JPH04250Y2 - - Google Patents

Description

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

(Prior art) In order to perform closed-loop control in the position control of hydraulic equipment, a sensor is required to detect the position of the actuator. (See page 679.) Therefore, various sensors such as potentiometers are employed, and some of these sensors are directly attached to fluid pressure (for example, oil pressure) cylinders. To explain this based on FIG. 2A, a scale (magnetic scale) is created by embedding magnetic material continuously at equal intervals in the rod axis direction (horizontal direction in the figure) on the circumferential surface 2A of the piston rod.
4 is composed. A main sensor 6 made of a magnetoresistive element is fitted into a sensor mounting hole 1A formed in the cylinder housing 1, and is disposed facing the scale 4 while maintaining a predetermined distance therebetween.
Here, as the piston rod 2 moves, the magnetic flux changes every time one magnetic body crosses the main sensor 6, so that the main sensor 6 outputs an AC waveform as shown in FIG.

Then, by converting this sensor output into a rectangular wave (pulse) using a comparator and counting the rise or fall of the pulse, the stroke (movement amount) of the rod 2 can be determined. This is because one cycle of the AC waveform corresponds to the movement of one magnetic body.

However, since the combination of the main sensor 6 and scale 4 can only measure the stroke, it is necessary to detect the reference position in order to know the rod position. For this purpose, a reference point scale 5 and a reference point sensor 7 arranged opposite thereto are provided.
Its configuration is similar to the relationship between the scale 4 and the sensor 6.

Note that 3 is a bearing that slidably supports the rod 2, 8 is a clevis, and 9 is a shaft hole.

(Problem to be solved by the invention) By the way, due to the structure of such a cylinder, when there is a change in the distance between the sensor detection surface 6A and the rod outer peripheral surface 2A, the amplitude and amplitude center value of the sensor output will change. have. This situation is shown in Figure 3. The output waveform when the interval value g is the minimum value gmin has a large amplitude, but when g is the maximum value
When gmax is reached, the output amplitude is small and the center value of the amplitude is also moving upward. Therefore, in order to obtain stable output, high accuracy is required for the interval values.

On the other hand, when installing a specific sensor,
For example, after machining a cylindrical cylinder housing, a stepped sensor mounting hole 1A is cut using a drill or the like to match the outer shape of the stepped sensor. Therefore, the accuracy in drilling directly determines the spacing accuracy. For example, in Fig. 2B, the height of the sensor small diameter portion 6B is H _S , the height from the housing outer circumferential surface 1B to the rod outer circumferential surface 2A is H _l , and the height to the stepped portion of the sensor mounting hole 1A is H ₃ , then g=H _l −(H ₃ +H _S ). Here,
This is because the accuracy of the housing dimension H _l and sensor dimension H _S can be expected to a considerable degree in terms of accuracy, so the accuracy of the stepped hole dimension H ₃ directly affects the interval accuracy.

However, it is quite difficult to control the stepped hole dimension _H3 with high precision in terms of manufacturing. This is because the stricter the accuracy control, the higher the cost. For this reason, the stepped hole machining becomes a factor that fluctuates the sensor output, resulting in a decrease in stroke detection accuracy and reliability.

This idea was made by focusing on the problems of the conventional method, and instead of using stepped processing, it added a wear-resistant member that makes sliding contact with the piston rod, and fixed the sensor body to this member. Among other things, the object is to provide a device that manages spacing.

(Means for solving the problem) A sensor installation in which a scale is provided in the direction of the outer circumferential axis of the piston rod, and a sensor body is formed in the cylinder housing side in the radial direction to face the scale and detect the stroke position of the piston rod. In a cylinder with a built-in stroke sensor fitted into a hole, a wear-resistant cylindrical member protruding from the sensor detection surface is loosely fitted between the sensor mounting hole and the sensor body, and this is rotated relative to the cylinder housing. The cylindrical member is slidably attached to the outer peripheral surface of the piston rod.

(Function) With this configuration, the distance between the sensor detection surface and the outer peripheral surface of the rod is determined only by the dimensions of the cylindrical member and the sensor body. Here, since not only the sensor body but also the newly added cylindrical member is a separate member from the cylinder housing, dimensional control becomes easy. As a result, the interval value can be easily and reliably secured with high precision, thereby providing stable sensor performance.

In addition, since the sensor body and the cylindrical member are free to rotate relative to each other, uneven wear of the cylindrical member due to the rotation of the cylindrical member that contacts the outer peripheral surface of the piston rod is prevented, and regardless of the rotation of the cylindrical member, Since the sensor body is not forced to rotate, problems such as wire breakage do not occur.

Examples of this invention will be described below.

