JPH03244721A - Hydraulic circuit of hydraulic shovel - Google Patents

Abstract

PURPOSE:To cause a hydraulic shovel to travel at speed lower than the normal speed by dividing pressure oil of a pump into equal halves using a traveling motor when solenoid switching valves are switched and only travelling of the shovel in right and left directions is controlled simultaneously. CONSTITUTION:When a solenoid switching valve 52 is switched from its normal position 52a to a position 52b hydraulic lines 54, 55 for signals are communicated with respective portions of a pilot pump 31 and hydraulic lines 32e, 53 for signals are communicated with respective portions of the pump 31 via the throttle 56 of the valve 52. When an operator switches right and left travelling switching valves 11, 12 auxiliary switching valves 21, 22 block respective hydraulic lines 32a, 32b for signals and pressure is generated in a hydraulic line 32d for signals by the throttle 56 of the valve 52. At the same time a rectilinear travelling valve 19 is switched to a position 19b and equal pressure is generated in signal lines 54, 55 via the position 52b and switching valves 50, 51 are switched to respective positions 50b, 51b. Further a help from the valve 11 to the pump 1 is blocked and the pump 2 drives the valves 11, 12 in parallel and causes a hydraulic shovel to travel at half the normal speed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a hydraulic circuit for a hydraulic excavator.

(Prior art) Hydraulic excavators are generally equipped with attachments consisting of a boom, an arm, a packet, etc. in addition to the revolving body and the traveling body, and each of these includes a swing motor, a left/right travel motor, a boom cylinder, an arm cylinder, a packet cylinder, etc. is driven by a hydraulic actuator. These hydraulic actuators are controlled individually or in combination by directional control valves.

The conventional and common hydraulic drive system divides these directional valves into two groups, each group is connected to a separate hydraulic pump, and within each group, the directional valves are connected in parallel to the hydraulic pump. Was. An example of this conventional hydraulic circuit is shown in FIG.

In FIG. 2, 1 and 2 are hydraulic pumps. A left travel motor 3, a swing motor 5, and an arm cylinder 6 form a first group with respect to the hydraulic pump 1. Further, a right traveling motor 4°, a boom cylinder 7, and a bucket cylinder 8 form a second group with respect to the hydraulic pump 2. As directional control valves that control the operation of each actuator, for the pump 1, a left travel switching valve kl, a boom 2-speed switching valve 13,
A swing switching valve L4 and an arm switching valve 15 are each connected in parallel, and a right travel switching valve 12, a boom switching valve 18, a packet switching valve 17, and a standby switching valve 16 are each connected in parallel to the pump 2. .

Reference numeral 19 denotes a straight travel valve installed upstream of the switching valve ↓I, and is provided on the neutral flow path 34 of the discharge oil line of the pump 1 and on the most upstream side of the parallel flow path 37 of the discharge oil line of the pump 2. Each of the directional switching valves 11 to 8 is an auxiliary switching valve 21 that shuts off the signal hydraulic line in conjunction with switching of the main switching valve.
28.

Next, the pilot pressure oil generated by the pilot pump 3 is guided to both ends of the directional control valves 11 to 18 as appropriate through the operating pilot valves 29, 30, etc. (only traveling is shown in the figure) by lever operation by the operator. , switch the directional control valve and operate each actuator.

Furthermore, this pilot pressure oil is used for signal purposes. That is, the signal hydraulic line 32a connects to the auxiliary switching valve 2↓, the signal compensation line 32b connects to the auxiliary switching valve 22, and the signal hydraulic line 32c connects to the auxiliary switching valve 23゜24.25, 26.
．． 27 and 28 in this order to communicate with the tank. The signal hydraulic line 32d is branched from the hydraulic line 32c and guided to the port of the aforementioned straight travel valve. Note that the pressure oil generated by the pilot pump 31 is connected to signal hydraulic lines 32a and 32b.

Although 32c is connected to the tank, the aperture 3
3 and guided to the aforementioned pilot valves 29 and 30, etc., making it possible to operate them.

The inlet port of the left travel switching valve 11 is connected to the parallel flow path 35 of the hydraulic pump 1 via a throttle valve 39 with a check valve that supplies pressure oil only to the inlet port 38 side. The inlet ports of the boom two-speed switching valve 3 and the boom switching valve I8 are connected by a conduit 40, allowing the two pumps to merge when the boom is raised.

