JPS60123630A - Control circuit for construction vehicle - Google Patents

Abstract

PURPOSE:To provide running straightness and high running force, by installing a switching valve and a relief valve which hold a slightly high set pressure through driving of two running motors with the aid of only the pump of the one circuit during running, and hold an ordinary set pressure during non-running. CONSTITUTION:In a 2-variable-volume-hydraulic-pump system, a bucket control valve 19, a boom control valve 20 and an arm control valve 29 are connected in parallel to a first hydraulic pump P1 through a running control valve 18 and a switching valve 54. Meanwhile, a slewing control valve 22, a boom control valve 32 and an arm control valve 26 are connected in parallel to a second hydraulic pump P2, and a running control valve 24 is connected in parallel thereto through a switching valve 57. Further, during switching of the switching valve 54, the pressure oil of the first hydraulic pump is communicated to the upper stream of a running control valve 24 in other circuit, and the switching valve 54 is switched during control of the running control valve 18. Further, high pressure set and low pressure set relief valves 52 and 53 are connected to a center bypass passage through a switching valve 51.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a control circuit for a construction vehicle that includes two circuit systems and each circuit system is provided with one travel motor.

(Conventional control circuit) Figure 1 shows a conventional HIftj4 for a power excavator.
In the circuit, one circuit system connected to the pump Pl includes a switching valve 1 connected to the travel motor, a switching valve 2 connected to the boom cylinder 2, a switching valve 3 connected to the packet cylinder, and a switching valve 4 for arm merging. are connected to each other via a center bypass passage 5, and the switching valves 1 to 3 are also communicated via a parallel passage 6.

The other circuit system connected to the pump P2 also includes a switching valve 7 connected to the travel motor. Boom merging switching valve 8,
A switching valve 9 connected to the swing motor t1i and a switching valve 1o connected to the arm cylinder are connected via a center bypass passage 11 and a parallel passage 12.

In the conventional control circuit configured as described above, both the pumps P
If the volumetric efficiencies of I and P2 differ, or if the loads on actuators other than the travel motor differ, the speed of each travel motor will not be constant, which may impair the straight-line performance of the vehicle. there were.

In addition, the above circuit system includes each relief 5t13,
] 4 to maintain the set pressure, for example,
While the vehicle is running, when it hits an obstacle that cannot be overcome with the set pressure of the relief valve 3.14, even if the obstacle can be overcome by slightly increasing the power, this conventional The disadvantage of this circuit was that it could not be powered up.

(Objective of the Present Invention) A first object of the present invention is to provide a control circuit that guarantees the straightness of the vehicle even if the volumetric efficiencies of both pumps are different.

A second object is to provide a control circuit that maintains a high circuit pressure when the vehicle hits an obstacle and increases the power enough to overcome the obstacle.

The third purpose is that even when maintaining a high circuit pressure as described above, high voltage is not applied to circuits other than the traveling motor, and therefore it is necessary to improve the pressure resistance of the circuits, etc. It is to provide no control circuit.

(Embodiment of the present invention) In the first embodiment shown in FIG. A switching valve 18~2° is connected to the 7 actuator.

Further, the other circuit system to which the variable discharge pump P2 is connected is connected to a travel motor 21, a swing motor 22, and an arm cylinder 23, and switching valves 24 to 26 are connected to each of these actuators.

Then, a parallel passage 28 is connected to the pump passage 27 of the pump P1, and this parallel passage 28
The switching valves 18 to 2o are connected in parallel to each other.

Furthermore, in this embodiment, a switching valve 28 for arm merging is also connected to the parallel passage 28 at the most downstream of each of the switching valves 18 to 2o.

A parallel passage 31 is also connected to the pump passage 3o of the pump P2, and each of the switching valves 24 to 26 is connected in parallel to this parallel passage 31. A switching valve 32 is connected.

Each switching valve as described above switches in proportion to the amount of operation of the pilot operation mechanisms 33 to 35 and 38 to 38 provided in each circuit system, but these pilot operations #! The pimit pressure generated by operating the mechanism is the shuttle gT38
~43. The highest pressure is selected by 44~48, and the highest pressure is selected by pump P1. It is arranged to be supplied to the regulator 49.50 of P2.

A selector valve 51 is connected to the pump passage 27 of one circuit system as described above, and this selector valve 51 has its pilot pressure chamber 51a
It is connected to shuttle valve 39.

Therefore, this selector valve 51 is
5 is maintained at the normal position S shown in the figure. In this normal position S, the pump passage 27 is communicated with the relief valve 52 having a normal set pressure.

