JP2012087541A - Operation speed control device of work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation speed control device of a work machine, with which the amount of time and labor at the time of assembly can be reduced and assembly work can be conducted efficiently.SOLUTION: An operation speed control device comprises: operation speed mode setting means, such as a switch 37, which sets the operation speed of a hydraulic actuator; and operation signal changing means 39 which changes a proportionality constant of, or the maximum value of, a command current value I corresponding to the operation amount of an electric lever 36 in accordance with the operation of the operation speed mode setting means, such as the switch 37. At the time of assembly or parts replacement, the operation speed mode setting means, such as the switch 37, is operated to thereby reduce the proportionality constant of, or the maximum value of, the command current value I corresponding to the operation amount of the electric lever (36), and thus, the hydraulic actuator can be made to move at a slow speed without requiring delicate operation.

Description

  The present invention relates to a working machine such as a hydraulic excavator using an electric motor as a power source, which can suitably control the speed of a hydraulic actuator during maintenance of assembly or the like.

  In general, in a working machine such as a hydraulic excavator used for excavation, the control valve spool is moved in accordance with the operation amount of the operation lever, and the opening area of the control valve flow path is changed, thereby adjusting the lever operation amount. The corresponding operating speed is obtained.

  Moreover, the working machine described in Patent Document 1 realizes an actuator operating speed that matches the work content by changing the discharge amount of the hydraulic pump in accordance with the lever operation amount. In general, the working machine uses an engine as a prime mover, and as described in Patent Document 2, control is performed to change the engine rotation speed in accordance with the operation amount of the operation lever. In the case of controlling the rotational speed of the engine in this way, if the rotational speed of the engine is decreased, the rotational speed of the hydraulic pump also decreases and the discharge amount also decreases. Is often operated at a low engine speed.

  In such a working machine, as an operation device, there is an electric lever that generates an electric signal as an operation amount in addition to an operation lever that generates a pilot hydraulic pressure as an operation signal. In the case of an electric lever, the speed of the hydraulic actuator is a speed corresponding to an electric operation signal proportional to the operation amount that is the output of the electric lever. That is, an electrical operation signal output from the electric lever is input to the controller, and the controller outputs an electrical operation signal (current) proportional to the operation amount to the solenoid of the proportional solenoid valve. In the proportional solenoid valve, a flow passage opening having an area corresponding to the current to the solenoid is formed, and a pilot pressure corresponding to the flow passage opening area is applied to the operation chamber of the control valve, and in response to the pilot pressure in the control valve. The hydraulic fluid with the specified flow rate is supplied to the hydraulic actuator.

  In a working machine using an electric lever as an operating lever in this way, as means for adjusting the speed of the actuator with respect to the operating amount of the electric lever, Patent Document 3 discloses a left and right operation that is performed in the output circuit of the turning electric lever. An electrohydraulic circuit for balancing the turning speed is disclosed. This electrohydraulic circuit includes a proportional solenoid valve connected to each of the two operation chambers of the turning control valve, and has a configuration in which an operation current is applied from the controller to each proportional solenoid valve. An adjustment resistor that can be connected and separated in parallel to the solenoid of each proportional solenoid valve is provided. Then, with respect to the solenoids of the two proportional solenoid valves, the resistance value of the adjusting resistor connected in parallel is increased / decreased to adjust the current from the controller to the solenoids of the two proportional solenoid valves, thereby turning left and right The speed is adjusted to be the same.

JP-A-2-125322 JP 2006-83829 A Japanese Utility Model Publication No. 6-12558

  As a conventional working machine, there is a working machine using an AC electric motor driven by a power source of a constant frequency as a power source instead of an engine as a power source for driving a hydraulic pump. Such a working machine is, for example, a large hydraulic excavator that performs ore digging of ore, etc., for example, a 6.6 kV AC power transmitted from a power plant is directly connected to the electric motor of the working machine by a cable, and the electric motor is It is driven by this power source.

