JPH0477801B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application This invention relates to the output and speed of a hydraulic actuator operated by pressure oil of a variable displacement hydraulic pump.
The present invention relates to a hydraulic actuator actuating device that simultaneously changes according to external specifications.

Conventional technology Conventionally, in systems in which the discharge pressure oil of a variable displacement hydraulic pump is switched by a hydraulic switching valve to operate an actuator such as a hydraulic cylinder or a hydraulic motor, the load of the prime mover that drives the hydraulic pump is applied to the actuator. Regardless of the load pressure, a method has been adopted in which the output of the prime mover is efficiently utilized by keeping it almost constant, and the system is made rational.

For example, in the circuit diagram of the hydraulic operating system shown in FIG. 7, the pressure oil discharged from the first hydraulic pump 2 driven by the prime mover 1 flows into the hydraulic switching valve group A,
When the hydraulic switching valves 8, 9, 10, and 11 are switched, the actuators connected to them are operated, and the pressure oil discharged from the second hydraulic pump 3 flows into the hydraulic switching valve group B, and the hydraulic switching valves 12, 13, and 14 are switched. , 15 are switched, actuators connected thereto are operated, and the pressure oil discharged from the pilot pump 4 is used as a hydraulic power source for various operating systems through an oil passage 7. Of these hydraulic pumps, the pilot pump 4 always generates a constant pressure and a fixed amount of pressure oil, so the load on the prime mover 1 is constant;
The first and second hydraulic pumps 2 and 3 are variable displacement hydraulic pumps, and when the load pressure of the actuator belonging to each is low, they discharge a large amount of pressure oil to accelerate the operating speed of the actuator. The flow rate control valve 26 is operated so that the multiplicative product of the discharge pressure and the oil volume is always maintained at a generally constant value by reducing the discharge oil volume when the pressure increases, and the absorbed power for driving the hydraulic pump is kept constant. , 27 are provided and controlled.

Generally, in such an operating circuit, if the discharge pressure of the hydraulic pump is PKg/cm ² , the discharged oil amount is Q/min, and the absorbed power of the hydraulic pump at that time is W, then W = P・Q/450. In order to keep the value of W constant, it is necessary to keep the value of the variable P×Q in the above equation constant. Therefore, if the discharge pressure of the first and second hydraulic pumps 2 and 3 increases, the flow rate control valves 26 and 27 change the discharge oil amount in inverse proportion to that value. A diagram showing the relationship between P and the discharged oil amount Q is shown in Fig. 8. When the load pressure of the actuator is relatively low P ₁ or lower,
It is operated at the maximum discharge oil amount _Q1 , and as the load pressure P gradually increases, the discharge oil amount Q decreases.
When the maximum discharge pressure _P2 is reached, the discharge oil amount becomes _Q2 ,
By keeping the value of the absorbed power W almost constant at all times, so-called constant horsepower is achieved so that the prime mover 1 is not overloaded and an efficient operating state including the hydraulic system is maintained. I try to do it while driving. Furthermore, relief valves 16 and 17 are provided in the branch oil passages of the oil passages 5 and 6 on the discharge side of the first and second hydraulic pumps 2 and 3, respectively, so that the discharge circuit pressure is prevented from overloading the actuator or by any other reason. It is designed to prevent abnormally high pressures of P ₂ or higher from occurring due to unforeseen circumstances. Therefore, the amount of oil discharged from the hydraulic pump 2 or 3 in the actuator operating circuit as described above cannot be greater than _Q1 and less than _Q2 , and at the same time, the discharge pressure cannot exceed _P2 .

Problems to be Solved by the Invention In working machines and devices equipped with hydraulic actuators, if an actuator is designed with a cross-sectional area that allows sufficient margin for the required output, the operating speed will be reduced due to the limited amount of discharged oil. Therefore, the goal is to have an actuator that is suitable for the average load that can be assumed, and to be able to perform the work most effectively in average work. Unexpected loads may occur, and in such cases,
Taking into consideration the frequency and size of such incidents, uneconomical countermeasures have been taken, such as changing working conditions or replacing them with machines and equipment of larger capacity.

For example, to perform excavation work with the hydraulic bucket 40 shown in FIG. When excavating and changing the excavation location, the vehicle body is moved by a travel hydraulic motor (not shown), and the output of each actuator has sufficient capacity to withstand the general excavation resistance and travel resistance of earth and sand. However, as shown in the figure, when there is a mixture of cobblestones 47 with unexpected excavation resistance in the soil, and this cobblestone 4
If only 7 is removed, the capacity of the backhoe 40 will be enough to make it in time, then the driver's skill and time are required to dig around the boulder 47 and remove it, or else an even larger machine is used. Then he took various measures.

