JP2000298086A - Material tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material tester provided with a hydraulic circuit capable of controlling the hydraulic cylinder in the material tester simply and highly accurately. SOLUTION: A cylinder driving circuit is constituted by providing a load response type pressure reducing valve 7 operated corresponding to the oil pressure difference ΔP(=P1-P2) between the pressures before and behind a hydraulic servo valve 5 to adjust the oil pressure supplied to the hydraulic servo valve, between the hydraulic servo valve 5 driving a hydraulic cylinder 1 corresponding to the load applied to a test piece and the hydraulic pump 3 thereof. Further, a relief valve 8 for adjusting the oil pressure P0 supplied to the input side of the load responce type pressure reducing valve corresponding to the oil pressure P1 on the output side of the load response type pressure reducing valve is provided to a hydraulic source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material testing machine for performing a test such as compression, extension and fatigue by applying a load to a test piece via a hydraulic cylinder, and more particularly to a control of a hydraulic circuit for driving the hydraulic cylinder. The present invention relates to a material testing machine having improved simplicity and a simplified configuration.

[0002]

[Related Background Art] A material for applying a load to a test piece using a hydraulic cylinder, and testing the compression properties and extension properties of the test piece and the fatigue fracture strength from the relationship between the load applied to the test piece and the displacement. In a test machine, it is important to control the hydraulic cylinder with high accuracy. The hydraulic cylinder is driven by applying pressure oil supplied from a hydraulic pressure source to the hydraulic cylinder via a hydraulic servo valve, and controlling the operation (valve opening) of the hydraulic servo valve to control the hydraulic pressure (valve opening). Drive pressure), and thus the load pressure of the hydraulic cylinder. The control of the hydraulic servo valve is exclusively performed electrically by a servo amplifier provided as a feedback control system.

[0003]

In Japanese Utility Model Publication No. 7-52608, for example, a relief valve is provided in a primary line connecting a hydraulic source (hydraulic pump) and a hydraulic servo valve, and the relief valve is connected to a hydraulic valve. A technology is disclosed in which a hydraulic pressure difference before and after the hydraulic servo valve is maintained at a value equal to or less than a preset value by driving the hydraulic valve in accordance with a hydraulic pressure difference before and after the servo valve. According to such a hydraulic circuit, the hydraulic pressure difference before and after the hydraulic servo valve can be kept constant, so that the valve pressure drop at the hydraulic servo valve can be reduced, and the conversion to heat energy can be reduced.

However, since the pressure on the primary side of a hydraulic servo valve connected to a hydraulic source (hydraulic pump) for generating a high hydraulic pressure of about 210 kgf / cm ² is directly controlled by the relief valve, the Heavy load.
In addition, since the operation of the relief valve easily affects the hydraulic servo valve, there is a possibility that stable operation of the hydraulic servo valve is hindered.

The present invention has been made in view of such circumstances, and an object of the present invention is to control a hydraulic cylinder simply and with high accuracy without regard to the operating pressure (load pressure) of the hydraulic cylinder. It is an object of the present invention to provide a material testing machine provided with a hydraulic circuit that can be used.

[0006]

In order to achieve the above-mentioned object, a material testing machine according to the present invention comprises a hydraulic test apparatus comprising: a hydraulic servo valve for driving a hydraulic cylinder in accordance with a load applied to a test piece; A cylinder drive circuit is provided by providing a load-sensitive pressure reducing valve that operates in accordance with the hydraulic pressure difference before and after the hydraulic servo valve to adjust the hydraulic pressure supplied to the hydraulic servo valve. A relief valve is provided for adjusting the hydraulic pressure supplied from the hydraulic pressure source to the input side of the load-responsive pressure reducing valve in accordance with the hydraulic pressure at the output side of the pressure reducing valve.

