JPH0464376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an arm switching valve and a swing switching valve for a hydraulic excavator.

2. Description of the Related Art Work attachments (not shown) such as a boom, an arm, and a bucket are attached to the front part of the upper revolving body of a hydraulic excavator to perform various excavation operations. Among them, there are swing pressing excavations in which the side surface of the bucket is pressed against the inclined wall surface to excavate vertically on the wall surface, and arm diagonal pull grading, both of which involve simultaneous operation of the swing and arm. Therefore, in the turning force excavation, if the turning force is small, the bucket escapes to the side and the inclined wall surface cannot be excavated vertically. For this reason, when operating the swing and arm simultaneously on a hydraulic excavator, a swing priority system is adopted. FIG. 7 is a hydraulic circuit diagram of a prior art turning priority system. In the figure, 1 is a remote control valve for swing operation (hereinafter referred to as a remote control valve), 2 is a remote control valve for arm operation, and 3 is a remote control valve for arm operation.
is a swing motor, 4 is an arm cylinder, 5' is a swing switching valve, 6' is an arm switching valve, 7 is a hydraulic pump,
Reference numeral 8 designates a shuttle valve provided at an intermediate portion of an oil passage communicating the pilot pressure receiving portions on the left and right sides of the swing switching valve 5', and 9 designates a pilot pump.

In the hydraulic circuit shown in FIG. 7, the operating functions for simultaneous rotation and arm operation will be described. For example, the swivel remote control valve 1 is operated to the A position, and the arm remote control valve 2 is simultaneously operated to the B position. Then, the pilot pressure from the swing remote control valve 1 acts on the right pilot pressure receiving part of the swing switching valve 5' through the pilot oil passage 10, switching the swing switching valve 5' to position C, and the pressure from the arm remote control valve 2 The pilot pressure acts on the right pilot pressure receiving portion of the arm switching valve 6' through the pilot oil passage 11, and switches the arm switching valve 6' to the 2 position. At the same time, the pressure oil discharged from the hydraulic pump is transferred to oil passage 12, check valve 13, oil passages 14 and 15, and check valve 1.
6. Swing motor 3 via position C of swing switching valve 5'
The rotation motor 3 is rotated.
On the other hand, since the arm cylinder 4 and the swing motor 3 are connected in parallel, the pressure oil discharged from the hydraulic pump 7 flows through the check valve 13, the oil passage 17, the arm switching valve 6', and the oil passage 18. The oil is then sent to the head side of the arm cylinder 4, and the arm cylinder 4 is extended. A part of the pilot pressure oil acting on the right pilot pressure receiving part of the swing switching valve 5' passes through the shuttle valve 8 and the oil passage 19 to the variable restrictor 20 in the two-position section of the arm switching valve 6'. also works. Therefore, the return oil circuit from the arm cylinder 4-piston rod side is throttled by the variable throttle section 21 in the two-position section of the arm switching valve 6'. Therefore, the pressure on the head side of the arm cylinder 4 increases, but the amount of oil sent decreases, so that the pressure oil discharged from the hydraulic pump 7 is transferred to the check valve 13, the oil passages 14, 15, the check valve 16, and the swing switching valve 5'. A large amount of the rotation force is supplied to the rotation motor 3 through the position C, and the rotation force increases.

Problems to be Solved by the Invention When a hydraulic excavator simultaneously operates its swing and arm, the prior art employs the above-mentioned swing priority system to increase the swing force. Therefore, in FIG. 7, the pilot secondary pressure of the swing remote control valve 1 is used as the pilot pressure signal acting on the variable restrictor 20 in the two-position section of the arm switching valve 6'.

However, some models of hydraulic excavators, such as small hydraulic excavators, do not employ a remote control valve operation type but are equipped with a so-called direct pull operation type switching valve using a direct lever or link. Therefore, the pilot secondary pressure from the remote control valve as in the prior art shown in FIG. 7 cannot be used. Therefore, it is an object of the present invention to improve the above-mentioned points and provide an arm and a swing switching valve that can be used in a direct pull operation type and a remote control valve operation type.

