JP3474050B2 - Construction machine hydraulic circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydraulic circuit for a construction machine such as a backhoe or a crane.

[0002]

2. Description of the Related Art Generally, a spool type flow control valve produces an unbalanced force in the axial direction depending on the positional relationship between the spool and the port when there is a flow through the valve, but is statically completely hydraulically balanced. Therefore, it is possible to operate with a relatively small operating force. Therefore, a high-pressure and large-volume fluid can be easily handled, and several ports can be arranged in the axial direction of the valve, so that it is particularly suitable for a directional control valve, and is widely used in backhoes and the like.

[0003]

In recent years, many construction machines are of a pilot operated type in which a control valve is operated to be switched by pilot pressure in order to enable light maneuvering with a light operating force. However, in the pilot operation type, the spool is pushed back by the above-mentioned unbalanced force in the axial direction, that is, the fluid force (flow force), and the pilot pressure is lost to the fluid force acting on the spool near the maximum opening degree. The control valve sometimes did not reach the maximum opening despite operating the lever to the maximum. Further, depending on the valve opening degree, pilot pressure and fluid force may oppose each other, causing hunting of the spool. An object of the present invention is to remedy the above-mentioned inconveniences and to make good use of a pilot operated spool valve, which has many advantages.

[0004]

[Means for Solving the Problems]

[Configuration] To achieve the above object, the present invention provides an oil for driving a load device.
Pilot operated type in the pressure oil supply circuit to the pressure actuator
The spool-type flow rate control valve is provided, the pilot-operated
On the spool of the spool type flow control valve of
It acts on the return oil from the user and causes the load device to
Provided with suppressing internal stop the weight movement, the oil
Connection between a pressure actuator and the spool type flow control valve
Pilot operation from the hydraulic actuator side of the oil passage
Type spool-type flow control valve
The outer side that acts on the flow path on the hand side of the internal throttle provided on the
It is characterized in that a partial aperture is provided .

Further, the hydraulic actuator is a hydraulic motor for driving a swivel base equipped with an excavation work device.

[Operation] According to the configuration of claim 1, the details will be described in the section of the embodiment, but since the hydraulic pressure in the control valve can be lowered by the external throttle existing outside the control valve, the control can be performed. It is possible to make the pilot pressure exceed the fluid force that acts on the spool when the valve is fully operated, thus eliminating the problem that the control valve does not fully open even when the operating lever is fully operated. , You will be able to fully open it. or,
As a result, hunting due to antagonism of pilot pressure and fluid force is eliminated, and the hydraulic actuator can be driven well.

The structure of claim 2 has the following operation. In other words, the flow control valve for turning is usually provided with a throttle in the control valve that acts on the return oil passage of the hydraulic oil in order to suppress fluctuations of the swivel base and movement of its own weight during swing-down turning on a sloping ground. Therefore, due to the internal throttle, the above-mentioned fluid force to the spool is remarkably generated. As a countermeasure, increasing the pilot pressure only in the swing control valve (actually weakening the neutral return spring) is conceivable, but if that happens, there is a high risk of component mistakes with other control valves, It is difficult to realize due to assembly. Therefore, by employing a configuration according to claim 1 to the turning hydraulic circuit,
The above-mentioned action due to this also remarkably occurs, and good turning behavior can be obtained.

[Effect] In any of the hydraulic circuits according to the first and second aspects, there is a disadvantage that the valve is hunted or does not reach the maximum opening degree, which is caused by the pilot operation type caused by the spool fluid force.
It was possible to deal with this problem by a simple modification that provided a throttle on the outside of the valve, with a thorough knowledge of the phenomenon, and it was possible to improve economically .

According to the second aspect of the present invention, it is possible to effectively improve the above-mentioned turning control valve, which is particularly likely to cause inconvenience, to a state in which it functions well.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a small turning type backhoe as an example of construction equipment, 1 is an excavation work device, 2 is a swivel platform, 3 is a traveling machine platform, 4 is a crawler traveling device, and 60 is a dozer. Yes, the excavation work device 1 includes a boom 5, an arm 6, a bucket 7, and the like, and the boom 5 has a parallel offset structure in which a proximal boom 5x and a distal boom 5z are connected by an intermediate boom 5y. ing.

