JPH01167615A - Position detecting device - Google Patents

Abstract

PURPOSE:To facilitate operation for aligning a slit plate with a shaft by pressing the slit plate against an elastic member through a pressure plate. CONSTITUTION:Light from a light source passes through a slit made in the slit plate 2 and reaches a photodetector. As the shaft 1 rotates, the slit of the fixed slit plate 2 opens and closes the optical path between the light source and photodetector. The width and pitch 4 of the slit of the slit plate 2 are decreased to attain high density, thereby improving the accuracy of position detection. The elastic member 6 is made of a rubber-made O ring and presses the slit plate 2 through the pressure plate 7. The quantity of deformation of the member 6 is determined by the gap between a holding member 8 and the pressure plate 7 and the holding member 8 is fixed abutting on the shaft 1, so the gap is constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photoelectric position detection device used for detecting a rotation angle, and in particular to improving the fixing of a slit plate for rotation angle detection.

Conventional technology In recent years, there has been a demand for highly accurate detection for position detection devices.
Therefore, in photoelectric position detection devices, it is required to improve the mounting accuracy of the detection slit plate.

An example of the above-mentioned conventional position detection device will be described below with reference to the drawings.

FIG. 2 is a sectional view of a main part of a conventional position detection device. 1 is a rotatable shaft, 2 is a slit plate, and 3 is an elastic member.

Light from a light source (not shown) passes through a slit provided in a slit plate and reaches a photodetector (not shown). As the axis 10 rotates, the slit of the slit plate 2 fixed thereto opens or closes the optical path between the light source and the photodetector. The position is detected based on the change in the amount of light at this time. In order to improve the position detection accuracy, the width and pitch of the slits provided in the slit plate 2 are narrowed, and the slits are arranged in high density. If the center of rotation deviates from the center of rotation, the output of the photodetector becomes unstable, and the photodetector has the drawback of not being usable as a position detector. Furthermore, even if it could be used, it had the disadvantage of reduced accuracy. For this reason, assembly adjustment is performed to align the slit portion of the slit plate 2 with the center of the shaft 1. Therefore, various efforts have been made to fix and temporarily fasten the shaft 1 and the slit plate 2.

FIG. 2 shows one example of this, in which the elastic member 3 has a disc spring-like shape, the inner diameter part of which is in contact with the outer circumference of the shaft 1, and the outer diameter part of which is in contact with the slit plate 2. The elastic member 3 is pressed against the slit plate 2 and fixed by the force of the two contact parts, and the slit plate 2 is pressed against the 7-rank part 1a of the shaft 1 by the deformation restoring force of the elastic member 3. At this time, the slit plate 2 is the flange portion 1a of the shaft 1.
Since the position is determined only by the force of the contact surface between the contact surface and the elastic member 3, when adjusting the center alignment of the shaft and the slit plate, the slit plate 2 cannot be moved with force greater than the static force. This allows the position of the slit plate 3 to be adjusted.

On the other hand, FIG. 3 is a sectional view of a main part of a position detection device showing a second conventional example. 1 is a shaft and 2 is a slit plate, which is the same as the first conventional example. 4 is a nut that is integrated with a screw 1b provided on the shaft 1, and 6 is a spacer provided between the nut 4 and the slit plate 2. In this example, Nat4
, and press and fix the slit plate 2 through the spacer 4. In this case, the slit plate 2 and the nut 4 are in surface contact with each other via the spacer 4, and the possibility of center deviation after alignment due to elastic deformation and restoration, which was seen in the first conventional example, is reduced.

Problems to be Solved by the Invention However, in the first example above, when adjusting the slit plate, if the frictional force is large, the slit plate moves with a large force;
Fine adjustment becomes difficult, and conversely, if it is too small, relative movement may occur during the work to fix the shaft 1 and the slit plate 2.
There is a problem that the center is shifted. In this example, the frictional force that is the key to the adjustment work is managed only by the amount of pushing of the elastic member 3 into the shaft 1, and obtaining the fastest value or the value of the frictional force suitable for adjustment is a matter of the work. Required experience and skill. In addition, the elastic member 3 is shaped like a metal plate, and the slit plate 3 is a thin plate, and the contact part is a line contact, but microscopically, the metal plate is connected to the glass plate at the contact part. Due to this phenomenon, after the centering work is completed, the elastic deformation caused by this minute portion is restored, resulting in center deviation.

On the other hand, in the second example, the frictional force is managed by tightening the nut, so this difficulty is alleviated.

A paper spacer is used. By using paper, the nut tightening range that can be adjusted can be expanded to some extent, and there is no slippage between the slit plate 2 and the spacer 4 when the slit plate is moved to adjust the center of the slit plate 2. It has the advantage of causing no return. However, it is very difficult to manage the frictional force, and the slit plate 2 is easily damaged.

