JP2007278477A - Method of detecting gas in hydraulic cylinder and hydraulic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting entrained gas in a hydraulic cylinder in a simple method and a hydraulic apparatus provided with the method. <P>SOLUTION: The method of detecting gas in the hydraulic cylinder is applied to detect gas in the hydraulic cylinder of the hydraulic apparatus 1 which comprises a hydraulically controlled controller 2, a servo driver 51 controlled by a controller 2, a servo motor 50 driven by the servo driver 51, a hydraulic pump 52 supplying oil by the servo motor 50, a hydraulic cylinder arrangement 3 driven by oil supplied and a sensor 6 which detects amount of lift or associated amount of lift of the hydraulic cylinder arrangement 3 and sends out data of amount of lift or associated amount of lift to the controller 2. The method of detecting gas in the hydraulic cylinder includes the steps of processing the amount of variation in lift speed based upon the amount of lift or an associated amount of lift sent out from the sensor 6, acquiring a signal associated with the amount of gas in the hydraulic cylinder 31 based on the variation and sending the signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for detecting gas contamination in a hydraulic cylinder and a hydraulic apparatus having means for detecting gas contamination.

  The hydraulic device supplies oil (working fluid) in the tank to the hydraulic cylinder device, raises the lift of the hydraulic cylinder device, discharges oil from the hydraulic cylinder device into the tank, and lowers the lift. When gas (air) is mixed in the hydraulic device, the lift hunts, and the behavior at the time of starting and stopping becomes unstable.

  Also, when the hydraulic cylinder device uses a single-acting cylinder and is used under low pressure, if the mixed gas is distributed in the oil as microbubbles, it will lead to the generation of vibration and noise due to cavitation, and the pump etc. There is a risk of affecting the durability of being easily damaged.

  As a cause of gas mixing into the hydraulic cylinder device, it is conceivable that gas is sucked from the pump due to poor assembly work at the time of equipment manufacture, oil reduction, or the like. However, since it is difficult to completely prevent gas mixture, it is important to detect whether gas is mixed in the hydraulic cylinder device.

  Patent Document 1 proposes a method in which a light projecting unit and a light receiving unit are installed facing each other in the middle of a pipe through which oil passes, and an air (gas) amount is detected based on an output result of the light receiving unit. Since the light from the light projecting unit is scattered by the bubbles and does not reach the light receiving unit, the amount of light received by the light receiving unit is inversely proportional to the number of bubbles. As a result, the amount of gas mixed in the oil is detected from the amount of light received by the light receiving unit.

In Patent Document 2, the bulk elastic modulus of oil in the device is obtained from the relationship between the piston operation amount of the hydraulic cylinder device and the hydraulic pressure, and the obtained bulk elastic modulus, the bulk elastic modulus of oil, and the bulk elasticity of air (gas). A method for obtaining an air (gas) mixing rate using a coefficient is proposed.
JP-A-6-11375 JP 2000-94052 A

  In Patent Document 1 described above, a light projecting unit and a light receiving unit are installed in order to detect the amount of gas mixed in the apparatus. In addition to the hydraulic cylinder device, a device for projecting and receiving light and a space for arranging the device are required.

  Further, in Patent Document 2 described above, the bulk elastic modulus is obtained from the piston operation amount of the hydraulic cylinder device and the oil pressure of the oil in the device, and the bulk elastic modulus, the general bulk elastic coefficient of oil, and the bulk elastic coefficient of air, Is used to determine the gas mixing rate. Since a device for obtaining the bulk modulus of oil is required, the device becomes complicated.

  The present invention has been made in view of the above problems, and an object thereof is to provide a method for detecting gas contamination in a hydraulic cylinder by a simple method.

  It is another object of the present invention to provide a hydraulic apparatus having simple means for detecting gas mixture in the hydraulic cylinder.

  The method for detecting gas in a hydraulic cylinder according to the present invention includes a hydraulic control controller, a servo driver controlled by the controller, a servo motor driven by the servo driver, a hydraulic pump that supplies oil by the servo motor, and oil supplied. A method for detecting gas in a hydraulic cylinder of a hydraulic system comprising a driven hydraulic cylinder device and a sensor for detecting a lift amount or lift-related amount of the hydraulic cylinder device and sending the lift amount or lift-related amount data to the controller. Determining a lift speed change amount based on the lift amount or the lift-related amount sent from the sensor, obtaining a signal related to the gas amount in the hydraulic cylinder based on the change amount, and And a transmitting step.