Furthermore, when setting up a deep hole in the ground using the machine 48 equipped with a deep-digging clamshell shown in FIG.
5. The arm cylinder 56 is actuated to vertically lower the clam shell bucket 53 attached to the tip of the arm 51 via the extension beam 52 to a predetermined deep hole position, and remove the earth and sand from the bottom of the hole using the clam shell bucket. The extension beam 52 is grabbed by the extension beam 53 and transported to the ground, but as the depth of excavation of the deep hole progresses, the extension beam 52 becomes longer and its own weight increases.
When it comes to the maximum specified length, Clam Ciel Bucket 53
Although the actuator has enough capacity to lift the dirt it has grabbed, it does not have that much leeway. Therefore, when the bottom of the hole is muddy with spring water and soil, extra lifting force is required only at the moment when the bucket 53 is cut off from the bottom of the hole, and the main boom cylinder 54, intermediate boom cylinder 55, arm cylinder 56, etc. Since there is a tendency for a slight and short-term lack of capacity to occur, it is often necessary to use a larger body for deep-digging clam shells.

In view of these problems, the present invention makes full use of the capabilities of standard machinery or equipment during normal work, and allows operators to respond to above-average actuator output demands that happen to occur during a work cycle for a short period of time. The object of the present invention is to realize a hydraulic actuator variable actuation device that can respond to this at will and also reduce the dynamic overload exerted on machinery and equipment.

Means for Solving the Problems In order to solve the above problems, the present invention takes the following measures. That is, a) In a hydraulic circuit that supplies the discharge pressure oil of a variable displacement hydraulic pump equipped with a flow control valve that has a function of increasing or decreasing the amount of discharged oil in inverse proportion to the discharge pressure to a hydraulic switching valve to operate a hydraulic actuator. (b) In addition to the receiving part for the self-discharge pressure of the hydraulic pump, the flow rate control valve receives an arbitrary external signal to control the maximum discharge oil amount of the hydraulic pump by a predetermined amount regardless of the self-discharge pressure. An external signal receiving section is provided that provides a limiting function.

c) The discharge pressure relief valve, which is installed in the discharge side oil passage of a variable displacement hydraulic pump to prevent the pressure in the oil passage from exceeding a certain set value, has a setting value for the oil passage that is set by an external signal. , a discharge pressure increase command receiving section is provided which provides a function of increasing the pressure by a predetermined value from the above-mentioned constant set value.

d) A port relief valve is installed in the oil passage connecting the hydraulic actuator and the port of the hydraulic switching valve to prevent the pressure in the oil passage from exceeding a specified set value due to confinement pressure, etc. A port pressure boost command receiving section is provided which provides a function of increasing the pressure set value by a predetermined value from the prescribed set value using an external signal.

e) A signal means, such as an automatic return switch or pedal, should be installed near the driver's seat so that it can be freely operated manually and output external signals such as pilot pressure only during operation.

f) The external signal from the above signal means is transmitted to the external signal receiving section of the flow control valve of the variable displacement hydraulic pump, the discharge pressure boost command receiving section of the discharge pressure relief valve, and the port pressure boost command receiving section of the port relief valve. We will take measures that will lead to both at the same time.

Effect The external signal obtained by operating a signal means such as an automatic return switch or pedal from the driver's seat is
When the external signal receiving section of the flow rate control valve of the variable displacement hydraulic pump, the pressure increase command receiving section of the discharge pressure relief valve, and the pressure increase command receiving section of the port relief valve are connected simultaneously, the maximum discharge oil of the variable displacement hydraulic pump can be reached. The amount is limited by a predetermined amount, and is further reduced in accordance with the discharge pressure at that time, and at the same time, the set pressures of the relief valve and the port relief valve are set higher than the normal set value by a predetermined value.

Therefore, the operating speed of the hydraulic actuator, which is operated by the pressure oil discharged from this hydraulic pump, is slower than normal, and when the load pressure of the hydraulic actuator increases in this state, the amount of oil discharged from the hydraulic pump becomes constant horsepower. The pressure decreases along the curve, but the discharge pressure relief valve does not open until the load pressure becomes higher than the normal circuit pressure, and even when the pressure reaches this high pressure, pressure oil is released from the port relief valve. There is no relief, and under the discharge pressure after boosting, the amount of oil delivered by the variable displacement hydraulic pump is much smaller than the normal minimum amount of oil delivered, so the output of the hydraulic actuator increases and the speed decreases. Decrease.