In view of the above problems, the present invention provides a position detector that facilitates alignment of a slit plate and a shaft to enable highly accurate position detection.

Means for Solving the Problems In order to solve the above problems, the position detector of the present invention has a structure in which an elastic member presses the slit plate in the axial direction through the holding plate. .

Function: With the above-described configuration, the present invention obtains a constant frictional force by deforming the elastic member by a certain amount, and by interposing a presser plate between the slit plate and the elastic member, it deforms the elastic member in the radial direction. This deformation can be absorbed by the sliding of the presser plate, and positioning without resetting can be realized.

Embodiment Hereinafter, a position detection device according to an embodiment of the present invention will be explained with reference to FIG. 1 is a shaft and 2 is a slit plate, which are similar to the conventional example. e is an elastic member and a rubber ring Q IJ
7 is a holding plate, which is an iron plate with a clean surface. 8 is a holding member for the elastic member 6, and 9 is a nut for fixing the holding member 8 to the shaft.The holding member 8 comes into contact with a part of the shaft and its position is fixed.

The slit plate 2 is in contact with the shaft 1 as in the conventional example, but the amount of deformation of the elastic member 6 is determined by the gap between the holding member 8 and the holding plate 7, and the holding member 8 is fixed in drawing contact with the shaft. , this gap is constant. Furthermore, by determining in advance the amount of deformation of the elastic member that will provide a frictional force suitable for adjustment, and designing the clearance accordingly, a structure suitable for adjustment can be obtained. In this embodiment, a rubber Q IJ song with a wire diameter of 2+ml+ was used as the elastic member 6, and the amount of change in diameter was set to be 15 to 20 inches. In addition, the nut 9 of this embodiment is simply for fixing, and is not an adjustment nut as in the second conventional example, so the work is simple. In this way, there is no need to adjust the frictional force, and furthermore, the nut 9 always maintains a suitable frictional force. is obtained. In addition, by interposing the presser plate 7 between the elastic member 6 and the slit plate 2, the slit plate 2 receives only frictional force when moving in the radial direction, that is, when aligning the center, and the elastic member 6 is deformed in the radial direction. Even if the resistance force increases, the deformation is absorbed by the sliding between the slit plate 2 and the holding plate 7. Therefore, the radial deformation of the elastic member that causes the return is always less than the frictional force and does not pose a problem.

Although a rubber O-ring was used as the elastic member 6 in this embodiment, the present invention is not limited to this, and the amount of deformation may vary depending on the content of the adjustment work, the method, the material between the slit plate, the shaft, and the presser plate, etc. There are differences in the optimal frictional force depending on the surface condition or the frictional force obtained by deformation, and it changes accordingly. Therefore, the value changes depending on each case.

Furthermore, the method of fixing the elastic member is not limited to nuts, and any fixing method that can keep the deformation of the elastic member constant may be used. Furthermore, the holding plate is not limited to a metal plate, and may have a rigidity that does not transmit local deformation of the elastic member to the slit plate, and a coefficient of friction that is similar to or smaller than the coefficient of friction between the slit plate and the shaft. It is fine as long as it is something. This is because the frictional force that balances the radial deformation of the elastic member is that of the holding plate and the slit plate, so if the frictional force of the holding plate is large, the radial deformation will be released by sliding between the slit plate and the shaft. , and the desired effect cannot be obtained. Also,
It goes without saying that the other parts of the position detection device may be of any function.

Effects of the Invention As described above, the present invention simplifies the work of centering the slit plate and the shaft by causing the elastic member to press the slit plate via the holding plate, and eliminates misalignment due to return after adjustment, making it more reliable. , a highly accurate position detection device can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a cross-sectional view of a main part of a position detecting device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of a first example of a conventional position detecting device, and FIG. FIG. 2 is a sectional view of a main part of a second example of a conventional position detection device. 1... shaft, 2... slit plate, 6...
...Elastic member, 7... Presser plate.

Claims (3)

[Claims] (1) In a position detection device that includes a slit plate fixed to a rotatable shaft between a light source and a photodetector, and detects the rotation angle of the slit plate, an elastic member is inserted into the slit via a holding plate. A position detection device characterized by pressing in the axial direction around a plate. (2) The position detection device according to claim 1, wherein the support portion of the elastic member and the shaft are fixed so that the amount of deformation of the elastic member is constant or within a predetermined range. (3) The position detection device according to claim 1, wherein the frictional force between the slit plate and the holding plate is smaller than or equal to the frictional force between the shaft and the slit plate.