JP3462774B2 - Hydraulic circuit with cooling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a hydraulic circuit having a cooling device provided in a working machine such as a hydraulic shovel. 2. Description of the Related Art Generally, in a hydraulic circuit of a working machine such as a hydraulic shovel, a variable displacement hydraulic pump, a hydraulic actuator operated by supplying hydraulic oil from the hydraulic pump, and a return oil returning to a tank are provided. And a cooling device such as an oil cooler for cooling the oil. As such a hydraulic circuit, for example, a hydraulic circuit as shown in FIG. 4 is known. In this hydraulic circuit, a temperature detector 30 detects a hydraulic oil temperature in the oil tank 13 and the hydraulic oil temperature is set to a set temperature. In this case, a command is output from the control unit 16 to switch the electromagnetic switching valve 17, whereby the cooling motor 6 is driven to send cooling air to the oil cooler 14, and the oil cooler 14 It is configured to provide cooling. On the other hand, in the hydraulic circuit, the discharge flow rate of the hydraulic pump 2 is set to the minimum flow rate when the control valves 9 and 10 are in the neutral position N by guiding the pressure of the oil passage on the inlet side of the negative control relief valve 19 to the flow control device 3. While the control valves 9 and 10 are switched to the pressure oil supply position X or Y in response to the operation of the operating tools 11a and 12a, so that the discharge flow rate is controlled to increase. Energy saving and improved operability. [0003] In the above-mentioned conventional motor, when the temperature of the hydraulic oil rises abnormally for some reason during operation, or when the temperature of the hydraulic oil needs to be lowered quickly to repair the machine. In such a case, the control valves 9 and 10 are set to the neutral position N to lower the hydraulic oil temperature, the operation of the hydraulic cylinders 7 and 8 is stopped, and the cooling motor 6 is driven to supply cooling air to the oil cooler 14. Even if it is sent, as described above, the control valves 9, 1
When 0 is in the neutral position N, the discharge flow rate of the hydraulic pump 2 is minimized, so that the flow rate passing through the oil cooler 14 is reduced, and there is a problem that the working oil is not easily cooled, and the present invention will be solved here. There was a problem. SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has been made to solve these problems, and is provided with a variable displacement type for supplying hydraulic oil. Hydraulic pump, a hydraulic actuator operated by supply of hydraulic oil from the hydraulic pump, and return oil returning to the tank
A cooling device for cooling the return oil flowing through the road, while reducing the pump flow rate of the hydraulic actuator inoperative constituted by a flow control mechanism for increasing the pump flow in the hydraulic actuator operation state In a hydraulic circuit, a temperature detector for detecting a hydraulic oil temperature;
Setting in which the hydraulic oil temperature detected by the temperature detector is preset
Outputs an OFF signal if the temperature is lower than the set temperature
And a temperature controller for outputting an ON signal.
When the ON signal is output from the temperature controller, the cooling device
In the configuration for cooling the return oil, rapid cooling operation means that is turned on and off to rapidly cool the return oil, and cooling that operates the cooling device based on the ON operation of the rapid cooling operation means and actuation means, and rapid cooling at a flow rate increasing means for increasing the pump flow rate based on the oN operation of the rapid cooling operation means, the rapid cooling operation means OFF
In this case, the signal from the temperature controller should be transmitted to the cooling device.
Connected to the temperature controller and the rapid cooling operation means is ON.
In this case, the signal of the rapid cooling operation means is transmitted to the cooling device.
A signal switch connected to the quenching operation means;
The pressure circuit is provided with a hydraulic pressure control based on the ON operation of the rapid cooling operation means.
Locking means for holding the actuator inactive
Supply hydraulic oil from hydraulic pump to hydraulic actuator
Switch between the neutral position and the pressure oil supply position
Control valve and neutral position control valve
It has a center bypass oil passage that passes through to the relief valve.
The flow control mechanism controls the pressure in the oil passage on the inlet side of the relief valve.
If high, lower pump flow while lower pressure
In this case, the pump flow rate is increased,
The cooling flow rate increasing means is configured to supply the oil in the center bypass oil passage
Rapid cooling that flows to the return oil passage without passing through the relief valve
Rapid cooling of the bypass oil passage during recirculation and the bypass oil passage during rapid cooling
By releasing it based on the ON operation of the operating means,
Reduces the pressure in the oil passage on the inlet side of the leaf valve to increase the pump flow rate
To prevent the increased oil from passing through the relief valve.