FIG. 2 shows an outline of the hydraulic circuit. The control valve 29 for the dozer cylinder and the control valve 3 for the bucket cylinder 7c.
0, control valve 32 for left traveling motor 31, boom cylinder 5
c control valve 9, arm cylinder 6c control valve 10, right travel motor 33 control valve 34, swing motor 45 control valve 3
5, an offset cylinder 36 control valve 37, and a service control valve 38 are provided. Cross-type operation levers 47 and 48 are arranged on the front side of the seat 46 in the operation unit 44, one for boom-bucket and the other for arm-turn.

As shown in FIG. 4, the operating levers 47, 48
Potentiometers 49, 50, 5 for detecting manipulated variables of
1, 52 is connected to the control device 26 and electrically operates each pilot valve 9A, 10A, 30A, 35A. Then, the variable displacement hydraulic pump 8 is discharged to each control valve at a pressure slightly higher than the load pressure.
A load sensing system (hereinafter abbreviated as LS / S) provided with the above, and an auto idle system (hereinafter abbreviated as AI / S) preferable in terms of noise and energy saving are provided and will be described below.

FIG. 3 shows a principle circuit diagram of a main part, which is an extracted portion of the boom cylinder 5c and the arm cylinder 6c surrounded by the phantom line in FIG.
The variable displacement hydraulic pump described above driven by 9;
Is a flow rate adjusting mechanism that variably sets the amount of oil discharged from the hydraulic pump 8 per unit time. The flow rate adjusting mechanism 13 is a horsepower control cylinder 13A that operates with the discharge pressure of the main pump 8.
And the flow control cylinder 13 driven by the adjusting pump 18.
It is composed of B and.

Further, a pressure compensation type flow rate adjusting valve 14 for the adjusting cylinder 13 is provided. 11 is for boom
Is each compensator (pressure compensation valve) for the arm,
Throttle valves 9s and 10s are provided on the supply-side oil passages of the boom control valve 9 and the arm control valve 10. In addition, each control valve 2 other than the control valves 9 and 10 for the boom and the arm
The valve structures (excluding the operating structure) of 9, 30, 32, 34, 35, 37 and 38 are basically the same as the control valves 9 and 10 for the boom and the arm.

The compensators 11 and 12 are located on the lower side of the pressure oil supply to the supply side throttle valves 9s and 10s, respectively.
Further, they are arranged on the upstream side of supplying pressure oil to the actuators 5c and 6c. And each compensator 1
The low pressure side oil passages 11t and 12t are provided on the lower side of the pressure oil supply for the actuators 1 and 12 and for communicating the pressure oil supply upper side portion for the actuators 5c and 6c and the spring side oil chambers of the compensators 11 and 12, respectively. There is.

Throttle valves 9s, which are on the good side of the pressure oil supply to the compensators 11 and 12, and which are provided on the oil passages on the supply side.
High pressure side oil passage 1 that connects the lower side portion of the pressure oil supply for 10 s and the anti-spring side oil chamber of each compensator 11, 12.
1k and 12k are provided. Each compensator 11,1
2, a constant differential pressure reducing valve provided with a compression spring 17 for urging the flow path cutoff side is constituted, and thereby an after-orifice type load sensing circuit is constituted.

There is provided a first low pressure side oil passage 14t which connects the spring side oil chamber 14x of the flow control valve 14 and the pressure oil supply lower side portion to the respective supply side throttle valves 9s, 10s, and each low pressure side oil passage. The first low-pressure side oil passage 14t communicates with 11t and 12t. The second oil passage 15 communicating with the supply ports 9p, 10p of the control valves 9, 10 and the oil chamber on the opposite side of the spring-side oil chamber 14x of the flow control valve 14 from the dedicated oil passage 16
It is in communication with. The pressure applied to the adjusting cylinder 13 when the flow control valve 14 is switched is covered by the dedicated adjusting pump 18 which is driven by the engine together with the hydraulic pump 8. That is, the flow control valve that operates the adjusting cylinder 13 so as to maintain the differential pressure between the first oil passage 14t and the second oil passage 15 that communicates with the supply ports 9p, 10p of the control valves 9, 10 at a predetermined value. 14 is provided with load control means A
Is configured.

