JPS60133128A - Hydraulic circuit of hydraulic excavator - Google Patents

Abstract

PURPOSE:To enable to perform other control as straight running is held, by a method wherein the running control valve of the control valve group of a first hydraulic pump is communicated, downstream from the bucket control valve of a second hydraulic pump, with the oil pressure of the second hydraulic pump through a separate bypass line. CONSTITUTION:In a 2-pump hydraulic system, a boom control valve 14B and an arm control valve 11A are connected in parallel to a first hydraulic pump 1, and a running control valve 10 is connected in series downstream from an arm control valve 11A. Meanwhile, a bucket control valve 13 is connected, in series to a running control valve 12, to a second hydraulic pump 2. Bypass lines 44 and 47, through which the second hydraulic pump 2, a bucket control valve 13, and the upper stream of the running control valve 10 are intercommunicated, are installed. This enables other actuator to perform independent control as straight running ability is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit for a hydraulic excavator such as a hydraulic excavator equipped with a plurality of actuators.

Hydraulic excavators, such as hydraulic excavators, are generally equipped with attachments consisting of a revolving body, a running body, and a boom, arm, and packet. driven by.

These actuators are controlled individually or in combination by the directional control valve. FIG. 1 is a side view showing the overall configuration of a hydraulic excavator, and FIG. 2 is a plan view of FIG. 1. In these figures, reference numeral 101 denotes a revolving body, which is disposed above a traveling body 102 and rotates by driving a revolving motor 3 . Reference numeral 104 denotes a left truck, which is driven by the left traveling motor 4.

Reference numeral 106 denotes a right truck, which is driven by the right travel motor 6. 108 is a boom, 109 is an arm, and 110 is a packet, which constitute a working machine. 8 is a boom cylinder that operates the boom 108; 5 is arm 1;
09 is the arm cylinder that operates, 7 is the packet 110
It is a packet cylinder that operates.

Traditionally, the most 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. It is something to do. This method has a simple hydraulic circuit and has the advantage of being able to drive each actuator simultaneously to some extent, but on the other hand, when the actuators in the counting process perform multiple operations, the movement of each actuator is affected by each other's operating pressure, making control difficult. If this cannot be done accurately, and if there is an extreme difference between the operating pressures of multiple actuators that operate in combination depending on the load condition on the actuators, pressure oil will flow only to the actuator with the lower operating pressure. Therefore, a situation arises in which the operation of the other actuator stops.

As an example of a solution to this problem, a hydraulic circuit shown in FIG. 3 has been proposed. This hydraulic circuit basically consists of a hydraulic pump and a plurality of directional control valves connected in tandem. In FIG. 3, two hydraulic pumps 1.2 are provided, a swing motor 3, a left travel motor 4 and an arm cylinder 5 form one group for the hydraulic pump 1, and for the hydraulic pump 2, The right travel motor 6, the packet cylinder 7 and the boom cylinder 8 form another group. and directional valve 9゜10.1
1 are connected in tandem to the hydraulic pump 1 , and directional valves 12 , 13 , 14 are connected in tandem to the hydraulic bonder 2 . On-off valves 18 and 19 for opening and closing communication with the tank 17 are provided downstream of the directional valve group 15 comprising the directional valves 9 to 11 and downstream of the directional valve group 16 comprising the directional valves 12 to 14. Each is provided. Pilot valves 20 to 25 are pilot pressure signal circuit B-
4 sends pilot pressure signals to the directional control valves 9 to 14, respectively, to JIJ control the direction and flow rate of these pressure oils. The pilot valves 20 to 25 are commonly connected to a pilot pressure signal 26 which is a hydraulic pressure source. Between the two directional valve groups 15.16 there is a bypass circuit 27, 28.29.
A bypass circuit 80 is also provided between the hydraulic pump 1 and the directional control valve 11. Bypass circuit 27
A restriction valve 31 having a flow rate restriction position and an open position is provided in the bypass circuit 30, and a restriction valve 32 is provided in the bypass circuit 30.

Pilot pressure signal circuits m and n that send pilot pressure signals to the on-off valves 18 and 19 are connected to the selection valve 33 and the switching valve 34.

