JPH0464375B2 - - 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. 5 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. 5, 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 7 flows through the oil passage 12,
Check valve 13, oil passages 14, 15, 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 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. 5, 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. 5 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: (a) providing a piston sliding chamber in which a piston with a throttle part is inserted in the spool of the arm switching valve; and (b) switching the arm cylinder extension operation. Sometimes, 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 piston in the spool of the arm switching valve is connected to the switching operation of the swing switching valve. In addition to blocking the drain oil passage on the rear spring chamber side, the piston with the throttle part can narrow the opening area of the notch hole on the front side of the piston sliding chamber of the arm spool by the spring force in the rear spring chamber of the piston. Configured.

Operation A: When the arm switching valve is in the neutral position, no hydraulic oil flows into the piston sliding chamber, so even if the swing switching is activated, the drain oil passage that opens to the spring chamber on the rear side of the piston in the arm spool is simply closed. It has nothing to do with turning operation.

(b) Even if the arm switching valve is switched, if the swing switching valve is in the neutral position, the drain oil passage of the swing switching valve that leads to the spring chamber on the rear side of the piston in the arm spool is open to the oil tank. A piston with a throttle inside the spool does not operate the throttle function.

C. When the rotation of the swing motor and the extension of the arm cylinder are operated simultaneously, the drain oil passage leading from the spring chamber on the rear side of the piston in the spool of the arm switching valve is blocked within the swing switching valve. Also, return oil from the piston rod side of the arm cylinder returns to the oil tank from the tank port via the arm switching valve, the front side of the piston sliding chamber in the arm spool, and its notch hole.

At the same time, some of the return oil that has flowed into the front side of the piston sliding chamber passes through the constriction part of the piston to the spring chamber on the rear side of the piston, so that the piston is moved forward by the spring force of the spring built into the rear side of the piston. , and narrow down the opening area of the notch hole on the front side of the piston sliding chamber.

(e) For this reason, the flow rate to the arm cylinder decreases, so that 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 operated 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 relief part in the section of the arm switching valve 6, 2
5 is a throttle part, 26 is a relief valve for the swing motor 3,
27 is a check valve for the swing motor 3, 28 is a boost check valve, 29 is a check valve, 30 is a prime mover for driving the hydraulic pump 7, 31 is a relief valve for the main oil passage, 32 is an oil tank, 34 is in the arm switching valve 6 The center bypass oil passage 46 is a drain oil passage provided in the swing switching valve 5.

FIG. 2 is a detailed sectional view of the arm switching valve 6 in FIG. 1, with the arm spool in a neutral position. In the figure, 33 is the body of the arm switching valve 6, and 34 is the body of the arm switching valve 6.
35 is an arm spool, 36 is a piston sliding chamber provided in the arm spool 35, and 37 and 38 are notch holes that communicate with the piston sliding chamber 36 from the outer periphery of the arm spool 35. , 39 is a spool head screwed onto the arm spool 35, 40 is a spring chamber, 41 is a notched hole communicating with the spring chamber 40 from the outer periphery of the arm spool 35, 42 is a piston with a constriction part 47 in the piston sliding chamber 36, 43 is a spring incorporated in the spring chamber 40 on the rear side of the piston 42; 44 is a rear plate attached to the body 33; 45 is a drain port provided on the rear plate 44; 46
is a drain oil passage provided in the swing switching valve 5. When the arm spool 35 is in the neutral position as shown in FIG. 2, no hydraulic oil is sent into the piston sliding chamber 36. At that time, the spring chamber 40 in the arm spool 35 is connected to the oil tank 3 through the drain oil passage 46 opened in the swing switching valve 5.
It communicates with 2.

FIG. 3 is a detailed cross-sectional view of the swing switching valve 5 and the arm switching valve 6 when the respective spools are switched in the direction of the arrow. In the figure, 48 is a drain introduction port of the swing switching valve 5, 49 is a swing spool,
Reference numeral 50 indicates a drain oil passage provided in the swing spool 49, 51 indicates a tank port that communicates with the drain oil passage 50 when the swing spool 49 is in the neutral position, and 52 indicates a drain port 45 of the arm switching valve 6 and the swing switching valve 5.
A is a port of the arm switching valve 6 that communicates with the drain introduction port 48 of the arm cylinder 4, B is a port that communicates with the piston rod side oil chamber of the arm cylinder 4,
53 is a return port for return oil of the arm switching valve 6.