In this way, when the hydraulic actuator's variable actuation device is operated and a large load is applied to the hydraulic actuator, the ability to respond to it is demonstrated, while the dynamic load on the aircraft and equipment is reduced, and the hydraulic When the hydraulic switching valve for operating the actuator is in the neutral state, even if some external force is applied, the neutral holding force increases by the value that the relief setting pressure of the port relief valve increases, but if the operation of the signal means is stopped, Since the set pressure of the port relief valve also returns to normal, no abnormal high pressure is generated in the hydraulic actuator hydraulic oil passage.

Embodiments Hereinafter, an example in which the present invention is applied to a hydraulic circuit of an actuator actuation system of a hydraulic excavator, which is most often used practically, will be explained.

FIG. 1 is a diagram showing an electric/hydraulic circuit in which a standard crawler type hydraulic excavator is equipped with the present invention. 1 is a prime mover that drives a first hydraulic pump 2, a second hydraulic pump 3, and a pilot pump 4; Each of these pumps sucks oil from the tank 29 and supplies pressure oil to the hydraulic switching valve group A through the oil path 5, to the hydraulic switching valve group B through the oil path 6, and to the oil path 7, respectively. supply The pressure oil that has flowed into the hydraulic switching valve group A is supplied to the hydraulic switching valves 8, 9, 10, 11 for left travel, arm 1st speed, swing, and boom 2nd speed. When 9, 10, 11 are switched, actuate each actuator,
When in neutral, the return oil passes through the center bypass passage and returns to the tank 29 through the oil passages 36 and 38, and the pressure oil that flows into the hydraulic switching valve group B is used for right travel, boom 1st speed, bucket It is supplied to the hydraulic switching valves 12, 13, 14, 15 for 2nd speed, and when the hydraulic switching valves 13, 14, 15 are switched, the respective actuators are operated, and when in neutral, it passes through the center bypass passage, The return oil returns to the tank 29 through oil passages 37 and 38. On the other hand, the pressure oil discharged from the pilot pump 4 mainly serves as a hydraulic pressure source for the operating system, and is regulated to a predetermined pressure by the relief valve 18 and is used for each operating system through the oil path 7 or its branched oil path 28. Guided by control equipment.

In addition, the first and second hydraulic pumps 2 and 3 are variable displacement hydraulic pumps, which limit the amount of oil discharged in inverse proportion to the discharge pressure to keep power absorption constant.
The first pilot oil chamber C provides so-called constant horsepower performance, and the second pilot oil chamber D exerts an acting force in the direction of reducing the maximum oil discharge amount by a predetermined value when an external pressure signal is applied. Flow control valve 2 modified from known technology with a receiving section
4.25. This flow control valve 24, 2
Figure 2 is a diagram showing the change in the amount of oil discharged from the first and second hydraulic pumps when a pressure signal acts on the two pilot oil chambers C and D in Figure 5. The discharge pressure is
The discharge oil amount when P ₁ or less is Q ₁ ,
As the discharge pressure exceeds P ₁ and becomes P ₂ , the discharge oil amount Q ₁
When the pressure decreases from Q ₂ to Q 2 , exceeds P ₂ , and exceeds the constant regular setting pressure of the relief valves 22 and 23 , the pressure oil is relieved by the relief valves 22 and 23 and flows into the oil passage 3.
6, 37, 38, etc., directly flowing into the tank 29 is the same as in the above-mentioned FIG.
When an external signal acts only on the second pilot oil chamber D, the discharge oil amount Q is limited from the maximum discharge oil amount _Q1 to a smaller amount _Q3 , and from this state, the discharge pressure Relief valve 22, 23
When the load on the actuator increases in a state where the set pressure can increase by a predetermined value from the normal constant set value, the pressure in the first pilot oil chamber C also increases to _P2.
exceeds P', and the minimum discharge oil amount decreases from _Q2 to Q'.