Here, a case where the actuators 3 to 8 are operated in a combined manner in the hydraulic circuit shown in FIG. 3 will be described.

(1) Swinging operation and traveling operation The directional control valve 9 is operated by the pilot pressure signal from the pilot valve 20 for swinging, and pressure oil from the hydraulic pump 1 is supplied to the swinging motor 3. Since the restriction valve 31 is switched to the open position by the pilot pressure signal from the pilot pressure signal circuit a or b, the directional switching valve 1o and the directional switching valve 12 are connected in parallel to the hydraulic bonder 2 by the bypass circuit 27.

Therefore, when the pilot valve 21 for left travel and the pilot valve 23 for left travel generate a pilot pressure signal, both the direction changeover valve 1o and the direction changeover de 12 operate, and the left travel motor 4 and the right travel motor 6 operate. Pressure oil from the hydraulic pump 2 is supplied to the. Thus, the turning morph 3 and the left and right travel motors 4 and 6 are driven independently.

(2) Swing operation and boom operation The directional control valve 9 supplies pressure oil from the hydraulic pump 1 to the swing motor 3 in response to a pilot pressure signal from the pilot valve 20 for swing. On the other hand, the directional control valve 14 supplies pressure oil from the hydraulic pump 2 to the boom cylinder 8 in response to a pilot pressure signal from the boom pilot valve 25 .

(3) Swing operation and arm operation Pressure oil from the hydraulic pump 1 is supplied to the swing motor 8 as described above by operating the swing pilot valve 2O. The switching valve 34 connects the pilot pressure signal circuit e or f for the arm to the pilot pressure signal circuit n in response to the pilot pressure signal of the pilot pressure signal circuit a or b for turning, so that the pilot pressure from the pilot valve 22 for the arm is reduced. The signal switches the on-off valve 19 to the closed position. Thereby, the directional switching valve 11 is connected to the hydraulic pump 2 via the switching valve group 16 by the bypass circuit 28, and the arm cylinder 5 is driven by pressure oil from the hydraulic pump 2.

As described above, the hydraulic circuit shown in FIG. 3 allows various combined operations, but problems arise when performing the following covering operations.

(a) Boom ios'f! while driving! : When attempting to dump, pressure oil from the hydraulic pump 1 is supplied only to the left travel motor 4, pressure oil from the hydraulic pump 2 is supplied only to the right travel motor 6, and no pressure oil is supplied to the boom cylinder 8. , therefore, the boom 108 cannot be moved.

(b) If you try to dump arm 1L79 while driving, since directional control valve 10 is switched υ,
The pressure oil supplied to the arm cylinder 5 is supplied through the throttle 32, and as a result, the arm 109 cannot be raised sufficiently.

(c) When attempting to escape from the wetland by clouding the arm 109 while traveling in a wetland, if the vehicle idles while traveling, pressure oil is not supplied to the arm cylinder, giving the arm 109 the force necessary for escape. I can't.

(d) When traveling with a load suspended from the tip of the packet 110, the packet 110
Even if an attempt is made to cloud 0, the packet cannot be moved because the directional control valve 12 has been switched. This is the same even when the excavator is not traveling with a load suspended as described above, and the hydraulic pressure of the hydraulic excavator allows other actuators to operate without any hindrance to straight forward travel even while the excavator is traveling. To provide the circuit.

To achieve this objective, the present invention comprises a first directional valve group connected to a first hydraulic pump and a second directional valve group connected to a second hydraulic pump, the first
The directional valve group consists of a boom directional valve, an arm directional valve, and a left (or right) travel directional valve, and the boom directional valve and arm directional valve are located at the center of the directional valve group. Connect in parallel on the upstream side of the bypass,
Connect the left (or right) travel direction switching valve to the downstream side,
Further, the second directional control valve group is composed of a right (or left) travel direction changeover valve and a packet direction changeover valve, and the right (or left) travel direction changeover valve is located upstream of the center bypass of the direction changeover valve group. and a packet directional control valve is connected to the downstream side thereof, and further includes a left hydraulic pump and a packet directional control valve, and a left hydraulic pump and a packet directional control valve belonging to the second hydraulic pump and the first directional control valve. (or right) A bypass pipe is provided between the travel direction switching valve.

