JP2011020640A - Hydraulic fluid circuit for motorized shovel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic fluid circuit for a motorized shovel capable of using hydraulic fluid as a heat source of a heating apparatus and reliably cooling the hydraulic fluid regardless of whether heating operation is on or off. <P>SOLUTION: The hydraulic fluid circuit for the motorized shovel includes: a hydraulic pump 26 driven by an electric motor 25; a plurality of control valves 30 for controlling each of the flows of hydraulic fluid from the hydraulic pump 26 to a plurality of hydraulic actuators 29; and a return line 34 for the hydraulic fluid. The hydraulic fluid circuit for the motorized shovel further includes: a bypass line 35 branched to the return line 34; a switching valve 36 provided on the branch point of the bypass line 35; an oil cooler 37 provided on the bypass line 35; a blower fan 38 for sending air warmed by the oil cooler 37 into an operating room 7; an oil cooler 39 provided on a downstream of a connecting point of the bypass line 35; a heating operation switch 40; and a controller 42 for controlling the switching valve 36 in accordance with a command of the heating operation switch 40. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric excavator, and more particularly, to an electric excavator provided with a heating device for heating a cab.

  In recent years, an electric work machine equipped with an electric motor instead of an engine has been proposed because it has an advantage of not exhausting exhaust gas and greatly reducing noise and vibration. In this electric work machine, since the engine is not mounted, the hot water after cooling the engine cannot be used as a heat source of the heating device. Thus, for example, a method of using hydraulic oil whose temperature has been increased by the operation of a hydraulic actuator has been proposed (for example, see Patent Document 1).

  In the electric forklift described in Patent Document 1, a plurality of hydraulic actuators (specifically, lift cylinders and tilt cylinders) that drive the cargo handling device, and hydraulic oil to the plurality of hydraulic actuators according to the operation of the cargo handling operation lever. Control valves that respectively control the supply of oil, an oil cooler inserted in the middle of the oil conduit between the control valves and the oil tank, and the oil cooler warmed by heat exchange with hydraulic oil And a blower for sending air (warm air) to the driver side.

JP 2002-29690 A

  However, when the prior art described in Patent Document 1 is applied to an electric excavator, the following problems occur. Although not clearly described in Patent Document 1, the blower is driven when the heating operation is performed, and the blower is stopped when the heating operation is not performed. That is, when the heating operation is performed, the hydraulic oil is cooled by the oil cooler, but when the heating operation is not performed, the hydraulic oil is not cooled. Here, in the electric excavator, the hydraulic oil becomes very hot because the number of hydraulic actuators is larger than that in the electric forklift and the operation is often performed in the travel stop state. Therefore, even when the heating operation is not performed, if the hydraulic oil is not cooled, problems such as reforming of the hydraulic oil and damage to the seals of the oil pipes occur.

  An object of the present invention is to provide a hydraulic oil circuit of an electric excavator that can use hydraulic oil as a heat source of a heating device and can reliably cool the hydraulic oil regardless of whether or not heating operation is performed. is there.

  (1) In order to achieve the above object, the present invention provides an electric motor, a hydraulic pump driven by the electric motor, a plurality of hydraulic actuators, and a plurality of hydraulic pressures from the hydraulic pump according to operation of an operating means. In the hydraulic oil circuit of an electric excavator provided with a plurality of control valves that respectively control the flow of hydraulic oil to the actuator, and a return line that returns the hydraulic oil from the plurality of control valves to the oil tank, the branching from the return line A bypass line that merges with the return line, and a switching valve that is provided at a branch point of the bypass line in the return line and that switches to one of the return line side and the bypass line side to discharge hydraulic oil. A first oil cooler provided in the bypass line for cooling the hydraulic oil, and the first oil A blower fan that feeds air warmed by heat exchange with the hydraulic oil in the cooler to the cab; a second oil cooler that is provided downstream from the junction of the bypass line in the return line and cools the hydraulic oil; Heating operation instruction means capable of instructing the start / end of heating operation, and valve control means for controlling the switching valve in accordance with an instruction from the heating operation instruction means.

