JPH0412335B2 - - Google Patents

Description

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

In general, a hydraulic excavator, for example, a hydraulic excavator, is equipped with a revolving body, a running body, and attachments such as a boom, an arm, and a bucket. Driven by an actuator. These actuators are controlled individually or in combination by directional control valves. 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, 10
Reference numeral 1 denotes a revolving body, which is disposed on the upper part of the traveling body 102;
It turns by driving the turning motor 3. 1
04 is a left truck, which is driven by the left travel motor 4. 106 is a right truck, right travel motor 6
Driven by. 108 is a boom, 109 is an arm, and 110 is a bucket, which constitute a working machine. 8 is a boom cylinder that operates the boom 108, 5 is an arm cylinder that operates the arm 109, and 7 is a bucket cylinder that operates the bucket 110.

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 multiple actuators are operated in a complex manner, the movement of each actuator is affected by each other's operating pressure, making it difficult to control accurately. If it is not possible to do so, and furthermore, there is an extreme difference between the operating pressures of multiple actuators that operate in combination depending on the load condition applied to the actuators,
Since pressure oil flows only to the actuator with the lower operating pressure, 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 and 2 are provided, a swing motor 3, a left traveling motor 4 and an arm cylinder 5 form one group for the hydraulic pump 1, and for the hydraulic pump 2, Right travel motor 6, bucket cylinder 7 and boom cylinder 8
form other groups. Directional switching valves 9, 10, and 11 are connected to the hydraulic pump 1 in tandem, and directional switching valves 12, 13, and 14 are connected to the hydraulic pump 2 in tandem. On-off valves 18 and 19 for opening and closing communication with the tank 17 are provided downstream of the directional control valve group 15 consisting of the directional control valves 9 to 11 and downstream of the directional control valve group 16 including the directional control valves 12 to 14. Each is provided. The pilot valves 20 to 25 send pilot pressure signals to the directional control valves 9 to 14, respectively, by pilot pressure signal circuits a to 1 to control the direction and flow rate of these pressure oils. Pilot valve 20-25
are commonly connected to a pilot pump 26 which is a hydraulic power source. Two directional valve groups 15, 16
Bypass circuits 27, 28, and 29 are provided therebetween, and a bypass circuit 30 is provided between the hydraulic pump 1 and the directional control valve 11. The bypass circuit 27 is provided with a restriction valve 31 having a flow rate restriction position and an open position, and the bypass circuit 30 is provided with a restriction valve 31 having a flow rate restriction position and an opening position.
2 is provided. 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 control valve 10 and the directional control valve 12 are connected in parallel to the hydraulic pump 2 by the bypass circuit 27. Connected. Therefore, when the pilot valve 21 for left travel and the pilot valve 23 for right travel generate pilot pressure signals, both the directional switching valve 10 and the directional switching valve 12 operate, and the left travel motor 4 and the right travel motor 6 and 6 are supplied with pressure oil from the hydraulic pump 2. Thus, the swing motor 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) Swivel operation and arm operation Pressure oil from the hydraulic pump 1 is supplied to the swing motor 8 by operating the swing pilot valve 20 in the same manner as described above. In response to the pilot pressure signal from the pilot pressure signal circuit a or b for turning, the switching valve 34 is switched to the pilot pressure signal circuit e for the arm.
Alternatively, f is communicated with the pilot pressure signal circuit n, so that the pilot pressure signal from the arm pilot valve 22 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 is capable of performing various combined operations, but problems arise when performing the following combined operations.

(a) When attempting to dump the boom 108 while traveling, the pressure oil from the hydraulic pump 1 is supplied only to the left travel motor 4, the pressure oil from the hydraulic pump 2 is supplied only to the right travel motor 6, and the boom cylinder 8
is not supplied with pressure oil and therefore boom 1
08 cannot be moved.

(b) When attempting to dump the arm 109 while traveling, since the directional control valve 10 has been switched, the pressure oil supplied to the arm cylinder 5 will be supplied via the throttle 32, and as a result, Arm 109 cannot be raised sufficiently.

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

(d) When traveling with a load suspended from the tip of the bucket 110, even if you attempt to cloud the bucket 110 while driving to rehang the load, the directional control valve 12 has been switched, so the bucket 110 cannot be moved. It is not possible. this is,
The same applies even when you are not traveling with a load suspended as described above, and you cannot move the bucket while traveling.