  In the gas detection method in the hydraulic cylinder of the present invention, it is only necessary to detect a lift amount or a lift-related amount capable of obtaining a lift speed of a hydraulic cylinder device that is hydraulically controlled, and to perform a simple calculation step. Gas contamination in the hydraulic cylinder can be detected.

  In addition, the means for obtaining the lift amount or lift-related amount is usually attached to a hydraulic device using a servo driver. For this reason, it is not necessary to attach a special means and apparatus. Here, the lift-related amount refers to the lift amount of other parts and parts that are driven by the cylinder and move relative to the lift amount of the cylinder, in addition to the lift amount of the cylinder.

  The step of determining the amount of change used in the hydraulic cylinder gas detection method of the present invention includes the step of determining the actual speed of the lift based on the lift amount or lift-related amount, and the theoretical speed and actual speed based on the command of the hydraulic controller. It is preferable that the method includes a step of obtaining a difference. The actual speed when the lift actually moves is obtained from the lift amount or lift-related amount, and is compared with the theoretical speed based on the command of the hydraulic control controller, so that it is used as a judgment material for gas contamination in the hydraulic cylinder. Since the speed can be obtained by a generally used mathematical expression, gas contamination can be easily detected.

  In the step of obtaining a signal used in the hydraulic cylinder gas detection method of the present invention, it is preferable to obtain a signal when the amount of change is equal to or greater than a predetermined value. A predetermined value as a reference for determining gas mixing is set in advance, and it is determined whether or not gas is mixed in the hydraulic cylinder by comparing with a change amount, thereby detecting gas mixing. Since only the change amount is compared with the predetermined value, gas mixture can be detected quickly.

  The hydraulic apparatus of the present invention includes a hydraulic control controller, a servo driver controlled by the controller, a servo motor driven by the servo driver, a hydraulic pump that supplies oil by the servo motor, and a hydraulic pressure that is driven by the supplied oil. A hydraulic device comprising a cylinder device and a sensor for detecting a lift amount or lift-related amount of the hydraulic cylinder device and sending the lift amount or lift-related amount data to the controller, wherein the controller is sent from the sensor Change amount obtaining means for obtaining a change amount of the lift speed based on the lift amount or the lift related amount, signal obtaining means for obtaining a signal related to the gas amount in the hydraulic cylinder based on the change amount, and transmitting the signal And a signal transmitting means.

  In the hydraulic device of the present invention, a sensor for detecting the lift amount of the hydraulic cylinder device that is hydraulically controlled or an amount related to the lift is installed, and means for detecting and judging gas mixing based on a signal from the sensor is provided. Since only the controller is included, it is possible to detect gas contamination with a simple configuration.

  The change amount obtaining means for obtaining the change amount used in the hydraulic device of the present invention includes an actual speed obtaining means for obtaining an actual lift speed based on the lift amount or the lift related amount, and a theoretical speed and an actual speed based on a command from the hydraulic controller. It is preferable to comprise a speed change amount obtaining means for obtaining the difference between the two. The means for determining the actual speed when the lift actually moves from the lift amount or lift-related quantity and the means for comparing with the theoretical speed based on the command of the hydraulic controller are used as judgment materials for gas contamination in the hydraulic cylinder. . Since the speed can be obtained by a generally used mathematical expression, gas contamination can be easily detected.

  It is preferable that the signal acquisition means for obtaining a signal used in the hydraulic apparatus of the present invention obtains a signal when the amount of change is equal to or greater than a predetermined value. By simply setting a predetermined value as a reference for determining gas mixing, gas mixing is determined, so that simple and quick detection can be performed.

  According to the hydraulic cylinder gas detection method and the hydraulic apparatus having the gas detection means of the present invention, the sensor is installed at an appropriate position, and the lift speed is obtained based on the lift amount detected from the sensor or the amount related to the lift. Because the difference between the actual speed at which the lift has actually moved and the theoretical speed instructed by the lift are obtained as the amount of change in the lift speed, the gas mixture is detected by a simple method to determine the gas mixture based on the difference. Yes. If gas contamination can be known in advance, it is possible to prevent deterioration of workability due to lift hunting, starting movement, and unstable behavior at the time of stopping, and also preventing failure of the apparatus.

  Hereinafter, the present invention will be specifically described with reference to examples.

(Example)
FIG. 1 shows a schematic configuration diagram of a hydraulic apparatus 1 having a hydraulic cylinder gas detection means of the present embodiment.

