JP2005155698A - Hydraulic circuit of hydraulic work machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and securely ensure heat balance during warming-up operation when an engine starts and during work. <P>SOLUTION: The downstream side of a pilot control type direction change-over valve 14 or a solenoid control type direction change-over valve 21 is composed of a cooling oil passage 16 having an oil cooler 15 and a non-cooling oil passage 18 having no oil cooler. A shuttle valve 20 is provided in a communicating passage linking between a pair of pilot oil passages connecting a remote control valve 12 with a main direction change-over valve 7. The shuttle valve 20 is directly connected with a pilot control part of the pilot control type direction change-over valve 14 interposed in a return oil passage or is connected with a solenoid control part of the solenoid control type direction change-over valve 21 through a pressure switch 23 or the like. When operating the remote control valve 12, return oil is returned into a tank 17 through the cooling oil passage 16. When operating not the remote control valve 12, return oil is returned into the tank 17 through the non-cooling oil passage 18. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydraulic circuit of a hydraulic working machine equipped with an oil cooler.

Conventionally, in hydraulic work machines such as hydraulic excavators and cranes, the operation of hydraulic equipment such as valves and actuators is made smooth, and troubles of hydraulic equipment such as valves and actuators are prevented from occurring, especially during cold weather. A warm-up operation for increasing the temperature of the hydraulic oil is performed (for example, see Patent Document 1). On the other hand, during operation, the oil temperature of the hydraulic oil rises due to heat generated by the valves and actuators, and oil leakage occurs due to a decrease in viscosity, and the hydraulic oil tends to deteriorate. (For example, refer to Patent Document 2). In order to shorten the warm-up operation time by quickly raising the temperature of the hydraulic oil during the warm-up operation, while maintaining a good heat balance of the hydraulic oil, a cooling channel and a non-cooling are provided in the return channel. There has also appeared a structure in which a flow path is provided, an oil cooler is disposed in the cooling flow path, and an electromagnetic proportional valve is disposed in the non-cooling flow path (see, for example, Patent Document 3).
JP-A-8-284907 (pages 2 to 4, FIG. 1) JP 2001-65527 A (pages 2 to 4, FIG. 1) JP 2002-130216 A (pages 2 to 5, FIG. 1)

  The invention described in Patent Document 1 can reduce the load on the hydraulic pump when starting the engine by providing a heating device such as a heating heater in the suction pipe line connecting the hydraulic oil tank and the hydraulic pump to warm the hydraulic oil. In addition, it is possible to shorten the warm-up time of hydraulic oil after engine startup and save fuel consumption, and to warm up hydraulic oil in a short time when the engine starts, especially in cold weather It is. The invention described in Patent Document 1 is the most effective means in extremely cold regions in that a heating device is provided to actively warm the working oil, but a special device such as a heater and an oil temperature sensor is provided. In Japan, except for Hokkaido, it is not necessary to heat the hydraulic oil until a heating device is provided. A warm-up operation that circulates the hydraulic oil by starting the engine is sufficient.

  On the other hand, the invention described in Patent Document 2 is provided with a hydraulic oil cooler in order to cool the oil temperature of the hydraulic oil that has risen due to the heat generated by the valves and actuators during operation, contrary to Patent Document 1. A bypass circuit is provided to relieve the peak pressure applied to the oil cooler and extend the life, and a relief valve is inserted into this bypass circuit, but the bypass circuit is shut off below the set pressure of the relief valve. The hydraulic oil is returned to the tank via the hydraulic oil cooler, and the hydraulic oil having a high viscosity passes through the hydraulic oil cooler when the engine is started or cold, and adversely affects the hydraulic oil cooler. .

