JPH05332859A - Force detector - Google Patents

Abstract

PURPOSE:To obtain a compact, rugged force detector, which is hard to be affected by noises and has high detection sensitivity. CONSTITUTION:Strain gages 51, 52, 53 and 54 are formed on the outer surface of a cylindrical base body 2 as a unitary body. A ceramic substrate 3 is provided so as to cover the opening at one end of the base body. A signal processing circuit 4 having a bridge circuit, which is electrically connected to the strain gages, is provided on the substrate 3 in this constitution. Therefore, the detector can be made compact and rugged. Since the gage elements and the circuit are close, the detector is hard to be affected with noises, and the detection accuracy can be made high. Since the circuit is housed in the cavity in the base body 2, stability and reliability can be secured.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to force detectors. For example, the present invention relates to a force detector suitable for detecting measurement pressure in various measuring instruments.

[0002]

BACKGROUND ART In various measuring instruments, it is necessary to keep the measurement pressure constant in order to improve the measurement accuracy. Conventionally, as a method of keeping the measurement pressure constant, a type that uses human senses,
There are various types such as a type that uses gravity and a type that uses spring pressure, but none of them is sufficient to increase the measurement speed or further improve the measurement accuracy.

Therefore, a strain gauge is formed on a thin plate, and the measured pressure is monitored using a force detector in which the strain gauge and an external signal processing circuit (including a bridge circuit) are connected by a signal line. It is possible to keep it constant. Alternatively, it is conceivable to use a pressure sensor formed on the silicon substrate by the LSI process technology.

[0004]

However, although the former force detector has a very high sensitivity, it is hard to say that it is small when an external signal processing circuit is included. It has the drawback of being too much. Moreover, since the strain gauge and the external signal processing circuit are connected by a signal line, there is a drawback that they are easily affected by noise.

The latter pressure sensor has high sensitivity and a very small size, but is not suitable as a force detector.
Because it is a pressure detection principle using deformation of the silicon thin film, it is suitable for pressure detection of fluids and gases, but in order to apply it to a measuring instrument, it is necessary to convert force into fluid pressure, This is because this work is difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a force detector which is small in size, robust, and less susceptible to noise and has high detection sensitivity.

[0007]

Therefore, in the force detector of the present invention, a strain gauge is integrally formed on the peripheral surface of the base body and is electrically connected to the strain gauge at one axial end of the base body. As a configuration, a substrate provided with wiring is provided, and a signal processing circuit that is connected to the strain gauge through the wiring and detects a force acting on the substrate from a change in resistance value of the strain gauge is provided on the substrate. is there.

[0008]

[Function] While forming a strain gauge on the peripheral surface of the base,
Since the board is provided at one end of the board and the signal processing circuit is provided on the board, the board can be made compact and robust. Moreover,
Since the strain gauge and the detection circuit are close to each other, it is less susceptible to noise and the detection sensitivity can be increased.

[0009]

The preferred embodiments of the force detector of the present invention will be described below in detail with reference to the accompanying drawings.

First Embodiment A first embodiment is shown in FIGS. FIG. 1 is an external perspective view of the force detector of this embodiment, FIG. 2 is a sectional view thereof, and FIG. 3 is an exploded perspective view thereof. As shown in these figures, the force detector 1 according to the present embodiment has a cylindrical base 2 having a cavity 2A inside.
And a ceramic substrate 3 for closing one end opening of the base body 2,
Signal processing circuit 4 mounted on the ceramic substrate 3
It consists of and.

A strain gauge 5 is formed on the outer peripheral surface of the base 2 by chemical treatment. Strain gauge 5
Is a film in which a conductive film is folded back in a zigzag shape along the circumferential direction by a chemical treatment on the outer peripheral surface of the substrate 2, and is divided in the circumferential direction as shown in FIGS. 4 (A) and 4 (B). It includes four strain gauge elements 5 _1, 5 _2, 5 _3, 5 ₄ . The line width, the number of turns, the pitch, the length, and the like of the zigzag pattern are determined according to the characteristics of the material forming the strain gauge 5 and the required detection sensitivity. Further, as a material forming the strain gauge 11, a copper-nickel alloy or the like is suitable in the case of metal, and a vapor deposition film of germanium or silicon in the case of semiconductor is suitable.