  Since such a large excavator is over-restricted in terms of weight and size in the assembled state, the front is disassembled into a boom, an arm and a bucket and transported, and assembled at the work site. This assembly is performed using a crane, and when assembling the front, the boom is hung by the crane and assembled to the already assembled upper swing body. When connecting the boom cylinder to the boom, the mechanics pin-connect one end of the boom cylinder to the upper swing body, and then operate the boom cylinder operation lever to adjust the boom cylinder extension degree. The position of the pin hole at the tip of the boom cylinder is aligned with the pin hole of the boom cylinder, and the boom cylinder is connected to the boom by the pin when the position of the pin hole matches. Also, the arm is connected to the boom by aligning the pin hole of the boom with the pin hole of the arm while the mechanic adjusts the extension degree of the boom cylinder and the turning of the upper turning body. Further, the connection of the arm cylinder to the arm and the connection of the bucket cylinder to the bucket are similarly performed by adjusting the degree of extension of the arm cylinder and the bucket cylinder to align the pin holes.

  However, in the case of a working machine using an AC electric motor driven by a constant frequency power source as a prime mover, not only the electric motor but also the hydraulic pump is driven at a constant rotational speed. For this reason, the operation speed of the hydraulic actuator such as a hydraulic cylinder is controlled solely by adjusting the operation amount of the electric lever. The flow rate of the hydraulic oil in the control valve in response to the operation signal of the electric lever is set based on the operation speed of the hydraulic actuator in consideration of the efficiency in work such as excavation on site.

  However, when assembling the hydraulic excavator, if the pin holes are aligned by adjusting the degree of extension of the boom cylinder, arm cylinder, bucket cylinder, etc., it is necessary to adjust the position very finely. For this reason, it is necessary to cause the hydraulic cylinder to expand and contract at a low speed. However, such a low-speed expansion / contraction operation requires the lever to be moved very delicately, requires a high level of skill for maintenance personnel, and requires a lot of labor and time.

  In order to solve this problem, a power supply device that can change the frequency is used as the power source of the electric motor, the rotation speed of the electric motor can be changed by frequency control, and the electric motor is operated at a low speed during assembly. It is also possible to reduce the speed of the actuator by reducing the hydraulic pump flow rate. However, as described above, in the case of a hydraulic excavator using an AC electric motor used in open pit mining as a prime mover, the power supplied from the power plant at the site is, for example, 6.6 kV and a high voltage. For this reason, in order to perform the current frequency control to control the rotation of the electric motor, it is necessary to reduce the power supply voltage and use a semiconductor device for a large current, which makes the device expensive and large, which is not realistic. .

  On the other hand, it is conceivable to provide an adjustment resistor that can be connected in parallel to the solenoid of the proportional solenoid valve as described in Patent Document 3. However, in such a configuration in which the adjusting resistor is inserted, the current value input to the solenoid of the proportional solenoid valve (that is, the current value obtained by subtracting the current shunted to the adjusting resistor from the output current of the controller) is directly observed by the controller. Therefore, setting this current value to an actuator speed (low speed) suitable for assembly requires trial and error and takes time and effort. In addition, after adjusting the speed so that it is suitable for assembly by adding an adjusting resistor, it is necessary to investigate whether the adjusting resistor or the proportional solenoid valve is the cause when a failure occurs. This will also increase the amount of time required for repairs such as replacement.

  In view of the above problems, an object of the present invention is to provide an operating speed control device for a work machine that can reduce the labor and time during assembly and can efficiently perform assembly and parts replacement work.