Hereinafter, the present invention will be explained based on the illustrated embodiments.

FIG. 4 is a system diagram of a hydraulic circuit of a hydraulic excavator according to a first embodiment of the present invention.

In FIG. 4, the same parts as in FIG. 3 are given the same reference numerals, and their explanation will be omitted. IIA is the first arm directional control valve, II
B is a second arm directional switching valve, 14A is a first boom directional switching valve, and 14B is a second boom directional switching valve. 41 is a pipe line between the first hydraulic pump 1 and the boom directional control valve 14B of the confectionery 2; 42 is a pipe line between the second hydraulic pump 2 and the right travel direction control valve 12; 44 is a pipe line between the second hydraulic pump 2 and the right travel direction control valve 12 The first bypass line 45 connecting the second hydraulic pump 2 and the left travel direction switching valve 10 is a check valve interposed in the first bypass line. Reference numeral 47 denotes a second bypass line that is branched off from a portion of the first bypass line 44 after the check valve 45 and connects this branch point and the Barkerato circumferential switching valve 13 . Reference numerals 48 and 49 indicate a check valve and a throttle valve, respectively, which are interposed in the second bypass line 47. Note that 50 is a load check valve provided on the input boat side of each directional switching valve, and 51 and 52 are relief valves for circuit maintenance. 53 is the first hydraulic pump 1, the swing direction switching valve 9, and the first hydraulic pump 1
and the first arm directional control valve 11A, and this parallel circuit connects the second boom directional control valve 14B, the M-turn directional control valve 9, and the first arm directional control valve 11A.
The arm directional control valves 11A are connected in parallel.

Here, the operation of the hydraulic circuit of this embodiment when performing a compound operation will be explained.

(1) Swing operation and traveling operation Pressure oil is supplied to the swing motor 3 from the first hydraulic pump 1 via the swing direction switching valve 9. On the other hand, pressure oil is supplied to the right travel motor 6 from the first hydraulic pump 1 via the right travel direction switching valve 12.

Pressure oil is supplied to the left travel motor 4 from the first hydraulic pump 1 via the first bypass line 44 and the left travel directional switching valve 10 . Therefore, the turning operation and the traveling operation are performed independently as in the conventional example shown in FIG. 3, and the straightness of traveling is also maintained.

(2) Swing operation and boom operation Pressure oil is supplied to the swing motor 3 from the first hydraulic pump 1 via the swing direction switching valve 9, and the boom cylinder 8 is supplied with pressure oil from the first hydraulic pump 1 via the swing direction switching valve 9. Pressure oil is supplied from the first hydraulic pump 1 through the boom, and pressure oil from the second hydraulic pump 2 is supplied through the first boom directional control valve 14A. Such interaction between the turning motion and the boom motion is frequently performed in the operation of a hydraulic excavator. By the way, in a conventional hydraulic circuit in which the swing motor 3 and boom cylinder 8 are driven by separate hydraulic pumps 1 and 2 as shown in FIG. 3, when the swing motor 3 accelerates, excess pressure oil is IJ IJ-7 valve to IJ IJ
- Since the engine was turned off, it caused a loss of horsepower and was inefficient. That is,
Since the rotating body has a large inertia, when the rotating body accelerates, the operating pressure of the rotating motor 3 becomes higher than the opening pressure of the IJ-IJ-7 valve. However, in the hydraulic circuit of this embodiment, since the swing direction switching valve 9 and the second boom direction switching valve 14B are connected in parallel, the rise in the swing motor 3 operating pressure is due to the boom cylinder 8 operation. The excess pressure oil from the swing motor 3 is thereby supplied to the boom cylinder 8. Therefore, horsepower is effectively used for boom operation, and the boom can be raised sufficiently.

In addition, when independence of swing operation and boom operation is required, the first boom directional switching valve 14A and the second boom directional switching valve 14B may be connected to perform a two-stage operation. , the first boom directional control valve 14 is operated in the first stage.
Only A operates, and the first and second boom directional switching valves 14A are activated by the second stage operation.

If 14B are made to operate together, the swing operation and boom operation can be made completely independent by the first stage operation.