  In the present invention, for example, when there is a heating operation start instruction by the heating operation instruction means, the valve control means switches the switching valve to the bypass line side. Thereby, the return oil from the plurality of control valves to the oil tank passes through the first oil cooler and the second oil cooler. And the air warmed by the heat exchange with the hydraulic oil in the first oil cooler is sent into the cab by the blower fan. Therefore, hydraulic oil can be used as a heat source for the heating device. On the other hand, for example, when there is a heating operation end instruction by the heating operation instruction means, the valve control means switches the switching valve to the return line side. Thereby, the return oil from the plurality of control valves to the oil tank does not pass through the first oil cooler but passes through the second oil cooler. That is, the return oil always passes through the second oil cooler regardless of the heating operation. Therefore, it is possible to reliably cool the hydraulic oil regardless of the heating operation.

  (2) In the above (1), preferably, it further includes an oil temperature sensor for detecting the temperature of the hydraulic oil, and the valve control means is instructed to start a heating operation by the heating operation instruction means, and the oil temperature sensor When the temperature of the hydraulic oil detected in step S is larger than a preset threshold value, the switching valve is switched to the bypass line side, and the heating operation start means is instructed by the heating operation instruction means to be detected by the oil temperature sensor. When the temperature of the hydraulic oil is equal to or lower than the threshold value, the switching valve is switched to the return line side.

  Thereby, overcooling of hydraulic fluid can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, hydraulic fluid can be utilized as a heat source of a heating apparatus, and hydraulic fluid can be reliably cooled irrespective of the presence or absence of heating operation.

It is a side view showing the whole structure of the electric shovel which is an application object of the present invention. It is the schematic showing the hydraulic fluid circuit of the electric shovel in one Embodiment of this invention. It is the schematic showing the hydraulic fluid circuit of the electric shovel in other embodiment of this invention. It is a flowchart showing the control processing content of the controller in other embodiment of this invention.

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

  FIG. 1 is a side view showing the overall structure of an electric excavator to which the present invention is applied.

  In FIG. 1, an electric excavator includes a lower traveling body 2 having left and right crawler belts 1, an upper revolving body 3 that is turnably mounted on the lower traveling body 2, and the upper revolving body. 3, a swing frame 4 that forms the foundation lower structure, a swing post 5 that is mounted on the front portion of the swing frame 4 so as to be pivotable in the horizontal direction, and can swing up and down on the swing post 5. A) a multi-joint type front work machine 6 attached thereto, a canopy-type cab 7 provided on the left side of the revolving frame 4, and a battery (not shown) provided on the rear side of the revolving frame 4. The battery mounting part 8 to accommodate is provided.

  The lower traveling body 2 drives a substantially H-shaped track frame 9, left and right drive wheels 10 rotatably supported in the vicinity of the left and right rear ends of the track frame 9, and the left and right drive wheels 10, respectively. Left and right traveling hydraulic motors 11, left and right driven wheels (idlers) 12 that are rotatably supported in the vicinity of the left and right front ends of the track frame 9, and are respectively rotated by the driving force of the driving wheels 10 via the crawler belt 1. It has.

  In addition, a blade 13 for discharging soil is provided on the front side of the track frame 9 so as to be movable up and down, and the blade 13 is moved up and down by a hydraulic cylinder for blades (not shown). Further, a turning wheel (not shown) is provided between the center portion of the track frame 9 and the turning frame 4, and the turning frame 4 with respect to the lower traveling body 2 is disposed radially inside the turning wheel. Is provided with a turning hydraulic motor (not shown).

  The swing post 5 is rotatable in the horizontal direction with respect to the swing frame 4 via a vertical pin (not shown). The swing post 5 is rotated in the horizontal direction by a swing hydraulic cylinder (not shown), whereby the front work machine 6 swings to the left and right.

  The front work machine 6 includes a boom 14 that is pivotally connected to the swing post 5, an arm 15 that is pivotally coupled to the tip of the boom 14, and a pivot that can be pivoted to the tip of the arm 15. And a combined bucket 16. The boom 14, the arm 15, and the bucket 16 are operated by a boom hydraulic cylinder 17, an arm hydraulic cylinder 18, and a bucket hydraulic cylinder 19.

