JPS60175805A - Hydraulic circuit for steering and operational machinery - Google Patents

Abstract

PURPOSE:To provide for more efficient utilization of engine power by forming a demand valve in such a construction as capable of making switching operation according to a pressure difference between the positions before and after a throttle placed in a steering circuit and to the flow supplied to a steering circuit through the demand valve. CONSTITUTION:A demand valve 6 supplying the fluid discharged from a working pump P2 and an auxiliary pump P3 to a working circuit 7 and a steering circuit 1 is formed in such a construction as to allow a switching operation according to a pressure difference between the positions before and after a throttle 12 placed in the steering circuit 1 and also to the flow supplied into the steering circuit 1 through the demand valve 6. By doing so, steering operation under very slow pump revolution will cause the fluid discharged from the working pump P2 and the auxiliary pump P3 to be supplied to the steering circuit 1, and with no steering operation, the flow will be directed to the working circuit 7 thus minimizing the pump capacity and providing for efficient use of the engine power for running.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in tire shovel loaders, dump trucks, motor scrapers, etc., and provides a steering actuator and a working equipment pump using three pumps: a steering pump, an auxiliary pump, and a working equipment pump. The present invention relates to a hydraulic circuit for a steering/working machine that supplies pressure oil to an actuator (1u1).

Prior art This type of hydraulic circuit is a steering pump /','!, as shown in Fig. 1. Hydraulic power steering valve (hereinafter simply referred to as steering valve) AK in 1l-it circuit α! Next, the work equipment pump P2 is connected to the work equipment valve d in the second circuit C, the auxiliary pump Psk demand valve e is connected to m+, the second circuits a and c, and the demand valve e is connected to the first circuit σ. It is switched by the differential pressure before and after the throttle 1, and when the flow rate of the first circuit a is small (when the pump rotation speed is low), the discharge flow rate of the auxiliary pump P8 is supplied to the discharge flow rate 11 circuit α, and a large amount of oil is supplied to the steering valve 6. In addition, when the flow rate in the first circuit a is large (when the pump rotation speed is high), the entire discharge flow rate to the auxiliary pump is supplied to the second circuit C. When a large amount of oil is supplied to the work machine valve d and the flow rate of the first circuit α is medium,
(When the pump rotation speed is medium speed), the discharge flow rate of the auxiliary pump P3 is supplied to the first circuit a for the insufficient amount of oil in the steering, and the remaining discharge flow rate is supplied to the second circuit C. circuit is known.

This hydraulic circuit has the advantage that the absorption torque of the pump can be reduced and the full horsepower of the engine driving the pump can be achieved, and the speed of one working machine does not change even when the steering wheel is operated. However, on the other hand, when the pump rotation speed is extremely low, only the total flow rate of the steering pump Pl and the auxiliary pump P3 flows through the steering valve b.
Since the flow is not supplied to the steering wheel, there is a problem that the flow rate to the steering wheel is insufficient and the steering wheel cannot be operated as desired.

The shaded area in FIG. 2 is the insufficient area.

In FIG. 2, Ql is the steering pump P.

The discharge flow rate of Q2 is the work equipment pump P2 and the auxiliary pump P8.
Total discharge flow rate, Q! is the total pump p, , p, ,
The solid line A is the total discharge flow rate of p, and the solid line A is the required supply flow rate to the steering valve b.

In order to eliminate all of the above-mentioned problems, it is possible to increase the capacity of the auxiliary pump P3, but if you do this, it will not be possible to configure the entire hydraulic circuit with the minimum pump capacity and effectively utilize the engine horsepower for driving. .

Therefore, the present applicant previously filed an application for a complete hydraulic circuit as shown in Figure 3.

In this hydraulic circuit, a steering pump PI'C is connected to the steering circuit 1, and a work equipment pump P2 and an auxiliary pump P3 are connected to the steering circuit 1 through a demand valve 6.
and the working machine circuit 7, and the demand valve 6 is connected to the throttle 91 provided in the steering circuit 1.
When the differential pressure before and after 2 is smaller than a predetermined minimum value, the entire discharge flow rate of the work equipment pump P2 and the auxiliary pump P3 is supplied to the entire steering circuit 1, and when the differential pressure becomes larger than the predetermined minimum value by υ, the work starts. The discharge flow rate of the machine pump P2 and the auxiliary pump 7J is supplied to the entire steering circuit 1 and the work machine circuit 7, and when the differential pressure becomes larger than the maximum value of PJ+-5jL, the discharge flow rate of the work machine pump P2 and the auxiliary pump P8 is is configured to supply the entire amount to the work-like circuit 7.

When the pump rotation speed is extremely low in this hydraulic circuit 6, the entire discharge flow rate of the steering valve L〕0, work equipment pump P5, and auxiliary pump P can be supplied to the steering circuit 1, so that the flow rate to the steering is sufficient. You can operate the steering wheel.