The ceramic substrate 3 is formed in a disk having an outer diameter dimension slightly larger than the outer diameter dimension of the base body 2. Wirings 6 electrically connected to the strain gauge elements 5 _{1 to} 5 _{4 of the} strain gauge 5 are printed on the surface side of the disk, and each strain gauge element is provided at the center position through the wiring 6. A signal processing circuit 4 connected to 5 _{1 to} 5 ₄ is provided. The power supply line 7 to the signal processing circuit 4 and the output signal line 8 from the power supply line 7 are led out to the back surface side of the substrate 3 through through holes 9 formed in the substrate 3.

The signal processing circuit 4 is formed with bridge circuits 10 _z1 and 10 _z2 shown in FIG. That is, 4
Of the two strain gauge elements 5 _{1 to} 5 ₄ , two strain gauge elements 5 ₁ , 5 ₃ and 5 _2, 5 ₄ which are arranged symmetrically with respect to the axis of the base body 2 were inserted into the opposite sides. Two bridge circuits 10 _z1 and 10 _z2 are formed. The resistors surrounded by the rectangular frame are dummy resistors (the same applies hereinafter). The outputs V _{1 and} V ₂ of the bridge circuits 31 and 32 are added to each other and output as a signal proportional to the force Fz (see FIG. 4) in the axial direction (Z direction) of the base 2.

By the way, the strain gauge 5 is integrally formed on the outer peripheral surface of the base body 2 by a chemical treatment as follows. FIG. 6 shows the process. Here, the base 2 is made of metal. First,
In (A), the base 2 is rotated, and the insulating film 11 (for example, SiO 2) is formed on the outer peripheral surface of the base 2 by the CVD method or the like.
₂ etc.) to form. Subsequently, in (B), a conductive film 12 such as a metal film or a semiconductor film is formed on the insulating film 11 by a process such as vapor deposition or plating.

Next, in (C), a positive resist film 13 is coated thereon, and then in (D),
The laser beam 14 or the like is irradiated to draw the zigzag pattern shown in FIGS. At this time, the line in the strain gauge 5 is thin, and the line in the wiring portion is sufficiently thick.
Then, in (E), after removing the resist film 13 other than the portion irradiated with light by development, the exposed conductive film 12 is removed by etching. As a result, the strain gauges shown in FIGS. 3 and 4 are formed, but when the strain gauge is finally covered with the protective film, it is completed.

By the way, the chemical treatment described here is
The process is almost the same as the LSI manufacturing process, except that the surface for pattern formation is not a flat surface but a cylindrical surface.
However, this can be realized by adding a rotation drive mechanism for rotating the base 2 to the LSI manufacturing apparatus. Moreover, considering that the pattern rule is on the order of 100 μm or more, it is much easier than the LSI manufacturing.

Next, an assembling method and an example of use of the force detector 1 of this embodiment will be described. First of all, when assembling,
Place the signal processing circuit 4 at the center of the ceramic substrate 3,
It is electrically connected to the printed wiring 6. Then, the base 2 is placed on the substrate 3 so that the signal processing circuit 4 can be accommodated in the cavity 2A, and then the terminal portions of the strain gauge elements 5 _{1 to} 5 _{4 on} the outer peripheral surface of the base 2 and the ceramic substrate 3 are placed. The necessary portions of the printed wiring 6 are connected by soldering. Thereby, the force detector 1 is assembled. The lower end surface of the base body 2, that is, the portion of the ceramic substrate 3 that contacts the wiring 6 is subjected to an insulation treatment.

