JPH0329606Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a servo cylinder capable of measuring the amount of movement of a piston rod.

[Conventional technology]

Measuring the amount of movement of the piston rod of a fluid pressure cylinder (piston feed amount) to perform servo
This cylinder is indispensable for operating robots or machines that require complex and precise movements.

Conventionally, a system has been proposed in which an optical or magnetic digital scale or the like is moved together with the cylinder to read the piston feed amount and feed back to the piston drive unit to control the cylinder.

However, in this method, when moving the scale together with the piston of the cylinder, the scale was conventionally attached to the outside of the cylinder, which made the external shape of the cylinder with the scale large and complicated, making it difficult to handle. was.

Therefore, in order to eliminate such drawbacks, in recent years, as shown in FIGS. 4 and 5, a piston b is housed in the cylinder body a so as to be movable in the axial direction, and is integrally attached to the piston b. A hole d is drilled in the axial center of the piston rod c from one end of the rod c, and a flat magnetic scale e is inserted and fixed into the hole d, and a detection head (scale reading A support pipe g having a head (head) f is inserted into the hole d eccentrically from the axis of the hole d, and the end portion of the support pipe g is fixed to the cylinder body a side, and the piston b The movement of the magnetic scale e causes the magnetic scale e to move together with the piston rod c, whereas the detection head f does not move. Therefore, the detection head f and the magnetic scale e move relative to each other by the same amount of displacement as the displacement of the piston rod c, and the support pipe A configuration is proposed in which the detection head f reads the displacement amount of the piston b via the detection cable (signal line) h of the detection head f passed through the cylinder g, and feeds it back to the cylinder drive unit to control the cylinder. (Japanese Patent Application Laid-Open No. 58-225205).

[Problem that the invention attempts to solve]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 58-225205, a flat magnetic scale e is fixed in the hole d provided in the axial center of the piston rod c near the axial center of the hole d. Since the detection head f facing the magnetic scale e is supported by the support pipe g located off the axis of the hole d,
If the detection head f correctly faces the magnetic scale e, there will be no problem in detection, but if the piston rod c rotates in its circumferential direction during cylinder operation or during initial setting, the conventional flat magnetic scale e Then, there was a problem that the relative positional relationship with the detection head f was immediately destroyed, and the detection head f could no longer perform its detection function.

Therefore, the present invention has been devised to ensure that the detection function can always be maintained normally even if the relative position between the magnetic scale and the detection head shifts due to the rotation of the easily rotatable piston rod.

[Means for solving problems]

In this invention, a hole is drilled in the axial center of the piston rod which is movably housed in the cylinder body, a magnetic scale is attached to the hole, and the scale is fixed to the cylinder body and inserted into the hole. In a servo cylinder capable of detecting displacement occurring between a detection head and a rod, a magnetic scale mounted in the hole is mounted on the inner surface of the hole with a cross section having an arc shape along the inner surface of the hole, and the detection head is mounted on the inner surface of the hole. The structure is such that it is located on the axis of the hole.

[Effect]

In the present invention, lines of magnetic force coming out of a magnetic scale with an arcuate cross section are concentrated at the center of the arc, a strong magnetic field is formed at the axis of the hole, and the lines of magnetic force are further enhanced by the detection head located on the axis of the hole. Accurate capture and always accurate detection.

Furthermore, when using a conventional directional detection head, if the relative position of the magnetic scale and the detection head shifts in the rotational direction due to the rotation of the piston rod, the detection function cannot be maintained. Then, the magnetic scale also rotates, but since the magnetic scale has an arc shape with a radius centered on the axis of the hole, its relative position with the detection head does not change, and normal detection function can be maintained.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

1 and 2 show an embodiment of the present invention, in which a rod 3 of a piston 2 movably housed in a cylinder body 1 is slidably protruded from one end of the cylinder body 1, A head flange 4 is detachably attached to the other end of the cylinder body 1. The pressure chamber 2a on the head side of the piston 2 is made thinner on the inside than on the outside in the radial direction.
At the same time, at the axial center of the piston 2 and the piston rod 3 integrated with the piston 2,
A hole 5 is drilled from the piston head side to near the tip of the piston rod 3, and a semi-cylindrical magnetic scale 6 whose inner surface has the same radius from the axis of the hole 5 is inserted into the hole 5 over the entire length of the hole 5. Wear it over a period of time.
In addition, a support pipe 8 whose tip supports the detection head 7 and whose end is attached to the head flange 4 by screwing or the like is inserted into the hole 5, and the detection head 7 is aligned with the axis of the hole 5. position. On the pressure chamber 2a side of the piston 2, a magnetic scale 6 mounted in the hole 5 is held down and fixed, and a support pipe 8 is provided.
Seal flange 1 penetrated through seal material 9 through
0 is attached to the piston 2 with bolts 11 and the like, and the detection cable 12 of the detection head 7 is passed through the support pipe 8 and led out from the support pipe 8 to the outside of the head flange 4.

