JPS60115730A - Construction vehicle control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present 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 control circuit for a power shovel.
A travel motor 1, a packet cylinder 2, and a boom cylinder 3 are connected to one circuit system, and a travel motor 4, a swing motor 5, and an arm cylinder 6 are connected to the other circuit system. Closed center type switching valves 7-9 and 10-12 are connected.

One of the above circuit systems includes a variable displacement pump P1.
The switching valves 7 to 9 are connected in parallel to a parallel passage 14 connected to the pump passage 13 of the variable displacement pump P1, and a main relief valve 15 is also connected thereto. Similarly, a variable displacement pump P2 is connected to the other circuit system, and the switching valves 1O to 12 are connected in parallel to the parallel passage 17 connected to the pump passage 16 of the variable displacement pump P2. Along with the main relief valve 1 is connected.

Pilot operation mechanisms 19-21 and 22-24 corresponding to each switching valve are provided in both circuit systems as described above. The pilot operation mechanism generates a pilot pressure proportional to the amount of operation, and switches the switching valve in accordance with this pilot pressure.

The pilot pressure generated in this way is transferred to the shuttle valve 2.
5-29. The highest pressure is selected at 30-34, and the highest pressure is applied to the regulator 34. of the variable displacement pump P, , P, .
35.

Note that reference numeral 37 in the figure is an arm merging control valve, and by switching this merging control valve 37, the discharge oil of the variable displacement pump P1 of one circuit system flows into the arm cylinder 6.

Reference numeral 38 denotes a boom merging control valve, and by switching this merging control valve 38, when the boom cylinder 3 is extended, the oil discharged from the variable displacement pump P2 of the other circuit system flows into the bottom side chamber of the boom cylinder. do.

In such a conventional circuit, each travel motor is connected to an independent variable displacement pump P1. Since the pump is driven by P2, there is a drawback that, for example, if the volumetric efficiencies of the two pumps are different, the straight-line performance of the vehicle will be impaired.

Further, when the travel motor and another actuator are operated simultaneously, the speeds of both travel motors differ due to the influence of the load on the actuator, so there is also a problem that the straight-line performance of the vehicle is impaired in this case as well.

(Objective of the present invention) This invention guarantees the straightness of the vehicle while it is running, and also prevents it from being influenced by other actuators even when other actuators and the travel motor are operated simultaneously. The purpose is to provide a control circuit for construction vehicles that guarantees straight running.

(Embodiment of the present invention) The first embodiment shown in FIG.
In describing this embodiment, only its additional elements will be explained, and common elements will be denoted by the same reference numerals.

A control valve 39 is provided in the parallel passage 14 of one of the circuit systems on the side of the variable displacement pump P1. When the control valve 39 is in the illustrated normal position Mx, it maintains the parallel passage 14 in an open state and allows the pump passage 13 and the parallel passage 14 to communicate with each other.

Since the pilot chamber 39a of the control valve 39 is connected to the shuttle valve 25, pilot pressure flows into the pilot chamber 39a when the travel motor 1 is being driven. When this pilot pressure flows in, the control valve 39 switches to the switching position Y on the right side of the figure, closing the parallel passage 14 and cutting off communication between the pump passage 13 and the switching valves 8, 9, and 37 other than the switching valve 7. At the same time, the pump passage 13 is communicated with the downstream side of the check valve 41 provided in the supply passage 40 of the other circuit system.

A priority valve 42 is provided upstream of the check valve 41.
has been established. This priority valve 42 includes a shuttle valve 33 and
Since it is connected to the shuttle valve 44 which is connected to the pilot line 43 of the boom merging control valve 38, the switching valve 11
．． 12. When any one of 38 is operated, the priority valve 42 is switched from the normal position F to the switching position G.

In addition, numerals 45 and 46 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 regulators 35, 36.

Therefore, when the pilot operating mechanism 19 is operated to drive the traveling motor 1, the pilot pressure flows into the pilot chamber 39a of the control valve 39.
Switch to switching position Y. Therefore, the oil discharged from this one pump P1 flows into the traveling motor I, and also flows into the downstream side of the check valve 41 of the supply passage 40 via the control valve 39. At this time, when the pilot operation mechanism 22 is simultaneously operated to drive the other traveling morph 4, the other pump P2 also ensures a discharge amount corresponding to the operation amount of the pilot operation mechanism 22.

