JP5014186B2 - Control device for hydraulic cylinder - Google Patents

Description

  The present invention relates to a control device for a hydraulic cylinder.

  2. Description of the Related Art Conventionally, position detection devices that detect the position of a piston in a cylinder tube of a hydraulic or hydraulic cylinder are known.

For example, a method of detecting a magnetic piston attached to a piston rod by fixing an iron detection device to the outside of a non-magnetic cylinder tube as in the position detection device of Patent Document 1 is known. Since the cylinder tube does not have magnetism, the position detection device can detect the position by detecting the approach of the piston, which is a magnetic body, without attaching a magnet to the piston side.
Japanese Patent Laid-Open No. Sho 63-11501

  However, particularly in a cylinder with a large load, such as a hydraulic cylinder, the cylinder tube is usually composed of a carbon steel pipe which is a ferromagnetic material. Some austenitic stainless steel pipes are non-magnetic, but they are less used because they are more expensive than carbon steel pipes.

  If the carbon steel pipe is cheaper and stronger than the stainless steel pipe, the method of Patent Document 1 cannot be applied, and a method of detecting a magnet by providing a magnet on the piston side must be taken. In this case, there has been a problem that the modification is troublesome or foreign matter enters the cylinder tube during the modification.

  The present invention has been made in view of such points, and the object of the present invention is to accurately detect the position of the piston and adjust the piston speed even when a magnetic cylinder tube is used. is there.

  In order to achieve the above object, in the present invention, a change in the amount of strain detected from a strain gauge attached to the cylinder tube is detected, and the speed control of the hydraulic cylinder is performed using this detection result.

Specifically, in the first invention, a hydraulic cylinder control for controlling a hydraulic cylinder having a cylinder tube and a piston rod having a piston at one end and sliding in the cylinder tube. Assuming equipment
A strain gauge attached to the outer periphery of the cylinder tube;
Detecting means for detecting a cylinder stroke by changing a strain amount of the strain gauge when the piston passes a position corresponding to the strain gauge;
Speed adjusting means for adjusting the moving speed of the piston according to the detection result of the detecting means.

  That is, in the hydraulic cylinder, the piston moves and the cylinder stroke changes due to the difference in pressure in the region divided by the piston by increasing the hydraulic pressure in the cylinder tube. In a single-acting hydraulic cylinder, when the piston rod goes from a contracted state to an extended state, the internal pressure in the tube, which was low before the piston passes through, rises all at once when the piston passes through. The diameter increases and the strain gauge detects the strain. Conversely, when the piston rod is extended from the extended state to the contracted state, the internal pressure in the tube, which was high before the piston passes, decreases all at once when the piston passes, so the outer diameter of the cylinder tube becomes smaller, and the strain gauge Detects distortion. Thus, since the detection means detects that the piston has passed, the cylinder stroke can be detected from the position of the strain gauge.

  In the case of a return-acting hydraulic cylinder, the piston rod in the tube that had been lowered before passing through the piston, both when the piston rod changed from the extended state to the contracted state and when the piston rod changed from the extended state to the contracted state, Since the internal pressure rises at once when the piston passes, the outer diameter of the cylinder tube increases, and the strain gauge detects the strain. Thus, since it is detected that the piston has passed, the detection means can detect the cylinder stroke based on the position of the strain gauge.

  By attaching the strain gauge in this way, the cylinder stroke can be accurately detected even with a magnetic hydraulic cylinder in which a proximity sensor cannot be installed. Then, the speed adjusting means adjusts the moving speed of the piston according to the detection result of the detecting means, for example, it is possible to slow down the moving speed of the piston before the stroke end or stop the moving of the piston. It becomes. In addition, since it is not necessary to detect the passage of the piston with a proximity sensor as in the prior art, the cylinder stroke can be accurately detected even if the cylinder tube is a ferromagnetic material such as a carbon steel pipe.

In the second invention, in the first invention,
The strain gauge is attached in front of the stroke end of the piston, and the speed adjusting means responds to the detection result of the detecting means that detects the change in the strain amount of the strain gauge, and the speed adjusting means It is configured to reduce the flow rate.

  According to the above configuration, the cylinder stroke can be accurately detected by the detection means, so the impact on the hydraulic cylinder is effectively reduced by reducing the piston moving speed by reducing the flow rate of the working fluid before the stroke end. Is done.