(3) Swing operation and arm operation Pressure oil from the hydraulic pump 1 at @1 is supplied to the swing motor 3 via the swing direction switching valve 9, and the arm cylinder 5 is
First arm directional control valve 11A'! The pressure oil of the first hydraulic pump 1 is supplied through i=, and the pressure oil of the second hydraulic pump is supplied through the second arm directional switching valve 11B.

(4) Traveling operation and boom operation The left traveling motor 4 is connected to a first bypass line 44 and a left traveling directional control valve 10, and a second hydraulic pump 2 is connected to the left traveling motor 4.
Pressure oil of the second hydraulic pump 2 is supplied to the right travel motor 6 via the right travel direction switching valve 12. Further, pressure oil from the first hydraulic pump 1 is supplied to the boom cylinder 8 via the second arm directional switching valve 14B'z. Therefore, in this embodiment, traveling h1
The key money operation for the movement and boom operation is possible, and the travel operation and arm operation can be made independent, allowing straight-line travel. (5) Travel operation and arm operation The hydraulic pump 2 of the seat ↓ 2 is
Pressure oil from the second hydraulic pump 2 is supplied to the right travel motor 6 via the right travel direction switching valve 12 . Further, pressure oil from a first hydraulic pump is supplied to the arm cylinder 5 via the first arm directional switching valve 11A'. Therefore, since the traveling motion and the arm motion are independent, arm 109 can be raised sufficiently without hindering straight traveling, and arm 109 can have sufficient force even if it slips while traveling when escaping from a wetland. This will not cause any inconvenience in escaping from the wetland.

(6) Traveling operation and packet operation Pressure oil from the first hydraulic pump 1 is supplied to the left traveling motor 4 via the left traveling direction switching valve 10, and the right traveling motor 6
Pressure oil from the second hydraulic pump 2 is supplied to the right-hand travel direction switching valve 12 . Further, pressure oil from the second hydraulic pump 2 is supplied to the packet cylinder 7 via the first bypass line 44, a second bypass line 47 branching from the first bypass line 44, and the packet directional switching valve 13. , the first bypass line 44, the second bypass line 47, and the packet direction switching valve 13, which branch from before the input port of the left travel directional switching valve 100.
The pressure oil of the hydraulic pump 1 is combined with the pressure oil of the second hydraulic pump 2 and supplied. Such a branching of the pressure oil to the packet cylinder 7 is carried out without any problem since the driving pressure of the packet cylinder is normally lower than the driving pressure of the travel motor.

In this way, it is possible to perform packet operations while the vehicle is running. Further, in this case, the drive pressure of the left and right travel motors 4, 6 is approximately equal to the pressure of the first bypass line 44, so that the straightness of travel is not lost. By the way, if the driving pressure of the packet cylinder 8 is low, the amount of pressure oil sent to the packet cylinder 8 will increase in the circuit as described above, and therefore the amount of pressure oil supplied to the travel motors 4 and 6 will decrease. There may be cases where the vehicle becomes abnormally slow. Squeeze! 11149 is provided to prevent this, and the flow rate of the pressure oil flowing into the packet cylinder 7 is restricted by the restrictor 49. In addition, aperture 9
49 is not necessarily necessary.

As described above, in this embodiment, the first directional valve group is connected to the second boom directional valve, the swing directional valve, and the first directional valve, which are connected in parallel on the upstream side of the center bypass.
The second directional valve group consists of a directional control valve for the arm and a directional control valve for left-hand travel connected to the downstream side, and a directional control valve for right-hand travel connected to the most upstream side of the center bypass. , consists of a first boom directional control valve and a packet directional control valve connected in parallel on the downstream side, and an arm directional control valve connected most downstream, which is connected to a second directional control valve group. A first bypass line is provided between the second hydraulic pump and the left travel directional control valve, and a second bypass line is provided between the packet directional control valve and the first bypass line. Because of the provision of the Straightness can be maintained. Furthermore, it is also possible to reduce energy loss during a combined operation of a swing operation and a boom operation.

Fig. MrJ5 is a system diagram of a hydraulic circuit of a hydraulic excavator according to a second embodiment of the present invention.

