JPS5827121Y2 - Fluid pressure servo cylinder - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a fluid pressure servo cylinder that can directly control the position of a load in a linear direction in response to rotational input.

The conventional fluid pressure servo cylinder to be improved by this invention is the one shown in Fig. 1, which was proposed in Japanese Utility Model Publication No. 53-12939. The spool rotates smoothly in the valve chamber and moves smoothly in the linear direction, and there is less fluid leakage at the servo valve. In order to achieve this, special high precision is required for each part constituting the servo valve part and the cylinder part, and the assembly of these parts also requires a high degree of skill.

Hereinafter, a conventional fluid pressure servo cylinder and a fluid pressure servo cylinder of this invention will be described with reference to the drawings.

Figure 1 shows a conventional fluid pressure servo cylinder, with a 3-way servo valve (section V) and a cylinder (section C) as shown in the figure.
It is made up of.

As shown in the figure, the spool 1a of the three-way servo valve V has a threaded rod 1b on its left side, which protrudes into the cylinder C and is threadedly engaged with a Nand 3 attached to the piston 2.

The spool 1a and the threaded rod 1b are machined from a single material or made separately and combined into one body.

Therefore, when an input signal is applied to the pulse motor 4 (another servo motor or the like may be used) and it rotates, the rotation is transmitted to the spool 1a through the combination of gears 5 and 6.

When the spool 1a rotates, the spool 1a moves in the axial direction within the valve chamber 7 due to the threaded engagement between the threaded rod 1b and the Nand 3.

For example, when an input signal for clockwise rotation is given to the pulse motor 4, the spool 1a moves to the right, and when a signal for counterclockwise rotation is given to the pulse motor 4, the spool 1a moves to the left.

In the figure, the spool 1a is in the neutral position, and the land 1c is connected to the pressure fluid inflow path 8, outflow path 9, and discharge path 1.
0 are mutually isolated.

Therefore, in this state, even if pressure fluid is applied to the inflow path 8 from the pressure fluid supply source 11 through port P, no pressure fluid flows into the cylinder on the rond side from the supply source 11 through port B. Even if pressure fluid is applied to the chamber 12b, the fluid is not discharged, and the piston 2 remains stationary and does not move.

Since the pressure receiving area on the front side and the pressure receiving area on the head side of the piston 2 are selected at a ratio of approximately 1:2, the magnitude of the fluid pressure in the cylinder chamber 12b on the front side and the cylinder chamber 12a on the head side is approximately 2:2. :1, and the forces pushing the piston 2 from both sides are equal and balanced.

Now, if an input signal is applied to the pulse motor 4 and the spool 1a moves to the right, the gap between the inflow path 8 and the outflow path 9 will open, and the fluid pressure of the supply source 11 will flow into the cylinder chamber 12a on the head side. In addition, the pressure fluid flows into the cylinder chamber 12a, the pressure fluid in the cylinder chamber 12b is returned to the supply source 11 side, and the piston 2 moves to the left.

When the piston 2 moves to the left, the spool 1a also moves to the left because the threaded rod 1b is screwed into it, and when the spool 1a moves to the original neutral position, the piston 2
stands still.

Now, to explain the case where a pulse motor is used, the piston 2 moves by an amount proportional to the number of signal pulses applied to the pulse motor 4, and this moves the piston rod 1.
The position of the load connected to the threaded portion 13a at the left end of the screw 3 is controlled.

When a reverse rotation input signal is applied to the pulse motor 4 (a pulse with a reverse sign), the spool 1a rotates in the opposite direction and moves to the left.

At this time, the space between the outflow passage 9 and the discharge passage 100 is opened, the pressure oil in the cylinder chamber 12a is discharged from the port T to the tank 14 through the discharge passage 10, and the piston 2 flows from the supply source 11 into the cylinder chamber 12b. The piston 2 is moved to the right by the pressure fluid and comes to rest when the spool 1a returns to the neutral position as described above.

In this way, the position of the load is directly controlled in the linear direction by the rotation input signal to the pulse motor 4.