  As described above, according to the present invention, the strain gauge is attached to the outer periphery of the cylinder tube, the cylinder stroke is detected from the change in the strain amount of the strain gauge when the piston passes, and the detection signal is received in response to the detection signal. By adjusting the moving speed, it is possible to accurately detect the position of the piston and adjust the piston speed even when a magnetic cylinder tube is used.

  Furthermore, even if a cylinder tube made of a ferromagnetic material is provided, by detecting a change in the strain amount of the strain gauge, it is possible to accurately detect the cylinder stroke and easily adjust the moving speed of the piston.

  According to the second aspect of the invention, the change in the strain amount of the strain gauge attached before the stroke end of the piston is detected, and the flow rate of the working liquid to the hydraulic cylinder is reduced. It is possible to reduce the impact at the stroke end by relaxing the moving speed of the piston in front.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Cylinder stroke detection method-
First, a cylinder stroke detection method using a strain gauge will be described.

  FIG. 1 shows a hydraulic cylinder 1 as a hydraulic cylinder according to an embodiment of the present invention. The hydraulic cylinder 1 is a single-acting type. The hydraulic cylinder 1 includes a cylinder tube 2 and a piston rod 4 having a piston 3 at one end, and the piston 3 slides in the cylinder tube 2. The cylinder tube 2 is made of a ferromagnetic carbon steel pipe. A packing 5 is fitted on the outer periphery of the piston 3. A cylinder hydraulic pipe 6 is connected to the base end side of the cylinder tube 2. A compression coil spring 7 is inserted between the outer periphery of the piston rod 4 opposite to the cylinder hydraulic pipe 6 and the inner periphery of the cylinder tube 2 so as to apply a biasing force when the piston 3 returns. Has been.

  As a feature of the present invention, as shown in FIGS. 1 to 4, strain gauges 8, 9, and 10 are attached to the outer periphery of the cylinder tube 2. For example, a first gauge 8, a second gauge 9, and a third gauge 10 are attached in order from the base end side of the cylinder tube 2. The first gauge 8 is attached to a position where the piston 3 is slightly advanced from the base end side of the cylinder tube 2. The third gauge 10 comes to a position just above the packing 5 of the piston 3 when the tip end of the piston 3 passes directly under the stroke end and the compression coil spring 7 is at the fully stroked stroke end. It is attached as follows. The second gauges 9 are respectively attached in the middle of these. In the drawing, the mounting positions of the strain gauges 8, 9, and 10 are indicated by black inverted triangles for easy viewing.

  In the hydraulic cylinder 1, high pressure oil is poured from the cylinder hydraulic pipe 6, the hydraulic pressure in the cylinder tube 2 is increased, and the piston 3 moves and the cylinder stroke changes due to the pressure difference in the region partitioned by the piston 3. To do. As shown in an enlarged view in FIG. 5, in the single-acting hydraulic cylinder 1 as in the present embodiment, when the piston rod 4 is in the extended state from the contracted state, the tube ( Since the internal pressure in the outer diameter D1) at that time rises at once when the piston 3 (exactly, the outer packing 5) passes, the outer diameter D2 of the cylinder tube 2 increases (D2> D1), and distortion occurs. Gauges 8, 9, and 10 detect strain. On the contrary, when the piston rod 4 is in the contracted state from the extended state, the internal pressure in the tube (the outer diameter D2 at that time) that was high before the piston 3 passes is reduced at once when the piston 3 passes through. The outer diameter D1 of the cylinder tube 2 is reduced (D1 <D2), and the strain gauges 8, 9, and 10 detect the strain.

  In this way, the strain gauges 8, 9, and 10 are attached, and the cylinder stroke is accurate even with the magnetic hydraulic cylinder 1 in which the proximity sensor cannot be installed by measuring which strain gauge is detected. Can be detected.

  Next, the result of measuring the strain amount of the strain gauges 8, 9, 10 by applying a load to the hydraulic cylinder 1 will be described.

  6 and 7 show the measuring device 13. The measuring device 13 includes a lifting platform 14 that can be moved up and down. The lift 14 includes a support 15 having four support bars 15a and a top plate 16 having a tube 16a into which each support 15 is inserted. On the top plate 16, a weight 17 for securing a minimum operating pressure is placed.

  The tip of the piston rod 4 of the hydraulic cylinder 1 is connected to the support base 15 side, and the base end side of the cylinder tube 2 is connected to the top plate 16. The cylinder hydraulic pipe 6 of the hydraulic cylinder 1 is connected to a hydraulic unit (not shown).

  With this configuration, when the hydraulic oil is fed from the hydraulic unit, as shown in FIG. 7, the hydraulic cylinder 1 is extended and the lifting platform 14 is raised, while the supply of hydraulic oil is stopped and the cylinder tube 2 is stopped. When the hydraulic oil is returned to the tank of the hydraulic unit, as shown in FIG. 6, the hydraulic cylinder 1 is contracted and the lifting platform 14 is lowered.

FIG. 8 shows the result of measurement using the measuring apparatus 13 configured as described above. The horizontal axis represents time (s), and the vertical axis represents stress (N / mm ² ) and hydraulic pressure (MPa).

First, at the time of full bottom at the start of operation, the hydraulic pressure is about 4 MPa to support the weight 17. The stress of the first to third gauges 10 is 0 N / mm ² .

  Next, the ascending operation is started. When the hydraulic motor of the hydraulic unit is driven and high-pressure hydraulic oil is fed into the cylinder tube 2 from the cylinder hydraulic pipe 6, the piston rod 4 starts to rise.

  Next, when hydraulic fluid is further fed, the stress of the first gauge 8 increases as the piston 3 approaches the first gauge 8.

Then, as shown in FIG. 2, when the hydraulic oil flows directly under the packing 5 after passing under the first gauge 8, the stress of the first gauge 8 becomes 12 to 13 N / mm ² .

When the hydraulic oil is further fed, as the piston 3 approaches the second gauge 9, the stress of the second gauge 9 increases, and after the packing 5 passes just below the second gauge 9, as shown in FIG. When the gas flows underneath, the stress of the second gauge 9 is also 12 to 13 N / mm ² .

  When the hydraulic oil is further fed, as the piston 3 approaches the third gauge 10, the force for pressing the compression coil spring 7 increases, and the pressure in the cylinder tube 2 increases as an operating resistance. For this reason, the stress of the third gauge 10 increases. In the first gauge 8 and the second gauge 9 as well, the stress gradually increases as the pressure in the cylinder tube 2 increases.

When the stroke end, the operation of the hydraulic cylinder 1 is stopped, as shown in FIG. 4, a packing 5 is when it reaches just below the third gauge 10, the stress of the third gauge 10 becomes 21~22N / mm ^2. On the other hand, the first gauge 8 and the second gauge 9 are 39 to 41 N / mm ² . Since the hydraulic oil returns from the relief valve (not shown) to the tank, the hydraulic pressure becomes the relief pressure (about 13 MPa). The stresses of the first gauge 8 and the second gauge 9 are determined by this relief pressure. Since there is no hydraulic oil directly under the third gauge 10 at the stroke end, the stress of the third gauge 10 is lower than the stress of the first gauge 8 and the second gauge 9.

Next, when the drive of the hydraulic unit is stopped, the lowering operation is started, and when the piston 3 starts to move, the value of the third gauge 10 is drastically reduced to 0 N / mm ² . Further, the first gauge 8 and the second gauge 9 are reduced to about 10 N / mm ² .

Furthermore, the stress of the second gauge 9 decreases from the time when the piston 3 is in front of the second gauge 9, and the packing 5 becomes 0 N / mm ² after passing directly under the second gauge 9.

Furthermore, the stress of the third gauge 10 decreases from the time when the piston 3 is in front of the third gauge 10, and the packing 5 becomes 0 N / mm ² after passing directly under the third gauge 10.

  In this way, by detecting the values of the strain gauges 8, 9, and 10, it is detected that the piston 3 has passed directly below the strain gauges 8, 9, and 10. For this reason, the cylinder stroke can be detected based on the positions of the strain gauges 8, 9, and 10.

-Tailgate lifter with hydraulic cylinder control device-
Next, the tailgate lifter 21 provided with the control device 20 for the hydraulic cylinder of the present embodiment will be exemplified. As shown in FIGS. 9 to 11, the tailgate lifter 21 is installed at a rear opening of a one-box car or the like, and allows a wheelchair or luggage to be put on the vehicle.

  The tailgate lifter 21 has a deck 22 that is parallel to the ground and is connected to a post 23. One end of a lift arm 24 is connected to the post 23, and the other end is supported by a support bracket 25 at the periphery of the rear opening of the vehicle body. The post 23 is connected to the compression arm 26 and the hydraulic cylinder 1. High pressure hydraulic oil is sent from the power unit 27 to the hydraulic cylinder 1. 10 and 11, when the hydraulic cylinder 1 is extended, the lift arm 24 pulls the post 23 and the deck 22 is raised. On the other hand, as shown in FIG. 9, the hydraulic cylinder 1 is contracted and the deck 22 is lowered by the action and weight of the compression coil spring 7.

  As shown in FIG. 12, the hydraulic cylinder control device 20 includes a controller 28 as detection means and speed adjustment means. The controller 28 serves as detection means for detecting a cylinder stroke when the piston 3 passes through a position corresponding to the position where the strain gauge 10 is attached, and the amount of strain of the strain gauge 10 changes. Further, it also serves as a speed adjusting means for adjusting the moving speed of the piston 3 in accordance with the detection result of the detecting means. In the tailgate lifter 21, at least the third gauge 10 is attached to the hydraulic cylinder 1 (that is, the third gauge 10 is attached near the stroke end). The first and second gauges 8 and 9 may be attached to detect the cylinder stroke.

  The hydraulic cylinder control device 20 includes a two-position switching solenoid valve 29 and a flow control valve 30. A signal from the strain gauge 10 is input to the controller 28, and a control signal is sent from the controller 28 to the solenoid valve 29. Specifically, as shown in FIG. 14, the controller 28 receives the gauge output of the third gauge 10 and operates the switch R <b> 1 to switch the solenoid valve 29.

  Next, the operation of the tailgate lifter 21 will be described.

  First, as shown in FIG. 9, in order to raise the deck 22 from the state where the deck 22 is placed on the ground, the power unit 27 is driven, and as shown in FIG. Feed in high pressure oil. Then, the hydraulic cylinder 1 is extended and the deck 22 is gradually raised.

  As shown in FIG. 10, the stress of the third gauge 10 changes before the stroke end, and the signal is sent to the controller 28. Then, the switch R1 is turned on, the solenoid valve 29 is moved, and the state shown in FIG. 13 is obtained.

  The high pressure oil from the power unit 27 is sent to the hydraulic cylinder 1 through the flow control valve 30 while the flow rate is reduced. For this reason, the ascending speed of the deck 22 is reduced from before the stroke end, and the shock at the stroke end is reduced. For this reason, an impact is transmitted to the wheelchair etc. which were mounted on the deck 22, and an uncomfortable feeling is not given.

  Therefore, according to the control apparatus 20 of the hydraulic cylinder according to the present embodiment, the strain gauges 8, 9, 10 are attached to the outer periphery of the cylinder tube 2, and the strain amount of the strain gauges 8, 9, 10 when the piston 3 passes is determined. By detecting the cylinder stroke from the change and adjusting the moving speed of the piston 3 in response to the detection signal, the position of the piston 3 can be accurately detected even when the cylinder tube 2 made of magnetic material is used. The speed of the piston 3 can be adjusted.

  Even if the cylinder tube 2 made of a ferromagnetic material is provided, it is possible to accurately detect the cylinder stroke and adjust the moving speed of the piston 3 by detecting changes in the strain amount of the strain gauges 8, 9, and 10. It can be done easily.

  Further, the change in the strain amount of the strain gauge 10 attached before the stroke end of the piston 3 is detected, and the flow rate of the working liquid to the hydraulic cylinder 1 is reduced, so that the piston 3 is moved before the stroke end. The impact at the stroke end can be reduced by slowing the moving speed.

(Other embodiments)
The present invention may be configured as follows with respect to the above embodiment.

  That is, in the above embodiment, the hydraulic cylinder is the hydraulic cylinder 1, but the liquid for adjusting the pressure is not limited to hydraulic oil, and may be water or the like.