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 rotation motor rotates three times and the arm cylinder 4 extends at the same time, the passage of the drain oil passage 50 in the rotation spool 49 of the rotation switching valve 5 to the tank port 51 is blocked. Also, return oil from the piston rod side oil chamber of the arm cylinder 4 passes through port B of the arm switching valve 6, the notch hole 37 of the arm spool 35, the front side of the piston sliding chamber 36, the notch hole 38, and the return port 53. tank 3
Return to 2. At the same time, a part of the return oil that has flowed into the front side of the piston sliding chamber 36 passes through the constriction part 47 of the piston 42 to the spring chamber 40 on the rear side of the piston 42, so that the piston 42 is moved forward by the spring force of the spring 43. The opening area of the notch hole 38 on the front side of the piston sliding chamber 36 is narrowed down. Therefore, the flow rate to the arm cylinder 4 decreases, so that the pressure oil discharged from the hydraulic pump 7 is transferred to the swing switching valve 5.
A large amount of the power is supplied to the swing motor 3 through the above, and the swing force of the swing 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 54 and the arm switching valve 55 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. The operating functions of the swing switching valve 54 and the arm switching valve 55 are the same as those of the swing switching valve 5 and the arm switching valve 6 in FIG. 1 described above.

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 with a throttle part is inserted is provided in the arm spool of the arm switching valve, and the arm cylinder can be extended during simultaneous swing and arm operation. In this case, the swing spool in the swing switching valve is configured to block the drain oil passage communicating with the spring chamber of the arm spool in the arm switching valve. To this end, a piston with a restrictor in the arm spool narrows the return oil path from the arm cylinder, reducing the flow rate to the arm cylinder, increasing the flow rate to the swing motor, and increasing its swinging force. Conventional technology uses pilot secondary pressure from a remote control valve to narrow the return oil path from the arm cylinder, so some models of hydraulic excavators that do not use the remote control method may require switching to the conventional technology. It was not possible to adopt a turning priority system using valves. However, in the present invention, when the swing switching valve is switched, the drain oil passage leading to the spring chamber in the arm spool is shut off, and the piston with a throttle part in the arm spool reduces the flow rate to the arm cylinder, thereby reducing the flow rate to the swing motor. I was able to increase it. 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 drawings]

FIG. 1 is a hydraulic circuit diagram having a switching valve according to the present invention;
Fig. 2 is a detailed cross-sectional view of the arm switching valve, Fig. 3 is a detailed cross-sectional view of the swing and arm switching valve, Fig. 4 is a hydraulic circuit diagram of another embodiment of the present invention, and Fig. 5 is a conventional switching valve. FIG. 3...Swivel motor, 4...Arm cylinder,
5, 5', 54...Swivel switching valve, 6, 6', 55...
...Arm switching valve, 35...Arm spool, 36
... Piston sliding chamber, 37, 38, 41 ... Notch hole, 40 ... Spring chamber, 42 ... Piston, 45
...Drain port, 46...Drain oil path section, 47
...Aperture part, 49...Swivel spool.

Claims (1)

[Claims] 1. In a switching valve in the hydraulic circuit of a hydraulic shovel that switches the pressure oil discharged from a hydraulic pump to control the operation of various hydraulic actuators, a piston sliding chamber in which a piston with a throttle part is inserted is provided in the spool of the arm switching valve, and the arm When the cylinder extension operation is switched, the piston rod side of the arm cylinder is communicated with the return oil passage through the front side of the piston sliding chamber and its notch hole, and the spool of the arm switching valve is connected to the return oil passage in conjunction with the switching operation of the swing switching valve. In addition to blocking the drain oil passage on the side of the spring chamber on the rear side of the piston, the piston with the throttle part is configured to be able to narrow the opening area of the notch hole on the front side of the piston sliding chamber of the spool by the spring force in the spring chamber on the rear side of the piston. A switching valve for hydraulic excavators characterized by: