JPH04319130A - Hydraulic circuit for hydraulic shovel - Google Patents

Abstract

PURPOSE:To smoothen straight running of hydraulic shovel during the operation of switching valve by letting the pilot pressure pass through a sub-valve via a side valve which operates in connection with a switching valve and is set so that it is switched to the oil passage shutoff position when the switching valve is in the neutral position and to the oil passage opening position when the switching valve is in the switching position. CONSTITUTION:A side valve 46, which operates in connection with a switching valve 22', is installed to the switching valve 22' which is activated by the direct push/pull operation. The side valve 46 is set so that it is switched to the oil passage shutoff position when the switching valve 22' is in the neutral position and to the oil passage opening position when the switching valve 22' is in the switching position. When the switching valve 22' is operated during of hydraulic shovel, the pilot pressure from a pilot pump 28 is sent to a sub-valve 30L via the side valve 46. Next, the hydraulic shovel is run by operating running valves 17L, 17R, and the pilot switching valve is operated without the operation switching valve 22', so that the pilot pressure fed from hydraulic remote control valves 4L, 4R is applied to the pilot pressure receiving section 24 of a straight running valve 23.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention applies to various hydraulic actuators.
The present invention relates to a hydraulic circuit for straight travel of a hydraulic excavator, which is equipped with a pilot switching valve and a direct push/pull operation type switching valve.

0002

2. Description of the Related Art FIG. 2 is a side view of a hydraulic excavator. In the figure, 1 is the lower traveling body of the hydraulic excavator, 2L and 2R are the left and right traveling motors, 3 is the upper rotating body, 4L and 4
R is a left and right hydraulic remote control valve, 5 is a swing motor, 6 is a swing bracket attached to the front part of the upper rotating body 3, 7 is a swing cylinder, 8 is a work attachment, 9
is the boom of work attachment 8, 10 is the arm, 11
1 is a bucket, 12 is a boom cylinder, 13 is an arm cylinder, 14 is a bucket cylinder, 15 is a dozer device, 1
6 is a dozer cylinder of the dozer device 15.

FIG. 3 is a conventional hydraulic circuit diagram of a hydraulic excavator. In the figure, 17L and 17R are travel switching valves that control the left and right travel motors 2L and 2R, respectively, and 18, -, 21 are other actuators (for convenience of explanation,
(Other actuators are not shown in FIG. 3) are pilot switching valves for control, 22 is a direct push/pull operating switching valve that controls, for example, a swing cylinder, a dozer cylinder, etc., 23 is a straight travel valve, and 24 is a pilot switching valve for control. Straight travel valve 23
, 25 and 26 are the first and second pumps, 27 is an oil tank, 28 is a pilot pump,
29 is a shuttle valve that selects the high pressure of the pilot pressure (in this case, the pilot secondary pressure) derived from the hydraulic remote control valves 4L and 4R; 30L and 30R are the travel switching valves 17;
These are sub-valves of L and 17R (hereinafter referred to as travel valves 17L and 17R). Also, the symbols E-I, Ro-Ro, Har-
C, . . . , . . . , , , , , , , , , , , , , , , , , , , , ,, , ,, ,, ,, ,, ,, ,,, ,,, ,,, ,,,, ,,,, 1,,,,,,,,,,,,,,,,,,,,,,,1,1,1,11 or, respectively, respectively, indicate the connections of the pilot pipes that connect the hydraulic remote control valves 4L, 4R and the pilot switching valves 18, -, 21.

Next, the conventional hydraulic circuit is shown in FIGS. 2 and 3.
Let's talk about. In the conventional hydraulic circuit, there are pilot switching valves 18, -, 21 that are operated by operating hydraulic remote control valves 4L and 4R as switching valves that control various hydraulic actuators installed in a hydraulic excavator, and pilot switching valves 18, 21, which are actuated by operating hydraulic remote control valves 4L and 4R, and direct push/pull operation type switching valves. A switching valve 22 is provided, and the various hydraulic actuators are divided into two groups A and B, each with a first pump 25,
The left and right travel valves 17L and 17R are arranged in the front rows of groups A and B, respectively, and the straight travel valve is located on the discharge side of the first pump 25 and the second pump 26. 23, and the left and right travel valves 1
7L and 17R are provided with sub-valves 30L and 30R, respectively, which switch and operate in conjunction with the traveling valves 17L and 17R. Of the two sub-valves 30L and 30R, the pilot pressure passes through the upstream sub-valve 30L and the downstream sub-valve 30R, and is applied to the pilot pressure receiving portion 24 of the straight travel valve 23.

