JP5024877B2 - Fatigue test linear actuator - Google Patents

Description

  The present invention relates to a fatigue test linear actuator that applies a force generated by an electric cylinder to a force generated by an electric cylinder and repeatedly and repeatedly applies a compressive load or a tensile load to a specimen. The present invention relates to a fatigue test linear actuator that synchronizes the operation with a hydraulic cylinder and continuously applies a load due to a reciprocating motion to a specimen.

  For example, a fatigue test has conventionally been performed on a body, suspension, or chassis of an automobile to evaluate the life reliability. In the fatigue test, a compressive load or a tensile load due to a reciprocating linear motion continuously acts on the specimen to be tested, and the test is repeated until it breaks. As a fatigue test actuator that outputs such a constant load waveform, a hydraulic actuator has been conventionally used. For example, Patent Document 1 below discloses a fatigue tester.

In this fatigue testing machine 100, an actuator 102 made of a hydraulic cylinder is provided on a frame 101, and a specimen S is held between the frame 101 and the actuator 102 via a load cell 103. The actuator 102 is supplied with hydraulic fluid sent from the hydraulic pressure source 104, and the rod 110 reciprocates by switching the servo valve 105, whereby a load is repeatedly applied to the specimen S continuously. At that time, the load applied to the specimen S is detected by the load cell 103, and the displacement and strain are detected by the displacement meter 106 and the strain gauge 107. Based on the detected load, displacement, and strain values, the control unit 108 controls the operation of the servo valve 105 via the servo amplifier 109.
JP-A-11-64193 JP 2003-53587 A

  However, conventional fatigue test actuators composed of hydraulic cylinders have a large hydraulic source structure consisting of a hydraulic pump for generating the necessary load, a drive motor for driving the hydraulic pump, and an oil tank. There was a problem of increasing the size. In addition, the conventional fatigue test actuator has a problem that a large amount of energy loss occurs in the pipe in the middle because hydraulic oil flows from the hydraulic pump through the pipe to the hydraulic cylinder and outputs a load there.

  Therefore, it is conceivable to switch the fatigue test actuator from a hydraulic cylinder to an electric cylinder. However, in the fatigue testing machine, for example, a load of about 2 to 5 tons must be continuously applied to the specimen, so that the load on the ball screw that converts the rotational force into thrust is large. Therefore, since the wear of the ball screw portion is severe, the life is short, and while the load is continuously applied, the load waveform having a constant cycle is distorted and the test accuracy is lowered. For this reason, the electric cylinder alone cannot be realized as a fatigue test actuator.

  In this regard, Patent Document 2 discloses an actuator that assists by applying hydraulic pressure to the output of an electric cylinder, although it is an electric press device. Specifically, as shown in FIG. 3, the motor 202 is driven by the control of the electric cylinder control device 201 to advance to the pre-programmed amount of movement of the piston rod 203 and stop pressing. To do. On the other hand, the accumulator 205 is preliminarily pressurized by a hydraulic pump 206, and the hydraulic pressure is applied to the load side and the anti-load side of the cylinder tube 208 by energizing the switching valve 207, and is pushed by the area difference. Generate pressure.

  The actuator 200 has an effect that the load applied to the screw mechanism 210 is reduced and the life can be extended by the hydraulic pressure assisting the output of the electric cylinder. However, the hydraulic circuit is relatively large, and the assist using the accumulated pressure of the accumulator 205 cannot be used for a fatigue test in which a load is continuously applied. Therefore, when considering what assists the output of the electric cylinder with hydraulic pressure, it is necessary to develop a fatigue test actuator adapted to the fatigue tester.

  Therefore, in order to solve such problems, the present invention assists the output of the electric cylinder with the output of the hydraulic cylinder, and is capable of maintaining a load on the specimen by continuous and accurate reciprocating linear motion. It aims at providing the linear actuator for a test.

