JPH0333802Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic circuit applied to a control valve of a hydraulic power shovel.

[Conventional technology]

There is no prior art similar to the present invention, and it belongs to a new category.

[Problem that the invention attempts to solve]

In order to increase the traveling speed without changing the discharge flow rate of the hydraulic pump, the theoretical stroke volume of the traveling motor is
Just make qth smaller. Generally, when the travel motor is started, the load pressure is high, and this pressure is determined by the circuit system pressure Pmax. Therefore, if the theoretical stroke volume qth of the travel motor is reduced in order to increase the travel speed, and the circuit system pressure remains the same as before, then if the capacity reduction amount of the travel motor is △qth, the output torque of the travel motor will be (constant )×(qth−△qth)×
Pmax, conventional output torque (constant) x qth x
It will be lower than Pmax. In order to solve this problem, it is possible to use a variable displacement motor that sets the capacity to qth as before when the load pressure is high at startup, and decreases the capacity when the load pressure decreases during steady running. Mechanical motors are generally expensive. Therefore, the present invention makes it possible to make the capacity of the motor slightly smaller than the conventional one while keeping the capacity of the motor fixed, to increase the vehicle speed, increase the circuit system pressure, and prevent the output torque from decreasing at the time of starting. The present invention aims to provide a low-cost circuit system capable of canceling the increase in circuit system pressure when a travel motor and other actuators are operated simultaneously in order to prevent a reduction in the fatigue life of other actuators.

[Means for solving problems]

(1) In order to increase the vehicle speed during steady driving, reduce the theoretical stroke volume of the travel motor. (Initial volume
qth, the reduction amount is △qth, and the pump discharge amount is Q, then the motor rotation speed is △N=Q/
It becomes faster by (qth - △qth) - Q/qth. ) (2) A pilot pressure generation mechanism is installed in the travel operation valve and other actuator operation valves to increase the set pressure of the circuit main relief valve when only travel operation is performed, and to increase the set pressure when travel and other operation valves are operated simultaneously. to normal pressure. (Normally set pressure
Pmax, and the boosting amount is △P. Motor output torque T = (constant) Pmax x qth = (constant) x (Pmax
If △P is set so that +△P) x (qth - △q), even when the motor capacity is reduced as shown in (1) above,
Obtain the same motor output torque as the original. ) [Function] The vehicle speed increases during steady running when the load on the traveling motor is low, and the hydraulic pressure applied to other actuators during running can be reduced.