In this fluid pressure servo cylinder, in order to move the threaded rod 1b in the axial direction, the piston rod 13 is provided with a hollow portion 13b, as shown in the figure.
b communicates with the cylinder chamber 12a through a pore 3a provided in the NAND 3, and connects the cylinder chamber 12a and the hollow part 13b.
and are always at equal pressure.

Further, the cylinder chamber 12a is also communicated with an end chamber 16 on the right side of the spool 1a through an oil passage 15, and the end chamber 16 is always at the same pressure as the cylinder chamber 12a.

Therefore, the same fluid pressure is always applied to both end faces of the spool 1a in a balanced manner, so there is little resistance to the rotation and axial movement of the spool 1a, and the position of the load can be controlled with minute inputs. ing.

The above is an overview of the structure and function of a conventional fluid pressure servo cylinder.As explained earlier, in this fluid pressure servo cylinder, the spool 1a and the threaded rod 1b are integrated into one body, and this is a three-piece structure. It is located at the center of the directional servo valve (1) and the cylinder C, and is engaged with the two at three locations: the nut 3, the spool 1a, and the end chamber 16.

Among these, the part where the spool 1a fits into the valve chamber 7 is long, so that the rotation and axial sliding of this part are carried out smoothly with little resistance, and leakage within the valve device is reduced. In order to achieve this, the inner diameter of the valve chamber 7 and the outer diameter of the spool 1a must be machined with high precision, and when this fluid pressure servo cylinder is assembled, bending stress etc. must be applied to each part of the threaded rod 1b and spool 1a. Each fitting part must fit together in an extremely natural state without causing any damage.

That is, straightness of the threaded rod 1b, spool 1a, and valve chamber 7 is required, and in the assembled state, the center line of the internal thread of the piston 2, the center line of the valve chamber 7, and the end chamber 16 that holds the right end of the spool 1a are The center line must match.

For this purpose, parallelism with the reference plane, linearity, and positional accuracy are required in the machining of the valve chamber 7 and the end chamber 16, and each component of the cylinder C is also required to have high precision. Furthermore, when assembling these parts, it is necessary for a skilled person to be very careful so as not to cause bending stress on the threaded rod 1b and the spool 1a due to deviation of the above-mentioned center line.

Therefore, the object of this invention is to provide a fluid pressure servo cylinder that is easy to manufacture and can be mass-produced by solving the above-mentioned problems of the conventional fluid pressure servo cylinder.

For this reason, the present invention has developed a conventional hydraulic pressure cylinder that has a small diameter land and a large diameter land that fit into the inner holes of the small diameter part and the large diameter part of the servo valve body to form respective valve chambers. One part has a threaded part that protrudes into the hollow part of the piston rond that communicates with the cylinder chamber on the head side, and the other part is a rond that extends the diameter of the cast tonpa. a threaded rod that passes through the through hole of the spool without contact and whose tip end is coupled to the rotation input section, and a thrust bearing is fitted between the stopper and the end surface of the small diameter section of the spool. By making the difference in cross-sectional area between the large diameter part and the small diameter part of the valve chamber substantially equal to the cross-sectional area of the extended rond of the threaded rod, the spool and the threaded rod become separate bodies, and the difference in cross-sectional area of the spool is reduced. Since the fluid pressure applied to the rod and the fluid pressure applied to the cross-sectional area of the extension rod of the penetrating rod are in balance, the threaded rod can be easily rotated with a small input.

Next, the present invention will be explained using figures.

The structure of one embodiment is shown in FIG.

The figure shows a three-way servo valve in which the valve device part is the same as the conventional one in Figure 1, and since both operate as fluid pressure servo cylinders are the same, the main points are the differences in structure and the operation of that part. The explanation will focus on

In this fluid pressure servo cylinder, as shown in the figure, the valve chamber provided in the center of the main body 29 of the three-way servo valve V' has two stages, a small diameter part 18 and a large diameter part 1902, which communicate concentrically. The difference in cross-sectional area between the two is exactly equal to the cross-sectional area of the extension iron 20a of the threaded rod 20.

