JPH0537041Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic circuit used in hydraulic power shovels and other construction machines.

[Conventional technology]

Conventionally, the bypass oil passage is connected to the downstream end of the bypass oil passage, which is controlled to open and close in a neutral position in conjunction with a directional control valve that is supplied with pressure oil from an engine-driven variable displacement pump. A pressure generating valve that generates a pilot operating pressure on the primary side is connected to a pump discharge amount control device that increases or decreases the discharge amount of the pump according to the load, and the pump discharge amount is minimized depending on the pilot operating pressure. Japanese Patent Laid-Open Publication No. 2002-2013 Sho has developed a construction machine that incorporates an auxiliary pilot valve to control the flow rate, and reduces the pump discharge amount when the actuator is inactive when the directional control valve is in the neutral position, thereby preventing wasted engine output and rising oil temperature. As shown in Publication No. 62-10341, the directional control valve was held in the neutral position in order to reduce the noise and avoid complaints from citizens when warming up the vehicle in urban areas in winter. If the target rotational speed of the engine is set to idle rotation and the resistance of the pressure generating valve is used to generate heat, the amount of pump discharge is small, so it takes a long time to warm up the oil in the entire tank.

[The problem that the idea attempts to solve]

In order to avoid this, as in the case of a hydraulic circuit driven by a constant displacement pump (for example, see Utility Model Application Publication No. 59-146603), the actuator (hydraulic cylinder) is connected to the stroke end by operating the directional control valve. If warm-up operation was performed by increasing the engine output and injecting the main relief valve, the pump load would be increased according to the set pressure of the main relief valve, which is significantly higher than that of the pressure generating valve. The pump discharge amount control device operates and reduces the pump discharge amount according to the pump load, so the warm-up time is shortened only by increasing the amount of fluid frictional heat generated according to the pressure difference before and after the main relief valve. However, on the other hand, the high-pitched noise from the relief valve and the engine noise are significant, and this continues until the oil in the entire tank is warmed up, resulting in complaints from citizens in urban areas.

Therefore, in practice, the driver operates each directional control valve to idle the actuator.
Although the main relief valve is prevented from operating, the driver must continue to control the directional control valve during warm-up, which is not only a real hassle, but also makes it difficult to operate the actuator in the cold outdoors. The problem was that the driver was easily fatigued because he had to do so in many cases.

[Means to solve the problem]

The present invention deals with this problem, and includes a position where the auxiliary pilot oil passage is conducted in the middle of the pilot oil passage 16 between the primary side of the pressure generating valve 8 and the pilot operating portion 15a of the auxiliary pilot valve 15; Switchable valves 17 and 19 are connected between the pilot operating section 15a and the position where it is connected to the tank.

If the switching valve is an electromagnetic switching valve, a temperature detector 18 is attached to the tank that is selectively connected to the power source and issues a signal when the oil temperature in the tank T falls below a predetermined temperature, and the pilot of the auxiliary pilot valve is installed. The electromagnetic switching valve 17, which has a normal position where the pilot oil passage 16 is conducted to the operating part 15a and a switching position where the pilot operating part is connected to the tank, is switched to the switching position by the signal generated by the temperature sensor. It may be configured as follows.

[Effect]

Since the present invention has the above-mentioned configuration, if the pilot oil passage is made conductive by the switching valve, not only can the pump discharge amount be increased when the actuator is driven, but also the actuator can be operated with the directional switching valve returned to the neutral position. When the pump is stopped, the pump discharge amount is reduced to prevent waste of pump drive power and rise in oil temperature, as in the conventional case.

Also, when warming up in winter, first maintain the directional control valve in the neutral position, and then turn the directional control valve 17 or 19 on.
The pilot operating part 15 of the auxiliary pilot valve is
Warm up the unit with a connected to the tank. Then, the pump discharge amount control device in which the hydraulic pressure of the pilot operating section is discharged into the tank operates to increase the pump discharge amount, so that the pressure generating valve 8 warms the hydraulic circuit between the directional control valve and the tank. Machine operation time can be shortened. Next, when the oil temperature in the tank reaches a predetermined temperature or higher, this is detected by a thermometer, etc., and the actuator is idled to warm up the hydraulic circuit between the directional control valve and the actuator. This prevents wear of the seals, etc., but idle movement of this actuator is
~3 times is sufficient.

If the switching valve is an electromagnetic switching valve 17, it can be controlled by a temperature sensor 18 that can issue a signal when the tank oil temperature drops below a predetermined temperature, so that the control of the temperature sensor controller can be performed in advance. By switching the switch to enable signal generation and starting warm-up operation, the electromagnetic switching valve can be switched to the switching position and the pump discharge amount can be increased.Moreover, if the tank oil temperature rises to a predetermined temperature, Since the temperature sensor no longer emits a signal, the electromagnetic directional valve automatically returns to the normal position and reduces the pump discharge amount, so the operating sound prevents the hydraulic circuit between the directional control valve and the tank from warming up. Sensing that it has ended,
Warming up of the hydraulic circuit between the directional control valve and the actuator can be started immediately.

