JPH0349285Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a fluid pressure cylinder incorporating a stroke sensor.

(Prior art) In order to detect the operating stroke amount of a hydraulic cylinder, etc., as shown in Fig. 2A and B,
Some devices measure the stroke position of a piston rod using a magnetic resistance sensor or the like.

A piston rod 2 of a hydraulic cylinder 1 is slidably supported by a bearing 3.

The piston rod 2 is provided with a displacement scale 4 that is continuously arranged at predetermined distance intervals on one side, and a reference point scale 5 that is arranged on the other side to represent a reference point.

A main sensor 6 and a reference point sensor 7, which are composed of a magnetic resistance sensor or the like, are arranged in the hydraulic cylinder 1 so as to face each of the scales 4 and 5.

When the piston rod 2 moves, the main sensor 6 produces a waveform (sine curve) output as shown in FIG.

The sensor output is maximum at the position closest to each scale, so the maximum value is when the scale is directly below (directly above) the sensor, and the minimum value is when the scale is located between adjacent scales.

(Problem that the invention aims to solve) By the way, when the air gap g between each sensor and the scale changes, the output when the gap is large (gmax) is smaller than when the gap is small (gmin). When the sensor output is compared with a predetermined level using a comparator, the pulse width appears as a fluctuation in the output.

In the case where a clevis (rod head) 8 is provided to connect the piston rod 2 to a load, the design is such that an external lateral load acts from a direction perpendicular to the shaft hole 9 of the clevis 8.

However, when the sensors 6, 7 and scales 4, 5 are arranged in the direction of lateral load as shown in Fig. 2, when the piston slides while receiving the lateral load, the bearing 3 will wear unevenly in the direction of the load. Therefore, a non-negligible gap (gd) occurs between the piston rod 2 and the bearing 3.

In this state, the air gap g between the sensor and the scale fluctuates within a range of 2 gd due to the lateral load, resulting in fluctuations in the sensor output as shown in FIG. 3 above.

For this reason, detection accuracy and reliability as a stroke sensor have been reduced.

The present invention aims to solve such problems.

(Means for Solving the Problems) The present invention provides a cylinder with a built-in stroke sensor in which scales are arranged at predetermined intervals in the direction of the outer circumferential axis of the piston rod, and a sensor is attached to the cylinder facing the scales. The center of the shaft hole formed in the scale is set to be approximately parallel to the direction of the air gap between the scale and the sensor.

(Function) The external lateral load on the piston rod is
Even if it acts in a direction perpendicular to the shaft hole of the clevis and causes uneven wear of the bearing, the fluctuation in the air gap between the sensor and the scale is so small that it can be ignored. Therefore, fluctuations in sensor output can be suppressed.

(Example) Hereinafter, an example of the present invention will be described based on FIG. 1.

As shown in FIG. 1A, in the present invention, the axial direction of the shaft hole 9 of the clevis 8 formed at the tip of the piston rod 2 is aligned with the main sensor 6 and the scale 4, and the reference point sensor 7 and the scale 5. It is set so that it is approximately parallel to the scale width center line M connecting the facing points, and the external lateral load Fd acting on the piston rod 2 is applied from a direction approximately perpendicular to the air gap direction between the sensor and the scale.

In this way, as shown in Figure 1B,
Due to the action of the lateral load Fd, the bearing 3 that slides and supports the piston rod 2 wears unevenly, causing the gap
Even if gd occurs, this gap gd will not affect the air gaps g between the main sensor 6 and scale 4, as well as between the reference point sensor 7 and scale 5.

Since the external lateral load Fd applied to the piston rod 2 acts in a direction orthogonal to the shaft hole 9 of the clevis 8, the uneven wear that occurs on the bearing 3 is noticeable in the direction of this load, and there is less uneven wear in the direction orthogonal to the lateral load. . Therefore, the air gap variation between the sensor and scale caused by the gap gd due to uneven wear is so small that it can be ignored.

As a result, the output fluctuation as shown in FIG. 3 described above does not occur, and stable stroke position detection accuracy is maintained over a long period of time.

In this example, the sensor was explained as a magnetoresistive sensor, but it is clear that the present invention is effective for all sensors whose sensor output amplitude and amplitude center value vary due to air gap variation between the sensor and scale. Dew.

(Effects of the invention) As described above, the present invention can minimize the influence of the lateral load acting on the piston rod on the sensor output, maintain stable output characteristics even under poor usage conditions, and detect stroke position. accuracy,
Reliability can be improved.

[Brief explanation of the drawing]

FIG. 1A is a sectional view of a main part showing an embodiment of the present invention;
FIG. 1B is also a cross-sectional view taken along the line --. Figure 2A is a sectional view of the conventional example, and Figure 2B is its -
The line cross-sectional view and FIG. 3 are waveform diagrams similarly showing the sensor output characteristics of the conventional example. 1...Cylinder, 2...Piston rod, 3...
...Bearing, 4, 5...Scale, 6,7...
Sensor, 8... Clevis, 9... Shaft hole.

Claims (1)

[Scope of utility model registration request] In a cylinder with a built-in stroke sensor, in which scales are arranged at predetermined intervals along the outer axial direction of the piston rod, and a sensor is attached to the cylinder facing the scales, the center of the shaft hole formed at the tip of the piston rod is located between the scale and the sensor. A cylinder with a built-in stroke sensor, characterized in that it is set substantially parallel to the air gap direction.