As shown in the figure, the spool 21 has a hollow shape with a through hole 30 and is separate from the threaded rod 20 and its extension rod 20a.
There is a part that fits into the valve chamber and slides in the axial direction within the valve chamber.

The small diameter land 21a and the large diameter land 21b are the small diameter portion 18.
and is positioned approximately at the center of the spool 21, fitting with the large diameter portion 19.

The leftward movement of the spool 21 is stopped via a thrust bearing 22 by a stopper 20b provided at the base of the extension iron 21a.

The extension rod 20a is rotatably held at the end plate 23 of the valve chamber, and is rotatably coupled to the pulse motor 4 through gears 25 and 26 within a gear chamber 24 outside the end plate 23.

Note that a spring 27 is attached to the through hole 30 of the spool 210 so as to push the spool 21 to the left.

The barrel 31 of the cylinder C is fluid-tightly connected to the main body 29 of the valve device, and its structure is the same as that in FIG. 1, so a description thereof will be omitted.

In such a structure, the cylinder chamber 1 on the head side is now
If fluid pressure is applied to 2a, this fluid pressure passes through the gap in the thrust bearing 22 and is applied to the oil chamber 28 on the right side of the spool 21.

Therefore, the spool 21 is pushed to the left by the fluid pressure applied to the area (hereinafter referred to as annular area) obtained by subtracting the area of a circle whose diameter is the diameter of the small diameter part from the area of the circle whose diameter is the diameter of the large diameter part. This force is applied to the stopper 20b via the thrust bearing 22 and acts as a force pushing the threaded rod 20 to the left.

On the other hand, the fluid pressure in the cylinder chamber 12a is
The extension iron 20a joins the hollow part 13b of the piston iron 13 through the through hole 3 of the spool 21.
0, penetrates the bearing hole 32 of the end plate 23, and protrudes into the gear chamber 24 under normal pressure. ) is being pushed directly to the right by the fluid pressure.

Therefore, equal forces are applied to the screw rod 20 to push it to the right and to the left, and these forces are stopped by the thrust bearing 22, and the screw rod 20
The forces due to fluid pressure acting on are balanced.

Therefore, the threaded rod 20 can be easily rotated with a small input.

The spring 27 always presses the spool 21 to the left, thereby preventing the spool 21 from making any mechanical movement when starting this fluid pressure servo cylinder.

In addition, when the force due to the fluid pressure acting on the threaded rod 20 is completely balanced, the pressing force by the spring 27 is stopped at the threaded portion of the threaded rod 20 and the tonnant 3. Even if there is a bank crash in the screw joint, this pushing force will always ensure that the screws are connected on one side of the threaded surface, thereby preventing the positioning accuracy of the fluid pressure servo cylinder from being degraded by the puncture of the screw joint. It is fulfilling its role.

Above, we have compared the fluid pressure servo cylinder of this invention with the conventional fluid pressure servo cylinder and mainly explained the differences in structure and the operation of those parts, but the operation of the fluid pressure servo cylinder is completely different between the two. do not have.

That is, when rotation input is given to the pulse motor 4,
Through gears 26,25 the threaded rod 20 is rotated to move it in the axial direction.

In this case, the spool 21 is always held close to the stopper 20 of the threaded rod 20 by the fluid pressure and the spring 27 as described above.
b, so that it moves in the axial direction following the movement of the threaded rod 20, and the function of the valve device is completely the same as that of the conventional valve device shown in FIG.

As is clear from the above description, in the fluid pressure servo cylinder of this invention, the spool 21 and the threaded rod 20 are separate bodies, and the threaded rod 20 is screwed into the Nand 3 at the left end, and at the right end. It is supported by the end plate 23 of the valve chamber, and is held by a thrust bearing 22 in the middle.

Among these, since the thrust bearing 22 has some margin in the radial direction in the intermediate thrust bearing 220 portion, the accuracy of the center line in this portion is not required so much.

In ball bearings, the diameter of the race groove is generally larger than the diameter of the ball, so thrust bearings have some leeway in the radial direction, and flat race thrust bearings without grooves or needle thrust bearings are used. This further increases the tolerance to radial movement.