Via the bypass oil passage at the time of rapid cooling
And a bypass device for opening a bypass oil passage at the time of rapid cooling for rapid cooling by flowing into an oil passage. In this way, by operating the rapid cooling operation means, the cooling device operates and the pump flow rate increases, so that the flow rate of the return oil cooled by the cooling device can be increased. The oil temperature can be reduced in a short period of time, the hydraulic actuator can be kept inactive during rapid cooling, and the pump flow rate can be increased during rapid cooling. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a hydraulic circuit of a working machine such as a hydraulic shovel. In the hydraulic circuit, reference numeral 1 denotes a prime mover, and 2 denotes a variable displacement main pump driven by the power of the prime mover 1 (corresponding to the hydraulic pump of the present invention). ), The main pump 2 is configured using a swash plate type axial piston pump whose discharge amount changes based on the displacement of the swash plate 2a. Further, 3 is a swash plate control device for controlling the displacement of the swash plate 2a, 4 is a pilot pump, and 5 is a cooling pump for supplying pressurized oil to a cooling motor 6 to be described later. The pump 4 and the cooling pump 5 are also driven by the power of the prime mover 1. Reference numerals 7 and 8 denote first and second cylinders provided in the hydraulic circuit, and reference numerals 9 and 10 denote first and second cylinders for controlling the supply of pressurized oil to the first and second cylinders 7 and 8, respectively. Control valves 11 and 12 are the first and second operating tools 1
First and second pilot valves 13 for supplying pilot pressure oil to the first and second control valves 9 and 10 based on the operations of 1a and 12a are oil tanks.
In the present embodiment, the first and second cylinders 7 and 8 have been described as hydraulic actuators that operate by supplying hydraulic oil from the main pump 2, but it is needless to say that the present invention is not limited to this. The first and second control valves 9 and 10 are connected to the first and second pilot valves 11 and 1, respectively.
In a state where the pilot pressure oil is not output from the second cylinder 2, the neutral position N where the pressure oil is not supplied to the first and second cylinders 7 and 8.
, But the first and second pilot valves 11,
With the supply of the pilot pressure oil from 12, the pressure oil from the main pump 2 is supplied to the expansion-side oil chamber or the reduction-side oil chamber of the first and second cylinders 7 and 8, while the reduction-side oil chamber or It is configured to switch to the extension side position X or the reduction side position Y for discharging oil from the extension side oil chamber to the oil tank 13. Further, in a state where the first and second control valves 9 and 10 are located at the neutral position N, valve paths 9a and 10a that communicate with a center bypass oil path A described later.
Is opened, and the valve paths 9a and 10a are set to be closed in a state where the valve paths 9a and 10a are located at the extension side position X or the reduction side position Y. B is a return oil passage extending from the first and second control valves 9 and 10 to the oil tank 13. The return oil passage B is provided for cooling oil returning to the oil tank 13. An oil cooler 14 is provided. A cooling fan 15 for sending cooling air to the oil cooler 14 is provided.
Rotates based on the drive of the cooling motor 6. The cooling motor 6 is driven based on the supply of pressurized oil from the cooling pump 5, and the oil in the oil path C from the cooling pump 5 to the cooling motor 6 is supplied to the cooling motor 5. The first bypass oil passage D that flows to the return oil passage B without passing through the branch oil passage 6 is branched. Further, the first bypass oil passage D is switched to an OFF position for opening the first bypass oil passage D and an ON position for closing the first bypass oil passage D based on a command from the control unit 16 described later. An electromagnetic switching valve 17 is provided. The first solenoid-operated switching valve 17 is
At the position F, the pressure oil from the cooling pump 5 returns to the return oil passage B via the first bypass oil passage D.