Furthermore, this circuit has a throttle 4 to prevent a decrease in swing acceleration force when the arm switching valve 15 and the swing switching valve 14 are operated simultaneously.
1. Hydraulic pumps l and 2 have their neutral flow paths 3
Pump control valves 42 and 4 are located downstream of 4 and 36.
3, and has regulators 45 and 46 that maintain the discharge amount of the pump 1.2 at the minimum position when the upstream directional control valves are in a neutral state, that is, when they are not doing any work. ing. Pumps 2 and 3 each have relief valves 47, 48, 49 in their circuits for setting their discharge pressures.

The feature of the hydraulic circuit having the above-mentioned structure is to ensure straight travel when the vehicle is traveling and other actuators are operated simultaneously, and its operation will be explained as follows.

(↓) When only travel is operated; left travel switching valve 11 only, or right travel switching valve 12 only,
Alternatively, if the left and right switching valves are operated at the same time, the signal hydraulic lines 32a and 32b are cut off because the auxiliary switching valves 21 and 22 are in the off position, but since no other actuator is operated, the signal hydraulic line 32c is It remains connected to the tank. Therefore, no pressure oil is generated in the signal hydraulic line 32d, and the straight travel valve 19 is not switched. As a result, the left travel motor 3 absorbs the flow rate of the pump 1, and the right travel motor 4 absorbs the flow rate of the pump 2, and are driven independently.

(2) When only the 7 actuators other than travel are operated; When any one or more of the switching valves L3 to ↓8 other than travel are operated, the signal hydraulic line 3 is operated in the same way as above.
2c is shut off by one of the auxiliary switching valves, but since the signal hydraulic lines 32a and 32b are connected to the tank, no pressure oil is generated in the signal hydraulic line 32d, and the straight-travel valve 9 is not switched. do not have. As a result, actuators other than those for driving also absorb the flow rate on the pump and 2 as they are.

(3) If the other 7 actuators are operated while the left and right travel is being operated simultaneously; the signal hydraulic lines 32a and 32b are each shut off by the auxiliary switching valves 21.22 linked to the left and right travel switching valves 11.12, and the signal Since the hydraulic pressure line 32c is shut off by an auxiliary switching valve linked to the switching valve of another actuator, pressure oil is generated in the signal compensation line 32d, and the straight travel valve 9 is switched to position 19b.

As a result, the pressure oil of the pump 2 connects the left and right travel motors 3 and 4 in parallel via the travel switching valve 1.1.12, and the pump 1 opens and operates other actuators in parallel.

This means that even if other operations such as raising the boom or turning are performed while the vehicle is traveling straight ahead by left-right travel, the pressure oil on the pump is preferentially supplied to the left-right travel motor.

In addition, the straightness of travel is guaranteed by the wave train supply. In this case, since the two motors are opened and operated simultaneously by the pump 2, the traveling speed is half of the traveling speed when only traveling is operated, that is, 0.5 speed.

Next, to explain the throttle valve with check valve 39, when other actuators are frequently operated in an ON-FF manner while traveling straight, the traveling speed will change to 1 speed due to intermittent switching of the straight traveling valve L9. - It switches rapidly between 0 and 5 speeds, causing a shock to the main body operation. Therefore, by appropriately setting the opening degree of this throttle valve with check valve 39, parts of the travel circuit where the drive pressure is higher than that of the travel circuit, such as when raising the rubber or raising the arm, are supplied to some of the travel circuits, thereby preventing sudden changes in travel speed. However, when a turning operation is performed while driving, the turning starting pressure generally rises to the relief pressure of the circuit, and during turning acceleration, most of it is discarded from the relief valve to the tank, but this throttle valve 39 Since a portion of the fuel can be supplied to the traveling circuit, it is possible to improve the traveling speed.

In addition, in FIG. 1, from the throttle valve 39 with check valve to the left travel switching valve 11
However, since the pump 2 operates the travel motors 3 and 4 in parallel, straight travel is maintained due to the synchronization of the travel motors.

As described above, in the conventional circuit shown in Fig. 2, even if other actuators are operated while traveling straight, pressure oil from pump 2 is absorbed preferentially, so straight traveling is maintained, and furthermore, even if other actuators are operated while traveling straight, straight traveling is maintained. Although this system provides an efficient hydraulic circuit that supplies a portion of the excess oil to the travel circuit even when the system operates simultaneously, increasing speed, it has the following drawbacks.

That is, 1) If operations with a small load such as boom lowering and arm lowering are performed at the same time while traveling straight, the straight traveling valve switches and pump 1 opens the boom lowering, arm lowering, etc., but the lower pressure than the traveling circuit Therefore, pressure oil cannot be supplied from the throttle valve 39 to the traveling side. As a result, until then pumps 1 and 2
The main body, which had been running with two pumps, suddenly started running with only pump 2, causing a sudden deceleration. If this process is repeated frequently, the load may shake and spill, making it extremely difficult to maneuver.

