JP2766371B2 - Hydraulic circuit of excavator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit of a hydraulic shovel.

(Prior Art) Generally, a hydraulic excavator is provided with a swing body, a traveling body and attachments composed of a boom, an arm, a bucket, and the like. These are hydraulic actuators such as a swing motor, a left and right traveling motor, a boom cylinder, an arm cylinder, and a bucket cylinder. Driven by These hydraulic actuators are controlled individually or in combination by various directional control valves.

Conventionally, the most common hydraulic drive system divides these directional control valves into two groups, connects each group to a separate hydraulic pump, and connects each directional control valve to the hydraulic pump in each group in parallel. Is what you do.
FIG. 4 shows an example of the hydraulic circuit according to the prior art.

In FIG. 4, two hydraulic pumps 1 and 2 are provided, and a left traveling motor 3, a swing motor 5, and an arm cylinder 6 form a first group with respect to the first hydraulic pump 1, The right traveling motor 4, the boom cylinder 8, and the bucket cylinder 7 form a second group with respect to the hydraulic pump 2.

As a directional control valve for controlling the operation of each of the actuators, a left travel control valve 11 for the hydraulic pump 1 and a boom II
The control valve 13, the swing control valve 14, and the arm I control valve 15 are connected in parallel, respectively.
2, a boom I control valve 18 and a bucket control valve 17 are respectively connected in parallel, and an arm II control valve 16 is connected in tandem at the most downstream position.

The boom I control valve 18 and the boom II control valve 13 are switched in conjunction with each other by operating a boom operating lever (not shown). In particular, during a boom raising operation requiring a high speed, the hydraulic pressure of the hydraulic pump 1 is transmitted through a pipe 61. To join the hydraulic pump 2. Reference numeral 60 denotes a check valve for preventing the boom cylinder from lowering naturally. Similarly, the arm I control valve 15 and the arm II control valve 16 are switched in conjunction with each other by operating an arm operating lever (not shown). And is supplied to the arm cylinder 6 after being joined to the hydraulic pump 1.

Reference numeral 19 denotes a straight-running valve disposed upstream of the direction switching valve group. The straight-running valve is located at the most upstream position on the neutral oil passage 34 of the hydraulic pump 1. The boom I control valve 18 and the bucket control valve 17 are the straight-running valves. It is connected in parallel to the hydraulic pump 2 via 19. The directional control valves 11 to 18 have auxiliary switching valves 21 to 28 for shutting off the signal oil passage in conjunction with the switching of the main control valve, respectively.

Next, the pilot oil pressure generated by the pilot pump 31 is appropriately guided to the pressure receiving ports at both ends of the directional control valves 11 to 18 through operating pilot valves 29, 30 and the like (only the traveling valves are shown in the drawing) by the lever operation of the operator. Then, the direction control valve is switched to operate each actuator. In the figure, reference numeral 63 denotes a pilot hydraulic line, and reference numerals 64 to 67 denote pilot operation lines (only for traveling) guided from the pilot valve to the direction control valve.

Further, the pilot oil pressure constitutes a signal oil passage 32. The signal oil passage 32a includes the auxiliary switching valve 21, the signal oil passage 32b includes the auxiliary switching valve 22, and the signal oil passage 32c includes the auxiliary switching valves 23, 24, 25, 26, 27, and 28 in this order. Through the tank. The signal oil passage 32d branches off from the oil passage 32 and is guided to the port A of the straight traveling valve 19. Here, the hydraulic pressure generated by the pilot pump 31 is the pressure required by the throttle 33 when the directional control valves are in the neutral state, even though the signal oil passages 32a, 32b, and 32c communicate with the tank. Is secured and guided to the pilot valves 29, 30 and the like to enable the operation of each actuator.

The input port 38 of the left travel control valve 11 is connected to the parallel oil passage 35 of the hydraulic pump 1 via a throttle 39 with a check valve that supplies hydraulic pressure only to the input port 38 side. A throttle 41 is provided on the parallel oil passage 35 immediately before the arm I control valve.
When the turning control valve 15 and the turning control valve 14 are simultaneously operated, a decrease in turning acceleration force is prevented. Hydraulic pumps 1 and 2 each have a neutral oil passage 3
Pump control valves 42 and 4 provided at the most downstream of 4 and 36
A regulator 4 that communicates with the tank 44 through the valve 3 and maintains the discharge amount of the hydraulic pumps 1 and 2 at the minimum position when the upstream directional control valves are in a neutral state, that is, when no work is performed.
It has 5,46. 68, 69 are signal oil passages for the pump regulator. The hydraulic pumps 1, 2, 31 have relief valves 47, 48, 49 for setting respective discharge pressures.