Means for Solving the Problems The means of the present invention taken to solve the above problems are as follows: (a) A piston sliding chamber in which a piston is inserted into the spool of the arm switching valve is provided, and (b) When the arm cylinder extension operation is switched, the piston slides. The piston rod side of the arm cylinder and the return oil passage are communicated through the front side of the sliding chamber and its notch hole, and the swing operating pressure in the swing switching valve is derived by the switching operation of the swing spool, thereby switching the arm. It acts on the oil chamber on the rear side of the piston in the arm spool of the valve, and (2) the piston in the arm spool is configured to be able to narrow down the opening area of the notch hole on the front side of the piston sliding chamber.

Operation B: When the arm switching valve is in the neutral position, no hydraulic oil flows into the piston sliding chamber, so even if the swing switch is activated, the swing operation pilot pressure only acts on the oil chamber on the rear side of the piston in the arm spool, and the swing operation is performed. is unrelated.

(b) Even if the arm switching valve is switched, if the swing switching valve is in the neutral position, the swing operation pilot pressure will not act on the piston in the arm spool, so the piston in the arm spool will not operate the throttling function. Therefore, the amount of oil returned from the piston rod side of the arm cylinder is not throttled and reduced.

C. When rotating the swing motor and extending the arm cylinder at the same time, the swing operation pilot pressure acts on the rear chamber of the piston in the arm spool, so the piston in the piston sliding chamber moves forward and narrows the opening area of the notch hole in the arm spool. .

D. On the other hand, since the return oil from the arm cylinder passes through the narrowed notch hole, the flow rate to the arm cylinder decreases. Therefore, a large amount of the pressure oil discharged from the hydraulic pump is supplied to the swing motor via the swing switching valve, and the swinging force of the swing motor increases.

Examples Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a hydraulic circuit diagram having a swing and arm switching valve of the present invention, 3 is a swing motor, 4 is an arm cylinder, 5 is a direct pull operation swing switching valve,
6 is a direct pull operation type arm switching valve, 7 is a hydraulic pump, 22 is a check valve for the swing switching valve 5, 23 is a check valve for the arm switching valve 6, 24 is a piston throttle part in the section of the arm switching valve 6, 25 is a center bypass oil passage of the swing switching valve 5, 26 is a swing pilot pressure oil passage, 27 is a pilot oil passage that communicates the swing switching valve 5 and the arm switching valve 6, 28 is a relief valve for the swing motor 3, and 29 is a swing pilot pressure oil passage. A check valve for the swing motor 3, 30 a boost check valve, 31 a check valve, 32 a prime mover for driving the hydraulic pump 7,
33 is a main oil passage relief valve, and 34 is an oil tank.

FIG. 2 is a detailed cross-sectional view when the swing switching valve 5 is in the neutral position and the arm switching valve 6 is switched to arm cylinder extension operation. In the figure, 3
5 is a swing spool in the swing switching valve 5, 36 is an arm spool in the arm switching valve 6, 37 is a swing pilot pressure deriving port of the swing switching valve 5, 38 is a swing pilot pressure introduction port in the arm switching valve 6, 39
40 is a bridge oil passage in the arm switching valve 6, 40 is a piston sliding chamber provided in the arm spool 36, and 41 is a bridge oil passage in the arm switching valve 6;
42 and 43 are notched holes communicating from the outer circumference of the arm spool 36 to the front side of the piston sliding chamber 40, 44 is an oil chamber on the rear side of the piston, and 45 is a piston slidably inserted into the piston sliding chamber 40. A notched hole that communicates from the outer circumference of the arm spool 36 to the piston rear side oil chamber 44, 46 is a return port of the arm switching valve 6, and A and B are connected to the swing motor 3 from the swing switching valve 5.
Ports for connecting oil passages to, C and D are arm switching valves 6
These are ports for connecting oil passages to the head side and piston rod side of the arm cylinder 4, respectively.