2) In addition, in this circuit, when only driving is operated, it is in so-called 1st speed, and in order to achieve slow speed driving for precision work, it is necessary to lower the engine speed with a separately installed throttle lever, which is cumbersome to operate. It is.

(Problem to be solved by the invention) Hydraulic excavators are used at all kinds of construction sites due to their versatility, but their mobility has improved in recent years through high-speed running, making them useful for moving around sites, transporting materials, etc. are doing. However, work while moving, such as transporting materials or pouring ready-mixed concrete, sometimes requires running at very low speeds.
Furthermore, during complex operations including traveling, changes in travel speed when other actuators start or stop operation may cause load shaking and spillage, which is undesirable when precision work is to be performed.

An object of the present invention is to provide a travel-independent hydraulic circuit that realizes low-speed travel lower than the normal speed in the travel operation of a hydraulic excavator, and furthermore, the travel speed does not change even if other actuators are activated during slow-speed travel. It is something.

(Means for solving the problem) One travel switching valve and a non-travel actuator are connected in parallel to the first pump, and the other travel switching valve and a non-travel actuator are connected to the second pump in parallel. The actuators are connected in parallel, and a first position is placed on the neutral flow path immediately before the one travel switching valve, and a first position that normally forms the neutral flow path of the first pump and a parallel flow path of the second pump, and is a second position that constitutes a flow path that supplies the pressure oil of the first pump in parallel to the actuator switching valve other than the running switching valve of the second pump, and supplies the pressure oil of the second pump to one of the running switching valves. In a hydraulic circuit in which a straight travel valve is arranged, the parallel flow path of the first pump and the inlet port of one of the travel direction switching valves are normally communicated by a throttle valve with a check valve, and the passage is closed during switching. A switching valve is installed in which the parallel flow path of the first pump and the most downstream part of the neutral flow path are normally closed and communicated during switching. The signal hydraulic line was constructed so that the two switching valves would switch simultaneously when the vehicle was operated simultaneously.

(Example) An explanation will be given based on FIG. 1. However, the same components as those in the prior art are designated by the same reference numerals as those in the known circuit of FIG. 2, and a description thereof will be omitted.

A two-position switching valve that communicates the inlet port 38 of the left travel switching valve 11 with the parallel flow path 35 of the pump 1 through a throttle valve 50a with a check valve in normal times, and has a position 50b that is closed when signal pressure is received. Connect via 50.

The most downstream of the parallel flow path 35 and the most downstream of the neutral flow path 34 of the pump 1 are normally closed and communicated when a signal pressure is received.
It is connected via the position switching valve 51.

An electromagnetic switching valve 52 is installed in the pilot signal hydraulic line 32c immediately before the boom 2nd speed auxiliary switching valve 23.

The respective ports of the switching valves 50, 51, and 52 are connected to each other through a signal appropriate pressure line 53 between 52c and 51c, a signal hydraulic line 54 between 52d and 51d, and a signal hydraulic line 55 between 52d and 50c.

(Function) When the electromagnetic switching valve 52 is in the normal position 52a in FIG. 1, the oil discharged from the pilot pump 31 is communicated with the tank 44 via the signal hydraulic lines 32c to 32e and the auxiliary switching valves 23 to 28. Therefore, the signal hydraulic line 53
, 54.55, no pressure oil is generated, so the switching valve 50.5
No. 1 does not switch, and there is no functional difference from the conventional circuit.

Next, when the electromagnetic switching valve 52 is switched to the 52b position.

The signal hydraulic lines 54 and 55 communicate with the pilot pump, and the signal hydraulic lines 32e and 53 communicate with the electromagnetic switching valve 5.
4 which communicates with the pilot pump via a throttle 56 in 2b.
Ru. - The force signal hydraulic lines 32a, 32b conventionally lead to the tank via auxiliary switching valves 21,22.

Now, with the electromagnetic switching valve 52 switched to 52b, when the operator switches the left and right travel switching valves 11 and 12 at the same time, the interlocked auxiliary switching valves 21 and 22 block the signal hydraulic lines 32a and 32b, and the electromagnetic switching valve A pressure is generated in the signal hydraulic line 32d by the throttle 56 in the valve 52b.