The operating speed control device for a work machine according to claim 1 is:
An AC electric motor driven by a constant frequency power supply;
A hydraulic pump driven by the electric motor;
A hydraulic actuator that is operated by hydraulic oil discharged from the hydraulic pump;
A control valve for controlling the amount of hydraulic fluid flowing to the hydraulic actuator;
A proportional solenoid valve for adjusting the operating pressure of the control valve;
An electric lever provided for operating the hydraulic actuator and outputting an electric signal as an output value;
In an operating speed control device for a working machine, comprising a controller for causing a command current value corresponding to an operation amount of the electric lever to flow through a solenoid of the proportional solenoid valve,
An operating speed mode setting means for setting an operating speed mode of the hydraulic actuator;
And an operation signal changing means for changing a proportional constant or maximum value of the command current value corresponding to the operation amount of the electric lever by operating the operating speed mode setting means.

The operation speed control device for a work machine according to claim 2 is the operation speed control device for a work machine according to claim 1,
The operating speed mode setting means is a switch or a connector that can be connected and disconnected.

The operation speed control device for a work machine according to claim 3 is the operation speed control device for a work machine according to claim 1,
The operating speed mode setting means is a variable resistor capable of continuously adjusting the relationship between the operation amount of the operation lever and the command current value.

  According to the first aspect of the present invention, when the work machine is assembled or the parts are replaced, the command current value proportional constant corresponding to the operation amount of the operation lever is set by the operation speed mode setting means to the low speed mode. Or, change the maximum value to a lower value. As a result, the ratio of the speed of the hydraulic actuator to the lever operation amount can be reduced, or the maximum speed can be reduced. This eliminates the need for a fine lever operation, and facilitates the pin hole alignment and the like required for assembly and component replacement. For this reason, the maintenance staff has less labor and can assemble the work machine and replace the parts in a shorter time than before.

  Further, in the present invention, since the command current value itself supplied to the solenoid of the proportional solenoid valve can be reduced, this command current value itself is displayed on, for example, a monitor to monitor the command current value and the hydraulic actuator. The correspondence can be confirmed while comparing the speed. For this reason, if a problem occurs in the proportional solenoid valve system, whether the command system including the controller or the proportional solenoid valve itself is defective if the operation status of the proportional solenoid valve is monitored while monitoring the command current value. Can be quickly determined, and maintenance work is facilitated.

  According to the second aspect of the present invention, since the work mode can be set by turning on / off the switch or connecting / disconnecting the connector, the work speed mode can be switched relatively easily.

  According to the invention of claim 3, since the operation speed mode setting means is constituted by the variable resistance, the proportional constant or the maximum value of the command current value for the proportional solenoid valve corresponding to the operation amount of the operation lever is continuously changed. Can do. For this reason, it becomes possible to adjust the speed of the hydraulic actuator at a suitable speed according to the characteristics that differ depending on the actual machine and the individuality of the maintenance personnel.

It is a side view which shows an example of the working machine with which this invention is applied. 1 is an electrohydraulic circuit diagram showing an embodiment of an operating speed control device for a working machine according to the present invention. It is a functional block diagram which shows the specific example of the operating speed control apparatus of the working machine of FIG. It is a graph explaining the effect | action of the operating speed control apparatus of the working machine of FIG. It is a functional block diagram which shows other embodiment of this invention. It is a graph explaining the effect | action of the operating speed control apparatus of the working machine of FIG. It is a functional block diagram which shows other embodiment of this invention. It is a functional block diagram which shows other embodiment of this invention.

  FIG. 1 is a side view showing a hydraulic excavator as an example of a working machine to which the present invention is applied. Reference numeral 1 denotes a lower traveling body. The lower traveling body 1 has drive wheels 3 that are driven by a traveling motor (not shown) made of a hydraulic motor attached to rear portions of left and right side frames 2 constituting a track frame. A driven wheel 4 is attached to the front portion of the frame 2 and a crawler belt 5 is hung around the driving wheel 3 and the driven wheel 4.

  Reference numeral 6 denotes an upper swing body installed on the lower traveling body 1 via a swing device 7. The turning device 7 has a turning motor (not shown) made of a hydraulic motor. Mounted on the upper swing body 6 are a cab 9, a power unit 10 including an electric motor 20, a hydraulic pump 22, a pilot hydraulic pump 23, and an oil tank 24 shown in the electrohydraulic circuit of FIG. 2.