Furthermore, when the travel motor 15 is driven, the pilot pressure at that time flows into the pilot pressure chamber 51a via the shuttle valve 38, so the selector valve 51 is switched to the switching position T. At this switching position T, the pump passage 27 communicates with the relief valve 53, and the set pressure of the relief valve 53 is set somewhat higher than that of the relief valve 52.

As is clear from this, when the travel motor 15 is being driven, the set pressure of the circuit is somewhat higher than when the travel motor I5 is not being driven.

Further, a control valve 54 is connected to the parallel passage 28, and a pilot pressure chamber 54a of the control valve 54 is connected to the shuttle valve 38 in the same way as the two-legged selector valve 51.

Therefore, when the travel motor 15 is not driven,
Although the control valve 54 maintains the illustrated normal position X,
When the travel motor 15 is driven, the control valve 54 is switched to the switching position Y by the pilot pressure at that time.

When the control valve 54 is switched to the switching position Y, the parallel passage 28 is closed, so that communication between the pump passage 27 and the other switching valves 18, 20, and 28 except for the switching valve 18 is cut off. The pump passage 27 communicates with the downstream side of the check valve 56 provided in the supply passage 55 of the other circuit system.

This supply passage 55 communicates with the pump passage 30 of the other pump P2, and is also connected to the check valve t58 and the priority valve 57 on the upstream side. However, if this check valve 56 is within the supply passage age, the priority valve 5
It may be provided on the upstream side of 7.

The priority valve 57 is connected to the shuttle valve 58 which is connected to the shuttle valve 47 and the pilot line 58 of the switching valve 32 for boom merging.
When any one of these is operated, the priority valve 57 is switched from the normal position F to the switching position G.

In addition, the reference numerals 60 and 61 in the figure are unload valves, which are normally operated as follows.
It remains in the unloaded position shown, but is switched to the closed position under the influence of pilot pressure flowing into the regulator 48,50.

Further, reference numeral 82 is a relief valve for controlling the circuit pressure of the other circuit system, which is connected to the pump passage 29, and
Similar to the relief valve 52, the normal set pressure is maintained.

When the travel motor 15 is driven, the selector valve 51 and the control valve 54 are switched to the switching positions T and Y, respectively, as described above.

Therefore, the highest pressure of one pump P1 is maintained at the set pressure of the relief valve 53, which is slightly higher than the normal set pressure.

The pump P1 communicates with the travel motor 15 and also communicates with the downstream side of the check valve 56 of the supply passage 55 via the control valve 54.

At this time, when the pilot operation mechanism 3B is simultaneously operated in order to drive the other travel motor 21, the other pump P2 also secures a discharge amount corresponding to the operation amount of the pimit operation mechanism 36.

In this way, when both pumps are driven simultaneously and the vehicle travels straight ahead, the discharged oil from both pumps merges in the supply passage 55, so that the flow rates supplied to the auxiliary travel motors 15, 21 become equal after all. Therefore, the straightness of the vehicle is guaranteed.

When the vehicle is running normally, it does not require much puffing, but when driving on a slope or overcoming an obstacle, the circuit pressure is set slightly higher than the normal set pressure and the power is increased. There are things you have to do.

In such a case, for example, when overcoming an obstacle, if the load pressure exceeds the set pressure of the relief valve 62, this load pressure acts on the check valve 56 as back pressure. In this state, the maximum pressure of the other pump P2 is maintained at the normal set pressure by the relief valve 82, and the maximum pressure of the one pump P1 is
Since the set pressure is maintained at a somewhat higher level by the relief valve 53, the check valve 5B is closed by the pressure on the one pump P1 side.

When check valve 56 closes as described above, supply passage 55
Since the communication between the pump P2 and the drive motor 1 is cut off, the
The circuit connecting 5.21 and pump P1 is independent. Since this independent circuit is controlled by the relief valve 53 that maintains a set pressure higher than the normal set pressure, it is possible to increase the power of the traveling motor.

However, this increase in circuit pressure occurs only in the above-mentioned independent circuit, and in particular, since the other actuators in the other circuit system connected to pump P2 are controlled by the relief valve 62, the circuit pressure is Maintained at set pressure. In other words, since high pressure higher than the normal set pressure does not act on the other actuators mentioned above, they can withstand sufficient pressure without increasing the pressure resistance of the other actuators and the circuit system connected to them, and the durability increases accordingly. will improve.