One of the features of the above-mentioned prior art circuit lies in the function of the straight travel valve 19, which secures the straight travel of the main body when the travel and other actuators are simultaneously operated. The operation is described as follows: (1) When only traveling is operated; The traveling pilot valves 29 and 30 are operated by the traveling lever, and only the left traveling control valve 11 or the right traveling control valve 12 or both are simultaneously operated. When operated, the auxiliary switching valve 2
Either or both 1 and 22 serve as disconnection ports, and the signal oil passages 32a or 32b, or both 32a and 32b are shut off, but the signal oil passage 32c is in the tank because no other actuator is operated. Remains in communication with Accordingly, no oil pressure is generated in the oil passage 32d, and the straight travel valve 19 remains at the normal position 19a. For this reason, the left traveling motor 3 is independently driven by the hydraulic pump 1 and the right traveling motor 4 is independently driven by the hydraulic pump 2, so that the so-called first-speed traveling is achieved.

(2) When an actuator other than traveling is operated; When one or more of the directional control valves 13 to 18 other than traveling is operated, the signal oil passage 32c is disconnected from any of the auxiliary switching valves. Blocked by position, but signal passage
Since the tanks 32a and 32b communicate with each other, no oil pressure is generated in the oil passage 32d, and the straight travel valve 19 remains at the normal position 19a. Thereby, the actuators other than the traveling are also independently driven by the hydraulic pumps 1 and 2, respectively. However, in this circuit, the pressure oils of the left and right pumps merge when the boom is raised or the arm is retracted.

(3) When the other actuator is operated while the left and right traveling is operated simultaneously; When the left and right traveling and the other actuator are operated simultaneously, the auxiliary switching valves 21 and 22 interlocked with the left and right traveling control valves 11 and 12 are turned off, respectively. The signal oil passages 32a and 32b are shut off because of the position opening, and at least one of the auxiliary switching valves 23 to 28 interlocked with the control valves 13 to 18 of the other actuators becomes the disconnection position opening for the signal. Since the oil passage 32c is shut off, pressure oil is generated in the oil passage 32d, and the straight traveling valve 19 is switched to the switching position 19b.
As a result, the hydraulic pressure of the hydraulic pump 2 is supplied to the right traveling control valve 12 via the neutral oil passage 36, and at the same time, to the left traveling control valve 11 via the parallel oil passage 70, the position 19b of the straight traveling valve, and the neutral oil passage 34. Are also supplied in parallel.

On the other hand, the pressure oil of the hydraulic pump 1 is supplied in parallel to the actuator control valve operated via the parallel oil passage 35 or through the parallel oil passage 37 at the position 19b of the straight traveling valve. This means that even if other operations such as boom and turning are performed during straight running by simultaneous operation of left and right running, the hydraulic pump 2
The hydraulic pressure is exclusively supplied to the left and right traveling motors 3 and 4 to guarantee straight traveling of traveling by parallel driving. In this case, the hydraulic oil discharged from the hydraulic pump 2 is supplied to the two traveling motors 3, 4
In this case, the speed is half that of operating only the traveling, that is, the traveling 0.5 speed.

Next, the throttle valve 39 with a check valve will be described. When the other actuator is frequently operated during the straight traveling, the traveling speed becomes 1 with the intermittent switching of the straight traveling valve 19.
The speed is frequently changed to -0.5 speed, which causes a shock during traveling. Therefore, by appropriately setting the opening of the throttle valve 39 with a check valve, the partial pressure oil of one pump circuit on the actuator side having a high driving pressure such as boom raising and arm pushing can be relatively low. This is supplied to the traveling circuit on the pump 2 side to prevent a sudden change in traveling speed.