That is, the present invention provides a load-sensitive pressure-reducing valve which operates in accordance with a hydraulic pressure difference before and after the hydraulic servo valve between the hydraulic servo valve and the hydraulic pressure source, so that the hydraulic servo valve and the hydraulic pressure source can be connected to each other. Preventing interference and providing a relief valve between the load-sensitive pressure-reducing valve and the hydraulic pressure source that operates according to the oil pressure on the output side of the load-sensitive pressure-reducing valve, thereby simplifying and effectively providing the hydraulic servo valve. The feature is to ensure stable operation of.

Further, according to the present invention, a plurality of cylinder drive circuits for driving a plurality of hydraulic cylinders are respectively supplied with hydraulic pressure from a common hydraulic source, and each of the plurality of cylinder drive circuits is provided with a load-sensitive circuit. According to the present invention, a relief circuit provided in a hydraulic pressure source is driven in accordance with the hydraulic pressure on the output side of the type pressure reducing valve to adjust the hydraulic pressure supplied to the input side of each load-sensitive type pressure reducing valve.

Preferably, the hydraulic pressure at the output side of each load-responsive pressure reducing valve is introduced via a check valve to drive the relief valve, so that the output side of each load-responsive pressure reducing valve has the highest output. The relief valve is operated according to the oil pressure to adjust the oil pressure supplied from the oil pressure source to the input side of each of the load-responsive pressure reducing valves.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hydraulic circuit in a material testing machine according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a hydraulic circuit in a material testing machine according to this embodiment. Reference numeral 1 denotes a hydraulic cylinder that is driven by receiving hydraulic pressure and applies a predetermined load to a test piece (not shown). By the operation of the hydraulic cylinder 1, a load consisting of a load or a displacement is applied to the test piece, and tests such as compression and tensile strength and further bending strength are performed based on the relationship between the load value and the displacement value at that time.

The hydraulic cylinder 1 is basically driven by the hydraulic pump 3 and the filter 4 from the oil tank 2.
This is performed by adjusting the flow rate of pressure oil of a predetermined pressure supplied through the hydraulic cylinder 1 through the hydraulic servo valve 5 and supplying it to the hydraulic cylinder 1. In particular, the flow rate adjustment (pressure control) of the pressure oil by controlling the valve opening of the hydraulic servo valve 5 is electrically executed under the control of the controller 6. Note that the controller 6 is configured, for example, based on an error between a control target value and a load (operating pressure) obtained by a pressure sensor (not shown) incorporated in the hydraulic cylinder 1.
The operation of the hydraulic servo valve 5 is feedback-controlled to make the error zero.

The feature of this hydraulic circuit is that:
The point is that a load-sensitive pressure reducing valve 7 is provided between the primary side (input side) of the hydraulic servo valve 5 and the hydraulic pump 3 as its hydraulic pressure source. The load-responsive pressure reducing valve 7 serves to reduce the pressure oil supplied from the hydraulic pump 3, for example, about 210 kgf / cm ² , and supply the reduced pressure oil to the primary side of the hydraulic servo valve 5. In accordance with the secondary pressure P2 of the hydraulic servo valve 5 which is the load pressure of 1, the hydraulic servo valve 5
The secondary pressure P1 has a role of always being set to a pressure higher than the secondary pressure P2 by a constant pressure. The load-responsive pressure reducing valve 7 together with the hydraulic servo valve 5 constitutes a cylinder drive circuit for driving the hydraulic cylinder 1 with high accuracy and stability.

That is, the load-responsive pressure reducing valve 7 is connected to the primary side of the hydraulic servo valve 5 regardless of the load pressure P 2 of the hydraulic cylinder 1 and regardless of the pressure of the pressure oil supplied from the hydraulic pump 3. The pressure difference ΔP from the secondary side (= P1-P2)
For example, it functions so as to always keep it constant at about 5 to 10 kgf / cm ² . Specifically, the load-responsive pressure-reducing valve 7 has its valve opening adjusted in accordance with the primary pressure P1 of the hydraulic servo valve 5, and the secondary pressure P2 of the hydraulic servo valve 5, which is the pressure on the output side, is adjusted. A pressure regulating valve is provided which equilibrates when a predetermined pressure difference ΔP with respect to the primary pressure P1 is reached.