The linear actuator for fatigue testing according to the present invention applies a load continuously and repeatedly to a specimen, forms a ball screw between the rotating rod and the thrust block, and is applied from the driving motor to the rotating rod. An electric cylinder that generates thrust as a repetitive load from the thrust block by rotation, and a hydraulic cylinder that is connected to a closed hydraulic circuit and outputs the reciprocating linear motion of the piston rod under the pressure of hydraulic oil sent from a hydraulic pump A drive motor for operating the electric cylinder is connected to the hydraulic pump, a piston rod of the hydraulic cylinder is connected to the thrust block, and an operation of the electric cylinder and the hydraulic cylinder is the drive Synchronized with the output of the motor, the output of the hydraulic cylinder is generated from the electric cylinder. It said that the thrust of the thrust block is obtained so as to assist that,
A plurality of the thrust blocks are arranged along the axial direction of the rotating rod, and each thrust block is fixed at a predetermined interval with respect to a shaft for transmitting a load to the specimen. It is characterized by being.

The fatigue test linear actuator according to the present invention is provided in the actuator body so that the rotating rod is rotatably supported via a bearing, and the thrust block is moved along the rotating rod. It is preferable that the hydraulic cylinder is provided in the actuator body.

Further, in the fatigue test linear actuator according to the present invention, the actuator main body is provided with a guide rail along the axial direction of the rotating shaft on the inner peripheral surface side, and the thrust block extends along the guide rail. It is preferable to hold a rolling guide ball.
In the fatigue test linear actuator according to the present invention, the guide rail is a rail member arranged along the axial direction of the rotating shaft, and the rail member is positioned in the radial direction of the rotating rod. It is preferable that the actuator is attached to the actuator body with an adjusting screw for adjusting.
The linear actuator for fatigue test according to the present invention has a displacement sensor that detects a change in the radial direction of the shaft fixed to the thrust block in order to transmit a load to the specimen. It is preferable that the change of the shaft generated in the direction is detected.

  Therefore, in the fatigue test linear actuator of the present invention, when the rotation direction of the drive motor is continuously switched during the fatigue test of the specimen, the thrust block of the electric cylinder and the hydraulic cylinder are synchronized each time and are pushed against the specimen. Pressure and tensile force are repeatedly applied. According to the present invention, the load that assists the output of the hydraulic cylinder is applied to the thrust of the electric cylinder, and the fatigue can be continuously applied to the specimen by continuous and accurate reciprocating linear motion. A linear actuator for testing can be provided.

In addition, according to the present invention, since the plurality of thrust blocks are fixed at a predetermined interval with respect to the shaft for transmitting the load to the specimen, the load on the ball held by each thrust block is determined. Can reduce the accuracy of the load waveform due to wear of the ball, and can improve problems such as noise.
Further, since the thrust block is smoothly moved in the axial direction by the guide ball and the guide rail, even when a lateral load is applied, the load can be repeatedly applied to the specimen with a stable load waveform.
In addition, changes due to wear of the guide ball can be detected by a displacement sensor, and by adjusting the position of the guide rail based on the detection result, repeated loads with a stable load waveform can be applied by preventing backlash, etc. Can do.

Next, an embodiment of a linear actuator for fatigue test according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a fatigue test linear actuator of the present embodiment.
This fatigue test linear actuator (hereinafter simply referred to as “actuator”) 1 converts a rotary motion of the drive motor 2 into a reciprocating linear motion and outputs it, and a reciprocating linear motion by the hydraulic oil pressure of a hydraulic pump. The output hydraulic cylinder is integrally formed. In particular, one drive motor 2 is configured to operate the hydraulic pump and synchronize the operations of both cylinders.

  The actuator 1 has a rotating rod 12 inserted into a cylindrical actuator body 11 through its center. The rotating rod 12 is rotatably supported by a bearing 13 in the actuator body 11, and a belt 14 is stretched around each pulley between the rotating rod 12 and the drive motor 2. The rotating rod 12 that receives the rotational output of the drive motor 2 passes through the thrust blocks 15 and 16 in the actuator body 11, and a ball screw is formed between the two. That is, a sliding portion in which a plurality of balls 17 are inserted is formed in a groove formed in the rotating rod 12 and the thrust blocks 15 and 16, and the rotation of the rotating rod 12 moves in the axial direction of the thrust blocks 15 and 16. And is configured to generate thrust.

  Two to four shafts 18 that penetrate the actuator body 11 in the axial direction are fixed to the thrust blocks 15 and 16, and a load cell for measuring a load applied to the specimen is attached to the tip of the shaft 18. 19 is attached. A load cell 19 is connected to a specimen to be subjected to a fatigue test via a jig (not shown). Note that the actuator 1 may perform load control with respect to the specimen by the load cell 19 or may perform stroke control with the differential transformer 20 provided with respect to the shaft 18.