Therefore, as shown in FIG.
When the hydraulic pump 7 moves in the direction of the arrow, the pressure oil discharged from the hydraulic pump 7 is sent to the head side oil chamber of the arm cylinder 4 via the bridge oil passage 39 and port C.
On the other hand, the return oil from the piston rod side of the arm cylinder 4 is sent to port D of the arm switching valve 6, to the notch hole 42 of the arm spool 36, and to the piston sliding chamber 4.
Returns to the oil tank 34 via the notch hole 43 and return port 46 on the front side. Note that, since the rotation operating pressure does not act on the oil chamber 44 on the rear side of the piston in the arm spool 36, the return oil from the arm cylinder 4 is not subjected to a throttling action by the piston 41.

Next, based on FIGS. 1 and 3, the operating function of the switching valve of the present invention during simultaneous swing and arm operation will be described. When the swing motor rotates three times and the arm cylinder 4 is extended simultaneously, the pressure oil discharged from the hydraulic pump 7 opens the check valve 22 in the swing switching valve 5, passes through the bridge oil passage 47 and port B, and then flows into the swing motor 3. Operate the rotation. At the same time, a part of the operating pressure oil of the swing motor 3 is supplied to the swing pilot pressure oil passage 26, the swing pilot pressure derivation port 37, the pilot oil passage 27, the swing pilot pressure introduction port 38 of the arm switching valve 6, and the notch hole of the arm spool 36. 45, the piston 4 via the piston rear oil chamber 44
It acts on 2. Then, the piston 41 moves to the front side, and the notch hole 4 on the front side of the piston sliding chamber 40
Narrow down the opening area in step 3. Therefore, the flow rate of the arm cylinder 4 decreases, so that the pressure oil discharged from the hydraulic pump 7 passes through the swing switching valve 5 to the swing motor 3.
As a result, the turning force of the turning motor 3 increases.

Next, FIG. 4 shows another embodiment of the present invention, in which remote control valves 1 and 2 are arranged for operating the swing motor 3 and arm cylinder 4, respectively. For this purpose, in the figure, the swing switching valve 48 and the arm switching valve 49 have pilot pressure receiving portions on the left and right sides, and are switched by the pilot pressure from the remote control valves 1 and 2, respectively. Therefore, the operating functions of the swing switching valve 48 and the arm switching valve 49 are the same as those of the swing switching valve 5 and the arm switching valve 6 in FIG. 1 described above.

FIG. 5 also shows another embodiment of the present invention, in which a spring is inserted into the arm spool of the arm switching valve. In Figure 5, 50
51 is an arm switching valve, 51 is an arm spool, 52 is a piston slidably inserted into the arm spool 51, 53 is a return oil passage oil chamber in the arm spool 51, and 54 and 55 are return valves from the outer periphery of the arm spool 51. Notched hole 56 leading to oil passage oil chamber 53
5 is a piston front spring chamber; 57 is a drain oil passage leading from the piston front spring chamber 56 to an external oil tank;
Reference numeral 8 indicates a spring incorporated in the spring chamber 56 on the front side of the piston, 59 indicates an oil chamber on the rear side of the piston, and 60 indicates an oil chamber 59 on the rear side of the piston from the outer periphery of the arm spool 51.
It is a notch hole that leads to. In addition, 34 is an oil tank,
38 is a swing pilot pressure introduction port, 39 is a bridge oil passage in the arm switching valve, and 46 is a return oil passage for return oil from the arm cylinder 4.