  Reference numeral 11 denotes a working device attached to the upper swing body 6. The working device 11 is attached to the upper swing body 6 so as to be able to move up and down by a boom cylinder 12 which is a hydraulic cylinder, and is attached to the tip of the boom 13 so as to be vertically rotatable by an arm cylinder 14 which is a hydraulic cylinder. And a loader bucket 17 that is rotatably attached to a tip of the arm 15 by a bucket cylinder 16 that is a hydraulic cylinder. Reference numeral 18 denotes a cable for supplying power to an AC electric motor 20 which is a prime mover of the power unit 10. For example, 6.6 kV AC power is supplied to the electric motor 20 by the cable 18.

  In FIG. 2, reference numeral 21 denotes a hydraulic circuit including the electric motor 20, a hydraulic pump 22, a pilot hydraulic pump 23, an oil tank 24, and the like. Reference numerals 25 and 26 are relief valves for setting the maximum pressure of the discharge hydraulic pressure of the hydraulic pumps 22 and 23, respectively. Reference numeral 12 denotes the above-described boom cylinder, which is a hydraulic cylinder shown as an example of a hydraulic actuator. Reference numeral 27 denotes a control valve for the boom cylinder 12, and reference numerals 28 and 29 denote proportional solenoid valves which are pilot valves for the control valve 27.

  The proportional solenoid valves 28 and 29 form flow passage opening areas corresponding to the currents to the respective solenoids 28a and 29a, and thus the pilot pressure oil supplied from the pilot hydraulic pump 23 to the operation chambers 27a and 27b of the control valve 27, respectively. By controlling the hydraulic pressure, the control valve 27 is switched and the flow rate of hydraulic oil from the hydraulic pump 22 to the boom cylinder 12 is controlled, thereby controlling the operating direction and operating speed of the boom cylinder 12. is there.

  Reference numerals 30 and 31 denote hydraulic lines between the boom cylinder 12 and the control valve 27, and reference numerals 32 and 33 denote relief valves provided between the hydraulic lines 30 and 31 and the oil tank 24. These relief valves 32 and 33 prevent the hydraulic pressure in the hydraulic lines 30 and 31 from becoming excessive.

  Reference numeral 35 denotes a controller of the work machine, and as shown in the drawing, the control valve 27 is switched and controlled by supplying current to the solenoids 28a and 29a of the proportional solenoid valves 28 and 29, so that various hydraulic actuators such as the boom cylinder 12 are provided. The control is performed. Reference numeral 36 denotes an electric lever for operating the boom cylinder 12, and outputs an operation electric signal (voltage) corresponding to the operation amount to the controller 35. Reference numeral 37 denotes a switch added according to the present invention. This switch 37 turns on / off an electrical signal to the controller 35 and sets an operation speed mode of the hydraulic actuator. The controller 35 refers to the load signals (pressure signals) of the hydraulic actuators such as the boom cylinder 12, the arm cylinder 14, the bucket cylinder 16, the swing motor, and the traveling motor, and the total output horsepower ( (Discharge flow rate × discharge pressure) is controlled so that the maximum output horsepower of the electric motor 20 does not exceed. Therefore, when the load is small, such as during assembly and disassembly, the discharge amount of the hydraulic pump 22 becomes large.

  FIG. 3 is a functional block diagram showing a configuration example of a portion for controlling the proportional solenoid valves 28 and 29 in the controller 35, and 38 to 40 are portions included in the controller 35. The coefficient generating means 38 changes a coefficient to be multiplied by the electric signal (voltage V) corresponding to the operation amount of the electric lever 36 depending on whether or not the switch 37 is turned on (closed). That is, the switch 37 is turned off in the standard mode that is the work speed mode inherent to the work implement, and the coefficient a is set to 1, for example. Conversely, in the low speed mode in which the switch 37 is turned on, the coefficient b is switched to a coefficient smaller than the coefficient. The operation signal changing means 39 generates aV or bV corresponding to a value obtained by multiplying the electric signal (voltage V) corresponding to the operation amount by the coefficient a or b generated by the coefficient generating means 38. The drive circuit 40 supplies a command current I substantially proportional to aV or bV to the solenoids 28a and 29a of the proportional solenoid valves 28 and 29.