(Example) As shown in FIG. 1A, in this invention, a sensor detection surface 6
Attach a cylindrical member 11 made of wear-resistant material (such as Teflon or brass) that protrudes beyond A,
This cylindrical member 11 is configured to be brought into sliding contact with the rod outer peripheral surface 2A via an elastic member. Specifically, a step is formed on the inner periphery of the cylindrical member 11 to match the outer shape of the sensor (the small diameter portion 6B and the large diameter portion 6C), and the relative relationship between the sensor 6 and the cylindrical member 11 is determined by the butt of the stepped portion. Determine the position. for example,
If the stepped height of the cylindrical member 11 is H _B and the stepped height of the sensor 6 is H _S , the height at which the cylindrical member 11 protrudes beyond the sensor surface 6A is the difference between these (H _B − H _S ). In addition, in this example, the sensor mounting hole 1A is a right circular column-shaped through hole that fits loosely into the cylindrical member 11, to the extent that the piston rod 2 and the cylindrical member 11 can slide.
The upper surface of the sensor 6 and the protrusion 11A of the cylindrical member are lightly pressed against the outer peripheral surface 2A of the rod via a ring-shaped member 12 made of an elastic body (for example, a spring or rubber). Further, the cylindrical member 11 is also loosely fitted to the sensor 6 and is rotatable relative to the sensor 6.

FIG. 1C shows another embodiment in which a cylindrical member 11a having no stepped portion is fitted into the sensor small diameter portion 6B, and the upper surface of the sensor 6 is pressed against the ring-shaped member 12.

In addition, in order to clarify the shape of the protrusion 11A, Fig. 1B is a diagram developed by expanding Fig. 1A at 90 degrees around the sensor axis. Therefore, its shape is also curved.

Therefore, with this configuration, the distance between the sensor detection surface 6A and the rod outer peripheral surface 2A is equal to the dimension related to the sensor 6 and the cylindrical member 11, that is, H _S
- Defined in H _B. Here, since both 6 and 11 are separate members from the cylinder housing 1, dimensional control becomes easier, unlike the case where the stepped holes are machined again after the housing is formed. For this reason,
Since the dimensional accuracy of these members 6, 11 directly becomes the spacing accuracy, a predetermined spacing can be easily, reliably, and accurately secured. Moreover, since it is only lightly contacted with the rod 2 via the elastic body 12,
Even if the rod 2 is deflected due to load fluctuations, this is absorbed and is not affected by the sensor scale interval.

Further, in this example, since the sensor mounting hole 1A is a mere through hole, it has no effect on the spacing accuracy. For this reason, hole machining is also easier.

Further, the cylindrical member 11 rests on the rod 2 in a saddle-like manner and is in a stable state against rotation. Here, when the sensor 6 rotates, the relative position between the sensor sensing part and the scale may shift, or the sensor 6 may
However, this example prevents the wiring from becoming twisted.

Incidentally, since the cylindrical member 11 slides between the rod 2 and the rod 2, the problem of wear occurs, but this problem is solved by constructing the cylindrical member 11 from a wear-resistant material. Further, since the cylindrical member 11 is rotatable relative to the sensor 6 and the cylinder housing 1, it can be provided with a function of preventing uneven wear by rotating itself.

Here, we have explained the case where the main sensor or reference point sensor is configured with a magnetoresistive sensor, but it can also be applied to sensors whose sensor output is affected by changes in the distance between the sensor body and the scale. Needless to say, it can be done.

(Effects of the invention) As explained above, in this invention, a wear-resistant cylindrical member is attached to the sensor body that protrudes beyond the sensor detection surface, and this cylindrical member is brought into light contact with the outer peripheral surface of the piston rod. Therefore, the present invention relates to a cylindrical member and a sensor body that allow easy dimension control of the distance between the sensor detection surface and the outer peripheral surface of the rod. It can be determined only by the dimensions, and stable sensor performance can thereby be obtained.

Furthermore, since the piston rod is brought into light contact through the elastic member, even if the piston rod is deflected due to load fluctuations, a constant distance can always be maintained between the piston rod and the sensor.

Furthermore, since the cylindrical member is supported so as to be rotatable relative to the sensor, it is possible to prevent rotation of the sensor and the accompanying twisting and disconnection of the wiring. It is also possible to prevent uneven wear by capturing active rotation.

[Brief explanation of the drawing]

FIG. 1A is a sectional view of a main part showing an embodiment of this invention, and FIG. 1B is a sectional view of FIG. 1A developed by 90 degrees. FIG. 1C is a sectional view showing another embodiment. Figure 2A is a sectional view of the conventional example, and Figure 2B is the sectional view of the second example.
FIG. 3 is a sectional view taken along the line II in FIG. A and a waveform diagram of the sensor output. 1...Cylinder housing, 1A...Sensor mounting hole, 2...Piston rod, 2A...Outer circumferential surface, 4...Magnetic scale, 5...Reference point scale, 6...Sensor body, 6A...Detection surface, 6B …
...Small diameter part, 6C...Large diameter part, 7...Reference point sensor, 11...Cylindrical member, 11A...Protrusion part, 1
2...Ring-shaped member.

Claims (1)

[Scope of utility model registration request] A cylinder with a built-in stroke sensor, in which a scale is provided in the direction of the outer circumferential axis of the piston rod, and a sensor body that faces the scale and detects the stroke position of the piston rod is fitted into a sensor mounting hole formed in the radial direction on the cylinder housing side. A wear-resistant cylindrical member that protrudes beyond the sensor detection surface is loosely fitted between the sensor mounting hole and the sensor body, and is mounted so as to be rotatable relative to the cylinder housing, and this cylindrical member is attached to the piston rod. A cylinder with a built-in stroke sensor, characterized in that the cylinder is brought into sliding contact with the outer peripheral surface of the cylinder.