JPH0244612Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a steering control circuit that uses a flow rate control valve to supply a constant controlled flow rate to the steering circuit side and to supply surplus flow rate to other working machine circuits.

(Conventional Control Circuit) The conventional control circuit shown in FIG. A small capacity control valve unit b is connected to.

The steering valve mechanism a has a flow control valve F, a switching valve V provided downstream of the flow control valve F, and overload relief valves 13 and 14 connected downstream of the switching valve V as main elements. I have to.

Furthermore, the control valve unit b is
The main elements are a directional switching valve 15 and a gear pump 16. By turning a handle (not shown), the switching valve 15 is switched to the left or right, and the hydraulic oil from the pilot pump 17 is transferred to the gear pump 16. supply And this gear pump 16
The pilot discharges a flow rate proportional to the rotational speed of the handle.

Now, if the handle is rotated to switch the directional control valve 15 to the right position in the figure, the oil discharged from the pilot pump 17 will flow into the gear pump 16 via the directional control valve 15.

At this time, a pilot flow rate proportional to the rotational speed of the handle is discharged from the gear pump 16,
The discharged oil flows into one pilot chamber 19 of the switching valve V via the directional switching valve 15 and one pilot passage 18, and switches the switching valve V to the right position in the drawing.

When the switching valve V is switched as described above, one of the pilot chambers 19 is connected to the communication path 20→variable throttle 2.
1→The other pilot chamber 2 via the communication path 22
3, but at this time the other pilot compartment 2
3 communicates with the tank T via the pilot passage 24 and the directional control valve 15.

The variable throttle 21 is provided on the switching valve V, and its opening degree is adjusted according to the amount of movement of the spool of the switching valve V.

The oil discharged from the gear pump 16 passes through the variable throttle 21 and enters the other pilot chamber 23.
Further, from this pilot chamber 23,
It returns to the tank T via the pilot channel 24.

When the hydraulic oil passes through the variable throttle 21 in this manner, a differential pressure is generated before and after the variable throttle, and the front pressure flows into one pilot chamber 19 as pilot pressure. This pilot pressure is determined in accordance with the discharge amount of the gear pump 16, in other words, in proportion to the rotational speed of the handle. Specify the amount of switching.

When the switching valve V is switched as described above, the power cylinders 10 and 11 operate to deflect the vehicle body and switch its steering direction.

In addition, reference numerals 25 and 26 in the figure are stop valves, which the stopper of the vehicle body comes into contact with just before the limit steering angle of the vehicle body and switches from the normal position shown in the figure to the switching position. I am trying to alleviate this.

Further, the flow rate control valve F has both ends of its spool facing the pilot chambers 27 and 28.

One pilot chamber 27 is connected to the pump passage 1 between the flow rate control valve F and the switching valve V.
The pressure on the upstream side of a fixed throttle 29 provided at 2 is guided.

Further, the other pilot chamber 28 is connected to the switching valve V. When this switching valve V is in the neutral position shown, cutting off communication between the pump passage 12 and the power cylinders 10 and 11, the other pilot chamber 28 communicates with the tank passage 30 and the tank pressure is increased. Become. On the other hand, when the switching valve V is switched to either the left or right side, the other pilot chamber 28 communicates with the downstream side of the fixed throttle 29, and the load pressure of the power cylinders 10, 11 is
It is led to this other pilot chamber 28.

Furthermore, a relief valve 31 is connected to this other pilot chamber 28, and when the pressure in this pilot chamber 28, that is, the load pressure of the power cylinders 10, 11 exceeds a set pressure, this relief valve 31 opens. I try to explain myself. Therefore, this relief valve 31 exhibits the function of controlling the circuit pressure in the other pilot chamber 28 and the power cylinder side to within the set pressure range.

Therefore, when the switching valve V is held at the neutral position shown in the figure, the pressure in one pilot chamber 27 becomes higher than the pressure in the other pilot chamber 28, so the flow control valve F is kept in the position shown in the figure. Switch. In this illustrated switching position, the entire discharge amount of the pump P is supplied to the working machine circuit side via the actuator passage 32.

Then, when the switching valve V is switched to either the left or right side, a flow is generated in the fixed throttle 29, so a pressure difference is generated before and after the fixed throttle 29. The front pressure of this throttle 29 is
The after pressure flows into the pilot chamber 27 on one side, and the afterpressure flows into the pilot chamber 28 on the other side.

In this state, if the discharge amount of the pump P is equal to or less than the control flow rate, the differential pressure before and after the fixed throttle 29 will not become so large.
8 becomes almost equal. for that,
The flow control valve F is set to the right position in the figure by the action of a spring 33 provided in the other pilot chamber 28. In this right-hand position, the entire pump discharge amount flows into the power cylinders 10 and 11.