  The hydraulic device 1 detects the height of the lift 30 of the hydraulic cylinder device 3 by detecting the height of the hydraulic control device 2, the servo device 5 that supplies and discharges oil to and from the hydraulic cylinder device 3 through the pipe 4 under the control of the controller 2. It consists of a height sensor 6 that sends out the height.

  The controller 2 includes an actual speed acquisition means (not shown) for obtaining the actual speed of the lift vertically moved based on the height of the lift 30 sent from the height sensor 6, and a command issued to the servo driver 51 of the servo device 5. A speed difference acquisition means (not shown) for obtaining a difference between a theoretical speed based on the actual speed and an actual speed, a signal acquisition means (not shown) for determining that a signal is output when the difference is equal to or greater than a reference value, and a signal It comprises signal transmitting means (not shown) for transmitting.

  The hydraulic cylinder device 3 includes a lift 30 that moves up and down, a hydraulic cylinder 31 that is disposed under the lift 30 and expands and contracts by supplying and discharging oil and moves the lift 30 up and down, and a lift guide 32 that guides the lift 30 up and down. Consists of. The hydraulic cylinder 31 includes a first cylinder 310 installed on the floor 7, a second cylinder 311 slidably inserted into the first cylinder 310, and a third cylinder slidably inserted into the second cylinder 311. 312.

  The servo device 5 includes a servo driver 51 that rotates and controls the servo motor 50 based on a command from the controller 2, a hydraulic pump 52 that supplies and discharges oil to and from the hydraulic cylinder device 3 by the rotation of the servo motor 50, and a hydraulic pump 52 includes a tank 53 in which oil supplied and discharged is stored.

  The height sensor 6 is installed on the floor 7 on which the hydraulic cylinder device 3 is installed, and the lift 30 detects the height based on the lowest position in the driving direction of the hydraulic cylinder 31 by an optical position sensor. The height is sent to the controller 2. The hydraulic device 1 when the lift 30 of the hydraulic cylinder device 3 is at the lowest position is shown in FIG. The third cylinder 312 is inserted into the second cylinder 311, and the second cylinder 311 into which the third cylinder 311 is inserted is inserted into the first cylinder 310.

  In the hydraulic apparatus 1 according to the present embodiment, an operator (not shown) rides on the lift 30 to place tools and parts necessary for the work, and changes the height of the lift 30 to the controller 2 as necessary. Issue a command. The controller 2 issues a command to the servo driver 51 based on a command from the operator, controls the rotation of the servo motor 50, and the rotation of the servo motor 50 causes the hydraulic cylinder 31 of the hydraulic cylinder device 3 through the pipe 4 from the tank 53. Oil is supplied and discharged to the height of the lift 30.

  The controller 2 calculates a theoretical speed when the lift 30 moves based on a command from the operator, and sends the height at which the lift 30 is actually moved up and down from the height sensor 6 to differentiate the height with respect to time. Thus, the actual speed can be obtained (actual speed acquisition means). When the difference between the theoretical speed and the actual speed (speed difference acquisition means) is equal to or greater than the reference value, a warning signal is transmitted to the operator because there is a possibility of gas mixing in the hydraulic cylinder 31. (Signal transmission means).

  In the hydraulic cylinder gas detection means of this embodiment, the hydraulic controller 2 is provided with a CPU, RAM, ROM, etc., and performs signal processing by a program stored in advance in the ROM to detect gas contamination in the hydraulic cylinder. . FIG. 3 is a flowchart showing the steps performed by the controller 2.

  In step S1, an instruction from the lift 30 is acquired. In step S2, a command is issued to the servo driver 51 of the servo device 5 according to the instruction obtained in S1. In S3, the theoretical speed of the lift 30 based on the command is acquired.

  Step S4 is a process in which the servo device 5 drives the hydraulic cylinder device 3, and details are not shown. The servo driver 51 controls the rotation of the servo motor 50 based on the command, and the hydraulic pump 52 supplies and discharges the oil in the tank 53 to the hydraulic cylinder 31 of the hydraulic cylinder device 3.

  In step S <b> 5, the height of the lift 30 of the hydraulic cylinder device 3 changed based on a command from the servo device 5 is acquired from the height sensor 6. In step S6, the height data is differentiated with respect to time, and the actual speed of the lift 30 actually moved is calculated. In step S7, the difference between the theoretical speed and the actual speed of the lift 30 is calculated. In step S8, if the difference is larger than the reference value, the process proceeds to step S9 to acquire a signal. If the difference is not exceeded, the program is terminated. In step S10, a warning is issued and the program is terminated.