In addition, it can be used as shown in FIG. FIG. 7 shows the force detector 1 of this embodiment.
This is an example in which is used for the bench type micrometer 20. The bench-type micrometer 20 includes an anvil support tool 23 and an anvil 2 on one standing arm 22 of a bench-type base 21.
4, while holding the micrometer head 26 on the other standing arm 25 coaxially with the anvil 24, the spindle 27 of the micrometer head 26 is thimble 2
In addition to the turning operation of 8, the motor built in the base 21 (motor not shown, which is started and stopped by the switch 29) is driven to move back and forth with respect to the anvil 24. Here, the force detector 1 of the present embodiment is provided at the tip of the anvil 24.

Now, after inserting the object to be measured between the force detector 1 provided at the tip of the anvil 24 and the spindle 27, the switch 29 is turned on to drive the motor.
The spindle 27 of the micrometer head 26 is advanced toward the anvil 24. When the tip of the spindle 27 comes into contact with the object to be measured and the object to be measured is sandwiched between the spindle 27 and the force detector 1, an axial force Fz acts on the force detector 1. Then, the signal processing circuit 4
Outputs a signal (V ₁ + V ₂ ) proportional to the force Fz. Therefore, by monitoring the signal (V ₁ + V ₂ ) and stopping the motor when the preset reference level is reached, the measured pressure can be kept constant at all times.

Therefore, according to the first embodiment, four strain gauge elements 5 _1, 5 _2, 5 _3, 5 ₄ are formed on the outer peripheral surface of the cylindrical substrate 2 by chemical treatment, and the strain gauge elements are formed. 5 _1,
Two bridge circuits 10 _z1 and 10 including 5 _2, 5 _{3 and} 5 ₄
since it is configured to _z2, if adding the output V _1, V ₂ of the bridge circuits 31 and 32 to each other, it is possible to obtain a signal proportional to the axial force Fz. Moreover, since the ceramic substrate 3 is provided by closing the one end opening of the base body 2 and the signal processing circuit 4 including the bridge circuits 10 _z1 and 10 _z2 is provided on the ceramic substrate 3, a compact and robust structure can be achieved and noise can be reduced. It is difficult to be affected by and the detection sensitivity can be increased. In particular, since the signal processing circuit 4 is housed in the cavity 2A of the base body 2 in a hermetically sealed state, the stability and reliability of the operation can be secured. Furthermore, it is easy to assemble and inexpensive.

Second Embodiment A second embodiment is shown in FIGS. 8 and 9. In the description of these drawings, the same components as those in FIGS. 1 to 7 described above are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, two forces Fx and Fy in the direction perpendicular to the axial direction (Z direction) can be detected. As shown in FIGS. Four strain gauge elements 5 _11, 5 _12, 5 _13, 5 ₁₄ are formed on the outer peripheral surface at symmetrical positions about the X and Y axes, respectively. Further, the signal processing circuit 4, as shown in FIG. 9, four strain gauge elements 5 _11, 5 _12, 5 ₁₃ among the two strain gauge elements arranged at symmetrical positions around the axis of the base body 2 Two bridge circuits 10y and 10x are formed in which 5 _11, 5 ₁₃ and 5 _12, 5 ₁₄ are respectively inserted in adjacent sides.

Therefore, according to the second embodiment, in addition to the effect described in the first embodiment, the signal V ₃ proportional to the force Fx perpendicular to the axial direction (Z direction) is obtained from the bridge circuit 10x. Further, the signal V ₄ proportional to the force Fy which is perpendicular to the axial direction (Z direction) and perpendicular to the force Fx can be obtained from the bridge circuit 10y. for that reason,
For example, it can be used for a two-dimensional measuring machine or the like that measures the dimensions and the like of an object to be measured by bringing the object and the probe into contact with each other while relatively moving them in two-dimensional directions orthogonal to each other.

The strain gauge elements 5 _1, 5 _2, 5 _3, shown in FIG.
5 ₄ and the strain gauge elements 5 _11, 5 _12, 5 _13, 5 _{14 of} FIG. 8 are formed on the outer peripheral surface of the substrate 2, and the bridge circuit 10
_By combining _z1 , 10z2, 10y and 10x, it is possible to simultaneously obtain signals proportional to the forces Fz, Fx and Fy in the three directions.