  The driver's cab 7 includes a driver seat (seat) 20 on which a driver is seated, a left console box 21 provided on the left side of the driver seat 20, and a right console box provided on the right side of the driver seat 20 (see FIG. Not shown). In front of the driver's seat 20, left and right traveling operation levers 22 are provided. An optional operation pedal (not shown) is provided on the left foot portion of the left traveling operation lever 22, and a swing operation pedal (not shown) is disposed on the further right foot portion of the right traveling operation lever 22. (Not shown) is provided. At the front of the left console box 21, there are provided a cross operation type turning / arm operation lever 23 and a lock lever 24 for preventing erroneous operation. At the front of the right console box, there are provided a cross operation type bucket / boom operation lever (not shown) and a blade operation lever (not shown).

  The upper swing body 2 includes an electric motor 25 (see FIG. 2 described later) driven by electric power from a battery, an inverter device (not shown) that controls the electric motor 25, and a hydraulic pump driven by the electric motor 25. 26 (see FIG. 2 to be described later), a pilot pump 27 (see FIG. 2 to be described later), an oil tank 28 (see FIG. 2 to be described later) for storing hydraulic oil, and the like are mounted.

  FIG. 2 is a schematic diagram illustrating a hydraulic oil circuit (hydraulic circuit) of an electric excavator according to an embodiment of the present invention. In FIG. 2, only one set of a hydraulic actuator, a control valve, and an operating device is shown for convenience.

  In FIG. 2, a hydraulic pump 26 and a pilot pump 27 driven by an electric motor 25, and a plurality of hydraulic actuators 29 (specifically, the left and right traveling hydraulic motors 11, the blade hydraulic cylinders, the swing hydraulic motor, the swing described above) Hydraulic cylinder for boom, hydraulic cylinder for boom 17, hydraulic cylinder for arm 18, and hydraulic cylinder for bucket 19 (represented by hydraulic cylinders as representative in the figure), and operation from hydraulic pump 26 to a plurality of hydraulic actuators 29 A plurality of control valves 30 for controlling the flow of oil (specifically, left and right travel control valves, blade control valves, swing control valves, swing control valves, boom control valves, arm control valves, For bucket Control valve) and a plurality of hydraulic pilot type operation devices 31 (specifically, an operation device with left and right traveling operation levers 22, an operation device with blade operation levers, and an operation with swing operation pedals) Device, an operation device provided with a turning / arm operation lever 23, and an operation device provided with a bucket / boom operation lever), and a lock valve 32 capable of shutting off the original pressure from the pilot pump 27. Yes.

  The lock valve 32 is provided in a hydraulic pipe line between the pilot pump 27 and the plurality of operation lever devices 31 and is switched according to the operation of the lock lever 34 so that the hydraulic pipe line can be communicated and cut off. It is. That is, when the lock lever 34 is pulled down to the lowered position (lowered state), the solenoid drive portion of the lock valve 32 is energized, and the lock valve 32 is switched to the communication position shown on the left side in the drawing. Thereby, the original pressure from the pilot pump 27 is guided to the operation lever device 31. On the other hand, when the lock lever 32 is pulled up to the raised position (the raised state), the solenoid drive portion of the lock valve 32 is not energized, and the lock valve 32 is switched to the shut-off position shown on the right side in the drawing by the biasing force of the spring. As a result, the original pressure from the pilot pump 27 is cut off.

  Although not shown in detail, the operation device 31 reduces the operation pilot pressure (secondary pilot pressure) obtained by reducing the original pressure (primary pilot pressure) from the pilot pump 27 according to the operation amount of the operation lever (or operation pedal). A pair of pressure reducing valves for output is provided. For example, when the operation lever (or operation pedal) is operated to one side, the operation pilot pressure generated by the pressure reducing valve on one side is output to the pilot operating portion on one side of the control valve 30, and the control valve 30 is moved to one side. Can be switched to. Accordingly, the hydraulic oil supplied from the hydraulic pump 26 via the discharge line 33 is supplied to one side of the hydraulic actuator 29, and the hydraulic oil from the other side of the hydraulic actuator 29 is supplied to the oil tank 28 via the return line 34. Returned. On the other hand, for example, when the operation lever (or operation pedal) is operated to the opposite side, the operation pilot pressure generated by the pressure reducing valve on the other side is output to the pilot operation part on the other side of the control valve 30, and the control valve 30 is moved to the opposite side. Is switched to. Accordingly, the hydraulic oil supplied from the hydraulic pump 26 via the discharge line 33 is supplied to the other side of the hydraulic actuator 29, and the hydraulic oil from one side of the hydraulic actuator 29 is supplied to the oil tank 28 via the return line 34. It is supposed to be returned.