The difference between this embodiment and the first embodiment is that the first boom directional control valve 14A is connected from the middle of the first bypass line 44.
The third bypass line is provided between the second embodiment and the other parts are the same as the first embodiment. That is, 54 is a third bypass line that branches off from the first bypass line 44 and is provided between the input boat of the first boom directional control valve 14A. Reference numerals 55 and 56 indicate a check valve and a throttle valve, respectively, which are interposed in the third bypass line 54.

In the first embodiment, when it was necessary to make the swing operation and the boom operation independent, the first and second boom directional control valves 14A and 14B were configured to be connected by two projections in one operation. In the first embodiment,
In the case of a combination of travel operation and boom operation, the boot cylinder 8 cannot be completely driven even if the first stage operation of activating the first boom directional control valve 14A is performed. That is, since the right travel directional switching valve 12 is switched, the first boom directional switching valve 14A and the second hydraulic pump 2 are connected to each other, and the second boom directional switching valve 14B is switched. This is because it has not been switched.

However, in this embodiment, the third bypass line 5
4 is provided, so when performing traveling operation and boom operation,
When the boom lever is operated to perform the first stage operation, the first boom directional control valve 14A is switched, and the pressure oil of the first and second hydraulic pumps 1.2 is transferred to the first bypass line 44, f.
It is supplied to the boom cylinder 8 via the M3 bypass line 54 and the first boom directional switching valve 14A to perform boom operation.

In this case, if the driving pressure of the boom cylinder 8 is low, the first SH
2 f (b I + from bombs 1 and 2) The amount of pressurized oil sent to the cylinder 8 increases, and the running may become abnormally slow. The throttle 56 is provided to prevent this, and the flow of pressure oil flowing into the boom cylinder 8 is restricted by the throttle 56.

Note that the aperture 56id is not necessarily essential.

In this way, in this embodiment, in addition to the configuration of the first embodiment, a third bypass line is provided between the first bypass line and the button and the one boom directional control valve. 1st
In addition to achieving the same effect as the embodiment described above, in order to ensure independence when performing a combined operation of swing operation and boom operation, a configuration in which the boom directional control valve is operated in two stages can also be used to control the travel operation. Even when performing a combined operation of boom operation and boom operation, this can be performed without any problem.

FIG. 6 is a system diagram of a hydraulic circuit of a hydraulic excavator according to a third embodiment of the present invention.

This embodiment differs from the second embodiment shown in FIG. 5 in that a fourth bypass line is connected to the first bypass line 44, and the other configurations are the same as the second embodiment. be. That is, 58 is a fourth bypass line that connects the first hydraulic pump 1 and the first bypass line 44. Reference numerals 59 and 60 indicate a check valve and a crest interposed in the fourth bypass line 58.

In the case of the second embodiment described above, when the boom is operated during traveling operation, the pressure oil that has not been supplied to the left and right traveling motors 4.6 is reduced by approximately half.

As a result, the traveling speed may suddenly drop to a low level, giving a shock to the operator.

However, in this embodiment, the fourth bypass line 5
8, part of the pressure oil of the first hydraulic pump 1 is supplied to the travel motor 4 through the first bypass line 44, and the throttle angle 0 of the fourth bypass line 58 is appropriately set. By doing so, it is possible to reduce shock and maintain independence of boom operation. The same thing can be said when performing a combined operation of a turning operation and a traveling operation, or a combined operation of a traveling operation and an arm operation.

In this way, in this embodiment, the fourth bypass line connecting the first hydraulic pump and the first bypass line is added to the configuration of the second embodiment, so that the same effect as in the second embodiment can be obtained. In addition to this, it is possible to reduce the shock that occurs when the travel operation and other actuator operations are coupled.

FIG. 7 is a system diagram of a hydraulic circuit of a hydraulic excavator according to a fourth embodiment of the present invention.

This embodiment is different from the third embodiment shown in FIG. The point is that an on-off valve 61 is provided, and the other configuration is the third one.
This is the same as the embodiment. The on-off valve 61 has an upper position (the illustrated position) and a lower position, and is operated manually or by stepping on it. When the on-off valve 61 is in the upper position, the first bypass line 44 is conductive and becomes the same circuit as the third embodiment,
The same action is taken. When the on-off valve 61 is in the lower position, the first bypass line 44 is cut off at the on-off valve 61, and the second hydraulic pump 2 and the left-hand directional switching valve 1 are disconnected.
0 means communication is cut off.

