removed, so that the pressure pin 5 slightly protrudes from the end surface of the cylinder 6. Ta.

[Problem to be solved by the invention]

However, in the conventional force sensor described above, the amount of protrusion of the pressure pin 5 from the end surface of the cylinder 6 needs to be extremely small, 10 μm, and the materials of the cylinder 6 and the pressure pin 5 are different. Due to the processing characteristics of the material itself, it is difficult to obtain a completely uniform surface in secondary processing such as cutting or grinding. If the machining accuracy of the single part of the tube 6 is poor, even if a uniform surface is obtained by secondary machining, when the machining spacer 8 is removed, an appropriate amount of protrusion will not be obtained, resulting in poor reproducibility and poor reliability. It was missing.

The shape of the contact that applies force to the pressure pin 5 from the outside is the cylinder 6.
If the pressure pin 5 is larger than the shape of the pressure pin 5 that slightly protrudes from the end surface of the cylinder 6, the end surface of the cylinder 6 acts as a stopper, and the amount of movement of the pressure pin 5 is limited, making it possible to prevent damage to the sensor element 1. However, if the shape of the contactor is smaller than the shape of the pressure pin 5, the end surface of the tube 6 will not act as a stopper, making it impossible to prevent damage to the sensor element 1.

Furthermore, if an excessive load is applied to the pressure pin 5, the entire cylinder 6 is deformed by the load, causing damage to the sensor element 1, which has the disadvantage that damage to the sensor element 1 cannot be prevented. .

The purpose of the present invention is to prevent the destruction of the sensor element, have high output sensitivity, eliminate the need for secondary processing of the pressure pin and cylinder, have high structural rigidity, and be easy to assemble. An object of the present invention is to provide a force sensor having a structure for sensing the amount of deformation of a cylinder in advance, and a method for manufacturing the same.

[Means to solve the problem]

1. The force sensor of the present invention comprises a sensor element, a sensor support part that is separated from a base and a middle cylinder for fixing this sensor element, a cylinder for fixing this sensor support part inside, and a bottom surface inside this cylinder. A plurality of strain gauges are fixed to the cylinder and form a bridge circuit, a ring-shaped spacer is provided on the periphery of the end face of one end of the cylinder, and a leaf spring is connected through the spacer and has a hole in the center. and a pressure pin which is inserted into the center of the end surface of one end of the cylinder and a hole provided in the leaf spring, and whose flange part provided at one end is fixed to the leaf spring, and A top plate is provided.

2. The method for manufacturing a force sensor of the present invention includes the tube.

A step of joining the spacer, the leaf spring, the pressure pin, and the upper plate; a step of joining the plurality of strain gauges fixed to the inner bottom surface of the cylinder; and the sensor element and the strain gauge. and a step of joining and integrating the tubes.

〔Example〕

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

FIG. 1 is a sectional view of a force sensor showing an embodiment of the present invention.

In FIG. 1, a sensor element 1 is joined to a base 2 having a plurality of input/output terminals with high positioning accuracy, and the sensor element 1 and the input/output terminals of the base 2 are connected by wire bonding or the like. Further, this stand 2 is press-fitted into a middle cylinder 101 having a plurality of fine holes in its outer circumferential portion to constitute a sensor support portion. Further, the tube 102 has a fitting hole at one end into which the middle tube 101 is inserted, a hole in the center of the fitting hole, and a plurality of holes on the outer periphery of the hole, which is the bottom surface of the fitting hole. A strain gauge 103 is bonded to form a bridge circuit. - direction, this strain gauge 10
The bridge circuit No. 3 passes through a plurality of fine holes on the outer periphery of the middle cylinder 101 and is connected to the input/output terminal of the base 2. Here, the spacer 104 has a ring shape with an outer diameter equivalent to that of the tube 102. Further, the leaf spring 105 has the same outer diameter shape as the cylinder 102 and the spacer 104, and
It has a hole smaller than the central hole of No. 2. Note that this leaf spring has a shape with multiple concentric grooves inside,
When the shape has a plurality of radial grooves, an advantageous feature is that the thickness of the leaf spring can be increased. Moreover, the pressure pin 106 has a cylindrical shape in which the central part has the same shape as the hole in the center of the leaf spring 105, and one end has a needle tip shape.
The other end has a flange portion having a spherical end surface.

Further, the upper plate 107 has a cylinder 102° spacer 104. and has the same outer diameter shape as the leaf spring 105, and has a hole in the center that is larger than the flange part of the pressure pin 106,
The outer periphery of this hole has a counterbore up to the width of the ring shape of the spacer 104.

The spacer 104 prevents the deformation of the leaf spring 105 and the pressure pin 1.
06, and at the same time, it also serves as a stopper to limit the amount of deflection of the diaphragm portion and protect the diaphragm portion from damage. In the embodiment of the present invention, the thickness of the spacer 104 is limited to 10 μm.

Next, the manufacturing process of the force sensor will be described with reference to FIG.