The cooling motor 6 is not driven by this, but the first electromagnetic switching valve 17 switches to the ON position to close the first bypass oil passage D, so that the pressure oil from the cooling pump 5 And the cooling motor 6 is driven. In FIG. 1, reference numeral 18 denotes a check valve for preventing negative pressure of the cooling motor 6. On the other hand, the center bypass oil passage A is connected from the main pump 2 to the negative control relief valve 19 (the present invention) via the valve passages 9a, 10a of the first and second control valves 9, 10 at the neutral position N. The oil that has passed through the negative control relief valve 19 is returned to the return oil passage B
To the upstream side of the oil cooler 14. Further, the pressure P of the oil passage on the inlet side (upstream side) of the negative control relief valve 19 is reduced by the negative control line E
To the swash plate control device 3 via the Then, as shown in the pump characteristic diagram of FIG. 3, the swash plate control device 3 sets the pressure P in the oil passage on the inlet side of the negative control relief valve 19 to a preset pressure P1 or less (P ≦ P1). Means that the discharge flow rate Q of the main pump 2 is equal to the maximum flow rate Qma
x, and when the pressure P is equal to or higher than a preset pressure P2 (P ≧ P2, where P1 <P2), the discharge flow rate Q is controlled to be a minimum flow rate Qmin.
Further, when the pressure P is between P1 and P2, the discharge flow rate Q is controlled so as to decrease as the pressure P increases. That is, the first and second operating tools 11a and 12a are not operated and the first and second control valves 9 and 1 are not operated.
In a state where 0 is located at the neutral position N and the valve paths 9a and 10a are open, the pressure oil from the main pump 2 is supplied to the negative control relief valve 19 via the center bypass oil path A. The pressure P of the oil passage on the inlet side of the negative control relief valve 19 is equal to the set pressure P
Therefore, the discharge flow rate Q of the main pump 2 is controlled to be the minimum flow rate Qmin. On the other hand, when the first and second control valves 9 and 10 are switched to the extension side position X or the contraction side position Y based on the operation of the first and second operation tools 11a and 12a, the valve paths corresponding to the operation amount are changed. 9a, 10
a gradually closes, and the pressure P in the oil passage on the inlet side of the negative control relief valve 19 decreases. When the valve paths 9a and 10a are fully closed, the pressure P decreases to near the tank pressure and becomes equal to or lower than the set pressure P1, and the discharge flow Q of the main pump 2 is controlled to the maximum flow Qmax. Further, F is a second bypass oil passage branching from the oil passage on the inlet side of the negative control relief valve 19 and joining the return oil passage B on the upstream side of the oil cooler 14 (the bypass oil for rapid cooling according to the present invention). In the second bypass oil passage F, a pilot check valve 20 (corresponding to the rapid cooling bypass oil passage opening means of the present invention) is disposed. This pilot check valve 20 closes the valve passage from the oil passage on the inlet side of the negative control relief valve 19 to the return oil passage B when the pilot pressure oil is not supplied to the pilot port 20a. The above-mentioned valve path is opened based on the supply of pilot pressure oil to the center bypass oil path A, whereby the oil in the center bypass oil path A passes through the second bypass oil path F without passing through the negative control relief valve 19. The oil flows into the return oil passage B. When the oil in the center bypass oil passage A is flowing to the return oil passage B via the second bypass oil passage F, the first and second control valves 9 and 10 are located at the neutral position N. However, the pressure P in the oil passage on the inlet side of the negative control relief valve 19 decreases. Thus,
The low pressure P is guided to the swash plate control device 3 through the negative control line E, so that the discharge flow rate Q of the main pump 2 is controlled to the maximum flow rate Qmax. On the other hand, G is a pilot oil passage from the pilot pump 4 to the first and second pilot valves 11 and 12, and the pilot oil passage G
Of closing pilot oil passage G based on command from
A second electromagnetic switching valve 21 that switches between an F position and an ON position for opening the pilot oil passage G is provided. When the second electromagnetic switching valve 21 is located at the OFF position,
The pilot pressure oil is not supplied from the pilot pump 4 to the first and second pilot valves 11 and 12, so that even if the first and second operating tools 11a and 12a are operated, the first and second pilot valves 11 and 12a are operated. Although the pilot pressure oil is not output from the pump 12, the pilot pump 4 is switched by switching the second electromagnetic switching valve 21 to the ON position.
The pilot pressure oil is supplied to the first and second pilot valves 11 and 12 from the first and second operating tools 11 and 12.
