JPH0646041B2 - Hydraulic actuator variable actuator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator operating device that simultaneously changes the output and speed of a hydraulic actuator that is operated by pressure oil of a variable displacement hydraulic pump, according to an external command.

2. Description of the Related Art Conventionally, in a system that operates an actuator such as a hydraulic cylinder or hydraulic motor by switching hydraulic oil discharged from a variable displacement hydraulic pump with a hydraulic switching valve, the load of a prime mover that drives the hydraulic pump is applied to the actuator. A method has been adopted in which the output of the prime mover is efficiently used and the system is rational by keeping the output almost constant regardless of the load pressure.

For example, in the circuit diagram of the hydraulic operation system shown in FIG. 7, the discharge pressure oil of the first hydraulic pump 2 driven by the prime mover 1 flows into the hydraulic pressure switching valve group A, and the hydraulic pressure switching valves 8, 9, 1
When 0 and 11 are switched, the actuator connected to them is operated, the discharge pressure oil of the second hydraulic pump 3 flows into the hydraulic switching valve group B, and when the hydraulic switching valves 12, 13, 14 and 15 are switched, Actuated actuators connected to them,
The pressure oil discharged from the pilot pump 4 passes through the oil passage 7 and is used as a hydraulic pressure source for various operating systems. Of these hydraulic pumps, the pilot pump 4 constantly generates a constant pressure and a constant amount of pressure oil, so that the load on the prime mover 1 is constant, while the first and second hydraulic pumps 2 and 3 have variable displacements. Type hydraulic pumps that discharge a large amount of pressure oil to increase the operating speed of the actuator when the load pressure of the actuators belonging to each is low, but decrease the discharge oil amount when the load pressure of the actuator increases. The flow rate control valves 26 and 27 are controlled so that the synergistic product of the discharge pressure and the oil amount is always maintained at a constant value and the absorption power for driving the hydraulic pump is constant.

Generally, in such an operating circuit, when the discharge pressure of the hydraulic pump is P kg / cm ² , the discharge oil amount is Ql / min, and the absorption power of the hydraulic pump at that time is W, In order to make the value of W constant, it is necessary to make the value of the variable P × Q in the above equation constant. From this, the flow control valves 26 and 27 are the first and second hydraulic pumps 2,
If the discharge pressure of No. 3 rises, the discharge oil amount is changed in inverse proportion to the value, and FIG. 8 is a diagram showing the relationship between the discharge pressure P and the discharge oil amount Q at this time. When the load pressure of is relatively low P ₁ or less,
The operation is performed with the maximum discharge oil amount Q ₁ , the discharge oil amount Q decreases as the load pressure P gradually increases, and when the maximum discharge pressure P ₂ is reached, the discharge oil amount Q ₂ is reached, and the value of the absorption power W Is always almost constant, so that the prime mover 1 is not overloaded, and the so-called constant horsepower operation is maintained so that an efficient operating state including the hydraulic operating system is maintained. There is. Furthermore, the first and second
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 hydraulic pumps 2 and 3, respectively, and the discharge circuit pressure is set to P due to an actuator overload or some unexpected cause. It is designed not to have an abnormally high pressure of ₂ or more. Therefore, the discharge oil amount of the hydraulic pump 2 or 3 in the actuator operating circuit as described above is Q ₁ or more and Q
At the same time, the discharge pressure cannot be less than ₂ and the discharge pressure cannot exceed P ₂ .

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a working machine or device equipped with a hydraulic actuator, if an actuator having a cross-sectional area with a sufficient output required for design is used, the operating speed of the hydraulic oil will be reduced at a limited discharge amount. Since it is slow and uneconomical, it is generally aimed to have an actuator that corresponds to the expected average load and to perform the work most effectively in a level work, but depending on the work object and the content May cause an unexpected load.In such a case, change the working conditions in consideration of the frequency and size, or replace it with a larger capacity machine or device, which is an uneconomical measure. I was doing

For example, in order to perform excavation work with the hydraulic backhoe 40 shown in FIG. 5, the boom 41, the arm 42, and the bucket 43 are
The boom cylinder 44, the arm cylinder 45, and the bucket cylinder 46 operate to excavate the earth and sand at the blade edge of the bucket 43, and when changing the excavation location, the vehicle body is moved by a traveling hydraulic motor (not shown). Output is sufficient for excavation resistance and running resistance of general earth and sand, but as shown in the figure, there was a mixture of cobblestones 47 with excavation resistance higher than expected in the soil. For example, when only the boulder 47 is removed and the backhoe 40 is in time enough, the driver's skill and a long time are taken to dig up the boulder 47, or the impact is applied. They were taking measures such as removing them or otherwise throwing in larger machines.