Also, when turning is performed during traveling, the turning acceleration pressure generally rises to the relief pressure of the circuit, and during turning acceleration, most of the pressure is discarded from the relief valve to the tank. Since a part can be supplied to the traveling circuit by the valve 39, energy loss can be prevented and traveling speed can be improved.

In FIG. 4, the throttle valve 39 with a check valve is connected to the left travel control valve.
Although the pressure oil is supplied only to 11, the straightness is maintained because the hydraulic pump 2 drives the traveling motors 3 and 4 in parallel.

As described above, according to the conventional circuit shown in FIG. 4, even if another actuator is operated during the straight traveling, the hydraulic oil of the pump 2 is preferentially supplied to the left and right traveling motors, so that the straight traveling property is maintained. Further, while providing an efficient hydraulic circuit for increasing the speed by supplying a part of surplus oil at the time of driving another actuator to the traveling circuit, it has the following disadvantages.

That is, when an operation with a small load such as boom lowering or arm retraction is performed during straight traveling, the traveling straight valve is switched, and the pump 1 drives the boom lowering or arm retraction, but the throttle valve 39 is at a lower pressure than the traveling circuit. Pressure oil cannot be supplied to the traveling side. As a result, the main body, which has been driven by the pumps 1 and 2 and the two pumps, is suddenly driven by the pump 2 only, resulting in rapid deceleration. If you repeat this process many times, the load will sway or spill, making it very difficult to control.

In the circuit shown in FIG. 1, when only traveling is operated, so-called first speed is used. However, in order to realize ultra-slow traveling for performing precise positioning work, the engine speed is controlled by a throttle lever provided separately for each operation. Operation is troublesome.

(Problems to be Solved by the Invention) Hydraulic excavators are used at all construction sites due to their versatility, but especially in traveling, the mobility has been improved by high-speed traveling in recent years, demonstrating their power in on-site movement, material transport, etc. doing. However, traveling work such as material transportation and backpacking of ready-mixed concrete sometimes requires very low-speed traveling. Further, in a combined operation including traveling, a change in traveling speed when starting or stopping the operation of another actuator induces load swing or spillage, which is not preferable for precision work.

SUMMARY OF THE INVENTION An object of the present invention is to provide a traveling independent hydraulic circuit which realizes a low-speed traveling at a speed lower than a normal speed in a traveling operation of a hydraulic shovel, and in which the traveling speed does not change even when another actuator is operated at the low-speed traveling. It is.

(Means for Solving the Problems) One traveling control valve is arranged at the most upstream position with respect to the first pump, an actuator other than traveling is connected in parallel downstream thereof, and the other pump is connected to the other pump with respect to the second pump. The travel control valve is arranged at the most upstream, actuators other than travel are connected in parallel downstream of it, and furthermore, the arm II control valve is connected in tandem at the most downstream, on the neutral oil path upstream of the one travel control valve. ,
Normally, a first position forming a parallel oil passage of the first pump's neutral oil passage and the second pump, and at the time of switching, the pressure oil of the second pump can also be supplied to one of the travel control valves. A second pump that can supply the pressure oil of one pump also to the parallel oil passage on the second pump side
In a hydraulic circuit of a hydraulic shovel provided with a straight traveling valve having a position of, a check is made between the parallel oil passage of the first pump and the inlet port of the one traveling control valve to normally allow flow only to the traveling control valve side. The valve is connected by a first opening / closing valve having a position for closing an oil passage at the time of switching, and is connected to the most downstream of the parallel oil passage of the second pump at the time of switching.
A second on-off valve having a position for closing the parallel oil passage of the pump and connecting the parallel oil passage to the upstream of the pump control valve on the first pump side at the time of switching is installed, and further for a signal for switching the straight traveling valve. In the oil passage, normally, the pressure receiving ports of the two on-off valves are opened to the tank, and at the time of switching, an electromagnetic valve having a position for communicating the pressure receiving port with the pilot pump is installed. In a state where the electromagnetic valves are switched, When the left and right traveling are simultaneously operated, the signal oil path is configured such that the three valves of the traveling straight valve and the first and second opening / closing valves are simultaneously switched. The signal oil passage is configured so that the second on-off valve returns to the normal position when the actuator is operated.

(Example) An example of the present invention will be described with reference to FIG. Note that the same components as in the prior art will be described with the same reference numerals as in FIG.