Pilot pressure oil is output from the first and second pilot valves 11, 12 based on the operations of a, 12a. Further, H is a branched pilot oil passage branched from a pilot oil passage G from the pilot pump 4 to the second electromagnetic switching valve 21 and leading to a pilot port 20a of the pilot check valve 20. A third electromagnetic switching valve 22 is provided in the branch pilot oil passage H. The third solenoid-operated directional control valve 22 controls the pilot check valve to turn off the oil from the pilot port 20a to the oil tank 13 and the pressure oil from the pilot pump 4 based on a command from the control unit 16. It is configured to switch to the ON position for supplying to the valve pilot port 20a. When the third electromagnetic switching valve 22 is switched to the ON position and the pilot pressure oil is supplied to the pilot check valve pilot port 20a, as described above, the pilot check valve 20
Is opened so that the oil in the center bypass oil passage A flows through the second bypass oil passage F to the return oil passage B. In FIG. 1, reference numeral 23 denotes a relief valve for a main circuit, and reference numeral 24 denotes a relief valve for a pilot circuit. The control unit 16 is constructed using a microcomputer or the like.
6 includes first and second signal switches 25 and 26 and a temperature controller 27 to be described later. The control unit 16 includes a safety switch 28, which will be described later, which is provided in the driver's seat of the working machine.
A signal from a quenching switch 29 and a temperature detector 30 provided in the oil tank 13 are input, and based on the input signals, the first and second signal switches 25 and 26 and a temperature controller 27 First, second, third electromagnetic switching valves 17, 21,
22 is configured to output an OFF-ON switching signal. The safety switch 28 is turned off when the operator leaves the work machine or when the engine is started, and is turned on when the operator is working. The signal of the safety switch 28 is a first signal. It is input to the switch 25. The first signal switch 25 is provided with a quenching switch 2.
The input signal from the safety switch 28 is switched to the ON side and the OFF side by an input signal from the switch 9. That is, when the safety switch 28 is OFF, the second electromagnetic switching valve 21 is switched to the OFF position, and when the safety switch 28 is ON, the second electromagnetic switching valve 21 is switched to the ON position. In addition, the first signal switch 25 is
In the state where the switch is switched to the F side, the signal of the safety switch 28 is not transmitted to the second electromagnetic switching valve 21, and the second electromagnetic switching valve 21 is held at the OFF position. The quenching switch 29 corresponds to the quenching operation means of the present invention.
Although it is operated to the F side, it is operated to the ON side when the operating oil temperature rises abnormally or when it is desired to rapidly decrease the operating oil temperature, and the signal of the quenching switch 29 is The signals are input to the first and second signal switches 25 and 26 and transmitted to the third electromagnetic switching valve 22. The first signal switch 25 switches to the above-described ON side when the rapid cooling switch 29 is OFF, and switches to the OFF side when the rapid cooling switch 29 is ON . In addition, the second signal switch (book
Corresponds to the "signal switching device" of the invention) 26, quenching switch 29 in the case of OFF is connected to a temperature controller side for transmitting a signal from the temperature controller 27 to the first electromagnetic switching valve 17, When the quenching switch 29 is ON, it is connected to the quenching switch that transmits the signal of the quenching switch 29 to the first electromagnetic switching valve 17. In a state where the second signal switch 26 is connected to the quenching switch,
The ON signal of the quenching switch 29 is transmitted to the first electromagnetic switching valve 17, and the first electromagnetic switching valve 17 is switched to the ON position. Further, the third electromagnetic switching valve 22 includes a quenching switch 29.
When the switch 29 is OFF, the switch is switched to the OFF position, and when the rapid cooling switch 29 is ON, the switch is switched to the ON position. Further, the temperature detector 30 detects the temperature of the working oil in the oil tank 13, and a signal from the temperature detector 30 is input to a temperature controller 27. The temperature controller 27 determines that the temperature T of the hydraulic oil detected by the temperature detector 30 is lower than a preset temperature T1 (T <T
In the case of 1), the OFF signal is transmitted to the second signal switch 26.
And the detected temperature T is equal to or higher than the set temperature T1 (T ≧ T1).
