JPS5876619A - Hydraulic circuit for hydraulic shovel - Google Patents

Abstract

PURPOSE:To perform a precise multiplication of a bucket speed, by a method wherein, in a subject circuit comprising direction switching valves for multiplying a bucket, in case an arm cylinder is excessively increased in load, a hydraulic oil in a hydraulic pump in a different system is fed to a bucket cylinder through said valve. CONSTITUTION:A hydraulic circuit for hydraulic shovel is constituted such that first and second direction switching groups 10 and 12 are attached to first and second main hydraulic pumps 9 and 11, and the groups 10 and 12 have direction switching valves 15-18, 19-22, respectively, for a bucket, an arm, a boom, and running. In which case, a pump port P of said valve 32 is connected to a pump circuit 39 through a piping 40 so that the pump port P is positioned in parallel to a common pump port 38 of the group 12. A logic valve 41, closing at an operating time of the bucket, is connected to a downstreammost part of a center bypass of the group 12, and the output side thereof is connected to a tank circuit 34.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the hydraulic circuit of a hydraulic field or packhoe type hydraulic belt.

Figure 1 shows the appearance of an example of a conventional hydraulic loading cylinder.
Normally, the arm control lever is left open and the arm control lever is operated as necessary. That is,
Always move arm cylinder 1 in the direction of rod extension,
Without moving the arm 2 forward, move the back cylinder 3 in the vertical direction as necessary to scoop up the packet 4 (tilt direction) and roll it (b) to place the load on the packet 4. Put in. #p In Figure 1, 5 is a boom cylinder, 6 is a boom, 7 is a rotating body, and 8Fi traveling body. FIG. 2 shows an example of a hydraulic oil path of a conventional hydraulic loading cylinder. The first main hydraulic pump is provided with a monoblock type four-barrel directional control valve group 10, and the second main hydraulic pump 11 is provided with a monoblock type four-barrel directional control valve group 10. A directional valve group 12 is provided.

The first and second turns 713 and 14 are provided separately. The directional switching valve glue 110 of Peng 1 includes the packet directional switching valve 15, the first arm directional switching valve 1, the boom directional switching valve 17 of the irises 1, and the right travel directional switching valve 1.
8 are connected in parallel. Second directional valve group 12
Specifically, the packet opening/closing directional switching valve 19, the second arm directional switching valve 20, the boom directional switching valve 21 of the second arm, and the left running directional switching valve 22 are connected in parallel. As an actuator, arm cylinder 2 is directly necessary for digging operation.
3 and the packet cylinder 24 are shown, and the boom cylinder, packet opening/closing cylinder, right travel motor, and left travel motor are omitted. Furthermore, the one-swing directional switching valve and the swing motor are also omitted.

2! i, 21i are relief valves, 27.21 are filters,
29 is an oil cooler, and 30 is a tank.

As shown in FIG. 1, the arm cylinder 2sK has a two-stage arm circuit in which pressure oil from the two main hydraulic pumps 9. It is a one-stage circuit in which only pressure oil is supplied from the two main hydraulic pumps 9. In such a hydraulic circuit, normally when the arm operating lever is turned on and off, the arm cylinder 23's dynamic force in the rod extension direction becomes too large, causing the relief valves 25 and 26 to operate in relief. Since it is no longer possible to excavate with 23 alone, the packet operation lever is operated to move the packet cylinder 24 in the rod extension direction KWIJ and rotate the packet 4 in the scooping direction. Therefore, the pressure oil discharged from the first main hydraulic pump 3 is transferred to the packet cylinder 24 by the bucket Y directional control valve 15.
On the other hand, the pressure m discharged from the second main hydraulic pump 11 is wasted into the tank 30 due to the relief operation of the relief valve 26, resulting in a loss of energy. . In addition, when the packet cylinder 24 is manufactured independently, only the pressure oil from the first main hydraulic pump S is used, and the pressure oil from the second main hydraulic pressure t::/p 11 is not used. This means that only the station is making effective use of it, and the packet operation speed is also slow.

Next, excluding the above-mentioned drawbacks, as shown in FIG.
Carry-over boat 3 to second directional valve group 12
1, and connect the pump mate of the carryover type packet expansion directional switching valve 32. Nokukerato speed increasing directional switching valve 32
The center bypass boat is connected to tank circuit 3 by piping 33.
4, and the work boat is connected to the bottom side oil chamber of the packet cylinder 24 via piping 35. Therefore, when the packet cylinder 24 operates independently in the rod extension direction, the pressure oil from the two main hydraulic pumps 9 and 11 is supplied to the bottom of the packet cylinder 24 @oil gK, so that the packet is scooped up in the direction The operating speed is twice that of the case shown in FIG.

However, in FIG. 3, the packet expansion directional switching valve 32 is connected in tandem to the directional switching valve group 182, so if the arm operation lever (-) is turned on and then shifted, The center bypass 36 of the directional control valve group 12 is opened, pressure oil does not flow to the packet expansion directional control valve 32, and even if the packet chiller valve 3T is operated, the packet cylinder 24 is not supplied with pressure oil. No 1
Pressure oil is supplied only from the main hydraulic pump■. Therefore, the load applied to the arm cylinder 23K increases.
If the relief valve 26 operates in relief mode, the KS side 2
All the pressure oil of the main hydraulic pump 11 is wasted and discharged into the tank 30, and no useful work is done.

The purpose of the present invention is to solve the above-mentioned problems and provide a hydraulic circuit for a hydraulic excavator that can increase packet speed at low cost and prevent relief loss when the load on the arm cylinder is too large. It is to provide.

