Material testing machine

Patent metadata

Field	Value
Publication number	US-9835483-B2
Application number	US-201414506214-A
Country	US
Kind code	B2
Filing date	Oct 3, 2014
Priority date	Dec 9, 2013
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

A hydraulic pressure source includes an oil tank for storing hydraulic oil, a hydraulic pump, a motor for driving this hydraulic pump, and an inverter for changing a rotational frequency of the motor. A pipe line for drawing the hydraulic oil from the oil tank by operation of the hydraulic pump branches to a supply pipe line for supplying the hydraulic oil to the hydraulic cylinder, and a release pipe line for releasing superfluous hydraulic oil into the oil tank. The release pipe line has arranged thereon a pressure regulating mechanism and a flowmeter which measures a flow rate of the hydraulic oil flowing into the release pipe line. Based on a measurement value of the flowmeter, the inverter is operable to change the rotational frequency of the motor to become a necessary minimum rotational frequency.

First claim

What is claimed is:

1. A material testing machine for conducting a material testing by applying a testing force to a test specimen, the machine comprising a hydraulic cylinder, a hydraulic pressure source for supplying hydraulic oil to the hydraulic cylinder, and a flow control valve for controlling flow rates of the hydraulic oil which flows into the hydraulic cylinder and out of the hydraulic cylinder; wherein
the hydraulic pressure source includes:
a pump for feeding the hydraulic oil in a tank to the hydraulic cylinder;
a motor for driving the pump;
an inverter connected to the motor for changing a rotational frequency of the motor;
a release pipe line having mounted thereon a pressure regulating mechanism for regulating a pressure in a hydraulic circuit, the release pipe line branching from a pipe line which supplies the hydraulic oil from the tank through the pump to the hydraulic cylinder, for releasing a superfluous part of the hydraulic oil discharged from the pump;
a flowmeter mounted on the release pipe line for measuring a flow rate of the hydraulic oil flowing into the release pipe line;
a controller for controlling the rotational frequency of the motor through the inverter based on a measurement value of the flowmeter; and
wherein the pressure regulating mechanism includes a relief valve with an electromagnetic selector valve that is capable of flow path switching between a vent to the exterior and an oil tank.

2. The material testing machine according to claim 1 , further comprising:
a displacement detector for detecting strokes of a cylinder rod of the hydraulic cylinder when conducting the material testing by applying the testing force to the test specimen;
an input unit for setting beforehand the strokes of the cylinder rod of the hydraulic cylinder when conducting the material testing by applying the testing force to the test specimen; and
a storage unit for storing the strokes of the cylinder rod of the hydraulic cylinder inputted by the input unit;
wherein the controller is arranged to set an initial starting rotational frequency of the motor in response to whether a testing control mode selected at a time of starting the testing is a stroke control mode based on a detection value of the displacement detector or a control mode other than the stroke control mode, and when the testing control mode selected at the time of starting the testing is the stroke control mode, to start the motor at a rotational frequency according to a discharge rate of the pump calculated based on the strokes of the cylinder rod of the hydraulic cylinder stored in the storage unit.

3. The material testing machine according to claim 1 , wherein the controller is arranged to monitor a difference between a control signal of the flow control valve and a testing waveform during the testing, and when the difference exceeds a threshold set beforehand, to change the rotational frequency of the motor through the inverter.

4. The material testing machine according to claim 2 , wherein the controller is arranged to monitor a difference between a control signal of the flow control valve and a testing waveform during the testing, and when the difference exceeds a threshold set beforehand, to change the rotational frequency of the motor through the inverter.

5. The material testing machine according to claim 1 , wherein the pressure regulating mechanism further includes a proportional electromagnetic relief valve with a pressure sensor, which is connected to a bypass pipe line and is capable of proportionally controlling pressure in the hydraulic circuit in response to input voltage.

6. The material testing machine according to claim 5 , wherein the relief valve with the electromagnetic selector valve is capable of switching the flow path of the hydraulic oil to an oil tank at a no-load time.

7. The material testing machine according to claim 6 , wherein during a test execution with a load application, the hydraulic circuit has a pressure that is controlled by the proportional electromagnetic relief valve.

8. The material testing machine according to claim 7 , wherein the proportional electromagnetic relief valve is capable of changing pressure of flowing hydraulic oil while maintaining the cross-sectional area of the bypass pipe line constant.

9. The material testing machine according to claim 1 , wherein the flowmeter is disposed on the side of the release pipe line closer to the hydraulic pump than is the pressure regulating mechanism.

10. The material testing machine according to claim 1 , wherein the release pipe line is connected to the common pipe line that is connected to the return pipe line for returning oil returned from the cylinder to the tank, and an oil cooler is provided in the common pipe line.

Assignees

• Shimadzu Corp

Inventors

• Kimura Motofumi

Classifications

• G01F1/34 Primary

  by measuring pressure or differential pressure · CPC title

• G01N2203/0042

  Pneumatic or hydraulic means · CPC title

• G01N3/10

  generated by pneumatic or hydraulic pressure (G01N3/18 takes precedence) · CPC title

• G01N3/08 Primary

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title