  In the present embodiment, the two thrust blocks 15 and 16 are arranged at the front and rear, and the thrust obtained through the rotating rod 12 is generated at two locations. This is because, when a load is applied to the specimen, the reaction force acts as a large load on the ball 17 of the sliding portion, so that the places where the thrust is generated are dispersed to reduce the load received by each ball 17. I try to let them. Further, the thrust blocks 15 and 16 are arranged at a certain distance in order to improve the straight running stability. The shaft 18 is fixed so that its end is abutted against the thrust block 15, and is fixed to the other thrust block 16 in a penetrating manner.

  The thrust blocks 15 and 16 have a cylindrical shape that matches the actuator body 11, and the plurality of shafts 18 are prevented from rotating, and the guide mechanism with the actuator body 11 is also prevented from rotating. In other words, a plurality of guide balls 21 are held side by side in the axial direction between the actuator bodies 11 on the outer peripheral side of the thrust blocks 15 and 16. The ball rows made up of a plurality of guide balls 21 are provided in four rows at 90 ° intervals, for example, in the circumferential direction for each of the thrust blocks 15 and 16.

  This guide mechanism is configured to ensure a smooth reciprocating linear motion without the thrust blocks 15 and 16 being twisted with the actuator body 11 even when a radial force is applied to the shaft 18 during the fatigue test. Is. That is, when the pressing force or tensile force F by the actuator 1 acts on the acting surface of the specimen, a moment acts on the shaft 18. Therefore, the smooth movement of the thrust blocks 15 and 16 is ensured by the guide ball 21 even under such a lateral load.

  The guide ball 21 is disposed between the guide rail 22 provided on the inner peripheral surface side of the actuator body 11 and the thrust blocks 15 and 16. The guide rail 22 is separate from the actuator body 11 and is supported by an adjustment screw 23 with a handle screwed to the actuator body 11. That is, as described above, the guide ball 21 rotates while receiving a lateral load due to a moment, so that the wear is caused by the wear, or the wear amount is biased and the shaft 18 is inclined to increase the test accuracy. I will drop it. Therefore, in the present embodiment, by adjusting the screwing position of the adjusting screw 23, it is intended to prevent backlash and inclination of the thrust blocks 15 and 16 generated in the radial direction.

  The actuator body 11 is provided with a displacement sensor 25 such as a proximity sensor on each shaft 18 so as to detect the displacement of each shaft 18. Note that the displacement sensor 25 is arranged so as to detect two positions of the plurality of shafts 18, that is, a position between the thrust blocks 15 and 16 and a position protruding from the actuator body 11. Further, the displacement sensor 25 is connected to a display device (not shown) that displays a detection result, and information related to backlash by the guide mechanism and the inclination of the shaft 18 is displayed. As a result, the operator operates the adjustment screw 23 to absorb the play due to the displacement of the guide rail 22, and the inclination can be adjusted.

  By the way, the continuous reciprocating linear motion by the actuator 1 cannot be stopped during a fatigue test in which a pressing force or tensile force is applied to the specimen. Therefore, in this embodiment, by observing the detection value by the displacement sensor 25, it is possible to measure the timing of the replacement of the parts such as the guide ball 21. For this reason, a certain threshold value may be set, and when a detection value by the displacement sensor 25 exceeds the threshold value, a replacement alarm lamp (not shown) may be blinked.

  Subsequently, in the actuator 1 of the present embodiment, a hydraulic cylinder is added as a configuration in addition to the electric cylinder using a ball screw. That is, the load applied to the specimen is assisted by adding the output from the hydraulic cylinder 31 to the thrust applied to the shaft 18 by the thrust blocks 15 and 16. Two or more hydraulic cylinders 31 are arranged in the actuator body 11 in a balanced manner at equal intervals in the circumferential direction, and the cylinder tube is fixed to the actuator body 11. In each hydraulic cylinder 31, the piston rod 32 protrudes in the axial direction, and in particular, one end is connected and fixed to the thrust block 15.