By the way, when a hydraulic excavator crosses a long slope, the load is applied in the direction of the slope, so the driving pressure of the hydraulic motor at the bottom of the slope increases, and the driving pressure of the hydraulic motor above the slope decreases. , causing an imbalance in the driving pressures of both hydraulic motors. In the case of a circuit configuration where pressure oil is supplied to both hydraulic motors from the same hydraulic pump,
Since the pressure oil is supplied to the hydraulic motor, which has a lower driving pressure, the hydraulic excavator may turn around, which is dangerous.

For example, in the illustrated circuit, when the truck 106 driven by the left travel motor 4 is located above the slope, the driving pressure of the left travel motor 4 becomes low, and most of the pressure oil of the second hydraulic pump 2 is transferred to the first bypass line. 44 to the left travel motor 4, the hydraulic excavator will make a sharp turn.

The on-off valve 61 is provided to prevent such a curved state, and when crossing a slope, by setting the on-off valve 61 to the lower position, the hydraulic motor 4 is switched to the first hydraulic pump 1.
Also, since the hydraulic motor 6 is independently driven by the second hydraulic pump 2, the above-mentioned curved state can be prevented.

Note that the on-off valve 61 can also be installed in the first, second, and third embodiments. Further, the on-off valve 61 can be automatically operated using electric or hydraulic means only when straight forward travel is necessary.

As described above, in this embodiment, since an on-off valve is further provided in the first bypass line in addition to the configuration of the third embodiment, it not only has the same effect as the third embodiment, but also has the same effect as the third embodiment. It is possible to drive straight even if the vehicle is

As described above, in the present invention, the #41 directional valve group connected to the first hydraulic pump has a boom directional valve and an arm directional valve connected in parallel on the upstream side of the center bypass. and a left (or right) travel directional control valve connected to the downstream side of the center bypass, and a second directional control valve group connected to the M2 hydraulic pump to the upstream side of the center bypass. It consists of a right (or left) running directional switching valve connected to the right (or left) running directional switching valve and a packet directional switching valve connected downstream thereof, the second hydraulic pump and the packet directional switching valve, and the second hydraulic pump and 1st
A bypass pipe is provided between the left (or right) travel directional control valve belonging to the directional control valve group, so even during travel operation, other actuators can be operated independently without any problems while maintaining the straightness of travel. and make it work.

[Brief explanation of drawings]

The system diagrams of the hydraulic circuit of the bell, FIGS. 4, 5, 6 and 7 are shown in FIG. FIG. 3 is a system diagram of a hydraulic circuit of a hydraulic excavator according to a second, third, and fourth embodiment. 1.2...Hydraulic pump, 3...Swivel motor, 4...Left travel motor, 5...Arm cylinder, 6... Right travel motor, 7...
... Packet cylinder, 8 ... Boom cylinder, 10 ... Left travel directional control valve, 11A ...
... Directional switching valve for arm, 12... Directional switching valve for right travel, 13... Directional switching valve for packet, 14B... Directional switching valve for boom. ,44...
...First bypass line, 47...Second bypass line 0ff￥1Fig.2

Claims (1)

[Claims] 1. A first hydraulic pump, a second hydraulic pump, and a first directional valve group connected to the first hydraulic pump;
In a hydraulic circuit for a hydraulic excavator comprising a second directional valve group connected to a second hydraulic pump and an actuator connected to each directional valve, the first directional valve group is connected to its center. A boom directional control valve and an arm directional control valve connected in parallel on the upstream side of the bypass,
one travel directional switching valve connected to the downstream side of the center bypass; a packet directional switching valve connected to the downstream side of the second directional switching valve; and the second hydraulic pump. A hydraulic circuit between the packet directional control valve and the one running directional control valve. 2. The hydraulic circuit for a hydraulic excavator according to claim 1, wherein the bypass line between the second hydraulic pump and the packet directional control valve includes a flow rate restriction means. .