On the other hand, a relief valve 8 is provided in a pipe connecting the load-responsive pressure-reducing valve 7 and the hydraulic pump 3 as its hydraulic pressure source. The relief valve 8 basically operates according to the difference in oil pressure before and after the load-sensitive pressure-reducing valve 7, and particularly, the oil pressure at the output side of the load-sensitive pressure-reducing valve 7, that is, the hydraulic servo valve 5.
The hydraulic pump 3 operates in accordance with the primary pressure P1 supplied to the hydraulic pump 3 to relieve the pressure oil discharged from the hydraulic pump 3, and adjusts the hydraulic pressure Po supplied from the hydraulic pump 3 to the load-responsive pressure reducing valve 7. Specifically, the hydraulic pressure Po has a predetermined pressure difference ΔQ (= Po−P1) required for the operation of the load-sensitive pressure-reducing valve 7, and an unnecessary (excess) hydraulic pressure for the load-sensitive pressure-reducing valve 7. Control so that it does not become.

The relief valve 8 controls the pressure (primary pressure) of the pressure oil discharged from the hydraulic pump 3 by, for example, 21
By limiting it to about 0 kgf / cm ² , the maximum load pressure is maintained, and it also functions as a safety valve for the entire hydraulic circuit. Further, the relief valve 8 reduces the hydraulic pressure reduced by the relief from 5 to 1
By limiting the pressure to about 7 kgf / cm ² , even when the hydraulic cylinder 1 is in a no-load state, it also plays a role of securing a minimum primary pressure required for the operation of the load-responsive pressure reducing valve 7.

Thus, a cylinder drive circuit having such a load-sensitive pressure reducing valve 7 provided on the primary side of the hydraulic servo valve 5 is provided, and a relief valve 8 is provided upstream of the cylinder drive circuit (load-sensitive pressure reducing valve 7). According to the hydraulic circuit including the hydraulic cylinder 1, the pressure of the pressure oil supplied from the hydraulic pump 3
Even when the pressure is extremely large as compared with the pressure to be applied to the hydraulic servo valve 5, the pressure is reduced by the load-responsive pressure reducing valve 7 and then applied to the primary side of the hydraulic servo valve 5. Therefore, the valve pressure drop before and after the hydraulic servo valve 5, that is, the pressure difference ΔP between the primary pressure P1 and the secondary pressure P2 does not become excessive. In addition, the load-responsive pressure reducing valve 7 enables
The secondary pressure P1 is controlled so as to always have a constant pressure difference ΔP with respect to the load pressure of the hydraulic cylinder 1 (the secondary pressure of the hydraulic servo valve 5) P2. Therefore, even when the opening degree of the hydraulic servo valve 5 is adjusted under the control of the controller 6, the pressure difference ΔP before and after the servo valve is always kept constant as described above. The oil flow rate can be controlled with high accuracy in accordance with the valve opening, and highly accurate hydraulic servo control can be achieved.

In particular, since it is only necessary to adjust the valve opening of the load-responsive pressure reducing valve 7 in accordance with the load pressure of the hydraulic cylinder 1, that is, the secondary pressure P2 of the hydraulic servo valve 5, the control system is simple. Thus, the pressure before and after the hydraulic servo valve 5 (pressure difference ΔP) can be kept constant simply and effectively. In other words, the pressure across the hydraulic servo valve 5 (pressure difference ΔP) can be easily kept constant without monitoring the pressure across the hydraulic servo valve 5 (pressure difference ΔP).

In controlling the operation of the hydraulic servo valve 5 under the condition that the pressure difference ΔP before and after the hydraulic servo valve 5 is kept constant, the operating state of the hydraulic pump 3 temporarily changes due to some factor. As a result, even if the pressure of the pressure oil supplied from the hydraulic pump 3 fluctuates, the pressure fluctuation is blocked by the load-responsive pressure reducing valve 7, so that the hydraulic servo valve 5 is not adversely affected. Therefore, it is possible to isolate the hydraulic servo valve 5 from the hydraulic pressure source and control the hydraulic servo valve 5 independently with high accuracy.

