JPH04282003A - Hydraulic actuator - Google Patents

Abstract

PURPOSE:To apply a wide range of loads accurately to a hydraulic actuator. CONSTITUTION:There is provided to a rod 2 inserted to a cylinder 1 a large piston 3a and a small piston 3c which have different pressure bearing areas, and line valves 6a, 6c for line changeover use are fitted to pressure lines 5a, 5c respectively to connect the respective pistons 3a, 3c to a pressure pump 4, and at the same time, both side chambers of the large piston 3a and the small piston 3c are respectively communicated through balance valves 7a,7c.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to hydraulic actuators.

0002

[Prior Art] In a conventional hydraulic actuator, as shown in the schematic diagram of FIG. In this case, the pressure P applied to the hydraulic actuator is adjusted to the pressure receiving area A of the piston 3 so that P=F/A. Therefore, in this hydraulic actuator, if the maximum pressure of the pressure line 5 of the pressure pump 4 is Pmax, the maximum load Fmax
It is possible to apply a load up to (=Pmax x A).

However, in such a hydraulic actuator, when a load smaller than the maximum load Fmax that can be applied is applied, the pressure P in the pressure line 5 is
Therefore, the pressure control accuracy decreases for small pressures, and the accuracy of the applied load also decreases. Furthermore, in order to ensure accuracy, it is necessary to change to a hydraulic actuator with a piston that has a small pressure receiving area, which is a rather troublesome task.

0004

SUMMARY OF THE INVENTION The present invention was proposed in view of the above circumstances, and an object of the present invention is to provide a hydraulic actuator that can accurately apply a wide range of loads.

[0005]

[Means for Solving the Problems] To this end, the present invention provides a plurality of pistons with different pressure receiving areas provided on a rod inserted into a cylinder of a hydraulic actuator, and a pressure line connecting each of the pistons and a pressure pump. The piston is characterized by being equipped with a line switching valve and a load hydraulic pressure balance valve on both sides of the piston.

[0006]

[Operation] In the hydraulic actuator of the present invention, the maximum load that can be applied to pistons having different pressure receiving areas can be set by multiplying the maximum pressure of the pressure line by the pressure receiving area. Among the pistons that have a maximum load exceeding the load to be applied, the piston with the smallest pressure receiving area is used by switching the pressure line. Therefore, if the load is adjusted by pressure control, the load can be applied with high precision, and a wide range of loads can be applied with high precision.

[0007]

[Embodiment] An embodiment of the hydraulic actuator of the present invention will be explained with reference to the drawings. Fig. 1 shows a first embodiment;
A) is a schematic diagram of the device when using a large piston, and (B) is the same diagram.
is a schematic diagram of the device when a small piston is used, FIG. 2 is a vertical cross-sectional view of the cylinder when a friction reduction mechanism is installed in the same as above, FIG. 3 is a second embodiment, and FIG. 3A is a schematic diagram of the device , the same figure (B) is an explanatory diagram of the valve opening/closing operation, and FIG. 4 is a diagram showing the load accuracy in the same.

First, in FIG. 1 of the first embodiment, a rod 2 inserted into a cylinder 1 of a hydraulic actuator has a large piston 3a with a pressure receiving area A1 and a large piston 3a with a pressure receiving area A3.
A small piston 3c is attached. Pressure lines 5a and 5c are connected from the pressure pump 4 outside the cylinder 1 to the pressure receiving sides of the large piston 3a and the small piston 3c.
, line valves 6a and 6 for line switching, respectively.
c is attached. Further, the chambers on both sides of the large piston 3a and the small piston 3c are provided with balance valves 7a and 7c, respectively.
communicated via. In the figure, each valve 6
The "o" marks on a, 6b, 7a, and 7c indicate the open state, and the "c"
” indicates the closed state.

In such a device, the maximum pressure of the pressure pump 4 is Pmax, pressure receiving area A1 > pressure receiving area A3.
When applying load F to rod 2, (Pma
In the case of x × A1 )>F>(Pmax ×A3), use the large piston 3a as shown in Fig. 1(A),
If (Pmax×A3)>F, a small piston 3c is used as shown in FIG. 1(B). As a result of these operations, if the pressure control accuracy is ΔP, then when pressure P is applied to the large piston 3a, the load accuracy becomes ΔP/P. If the load at this time is applied by the small piston 3c,
The pressure is A1 /A3 ・P, and the accuracy of the load is ΔP
/P·A3 /A1, and the load accuracy is improved.

In this device, as shown in FIG. 2, a roller bearing 8 is provided on the cylinder side at the point where the large piston 3a and the small piston 3c contact the cylinder 1.
If equipped with this roller bearing 8, the friction caused by increasing the number of pistons can be reduced, and a highly accurate load can be applied.

Next, in FIG. 3(A) of the second embodiment,
A rod 2 inserted into a cylinder 1 of a hydraulic actuator is attached with a large piston 3a having a pressure receiving area A1, a medium piston 3b having a pressure receiving area A2, and a small piston 3c having a pressure receiving area A3. Pressure lines 5a, 5b, 5c connected from the pressure pump 4 outside the cylinder 1 to the pressure receiving side of each piston 3a, 3b, 3c are provided with line valves 6a, 6b, 6c for line switching, respectively. Furthermore, each piston 3a. 3b. Both chambers 3c are communicated via balance valves 7a, 7b, and 7c, respectively. The opening and closing procedures for each valve 6a to 7c when using each piston 3a, 3b, and 3c are shown in Figure 3(B).
As shown.

[0012] The load application accuracy in such a device is as follows:
As shown in FIG. 4, load accuracy is improved by switching between the medium piston 3b and the small piston 3c, compared to the case where the entire load is applied by the large piston 3a alone. By increasing the number of pistons in this way, a wide range of loads can be applied with high accuracy.

[0013]

[Effects of the Invention] In short, according to the present invention, a plurality of pistons with different pressure receiving areas are provided on a rod inserted into a cylinder of a hydraulic actuator, and a pressure line is provided on a pressure line connecting each of the pistons and a pressure pump. The present invention is industrially extremely useful because it provides a hydraulic actuator that can accurately load a wide range of loads by providing a valve for line switching and a valve for balancing load and hydraulic pressure on both sides of the piston.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the hydraulic actuator of the present invention, and FIG. 1 (A) is a schematic diagram of the device when a large piston is used;
Figure (B) is a schematic diagram of the device when a small piston is used.

FIG. 2 is a longitudinal cross-sectional view of the cylinder when a friction reduction mechanism is provided in the same as above.

FIG. 3 shows a second embodiment; FIG. 3(A) is a schematic diagram of the device, and FIG. 3(B) is an explanatory diagram of the valve opening/closing operation.

FIG. 4 is a diagram showing load accuracy in the same as above.

FIG. 5 is a schematic diagram of a conventional hydraulic actuator.

[Explanation of symbols]

1 Cylinder 2 Rod 3a Large piston 3b Middle piston 3c small piston 4 Pressure pump 5a, 5b, 5c pressure line 6a, 6b, 6c line valve 7a, 7b, 7c Balance valve 8 Roller bearing

Claims (1)

[Claims] 1. A plurality of pistons with different pressure receiving areas provided on a rod inserted into a cylinder of a hydraulic actuator, and a line switching valve and piston provided in a pressure line connecting each of the pistons and a pressure pump. A hydraulic actuator characterized by comprising a valve for balancing load hydraulic pressure on both sides.