Further, when the vehicle is in a stopped state, no pressure is introduced into the pilot chamber 51a of the selector valve 51, so the selector valve 51 maintains the normal position S shown in the figure and allows the pump passage 27 to communicate with the relief valve 52. Therefore, the circuit pressure on the pump P1 side is maintained at the normal setting by this relief valve 52.

In addition, as described above, when running with only one pump P1, the running circuit is made independent, so the selector valve 51 and relief valves 52 and 53 that switch the set pressure are required.
It is sufficient to provide only one circuit system.

In addition, in this embodiment, when any one of the switching valves 25, 26, 32 or all of them are switched simultaneously while the travel motor is being driven, the highest pilot pressure at that time acts on the priority valve 57, The priority valve 57 is switched from the normal position F to the switching position G, and communication between the pump passage 27 and the supply passage 55 is cut off.

Therefore, for example, even if the load on the travel motor is lower than the load on the other actuators, the switching valve 25.2
6 or 32, the discharge oil of the other pump P2 reliably flows into the pump P2, and the operating speed of the actuator connected thereto does not become slow.

The pilot chamber 54a of the control valve 54 is connected to the shuttle valve 38 so as to be switched when the traveling motor 15 of one circuit system is driven, but the pilot chamber 54a is connected to the shuttle valve 44 side. May be connected. In other words, when the other traveling motor 21 is driven, the foot control valve 54 may be switched.

However, in the above case, a check valve other than the check valve 56 is provided in the pump passage 27 of one circuit system, and when the discharge amount of one pump P is zero, the other pump P2 must be prevented from being unloaded from the unload valve 60.

The second embodiment shown in FIG. 3 is different from the first embodiment in the relief valve that controls the set pressure of one of the circuit systems, and the other configurations are the same as in the first embodiment. It is.

That is, in this second embodiment, a main relief valve 63 is connected to the pump passage 27, and a selector valve 65 having three positions is connected to the vent passage 64 of the main relief valve 63.

The bipedal selector Palflo 5 is provided with two high port chambers 65a and 85b, one pilot chamber 65a is connected to the shuttle valve 38, and the other pilot chamber e5b is connected to the shuttle valve 38.
is connected to the inflow side of the regulator 48.

Therefore, when any one of the switching valves 18 to 20 and 28 is changed over, the pilot pressure is guided to one of the pilot chambers 85a. Further, when only the travel motor 15 is driven, the pilot pressure at that time is guided to the other pilot chamber 85b.

When pilot pressure is not flowing into any of the pilot chambers, in other words, all the switching valves 18 to 2
When 0 and 29 are held at neutral positions and none of the 7 actuators are driven, the selector valve 65 is held at the right position A shown in the figure by the action of the spring 66.

When the selector valve 65 maintains the right side position A, the vent passage 64 of the main relief valve 62 communicates with the tank T, so the main relief valve 82 substantially functions as an unload valve, and the pump passage Return the hydraulic oil No. 27 to tank T.

When pilot pressure flows into one pilot chamber 85a, the selector valve 65 switches to intermediate position B, and when pilot pressure flows into the other pilot chamber 85b, it switches to left position C. There is.

When the selector valve 65 maintains the intermediate position B, the vent passage 64 communicates with the first pilot relief valve 67, and when it is switched to the left position C, the vent passage 84 communicates with the second pilot relief valve 68. I'm trying to communicate with you.

The first pilot relief valve 67 as described above maintains the normal set pressure, and the second pilot relief valve 68 has a set pressure somewhat higher than the normal set pressure.

When the vent passage 64 communicates with the first pilot relief valve 67, the main relief valve 63
However, when the first pilot relief valve 87 is operated at the normal setting pressure and the vent passage 3o is in communication with the second pilot relief valve 68, the main relief 5t63 is set to a slightly higher second pilot relief valve. It operates at the set pressure of valve 68.

Therefore, the set pressure of the main relief valve 63 is determined depending on which of the pilot relief valves 67 or 68 the vent passage 64 communicates with.

Therefore, when all the switching valves 18 to 20 and 29 are held at the neutral position shown in the figure, no pilot pressure is generated, and therefore, no pressure flows into any pilot chamber of the selector valve 65, and the selector valve 65 does not have any pilot pressure. Valve 65 maintains the illustrated right-hand position A.

When this right side position A is maintained, the main relief valve 63 functions as an unload valve as described above, so that the discharge amount from the pump P is
3 and returns to tank T to ensure standby flow rate.