Further, a relief valve 8 provided in the preceding stage of the cylinder drive circuit operates according to the operation state of the load-sensitive pressure-reducing valve 7 to operate the pressure of pressure oil applied from the hydraulic pump 3 to the load-sensitive pressure-reducing valve 7. Since Po is controlled, the pressure applied to the load-sensitive pressure-reducing valve 7 is not excessively increased, and the load on the load-sensitive pressure-reducing valve 7 is not unintentionally increased. In addition, when the hydraulic cylinder 1 is not loaded, the hydraulic servo valve 5 is not operated, or the secondary hydraulic pressure of the load-responsive pressure reducing valve 7 (the hydraulic servo valve 5
When the secondary side hydraulic pressure is low, the relief valve 8
Operates to reduce the pressure applied to the load-responsive pressure reducing valve 7 to a low level. Therefore, when the hydraulic cylinder 1 is in a no-load state, the pressure of the pressure oil supplied to the primary side of the load-responsive pressure-reducing valve 7 is regulated by the low-pressure relief valve 13 and maintained at a low pressure. The stable operation of the responsive pressure reducing valve 7 becomes possible.

That is, the relief valve 8 is operated in accordance with the operation state of the load-responsive pressure reducing valve 7 (output hydraulic pressure P1) to adjust the pressure of the pressure oil supplied from the hydraulic pump 3 to the primary side thereof. Therefore, the load-responsive pressure reducing valve 7 can be operated stably. As a result, the stable operation of the hydraulic servo valve 5 by the load-sensitive pressure-reducing valve 7 and the stable operation of the load-sensitive pressure-reducing valve 7 by the relief valve 8 are ensured while ensuring the highly accurate servo control. Can be. The pressure difference before and after the hydraulic servo valve 5 and the pressure (pressure difference) before and after the load-responsive pressure reducing valve 7 can be kept small, and the heat generation of the pressure oil due to the heat energy conversion caused by the valve pressure drop is reduced. Can be prevented.
As a result, it is possible to suppress the overall heat generation of the hydraulic circuit and to avoid troublesome work such as incorporating an oil cooler.

In particular, even when the hydraulic cylinder 1 is in a no-load state, the operation of the relief valve 8 can lower the hydraulic pressure of the entire hydraulic circuit. Since the load can be greatly reduced, effects such as a so-called energy saving mode can be set effectively. By the way, by using the cylinder drive circuit configured as described above,
A plurality of hydraulic cylinders can be driven in parallel by sharing one hydraulic source.

The second embodiment shown in FIG. 2 comprises a two-axis type material testing machine provided with two hydraulic cylinders 1a and 1b, or two material testing machines.
Hydraulic servo valves 5a, 5b and their controllers 6a, 6
b and cylinder drive circuits A and B comprising load-responsive pressure-reducing valves 7a and 7b. The load-responsive pressure reducing valves 7a and 7b in each of the cylinder drive circuits A and B are connected to the primary hydraulic pressures Pa1 and Pb1 and the secondary hydraulic pressures Pa2 and Pb2 in the hydraulic servo valves 5a and 5b in the same manner as in the previous embodiment. Pressure difference ΔPa (= Pa2-Pa1), ΔPb (= Pb2-Pb1)
Operate so as to be constant.

On the other hand, the two cylinder drive circuits A and B
The pipeline connecting the input side of each of the load-responsive pressure-reducing valves 7a and 7b to the hydraulic pump 3 which is a common hydraulic pressure source for these cylinder drive circuits A and B mainly includes a relief valve 8. A relief circuit C is provided. The relief circuit C is provided with a hydraulic pressure (hydraulic servo valves 5a, 5) on the output side of the load-responsive pressure reducing valves 7a, 7b in the cylinder drive circuits A, B.
The primary hydraulic pressures Pa1 and Pb1) are introduced through check valves (check valves) 9a and 9b, respectively, and the hydraulic pressures are integrated to drive the relief valve 8. Therefore, the relief valve 8 is driven by the action of the check valves 9a and 9b by receiving the higher one of the hydraulic pressures Pa1 and Pb1 introduced from the output side of each of the load-responsive pressure reducing valves 7a and 7b. A flow control valve (drain valve) 10 is connected to the drive section of the relief valve 8, and the hydraulic pressure applied to the relief valve 8 is controlled by the hydraulic pressures Pa1 and Pb1 introduced through the check valves 9a and 9b. The higher hydraulic pressure is maintained. The hydraulic pressure Pa introduced through the check valves 9a and 9b
It is also possible to configure so that the higher one of Pb1 is maintained by utilizing the leak in the relief valve 8 itself. In this case, since the flow control valve 10 is not required, the configuration can be simplified and the cost can be reduced.

According to the hydraulic circuit thus constructed, if the hydraulic pressure Pa1 on the output side of the load-responsive pressure reducing valve 7a in the cylinder driving circuit A is temporarily changed to the cylinder driving circuit B
Is higher than the hydraulic pressure Pb1 on the output side of the load-responsive pressure-reducing valve 7b, the check valve 9b is closed by the introduction of the hydraulic pressure Pa1 from the cylinder drive circuit A via the check valve 9a. Then, the hydraulic pressure Pa1 is applied to the relief valve 8, and the load-responsive pressure reducing valves 7a, 7b of the cylinder driving circuits A, B
Are set to Pao (= Pa1 + ΔQ). At this time, the load-responsive pressure reducing valve 7b in the cylinder drive circuit B has a hydraulic pressure Pa higher than the hydraulic pressure Pbo (= Pb1 + ΔQ) based on the hydraulic pressure Pb1 on the output side.
Although o (= Pa1 + ΔQ) is supplied, only the valve pressure drop at the load-responsive pressure reducing valve 7b increases, and the operation of the hydraulic servo valve 5b is not affected.

Conversely, when the hydraulic pressure Pa1 on the output side of the load-responsive pressure reducing valve 7b in the cylinder drive circuit B is high, the check valve is introduced by the introduction of the hydraulic pressure Pb1 from the cylinder drive circuit B via the check valve 9b. 9a is closed. Then, the hydraulic pressure Pb1 is applied to the relief valve 8, and the hydraulic pressure supplied to each of the load-responsive pressure reducing valves 7a and 7b of the cylinder drive circuits A and B is set to Pbo (= Pb1 + ΔQ). That is, the hydraulic pressure P introduced through the check valves 9a and 9b
The operation of the relief valve 8 is controlled by the higher oil pressure of a1 and Pb1, and the oil pressure supplied to the load-responsive pressure reducing valves 7a and 7b is set. Therefore, the load-responsive pressure-reducing valves 7a and 7b in the cylinder drive circuits A and B maintain the pressures in the hydraulic cylinders 1a and 1b while maintaining a constant pressure (pressure difference ΔP) between the hydraulic servo valves 5a and 5b. The minimum required hydraulic pressure determined accordingly will be supplied,
Each of the load-responsive pressure reducing valves 7a and 7b can be operated stably.

Further, when the hydraulic circuit having the above-described configuration is employed, the required capacity (discharge capacity) of the hydraulic source (hydraulic pump 3) can be reduced. That is, in a two-shaft type material testing machine, it is rare to operate two hydraulic cylinders 1a and 1b at the same time. For example, when performing a shear test, one hydraulic cylinder 1a is operated to perform a test. After holding the piece, the other hydraulic cylinder 1b is operated to apply shear stress while maintaining the state. Therefore, in such a case, one hydraulic cylinder 1
It is only necessary to drive the cylinder drive circuit of the other hydraulic cylinder 1a while maintaining the state of the cylinder drive circuit that has driven a. Since the operation is static, for example, it is necessary to individually drive each of the hydraulic cylinders 1a and 1b. It is sufficient to use the hydraulic pump 3 having a pump capacity slightly higher than the pump capacity. Therefore, secondary effects such as reduction in cost and size of the hydraulic power source can be achieved. In addition, since the hydraulic power source including the relief circuit C can be integrated into one independent from the cylinder drive circuits A and B, the maintenance can be simplified.