In addition, relief valves 22 and 23 for discharge pressure provided between the oil passages 5 and 6, and port relief valves 57, 57', 58 provided in the middle of a circuit connecting ports of required hydraulic actuators and hydraulic switching valves,
58', 59, 59', etc. normally maintain a specified circuit pressure, and when a pressure signal from the outside acts on the discharge pressure command receiving section and the port pressure boost command receiving section E, the specified circuit pressure is set. This is a relief valve that is a modification of a known technology that has the function of setting the pressure higher by a predetermined value.

In addition, a pilot pump 4 serves as the hydraulic pressure source for the operating system.
When the branch oil passage 28 of the oil passage 7 from the oil passage 7 is energized, the oil passage 28 is communicated with the oil passage 39 connected to the outlet port, and when it is not energized, the oil passage 28 is closed.
It is connected to an electromagnetic switching valve 30 having a passage that communicates oil 39 with an oil passage 38 leading to the tank 29, and the electromagnetic switching valve 30 turns off the power only when an automatic return switch 32 is forcibly closed. Device 3
The oil passage 39 connected to the outlet port is extended and branched to provide relief valves 22, 23 and port relief valves 57, 57', respectively. ，
58, 58', 59, 59', etc., which is a pressure increase command receiving section for discharge pressure and port pressure, and a second pilot oil chamber D, which is an external signal receiving section for flow control valves 24, 25. ing.

In this way, the above-mentioned pilot pump 4, electromagnetic switching valve 30, switch 32, power supply 32, oil passage for pressure oil, etc. can also provide signal means for the external signal receiving section D and the boost command receiving section E for discharge pressure and port pressure. It consists of

Next, the operation of the electric/hydraulic circuit having the above configuration will be explained.

In earth and sand excavation work as shown in Fig. 5 or Fig. 6, normally the switch 32 is not operated and the circuit is open, that is, the pilot oil chambers D and E are in communication with the tank 29, so it is not possible to use a normal standard hydraulic excavator. The work will be carried out with the same force and speed as in Figure 5, but in cases such as sudden excessive resistance due to obstacles during excavation as shown in Figure 5, or when cutting the ground as shown in Figure 6, the digging force and pulling force will be small. When it is needed for only a short time, the switch 32 is closed and the electromagnetic switching valve 30 is energized, and the electromagnetic switching valve 30 is switched from the F position to the G position, so that the pressure oil in the oil passage 7 is transferred to the oil passage 28, Passing through the G position passage and the oil passage 39, the relief valves 22, 23 and the port relief valves 57, 57',
Since it acts on the pilot oil chambers E such as 58, 58', 59, 59' and the second pilot oil chamber D of the flow control valves 24 and 25, the maximum discharge oil amount of the first and second hydraulic pumps 2 and 3 is is limited from Q ₁ to Q ₃ in FIG.
Since the set pressures such as 9 and 59' can be increased by a predetermined value planned in advance, the load increases until the discharge pressure P in Fig. 2 reaches P'. Also, as the load pressure of the hydraulic actuator exceeds P ₂ and approaches P′, the amount of discharged oil is proportionally limited by the action of the flow control valve.
Finally, it becomes Q'.

This means that the pump driving prime mover 1 will not be overloaded under any circumstances, but especially when a high load is applied to the actuator, by slowing down its operating speed in proportion to the load pressure, By reducing the dynamic load applied to the actuated body, main body, etc. and protecting the strength of the structural members, the performance of the working device can be efficiently improved in a short period of time as needed. Also, 57, 57',
58, 58', 59, and 59' are port relief valves, and in this embodiment, they are respectively the arm first speed hydraulic switching valve 9 and the boom first speed hydraulic switching valve 1.
3. Even though the bucket hydraulic switching valve 14 is in the neutral position, if abnormally high confinement pressure is generated in the actuator circuit due to external force, this is to protect each part, and the set pressure is always
The relief pressure is set slightly higher than that of the relief valves 22 and 23 to avoid interference with each other, and when the pressure signal does not act on the pilot oil chamber E, the normal set pressure is maintained. When in use, it provides relief when locking pressure is generated due to external force, which occurs relatively frequently, and protects the actuator and associated working equipment.

Since the purpose of the present invention is to temporarily improve the actuator operating ability and not to be used constantly, the switch 32 in the above embodiment is operated for a short time each time it is necessary, and is normally open. is desirable. Therefore, as shown in Figure 3,
Grip 35 of the operating lever 34 for operating the hydraulic switching valve
It is preferable to employ a push button type automatic return type switch 32' provided at the top. In addition, the electromagnetic switching valve 30
Instead, as long as it does not deviate from the above requirements, the fourth
A foot pedal or a normally closed switching valve 31 of automatic return type may be used as shown in the figure.