Then, the first potentiometer 25 for electrically detecting the operation amount of the accelerator lever 24 for adjusting and setting the engine speed by artificial operation, and the geared motor 22 for driving and operating the governor lever 21 of the governor 20.
And an operation detecting means D for detecting whether or not the hydraulic actuator such as the boom cylinder 5c is operating. When the hydraulic actuator is stopped, the engine speed is changed to the idling side, and when the hydraulic actuator is operating, the engine is operated. The first potentiometer 25 is operated so that the number of rotations is adjusted to the set value by the accelerator lever 24.
Accelerator control means C for linking the geared motor 22 with the geared motor 22.
Is equipped with.

That is, the second potentiometer 2 for feedback for detecting the operation position of the governor lever 21.
7, geared motor 22, first low pressure side oil passage 14 described above
The control device 26 is equipped with a first pressure switch 23 for detecting the pressure of t and an accelerator control means C that links the first potentiometer 25.

That is, the hand accelerator lever 24 in the idling position i is operated to set the engine speed in the working state (usually set to the full accelerator position m), and in the working state, the setting. The engine speed is kept idling, and the engine speed is lowered to the idling state while the accelerator lever 24 is kept set to the position m when not working (no load). In this case, the first pressure switch 23 constitutes the operation detecting means D.

Further, the adjusting means B capable of changing and adjusting the throttle amounts of the throttle valves 9s and 10s is provided, and when the engine speed is increased, the driving speed of the hydraulic actuator such as the boom cylinder 5c becomes faster and the engine speed becomes lower. The control device 26 is provided with a speed control means E that links the second potentiometer 27 and the adjusting means B so that the driving speed of the hydraulic actuator becomes slower when the hydraulic actuator is driven.

The adjusting means B includes the compensators 11, 1
2 low pressure each low pressure oil passage 11t, 12t and 1st low pressure oil passage 14
t is connected via an electromagnetic high-speed response valve 28. The electromagnetic high-speed response valve 28 communicates the low pressure side oil passages 14t, 11t, 12t in the normal position b, and the low pressure side oil passages 11t, 12t in the high pressure position a and the high pressure second oil passage in the high pressure position a. The two-position switching valve structure is constructed so that the oil passage 15 is communicated with the oil passage 21a.

By operating the electromagnetic high-speed response valve 28, the hydraulic pressure acting on the low pressure side oil passages 11t, 12t of the compensators 11, 12 can be set to an intermediate value between the load pressures of the actuators 5c, 6c and the discharge pressure of the pumps. 1
Compensator 1 by the differential pressure maintaining action of 1, 12
The supply pressure to 1 and 12 becomes higher than that when the electromagnetic high-speed response valve 28 is in the normal position b. Then, in order to keep the differential pressure between the first low pressure side oil passage 14t and the discharge pressure of the hydraulic pump 18 constant, the differential pressures at the throttle valves 9s, 10s on the upper side of the compensators 11, 12 are reduced. That is, the throttle amounts of the throttle valves 9s and 10s are controlled to be small, that is, the opening amounts of the control valves 9 and 10 are controlled to be small, and as a result, the amount of oil supplied to the actuators 5c and 6c is reduced and the driving speed becomes slow. It will be. This action is maintained even if the load changes due to the control structure based on the differential pressure between the load pressure and the pump differential pressure.

On the contrary, when the supply pressure to the compensators 11 and 12 is lowered, the differential pressure between the throttle valves 9s and 10s is increased, that is, the throttle amount of the throttle valves 9s and 10s is increased.
That is, the control valves 9 and 10 are controlled to be increased in opening degree, the amount of oil supplied to the actuators 5c and 6c is increased, and the driving speed is increased.

A second potentiometer 27 for detecting the rotation speed of the engine 19, an electromagnetic high-speed response valve 28,
Setting device 3 that variably adjusts the duty ratio of intermittent operation time
9 and a switch 40 for switching between the automatic control mode and the manual control mode are connected to the control device 26, and the compensator 1
The partial pressures of 1 and 12 are configured to be changed and set. That is, by changing the partial pressure, the throttle valves 9s, 1
The adjusting means B capable of changing and adjusting the opening degree of 0 s is configured. The adjusting means B intermittently energizes the electromagnetic high-speed response valve 28, which is urged to return to the high pressure position a, to the normal position b where it is connected to the high pressure oil passage which is the discharge oil passage of the hydraulic pump 8. It has the function of performing intermittent operation and intermittent control without varying the intermittent time.