  FIG. 4 is a graph showing the relationship between the signal (voltage V) corresponding to the operation amount of the electric lever 36 and the command current value I. In FIG. 4, the lever operation amount represented by the horizontal axis indicates the operation amount (+ V) to the proportional solenoid valve 28 on the right side, and the operation amount (−V) to the proportional solenoid valve 29 on the left side. The command current value I indicates the current (+ I) to the solenoid 28a of the proportional solenoid valve 28 on the upper side, and the current (-I) to the solenoid 29a of the proportional solenoid valve 29 on the lower side. A line 41 shows a VI relationship when the working machine is in a standard mode when the working machine is in an original working state, the switch 37 is turned off, and the coefficient generating means 38 generates the coefficient a. . The VI relationship based on the coefficient a is a relationship set by a conventional work machine. Line 42 is a VI relationship added according to the present invention, which is a low speed mode in assembly, replacement of parts, etc., V− when the switch 37 is turned on and the coefficient generating means 38 generates the coefficient b. I relationship.

  As can be seen from FIG. 4, in the low speed mode during assembly or parts replacement, the proportional constant of the command current value (I) with respect to the lever operation amount (V) is reduced by turning on the switch 37. The amount of movement of the spool of the proportional solenoid valves 28 and 29 relative to the amount of operation of the electric lever 36 in the proportional solenoid valves 28 and 29 is small. That is, fine adjustment can be easily performed in a state where the movement amount of the spool of the proportional solenoid valves 28, 29, that is, the flow path opening area of the proportional solenoid valves 28, 29 is narrow. That is, the pilot pressure applied from the pilot hydraulic pump 23 to the operation chambers 27a, 27b of the control valve 27 via the proportional solenoid valves 28, 29 is set to a low pressure, that is, the operating oil flow rate is small and the flow passage area of the control valve 27 is small. Thus, the extension degree of the boom cylinder 12 can be finely adjusted at a low speed.

  Thus, since the boom cylinder 12 can be finely expanded and contracted at a low speed, when assembling or replacing parts, for example, alignment of the pin hole at the tip of the boom cylinder 12 and the pin hole of the boom 13 Positioning of the pin holes between the boom 13 and the arm 15 is facilitated, and quick assembly and component replacement are possible. Similarly, the combination with the arm 15 and the bucket 16 enables easy and quick assembly and parts replacement. In this embodiment, the ratio (b / a) between the coefficients b and a is preferably set to about 0.2 to 0.5.

  FIG. 5 is a functional block diagram showing another embodiment of the present invention. In this embodiment, when the switch 37 is turned on, the operation signal changing means 43 sets the maximum value ± Vmax of the electric signal (voltage V) corresponding to the operation amount to be lower than the normal maximum value. .

  FIG. 6 is a graph showing the control by the operation signal changing means 43 as described above. In this embodiment, even if the operation amount of the electric lever 36 is increased, the voltage corresponding to the operation amount is limited to be ± Vmax, so that the command current value I is also a low value ± as indicated by the line 44. Limited to Imax. For this reason, since the hydraulic oil flow rate in the control valve 27 is maintained at a low level even when the electric lever 36 is not operated with great care during assembly or the like, the boom cylinder 12 can be finely adjusted at a low speed. Expansion and contraction is possible, and the same effect as in the above embodiment can be obtained. Here, the maximum current value ± Imax in the low speed mode is preferably 10 to 30% of the maximum value (100%) in the standard mode.