In this case, since both pumps communicate with each other, even if their discharge amounts are different, the discharge amounts are averaged and the flow rate supplied to the travel motor 1.4 is equal. Become. Therefore, even if the discharge amounts of the two pumps are different, the straight-line performance of the vehicle is guaranteed.

On the other hand, when the travel motors 1 and 4 are driven and the switching valves 11, 12, 38, etc. of the other circuit system are operated at the same time, the load on the actuator connected to these switching valves is greater than the load on the travel motor 1.4. Even if the vehicle speed is low, the straight-line performance of the vehicle is guaranteed. That is, in the above case, the check valve 41 cuts off communication between the switching valve IO and the other pump P2, and the re-travel motor 1.4 and the other pump P2 are disconnected from each other.
The circuit connecting 1 becomes independent. Therefore, the flow rates supplied to the re-travel motor 1.4 become equal, and the straight-line performance of the vehicle is guaranteed.

Furthermore, when the switching valve 7 is switched to drive only one drive motor 1, even if the control valve 39 is switched, since the check valve 41 is provided, one pump P
1 of discharged oil is not unloaded from the unload valve 46 to the tank T.

Furthermore, while the travel motor is being driven, the swing motor 5
Or when driving the arm cylinders 6 at the same time,
At that time, the highest pi o, 1 pressure in the other circuit system acts on the priority valve 42, switches the fr prior valve 42 to the normal position F or to the switching position G, and disconnects the pump passage 13 and the supply passage 40. Cut off.

Therefore, for example, even if the load on the travel motor is lower than the load on other actuators in the other circuit system, the oil discharged from the other pump P2 will reliably flow into the swing motor 5 or the arm cylinder 6. The operating speed of the actuator no longer becomes slow.

In addition, as mentioned above, when the priority valve 42 drives the travel motor and simultaneously operates the actuator of the other circuit system, the discharge oil of the other pump P2 is preferentially applied to the actuator of the other circuit system. The purpose is to ensure that the Therefore, this priority valve may be provided with a throttle at the switching position G.

This throttle also includes a relief valve.

Further, the pilot chamber 39a of the control valve 39 is connected to the shuttle valve 25 so as to be switched when the traveling motor 1 of one circuit system is driven, but the pilot chamber 39a is connected to the shuttle valve 30 side. May be connected. In other words, when the other travel motor 4 is driven, this control valve 39
may be switched.

However, in the case of "-", the check valve 41 is provided in the pump passage 13 etc. of one circuit system, and one pump P,
When the discharge amount of the pump P2 is zero, it is necessary to prevent the discharge oil of the other pump P2 from being unloaded from the unload valve 45.

In the second embodiment shown in FIG. 3, the pilot chamber 39a of the control valve 39 is connected to a shuttle valve 49 provided between the supply passages 47 and 48 of the travel motor 1. This is the same as the first embodiment.

In the third embodiment shown in FIG. 4, the control valve 39 is in the third position and is mechanically connected to the switching valve 7 that controls the travel motor 1.

Therefore, in this embodiment, when the switching valve 7 is switched, the control valve 38 is also switched in conjunction with the switching.

However, the function of this control valve 39 is the same as in the first and second embodiments.

The fourth embodiment shown in FIG. 5 has a different configuration of the control valve 39, and at the switching position Y, the pump P is also connected to the parallel passage 14 side via the throttle 50.

It is designed to supply discharge oil of

That is, in each of the embodiments described above, when the control valve 39 is switched, oil is no longer supplied to the other actuators in this one circuit system, but in this embodiment, the throttle 50
By providing oil, it is possible to preferentially supply oil to the travel motor 1.4 and to supply the surplus oil to the other actuators.

(Structure of the present invention) This first invention provides for each of a pair of circuit systems to
A switching valve that connects the pump, a travel motor, and other actuators and controls these actuators is connected to the pump passage via a parallel passage, and a switching valve that controls the travel motor of at least one circuit system; In the control circuit of a construction vehicle, which is located in the first stream compared to other switching valves, the switching valve that controls the travel motor is located in the first stream.
A control valve is connected to the parallel passage of one circuit system located in the first flow, and when this control valve is in the normal position, each switching valve in one circuit system is communicated with the pump passage, and either one When the drive motor is driven and the control valve is switched to the switching position, the connection between the switching valves other than the switching valve connected to the drive motor in one of the circuit systems and the pump passage is cut off, or They are communicated through a throttle, and the pump passage is communicated with the inflow side of a switching valve that controls a travel motor in the other circuit system, while preventing oil discharged from the pump from flowing into the tank. It is characterized by the provision of a check valve.