Further, when any one of the switching valves 18 to 20 and 29 is switched, the pilot pressure flows into the pilot chamber ft5a of the selector valve 65, and switches the selector valve 65 to the intermediate position B.

Therefore, at this time, the vent passage 64 communicates with the first pilot relief valve 67, so the main relief valve 67
3 will operate at normal set pressure.

On the other hand, when the travel motor 15 is driven, its pilot pressure flows into the other pilot chamber e5b, and the selector valve θ5 is switched to the left position C.

When the selector valve 65 is switched to the left position C, the vent passage 64 communicates with the second pilot relief valve 68, so that the set pressure of the main relief valve 63 becomes somewhat higher than the normal set pressure.

Therefore, similarly to the first embodiment, when the vehicle is running, the power is increased compared to when the pressure is set normally.

The third embodiment shown in FIG.
8 and a relief valve 70 with a slightly higher set pressure are connected in parallel to the pump passage 27, and an on-off valve 70 is connected upstream of the relief valve 68 with the normal set pressure. l is connected.

Further, a control valve 72 corresponding to the control valve 54 of the first embodiment is connected to the parallel passage 28 of this one circuit system.

Then, the shuttle valve 75 selects the higher pressure in both pilot chambers of the switching valve 18 connected to the travel motor, and the pilot pressure is set to ``the pilot chamber of the two-legged on-off valve 71''. 1a and the pilot chamber 72a of the control valve 72.

When the on-off valve 71 is held at the normal position shown, the on-off valve 71 is connected to the pump passage 27 and the relief valve 68.
However, when the switching valve 18 is switched,
Communication between the pump passage 27 and the relief valve 68 is cut off.

Furthermore, when the control valve 72 is in the normal position shown in the drawing, it opens the parallel passage 2, but when it is in the switching position on the right side of the drawing, it closes the parallel passage 28 and connects the pump passage 27 to the other circuit system. It communicates with the downstream side of the check valve 56 provided in the supply passage 55 of the switching valve 24.

In addition, each switching valve 18-20,28.
24 to 26.32 are center open type.
When each of these switching valves is in the neutral position shown, the pump P
1 and P2 communicate with tank T via center bypass passages 73,74.

However, when the vehicle is stopped, the switching valve 8 is held at one neutral position, so the on/off valve 71 and the control valve 7 are
2 are held in their normal positions. Therefore, the circuit pressure of one circuit system is controlled by the relief valve 69 to within the normal set pressure.

Further, since the parallel passage remains open for two days, the oil discharged from the pump P is supplied to a predetermined actuator via this parallel passage 28.

When the switching valves 18 and 24 are switched from this state to drive the travel motor, both the on-off valve 71 and the control valve 72 are
It is held in the switching position.

When the control valve 72 is switched in this way, the pump P1 is communicated with the downstream side of the check valve 56 in the supply passage 55, so that the flow rate supplied to both traveling motors becomes equal, and the straight-line performance of the vehicle is guaranteed. Ru.

Further, when the load pressure of the traveling motor becomes lower than the set pressure of the relief valve 62 in order to overcome an obstacle, the discharge pressure of one pump P1 is controlled by the high pressure relief valve 70, and the other pump is Since the discharge pressure of P2 is controlled by the relief 5v62 that maintains the normal set pressure, the pressure downstream of the check valve 56 becomes high. For this purpose, the switching valve 2
4 and the other pump P2 is cut off, and
The circuit connecting one pump P1 and the switching valve 18.24 is independent. Since this independent circuit is controlled by the high-pressure relief valve 70, it is possible to increase the power as in the first embodiment.

In the fourth embodiment shown in FIG. 5, a main relief valve 76 is connected to the pump passage 27 of one circuit system, and
A selector valve 78 is connected to the vent passage 77 of the main relief valve 76. The downstream side of this selector valve 78 is connected to a first pyro-relief valve 79 that maintains a normal set pressure and a second pyro-relief valve 79 that maintains a high set pressure. .

Is this type of selector valve 78 the pilot chamber? 8a, a two-legged shuttle valve 75 similar to the third embodiment.
is connected to.

Further, in the other circuit system, a priority valve 81 similar to that of the first embodiment is connected to the pump passage 30.

In the fifth embodiment shown in FIG. 6, at least the switching valve 18 that controls the travel motor is manually switched, and the switching valve 18 is provided with a control valve 82 that connects one circuit system with the other circuit system. This is a combination of the following.