  A common hydraulic circuit is connected to the plurality of hydraulic cylinders 31. This hydraulic circuit has a hydraulic pump 33 to which a pressing side pipe 35 and a pulling side pipe 36 are connected. Each hydraulic cylinder 31 includes a pressure-side hydraulic chamber and a tension-side hydraulic chamber sandwiching a piston, and a pressure-side pipe 35 and a tension-side pipe 36 are connected to each other. In other words, one pressing side pipe 35 and one pulling side pipe 36 are connected from a hydraulic pump 32 to a plurality of hydraulic cylinders 31 to form a closed hydraulic circuit as shown.

  In the actuator 1, the hydraulic pump 32 is connected to the drive motor 2 common to the electric cylinder, and the motion of the piston rod 32 of the hydraulic cylinder 31 is output in synchronization with the propulsion of the thrust blocks 15 and 16. Yes. In this closed hydraulic circuit, the flow direction of the hydraulic oil by the hydraulic pump 32 is determined according to the rotational direction of the drive motor 2, which generates the output of the hydraulic cylinder 31 in accordance with the moving direction of the thrust blocks 15 and 16. Be able to.

  An oil tank 37 is provided in the closed hydraulic circuit, and relief valves 38a and 38b and check valves 39a and 39a are respectively connected to pipes branched from the pressure side pipe 35 and the tension side pipe 36 and connected to the oil tank 37. 39b is provided. Therefore, the hydraulic oil from the hydraulic pump 32 to the hydraulic cylinder 31 is supplied according to the set pressure of the relief valves 38a and 38b. However, when a hydraulic pressure exceeding the set pressure is applied, the relief valves 38a and 38b are opened, It flows to the oil tank 37. For example, when the hydraulic oil supplied to the pressing side pipe 35 exceeds the set pressure, the relief valve 38a is opened and flows from the check valve 39a to the pulling side pipe 36 via the oil tank 37, thereby the hydraulic pump 33. A circulation to return to occurs.

  Therefore, according to the actuator 1 of the present embodiment, when the rotation of the drive motor 2 is output from the shaft 3, the rotation is transmitted to the rotating rod 12 in the actuator body 11, and the hydraulic motor 33 is driven. Accordingly, the rotation of the rotary rod 12 moves the thrust blocks 15 and 16 in the axial direction to generate thrust, while the hydraulic motor 33 is driven to cause the hydraulic oil to flow in a predetermined direction in the closed hydraulic circuit. As a result, the piston rod 32 of the hydraulic cylinder 31 is projected in a predetermined direction.

  Specifically, when the thrust blocks 15 and 16 move to the left side of the drawing to generate a pushing force, the hydraulic oil is sent from the hydraulic pump 33 to the pushing side pipe 35. Then, the piston of the hydraulic cylinder 31 is pressurized to the left side of the drawing, and the piston rod 32 assists by pushing the thrust blocks 15 and 16 in the moving direction. When the drive motor 2 outputs rotation in the reverse direction, the thrust blocks 15 and 16 generate a pulling force that moves to the right side of the drawing, and at the same time, hydraulic oil is sent from the hydraulic pump 33 to the pulling side pipe 36. Then, the piston of the hydraulic cylinder 31 is pressurized to the right side of the drawing, and the piston rod 32 assists by pulling the thrust blocks 15 and 16 in the moving direction.

  Therefore, in the actuator 1 of the present embodiment, when the rotation direction of the drive motor 2 is continuously switched during the fatigue test of the specimen, the thrust blocks 15 and 16 and the hydraulic cylinder 31 are synchronized each time and A pressing force and a tensile force are repeatedly applied. Therefore, according to the present embodiment, there is provided an actuator 1 having a structure in which the thrust of the electric cylinder assists the output of the hydraulic cylinder and can continue to apply a load to the specimen by continuous and accurate reciprocating linear motion. It became possible.

  Since the actuator 1 assists the thrust of the thrust cylinders 15 and 16 to assist the output of the hydraulic cylinder 31, the load on the balls 17 constituting the ball screw in the thrust blocks 15 and 16 is reduced, and the life is extended by reducing wear. It became possible. Further, the load on the ball 17 can be reduced by dividing the thrust blocks 15 and 16 and distributing the load. Therefore, in the fatigue test, wear of the ball screw ball due to a small reciprocating sliding motion may cause problems such as deterioration of the waveform accuracy of the load applied to the specimen and noise, but in this embodiment, As described above, by reducing the load on the screw part, it was possible to improve such problems.