[0005] When the left and right travel valves 17L and 17R are operated, the hydraulic excavator travels. In this case, travel valve 17L
In conjunction with the switching operation of 17R and 17R, both sub-valves 30L and 30R are switched from the shutoff oil passage position to the open oil passage position. When the pilot switching valve for controlling other actuators (any one of pilot switching valves 18, 21) is operated in this running state, the pilot pressure derived from the hydraulic remote control valves 4L and 4R is changed to the shuttle valve 29. , conduit 3
1. Via the open oil path position of the sub-valve 30L, the pipe line 32, the open oil path position of the sub-valve 30R, and the pipe lines 33 and 34,
It acts on the pilot pressure receiving section 24. The straight travel valve 23 is switched from the R position to the N position. Pressure oil from the first pump 25 passes through a pipe line 35, and one pipe line 36 and a traveling valve 1
7L to the travel motor 2L, and the other branched at a pipe 35 to a pipe 37, the position of the straight travel valve 23, and the pipe 38.
, is supplied to the travel motor 2R via the travel valve 17R. Pressure oil from the second pump 26 is supplied to other operated actuators through pipes 39 and 40, the null position of the straight travel valve 23, pipes 41, 42, or 43, and check valves 44 or 45. Ru. As described above, the travel valves 17L and 17
When R and the pilot switching valve for controlling other actuators are operated simultaneously, the hydraulic excavator can travel straight.

[0006]

Problems to be solved by the present invention will be explained with reference to a conventional hydraulic circuit shown in FIG. 3. As shown in FIG. 2, the hydraulic excavator is equipped with a pair of hydraulic remote control valves 4L and 4R in front of the driver's seat. The operating levers of the hydraulic remote control valves 4L and 4R can be operated in the front, rear, left, and cross directions, respectively, and can be used with four types of hydraulic actuators (boom cylinder, bucket cylinder, arm cylinder, etc.).
Various pilot switching valves 18, . However, in addition to the four types of hydraulic actuators mentioned above, hydraulic excavators also have work attachments (
It is provided with a swing cylinder (a dozer cylinder for a dozer device is also provided, but the explanation thereof will be omitted) for performing the swing operation of reference numeral 8) shown in FIG. 2. The operation of this swing cylinder is controlled by the hydraulic remote control valves 4L and 4.
Since this cannot be done with R, a direct push/pull operation type (so-called manual operation type) switching valve 22 is arranged as a switching valve for controlling the swing cylinder. For this reason, if only the swing cylinder control switching valve 22 is operated while the hydraulic excavator is running by operating the running switching valves 17L and 17R, no pilot pressure will act on the pilot pressure receiving part 24 of the straight running valve 23. Therefore, the straight travel valve 23 does not switch to the straight travel oil path position NU. Since the straight travel valve 23 remains in the second pump discharge oil path position,
Pressure oil from the first pump 25 is supplied to the left travel motor 2L, and pressure oil from the second pump 26 is supplied to the right travel motor 2R and the swing cylinder. Left travel motor 2L
Since the flow rate of pressure oil supplied to the right travel motor 2R was smaller than the flow rate of pressure oil supplied to the right travel motor 2R, the hydraulic excavator did not move straight, which was a problem. The present invention aims to solve the above problems.

[0007]

[Means for Solving the Problems] The present invention provides a switching valve that operates by direct push/pull operation, and a side valve that switches in conjunction with the switching valve, so that when the switching valve is in a neutral position, the side valve is closed. When the switching valve is in the switching position, the side valve is set to switch to the open oil passage position, and when the hydraulic excavator operates the push-pull operation type switching valve directly while the hydraulic excavator is running, the pilot pump The pilot pressure is communicated to the upstream sub-valve via the side valve.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a hydraulic circuit diagram of the present invention. In the figure, the same reference numerals are given to the same components as in the prior art. Reference numeral 22' denotes a direct push/pull operation type switching valve, 46 a side valve that switches in conjunction with the switching valve 22', and 47 a shuttle valve for pilot pressure selection. Next, the configuration of the hydraulic circuit of the present invention will be described with reference to FIG. The switching valve 22' that operates by direct push/pull operation includes a side valve 46 that switches in conjunction with the switching valve 22'.
and set so that when the switching valve 22' is in the neutral position, the side valve 46 is in the cutoff oil passage position, and when the switching valve 22' is in the switching position, the side valve 46 is switched to the open oil passage position, When the hydraulic excavator is running and the direct push/pull operation type switching valve 22' is operated, the pilot pressure from the pilot pump 28 is applied to the side valve 46.
It was configured to communicate with the upstream sub-valve 30L via the upstream sub-valve 30L.