  In the above embodiment, the hydraulic cylinder 1 is a single-acting type having only one cylinder hydraulic pipe 6, but may be a backward-acting hydraulic cylinder in which two cylinder hydraulic pipes 6 are connected. In the case of a return-acting hydraulic cylinder, the piston rod 4 in the tube that was lowered before passing through the piston 3 in either of the contracted state from the extended state or the contracted state from the extended state. Since the internal pressure of the cylinder tube 2 increases at once when the piston 3 passes, the outer diameter of the cylinder tube 2 increases, and the strain gauges 8, 9, and 10 detect the strain. Thus, since it is detected that the piston 3 has passed, the cylinder stroke can be detected by the detection means based on the positions of the strain gauges 8, 9, and 10.

  In the above embodiment, the control device 20 for the hydraulic cylinder is provided in the tail gate lifter 21. However, for example, the control device 20 is used for a gate that has an open position and a closed position in which an open horizontal gate is closed vertically. In this case, the hydraulic cylinder is of a reciprocating type, and the outer circumference of the cylinder tube 2 is adapted to correspond to both when the piston is in the open end stroke position and when the piston is in the close end stroke position. Alternatively, a strain gauge may be attached to the hydraulic cylinder to detect the end stroke and control the hydraulic cylinder. In this case, a three-position switching solenoid valve may be provided, and a hydraulic circuit and an electric circuit may be assembled so that the flow control valve acts in both opening and closing operations.

  Moreover, the position which pastes a strain gauge should just stick 1 sheet-multiple sheets according to the cylinder stroke to detect.

  Furthermore, in the said embodiment, although the cylinder tube 2 shall consist of carbon steel pipes, you may comprise with another magnetic body and may comprise with a nonmagnetic body.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or a use.

  As described above, the present invention is useful for a control device that controls the speed of a hydraulic cylinder such as a hydraulic cylinder or a hydraulic cylinder in accordance with the cylinder stroke.

It is sectional drawing which looked at the time of the shrinking | reduction of the hydraulic cylinder concerning embodiment of this invention from the side. FIG. 2 is a view corresponding to FIG. 1 illustrating a state in which a hydraulic cylinder is extended and a piston comes directly below a first gauge. FIG. 2 is a view corresponding to FIG. 1 illustrating a state in which a hydraulic cylinder is extended and a piston comes directly below a second gauge. FIG. 2 is a view corresponding to FIG. 1 showing a state in which a hydraulic cylinder is extended and a piston comes directly below a third gauge. It is sectional drawing which expands and shows the piston of a hydraulic cylinder, and its periphery. It is a front view which shows a measurement apparatus of a descent state partly broken. It is a front view which shows the measuring apparatus of a rising body partly fractured | ruptured. It is a graph which shows the measurement result by a measuring device. It is a side view which shows the fall state of a tailgate. It is a side view which shows the tailgate before the stroke end. It is a side view which shows the tailgate in a stroke end. It is a hydraulic circuit figure at the time of raising operation. It is a hydraulic circuit diagram before the stroke end. It is a sequence diagram of a solenoid valve.

Explanation of symbols

1 Hydraulic cylinder (hydraulic cylinder)
2 Cylinder tube 3 Piston 4 Piston rod 8 First gauge (strain gauge)
9 Second gauge (strain gauge)
10 Third gauge (strain gauge)
20 Hydraulic cylinder control device (hydraulic cylinder control device)
28 controller (detection means, speed adjustment means)

Claims (2)

In a hydraulic cylinder control device for controlling a hydraulic cylinder comprising a cylinder tube and a piston rod having a piston at one end and the piston sliding inside the cylinder tube,
A strain gauge attached to the outer periphery of the cylinder tube;
Detecting means for detecting a cylinder stroke by changing a strain amount of the strain gauge when the piston passes a position corresponding to the strain gauge;
A hydraulic cylinder control device comprising: a speed adjusting unit that adjusts a moving speed of the piston in accordance with a detection result of the detecting unit. In the control apparatus of the hydraulic cylinder according to claim 1,
The strain gauge is attached in front of the stroke end of the piston, and the speed adjusting means responds to the detection result of the detecting means that detects the change in the strain amount of the strain gauge, and the speed adjusting means A control device for a hydraulic cylinder, characterized in that the flow rate is reduced.

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