Although the above embodiment describes the actuation system of the front attachment of a hydraulic excavator, the present invention is not limited to hydraulic excavators, and includes mobile and stationary mechanical devices, and can be used in various ways using hydraulic actuators. Hydraulic actuator operating circuits for construction machines such as tractor shovels and crushers, and industrial machines such as cargo lifters and transporters, which perform work, and in particular, hydraulic cylinders that rotate articulated beams such as booms and arms, and their This can be effectively used when an instantaneous operating force as described above is required in an operating circuit where locking pressure is likely to occur, such as an oil passage connecting a hydraulic switching valve port.

Further, in the embodiment of the present invention, the pilot oil chamber serves as an external signal receiving section for limiting the maximum discharge oil amount of the flow control valve attached to the variable displacement hydraulic pump and a pressure increase command receiving section for increasing the set pressure of the relief valve by a predetermined value. The pilot pressure oil supplied to the pilot oil chamber is controlled by operating means including an electromagnetic switching valve to arbitrarily open and close the oil passage from a hydraulic source outside the main circuit, but the signal medium at this time is Of course, the signal medium in the present invention is not limited to this, but any conventional pneumatic, electric, mechanical, or combination of these may be used as long as it can perform the same action. It goes without saying that there is no problem even if the medium is a combination of media.

Effects of the Invention The present invention can arbitrarily and easily reduce the maximum operating speed of a hydraulic actuator for a short period of time according to the driver's will, and during that time, the load pressure of the hydraulic actuator can be instantaneously lower than the normal maximum value. Although the operating speed of the hydraulic actuator is slow depending on the magnitude of the load pressure under highly demanding work conditions, it is possible to efficiently improve the instantaneous power of the hydraulic actuator, making it suitable for use in various work machines and other applications. In equipment, etc., it is possible to perform operations that increase the operating force without having to prepare large items due to a slight lack of capacity in a short period of time, which can occur extremely rarely, without making the operator/operator feel irritated. When this occurs, both the maximum and minimum speeds of the actuator are reduced, which prevents severe stress from occurring in the component parts, especially during high-load operations, and during normal operation.
The relief action from the port relief valve, which occurs relatively frequently, has an optimal relief setting value depending on the standard load condition and overload condition, so it is effective in protecting equipment, equipment, etc.

[Brief explanation of the drawing]

FIG. 1 is an electric/hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between discharge pressure and discharge oil amount of a variable displacement hydraulic pump used in the present invention.
Fig. 3 is a perspective view showing an example of the arrangement of switches, Fig. 4 is a view showing another embodiment of the switching valve used in the hydraulic circuit of the present invention, and Figs. A side view showing the working situation when equipped with a backhoe and a deep-digging clam shell, respectively, Figure 7 is a hydraulic circuit diagram of a conventional hydraulic excavator, and Figure 8 is a discharge diagram of a conventional variable displacement hydraulic pump for a hydraulic excavator. It is a pressure discharge oil amount characteristic diagram. 22... Relief valve, 23... Relief valve, 2
4...Flow rate control valve, 25...Flow rate control valve, 30...
...Solenoid switching valve, 31...Normally closed switching valve, 32...
Switch, 57, 57', 58, 58', 59, 5
9'...Port relief valve.

Claims (1)

[Claims] 1. In a hydraulic circuit that operates a hydraulic actuator by switching the discharge pressure oil of a variable displacement hydraulic pump by switching a hydraulic switching valve, a flow control valve that increases or decreases the amount of discharged oil in inverse proportion to the discharge pressure is connected to the pump's self. In addition to the discharge pressure receiving section, an external signal receiving section is provided which provides a function to preferentially limit the maximum discharge oil amount by a predetermined amount regardless of the discharge pressure based on an external signal. The relief valve installed in the passageway is further provided with a discharge pressure increase command receiving part that gives a function to increase the relief set pressure by a predetermined value by an external signal, and is further installed in the oil passage between the hydraulic actuator and the port of the hydraulic switching valve. One or all of the port relief valves
A port pressure increase command receiving section is provided that provides a function of increasing the relief set pressure of the port relief valve by a predetermined amount in response to an external signal, and an external signal can be arbitrarily supplied to each of the receiving sections at the same time. A hydraulic actuator variable actuation device characterized by being provided with a signal means.