  In the hydraulic cylinder gas detection means of this embodiment, steps S1 to S10 can be repeated as necessary when the hydraulic device 1 is driven.

  When the servo mechanism 5 used in the hydraulic apparatus 1 of the present invention receives a command from the controller 2, it can immediately move to the commanded height. Therefore, if gas is mixed in the hydraulic cylinder 31 of the hydraulic cylinder device 3, the gas is compressed more easily than oil, so the gas is compressed by the influence of the pressure accompanying the movement and the load applied to the lift 30, and moves after the movement stops. The lift 30 is released from the accompanying pressure and returns to the normal volume, and the lift 30 causes overshoot and variation.

  FIG. 4 shows a graph regarding the theoretical speed and the actual speed indicating the normal state of the hydraulic device 1 in which no gas is mixed in the hydraulic cylinder 31, and a graph regarding the theoretical speed and the actual speed when gas is mixed. As shown in FIG. 4 and 5, it can be seen that when gas is mixed in the hydraulic cylinder 31, the difference (variation) between the theoretical speed and the actual speed is large. Since there is a difference in speed even when no gas is mixed, the reference value is determined in consideration of the difference between the theoretical speed and the actual speed when no gas is mixed.

  In the hydraulic apparatus 1 having the gas detection means in the hydraulic cylinder of this embodiment, the speed at which the lift 30 is actually moved can be calculated by obtaining the height of the lift 30 of the hydraulic cylinder apparatus 3, and the difference from the theoretical speed can be calculated. It is possible to detect gas contamination in the hydraulic cylinder 31 by comparing the above. The detection program stored in the controller 2 is simple, and the cost including the installation of the height sensor 6 is low. As a result, by detecting the gas mixture in the hydraulic cylinder 31, it is possible to prevent the operator from deteriorating workability and to prevent the hydraulic apparatus 1 from being broken.

(How to obtain the reference value)
An example of how to obtain a reference value for determination when the hydraulic device 1 detects gas contamination will be described.

  The reference values are determined when the load is not applied to the lift 30 and when the load is not applied to the lift 30 in the state in which no gas is mixed into the hydraulic cylinder 31 and the state in which gas is mixed in the hydraulic cylinder 31. An experiment is performed, and the speed is determined from the theoretical speed and the actual speed obtained based on the height of the height sensor 6.

  Actually, the following six patterns were performed. The graph data of FIGS. 6-11 were obtained, respectively. The theoretical speed was constant at 150 mm / sec for all patterns.

1. Gas volume 0cc, load 0kg (Fig. 6)
2. Gas volume 30cc, load 0kg (Figure 7)
3. Gas amount 40cc, load 0kg (Fig. 8)
4). Gas amount 0cc, load 700kg (Fig. 9)
5). Gas volume 200cc, load 700kg (Figure 10)
6). Gas amount 300cc, load 700kg (Figure 11)
From the six graph data, variation in each speed from the ascending speed, descending speed, and theoretical speed in each combination of gas mixing amount and load shown in Table 1 was obtained.

  FIG. 12 is a graph showing the ascending speed, descending speed, and variation between the ascending and descending theoretical speed when there is no load, and FIG. 12 shows the ascending speed, descending speed, and FIG. 13 is a graph showing the variation between the theoretical speeds when ascending and when descending.

  As a result, before starting work without placing anything on the lift 30, there is a possibility of gas mixing if the difference between the theoretical speed and the actual speed is 40 (mm / sec) or more, and the lift 30 has a certain load. In some cases, gas may be mixed if the difference between the theoretical speed and the actual speed is 30 (mm / sec) or more. The reference value is 40 (mm / sec) when gas mixing is detected when no load is applied to the lift 30, and 30 (mm / sec) when the lift 30 is loaded (working, etc.). ).

  As mentioned above, although the suitable Example of this invention was described, this invention is not limited to the said Example. For example, the height sensor 6 is not limited to an optical type, and is not limited to detecting the height, but detects the speed of the lift 30 itself or is not related to the height sensor but is relatively related to the lift amount. It is sufficient if the speed can be detected. The method for obtaining the reference value for detecting gas contamination in the hydraulic cylinder 31 can also be determined uniquely without considering the presence or absence of a load on the lift 30.