  Here, as a major feature of the present embodiment, a bypass line 35 that branches from the upstream side of the return line 34 and connects to the downstream side of the return line 34 is provided, and a switching valve is provided at a branch point of the bypass line 35 in the return line 34. A (three-way valve) 36 is provided. The bypass line 35 is provided with an oil cooler 37 that cools the working oil, and the air that has been warmed by the oil cooler 37 by heat exchange with the working oil is supplied to the cab 7 (in detail, for example, A blower fan 38 to be fed into the driver's feet) is provided, and the oil cooler 37 and the blower fan 38 constitute a heating device. An oil cooler 39 is provided downstream of the connection point of the bypass line 35 in the return line 34. The cooling capacity of the oil cooler 37 is 20% or less with respect to the cooling capacity of the oil cooler 39.

  Further, a heating operation switch 40 (heating operation instruction means) and an air volume changeover switch 41 (heating air volume instruction means) are provided in the cab 7. The heating operation switch is capable of instructing ON (start) / OFF (end) of the heating operation, and outputs an instruction signal to the controller 42. The air volume changeover switch 41 can instruct the heating air volume in stages (specifically, for example, in one of three stages of strong wind, medium wind, and weak wind), and outputs the instruction signal to the controller 42. ing.

  When the ON signal is input from the heating operation switch 40, the controller 42 energizes the solenoid drive unit of the switching valve 36, and switches the switching valve 36 to the upper switching position in the figure. That is, the switching valve 36 is switched to the bypass line 36 side, and hydraulic oil flows out. At the same time, the blower fan 38 is driven. At this time, the rotational speed of the blower fan 38 is variably controlled in accordance with an instruction signal from the air volume changeover switch 41. On the other hand, for example, when an OFF signal is input from the heating operation switch 40, the solenoid drive portion of the switching valve 36 is not energized, and the switching valve 36 is switched to the lower switching position in FIG. That is, the switching valve 36 is switched to the return line 34 side, and the hydraulic oil flows out. At the same time, the blower fan 38 is stopped.

  Thus, in the present embodiment, for example, when there is a heating operation start instruction by the heating operation switch 40, the switching valve 36 is switched to the bypass line 36 side, so that the return oil from the plurality of control valves 30 to the oil tank 28 is , Via an oil cooler 37 and an oil cooler 39. Then, the air heated by the oil cooler 37 by heat exchange with the working oil is sent into the cab 7 by the blower fan 38. Therefore, hydraulic oil can be used as a heat source for the heating device. On the other hand, for example, when there is an instruction to end the heating operation by the heating operation switch 40, the switching valve 36 is switched to the return line 34 side, so that the return oil from the plurality of control valves 30 to the oil tank 28 passes through the oil cooler 37. Without going through the oil cooler 39. That is, the return oil always passes through the oil cooler 39 regardless of the heating operation. Therefore, it is possible to reliably cool the hydraulic oil regardless of the heating operation. As a result, problems such as hydraulic oil reforming and oil pipe seal damage can be avoided.

  Next, another embodiment of the present invention will be described. In the present embodiment, the switching valve is switched according to the temperature of the hydraulic oil.

FIG. 3 is a schematic diagram illustrating a hydraulic oil circuit of the electric excavator in the present embodiment.
FIG. In FIG. 3, parts equivalent to those in the above embodiment are given the same reference numerals, and description thereof will be omitted as appropriate.

  In the present embodiment, an oil temperature sensor 43 that detects the temperature of the hydraulic oil is provided on the downstream side of the oil cooler 39, and a detection signal from the oil temperature sensor 43 is output to the controller 42. The controller 42 </ b> A controls the switching valve 36 and the blower fan 38 in accordance with signals from the heating operation switch 40 and the oil temperature sensor 43. The control procedure of the controller 42A will be described below.

  FIG. 4 is a flowchart showing the contents of control processing of the controller 42A.