The purpose of the present invention is to solve the above-mentioned conventional problems,
To provide a hydraulic circuit for a hydraulic excavator that can operate other actuators without any hindrance to straight traveling even during traveling operation.

a first hydraulic pump, a second hydraulic pump, a first directional valve group connected to the first hydraulic pump, a second directional valve group connected to the second hydraulic pump, In a hydraulic circuit for a hydraulic excavator comprising an actuator connected to each directional valve, the first directional valve group is connected in parallel to the upstream side of its center bypass, and a boom directional valve and an arm directional valve are connected in parallel. and one traveling directional switching valve connected to the downstream side of the center bypass, and the other traveling directional switching valve connecting the second directional valve group to the upstream side of the center bypass. a bucket directional switching valve connected to the downstream side of the center bypass; It is characterized in that a bypass pipe line is provided in between.

When the travel direction changeover valve is switched and the hydraulic excavator is in the travel state, when the boom direction changeover valve or the arm direction changeover valve is operated, the travel direction changeover valve receives pressure from the second hydraulic pump. oil is supplied,
Pressure oil is supplied from the first hydraulic pump to the boom directional switching valve or the arm directional switching valve, allowing the boom or arm to be driven while traveling. Similarly, when the hydraulic excavator is in a running state, when the bucket directional control valve is operated, pressure oil is supplied from the second hydraulic pump to the traveling directional control valve and to the bucket directional control valve. Ru. Since this pressure oil is supplied through the flow rate restriction means, running is reliably maintained.

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

FIG. 4 is a system diagram of the hydraulic circuit of the hydraulic excavator according to the 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. 11A is a first arm directional switching valve, 11B 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 second boom directional control valve 14B, 42 is a pipe line between the second hydraulic pump 2 and the right travel direction control valve 12, and 44 is a pipe line between the second hydraulic pump 2 and the right travel direction control valve 12B. 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. 4
A second bypass line 7 is branched from a portion of the first bypass line 44 after the check valve 45, and connects this branch point to the bucket directional control valve 13. 48 and 49 are a check valve and a throttle, respectively, which are interposed in the second bypass line 47. In addition, 50 is a load check valve provided on the input port side of each directional control valve, 51,
52 is a relief valve for circuit protection. 53 is
This is a parallel circuit that connects the first hydraulic pump 1 and the swing directional control valve 9, and the first hydraulic pump 1 and the first arm directional control valve 11A. The directional switching valve 14B, the turning directional switching valve 9, and the first arm directional switching valve 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, the right travel motor 6 is supplied with pressure oil from the second hydraulic pump 2 via the right travel direction switching valve 12, and the left travel motor 4 is supplied with pressure oil from the first bypass line 44 and the left travel direction changeover valve. Pressure oil is supplied from the second hydraulic pump 2 via 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 a combined operation of a swing operation and a boom operation is frequently performed when working with a hydraulic excavator. By the way, in a conventional hydraulic circuit in which the swing motor 3 and the boom cylinder 8 are driven by separate hydraulic pumps 1 and 2 as shown in FIG. was relieved from the relief valve, resulting in loss of horsepower and poor efficiency. That is, since the rotating body has a large inertia, the operating pressure of the rotating motor 3 becomes higher than the opening pressure of the relief valve during acceleration. However, in the hydraulic circuit of this embodiment, the swing direction switching valve 9 and the second boom direction switching valve 14B
are connected in parallel, the rotation motor 3
The increase in the operating pressure is suppressed by the operating pressure of the boom cylinder 8, so that excess pressure oil from the swing motor 3 is 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 control valve 14
The connection between A and the second boom directional control valve 14B is configured to perform a two-stage operation, and when the first stage is operated, only the first boom directional switch valve 14A is operated, and when the second stage is operated, the first boom directional switch valve 14A is operated. If the first and second boom directional switching valves 14A and 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 first hydraulic pump 1 is supplied to the swing motor 3 via the swing direction switching valve 9, and the arm cylinder 5 is supplied with the first arm direction switching valve 11A. The pressure oil of the first hydraulic pump 1 is
Further, pressure oil from the second hydraulic pump is supplied via the second arm directional switching valve 11B.

(4) Traveling operation and boom operation Pressure oil from the second hydraulic pump 2 is supplied to the left traveling motor 4 via the first bypass line 44 and the left traveling direction switching valve 10, and the pressure oil is supplied to the right traveling motor 6. Pressure oil from the second hydraulic pump 2 is supplied via the right travel direction switching valve 12. or,
Pressure oil from the first hydraulic pump 1 is supplied to the boom cylinder 8 via the second boom directional switching valve 14B. Therefore, in this embodiment, a combined operation of traveling operation and boom operation is possible, and moreover, traveling operation and boom operation can be made independent, and straight forward traveling is possible.