To achieve this objective, the present invention comprises a pump boat of a directional control valve for increasing speed (a bucket provided outside the first and second directional control groups) and a directional control valve for the second arm. Common pump port of the second directional valve group) K
A valve means is provided which is connected in parallel and connects the lowermost part of the INN of the center bypass of the second directional valve group so that the most downstream part always communicates with the tank and closes the most downstream part when the baffle F is operated. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on illustrated embodiments.

FIG. 4 shows one embodiment of the present invention. #! Portions similar to those in FIG. 3 are designated by the same reference numerals. The L-coupled packet expansion directional switching valve 32 is the first and llI2 directional switching valve group 10.
．． 12, and its final pump (P) is connected to the & pump circuit 311 via a pipe 40 so as to be in parallel with the common pump mate 38 of the directional control valve group 12 of the 2nd valve. The input side of a logic valve 41 is connected to the lowest fi portion of the center bypass 36 of the second directional valve group 12, that is, the middle overboard 31, and its output is connected to the tank circuit 34. - Pressure 11 of sick valve 41
42 is connected to the tank circuit 34 via a switching valve 43.

The logic valve 41 includes a valve body 45 having a communication hole 44 and a return spring 46 . The switching valve 43 receives a pilot pressure signal from the four-way valve 31 for pact tilting as a switching pressure.

When the bucket F is operated alone, when the packet tilt bi-stomer cut valve 3T is operated, a bi-lodge pressure signal is input to the switching valve 43, which is switched to the closed position. Since this is K,
The pressure plan 42 of the logic valve 41 is from the tank 30
The Fr.n10 sink valve 41 serves as a closed shaft. Then, the pressure oil from the second main hydraulic pump 11 is supplied to the bottom side of the packet cylinder 24 by the packet speed increasing directional switching valve 32, and merges with the pressure oil from the first main hydraulic pump 9. The operation speed in the pick-up direction of the packet becomes the speed of two pumps, which can increase the digging speed.If the pilot valve 31 for the banatchi route is not operated, the switching valve 43 is in the open position. Since the pressure is negative, the pressure -42 of the tank valve 41 reaches the tank 30, and if none of the directional control valves 19 to 22 are operating, the valve body 45
A pressure difference is applied to the logic valve 41, and the logic valve 41 becomes open. The center bypass 36 therefore communicates with the tank 30 and the directional valve group 12 of the nest 2 operates normally.

When the arm and the packet are operated, the switching valve 43 is switched to the closed position by operating the bucket tilt bi-four valve 31, and the logic valve 41 is placed in the closed state. Then, the pressure of the second main hydraulic pump 11 is divided into the second arm directional switching valve 20 and the bucket expansion directional switching valve 32. Therefore, if the load on the arm cylinder 23 becomes too large, the packet cylinder 2 with lower load pressure
Most of the pressure oil from the second main hydraulic pump 11 is supplied to the pump 4, and the relief valve 26 does not operate, thereby preventing relief loss.

In the embodiment of FIG. 4, the logic valve 41 corresponds to the valve means of the present invention. However, this valve means is a logic valve Kli
! Other types of valves can be used. tx
The means for controlling valve means such as the % gastric sick valve 41 include not only the switching valve 43 but also other hydraulic means, electrical means,
Mechanical means 1 Pneumatic means can be used.

According to the present invention, the pump boat of the directional control valve for packet expansion is added to the above-mentioned 15.
Since K is connected in parallel, if the load on the 1° arm cylinder becomes too large, pressure oil from the hydraulic pump in stripe 2 can be supplied to the packet cylinder Km via the packet expansion directional control valve, and the relief #Q can be It can be prevented. Also,
Since the packet expansion directional control valve is provided outside the 1st and 2nd directional control valve groups, there is no need to change the type of the directional control valve group to one with one more control valve group, which reduces costs. I can do it. In history, a valve means was provided at the most downstream part of the center bypass of the directional control valve group in Saba 2, which normally communicates the most downstream part with the tank and closes the most downstream part when the packet is operated, so that it is possible to operate the packet alone. Sometimes 1#! The pressure oil of the two hydraulic pumps can be supplied to the directional switching valve for increasing the number of packets, and the individual operation speed of the packet can be increased to the speed of the two pumps.

[Brief explanation of the drawing]

Figure 1 is a side view of an example of a conventional hydraulic loading excavator, Figure 2 is a hydraulic circuit diagram of an example of a conventional hydraulic loading excavator, and Figure 3 is a virtual hydraulic seeding shovel that can be considered from the level of conventional technology. Hydraulic circuit diagram of an example of Pell,
FIG. 4 is a hydraulic circuit diagram of one embodiment of the present invention. 9...First main hydraulic pump, 10...1
0 directional control valve group, 11...fg2 main hydraulic pump, 12...2nd directional control valve group, 15...packet directional control valve, 16.・
...First arm directional control valve, 20...
Second arm directional control valve, 23...Arm cylinder, 24...Bucket cylinder, 25.2
6... Relief valve, 30... Tank,
31... Carryover boat, 32...
・Directional switching valve for packet expansion, 36... Center bypass, 38... Common pump boat, 41...
...Logic valve, 43...Switching valve, P.
・・・・・・Pompbo F agent patent attorney Buken Tsugube (#t or 1 person)

Claims (1)

[Claims] In the first directional control valve group for the hydraulic pump of 1, the first arm directional control valve and the packet directional control valve are connected in parallel, and the second directional control valve for the second hydraulic pump is connected in parallel.
In the hydraulic circuit of the hydraulic cylinder equipped with the directional valve group for the second arm, the directional valve group 1 and the 2nd
The pump port of the packet expansion directional valve provided outside the directional valve group is connected in parallel to the common pump &-) of the second directional valve group, and A hydraulic circuit for a hydraulic pump, characterized in that the most downstream part of the bypass is provided with a valve means that normally communicates the most downstream part with a tank and closes the most downstream part when a packet is operated.