Also, when a deep hole is set up in the ground by the machine 48 equipped with the deep dig clamshell shown in FIG. 6, the main boom 49,
Intermediate boom 50, arm 51 to main boom cylinder 5
4, the intermediate boom cylinder 55 and the arm cylinder 56 are operated, and the clamshell bucket 53 attached to the tip of the arm 51 via the extension beam 52 is vertically lowered to the position of the predetermined deep hole to scrub the soil at the bottom of the hole. It is grasped by the shell bucket 53 and carried out to the ground, but the extension beam 52 becomes longer as the depth of excavation of the deep hole progresses, and its own weight also increases, and when it reaches the specified maximum length, the earth and sand grasped by the clamshell bucket 53 is removed. Although it has enough actuator capacity to lift it, it does not have much margin. Therefore, when the spring water and the earth and sand are muddy at the bottom of the hole, an extra pulling force is required only at the moment when the bucket 53 is ground cut from the bottom of the hole, and the main boom cylinder 54, the intermediate boom cylinder 55, the arm cylinder 56, etc. However, there is a tendency that the capacity insufficiency phenomenon occurs only for a short time, so it is often the case that a larger-sized deep-drilling clamshell body has to be thrown in.

In view of such a problem, the present invention makes the best use of the capacity of a standard machine or equipment in a level operation, and during a work cycle, operates for a short time in response to a request for an actuator output higher than usual that happens to occur. It is an object of the present invention to realize a hydraulic actuator variable actuation device that can arbitrarily cope with this according to the intention of a person, and reduce the shock overload exerted on the machine / device.

Means for Solving the Problems This invention has taken the following means in order to solve the above problems. That is, (a) In a hydraulic circuit that supplies the hydraulic pressure switching valve with the discharge pressure oil of a variable displacement hydraulic pump equipped with a flow control valve that has the function of increasing or decreasing the discharge oil amount in inverse proportion to the discharge pressure, and operating the hydraulic actuator. B) In addition to the receiving unit having a function of limiting the discharge oil amount in inverse proportion to the magnitude of the self-discharge pressure as a signal, the flow control valve receives the variable capacity when an external signal acts. An external signal receiving unit is provided that has a function of limiting the maximum discharge oil amount of the hydraulic pump of a fixed type to a predetermined amount.

C) A relief valve provided in the oil passage on the discharge side of the variable displacement hydraulic pump to prevent the pressure in the oil passage from exceeding the set value peculiar to the circuit is connected to the relief valve of the oil passage when an external signal acts. A boost command receiving unit is provided that gives a function of boosting the set value by a predetermined value rather than the specific installation value.

D) Near the driver's seat, a signal means that can output external signals such as pilot pressure only during artificial operation, such as an automatic reset switch or pedal, will be installed.

E) When an external signal is output from the signal means, the external signal is simultaneously transmitted to the external signal receiving section of the flow rate control valve of the variable displacement hydraulic pump and the boost command receiving section of the relief valve.

The external signal obtained by operating the signal means such as a switch or pedal of the automatic reset type near the driver's seat is the external signal receiving part of the flow control valve of the variable displacement hydraulic pump and the boost command receiving part of the relief valve. And the maximum discharge oil amount of the variable displacement hydraulic pump is limited by a predetermined amount, and further, the maximum discharge oil amount is reduced in accordance with the discharge pressure at that time, and at the same time, the relief valve of the relief side oil passage of the hydraulic pump is reduced. The relief set pressure is increased by a predetermined value above the specific set value.