Third Embodiment A third embodiment is shown in FIG. In the description of these drawings, the same components as those in FIGS. 1 to 7 described above are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the strain gauge element 5 shown in FIG. 4 is used._1,5
_2,5_3,5_FourThe four bridge circuits 10 of FIG.
_1,10_2,10_3,10_FourEmbedded in the output e_1,e_2,e
_3,e _FourTo calculate forces Fz, Fx, Fy in three directions at the same time.
This is to obtain a proportional signal.

The output e _{1, of} each bridge circuit 10 _1, -10 ₄
e _2, e _3, e ₄ are: e ₁ = −αFx + βFy + γFz ………… (1) e ₂ = −αFx−βFy + γFz ………… (2) e ₃ = αFx−βFy + γFz ………… ...... (3) e ₄ = αFx + βFy + γFz ……………… (4) Note that α, β and γ are coefficients.

From these equations (1) to (4), e ₁ + e ₂ + e ₃ + e ₄ = 4γFz ...... (5) (e ₃ + e ₄ )-(e ₁ + e ₂ ) = 4αFx ......
(6) (e ₁ + e ₄ ) − (e ₂ + e ₃ ) = 4βFy ...
(7) holds.

Therefore, according to the third embodiment, in addition to the effects described in the first embodiment, the forces Fz, Fx, F in the three directions are simultaneously obtained.
Since y can be detected, the contact with the object to be measured can be detected with high sensitivity by incorporating it into the touch signal probe of the coordinate measuring machine.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this embodiment, and various improvements and design changes can be made without departing from the gist of the present invention. It is possible.

For example, the signal processing circuit 4 may be mounted on the back surface side of the substrate 3 as shown in FIG. 11 when the signal processing circuit 4 does not fit in the cavity 2A of the substrate 2. In this case, instead of mounting all of the signal processing circuit 4 on the back surface side of the substrate 3, a part of the signal processing circuit 4 that cannot be accommodated in the cavity 2A of the substrate 2 may be mounted on the back surface side of the substrate 3.

Further, in each of the above-described embodiments, an example in which the force detector 1 is used as a measuring device has been described, but the use example is not necessarily limited to the measuring device, and a force such as a general processing machine or control machine can be used. It can also be used by attaching it to a site that needs to be detected.

[0033]

As described above, according to the present invention, it is possible to provide a force detector which is small in size, is robust, is not easily affected by noise, and has high detection sensitivity.

[Brief description of drawings]

FIG. 1 is an external perspective view showing a first embodiment of the present invention.

FIG. 2 is a sectional view of the above embodiment.

FIG. 3 is an exploded perspective view of the above embodiment.

FIG. 4 is a diagram showing a strain gauge pattern of the above-mentioned embodiment.

FIG. 5 is a diagram showing a bridge circuit of the embodiment.

FIG. 6 is a diagram showing a strain gauge manufacturing process according to the embodiment.

FIG. 7 is a diagram showing a usage example in which the force detector of the above-mentioned embodiment is used in a bench-type micrometer.

FIG. 8 is a diagram showing a strain gauge pattern in a second embodiment of the present invention.

FIG. 9 is a diagram showing a bridge circuit of the embodiment.

FIG. 10 is a diagram showing a bridge circuit according to a third embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a modified example of the present invention.

[Explanation of symbols]

1 power detector 2 base 3 ceramic substrate 4 signal processing circuit 5 strain gauge 5 _1, 5 _4, 5 _11, 5 ₁₄ strain gauge element _{10 z1, 10 z2, 10 x} , 10 y, 10 1 ~10 4 bridge Circuit 16 wiring

Claims (1)

[Claims] 1. A strain gauge is integrally formed on a peripheral surface of a substrate, and a substrate provided with wiring electrically connected to the strain gauge is provided at one axial end of the substrate, and the wiring is provided on the substrate. A force detector comprising a signal processing circuit which is connected to the strain gauge via the sensor and detects a force acting on the substrate from a change in resistance value of the strain gauge.