In this case, an ON signal is output to the second signal switch 26. When the second signal switch 26 is switched to the above-described temperature controller, the signal output from the temperature controller 27 is transmitted to the first electromagnetic switching valve 17. That is, when the OFF signal is output from the temperature controller 27, the first electromagnetic switching valve 17 is switched to the OFF position, and when the ON signal is output from the temperature controller 27, the first electromagnetic switching valve 17 is switched to the OFF position. It is switched to the ON position. In this case, the quenching switch 29 is normally operated to the OFF side. When the rapid cooling switch 29 is in the OFF state, the first signal switch 25 is switched to the ON side as described above, and the input signal from the safety switch 28 is transmitted to the second electromagnetic switching valve 21. . Further, the second signal switch 26 is connected to the temperature controller side, and a signal from the temperature controller 27 is transmitted to the first electromagnetic switching valve 17. Further, the third electromagnetic switching valve 22 is
It is located at the FF position. In this state, when the safety switch 28 is turned on to perform work, the second electromagnetic switching valve 2
1 is switched to the ON position, and the pilot pressure oil from the pilot pump 4 is supplied to the first and second pilot valves 11,
12 is supplied. Thereby, the first and second operating tools 11
The pilot pressure oil corresponding to the operation of the first and second control valves 9 and 10 is output from the first and second pilot valves 11 and 12 and supplied to the first and second control valves 9 and 10. The telescopic operation is performed. At this time,
Since the third electromagnetic switching valve 22 is located at the OFF position as described above, no pilot pressure oil is supplied to the pilot port 20a of the pilot check valve 20, and the pilot check valve 20 is connected to the inlet of the negative control relief valve 19. The valve path from the side oil path to the return oil path B is closed. As a result, the discharge flow rate of the main pump 2 is reduced as described above.
Is at the minimum flow rate when is located at the neutral position N,
In the state in which it is located at the extension side position X or the reduction side position Y, the flow rate is controlled so as to increase in accordance with the operation amount of the operation tools 11a and 12a. Further, at this time, since the second signal switching device 26 is connected to the temperature controller side as described above, the first electromagnetic switching valve 17 is turned off based on the OFF-ON signal output from the temperature controller 27. And the ON position. That is, when the operating oil temperature T detected by the temperature detector 30 is lower than the set temperature T1, the OFF signal is output from the temperature controller 27, and the first electromagnetic switching valve 17 is positioned at the OFF position. Accordingly, the cooling motor 6 is stopped, but when the working oil temperature T rises and becomes equal to or higher than the set temperature T1 when the work is continued for a long time or when the outside air temperature is high, the temperature controller 27 When the ON signal is output, the first electromagnetic switching valve 17 is switched to the ON position, whereby the cooling motor 6 is driven and cooling air is sent from the cooling fan 15 to the oil cooler 14. The working oil returning to the oil tank 13 is cooled. Meanwhile, and if the working oil temperature for some reason during operation rises abnormally, the like if it is necessary to lower the working oil temperature in a hurry to repair work machine, a rapid cooling switch 29 O Operate to N side. Thus, the first signal switching unit 25 is switched to O FF side, the second electromagnetic switching valve 2
1 is held in the OFF position. Also, the second signal switch 2
6 is connected to the quenching switch side, whereby the first electromagnetic switching valve 17 is switched to the ON position. Further, the third electromagnetic switching valve 22 is also switched to the ON position. When the first electromagnetic switching valve 17 is switched to the ON position, the cooling motor 6 is driven and the cooling fan 15
The cooling air is sent to the oil tank 13 to cool the working oil returning to the oil tank 13. Further, the supply of the pilot pressure oil to the first and second pilot valves 11 and 12 is cut off by holding the second electromagnetic switching valve 21 in the OFF position, thereby operating the operating tools 11a and 12a. Also, the pilot pressure oil is not supplied to the first and second control valves 9, 10, and the first and second control valves 9, 10 are held at the neutral position N. Further, when the third electromagnetic switching valve 22 is switched to the ON position, the pilot pressure oil is supplied to the pilot port 20a of the pilot check valve 20, and the second bypass oil passage F is opened.