Therefore, the operating speed of the actuator operated by the discharge pressure oil is slowed only while the signal means is operated, and when the load applied to the actuator increases at this time, the constant horsepower operation according to the load pressure is performed. Works with
When the load further increases, pressure oil higher by a predetermined value is supplied, so that an output larger than a normal actuator output can be obtained. Therefore, in this hydraulic actuator variable actuation device, the capacity of the hydraulic actuator is increased only during the operation of the operating means against an instantaneous overload, and even when the load pressure of the hydraulic actuator is small, its operating speed, that is, the hydraulic pump. It reduces the amount of oil discharged from the engine, prevents the prime mover from becoming overloaded, and
The shock load during operation of the work implement is reduced.

Embodiments Hereinafter, the present invention will be described as an example when it is applied to an actuator operating hydraulic circuit of a hydraulic excavator which is most practically used.

FIG. 1 is a diagram showing an electric / hydraulic circuit equipped with the present invention on a standard crawler type hydraulic excavator, and 1 is a prime mover for driving 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 passes through the oil passage 5 and the hydraulic switching valve group A, respectively.
Pressure oil is supplied to the hydraulic pressure switching valve group B through the oil passage 6 and to the oil passage 7. The pressure oil that has flowed into the hydraulic pressure switching valve group A is supplied to the hydraulic pressure switching valves 8, 9, 10, 11 for left traveling, arm first speed, turning, and boom second speed, and the hydraulic pressure switching valves 8, When 9, 10, 11 are switched, the respective actuators are operated, and when neutral, the oil passes through the center bypass passage and the return oil passes through oil passages 36 and 38 to the tank 2
Returning to No. 9, the hydraulic fluid that has flowed into the hydraulic pressure switching valve group B is supplied to the hydraulic pressure switching valves 12, 13, 14, 15 for the right traveling, the boom first speed, the bucket, and the arm second speed. When the hydraulic pressure switching valves 13, 14, 15 are switched, the respective actuators are operated, and when neutral, they pass through the center bypass passage and return oil returns to the tank 29 through the oil passages 37, 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 for each operating system by the oil passage 7 or its branched oil passage 28. Guided by control equipment.

The first and second hydraulic pumps 2 and 3 are variable displacement hydraulic pumps, which use the discharge pressure as a signal and limit the discharge oil amount in inverse proportion to the magnitude of the signal to absorb power. A receiving portion, which is a first pilot oil chamber C having a function of imparting a so-called constant horsepower performance, which maintains a constant value, and exerts an acting force in a direction of reducing a maximum discharge oil amount by a predetermined value when an external signal from the outside acts. It has flow control valves 24 and 25 which are modifications of the known technology and are provided with an external signal receiving section which is a second pilot oil chamber D. FIG. 2 is a diagram showing changes in the discharge oil amounts of the first and second hydraulic pumps when a pressure signal acts on the two pilot oil chambers C and D of the flow control valves 24 and 25. The discharge pressure of the hydraulic pump acts on C as a pilot pressure, and the discharge pressure is P ₁
Alternatively, the amount of discharged oil is Q ₁ or less, and as the discharge pressure exceeds P ₁ and becomes P ₂ , the discharged oil amount Q ₁ to Q ₂
When the pressure exceeds P ₂ and exceeds the peculiar normal set pressure of the relief valves 22 and 23, the pressure oil is released into the relief valve 2
It is the same as in FIG. 8 described above that the oil is relieved at 2, 23 and directly flows into the tank 29 through the oil passages 36, 37, 38, etc., but an external signal is sent only to the second pilot oil chamber D. When it works, the discharge oil amount Q is limited to the maximum discharge oil amount Q ₁ to Q ₃ which is smaller than that, and from this state, the set pressure of relief valves 22 and 23, which will be described later, is more than the set point. As the load increases on the actuator in a state where the pressure can be increased by a predetermined value and the load pressure increases, the pressure in the first pilot oil chamber C also exceeds P ₂ and becomes P ′.
Minimum discharge oil amount is as decreases to less Q 'than Q _2.