A position 50a at which the input port 38 of the left traveling control valve 11 and the parallel oil passage 35 of the hydraulic pump 1 are normally communicated by a throttle valve with a check valve, and a position 50b at which the oil passage is closed when signal pressure is received.
Is connected via a first on-off valve 50 having

A position 51a that normally closes the circuit between the parallel oil passage 37 of the pump 2 and the upstream of the pump control valve 42 of the pump 1
And a second opening / closing valve 51 having a communicating position 51b when receiving a signal pressure.

Immediately before the boom II auxiliary switching valve 23 in the signal oil passage 32c, the auxiliary switching valves 23 to 28 are normally connected to the pilot pump 31 in this order, and the first and second opening / closing valves are normally used.
Position 52a where the pressure receiving ports for signals 50 and 51 communicate with the tank
At the time of switching, the auxiliary switching valves 23 to 28 are connected to the pilot pump 31 via the throttle 56 and the first and second
An electromagnetic valve 52 having a position 52b for connecting the signal pressure receiving ports of the on-off valves 50, 51 to the pilot pump 31 is installed.

In the signal oil passage to the second on-off valve 51, the electromagnetic valve
In the state where 52 is switched to 52b, the signal pressure receiving port of the second on-off valve 51 is normally communicated with the pilot pump 31 at the position 53a, and the signal pressure receiving port of the on-off valve 51 is received when the signal pressure is applied. A switching valve 53 having a position 53b that communicates with the tank is installed.

1) One output port B of the solenoid valve 52 and the input port E of the auxiliary switching valve 23 are connected by a signal oil passage 75, and 2) the solenoid valve 52 is connected between the various switching valves 50, 51, 52 and 53. 3) the other output port C of the solenoid valve 52 and the signal pressure receiving port D of the first on-off valve 50 are signaled. 4) The other output port C of the solenoid valve 52 and the input port G of the switching valve 53 are connected by a signal oil passage 78. 5) The output port H of the switching valve 53 and the second opening / closing valve 51 are connected. The signal pressure receiving ports I are connected by signal oil passages 79, respectively.

FIG. 2 shows a second embodiment of the present invention, in which the switching valve 53 is omitted, the signal oil passage 78 is directly led to the pressure receiving port I of the second on-off valve 51, and another signal oil passage is provided. 76 is connected to the other signal pressure receiving port J of the on-off valve 51, and the signal pressure is applied to the I port or the J port to switch the on-off valve 51 to 51b or 51a, respectively.
When acting on the port at the same time, the position 51a is held by the spring force K.

FIG. 3 shows a third embodiment of the present invention, in which the operation of the second on-off valve 51 is incorporated inside the arm II control valve 16. In the figure, at one switching position 16b of the arm II control valve, the extension oil passage 71 of the parallel oil passage 37 of the hydraulic pump 2 is connected to the pump control valve 42 of the hydraulic pump 1 via a pipe 72.

Further, when the control valve 16 is switched to 16b, the auxiliary switching valve 26
The signal oil passage of No. is set as the communication position A.

A signal oil passage from the output port H of the switching valve 53
79 is led to one pressure receiving port L of the arm II control valve 16.

(Operation) When the solenoid valve 52 is in the normal position 52a in FIG.
The pressure oil of the pilot pump 31 is communicated from the signal oil passage 32c to the tank 44 through 75 and the auxiliary switching valves 23 to 28, while the signal pressure receiving ports D and I of the open / close 50 and 51 are also connected to the solenoid valve 52a.
Since the valve is in communication with the tank via the position, the on-off valves 50 and 51 do not operate, so that there is no functional difference from the conventional circuit.

Next, when the solenoid valve 52 is switched to the switching position 52b, the signal oil passages 77, 78, 79 are connected to the pilot pump 31 through the position 52b of the solenoid valve, and the signal oil passages 75, 76 are connected to the solenoid valve 52. Is connected to the pilot pump 31 via the throttle 56 in the switching position 52b. On the other hand, the signal oil passages 32a and 32b are
It leads to the tank via 22.