〔Example〕

Figures 1 and 2 show one variable displacement type (axial piston type) of a two-pump power shovel.
An embodiment of the present invention is shown in which the present invention is applied to a hydraulic circuit driven by a pump 1, in which the pump 1 is driven by a diesel engine controlled by a mechanical or electrical all-speed governor, and the engine is warmed up. When driving, it is rotated at idle. The directional switching valve 2 for controlling the travel motor on one side and the directional switching valves 3, 4, and 5 for controlling the actuator on one side are connected in parallel to the discharge port of the pump 1, and are provided with a center bypass oil passage 6 that is conductive at the neutral position shown in the figure. . 20, 21, 2
Reference numerals 2 and 23 indicate a pair of piping provided between each of the directional control valves 2, 3, 4, and 5 and the corresponding actuator.

The tank passage 7 through which the return oil from the tank port of each directional control valve passes is connected at its upstream end to the center bypass oil passage 6 via the pressure generating valve 8, and the downstream part of the tank passage 7 is connected to the center bypass oil passage 6. Oil cooler 24 and filter 25 are connected in sequence. A check valve 26 is connected to the tank passage 7 in parallel with the filter 25, and the check valve 26 opens when the resistance increases due to clogging of the filter. Note that 27 is a relief valve connected to the pump discharge port, and its discharge oil passage 28 is of course connected to the tank passage 7.

The pump discharge amount (pump tilting angle) control device presses a parent-child piston 9, which is interlocked and connected to the pump swash plate so that the pump tilting angle can be adjusted, in a direction A to decrease the discharge amount, as shown in FIG. A child cylinder 10 that is always connected to the pump discharge port through an oil passage 29, a parent cylinder 11 that can press the parent and child piston in the direction of increasing the discharge amount, and two oil passages that each have one end connected to the parent cylinder. The other end of the return oil passage 12 is connected to the tank using the pilot oil pressure (pump discharge oil pressure) from the oil passage 30 when the pump load increases, and the other end of the pressure oil passage 13 is connected to the tank when the pump load decreases. It consists of a servo mechanism including a main pilot valve 14 connected to the pump discharge port by a return spring, and an auxiliary pilot valve 15 inserted in the middle of the pressure side oil passage 13.

The auxiliary pilot valve 15 is switched to the upper end position in FIG. 2 when the pilot operating pressure on the primary side of the pressure generating valve 8 is transmitted to its pilot operating portion 15a, and connects the main cylinder 11 directly to the tank T. When the pilot operating pressure of the pilot operating portion 15a is discharged to the tank, the auxiliary pilot valve 15 is switched to the lower end position shown in the figure by its own return spring elasticity, and the pressure between the parent cylinder and the main pilot valve is removed. The pressurizing side oil passage 13 is electrically connected. Reference numeral 31 in FIG. 2 indicates a lever 3 that feeds back the displacement of the parent and child piston 9 to the outer casing of the main pilot valve 14.
2 is a pilot valve 1 that assists the displacement of the parent and child pistons.
The lever that provides feedback to the outer casing of No. 5 is shown.

Pilot oil passage 1 between the primary side of the pressure generating valve 8 and the pilot operating portion 15a of the auxiliary pilot valve
The solenoid 17a of the electromagnetic switching valve 17 inserted in the middle of the tank T is connected to the temperature sensor 1 attached to the tank T.
8 controller 33 and its control switch 34. That is, if the switch 34 is opened to deactivate the controller 33 of the temperature sensor 18, the solenoid 17a will not operate, so the electromagnetic switching valve 17 will be maintained at the normal position shown in FIG. 1 where the pilot oil passage 16 is conducted. . When the switch 34 is closed and the controller 33 is connected to the power source 35, the controller starts operating, and when the oil temperature in the tank T is below a predetermined temperature, the temperature detector 18 issues a signal and energizes the solenoid 17a. Solenoid switching valve 1
7 to the right position (switching position) in FIG. 1, and the pilot operating part 15a is connected to the tank T via the oil passage 36, etc. However, when the tank oil temperature reaches a predetermined temperature, the switching valve 17 returns to the normal position. Return to

Therefore, the switch 34 is opened and the switching valve 17 is set to the first position.
In the normal operating state where the pilot oil passage 16 is maintained in the conducting position (normal position) shown in the figure, when either of the directional control valves 2, 3, etc. is switched from the neutral position shown in the figure to the actuator drive position, pressure is generated. Valve 8
Since no pilot operating pressure is generated on the primary side of the
The auxiliary pilot valve 15 returns to the lower end position shown in FIG.
3 conducts. Therefore, when the pump discharge oil pressure acting on the pilot operating portion 14a of the main pilot valve increases due to an increase in load, the main pilot valve connects the main cylinder 11 to the tank via the return oil passage 12 at the upper end in FIG. position, the parent and child piston 9 slides in the direction A in which the pump discharge amount decreases due to the hydraulic pressure of the child cylinder 10, and when the load decreases and the pump discharge oil pressure acting on the pilot operating portion 14a decreases. , since the main pilot valve is switched to the lower end position in the figure, which connects the parent cylinder to the pump discharge port via the pressurizing side oil passage 13, the parent and child piston 9 changes the pump discharge amount due to the difference in the pressure receiving area at both ends. When the main pilot valve 14 slides in the increasing direction and the pump discharge amount reaches a value corresponding to the load, the main pilot valve 14 returns to the neutral position shown in FIG.

When the actuator is stopped by returning the directional control valve to the neutral position from this actuator drive state, the bypass oil passage 6 becomes conductive and the pilot operating pressure of the auxiliary pilot valve 15 is generated on the primary side of the pressure generating valve 8. The auxiliary pilot valve is switched to the upper position of FIG. 2 to connect the parent cylinder 11 directly to the tank. Therefore, the parent and child piston 9 slides in the A direction by the oil pressure of the child cylinder 10, reducing the pump discharge amount.

Also, during warm-up operation with the switch 34 closed and the change-over valve 17 switched to a switching position for discharging the hydraulic pressure of the pilot operating section 15a of the auxiliary pilot valve 15 to the tank, the pressurized side oil passage 13 is opened by the auxiliary pilot valve 15. In this case, since the pump load is at a minimum, the pump discharge volume controlled by the main pilot valve 14 is at a maximum.

An embodiment in which the switching valve is an electromagnetic switching valve 17 and is configured to be automatically controlled by a temperature sensor 18 has been described above. A switching valve 19 can also be used. In FIG. 3, oil passages with the same symbols as those in FIG. 1 indicate corresponding oil passages, and in this case, switching between normal operation and warm-up operation is performed manually.

[Effect of idea]

According to the present invention, the following effects are achieved.

According to the structure of claim (1), the switching valve 17 or 1
9 can be selectively switched in advance to minimize the pump discharge amount at the neutral position of the directional control valve or to maximize the pump discharge amount at the neutral position of the directional control valve. By increasing the pump discharge amount without operating the directional valve, the hydraulic circuit between the directional valve and the tank can be warmed up more efficiently in a shorter time than before, and with less noise and no complaints from citizens. In addition, the number of warm-up operations of the hydraulic circuit between the actuator and the directional control valve that idles the actuator can be reduced, which reduces driver fatigue during warm-up operation.

According to the structure of claim (2), when the warm-up operation of the hydraulic circuit between the directional control valve in the neutral position and the tank is completed, this is detected from the operation sound and the hydraulic circuit is raised by the warm-up operation. Since you can immediately start a warm-up operation that idles the actuator without cooling the oil temperature, you can prevent heat loss during warm-up.
Moreover, the warm-up operation becomes very easy.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of one embodiment of the present invention, FIG. 2 is a schematic diagram of a pump discharge amount control device, and FIG. 3 is a diagram showing another embodiment of the switching valve of the present invention. 1... Pump, 2, 3, 4, 5... Directional switching valve, 6... Bypass oil passage, 7... Tank passage, 8
...Pressure generating valve, 9... Parent and child piston, 10...
Child cylinder, 11...Main cylinder, 14...Main pilot valve, 15...Auxiliary pilot valve, 15a
... Pilot operation section, 16 ... Pilot oil path, 17 ... Solenoid switching valve, 18 ... Temperature detector,
19...Switching valve, 33...Temperature detector controller, 34...Controller control switch.

Claims (1)

[Claims for Utility Model Registration] (1) A bypass oil passage 6 that is controlled to open and close so as to be conductive at a neutral position in conjunction with a directional control valve that is supplied with pressure oil from an engine-driven variable displacement pump.
A pressure generating valve 8 that generates a pilot operating pressure on the primary side when the bypass oil passage is conducted is connected to the downstream end of the pump, and a pump discharge amount control device that increases or decreases the discharge amount of the pump according to the load; In a hydraulic circuit for construction machinery incorporating an auxiliary pilot valve 15 that controls the pump discharge amount to a minimum based on the pilot operating pressure, the primary side of the pressure generating valve 8 and the pilot operating portion 15a of the auxiliary pilot valve 15 are connected to each other. Pilot oil passage 1 between
6, there is a switching valve 17, 1 which can be switched between a position where the pilot oil passage is conducted and a position where the pilot operating part 15a is connected to the tank.
9 is connected to a warm-up operation device for a hydraulic circuit for construction machinery. (2) A temperature detector 18 that is selectively connected to a power source and that issues a signal when the oil temperature in the tank T falls below a predetermined temperature is attached to the tank, and the temperature sensor 18 is installed in the tank to prevent pilot oil from flowing into the pilot operating section 15a of the auxiliary pilot valve. The electromagnetic switching valve 17, which has a normal position where the passage 16 is conducted and a switching position where the pilot operating section is connected to the tank, is configured to be switched to the switching position by the signal generated by the temperature detector. A warm-up operation device for a hydraulic circuit for construction machinery according to claim (1).