(5) Traveling operation and arm operation Pressure oil from the second hydraulic pump 2 is supplied to the left traveling motor 4 via the first bypass line 44 and the left traveling direction switching valve 10, and the pressure oil is supplied to the right traveling motor 6. Pressure oil from the second hydraulic pump 2 is supplied via the right travel direction switching valve 12. or,
Pressure oil from the first hydraulic pump 1 is supplied to the arm cylinder 5 via the first arm directional switching valve 11A. Therefore, the traveling motion and the arm motion are independent, and the arm 109 can be raised sufficiently without hindering straight traveling, and even if the vehicle idles while traveling when escaping from the wetland, sufficient force can be applied to the arm 109. This allows for no inconvenience in escaping from the wetland.

(6) Travel operation and bucket operation The left travel motor 4 has a left travel directional control valve 1.
Pressure oil from the first hydraulic pump 1 is supplied to the right travel motor 6 via a right travel directional switching valve 12 . Further, the bucket cylinder 7 includes a first bypass line 44, a second bypass line 47 branching from the first bypass line 44, and a bucket directional control valve 1.
3, the pressure oil of the second hydraulic pump 2 is supplied, and at the same time, the left travel direction switching valve 1
The pressure oil of the first hydraulic pump 1 is transferred to the second hydraulic pump 2 through the first bypass line 44, the second bypass line 47, and the bucket directional control valve 13, which branch from before the input port 0. It is supplied by merging with the pressure oil. Such a branching of the pressure oil to the bucket cylinder 7 is carried out without any problem since the driving pressure of the bucket cylinder is normally lower than the driving pressure of the travel motor. In this way, it is possible to perform a bucket action while driving. Also, in this case,
The driving pressure of the left and right travel motors 4 and 6 is approximately the first
Since the pressure is equal to the pressure in the bypass line 44, the straightness of running is not lost. By the way, if the driving pressure of the bucketed cylinder 8 is low, in the above-mentioned circuit, the bucketed cylinder 8
The amount of pressure oil sent to the travel motors 4 and 6 increases, and therefore the amount of pressure oil supplied to the travel motors 4 and 6 decreases, which may result in abnormally slow travel.
The throttle 49 is provided to prevent this, and the flow rate of the pressure oil flowing into the bucket cylinder 7 is restricted by the throttle 49.

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 arm, which are connected in parallel on the upstream side of the center bypass. The second directional valve group is composed of a directional switching valve for right running connected to the most upstream side of the center bypass, and a directional switching valve for left running connected to the downstream side of the second directional switching valve group. It consists of a first boom directional control valve and a bucket directional control valve connected in parallel on the downstream side, and an arm directional control valve connected to the most downstream side, and a second directional control valve connected to the 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 first bypass line and the bucket directional control valve via a throttle. Since the bypass line is provided, it is possible to perform not only the combined operation of the turning operation and the operation of other actuators, but also the combined operation of the travel operation and the operation of other actuators without any problems. 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. 5 is a system diagram of a hydraulic circuit of a hydraulic excavator according to a second embodiment of the present invention.

This embodiment differs from the first embodiment in that a third bypass line is provided between the middle of the first bypass line 44 and the first boom directional control valve 14A. The parts are the same as in the first embodiment. That is, 54 branches from the first bypass line 44 and connects to the first boom directional control valve 14.
This is a third bypass line provided between the input port of A and the input port of A. 55 and 56 are a check valve and a throttle, respectively, which are interposed in the third bypass line 54.

In the first embodiment, when it is necessary to make the swing operation and the boom operation independent, the connection between the first and second boom directional control valves 14A and 14B is configured to operate in two stages. When configured,
In the first embodiment, in the case of a combination of travel operation and boom operation, the first boom directional control valve 14A
Even if the first stage operation of activating the boom cylinder 8 is performed, the boom cylinder 8 cannot be driven. 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 cut off, and the second boom directional switching valve 14B is switched. This is because it has not been done.

However, in this embodiment, since the third bypass line 54 is provided, when performing traveling operation and boom operation, when the boom lever is operated to perform the first stage operation, the first boom directional switching valve 14A is activated. The pressure oil of the first and second hydraulic pumps 1 and 2 is supplied to the boom cylinder 8 via the first bypass line 44, the third bypass line 54, and the first boom directional switching valve 14A. Perform boom operation. In this case, if the driving pressure of the boom cylinder 8 is low, the amount of pressurized oil sent from the first and second hydraulic pumps 1 and 2 to the boom cylinder 8 increases, which may result in abnormally slow travel. The throttle 56 is provided to prevent this, and the flow rate of the pressure oil flowing into the boom cylinder 8 is restricted by the throttle 56. Note that the aperture 56 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 first boom directional control valve. In addition to achieving the same effect as in the embodiment, 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 travel operation and boom operation. This can be done without any problem even when performing complex operations.