In addition to the first invention, a second invention provides, in addition to the first invention, on the inflow side of the switching valve that controls the traveling motor of the other circuit system, the pump and the switching valve are connected in a free state at a normal position. A priority valve is provided, and when a switching valve other than the switching valve connected to the traveling motor in the other circuit system is operated, this priority valve is switched to the switching position, and communication between the pump and the switching valve of the traveling motor is established. The feature is that the two are communicated through a diaphragm or a diaphragm.

(Effects of the present invention) According to the first invention, the variable displacement pumps in both circuit systems communicate with each other and their discharge amounts are averaged, so even if the volumetric efficiencies of both pumps are different, Since the flow rates supplied to the travel motors are equal, straight-line travel is guaranteed, and even if other actuators are driven at the same time, the travel motors are not affected by the other actuators.

According to the second invention, since the priority valve is provided in the other circuit system, the actuator of the other circuit system is
Yuzu can be reliably supplied regardless of the load conditions of the travel motor.

[Brief explanation of the drawing]

Figure 1 is a conventional circuit diagram, Figure 2 is a circuit diagram of a first embodiment of the present invention, Figure 3 is a circuit diagram of a second embodiment, and Figure 4 is a circuit diagram of a third embodiment. , FIG. 5 is a partial circuit diagram of the fourth embodiment. ■, 4...Travel motor, 7-12...Switching valve, Pl
, P2Φ/φ variable displacement pump, 13.1 [i-Pump passage, 14.17... Parallel passage, 19-24 Competition pilot operation mechanism, 39-... Control valve, 40...
- Supply passage, 41... Check valve, 42... Priority valve, 50... Throttle. Representative Patent Attorney Nobuyuki 1lIl

Claims (2)

[Claims] (1) A pump, a travel motor, and other actuators are connected to each of the pair of circuit systems, and a switching valve for controlling these actuators is connected to the pump passage via a parallel passage, so that at least one circuit In a control circuit for a construction vehicle in which a switching valve for controlling a running motor in a system is located most upstream with respect to other switching valves,
A control valve is connected to the parallel passage of one circuit system in which the switching valve that controls the travel motor is located at the most upstream position, and when this control valve is in the normal position, each switching valve in one circuit system is pumped. When the control valve is switched to the switching position by driving one of the travel motors, the switching valve other than the switching valve connected to the travel motor in one of the circuit systems and the pump passage At the same time, the pump passage is communicated with the inflow side of the switching valve that controls the travel motor in the other circuit system, while the discharge oil of the pump is A construction vehicle control circuit equipped with a check valve to prevent water from flowing into the tank. (2) A pump, a travel motor, and other actuators are connected to each of the pair of circuit systems, and a switching valve for controlling these actuators is connected to the pump passage via a parallel passage, so that at least one circuit In a control circuit for a construction vehicle in which a switching valve for controlling a running motor in a system is located most upstream with respect to other switching valves,
A control valve is connected to the parallel passage of one circuit system in which the switching valve that controls the travel motor is located at the most upstream position, and when this control valve is in the normal position, each switching valve in one circuit system is connected to the pump passage. When the control valve is switched to the switching position by driving one of the travel motors, the switching valves other than the switching valve connected to the travel motor in one of the circuit systems and the pump passage At the same time, the pump passage is communicated with the inflow side of the switching valve that controls the travel motor in the other circuit system, while the pump discharge oil is connected to the tank. A check valve is provided on the inflow side of the switching valve that controls the traveling motor of the other circuit system, and the pump and the switching valve are in free communication at the normal position. A priority valve is provided, and when a switching valve other than the switching valve connected to the traveling motor of the other circuit system described in -1- is operated, this priority valve is switched to the switching position, and the switching valve of the pump and the traveling motor is switched to the switching position. A control circuit for a construction vehicle configured to either cut off communication or allow communication between the two through an aperture.