Further, the relief valves 22 and 23 provided above branched from the oil passages 5 and 6 are usually set so as to have a specific circuit pressure, but when an external signal is added to the relief valves 22 and 23 to operate, the above-mentioned specific relief pressures are provided. This is a modification of a known relief valve having a boost command receiving portion, which is a pilot oil chamber E having a function of setting the set value of the circuit pressure to a higher pressure by a predetermined value. Further, the branch oil passage 28 of the oil passage 7 of the operation system hydraulic power source is excited and is switched to the G position, and the oil passage 3 connecting the oil passage 28 to the outlet port.
9, the oil passage 28 is closed when it is in the F position without being excited, and the oil passage 39 is connected to the tank 29 via the oil passage 38.
Is connected to an electromagnetic switching valve 30 that forms a passage communicating with the electromagnetic switching valve 30. The electromagnetic switching valve 30 is energized by the power supply device 33 only when the automatic reset switch 32 is forcibly closed, and the F position to the G position. Further, the oil passage 39 connected to the outlet port is extended and branched so that the pilot oil chamber E, which is the pressure command receiving portion of the relief valves 22 and 23, and the flow rate control, respectively. Valve 24,
25 to the second pilot oil chamber D, which is the external signal receiving unit. Therefore, the pilot pump 4, the oil passages 28, 39, the electromagnetic switching valve 30, the switch 32, the power source 33 and the like constitute a signal generating means for the external signal receiving section D and the boost command receiving section E.

Reference numerals 19, 19'20, 20 ', 21 and 21' are port relief valves, and are respectively the arm first speed hydraulic switching valve 9, the boom first speed hydraulic switching valve 13, and the bucket hydraulic switching valve 14. Even if is in the neutral position, if an abnormally high binding pressure occurs in the actuator circuit due to an external force, it is for protecting each part. The set pressure is set in the pilot oil chamber E of the relief valves 22 and 23. Set slightly higher than the relief pressure when the boost command signal is applied.

Next, the operation of the electric / hydraulic circuit configured as described above will be described.

In the earth and sand excavation work as shown in FIG. 5 or FIG. 6, normally, the switch 32 is not operated, and the open state is set, that is, the pilot oil chambers D and E are communicated with the tank 29, like a normal standard hydraulic excavator. Although the work will be performed with the force and speed, the excavation force and the pulling force are slightly increased in the case of sudden excessive resistance due to obstacles during excavation in Fig. 5 and ground cutting in Fig. 6, etc. Moreover, when the switch 32 is closed and the electromagnetic switching valve 30 is energized when it is needed only for a short time, the electromagnetic switching valve 30 switches from the F position to the G position, so that the pressure oil in the oil passage 7 becomes the oil passages 28, G. The pressure command receiving portion E of the relief valves 22 and 23 passes through the position passage and the oil passage 39.
And the external signal receiving portion D of the flow control valves 24 and 25, the discharge oil amount Q of the first and second hydraulic pumps 2 and ₃ is limited from Q ₁ to Q _{3 in} FIG. Since the set pressures of the relief valves 22 and 23 can be increased by a predetermined value designed in advance, there is no relief until that value, that is, the discharge pressure P in FIG. 2 becomes P ′, and load pressure of the hydraulic actuator P beyond the P ₂ 'as the approaches, the discharge oil amount by the action of the flow control valve is also limited proportionately, remained 3 horsepower constant operating conditions, eventually Q' becomes.

This means that the pump driving prime mover 1 does not become overloaded under any circumstances, but in particular, when a high load is applied to the actuator, its operating speed is reduced in proportion to the load pressure. It is possible to reduce the dynamic load applied to the actuated body, the main body, and the like to protect the constituent members in terms of strength, and to efficiently improve the capacity of the working device as needed for a short time.

Further, when the cobblestone 47 shown in FIG. 5 is excavated, or when floating stones are being excavated, the impact force may be applied by using the bucket 43. However, since the load pressure is low, a large amount of pressure is applied to the hydraulic actuator for the working device. Pressure oil is supplied, the operating speed is increased, and the working device and the main body are adversely affected in terms of durability, but at this time, the amount of hydraulic oil discharged from the hydraulic pump is limited to Q ₁ to Q ₃ described above. This can be avoided by taking the following measures.