The structure of the magnetic scale 6 is based on Japanese Patent Application Laid-Open No. 1986-
Similar to that disclosed in No. 225205, S poles and N poles were arranged alternately at appropriate intervals in the longitudinal direction between the outer ferromagnetic scale base and the inner non-magnetic cover for protecting the rubber magnet. shall be taken as a thing. 13 is a fluid inlet/outlet to the head side pressure chamber 2a, and 14 is a fluid inlet/outlet to the rod side pressure chamber 2b.

When fluid is supplied and discharged from the inlet/outlet 13 or 14,
A piston 2 can move left and right within the cylinder body 1. As the piston 2 moves, the piston rod 3 also moves simultaneously and is displaced relative to the cylinder body 1. A magnetic scale 6 is installed in the hole 5 of the cylinder rod 3, and on the other hand, the detection head 7 inserted into the hole 5 is fixed to the cylinder body 1 side, so the magnetic scale 6 and the detection head 7 are relative to each other. The cylinder moves with the same amount of displacement as the displacement of the piston rod 3, and by detecting this displacement with the detection head 7, the amount of displacement of the piston 2 can be known, and the operation of the cylinder can be controlled based on this detection signal. . Moreover, since the magnetic scale 6 has a semi-cylindrical shape, the lines of magnetic force coming out of the magnetic scale 6 are concentrated at the center of the semi-cylinder, and a strong magnetic field is formed at the axial center of the hole 5. The positioned detection head 7 can more accurately capture the lines of magnetic force, so that accurate detection can be performed at all times.

When moving the piston 2 and detecting the amount of displacement of the piston as described above, if the piston 2 is displaced relative to the cylinder body 1 in the circumferential direction,
At the same time, the magnetic scale 6 also rotates, for example, to the state shown in FIG. It does not change and can always be detected under the same conditions.

Although the above embodiment shows the case where the magnetic scale 6 has a semi-cylindrical shape, it is not limited to a semi-cylindrical shape, and when the piston rod 3 rotates, its relative position with the detection head 7 shifts in the rotation direction. However, it is sufficient that the detection head can correctly face the magnetic scale 6, and the width may be smaller than the semi-cylindrical shape.

[Effect of idea]

As described above, according to the servo cylinder of the present invention, the lines of magnetic force coming out of the magnetic scale having an arc-shaped cross section are concentrated at the center of the arc, so a strong magnetic field is formed at the axial center of the hole, and The magnetic field lines can be captured more accurately by the detection head located at the top of the scale, and accurate detection can be performed at all times. However, it can be detected normally without any problems, and there is no possibility that it will become undetectable. This excellent effect can be achieved, and since the magnetic scale can be isolated from the working fluid by installing a seal plate as in the embodiment, it can be used regardless of the type of working fluid.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the servo cylinder of the present invention.
Fig. 2 is a sectional view of Fig. 1, Fig. 3 is a view corresponding to Fig. 2 showing the state when the piston rod rotates, Fig. 4 is a sectional view of a conventional servo cylinder, and Fig. 5 is a sectional view of the conventional servo cylinder. FIG. 4 is a cross-sectional view of FIG. 1 is a cylinder body, 2 is a piston, 3 is a piston rod, 5 is a hole, 6 is a magnetic scale, 7 is a detection head, 8 is a support pipe, and 12 is a detection cable.

Claims (1)

[Scope of utility model registration request] A hole is provided in the axial center of the piston rod integrated with the piston in the cylinder body, a magnetic scale is mounted in the hole, a detection head fixed to the cylinder body is inserted into the hole, and the magnetic scale and detection head are connected. In a servo cylinder in which the amount of displacement of the piston can be detected by the relative displacement in the direction of the axis of the hole, the magnetic scale has an arc-shaped cross section along the inner surface of the hole, and the arc has the same radius centered on the axis of the hole. A servo cylinder characterized in that the detection head is located on the axis of the hole.