  In FIG. 4, first, at step 100, it is determined whether or not an ON signal is input from the heating operation switch 40. For example, when an ON signal is input from the heating operation switch 40, the determination in step 100 is satisfied, and the routine proceeds to step 110. In step 110, it is determined whether the temperature of the hydraulic oil detected by the oil temperature sensor 43 is greater than a preset threshold value (for example, 23 ° C.). For example, when the temperature of the hydraulic oil detected by the oil temperature sensor 43 is higher than the threshold value, the determination at step 110 is satisfied, and the routine proceeds to step 120. In step 120, the switching valve 36 is switched to the bypass line 35 side, the process proceeds to step 130, and the blower fan 38 is driven.

  On the other hand, for example, when an OFF signal is input from the heating operation switch 40, the determination in step 100 is not satisfied, and the routine proceeds to step 140. For example, when the temperature of the hydraulic oil detected by the oil temperature sensor 43 is equal to or lower than the threshold value, the determination in step 110 is not satisfied, and the routine proceeds to step 140. In step 140, the switching valve 36 is switched to the return line 34 side, the process proceeds to step 150, and the blower fan 38 is stopped.

  In this embodiment as well, as in the above-described embodiment, the working oil can be reliably cooled regardless of the presence or absence of the heating operation while using the working oil as a heat source of the heating device. Moreover, in this embodiment, overcooling can be prevented.

  In the above description, the hydraulic pilot type operation device 31 has been described as an example. However, the present invention is not limited to this, and the electric lever type (specifically, the operation amount of the operation lever or the operation pedal is detected by a detection means such as a potentiometer or a sensor. It is also possible to use an operation device that detects and outputs an electric operation signal. Further, as an application object of the present invention, an electric excavator provided with a canopy type cab 7 has been described as an example. However, the present invention is not limited thereto, and may be applied to an electric excavator provided with a cab type cab. . Further, as an application object of the present invention, a battery-mounted electric excavator has been described as an example. However, the present invention is not limited to this, and for example, the present invention is applied to an electric excavator capable of supplying power from an external power supply facility (commercial power supply). May be.

25 Electric motor 26 Hydraulic pump 28 Oil tank 29 Hydraulic actuator 30 Control valve 31 Operating device (operating means)
34 Return line 35 Bypass line 36 Switching valve 37 Oil cooler (first oil cooler)
38 Blower fan 39 Oil cooler (second oil cooler)
40 Heating operation switch (heating operation instruction means)
42 Controller (valve control means)
42A controller (valve control means)
43 Oil temperature sensor

Claims (2)

An electric motor, a hydraulic pump driven by the electric motor, a plurality of hydraulic actuators, and a plurality of control valves that respectively control the flow of hydraulic oil from the hydraulic pump to the plurality of hydraulic actuators according to operation of an operating means And a hydraulic oil circuit of an electric excavator provided with a return line for returning hydraulic oil from the plurality of control valves to the oil tank,
A bypass line branched from the upstream side of the return line and connected to the downstream side of the return line;
A switching valve that is provided at a branch point of the bypass line in the return line, and switches to one of the return line side and the bypass line side to discharge hydraulic oil;
A first oil cooler provided in the bypass line for cooling the hydraulic oil;
A blower fan for sending air warmed by heat exchange with hydraulic oil in the first oil cooler to the cab;
A second oil cooler that is provided downstream of the connection point of the bypass line in the return line and cools hydraulic oil;
Heating operation instruction means capable of instructing the start / end of heating operation;
A hydraulic oil circuit for an electric excavator, comprising: valve control means for controlling the switching valve in accordance with an instruction from the heating operation instruction means.   2. The hydraulic oil circuit for an electric excavator according to claim 1, further comprising an oil temperature sensor for detecting a temperature of the hydraulic oil, wherein the valve control means is instructed to start a heating operation by the heating operation instruction means, and When the temperature of the hydraulic oil detected by the temperature sensor is larger than a preset threshold value, the switching valve is switched to the bypass line side, and there is an instruction to start the heating operation by the heating operation instruction means, and the oil temperature sensor The hydraulic oil circuit for an electric excavator, wherein when the detected temperature of the hydraulic oil is equal to or lower than the threshold value, the switching valve is switched to the return line side.

Images