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. 59,6
0 is a check valve and a throttle interposed in the fourth bypass line 58.

In the case of the second embodiment described above, when the boom is operated during the traveling operation, the pressure oil that had been supplied to the left and right traveling motors 4 and 6 is reduced by approximately half. Therefore, a situation may occur where the traveling speed suddenly decreases and gives a shock to the operator.

However, in this embodiment, a part of the pressure oil of the first hydraulic pump 1 is supplied to the travel motor 4 via the first bypass line 44 by the fourth bypass line 58, and the fourth bypass line By appropriately setting the aperture 60 of the boom 58, shock can be reduced and independence of boom operation can be maintained. 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, this embodiment has the same effect as the second embodiment because it further includes a fourth bypass line that connects the first bypass line, the hydraulic pump, and the first bypass line to the configuration of the second embodiment. In addition, it is possible to reduce shocks that occur during a combined operation of traveling operation and other actuator operations.

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 only difference is that an on-off valve 61 is provided, and the other configurations are the same as the third 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 electrically connected to form the same circuit as in the third embodiment, and the same operation is performed. 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 communication between the second hydraulic pump 2 and the left travel direction switching valve 10 is cut off.

By the way, when a hydraulic excavator crosses a long slope, a 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 located above the slope becomes smaller, causing an imbalance between the driving pressures of both hydraulic motors. In the case of a circuit configuration in which pressure oil is supplied to both hydraulic motors from the same hydraulic pump, the pressure oil is supplied to the hydraulic motor with lower drive pressure, causing the hydraulic excavator to move in a dangerous direction. It is.
For example, in the illustrated circuit, when the truck 106 driven by the left travel motor 4 is located above the slope, the drive 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 operated by the first hydraulic pump 1 or Since the hydraulic motors 6 are each independently driven by the second hydraulic pump 2, the above-mentioned curved state can be prevented.

Note that the on-off valves 61 are installed at the first, second, and third valves.
This can also be done in the embodiment. Further, the on-off valve 61 can be automatically operated using electric or hydraulic means only when straight forward travel is required.

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 first directional valve group connected to the first hydraulic pump includes a boom directional valve and an arm directional valve connected in parallel on the upstream side of the center bypass. and the left (or right) connected to the downstream side of the center bypass
The second directional valve group connected to the second hydraulic pump is composed of a right (or left) running directional valve connected to the upstream side of the center bypass and a second directional valve group connected to the second hydraulic pump. A bypass pipe is provided by interposing a flow rate restriction means between the second hydraulic pump and the bucket directional switching valve, and the second hydraulic pump is configured with a bucket directional switching valve connected downstream. Since a bypass pipe is provided between the pump and the left (or right) travel directional control valve belonging to the first directional control valve group, the other actuators can be operated to maintain the straightness of travel even during travel operation. It can be operated independently without any problems.

[Brief explanation of drawings]

Figure 1 is a side view of the overall configuration of the hydraulic excavator, Figure 2 is a plan view of the hydraulic excavator shown in Figure 1, and Figure 3 is a side view of the overall configuration of the hydraulic excavator.
The figure is a system diagram of a hydraulic circuit of a conventional hydraulic excavator, and FIGS. 4, 5, 6, and 7 are hydraulic excavators according to the first, second, third, and fourth embodiments of the present invention. FIG. 3 is a system diagram of a hydraulic circuit. 1, 2...Hydraulic pump, 3...Swivel motor, 4
...Left travel motor, 5...Arm cylinder, 6...
...Right travel motor, 7...Bucket cylinder, 8...
...Boom cylinder, 10... Directional switching valve for left running, 11A... Directional switching valve for arm, 12... Directional switching valve for right running, 13... Directional switching valve for bucket, 14B... Directional switching valve for boom , 44...first bypass line, 47...second bypass line.

Claims (1)

[Claims] 1 a first hydraulic pump, a second hydraulic pump,
a first directional valve group connected to a first hydraulic pump; a second directional valve group connected to a second hydraulic pump;
In the hydraulic circuit of a hydraulic excavator comprising a directional valve group and an actuator connected to each directional valve, the first directional valve group is connected in parallel to the upstream side of its center bypass. It is composed of a switching valve and an arm directional switching valve, and one traveling directional switching valve connected to the downstream side of the center bypass, and the other one connecting the second directional switching valve group to the upstream side of the center bypass. and a bucket directional control valve connected to the downstream side of the center bypass; A hydraulic circuit for a hydraulic excavator, characterized in that a bypass pipe line is provided between a directional control valve for a bucket.