However, in the case of this hydraulic circuit, the work equipment circuit flow rate is
) In the practical range, when the pump rotation speed is low, the work equipment circuit flow rate is low, so the operating speed of the work equipment becomes slow, and when the work equipment is operated independently without steering operation. Since the flow rate shown in the shaded area flows from the working pump P2 and the auxiliary pump P3 to the steering circuit 1, that much flow rate (L: is wasted and results in energy loss).

Purpose of the Invention The pump capacity is kept to a minimum so that it can be effectively used for running at full engine horsepower, and when the pump is rotating at a very low speed, steering operation can supply the necessary flow to the steering circuit, and when the work machine is operated independently, the required flow rate can be supplied to the work machine circuit. Provide a complete hydraulic circuit capable of supplying the required flow rate.

Components of the Invention A demand valve that supplies the discharge fluid of the work equipment pump and the auxiliary pump to the work equipment circuit and the steering circuit is provided in the steering circuit, and the differential pressure before and after the throttle and the flow rate supplied to the steering circuit through the demand valve are When the pump is rotating at an extremely low speed, if the steering is operated, the fluid discharged from the work equipment pump and auxiliary pump is supplied to the steering circuit, and when the steering is not operated, the fluid is supplied to the work equipment circuit.

In FIG. 5 of the embodiment, the steering pump PI is connected to the first circuit (
The steering circuit) 1 is connected to the working machine pump P, and the auxiliary pump P is connected to the second and third circuits 2.3, respectively, and the second and third circuits 2.3 are short-circuited with a check valve 4. Road 5
It is connected and controlled to the working machine circuit 7 and the auxiliary circuit 8 through the demand valve 6'ft.
The work machine circuit 7 is connected to the work machine valve 9 and the auxiliary circuit 8
is connected to the first circuit 1.

The first circuit 1 is connected to and controlled by a steering cylinder 11 via a steering valve io, and is also connected to a throttle valve 1.
2 is provided, and the pressure before and after the throttle p is transmitted to the first and second pressure receiving portions 6α of the demand valve 6 in the first and second pilot paths 13.14.

6h.〇The demand valve 6 is in the first position where it cuts off the second circuit 2 and the working machine circuit 7 and connects the third circuit 3 to the auxiliary circuit 8■
When the differential pressure before and after the throttle 12 reaches a predetermined minimum value, the second circuit 2 and the working machine circuit 7 are connected through the throttle, and the third circuit 3 and the auxiliary circuit 8 are connected directly. When the differential pressure gradually increases, the second communication position H switches the second circuit 2 and the third circuit 3 to the working machine circuit 7 and the auxiliary circuit 8 at the same time. , second circuit 2
and a third communication position IVK which directly communicates with the working machine circuit 7 and communicates with the auxiliary circuit 8 through the full throttle of the m3 circuit 3. When the differential pressure reaches a predetermined maximum value, the second and third communication positions
Circuit 2', 3tl-fifth device V connected to work machine circuit 7
can be switched to and at each position pylon) PV
Pilot boat 1 that supplies pilot fluid to J+5
5 is formed, and this pilot path 15 is connected to the first pressure receiving portion 6α through the entire throttle 17.

Therefore, the demand valve 6 has a differential pressure before and after the throttle 912,
It is switched and controlled to each position depending on the flow rate flowing through the pilot boat 14.

However, when the rotation speed of the engine M is extremely low, the flow rate in the first circuit 1 is small and the differential pressure across the throttle 12 is lower than the predetermined minimum value.
The demand valve 6 is held at the first IRI, and the discharge flow rates of the work equipment pump P2 and the auxiliary pump P are supplied to the first circuit 1.

In this state, if the steering valve 10 is operated, fluid is supplied to the steering cylinder 11, and the supply flow rate is sufficient, allowing quick steering operation.

At this time, the differential pressure before and after the throttle 12 becomes large, and the demand valve 6 is sequentially switched to the 1st, 2nd, and M3 triple positions n, m, and (2), and a flow t commensurate with the steering operation speed is supplied. become.

In addition, if the steering is not operated in the above-mentioned state, the pressure difference before and after the throttle 12 will be extremely small, and a large amount of fluid will be supplied to the auxiliary pipe 8, so a large amount of fluid will also flow into the pilot boat I6, and the pilot boat I6 will have a large amount of fluid. , the demand valve 6 moves to the second and third communication positions 1[1].
, IV and finally becomes the fifth device V, the discharge fluid of the work equipment pump P2 and the auxiliary pump Ps is supplied to the work equipment circuit 7, and the work equipment is supplied with the necessary fluid. This allows the work equipment to operate faster.