〔Example〕

In FIG. 1, either or both of the operation valves 3 and 6, which control the left and right travel motors 10 and 11 that rotate and travel the left and right crawlers of the hydraulic power shovel and determine the rotation direction, are switched. A portion of the pressure oil from the pumps 1 and 2 passes through the check valves 19 and 20 and the throttle 21 and then reaches the pilot portion 27 of each spool.
Due to the neutral functions 16, 17, 18, 28, 29, and 30, the oil that had been drained to the return line T is closed by the above operation, so that the oil flow through the throttle 21 is eliminated. Therefore, a high pressure equal to the high-pressure side discharge pressure of the pumps 1 and 2, that is, a pressure in the passage 53, is generated in the passage 23. Also, part of the pressure oil from the pumps 1 and 2 passes through the check valves 19 and 20 and the throttle 22, and drops as drain from the passage 62 to the return line T by the neutral functions of the pilot sections 17, 18, 28, 29, and 30. Therefore, the pressure in the passage 62 is low. The travel motors 10 and 11 are under high pressure when started due to their inertial loads, and this pressure is determined by the set pressure of the relief valve 25. The pressure setting of 25 is determined by the preset load of the spring 25a, but the high pressure of the passage 23 acts on the chamber 26b of both rod cylinders 26 that adjusts the preset length.
Since the chamber 26a is connected to the low pressure of the passage 62, the rod 26c decreases the preset length of the spring 25a, moves to the side where the load is increased, and stops. For this reason, the set pressure of the relief valve 25 is the normal setting value.
Increase the voltage by △P from Pmax. Therefore, the pressure at the time of starting the travel motors 10, 11 becomes high. As mentioned above, the motor output torque can be kept the same as before by adding this boost function to the extent that the capacity of the travel motor is reduced in order to increase the vehicle speed. Furthermore, actuators 12, 13, 14, 15 other than the travel motor
When attempting to operate the corresponding operation valves 4, 7, etc.
When any of 5, 8, and 9 is switched, the pilot section 1
The corresponding ones of 7, 28, 18, 29, 30 are
Since the return flow from the passage 62 to the return line T is cut off, the flow of pilot oil flowing through the restriction 22 disappears, and the passage 62 absorbs the pressure of the passage 53, that is, the pressure of the passage 23.
is equal to the pressure of Both rod cylinders 26-2
Since the pressures in chambers 6a and 26b are equal, the spring 25
a causes the rod 26c to move upward in the figure, and the preset length of the spring 25a becomes the normal setting value. However, it is assumed that chambers 26a and 26b of both rod cylinders 26 have the same pressure receiving area. Therefore, when one or both of the left and right travel motors 10, 11 and the other actuators 12 to 15 are operated simultaneously, the set pressure of the relief valve 25 can be reduced to a level that does not impede the fatigue life of the other actuators. . Furthermore, when operating only other actuators while the traveling operation valve remains neutral, the throttle 21,
Since the pilot oil downstream of 22 joins in the passage 65, the pilot oil flows in the pilot parts 17,18,28,29,
30, the flow back to the return line T is immediately cut off, so the pressures in the passages 62 and 23 become equal, the set pressure of the relief valve 25 becomes the normal setting value, and the fatigue life of other actuators is reduced. is not inhibited. The pilot oil flow flowing through the above-mentioned throttles 21 and 22 uses part of the discharge oil of the main pumps 1 and 2, but the same result can be obtained by providing the throttles 21 and 22 in the discharge line of the pilot pump 60 shown in FIG. It becomes a function. 61 is a relief valve that determines the upper limit of the pressure of the pilot section. As shown in Fig. 3, the mechanism for increasing the normal set pressure of the relief valve 25 is to install a pilot relief valve 71 that determines the normal set pressure and a pilot relief valve 72 that determines the pressure at the time of pressure increase in the vent line of the relief valve. 23
Valve 7 that switches to the closed position when the pressure increases due to switching of either or both of travel operation valves 3 and 6.
The same function can be obtained by connecting the pilot relief valve 71 to 0. That is, when pressure is built up in the passage 23 and not in the passage 62, the valve 70 is in the closed position, and the pressure in the relief valve 25 is determined by the pilot relief valve 72, and the pressure increases during running. Further, when the same pressure is established in the passage 23 and the passage 62, the valve 70 is in the open position by the spring force, and the pressure of the relief valve 25 is reduced by the pilot relief valve 71 which determines the normal set pressure lower than the pilot relief valve 72. The discharge pressure of pumps 1 and 2 does not normally exceed the set pressure. Also, the third
The pilot oil flow flowing through the throttles 21 and 22 in the boost switching mechanism shown in the figure uses the discharge oil of the main pumps 1 and 2, but the pilot pump 60 shown in FIG.
The same function can be achieved even if throttles 21 and 22 are provided in the discharge line.

[Effect of idea]

The set pressure of the relief valve that determines the circuit system pressure is increased when driving any or all of the left and right travel motors, and the product of the pressure value after the pressure increase and the motor capacity is the pressure value before the pressure increase and the motor capacity. By setting the capacity of the motor small so as to be equivalent to the product, it is possible to obtain the same motor starting torque as before and to increase the vehicle speed when the vehicle body is in a steady running state. Furthermore, when an actuator other than the travel motor is linked to travel, the pressure increase of the relief valve can be canceled so that the fatigue life of the actuator other than the travel motor is not impaired.

[Brief explanation of drawings]

1 to 4 show different embodiments of the hydraulic circuit of the construction machine of the present invention. 1, 2...pump, 3-9...operation valve, 10,
11... Travel motor, 12-15... Other actuators, 16-18, 27-30... Pilot section, 19, 20... Check valve, 21, 22
...Aperture, 23, 50, 51, 53, 62, 65
... Passage, 25 ... Relief valve, 25a ... Spring, 26 ... Both rod cylinders, 26a, 26b
...Pressure chamber, 26c...Rod, 61...Relief valve, 70...Switching valve, 71, 72...Pilot relief valve, 60...Pump.

Claims (1)

[Scope of utility model registration request] In a hydraulic circuit having two pumps that drive traveling crawlers, traveling motors individually installed in the discharge circuits of the pumps, other actuators, and operation valves that drive and operate each actuator, Each operation valve is provided with a pilot valve that switches together with the operation valve body, and further provided with a device for adjusting the pressure setting value of a circuit relief valve that determines the upper limit value of the discharge pressure of the pump, and one or two of the travel motors The adjusting device is operated so that the pressure of the relief valve increases when the drive motor is operated, and the adjusting device is operated so that the pressure increase of the relief valve is released when the drive motor or other actuator is operated. A hydraulic circuit for construction machinery, characterized in that it is operated by.