At the same time, the straight travel valve 19 is switched to 19b, and the same pressure is generated in the signal path 54,55 via the electromagnetic switching valve 52b, switching the switching valves 50,51 to sob and stb, respectively.

As a result, the switching valve 50 of the pump l is closed and the switching valve 51 is closed.
opens, the support to the traveling switching valve 11 is cut off, and the flow returns to the tank from the most downstream side of the parallel flow path.Since the pump 2 drives the left and right traveling switching valves 11 and 12 in parallel, the speed is reduced to half the normal traveling speed. In other words, 0.5 speed driving can be achieved.

Next, if you operate an actuator other than traveling while traveling straight at 0.5 speed, at least one of the auxiliary switching valves 23 to 28 will shut off the signal hydraulic line 32e.
Pressure is also generated in the signal hydraulic line 53, which acts on the other port 51c of the switching valve 51. The switching valve 51 is balanced because it receives the same pressure at both end ports, but is held at a position 51a that closes the neutral flow path by a spring force.

In other words, if actuators other than the drive actuator are operated simultaneously while the vehicle is moving straight at 0.5 speed, the pressure oil from the pump 2 is supplied to the left and right drive motors 3 and 4 in parallel, realizing slow speed travel and
For the pressure oil of pump 1, the switching valves 50 and 51 are both in the closed position 5.
By being held at 0b and 5La, it is supplied only to actuators other than those operated for travel. This ensures independence between travel and other actuators.

(Effects) According to the circuit of the present invention, by switching the electromagnetic switching valve 52 to the 52b position using a separately provided switch or the like, when only left and right travel is operated simultaneously, the pressure oil of the pump 2 is transferred to the travel motor 3. , 4, it is possible to achieve half the running speed (0 and 5 speeds) of the conventional circuit. Furthermore, even if other actuators are operated during the slow running, the pump cannot supply pressure oil to the running circuit, so independence of running is guaranteed.

In other words, even when operating the attachment while traveling with a hydraulic excavator, for example, when removing earth and sand from a bucket or pouring ready-mixed concrete, the traveling speed remains unchanged and smooth, precise work is possible. Of course, the solenoid switching valve 52 is in the normal position 5.
If the setting is returned to 2a, the running speed amplifier can be used as before.

[Brief explanation of drawings]

FIG. 1 shows a compensator circuit according to the present invention. FIG. 2 shows a known hydraulic circuit. In the figure; Top, 2 Hydraulic pump 3 4 Right travel motor 5 6 Arm cylinder 7 8 Bucket cylinder 11 12 Right travel switching valve 13 14 Swivel switching valve 15 16 Reserve switching valve 17 18 Boom switching valve 19 21.22, 23, 24 ,25,26,27.2829
．． 30 Pilot valve 31 Pilot pump 32a, 32b, 32c, 32d, 32e Signal hydraulic line 33 Restriction 34 Medium g, flow junction 35 Parallel flow path 36 Neutral flow path 37
Parallel flow path 38 Population port 39 Throttle valve
40 Pipeline 4Y Calibration 42.43 Pump control valve 44 Tank 45.46 Regulation 47
．． 48.49 Relief valve 50 2 position switching valve Left travel motor Swivel motor Boom cylinder Left travel switching valve Boom 2 speed switching valve Arm switching valve Bucket switching valve Travel straight valve Auxiliary switching valve 50a Throttle valve 50b (closed) position 5
12 position switching valve 52 Solenoid switching valve 53.54.5
5 Compensation line for signal 56 More than throttle

Claims (1)

[Claims] One travel switching valve and a non-travel actuator are connected in parallel to the first pump, and the other travel switching valve and a non-travel actuator are connected in parallel to the second pump. On the neutral flow path immediately before the travel switching valve, there is a first position that normally forms the neutral flow path of the first pump and a parallel flow path of the second pump, and a position that connects the pressure oil of the first pump to the second position during switching. In a hydraulic circuit in which a traveling straight valve having a second position that supplies pressure oil of a second pump in parallel to actuator switching valves other than the traveling switching valve of the pump and forming a flow path for supplying pressure oil of a second pump to one traveling switching valve is disposed, The parallel flow path of the first pump and the inlet port of one of the travel direction switching valves are normally connected by a throttle valve with a check valve, and a switching valve is installed that has a position to close the passage during switching, and If a switching valve is installed that has a position where the parallel flow path of the first pump and the most downstream part of the neutral flow path are normally closed and communicated during switching, and the left and right running is operated simultaneously, the two A hydraulic circuit for a hydraulic excavator, characterized in that a signal hydraulic line is configured such that switching valves are switched at the same time.