JP2011064274A - Drain circuit of hydraulic pump of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drain circuit of a hydraulic pump of a construction machine which enables a drain oil of the hydraulic pump to warm the hydraulic pump when a temperature in working fluid is low, for example, when warming the construction machine is performed. <P>SOLUTION: The drain circuit 18 of the hydraulic pump 12 of the construction machine is provided with a directional control valve 22 which switchably connects a drain oil passage 20 of the hydraulic pump 12 to a tank 4 of the working fluid or an intake oil passage 6 of the hydraulic pump 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a drain circuit of a hydraulic pump of a construction machine.

  Construction machines, for example, hydraulic excavators, which are representative examples, are driven by many hydraulic actuators. When the construction machine is loaded, a warm-up operation is performed in which a hydraulic pump that discharges hydraulic oil to the hydraulic actuator is operated with a light load to warm the hydraulic oil. In a construction machine operating in a cold district or the like, an electric heater is incorporated in a hydraulic oil suction pipe connecting a hydraulic oil tank and a hydraulic pump in order to warm up effectively at the start of work (for example, Patent Document 1). reference).

  On the other hand, during the load operation of construction machinery, hydraulic oil that operates at high pressure is frequently released from the relief valve, so this energy becomes heat and returns to the tank, and the hydraulic oil in the tank. Becomes hot. When a large amount of hydraulic oil returning from the hydraulic actuator to the tank becomes excessively hot, an oil cooler is installed in the return oil passage to the tank, and the hydraulic oil is cooled (for example, see Patent Document 2).

  In a hydraulic pump that discharges high-pressure hydraulic oil, the piston, gears, bearings, and the like of the pump are lubricated by a part of the discharged oil. This oil is led to the tank by a drain oil passage. The drainage oil of the hydraulic pump also discharges the high-pressure discharge oil to the low-pressure part, so that its energy changes to heat and becomes high temperature, which is a small amount compared to the return oil, but the temperature of the hydraulic oil in the tank To raise.

JP-A-8-284907 (FIG. 1) JP-A-8-128076 (FIG. 1)

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is that the hydraulic pump is warmed by the drain oil of the hydraulic pump when the temperature of the hydraulic oil is low, such as during the warm-up operation of the construction machine. It is an object of the present invention to provide a drain circuit for a hydraulic pump of a construction machine.

  According to the present invention, as a drain circuit of a hydraulic pump of a construction machine that solves the above technical problem, a switching valve that connects the drain oil passage of the hydraulic pump to a hydraulic oil tank or to a suction oil passage of the hydraulic pump in a switchable manner is provided. A drain circuit for a hydraulic pump of a construction machine is provided.

  Preferably, the switching valve is constituted by an electromagnetic switching valve, and includes a detection switching means for detecting the temperature of the hydraulic oil sucked into the hydraulic pump and switching the electromagnetic switching valve at the set temperature, and the electromagnetic switching valve detects the drain oil passage. When the measured temperature exceeds the set temperature, it is connected to the tank, and when it is lower than the set temperature, it is connected to the suction oil passage. Further, the drain oil passage connected to the tank is connected upstream of the oil cooler of the return oil passage to the tank of the working oil of the construction machine having the oil cooler.

  The drain circuit of the hydraulic pump of the construction machine configured according to the present invention includes a switching valve that connects the drain oil passage of the hydraulic pump to the hydraulic oil tank or to the suction oil passage of the hydraulic pump. Therefore, when the temperature of the hydraulic oil is low as in the warm-up operation, the drain oil can be introduced into the suction oil passage of the hydraulic pump by the switching valve to warm the hydraulic pump.

The hydraulic circuit diagram of the construction machine provided with the drain circuit of the hydraulic pump comprised according to this invention.

  Hereinafter, a drain circuit of a hydraulic pump of a construction machine configured according to the present invention will be described in more detail with reference to the accompanying drawings illustrating a preferred embodiment.

  A description will be given with reference to FIG. The hydraulic circuit of the construction machine includes a hydraulic pump 12 that is driven by the engine 2 and sucks the hydraulic oil in the tank 4 through the suction oil passage 6 and discharges it to the actuator circuit 10 through the discharge oil passage 8. The hydraulic oil that has passed through the actuator circuit 10 is returned to the tank 4 through a return oil passage 16 in which an oil cooler 14 is installed.

  The hydraulic pump 12 is constituted by, for example, a well-known piston pump that discharges high-pressure hydraulic oil. Leakage oil from an internal piston, a bearing portion, or the like that is lubricated by a part of the discharged oil is sucked by a drain circuit 18. The oil passage 6 or the return oil passage 16 is switchably connected.

  The actuator circuit 10 is a well-known one including a hydraulic cylinder, a hydraulic motor, a hydraulic control valve, and the like, such as a traveling device, a working device, and a steering device, which are operated by the discharge oil of the hydraulic pump 12.