1 is a schematic configuration diagram of a hydraulic apparatus 1 having a hydraulic cylinder gas detection means 1 of the present embodiment. It is a schematic block diagram of the hydraulic apparatus 1 when the lift 30 of FIG. 1 is the lowest. It is a flowchart of the gas detection means 1 in a hydraulic cylinder of a present Example. It is a graph regarding the theoretical speed and the actual speed when the gas is not mixed in the hydraulic device 1 of the present embodiment. It is a graph regarding the theoretical speed and the actual speed when gas is mixed in the hydraulic device 1 of the present embodiment. It is a graph of the actual speed and lift height when the gas amount of the hydraulic device 1 of the present embodiment is 0 cc and there is no load. It is a graph of the actual speed and lift height in the case of 300cc of gas amount of the hydraulic apparatus 1 of a present Example, no load. It is a graph of the actual speed and lift height in the case of 400cc of gas amount of the hydraulic apparatus 1 of a present Example, no load. It is a graph of the actual speed and the height of a lift when the gas amount of the hydraulic device 1 of this embodiment is 0 cc and the load is 700 kg. It is a graph of the actual speed and lift height when the gas amount is 200 cc and the load is 700 kg of the hydraulic device 1 of the present embodiment. It is a graph of the actual speed and lift height when the gas amount is 300 cc and the load is 700 kg of the hydraulic device 1 of the present embodiment. It is a graph regarding the variation in the actual speed for every gas mixture amount in the case of no load in the hydraulic device 1 of a present Example, and theoretical speed, and an actual speed. It is a graph regarding the variation in the actual speed for every gas mixture amount in the case of the load of 700 kg in the hydraulic apparatus 1 of a present Example, and theoretical speed, and an actual speed.

Explanation of symbols

1: Hydraulic device 2: Hydraulic control controller 3: Hydraulic cylinder device 4: Piping 5: Servo device 6: Height sensor 7: Floor 30: Lift 31: Hydraulic cylinder 32: Lift guide 50: Servo motor 51: Servo driver 52: Hydraulic pump 53: Tank 310: First cylinder 311: Second cylinder 312: Third cylinder

Claims (6)

Hydraulic control controller, servo driver controlled by the controller, servo motor driven by the servo driver, hydraulic pump supplying oil by the servo motor, hydraulic cylinder device driven by supplied oil, and hydraulic cylinder device A method for detecting gas in a hydraulic cylinder of a hydraulic device, comprising a sensor for detecting a lift amount or a lift-related amount of the engine and sending the lift amount or lift-related amount data to the controller,
Obtaining a change amount of the lift speed based on the lift amount or the lift-related amount sent from the sensor; obtaining a signal related to the gas amount in the hydraulic cylinder based on the change amount; and transmitting the signal. A gas detection method in a hydraulic cylinder, comprising: a step.   The step of obtaining the change amount includes a step of obtaining an actual speed of the lift based on the lift amount or the lift-related amount, and a step of obtaining a difference between the theoretical speed based on the command of the hydraulic controller and the actual speed. The method for detecting gas in a hydraulic cylinder according to claim 1.   The hydraulic cylinder gas detection method according to claim 1 or 2, wherein the step of obtaining the signal obtains the signal when the amount of change is equal to or greater than a predetermined value. Hydraulic control controller, servo driver controlled by the controller, servo motor driven by the servo driver, hydraulic pump supplying oil by the servo motor, hydraulic cylinder device driven by supplied oil, and hydraulic cylinder device A hydraulic device comprising a sensor for detecting a lift amount or a lift-related amount and sending the lift amount or lift-related amount data to the controller,
The controller includes a change amount obtaining means for obtaining a change amount of the lift speed based on the lift amount or the lift related amount sent from the sensor, and a signal for obtaining a signal related to the gas amount in the hydraulic cylinder based on the change amount. A hydraulic apparatus comprising: an acquisition unit; and a signal transmission unit that transmits the signal.   The change amount obtaining means for obtaining the change amount includes an actual speed obtaining means for obtaining an actual lift speed based on the lift amount or the lift-related amount, and a difference between the theoretical speed based on the command of the hydraulic controller and the actual speed. The hydraulic apparatus according to claim 4, further comprising a speed change amount obtaining means for obtaining   The hydraulic apparatus according to claim 5, wherein the signal acquisition unit that obtains the signal obtains the signal when the amount of change is equal to or greater than a predetermined value.

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