In the state where the solenoid valve 52 is switched to 52b in this way, 1) When the operator operates the left and right traveling control valves 11 and 12 simultaneously to perform only traveling work, the linked auxiliary switching valves 21 and 2 are operated.
2 closes the signal-like oil passages 32a and 32b, while the switching position of the solenoid valve
Due to the presence of the throttle 56 in 52b, pressure is generated in the signal oil passage 32, and this pressure switches the straight traveling valve 19 to the switching position 19b via the signal oil passage 32d. Also, this signal pressure is
b, the on / off valve 50 is switched to the switching position 50b via the signal oil passage 77, and the on / off valve 51 is further switched to 51b via the signal oil passages 78, 79. At this time, the signal oil passages 75 and 76 are still in communication with the tank and no pressure is generated. Since the straight travel valve 19 is switched to the switching position 19b, the left and right traveling motors 3 and 4 are driven in parallel by the hydraulic pump 2, so that traveling at half the normal traveling speed, that is, 0.5 speed is possible. The pressure oil is shut off the support to the traveling circuit because the on-off valve 50 is in the closed position 50b, and the on-off valve 51
To connect the parallel oil passages 37 and 71 to the tank circuit, the position 19b of the straight travel valve 19, the parallel oil passages 37 and 71, and the on-off valve
The tank is unloaded to the tank 44 via the pipe 51, the pipe 72, and the pump control valve 42. At this time, in the pump 1, the control pressure generated by the pump control valve 42 acts on the regulator 45, and the discharge amount is kept to a minimum, thereby preventing the loss of energy.

2) When another actuator is operated during traveling at the traveling 0.5 speed, at least one of the auxiliary switching valves 23 to 28 shuts off the signal oil passage 75 so that the pressure is also applied to the signal oil passage 76. Occurs and switches the switching valve 53 to 53b. As a result, the signal oil passage 79 which has generated the pressure oil up to that time communicates with the tank, the on-off valve 51 is returned to the position 51a by the spring K, and the parallel oil passages 37, 71 are cut off from the tank circuit.

That is, when the actuators other than the traveling are simultaneously operated during the straight traveling at the traveling 0.5 speed, the hydraulic oil of the hydraulic pump 2 is supplied in parallel to the left and right traveling motors 3 and 4 so that the traveling at the very low speed can be continued and the hydraulic pressure of the hydraulic pump 1 Indicates that the on-off valve 50 is in the closed position
50b, the on-off valve 51 is held at the closed position 51a, so that it is supplied only to operated actuators other than traveling. This makes it possible to realize running independence in which the running speed does not change even if the running and other actuators are simultaneously operated.

In the second embodiment shown in FIG.
1) When only driving is operated, the signal oil passage 78 is directly connected to the second
2) When the actuator other than traveling is operated in this state, the signal pressure generated in the signal oil passage 76 is directly transmitted to the on-off valve 51.
The open / close valve 51 receives the same pressure at the pressure receiving ports at both ends, and thus balances. However, the normal position 51a is held by the spring force K, and both are shown in FIG. Works the same as a circuit.

Further, in the third embodiment shown in FIG.
1) When only traveling is operated, the signal pressure acts on one pilot port L of the arm II switching valve 16 via the oil passage 78, the switching valve 53a, and the oil passage 79, and the parallel oil The paths 37, 71 are kept in the closed position 16b. At this time, the auxiliary switching valve 26 also has the same operation as the circuit in FIG.

2) When actuators other than traveling are simultaneously operated during traveling straight, signal pressure is generated in the oil passage 76 and the switching valve 53
To 53b to open the signal oil passage 79 to the tank,
The arm II switching valve 16 returns to the neutral position 16c, and the parallel oil passage 71
Cut off. That is, this also operates in the same manner as the circuit shown in FIG.

That is, in the configuration in which the second opening / closing valve 51 is incorporated in the arm II switching valve, the signal oil passage 79 is opened to the tank by the switching valve 53 even when the arm II is operated during the low-speed traveling at the switching position 16b. , There is no risk of both functions interfering, arm
It can realize the rational action that II prioritizes.

In the second embodiment of the present invention shown in FIG. 2, since the signal oil passages 78 and 76 are directly led to both ends of the on-off valve 51, the switching valve 53 can be omitted. An inexpensive circuit can be provided.