The force sensor according to the embodiment of the present invention can be roughly divided into a sensor support part and an outer cylinder part.

The sensor element 1 has a diaphragm portion processed by a normal integrated circuit manufacturing process and anisotropic etching.
The sensor element 1 and the base 2 are bonded to the base 2, and then the sensor element 1 and the base 2 are connected by wire bonding to form the element part as a force sensor.Next, the inner cylinder 101 is press-fitted into the base 2, and the sensor element 101 is connected to the base 2 by wire bonding. The sensor support part is completed.

The outer cylinder portion of the force sensor is a cylinder 102. Spacer 104, leaf spring 105. Pressure pin 106. and an upper plate 107 made of a metal material. This integration of the outer cylindrical portion is achieved by sequentially laminating the respective parts and welding them using diffusion bonding, electron beam welding, laser welding, or the like. Among these, diffusion bonding is the most effective because it causes less thermal deformation during bonding.

Next, four strain gauges 103 are glued to the outer periphery of the hole in the bottom of the cylinder 102 of the outer cylinder part of the integrated force sensor.
A Wheatstone bridge circuit is formed in the same way as the sensor element.

Thereafter, the lead wire of the circuit constituted by this strain gauge 103 is passed through the fine hole on the outer periphery of the middle tube 101, and at the same time, the middle tube 101 is inserted into the fitting hole of the tube 102. In this state, if the inner cylinder 101 and the cylinder 102 are joined using an electron beam, laser welding, or adhesive, the sensor support part and the outer cylinder part are integrated. Furthermore, if the lead wire of the circuit constituted by the strain gauge 103 is connected to the input/output terminal of the base 2, the force sensor of the present invention is completed, and the manufacturing process of the force sensor is completed. Note that this force sensor has a structure in which the tip of the pressure pin 106 and the surface of the sensor element 1 are always in contact.

Next, the operating state of the force sensor will be explained based on FIG. (not shown) is balanced. However, when an external force is applied to the pressure pin 106, the sensor element 1 is deflected, the balance of the diffusion resistance is disrupted, and the output voltage changes. When the external force further increases, the amount of deflection of the sensor element 1 also increases, and eventually the leaf spring 105
Maximum output is obtained by contacting the top surface of 02.

Furthermore, when a larger load is applied, the upper surface of the cylinder 102 is bent, and the sensor element 1 is destroyed. So tube 10
If the upper surface of 2 is deflected, strain gauge 10
An output is obtained by a bridge circuit composed of 3, and the sensor element 1 has a double damage prevention structure.

The above is when the external force increases, and when it decreases, the above is the opposite.

〔Effect of the invention〕

As explained above, according to the present invention, by installing a bridge circuit using a strain gauge inside the cylinder, damage to the double-structured diaphragm part can be prevented, and reliability as a sensor is improved. Furthermore, since the tip of the pressure pin to which external force is transmitted has a hemispherical shape, the shape is not influenced by the shape of the contact that acts on the pressure pin from the outside. Furthermore, since the pressure pin is constantly in contact with the top surface of the sensor element, there is no output loss due to friction, and output characteristics are improved.

The sensor has a simple structure and can be miniaturized. Furthermore, by changing the thickness of the leaf spring to which the pressure pin on the upper part of the cylinder is joined, it is possible to use it in a wide range of applications, such as for small loads and for high loads.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a force sensor showing an embodiment of the present invention;
FIG. 2 is a sectional view of a conventional force sensor, and FIG. 3 is a sectional view showing a case where the cross section of the pressure pin 5 of the conventional force sensor shown in FIG. 2 is processed. ...Sensor element, 2...unit, 3...wire rod, 4,
101... Middle cylinder, 5,106... Pressure pin, 6,1
02... Cylinder, 7... Spring, 8... Spacer for processing, 9... Tightening screw for processing, 103... Strain gauge, 104... Spacer, 105... Leaf spring, 107 ...Upper board.

Claims (1)

[Claims] 1. A sensor support part consisting of a sensor element, a stand and a middle cylinder for fixing the sensor element, a cylinder for fixing the sensor support part inside, and a sensor support part for fixing the sensor element to the inner bottom surface of the cylinder. , a plurality of strain gauges forming a bridge circuit, a ring-shaped spacer provided on the peripheral edge of the end face of one end of the cylinder, a plate spring having a hole in the center part through the spacer, and the above-mentioned a pressure pin that is inserted into a hole provided in the central part of the end face of one end of the tube and the leaf spring, and whose flange part provided at one end is fixed to the leaf spring; and a pressure pin provided on the upper surface of the leaf spring. A force sensor comprising: an upper plate; 2. a step of joining the cylinder, the spacer, the leaf spring, the pressure pin, and the upper plate; a step of joining the plurality of strain gauges fixed to the bottom surface inside the cylinder;
2. The method of manufacturing a force sensor according to claim 1, further comprising the step of joining and integrating the sensor element, the strain gauge, and the cylinder.