Explaining the operation of the speed control means E, first, the changeover switch 40 is operated in the automatic control mode to intermittently energize the electromagnetic high-speed response valve 28.
It is linked so that the ratio of the energization time in one cycle of the intermittent time, that is, the duty ratio is reduced when the rotation speed of the engine 19 is low. Accordingly, if it is desired to reduce the turning speed during excavation work, the accelerator lever 24 can be operated to lower the engine speed, and conversely, to increase the drive speed, the engine speed can be increased. .

When it is desired to intentionally change the driving speed of the actuator, the changeover switch 40 is operated in the manual operation mode to set the second potentiometer 27 and the control device 2.
Disconnect from 6. Then, the duty ratio is set by the setting device 3.
The state determined by 9 is set, and the supply pressure to the compensators 11 and 12 can be set to an arbitrary value between the load pressure of the actuators 5c and 6c and the pump discharge pressure by the manual operation of the setting device 39. 5c, 8
The drive speed of c can be adjusted independently of the engine speed.

Next, the hydraulic circuit portion for turning will be described. A hydraulic circuit of the swing hydraulic motor 45 and the swing flow control valve 35 is shown in FIG. 5, and a model cross-sectional view of the control valve 35 for explanation is shown in FIG. In FIG. 6 in the neutral state, 35p is a pump port communicating with the second oil passage 15, 35t is a tank port, and 35c, 35c are oil supply / exhaust oil passages communicating with the hydraulic motor 45, and the input port 53p and the discharge port 53h. , 53h (the same as the compensators 11 and 12 described above) 53. And the spool 35S
The hydraulic chambers 35u, 35u at both ends communicate with the supply / discharge ports 35b, 35b of the pilot valve 35A. 35m
Is a pilot pressure supply port, and 35n is a tank port.

When the turning pilot valve 35A is operated (electromagnetic type or mechanical type) to apply a pilot pressure to the hydraulic chamber 35u on the left side in FIG. 6, for example, the spool 35
S moves to the right in the figure and shifts to the state shown in FIG. That is, the pressure oil from the pump port 35p is transferred to the first land R1.
Is supplied to the turning motor 45 through the compensator 53 and one of the oil supply / exhaust passages 35c, and the return oil is supplied from the other oil supply / exhaust passage 35c to the tank port 35t via the second land R2 formed on the spool 35S. It comes to flow.
The port drawn at a position facing the discharge port 53h is a differential pressure extraction detection port 35k communicating with the first oil passage 14t.

Here, the first land R1 is formed in a state of being slightly narrower than the theoretically required flow passage area from the flow rate of the pressure oil passing therethrough, which causes a differential pressure in LS / S. The throttle valve in the control valve (the above-mentioned throttle valve 9
The same as s, 10s) and 35s. or,
The second land R2 is a communication passage portion ra having a large radial width.
And a throttle passage portion rb having a narrow radial width (see FIGS. 8 and 9), and constitutes an internal throttle (for suppressing fluctuation and movement of own weight) 35q with respect to the return oil passage from the turning motor 45.

In the state shown in FIG. 7, there is an oil flow on the first land R1 on the left side and the second lands R2, R2 on the left and right sides in the figure, and the compensator 53 is on the second land R2 on the left side.
Since the flow from the swivel motor 45 to the swivel motor 45 has almost no pressure drop because it passes through the communication passage portion ra, as shown in FIG. 8, the return flow from the swivel motor 45 to the tank port 35p does not occur in the second land R2 on the right side. By passing through the throttle passage portion rb, a large pressure difference (for example, 100 kg / cm ² ) is generated between the oil supply / drain passage 35c and the tank port 35p. Then, a flow force (fluid force) in the direction of arrow A acts on the spool 35S due to the area difference in the spool axial direction at the right second land R2, that is, the difference in the pressure receiving area at the throttle passage portion rb.