In the third embodiment of the present invention shown in FIG. 3, the function of the on-off valve 51 can be incorporated into the other switching position of the arm II switching valve, so that the on-off valve 51 can be omitted. An efficient circuit can be provided.

(Effects) According to the present invention, when the solenoid valve 52 is switched to the switching position 52b by a switch or the like separately provided in advance, when only the left and right traveling is simultaneously operated, the hydraulic oil of the pump 2 is moved to the left and right traveling mochi 3. , 4, it is possible to realize a traveling speed that is half that of the conventional circuit (that is, a very low traveling speed of 0.5).

In addition, even if another actuator is operated during the low-speed traveling, the pump 1 cannot supply the pressurized oil to the traveling circuit, so the independence of traveling is guaranteed. In other words, when the attachment is operated while traveling with the hydraulic excavator, for example, when soil is removed from the bucket or backfill of ready-mixed concrete is performed, a smooth precision operation can be performed without causing a change in traveling speed. Of course, turn off the switch etc. and move the solenoid valve to the normal position 52a.
When the value is returned to, the traveling speed can be increased (first speed) as before.

[Brief description of the drawings]

 FIG. 1 shows a circuit according to a first embodiment of the present invention. FIG. 2 shows a circuit of the second embodiment. FIG. 3 shows a circuit of the third embodiment. FIG. 4 shows a known hydraulic circuit. In the figure, 1,2,31 ... hydraulic pump 3,4 ... travel motor, 5 ... turn motor 6 ... arm cylinder, 7 ... bucket cylinder 8 ... boom cylinder, 11,12 ... travel control valve 13 ~ 18 ... Directional control valve for other actuators 19 ... Traveling straight valve, 21 ~ 28 ... Auxiliary switching valve 29,30 ... Pilot valve 32 ... Signal oil passage, 33 ... Throttle 34 ... Neutral Oil passage, 35… Parallel oil passage 36… Neutral oil passage, 37… Parallel oil passage 38… Input port 39… Throttle valve with check valve 41… Throttle 42, 43… Pump control valve 44… Tank, 45, 46… Regulator 47, 48, 49… Relief valve 50, 51… Open / close valve, 52… Solenoid valve 53… Switching valve, 56… Restrictor 60… Check valve, 61, 62… ... Piping 63 ... Pilot pressure oil line 64-67 ... Bilot operation line 68,69 ... Signal oil passage, 70,71 ... Parallel oil passage 72 ... Piping, 75-79 ... Signal oil Road

Claims (1)

(57) [Claims] A first travel control valve is arranged at the most upstream position with respect to the first pump, an actuator other than the travel is connected in parallel downstream thereof, and the other travel control valve is connected to the second pump with the other travel control valve. It is arranged at the most upstream, the actuators other than traveling are connected in parallel downstream of it, and furthermore, the arm II control valve is connected in tandem at the most downstream, on the neutral oil path upstream of the one traveling control valve, normally A first position constituting a parallel oil passage of the first pump and a second oil passage, and at the time of switching, pressure oil of the second pump can also be supplied to one traveling control valve; In a hydraulic circuit of a hydraulic shovel provided with a traveling straight valve having a second position capable of supplying pressure oil also to a parallel oil passage on a second pump side, a parallel oil passage of the first pump and the one traveling control are provided. Normally flows only between the travel control valve side between the valve inlet port It is connected by a throttle valve with a check valve to allow, connected at the time of switching by a first opening / closing valve having a position to close the oil passage, and at the most downstream of the parallel oil passage of the second pump, usually the second pump A second on-off valve having a position for closing the parallel oil passage and connecting the parallel oil passage upstream of the pump control valve on the first pump side at the time of switching is installed, and further a signal oil passage for switching the straight travel valve. During normal operation, the pressure receiving ports of the two on-off valves are opened to the tank, and at the time of switching, a solenoid valve having a position communicating the pressure receiving port with the pilot pump is installed. When the traveling is simultaneously operated, the traveling straight valve, the first and second traveling
A signal hydraulic path is configured such that the three valves of the on-off valve are simultaneously switched, and when an arbitrary actuator other than traveling is operated in this state, a signal is issued so as to return the second on-off valve to the normal position. A hydraulic circuit for a hydraulic shovel, comprising a hydraulic oil passage.