In addition, the thrust blocks 15 and 16 are smoothly moved in the axial direction by the guide balls 21 and the guide rails 22 so that the load is repeatedly applied to the specimen with a stable load waveform even when a lateral load is applied. Can now.
Further, since a change due to wear of the guide ball 21 is detected by the displacement sensor 25 and the position of the guide rail 22 is adjusted on the basis of the detection result, a repeated load with a stable load waveform is also provided in this respect to prevent backlash. Can now work.

Further, since the operation of the electric cylinder including the thrust blocks 15 and 16 and the operation of the hydraulic cylinder including the hydraulic cylinder 31 are synchronized by one drive motor 2, complicated control is not required. Further, since the structure is simplified and a hydraulic cylinder is incorporated in the actuator body 11, the whole can be reduced in size.
Furthermore, in the present embodiment, the hydraulic oil 31 is operated by changing the direction of the hydraulic oil flowing in the closed hydraulic circuit, so that the energy loss due to the hydraulic oil flowing through the pipe is small, and the energy efficiency as a whole is low. Could be good.

As mentioned above, although one Embodiment of the linear actuator for fatigue tests concerning this invention was described, this invention is not limited to this, A various change is possible in the range which does not deviate from the meaning.
For example, in the above embodiment, the thrust blocks 15 and 16 divided into two are shown, but one thrust block may be used, or three or more divided blocks may be used.

It is the block diagram which showed embodiment of the linear actuator for fatigue tests. It is the figure which showed the structure of the conventional fatigue testing machine which used the hydraulic cylinder as the actuator. It is the figure which showed the structure of the electric press apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Linear actuator for fatigue tests 2 Drive motor 11 Actuator main body 12 Rotating rods 15 and 16 Thrust block 17 Ball 18 Shaft 19 Load cell 21 Guide ball 22 Guide rail 23 Adjustment screw 25 Displacement sensor 31 Hydraulic Linder 32 Piston rod 33 Hydraulic pump 35 Press side Piping 36 Pull side piping

Claims (5)

In fatigue testing linear actuators, where the load is continuously and repeatedly applied to the specimen,
An electric cylinder that constitutes a ball screw between the rotating rod and the thrust block, and generates thrust that becomes the repetitive load from the thrust block by rotation applied from the drive motor to the rotating rod;
A hydraulic cylinder connected to the closed hydraulic circuit and receiving the pressure of the hydraulic oil delivered from the hydraulic pump and outputting a reciprocating linear motion of the piston rod;
A drive motor for operating the electric cylinder is connected to the hydraulic pump, and a piston rod of the hydraulic cylinder is connected to the thrust block,
The operation of the electric cylinder and the hydraulic cylinder are synchronized by the output of the drive motor, and the output of the hydraulic cylinder assists the thrust of the thrust block generated from the electric cylinder ;
A plurality of the thrust blocks are arranged along the axial direction of the rotating rod, and each thrust block is fixed to the shaft for transmitting a load to the specimen with a predetermined interval. A linear actuator for fatigue testing, characterized by In the linear actuator for fatigue testing according to claim 1 ,
The rotary rod is rotatably supported in the actuator body via a bearing, the thrust block is provided to move along the rotary rod, and the hydraulic cylinder is provided in the actuator body. A linear actuator for fatigue testing characterized by being a thing. In the linear actuator for fatigue testing according to claim 2 ,
The actuator body is provided with a guide rail on the inner peripheral surface side along the axial direction of the rotating shaft, and the thrust block holds a guide ball that rolls along the guide rail. Linear actuator for fatigue testing. In the linear actuator for fatigue testing according to claim 3 ,
The guide rail is a rail member disposed along the axial direction of the rotating shaft, and the rail member is attached to the actuator body by an adjusting screw that adjusts the position of the rotating rod in the radial direction. A linear actuator for fatigue testing characterized by being a thing. In the linear actuator for fatigue tests according to any one of claims 1 to 4 ,
For the shaft fixed to the thrust block to transmit the load to the specimen, it has a displacement sensor that detects the change in the radial direction of the shaft, and detects the change in the shaft that occurs in the radial direction. A linear actuator for fatigue testing.

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