Therefore, in this structure, the only problem is the eccentricity accuracy of the threaded part of the threaded rod 20 and the NAND 3, and the fitted part of the extended rond part 20a and the end plate 23. Since the absorption is carried out at the bearing 220 portion, the precision of this portion is not required to be as strict as compared to the conventional structure shown in FIG.

In other words, due to its structure, the fluid pressure servo cylinder of this invention can tolerate a considerable amount of overall eccentricity after assembly, eliminating the need for skilled personnel to spend time on assembly, and also improving the precision of each component that makes up the device. may also be considerably lower than conventional ones.

In the embodiment shown in Fig. 2, a three-way servo valve is used as the valve device, but a four-way servo valve as shown in Fig. 3 can be manufactured in the same manner. Wear.

In this case, when the spool 21' is moved to the right by the input signal, pressure fluid flows from the supply source 11 through the boat A into the Henlo's cylinder chamber 12a, and at the same time, the fluid in the cylinder chamber 12b on the rond side flows. When the spool 21' is moved to the left, the pressure fluid flows into the cylinder chamber 12b on the rond side, and at the same time, the fluid in the cylinder chamber 12a on the head side flows into the tank 14 from the port B through the port T. 14, the maximum thrust, especially the cylinder thrust force, is approximately twice that of the three-way servo valve shown in FIG.

In FIG. 3, components that are the same as those in FIG. 2 are given the same numbers, and components that have the same function but have a slightly different shape are shown with the same numbers and a dash.

In addition, in the embodiments shown in FIGS. 2 and 3, the threaded rod 20
The spring 27 or 27' is used in order to eliminate the effect of bank lash at the threaded part of the piston 2 with the nut 3 and to eliminate impact noise during pressurization, but this does not affect cylinder positioning accuracy. If high precision is not required, these springs may be omitted and fluid pressure may be supplied gradually during use, and these springs are not necessarily necessary.

As explained above, the fluid pressure servo cylinder of this invention is an improvement on the conventional fluid pressure servo cylinder proposed in Publication of Utility Model Publication No. 53-12959. This has the effect of reducing the required accuracy of each component constituting the fluid pressure servo cylinder and eliminating the need for skilled workers for assembly, thereby providing a fluid pressure servo cylinder that is easy to manufacture and can be mass-produced.

[Brief explanation of the drawing]

Figure 1 is a structural diagram of a conventional fluid pressure servo cylinder, Figures 2 and 3 are structural diagrams of an embodiment of the fluid pressure servo cylinder of this invention, and Figure 2 is a three-way servo valve. is for a four-way servo valve. 2... Piston, 3... Nando's, 4.
...Pulse motor, 11...Fluid pressure supply source, 12a...Cylinder chamber on the head side, 12
b... Cylinder chamber of Ron Hit 1j, 13...
-, -Rondo, 14...Tank, 18°19.
... Valve chamber, 20 ... Threaded rod, 21 ...
...Spool, 22...Thrust hair ring,
25, 26...Gear, 27...Spring.

Claims (1)

[Scope of utility model registration request] A servo valve and a cylinder are assembled together, and the spool of the servo valve slides in the axial direction to switch the flow path of the pressure fluid to the cylinder, and the servo valve is switched by a threaded rod screwed into the piston of the cylinder. In a fluid pressure servo cylinder in which rotational input to a valve is converted into axial movement of a spool to control the position of a piston, each valve is fitted into the inner holes of the small diameter part and the large diameter part of the servo valve body. A hollow spool with a small-diameter land and a large-diameter land forming a chamber and a through hole in the center, and a hollow part of the piston rond whose one part with a threaded part communicates with the cylinder chamber on the head side. a threaded rod, the other protruding portion of which extends through the stopper and extends through the through hole of the spool in a non-contact manner, the tip of which is connected to the rotation input portion; A fluid characterized in that a thrust bearing is fitted between the end face of the small diameter part, and the difference in cross-sectional area between the large-diameter part and the small-diameter part of the valve chamber is approximately equal to the cross-sectional area of the extended rond of the threaded rod. Pressure servo cylinder.