Therefore, this control valve 82 has three positions corresponding to the switching valve 18, and opens the parallel passage 28 when it is in the neutral position shown. By switching the switching valve 18 connected to the travel motor to either the left or right side, the parallel passage 28 is communicated with the supply passage 55 of the other circuit system. However, in this embodiment, even when the control valve 82 is switched in a two-way manner, the oil discharged from the pump P is supplied to the other switching valve I9.20 via the throttle 83. ing. In other words, in this embodiment, priority is given to driving the traveling morph, while other actuators can also be driven at the same time.

Also, in the pump passage 27 of one pump P1, a main relief valve 76 and a selector valve 7 similar to the fourth embodiment are provided.
A first pilot relief valve 78 maintained at a normal set pressure and a second pilot relief valve 80 set at a slightly higher set pressure are provided.

However, in this embodiment, since the switching valve f1B is manually switched as described above, the pressure of the actuator passage 84, 85 connected to the travel motor 15 is supplied to the pilot chamber 78a of the bipedal selector valve 78. Shuttle valve 8
I select it with 6 and guide it.

Note that the other circuit system in the third to fifth embodiments may be tandem connection, parallel connection, or a combination thereof.

(Configuration of the present invention) The configuration of the present invention is to connect a pump, a travel motor, and other actuators to each of a pair of circuit systems, and to connect the travel motor switching valve of at least one circuit system to the other circuit system. In a control circuit for a construction vehicle, which is located most upstream with respect to the switching valve and is connected to at least one of the other switching valves via a parallel passage, the supply passage for the switching valve for the traveling motor of the other circuit system. A check valve is provided in the parallel passage of one of the circuit systems, and the parallel passage is normally maintained in a communicating state, and is switched by a drive signal of one of the traveling motors to shut off the parallel passage, or A control valve is provided which maintains the communication state through the throttle and communicates the pump passage of the one circuit system with the downstream side of the check 5F, and further drives the travel motor of the one circuit system. When the set pressure is maintained a little higher than the normal set pressure and an actuator other than the above-mentioned travel motor is being driven, - the relief valve that maintains the normal set pressure is connected to the pump passage of one of the above circuit systems. It is characterized by the points connected to it.

(Effects of the present invention) The present invention allows the circuit pressure to be set somewhat higher than the normal set pressure while the vehicle is running. The higher the value, the greater the power it exerts.

Also, while driving, the discharge amounts of the pumps in both circuit systems merge, or only the pump in one circuit system drives both travel motors, so the amount of electricity supplied to both travel motors becomes equal. . In this way, the supply flow rates are equal, so
The straight-line performance of the vehicle is guaranteed.

°゛ Moreover, even if the set pressure of the travel motor circuit system is maintained at a high level as described above, the other seven cutter circuit systems are controlled within the normal setting and constant pressure. Therefore, reliability can be maintained without increasing the pressure resistance of other actuators and their circuit systems.

[Brief explanation of the drawing]

Figure 1 is a conventional circuit diagram, Figure 2 is a circuit diagram of the first embodiment of the present invention, Figure 3 is a main part circuit diagram of the second embodiment, and Figure 4 is a circuit diagram of the main part of the second embodiment.
The figure is a circuit diagram of the third embodiment, FIG. 5 is a circuit diagram of the fourth embodiment, and FIG. 6 is a circuit diagram of the fifth embodiment. P,,P2...Φ pump, 15.21...travel motor, 18~20.24~26.28.32...-switching valve, 27.30-...pump passage, 28.3111...parallel Passage, 52.53.69.70.76... φ relief valve, 54.72.82... Switching valve, 56... Check valve, 83... Throttle. Representative Patent Attorney Nobuyuki Shima

Claims (1)

[Claims] Along with forming a ridgeline between the motor and other actuators,
In a control circuit for a construction vehicle, wherein a switching valve for a travel motor in at least one circuit system is located most upstream with respect to other switching valves, and is connected to at least one of the other switching valves via a parallel passage. , a check valve is provided in the first supply passage of the switching valve for running sheep in the other circuit system, and the parallel passage in the one circuit system is normally in communication with either one of the parallel passages. One running motor,
° is switched by the drive signal to block the parallel path or
Alternatively, while maintaining the communication state through the diaphragm, 1.
A control valve is provided that connects the pump passage of one of the circuit systems to the downstream side of the check valve described above, and when the traveling motor of one of the circuit systems is being driven, the pressure is set slightly higher than the normal set pressure. A control circuit for a construction vehicle comprising a relief valve that maintains a normal set pressure when driving an actuator other than the travel motor, and is connected to a pump passage of one of the circuit systems.