When the hydraulic excavator is running by operating the left and right traveling valves 17L and 17R, the pilot switching valve (18 , ~, 21), the hydraulic remote control valve 4L
, 4R is the pilot pressure derived from the shuttle valve 29
, pipe line 31a, shuttle valve 47, pipe line 31b, opening oil line position of sub-valve 30L, pipe line 32, sub-valve 30R
The pilot pressure is applied to the pilot pressure receiving part 24 through the open oil passage position and the pipes 33 and 34. Therefore, the straight travel valve 23 is switched from the R position to the N position, so that in this case, the hydraulic excavator travels straight as in the prior art.

Next, while the hydraulic excavator is traveling by operating the left and right traveling valves 17L and 17R, the pilot switching valves 18, -, 21 are not operated, but the switching valve 22 of the push/pull operation type is directly operated. ' to operate. In this case, no pilot pressure is derived from the hydraulic remote control valves 4L, 4R. However, in conjunction with the operation of the switching valve 22', the side valve 46 is switched from the shutoff oil passage position to the open oil passage position. The pilot pressure (in this case, the pilot primary pressure) from the pilot pump 28 is transmitted to the pipe line 48, the constriction part 49, and the pipe line 5.
0, open oil line position of side valve 46, pipe line 51, shuttle valve 47, pipe line 31b, open oil line position of sub-valve 30L, pipe line 32, open oil line position of sub-valve 30R, via pipe lines 33, 34 , acts on the pilot pressure receiving section 24. Therefore, since the straight travel valve 23 is switched from the R position to the N position, the hydraulic excavator can operate the hydraulic actuator (for example, a swing cylinder, a dozer cylinder, etc.) operated by the switching valve 22' while traveling straight. can.

[0011]

Effects of the Invention As explained above, in the present invention, a switching valve operated by direct push/pull operation disposed on a hydraulic excavator is provided with a side valve that switches in conjunction with the switching valve, so that the switching valve is in the neutral state. When the switching valve is in the switching position, the side valve is set to the cutoff oil passage position, and when the switching valve is in the switching position, the side valve is switched to the open oil passage position. As a result, when the direct push/pull operation type switching valve is operated while the hydraulic excavator is running, pilot pressure from the pilot pump acts on the pilot pressure receiving portion of the straight-travel valve via the side valve. Since the straight travel valve is switched to the straight travel oil path position, the hydraulic excavator can operate the hydraulic actuator operated by the switching valve while traveling straight ahead. Therefore, in a hydraulic excavator equipped with the hydraulic circuit of the present invention, even if the travel and pilot switching valves or the travel and direct push/pull operation type switching valves are operated simultaneously, the hydraulic excavator will not run diagonally or meander, resulting in improved running performance. and improve safety.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit of the present invention.

FIG. 2 is a side view of the hydraulic excavator.

FIG. 3 is a hydraulic circuit diagram of the prior art.

[Explanation of symbols]

2L, 2R Travel motors 4L, 4R Hydraulic remote control valves 17L, 17R Travel switching valves 18, -, 21 Pilot switching valves 22, 22' (directly push/pull operated) switching valve 23
Straight travel valve 25, 26 First, second pump 28 Pilot pump 30L, 30R Sub valve 46 Side valve 47, 29 Shuttle valve

Claims (1)

[Claims] Claim 1: A plurality of pilot switching valves that are operated by operating a hydraulic remote control valve as switching valves for controlling various hydraulic actuators installed in a hydraulic excavator, and a plurality of pilot switching valves that are operated by direct push/pull operation. The various hydraulic actuators mentioned above are divided into two groups A and B, each driven by a first and second pump, and the left and right travel switching valves are divided into two groups A and B. and B are placed in the front row, respectively, and a straight travel valve is provided on the discharge side of the first and second pumps, and the left and right travel switching valves are switched in conjunction with the travel switching valves. Each sub-valve is provided, and when the hydraulic remote control valve is operated while the hydraulic excavator is running, the pilot pressure derived from the hydraulic remote control valve passes from the upstream sub-valve to the downstream sub-valve among the two sub-valves, and is used as the pilot pressure of the straight-travel valve. In a hydraulic circuit configured to act on a pressure receiving pressure section, a switching valve operated by direct push/pull operation is provided with a side valve that switches in conjunction with the switching valve, and when the switching valve is in a neutral position, the side valve is closed. When the switching valve is in the switching position, the side valve is set to switch to the open oil passage position, and when the hydraulic excavator operates the push-pull operation type switching valve directly while the hydraulic excavator is running, the pilot pump A hydraulic circuit for a hydraulic excavator, characterized in that the pilot pressure is communicated to the upstream sub-valve via the side valve.