  The drain circuit 18 includes a drain oil path 20 (shown by a dotted line) that connects the drain oil of the hydraulic pump 12 to the suction oil path 6 and the return oil path 16, and a drain oil that is provided in the drain oil path 20. An electromagnetic switching valve 22 which is a switching valve for switching to the return oil passage 16 and a temperature switch 24 as detection switching means for detecting the temperature of the hydraulic oil sucked into the hydraulic pump 12 and switching the electromagnetic switching valve 22 at a set temperature are provided. .

  The electromagnetic switching valve 22 is composed of a two-position switching valve, and when the temperature switch 24 is not energized, the drain oil path 20 is connected to the suction oil path 6. When energized, the electromagnetic switching valve 22 connects the drain oil passage 20 to the return oil passage 16.

  The temperature switch 24 is installed in the hydraulic oil tank 4, detects the temperature of the hydraulic oil in the tank 4 that the hydraulic pump 12 sucks, and energizes the electromagnetic switching valve 22 when the detected temperature exceeds the set temperature. The set temperature is set to 60 ° C., for example, but may be set according to the type of construction machine, the form of work, the work environment, and the like.

  A drain oil passage 20 connected to the return oil passage 16 is connected to the upstream side of the oil cooler 14 so that the drain oil passes through the oil cooler 14. The oil cooler 14 is a known one having a cooler body 14a and a bypass valve 14b.

  The effect of the drain circuit of the hydraulic pump of the construction machine as described above will be described.

  The drain circuit 18 of the hydraulic pump of the construction machine includes a switching valve 22 that connects the drain oil passage 20 of the hydraulic pump 12 to the hydraulic oil tank 4 or the suction oil passage 6 of the hydraulic pump 12 in a switchable manner. Therefore, when the temperature of the hydraulic oil is low as in the warm-up operation, the drain oil can be introduced into the suction oil passage 6 of the hydraulic pump 12 by the switching valve 22 to warm the hydraulic pump 12. When the warm-up operation ends, the switching valve 22 is switched to connect the drain oil to the return oil passage 16 and return to the tank 4 so that the high-temperature drain oil is cooled by heat radiation.

  Since the switching valve 22 of the drain circuit 18 is constituted by an electromagnetic switching valve, the switching valve 22 is provided with detection switching means 24 for detecting the temperature of the hydraulic oil sucked into the hydraulic pump 12 and switching the electromagnetic switching valve 22 at the set temperature. 22 can connect the drain oil passage 20 to the tank 4 when the detected temperature exceeds the set temperature, and to the suction oil passage 6 when the detected temperature is lower than the set temperature, and can be automatically switched.

  Since the drain oil passage 20 connected to the tank 4 is connected upstream of the oil cooler of the return oil passage 16 to the tank 4 for the working oil of the construction machine having the oil cooler 14, the high-temperature drain oil is supplied to the oil cooler 14. Can be cooled and returned to the tank.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various changes or modifications can be made within the scope of the present invention, for example, as described below. Is.

  In the embodiment of the present invention, the temperature switch 24 is provided as the detection switching means. However, a combination of a temperature sensor and a controller that controls the output signal and outputs it to the electromagnetic switching valve 22 may be used.

  In the embodiment of the present invention, the switching valve 22 is constituted by an electromagnetic switching valve, but may be a manual switching valve.

  In the embodiment of the present invention, the drain oil passage 20 connected to the return oil passage 16 is connected to the upstream side of the oil cooler 14, but when it is not necessary to pass the oil cooler 14, it is connected to the downstream side. May be.

  In the embodiment of the present invention, the temperature switch 24 that detects the temperature of the hydraulic oil sucked into the hydraulic pump 12 and switches the electromagnetic switching valve 22 at the set temperature is installed in the tank 4, but is installed in the suction oil passage 6. May be.

4: Tank 6: Suction oil passage 12: Hydraulic pump 14: Oil cooler 16: Return oil passage 18: Drain circuit 20: Drain oil passage 22: Electromagnetic switching valve (switching valve)
24: Temperature switch (detection switching means)

Claims (3)

A switching valve that connects the drain oil passage of the hydraulic pump to the hydraulic oil tank or the suction oil passage of the hydraulic pump in a switchable manner;
A drain circuit for a hydraulic pump of a construction machine. The switching valve is constituted by an electromagnetic switching valve,
Detection switching means for detecting the temperature of the hydraulic oil sucked into the hydraulic pump and switching the electromagnetic switching valve at the set temperature;
The electromagnetic switching valve connects the drain oil passage to the tank when the detected temperature exceeds the set temperature, and to the suction oil passage when the detected temperature is lower than the set temperature.
The drain circuit of a hydraulic pump for a construction machine according to claim 1. The drain oil passage connected to the tank
Connected upstream of the oil cooler in the return oil path to the hydraulic oil tank of the construction machine with the oil cooler,
The drain circuit of a hydraulic pump for a construction machine according to claim 1 or 2.

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