  FIG. 7 shows another embodiment of the present invention. In this embodiment, a connector 45 is used instead of the switch 37 of FIG. The connector 45 is separated during the original work of the work machine, and is connected when assembling or replacing parts. If such a connector 45 or the switch 37 is used, the working speed can be set by connecting / disconnecting the connector 45 or turning on / off the switch 37, so that the working speed can be switched relatively easily.

  In the illustrated example of FIG. 7, the operation signal changing means 39 changes the coefficients a and b (a <b) multiplied by the voltage V corresponding to the lever operation amount by connecting and disconnecting the connector 45 (during normal operation). Instead, as shown in FIG. 6, in the low-speed mode state where the connector 45 is connected, ± Vmax is set to a low value so that the low-speed mode is set. The maximum current value ± Imax may be limited to a low value.

  FIG. 8 is a functional block diagram further illustrating another embodiment of the present invention. In this embodiment, the variable resistor 46 is used as the operating speed mode setting means, the coefficient α (α ≦ 1) is increased or decreased according to the output voltage of the coefficient generating means 47, and the operation signal changing means 48 is operated by the lever operation. The voltage V corresponding to the quantity is multiplied by a coefficient α to obtain αV as an output.

  According to this embodiment, by adjusting the variable resistor 46, the drive circuit 40 can continuously change the proportional constant with respect to the lever operation amount of the command current value I to the solenoids 28a and 29b. For this reason, it becomes possible to adjust the speed of the boom cylinder 12 at a suitable speed according to the characteristics that differ depending on the actual machine and the individuality of the maintenance personnel.

  Although the present invention has been described with the embodiment, various modifications and additions other than the above-described embodiment can be made without departing from the gist of the present invention when the present invention is implemented. For example, by interposing a hydraulically operated pilot valve between the proportional solenoid valves 28 and 29 and the control valve 27, the proportional solenoid valves 28 and 29 are downsized, and the command current value I for the solenoids 28a and 29a is small. Can be configured to be dull. In addition, the present invention can be used for other working machines that use an AC electric motor driven by a constant frequency power source as a prime mover instead of the above-described electric motor driven by a high-voltage power source.

  1: lower traveling body, 2: side frame, 3: driving wheel, 4: driven wheel, 5: crawler track, 6: upper turning body, 7: turning device, 9: cab, 10: power unit, 11: working device, 12: boom cylinder, 13: boom, 14: arm cylinder, 15: arm, 16: bucket cylinder, 17: loader bucket, 18: power cable, 20: electric motor, 22: hydraulic pump, 23: pilot hydraulic pump, 24 : Oil tank, 25, 26: Relief valve, 27: Control valve, 28, 29: Proportional solenoid valve, 35: Controller, 36: Electric lever, 37: Switch, 45: Connector

Claims (3)

An AC electric motor driven by a constant frequency power supply;
A hydraulic pump driven by the electric motor;
A hydraulic actuator that is operated by hydraulic oil discharged from the hydraulic pump;
A control valve for controlling the amount of hydraulic fluid flowing to the hydraulic actuator;
A proportional solenoid valve for adjusting the operating pressure of the control valve;
An electric lever provided for operating the hydraulic actuator and outputting an electric signal as an output value;
In an operating speed control device for a working machine, comprising a controller for causing a command current value corresponding to an operation amount of the electric lever to flow through a solenoid of the proportional solenoid valve,
An operating speed mode setting means for setting an operating speed of the hydraulic actuator;
An operation speed of the work machine, comprising: an operation signal changing unit that changes a proportional constant or a maximum value of the command current value corresponding to an operation amount of the electric lever by an operation of the operation speed mode setting unit. Control device. The operating speed control device for a work machine according to claim 1,
An operating speed control device for a working machine, wherein the operating mode setting means is a switch or a connector that can be connected and disconnected. The operating speed control device for a work machine according to claim 1,
The operating speed control device for a working machine, wherein the operating speed mode setting means is a variable resistor capable of continuously adjusting a relationship between an operation amount of the operating lever and the command current value.

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