Therefore, the hydraulic circuit diagram in which the arm switching valve 50 and the swing switching valve 5 having the above-mentioned structure are arranged is shown in the sixth figure.
This is shown in the figure. Therefore, the operating function of the arm switching valve 50 will be described based on FIGS. 5 and 6. When the swing switching valve 5 is switched to the H position and the arm switching valve 50 is switched to the H position and operated simultaneously, the pressure oil discharged from the hydraulic pump 7 passes through the check valve 22 and the swing switching valve 5 at the H position, and rotates the swing motor 3. At the same time, the arm cylinder 4 is extended through the check valve 23 and the arm switching valve 50 to their respective positions. At the same time, a part of the operating pressure oil of the swing motor 3 is supplied to the swing pilot pressure derivation port 37 of the swing switching valve 5 H position section, the pilot oil passage 27, the swing pilot pressure introduction port 38 of the arm switch valve 50 H position section, and the arm spool. 5
It acts on the piston rear oil chamber 59 through the notch hole 60 of No. 1, and moves the piston 52 forward. At this time, the spring 58 in the spring chamber 56 on the front side of the piston
is compressed, and a part of the oil in the spring chamber 56 is sent to the external oil tank 34 via a drain oil passage 57. Therefore, as the piston 52 moves forward, the shoulder of the piston 52 returns and narrows the opening area of the notch hole 55 of the oil passage chamber 53, so the flow rate of the arm cylinder 4 decreases and the flow rate to the swing motor 3 increases. , the turning force of the turning motor 3 increases. Note that when the swing switching valve 5 is returned to the neutral position, the swing pilot pressure does not act on the piston 52 in the arm spool 51, so the piston 52 moves rearward due to the spring force of the spring 58, and the notch hole 5
5 is fully opened, and the return oil of the arm cylinder 4 is no longer subjected to the throttling action.

Effects of the Invention As mentioned above, in the switching valve for a hydraulic excavator of the present invention, a piston sliding chamber in which a piston is inserted is provided in the arm spool of the arm switching valve, and when the arm cylinder is extended, the piston rod does not return from the piston rod side. The oil passes through the oil chamber on the front side of the piston sliding chamber in the arm spool and its notch hole, and returns to the return oil path. On the other hand, when the swing switching valve is switched, the swing operation pilot pressure is applied to the inside of the arm spool and the oil chamber on the rear side of the piston. For this purpose, if the swing and arm cylinder extension operations are operated simultaneously, the piston in the arm spool narrows the return oil path from the arm cylinder to reduce the flow rate and increase the flow rate to the swing motor, reducing the swing force of the hydraulic excavator. increase In the conventional technology, secondary pressure from a remote control valve was used to narrow down the return oil path from the arm cylinder, so for hydraulic excavators that do not use a remote control method, the conventional technology requires a switching valve to rotate the hydraulic excavator. It was not possible to adopt a priority system. However, in the present invention, when the swing switching valve is switched, the swing pilot pressure for operating the swing motor moves the piston in the arm spool, thereby narrowing the return oil path from the arm cylinder. Therefore, the switching valve of the present invention enables a swing priority system when the swing and arm are simultaneously operated, regardless of whether the hydraulic excavator is a direct pull operation type or a remote control valve operation type, and allows a swing priority system to be applied to many types of hydraulic excavators. The functionality of the system can be expanded.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram having a switching valve according to the present invention;
Figures 2 and 3 are detailed cross-sectional views of the swing and arm switching valve, Figure 4 is a hydraulic circuit diagram of another embodiment of the present invention, and Figure 5 is a detailed cross-sectional view of the arm switching valve of another embodiment of the present invention. , FIG. 6 is a hydraulic circuit diagram of another embodiment of the present invention, and FIG. 7 is a hydraulic circuit diagram having a conventional switching valve. 3...Swivel motor, 4...Arm cylinder,
5, 5', 48...Swivel switching valve, 6, 6'...Arm switching valve, 49,50...Arm switching valve, 36,
51...Arm spool, 38...Swivel pilot pressure introduction port, 41, 52...Piston, 4
2, 43... Notched hole, 45, 54... Notched hole, 55, 60... Notched hole.

Claims (1)

[Claims] 1. In a switching valve in the hydraulic circuit of a hydraulic excavator that controls the operation of various hydraulic actuators by switching the pressure oil discharged from a hydraulic pump, a piston sliding chamber with a piston inserted into the arm spool of the arm switching valve is provided, and the arm cylinder is extended. At the time of operation switching, the piston rod side of the arm cylinder and the return oil passage are communicated through the front side of the piston sliding chamber and its notch hole, and the swing operating pressure in the swing switching valve is derived by the switching operation of the swing spool. A hydraulic excavator, characterized in that the piston in the arm spool of the arm switching valve acts on a rear side oil chamber of a piston in the arm spool, and is configured such that the piston in the arm spool can narrow down the opening area of a notch hole on the front side of the piston sliding chamber. Switching valve for use.