At this time, flow force due to the throttling action can be considered in the first land as well.
The pressure drop at is negligible (a few kg / cm ² ) and is virtually negligible. Then, since a strong flow force acts on the spool 35S which is operated in the arrow B direction by the pilot pressure in the arrow I direction opposite to the arrow B direction, the spool 35S remains as it is (in the conventional hydraulic circuit without the throttle 54). 8), the pilot pressure is lost to the flow force, and depending on the strength of the pump pressure, as shown in FIG. 8, even if the pilot valve 35A is fully operated, the spool 35S of the turning control valve 35 has the maximum stroke (Fig. The position indicated by the phantom line 8) does not occur.

Therefore, as shown in FIG.
A check valve 55 and a throttle 54, which allow only pressure supply to the swing motor 45, are provided in parallel in each of a pair of oil supply / discharge passages (external piping) 56, 56 connecting the control valve 35 and the control valve 35. is there. That is, the pressure of the return oil from the swing motor 45 is greatly reduced and then returned to the control valve 35, so that the absolute value of the flow force at the second land R2 is greatly reduced to be smaller than the maximum pilot pressure, The maximum stroke state (state of FIG. 7) of the spool 35S can be revealed. Due to the presence of the external throttle 54, a slow return circuit that reduces shocks when the swivel base 2 is started and stopped is configured.

The internal throttle 35q of the control valve 35 functions to throttle even when the flow rate is comparatively small, but the external throttle 54 is required to have an effective throttle action in the maximum operation region. Therefore, when the vehicle is turned at a general turning speed, substantially only the internal diaphragm is operating, and it is possible to prevent the inconvenience that the intended speed cannot be obtained due to the excessive restriction of the diaphragms 35q and 54. ing. Although omitted intentionally in FIGS. 6 and 7, a spring mechanism for returning the spool 35S to the neutral position is actually present in one of the hydraulic chambers 35u.

[Another Embodiment] As shown in FIG. 9, even in the control valve having the structure including the second land R2 without the throttle passage portion rb, as shown in the figure, when the operation amount is small, the tank port 35t is Since the throttling action is generated at the opening portion with the second land, the pilot pressure and the flow force may antagonize each other in the vicinity thereof and the spool 35S may hunt. Therefore, even in this case, by providing the external diaphragm 54, the inconvenience can be eliminated.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

1] Side view of backhoe

FIG. 2 is a schematic overall view of a hydraulic circuit.

FIG. 3 is a partial hydraulic circuit diagram showing the principle of LS / S with AI / S.

FIG. 4 is a control block diagram.

FIG. 5 is a partial view of a swing motor related to a hydraulic circuit.

FIG. 6 is a sectional view showing a model structure of a turning control valve in a neutral state.

FIG. 7 is a model cross-sectional view showing a state of a turning control valve when pilot pressure is applied.

8 is an enlarged cross-sectional view of a second land portion of the control valve shown in FIG.

FIG. 9 is a cross-sectional view showing another structure of the second land.

[Explanation of symbols]

1 Excavation work equipment 2 swivel base 35 Spool type flow control valve 45 hydraulic actuator 54 Aperture 56 connection oil passage

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-52-89780 (JP, A) Special table S58-501283 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F15B 13/043 E02F 9/22

Claims (2)

(57) [Claims] 1. A hydraulic actuator for driving a load device.
Pilot operated spoo in the pressure oil supply circuit to (45)
This pilot-operated spool-type flow control valve (35) is provided with a le- type flow control valve (35).
To the spool (35S) of the hydraulic actuator (4
5) It acts on the oil returned from 5), and the load device becomes unstable or its own weight.
An internal throttle (35q) for suppressing movement is provided, and the hydraulic actuator (45) and the spool type flow rate are provided.
Of the oil passage (56) connected to the control valve (35), the hydraulic actuator
Pilot operated spool from the chute (45) side
In the return path to the mold flow control valve (35) side, the spool
The flow path is larger than the internal throttle (35q) provided in (35S).
A hydraulic circuit of a construction machine provided with an external throttle (54) that works on the good side . 2. The hydraulic circuit for a construction machine according to claim 1, wherein the hydraulic actuator (45) is a hydraulic motor for driving a swing base (2) having an excavation work device (1).