The oil in the center bypass oil passage A via the first and second control valves flows to the return oil passage B via the second bypass oil passage F without passing through the negative control relief valve 19. Thus, the pressure P of the oil passage on the inlet side of the negative control relief valve 19 is reduced, and the discharge flow rate of the main pump 2 is controlled to be the maximum flow rate. When the hydraulic oil temperature needs to be lowered quickly, such as when the hydraulic oil temperature rises abnormally for some reason during operation or when the working machine is repaired, with the above-described structure, When operating the quenching switch 29 O N side, as described above, the cooling motor 6 is driven together with the cooling of the hydraulic oil by the oil cooler 14 is performed, the discharge flow rate of the main pump 2 becomes maximum. As a result, when it is desired to rapidly lower the hydraulic oil temperature, the flow rate of the oil passing through the oil cooler 14 increases, so that the hydraulic oil temperature can be lowered in a short time, and the working efficiency is improved. .

[Brief description of the drawings] FIG. 1 is a hydraulic circuit diagram of the present embodiment. FIG. 2 is a control block diagram. FIG. 3 is a diagram showing characteristics of a main pump. FIG. 4 is a hydraulic circuit diagram showing a conventional example. [Explanation of symbols] 2 Main pump 3 Swash plate control device 6 Motor for cooling 7 First cylinder 8 Second cylinder 9 First control valve 10 Second control valve 13 Oil tank 14 Oil cooler 17 First electromagnetic switching valve 19 Negative control relief valve 20 Pilot check valve 21 Second electromagnetic switching valve 22 Third electromagnetic switching valve 29 Rapid cooling switch A Center bypass oil passage F Second bypass oil passage

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshikazu Kurokawa 7-14, Wadamiyadori 7-chome, Hyogo-ku, Kobe City, Hyogo Pref. JP-A-7-167104 (JP, A) JP-A-62-188806 (JP, A) JP-A-3-41212 (JP, U) JP-A-5-45207 (JP, U) JP-A 6-56141 (JP, A) JP, U) JP-A-2-127803 (JP, U) (58) Fields studied (Int. Cl. ⁷ , DB name) F15B 21/04 F15B 11/00-11/22

Claims (1)

(57) [Claim 1] A variable displacement hydraulic pump for supplying hydraulic oil, a hydraulic actuator which is operated by supplying hydraulic oil from the hydraulic pump, and a return oil passage returning to the tank. flow
A cooling device for cooling the Ruri turn oil, while reducing the pump flow rate of the hydraulic actuator inoperative state,
In a hydraulic circuit including a flow control mechanism for increasing a pump flow rate in a hydraulic actuator operating state, a temperature detector for detecting a hydraulic oil temperature;
The hydraulic oil temperature detected by the heater is below the preset temperature.
Outputs an OFF signal when the temperature is full, and when the temperature is higher than the set temperature
Is provided with a temperature controller for outputting an ON signal.
When the ON signal is output from the node, the cooling device
In the configuration for cooling the cooling oil, rapid cooling operation means that is turned on and off to rapidly cool the return oil, and cooling that operates the cooling device based on the ON operation of the rapid cooling operation means and actuation means, and rapid cooling at a flow rate increasing means for increasing the pump flow rate based on the oN operation of the rapid cooling operation means, wherein when rapid cooling operation means is OFF
Temperature to transmit the signal from the temperature controller to the cooling device
If the rapid cooling operation means is connected to the controller and the rapid cooling operation means is ON
Rapid cooling to transmit the signal of the rapid cooling operation means to the cooling device
A signal switch connected to the operating means, and a hydraulic circuit
Is a hydraulic actuator based on the ON operation of the rapid cooling operation means.
Locking means for holding the eta inactive and oil
Do not supply pressure oil from pressure pump to hydraulic actuator
Control to switch between neutral position and pressurized oil supply position
Through the control valve in the neutral position
And a center bypass oil passage leading to the relief valve.
The control mechanism is used when the pressure in the oil passage on the inlet side of the relief valve is high.
To reduce the pump flow rate,
With a configuration that increases the pump flow rate,
The amount increasing means relieves the oil in the center bypass oil passage.
By-pass during rapid cooling to flow to the return oil passage without passing through the valve
Quick cooling operation means for the path oil passage and the rapid cooling bypass oil passage
The relief valve is opened based on the ON operation of the relief valve.
The pressure in the oil passage on the inlet side is reduced to increase the pump flow rate,
The increased oil is opened without passing through the relief valve.
Released to the return oil passage via the rapid cooling bypass oil passage
A hydraulic circuit comprising a cooling device comprising: a rapid cooling bypass oil passage opening means for flowing and rapid cooling .