In this way, the demand valve 6 is switched to each position depending on the differential pressure before and after the throttle 912 and the flow rate flowing from the demand valve 6 to the auxiliary pipe 8, and supplies the flow rate to the last steering circuit 1 in accordance with the steering operation speed. Since this flow rate is supplied to the work equipment circuit 7, if the steering operation is performed when the pump rotation speed is extremely low, the entire required flow rate can be supplied to the steering circuit 1, and if the steering operation is not performed, the required flow rate can be supplied to the work equipment circuit 7. .

In other words, the flow rate of the work machine circuit 7 is B,
-13, varies based on the total pressure condition (flow rate of auxiliary pipe 8).

Furthermore, when the pump rotation is at a medium rotation speed, the flow rate of the first circuit 1 increases, and the differential pressure before and after the throttle I2 becomes higher than the predetermined minimum value, and the demand valve 6 becomes the first communication position ■, and the work equipment pump The discharge flow rate of the auxiliary pump lJs is supplied to the first circuit 1 and the work equipment circuit 7, and the discharge flow rate of the auxiliary pump lJs is supplied to the first circuit 1 to compensate for the insufficient flow rate of the steering pump P1, and is also supplied to the work 43q valve 9. be done.

Thereafter, as the pump rotation speeds up, the differential pressure before and after the throttle 12 increases, and the demand valve 6 is sequentially switched to the claw 2, third communication position Ill, IV, and the discharge flow rate of the work equipment pump P2 and the auxiliary pump P3 increases. : The flow rate supplied to the first circuit 1 decreases by 11 [1], and the flow rate supplied to the working machine valve 9 increases sequentially.

Furthermore, when the pump rotation reaches a high rotational speed, the flow rate of the first circuit 1 increases to the required supply flow to the steering cylinder 11.
゛The differential pressure before and after the orifice 12 exceeds the predetermined maximum acid value.
Since the demand valve 6 becomes the 27th communication device V, the discharge flow rate of the work equipment pump p2 and the auxiliary pump P3 (
is combined and supplied to the working machine V67.

FIG. 7 shows a specific example of the demand valve, in which the steering valve 10 and the demand valve 6 are disassembled from the valve body 20.

That is, the first and second spools 23 and 24 are fitted into the first and second valve holes 21 and 22 of the valve body 20, and by sliding the first spool 23 from side to side, the flow of water through the throttle 12 is caused. While the fluid is supplied to the steering cylinder 11, the second spool 24 is pushed against the spring 25 by the pressure difference between the left and right pressure receiving parts 6α and 6A in a direction that blocks the boat 26 and the oil hole that becomes the auxiliary pipe 8. The pilot boat 16 (which has an opening in the boat 26 with an aperture 917
A pilot passage 15) is formed, and this pilot boat 16 communicates with the right pressure receiving part 6a, and also with an oil hole which becomes the auxiliary conduit 8 via a restriction J27i.

Effects of the Invention By minimizing the pump capacity, engine horsepower can be effectively utilized for driving, etc.

If the steering operation is performed when the pump rotation speed is extremely low, the discharge fluid of the work equipment pump P2 and the auxiliary pump P3 will be supplied to the steering circuit 1, so the required flow rate can be supplied to the steering circuit.If the steering operation is not performed, the work equipment pump P7, Since the discharge fluid of the auxiliary pump P3 is supplied to the work equipment circuit 7, when the work equipment is operated alone, the required flow 11? − can be supplied.

[Brief explanation of the drawing]

Figure 1 is a conventional hydraulic circuit diagram, Figure 2 is the surface showing its flow-dark characteristics, and Figure 3 is the hydraulic circuit 1 that was previously filed by IiQ.
Fig. 4 shows the surface showing the flow rate characteristics, Fig. 5 shows the hydraulic circuit diagram of an embodiment of the present invention, Fig. 6 shows the fitting showing the flow rate characteristics, and Fig. 7 shows the details of the demand valve. It is a sectional view showing an example. P is steering pump, P2 (a work equipment pump, P
3 is an auxiliary pump, 1 is a steering circuit, 6 is a demand valve, 7 is a work machine circuit, 8 is an auxiliary pipe, and 12 is a throttle. Yamatori [[4 people Komatsu Ltd. Representative attorney Masaaki Yonehara Patent attorney Tadashi Hamamoto [Fig.

Claims (1)

[Claims] The steering circuit 1 includes a steering pump P. and connect and control the auxiliary pump P3 to the work machine pump to the work machine circuit 7 and the auxiliary pipe line 8 connected to the steering circuit 1 via the demand valve 6, and connect the demand valve 6 to the steering circuit 1. The differential pressure before and after the throttle 12 provided in 1 and the demand valve 6 all pass through to the auxiliary pipe 8.
Due to the flow rate supplied to P2, if the steering operation is performed when the pump rotation speed is extremely low, the work equipment pump P2,
A hydraulic circuit for a steering/working machine characterized by having a structure in which the discharge fluid of the auxiliary pump P3 is supplied to the entire steering circuit 1, and is also supplied to the working machine circuit 7 when the steering is not operated.