The present invention is not limited to the above embodiment. For example, the back-and-forth pressure (pressure difference ΔP) of the hydraulic servo valve 5 may be determined according to the specifications of the hydraulic circuit, and the operating pressure (degree of pressure reduction) of the load-responsive pressure reducing valve 7 is set according to the specifications. What should I do? Also, the relief pressure by the relief valve 8 may be determined according to the specifications of the load-responsive pressure-reducing valve 7 and the hydraulic pump 3. Further, it is possible to drive three or more cylinder drive circuits in parallel. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0028]

As described above, according to the present invention, a load-responsive pressure reducing valve is provided on the primary side of a hydraulic servo valve, and the hydraulic pressure is controlled by a relief valve while the front-rear pressure of the hydraulic servo valve is always kept constant. Since the hydraulic pressure supplied from the source to the load-responsive pressure reducing valve is controlled, highly accurate control of the hydraulic cylinder can be performed. Therefore, the generation of heat energy due to the valve pressure effect in the hydraulic servo valve can be suppressed, and the hydraulic pressure can be efficiently controlled without imposing an extra burden on the load-responsive pressure reducing valve. The effect is achieved.

Also, when the hydraulic cylinder is in a no-load state or when the primary hydraulic pressure of the hydraulic servo is low, the pressure oil supplied from the hydraulic source is suppressed to a low pressure. Effects such as energy saving can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a hydraulic circuit in a material testing machine according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a hydraulic circuit in a material testing machine according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 1a, 1b Hydraulic cylinder 3 Hydraulic pump 5, 5a, 5b Hydraulic servo valve 6, 6a, 6b Controller 7, 7a, 7b Load-sensitive pressure reducing valve 8 Relief valve 9a, 9b Check valve 10 Flow control valve A, B Cylinder drive circuit C relief circuit

Claims (3)

[Claims] 1. A hydraulic servo valve for driving a hydraulic cylinder for adjusting a hydraulic pressure supplied from a hydraulic source and applying a load to a test piece, and a hydraulic servo valve provided between the hydraulic servo valve and the hydraulic source. A cylinder drive circuit including a load-sensitive pressure-reducing valve for reducing the oil pressure supplied to the hydraulic servo valve in accordance with the oil pressure on the output side of the valve to make the oil pressure difference before and after the hydraulic servo valve constant; A relief valve for adjusting a hydraulic pressure supplied from the hydraulic pressure source to an input side of the load-sensitive pressure-reducing valve in accordance with a hydraulic pressure on an output side of the load-sensitive pressure-reducing valve in a circuit. . 2. A hydraulic servo valve for driving a hydraulic cylinder that applies a load to a test piece by adjusting a hydraulic pressure supplied from a hydraulic source, and a hydraulic servo valve provided between the hydraulic servo valve and the hydraulic source. A plurality of cylinder drive circuits including a load-responsive pressure-reducing valve for reducing the oil pressure supplied to the hydraulic servo valve in accordance with the oil pressure on the output side of the valve to make the oil pressure difference before and after the hydraulic servo valve constant, A relief valve provided on a hydraulic pressure source side for adjusting a hydraulic pressure supplied from the hydraulic pressure source to an input side of each of the load-responsive pressure-reducing valves in accordance with a hydraulic pressure on an output side of each of the load-responsive pressure-reducing valves in the plurality of cylinder drive circuits. A material testing machine comprising: a relief circuit provided with: 3. The relief circuit according to claim 1, further comprising a plurality of check valves that respectively drive the relief valve by introducing hydraulic pressures on the output side of each of the load-responsive pressure reducing valves in a plurality of cylinder drive circuits. The material testing machine according to claim 2, wherein