The object of the present invention is to temporarily limit the maximum operating speed of the actuator and to improve the operating force at the same time.
Since it should not be used all the time, it is desirable that the switch 32 in the above-mentioned embodiment is operated for a short time whenever necessary and is normally opened. Therefore, as shown in FIG. 3, it is advisable to employ an automatic resetting switch 32 'for the push button provided on the top of the grip 35 of the operating lever 34 for operating the hydraulic switching valve. Instead of the electromagnetic switching valve 30, a foot pedal and an automatic return type normally closed position switching valve 31 shown in FIG. 4 may be used as long as they do not deviate from the above requirements.

In addition, in the above embodiment, the operating system of the front attachment of the hydraulic excavator has been described, but the present invention is not limited to the hydraulic excavator, and various works can be performed by a hydraulic actuator, including a movable type and a stationary type mechanical device. It can also be applied to hydraulic actuator operating circuits for construction machines such as tractor shovels, crushers, industrial machines such as hoisting and lending machines and transport machines.

Further, the pilot oil chamber serves as an external signal receiving portion for limiting the maximum discharge oil amount of the flow control valve attached to the variable displacement hydraulic pump in the embodiment of the present invention and a boost command receiving portion for increasing the set pressure of the relief valve by a predetermined value. The pilot pressure oil to be supplied to this pilot oil chamber is designed to open and close the oil passage from the hydraulic power source outside the main circuit by operating means including the electromagnetic switching valve. Of course, the signal medium in the present invention is hydraulic, but the signal medium in the present invention is not limited to this, and any conventional pneumatic, electric, mechanical,
It is natural that there is no problem even if the medium is a combination thereof.

EFFECTS OF THE INVENTION The present invention reduces the maximum operating speed of the hydraulic actuator at low load for a short time arbitrarily and easily by the driver's will, and during that time, the load pressure of the hydraulic actuator is reduced to the normal maximum value. In a working condition that is instantly required to be higher than that, its operating speed is operated at a speed according to the magnitude of the load pressure, and the hydraulic actuator can efficiently improve its instantaneous operating force. There is no need to prepare a large-sized work machine or equipment due to a slight lack of capacity in a very short time, which is extremely rare, and to give the driver / operator no frustration. Both the maximum speed at light load and the minimum speed at heavy load decrease when the operation is increased, so it is suitable for work that requires accurate operation, and particularly, the striking force is used. Work, high load work, in particular, the occurrence of severe dynamic stress on the constituent members is reduced, but the working capacity is not reduced, and the durability of the machine is not adversely affected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric / hydraulic circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a characteristic diagram showing the relationship between the discharge pressure and the discharge oil amount of the variable displacement hydraulic pump used in the present invention, FIG. 3 is a perspective view showing an arrangement example of switches, and FIG. 4 is a hydraulic circuit of the present invention. FIG. 5 and FIG. 6 are views showing another embodiment of the switching valve used, and FIG. 7 and FIG. 7 are side views showing working conditions when the hydraulic shovel body is equipped with a backhoe and a deep dig clamshell as front attachments, respectively. FIG. 8 is a hydraulic circuit diagram of a conventional hydraulic excavator, and FIG. 8 is a characteristic diagram of the discharge pressure of a conventional variable displacement hydraulic pump for a hydraulic excavator. 22 ... Relief valve 23 ... Relief valve 24 ... Flow control valve 25 ... Flow control valve 30 ... Electromagnetic switching valve 31 ... Normally closed switching valve 32 ... Switch

Claims (1)

[Claims] Claim: What is claimed is: 1. A flow control valve attached to a pump for controlling a discharge oil amount of a variable displacement hydraulic pump for a hydraulic power source of a hydraulic operating circuit for operating a hydraulic actuator by switching pressure oil by a hydraulic switching valve. An external signal receiving unit that gives a function of limiting the maximum discharge oil amount of the pump to a predetermined amount when an external signal acts, in addition to a receiving unit that gives a function of increasing or decreasing the discharge oil amount according to the discharge pressure signal of A relief valve provided with a boost command receiving portion having a function of boosting the original relief set pressure by a predetermined value when an external signal acts in the middle of the oil passage through which the discharge side oil passage of the pump communicates with the tank,
A signal means for outputting the external signal only when arbitrarily operated, and a signal from the signal means is simultaneously supplied to an external signal receiving portion of the flow control valve and a boost command receiving portion of the relief valve. Variable actuator for hydraulic actuator.