  The invention described in Patent Document 3 is provided with a pressure gauge for detecting the pressure upstream of the oil cooler provided in the cooling flow path. When the pressure of the pressure gauge is high, it is determined that the viscosity of the hydraulic oil is high. The oil that returns to the tank through the oil cooler based on the viscosity of the hydraulic oil that changes according to the temperature of the hydraulic oil. The amount of oil that returns to the tank without changing the amount or the oil cooler is changed. However, in the case of an oil cooler with a filter, the pressure upstream of the oil cooler increases due to clogging of the filter, and it seems difficult to derive the relationship between the pressure detected by the pressure gauge and the viscosity of the hydraulic oil. Regarding this point, there is a description regarding “clogging of the filter attached to the oil cooler” on page 5, column 7, line 17 to column 8, line 4 of the specification of Patent Document 3, which seems to be addressable. On the other hand, when the viscosity of the hydraulic oil is high, the suction resistance and power loss of the hydraulic pump increase and the pressure loss accompanying the flow increases. Generally, the oil cooler is often provided at the most downstream, so the viscosity of the hydraulic oil is high. However, it may not be said that the pressure of the hydraulic oil before the oil cooler is high, and there is a problem that it is difficult to properly control the electromagnetic proportional valve by measuring the pressure of the hydraulic oil before the oil cooler.

  Therefore, when the oil temperature of the hydraulic oil becomes high due to the operation of the valve or actuator, all of the return oil is guided to the tank via the oil cooler, while the oil temperature of the hydraulic oil when the engine is started, especially during cold weather. When the engine is low, all of the return oil is returned directly to the tank without passing through the oil cooler to eliminate the adverse effects on the oil cooler, ensuring easy and reliable warm-up when starting the engine and heat balance during work. Therefore, a technical problem to be solved arises, and the present invention aims to solve this problem.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 provides a main hydraulic pump, an actuator driven by pressure oil from the main hydraulic pump, and the actuator. In a hydraulic circuit including a main direction switching valve for controlling the direction of pressure oil and a remote control valve for deriving a pilot pressure of a pilot pump to a pilot control unit of the main direction switching valve, return oil downstream of the main direction switching valve A pilot-controlled directional switching valve is provided in the road, and a downstream of the pilot-controlled directional switching valve is constituted by a cooling oil passage having an oil cooler and a non-cooling oil passage not having an oil cooler. A pilot valve in which a shuttle valve is provided in a communication oil passage that connects between a pair of pilot oil passages that connect a pilot control unit of a direction switching valve, and the shuttle valve is provided in the return oil passage Connected to the pilot control unit of the control direction switching valve, the return oil is returned to the tank via the cooling oil passage when the remote control valve is operated, and the return oil is returned via the non-cooling oil passage when the remote control valve is not operated. It is a hydraulic circuit of a hydraulic working machine in which oil is returned to a tank.

  The invention described in claim 2 is a main hydraulic pump, an actuator driven by pressure oil from the main hydraulic pump, a main direction switching valve for controlling the direction of pressure oil supplied to the actuator, In a hydraulic circuit including a remote control valve for deriving a pilot pressure of a pilot pump in a pilot control unit of the main direction switching valve, a solenoid-controlled direction switching valve is interposed in a return oil path downstream of the main direction switching valve, and the solenoid A downstream of the control type directional control valve is constituted by a cooling oil passage having an oil cooler and a non-cooling oil passage not having an oil cooler, and a sensor for detecting the operation of the remote control valve is provided, and the sensor is connected to the return oil passage. Connected to the solenoid control unit of the solenoid-controlled directional switching valve provided, and when the remote control valve is operated, the return oil is returned to the tank via the cooling oil passage, Down valve non-operating-time is a hydraulic circuit of a hydraulic working machine which is returned to the tank return oil through the non-cooling oil passage.

  According to a third aspect of the present invention, there is provided a main hydraulic pump, an actuator driven by pressure oil from the main hydraulic pump, a main direction switching valve for controlling the direction of pressure oil supplied to the actuator, In a hydraulic circuit including a remote control valve for deriving a pilot pressure of a pilot pump in a pilot control unit of the main direction switching valve, a solenoid control type direction switching valve is interposed in a return oil path downstream of the main direction switching valve, and the solenoid A pair of pilot oil passages that comprise a cooling oil passage having an oil cooler and a non-cooling oil passage not having an oil cooler downstream of the control type directional control valve and connecting the remote control valve and the pilot control portion of the main directional control valve A shuttle valve is provided in the communication oil passage that connects the two, and a pressure switch is connected to the solenoid control portion of the solenoid-controlled directional valve that is provided in the return oil passage. The return oil is returned to the tank via the cooling oil passage when the remote control valve is operated, and the return oil is returned to the tank via the non-cooling oil passage when the remote control valve is not operated. It is the hydraulic circuit of the hydraulic working machine.

  According to the first to third aspects of the present invention, when starting the engine where the temperature of the hydraulic oil is low and the viscosity is relatively high, the operation lever of the remote control valve is held in the neutral position to discharge from the main hydraulic pump. Since the hydraulic oil to be circulated is circulated through the non-cooling oil passage, the oil cooler is not adversely affected and warm-up can be performed quickly. On the other hand, when the temperature of the hydraulic oil becomes high during the operation, the direction switching valve provided in the return oil passage is switched by operating the remote control valve, and the hydraulic oil is circulated through the cooling oil passage and is circulated by the oil cooler. Since it is cooled, overheating can be prevented and heat balance can be maintained. In addition, when the operation lever is returned to neutral even during work, the hydraulic oil returns to the tank via the non-cooling oil passage and is not cooled by the oil cooler, but the work lever is set to non-neutral (ON) during work. Since there are many cases where the hydraulic oil passes through the cooling oil passage, there is no problem in heat balance.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 is an overall side view of a hydraulic excavator that employs a hydraulic circuit according to the present invention, FIG. 2 is a hydraulic circuit diagram according to a first embodiment of the present invention, and FIG. 3 is an electric circuit according to a second embodiment of the present invention. FIG. 4 shows a hydraulic circuit diagram according to a third embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a lower traveling body, and an upper swing body 2 is pivotably mounted on the lower traveling body 1, and a front attachment 3 is pivotally attached to the front center of the upper swing body 2 so as to be able to move up and down. A cab 4 is placed on the front side of the upper swing body 2, and a counterweight 5 is attached to the rear end of the upper swing body 2.

  In the hydraulic circuit diagram according to the first embodiment of the present invention shown in FIG. 2, the discharge port of the main hydraulic pump 6 is connected to the P port of the main direction switching valve 7, and the A and B ports of the main direction switching valve 7 are respectively connected. Connected to the actuator 8, the T port of the main direction switching valve 7 is connected to the return oil passage 10 via the oil passage 9.

  The pilot pump 11 is connected to a remote control valve 12 having an operation lever 12a. The remote control valve 12 is connected to the pilot control sections 7a and 7b of the main direction switching valve 7 through a pair of pilot oil passages 13a and 13b, respectively. Yes.

  The return oil path 10 connected to the neutral flow path 7c of the main direction switching valve 7 is connected to the P port of the pilot-controlled direction switching valve 14, and the A port of the pilot-controlled direction switching valve 14 feeds the oil cooler 15. It is connected to the tank 17 via the inserted cooling oil passage 16, and the B port of the direction switching valve 14 is directly connected to the tank 17 via the non-cooling oil passage 18.

  A shuttle valve 20 is inserted in the communication oil passage 19 connecting the pair of pilot oil passages 13a and 13b, and the shuttle valve 20 is connected to the pilot control portion 14a of the pilot-controlled directional switching valve 14. Yes.

  When the engine is started while the operation lever 12a of the remote control valve 12 is held in the neutral position, the pilot pressure of the pilot pump 11 is controlled by the pilot control units 7a and 7b of the main direction switching valve 7 and the pilot of the pilot control type direction switching valve 14. Since it is not derived to any of the control units 14a, the main direction switching valve 7 is held at the neutral position, while the pilot-controlled direction switching valve 14 is held at the position 14b by the biasing force of the spring. As a result, the hydraulic oil discharged from the main hydraulic pump 6 passes through the neutral flow path 7 c of the main direction switching valve 7, the return oil path 10, the position 14 b of the pilot-controlled directional switching valve 14, and the non-cooling oil path 18. Returning to 17, the oil is discharged again from the main hydraulic pump 6 and circulated, whereby the oil temperature of the hydraulic oil rises and is warmed up.

  In this initial stage of warm-up, although the oil temperature of the hydraulic oil is low and the viscosity is relatively high, the hydraulic oil returns to the tank 17 through the non-cooling oil passage 18 and the cooling oil passage 16 with the oil cooler 15 is present. The oil cooler 15 is not adversely affected because it does not pass through.

  On the other hand, when the operation temperature of the operating oil 12a of the remote control valve 12 is operated when the oil temperature of the working oil rises due to warming up, the pilot pressure of the pilot pump 11 is controlled by the pilot control of the main direction switching valve 7. Is led to one of the parts 7a and 7b, and is led to the pilot control part 14a of the pilot-controlled directional control valve 14 via the shuttle valve 20, and is connected to the main directional switching valve 7 and the pilot-controlled directional control valve 14 The hydraulic oil discharged from the main hydraulic pump 6 is guided to the actuator 8 via the main direction switching valve 7, and the return oil from the actuator 8 flows from the T port of the main direction switching valve 7 to the oil passage 9 and the return oil. To return to the tank 17 through the passage 10, the position 14c of the pilot-controlled directional switching valve 14, and the cooling oil passage 16 in which the oil cooler 15 is inserted. Hydraulic oil is cooled.

  During operation, if the operating lever 12a of the remote control valve 12 is returned to the neutral position, pilot pressure is not derived to the pilot control unit 14a of the pilot-controlled directional switching valve 14, so that the hydraulic oil discharged from the main hydraulic pump 6 is Although it will not be cooled because it passes through the non-cooling oil passage 18 without passing through the cooling oil passage 16 inserted with the oil cooler 15, the operation lever is often set to non-neutral (ON) during operation. There are many cases where oil passes through the cooling oil passage, and there is no problem in heat balance.

  The electrohydraulic circuit diagram according to the second embodiment of the present invention shown in FIG. 3 is a solenoid controlled directional control valve instead of the pilot controlled directional control valve 14 in the hydraulic circuit diagram according to the first embodiment of the present invention shown in FIG. 21 is provided in the return oil passage 10, in the vicinity of the operation lever 12 a instead of the communication oil passage 19 connecting the pair of pilot oil passages 13 a and 13 b and the shuttle valve 20 inserted in the communication oil passage 19. A sensor 22 for detecting the operation of the remote control valve 12 is provided, and the sensor 22 is connected to the solenoid control unit 21a of the solenoid control type directional switching valve 21. The configuration is basically the same as that of the first embodiment. Has the same action and effect.

  That is, the return oil path 10 connected to the neutral flow path 7c of the main direction switching valve 7 is connected to the P port of the solenoid control type direction switching valve 21, and the A port of the solenoid control type direction switching valve 21 is an oil cooler. The B port of the solenoid-controlled directional switching valve 21 is directly connected to the tank 17 via the non-cooling oil passage 18.

  When the engine is started while the operation lever 12a of the remote control valve 12 is held at the neutral position, the pilot pressure of the pilot pump 11 is not led to the pilot control units 7a and 7b of the main direction switching valve 7, but from the sensor 22. Since the signal is not derived to the solenoid control unit 21a of the solenoid control type direction switching valve 21, the main direction switching valve 7 is held at the neutral position, and the solenoid control type direction switching valve 21 is held at the position 21b by the biasing force of the spring. Is done. As a result, the hydraulic oil discharged from the main hydraulic pump 6 passes through the neutral flow path 7 c of the main direction switching valve 7, the return oil path 10, the position 21 b of the solenoid control type direction switching valve 21, and the tank through the non-cooling oil path 18. Returning to 17, the oil is discharged again from the main hydraulic pump 6 and circulated, whereby the oil temperature of the hydraulic oil rises and is warmed up.

  On the other hand, when the operation temperature of the operating oil 12a of the remote control valve 12 is operated when the oil temperature of the working oil rises due to warming up, the pilot pressure of the pilot pump 11 is controlled by the pilot control of the main direction switching valve 7. The detection signal of the sensor 22 is led to the solenoid control unit 21a of the solenoid control type directional switching valve 21, and the main direction switching valve 7 and the solenoid control type directional switching valve 21 are derived to one of the parts 7a and 7b. The hydraulic oil discharged from the main hydraulic pump 6 is guided to the actuator 8 via the main direction switching valve 7, and the return oil from the actuator 8 flows from the T port of the main direction switching valve 7 to the oil passage 9 and the return oil. To return to the tank 17 through the passage 10, the position 21c of the solenoid-controlled directional switching valve 21, and the cooling oil passage 16 in which the oil cooler 15 is inserted. Hydraulic oil is cooled.

  As a result, when the operating lever is not operated, particularly when the engine is started, all of the return oil is circulated without passing through the oil cooler, so that warm-up can be performed quickly. Since all the oil passes through the oil cooler, the cooling efficiency can be improved, and warm-up / cooling can be selected in conjunction with the operation / non-operation of the operation lever. A heat balance can be obtained.

  The electrohydraulic circuit diagram according to the third embodiment of the present invention shown in FIG. 4 is a solenoid controlled directional control valve instead of the pilot controlled directional control valve 14 in the hydraulic circuit diagram according to the first embodiment of the present invention shown in FIG. 21 is provided in the return oil passage 10, and the solenoid control portion 21a of the solenoid type directional switching valve 21 and the shuttle valve 20 are connected via a pressure switch 23. Basically, the first embodiment. And it is the structure substantially the same as 2nd Embodiment, and there exists the same effect | action and effect.

  That is, the return oil path 10 connected to the neutral flow path 7c of the main direction switching valve 7 is connected to the P port of the solenoid control type direction switching valve 21, and the A port of the solenoid control type direction switching valve 21 is an oil cooler. The B port of the solenoid-controlled directional switching valve 21 is directly connected to the tank 17 via the non-cooling oil passage 18.

  When the engine is started while the operation lever 12a of the remote control valve 12 is held at the neutral position, the pilot pressure of the pilot pump 11 is not led to the pilot control units 7a and 7b and the pressure switch 23 of the main direction switching valve 7. The main direction switching valve 7 is held at the neutral position, while the solenoid control type direction switching valve 21 is held at the position 21b by the biasing force of the spring. As a result, the hydraulic oil discharged from the main hydraulic pump 6 passes through the neutral flow path 7 c of the main direction switching valve 7, the return oil path 10, the position 21 b of the solenoid control type direction switching valve 21, and the tank through the non-cooling oil path 18. Returning to 17, the oil is discharged again from the main hydraulic pump 6 and circulated, whereby the oil temperature of the hydraulic oil rises and is warmed up.

  On the other hand, when the operation temperature of the operating oil 12a of the remote control valve 12 is operated when the oil temperature of the working oil rises due to warming up, the pilot pressure of the pilot pump 11 is controlled by the pilot control of the main direction switching valve 7. And is output to the pressure switch 23 via the shuttle valve 20, and the output signal of the pressure switch 23 is guided to the solenoid control unit 21 a of the solenoid-controlled directional switching valve 21. Then, the main direction switching valve 7 and the solenoid control type direction switching valve 21 are switched, and the hydraulic oil discharged from the main hydraulic pump 6 is guided to the actuator 8 through the main direction switching valve 7, and the return oil from the actuator 8 is From the T port of the main direction switching valve 7 to the oil passage 9, the return oil passage 10, the position 21c of the solenoid control type direction switching valve 21, the oil cooler 15 To return to the tank 17 through the cooling oil path 16 being interposed, the hydraulic oil is cooled.

  As a result, when the operating lever is not operated, particularly when the engine is started, all of the return oil is circulated without passing through the oil cooler, so that warm-up can be performed quickly. Since all the oil passes through the oil cooler, the cooling efficiency can be improved, and warm-up / cooling can be selected in conjunction with the operation / non-operation of the operation lever. A heat balance can be obtained.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

Overall side view of a hydraulic excavator employing a hydraulic circuit according to the present invention Hydraulic circuit diagram according to the first embodiment of the present invention Electrohydraulic circuit diagram according to the second embodiment of the present invention Electrohydraulic circuit diagram according to the third embodiment of the present invention

Explanation of symbols

6 Main hydraulic pump 7 Main direction switching valve 8 Actuator 9 Oil path 10 Return oil path 11 Pilot pump 12 Remote control valve 12a Operation lever 14 Pilot control type direction switching valve 15 Oil cooler 16 Cooling oil path 17 Tank 18 Non-cooling oil path 19 Communication Oil path 20 Shuttle valve 21 Solenoid-controlled directional valve 22 Sensor 23 Pressure switch

Claims (3)

  A main hydraulic pump, an actuator driven by pressure oil from the main hydraulic pump, a main direction switching valve for controlling the direction of the pressure oil supplied to the actuator, and a pilot controller for the main direction switching valve In a hydraulic circuit including a remote control valve for deriving a pilot pressure of the pump, a pilot-controlled directional switching valve is interposed in a return oil passage downstream of the main directional switching valve, and an oil cooler is provided downstream of the pilot-controlled directional switching valve. And a non-cooling oil passage not having an oil cooler, and a shuttle valve in a communication oil passage connecting a pair of pilot oil passages connecting the remote control valve and the pilot control unit of the main direction switching valve. The shuttle valve is connected to a pilot control unit of a pilot-controlled directional switching valve interposed in the return oil passage, and the cooling oil is operated when the remote control valve is operated. While returning to the tank return oil through the remote control valve inoperative when the hydraulic circuit of a hydraulic working machine, characterized in that it has returned to the tank return oil through the non-cooling oil passage.   A main hydraulic pump, an actuator driven by pressure oil from the main hydraulic pump, a main direction switching valve for controlling the direction of the pressure oil supplied to the actuator, and a pilot controller for the main direction switching valve In a hydraulic circuit including a remote control valve for deriving a pilot pressure of the pump, a solenoid-controlled directional switching valve is provided in a return oil path downstream of the main directional switching valve, and an oil cooler is disposed downstream of the solenoid-controlled directional switching valve. And a non-cooling oil passage having no oil cooler, a sensor for detecting the operation of the remote control valve is provided, and a solenoid-controlled directional switching valve provided with the sensor in the return oil passage. Connected to the solenoid control unit, when the remote control valve is operated, the return oil is returned to the tank through the cooling oil passage, while when the remote control valve is not operated, the non-cooling oil is returned. Hydraulic working machine of a hydraulic circuit, characterized in that it has returned to the tank return oil through the.   A main hydraulic pump, an actuator driven by pressure oil from the main hydraulic pump, a main direction switching valve for controlling the direction of the pressure oil supplied to the actuator, and a pilot controller for the main direction switching valve In a hydraulic circuit including a remote control valve for deriving a pilot pressure of the pump, a solenoid-controlled directional switching valve is provided in a return oil path downstream of the main directional switching valve, and an oil cooler is disposed downstream of the solenoid-controlled directional switching valve. And a non-cooling oil passage not having an oil cooler, and a shuttle valve in a communication oil passage connecting a pair of pilot oil passages connecting the remote control valve and the pilot control unit of the main direction switching valve. And connecting the shuttle valve via a pressure switch to a solenoid control unit of a solenoid-controlled directional switching valve provided in the return oil passage. The hydraulic working machine is characterized in that the return oil is returned to the tank through the cooling oil passage during operation, and the return oil is returned to the tank through the non-cooling oil passage when the remote control valve is not operated. Hydraulic circuit.

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