When the pump discharge rate increases and becomes equal to or higher than the control flow rate, the pressure difference across the fixed throttle 29 increases, and the pressure in one pilot chamber 27 becomes higher than the pressure in the other pilot chamber 28. The flow rate control valve F is set at the position shown, and the controlled flow rate is supplied to the power cylinders 10 and 11, and the surplus flow rate is supplied to the working machine circuit side.

In the conventional circuit as described above, for example, when a steering operation is performed while the other work equipment mentioned above is operating, the pump flow rate is supplied to both, so the flow rate supplied to the work equipment side decreases. So,
The drawback was that the speed changed rapidly.

Further, this conventional control circuit exhibits characteristics as shown in FIG.

That is, when the engine speed is low, the controlled flow rate is greater than the surplus flow rate, but when the engine speed becomes high, the surplus flow rate is conversely greater than the controlled flow rate. As the pump capacity increases, the rate of change in the surplus flow rate increases.

In other words, if the pump capacity is large, the inclination angle of the straight line α in Fig. 2 becomes large, so when the engine speed is low and when the engine speed is high,
The difference in the discharge amount of the pump P increases, and the proportion of the surplus flow rate also changes accordingly.

For this reason, for example, when the switching valve V is switched from a state in which the entire discharge amount is supplied to the work equipment circuit at low rotation speeds to supply a controlled flow rate to the power cylinders 10 and 11, the surplus flow rate becomes extremely large. It becomes less. On the other hand, at high rotational speeds, the rate of decrease in the surplus flow rate decreases.

As described above, in the conventional control circuit, the rate of change in the surplus flow rate between low and high engine speeds is too large, resulting in an extremely large rate of change in the speed of the working machine.

Furthermore, when the engine speed increases, the flow rate control valve F operates when it is desired to increase the flow rate supplied to the power cylinders 10 and 11. However, there was also the drawback that only a constant controlled flow rate could always be supplied.

(Purpose of this invention) This invention is designed to reduce the speed change of the working equipment even if the steering operation is performed while supplying surplus flow to the working equipment circuit, and to increase the engine speed. The object of the present invention is to provide a steering circuit that increases the flow rate supplied to a power cylinder.

(Embodiment of the Present Invention) In describing the embodiment of the present invention shown in FIG. 3, elements common to those of the above-mentioned conventional device will be given the same reference numerals, and detailed explanation thereof will be omitted.

Therefore, in this embodiment, a steering pump _P1 and an auxiliary pump _P2 are provided.

The steering pump P ₁ is directly connected to the switching valve V via the supply passage 34 . Further, since the auxiliary pump _P2 is connected in exactly the same way as the pump P in the conventional circuit, the details thereof will be omitted.

That is, in this embodiment, the pump P of the conventional control circuit described above is replaced with an auxiliary pump _P2 , and a steering pump _P1 is separately added to this auxiliary pump _P2 .

Therefore, when the switching valve V is in the neutral position shown in the figure, the oil discharged from the steering pump _P1 is
It returns directly to the tank T via this switching valve V and the tank passage 30. Furthermore, in this state, the entire amount of oil discharged from the auxiliary pump P ₂ is supplied to the working machine circuit via the actuator passage 32, which is the same as in the conventional case.

Then, when the switching valve V is switched to either the left or right side from the above state, the supply passage 34 and the pump passage 12 merge within this switching valve V, so the discharge oil of both pumps P ₁ and P ₂ merges. The power is then supplied to the power cylinders 10 and 11.

As described above, the discharge oil of both pumps P ₁ and P ₂ join together, but the discharge amount of the auxiliary pump P ₂ is controlled by the flow rate control valve F. In other words, this flow control valve F detects the pressure difference before and after the fixed throttle 29 and performs a predetermined control according to the pressure difference, in the same way as the conventional one.
The excess flow rate is supplied to the 0 and 11 sides, and the surplus flow rate is supplied to the working machine circuit side.

FIG. 4 shows the control characteristics in this embodiment in relation to the engine speed.

In this Fig. 4, the straight line i shows the flow rate characteristics of the steering pump _P1 , and the straight line h shows the flow rate characteristics of the auxiliary pump P1.
Shows the flow characteristics of _P2 . A straight line j parallel to the horizontal axis is the control flow rate specified by the flow rate control valve F, and a curve k is a combination of the characteristics of both pumps.

As is clear from FIG. 4, the discharge amounts of both pumps P ₁ and P ₂ are made proportional to the engine speed.

Thus, when the switching valve V is in the neutral position shown in the figure, the entire discharge amount of the auxiliary pump _P2 , indicated by the straight line h, is supplied to the working machine circuit side. When the switching valve V is switched to the left or right, the auxiliary pump
Of the discharge amount of P ₂ , the control flow rate shown by the straight line j is
It is supplied to the power cylinders 10, 11 together with the entire discharge amount of the steering pump _P1 shown by the straight line i, and the surplus flow is supplied to the working machine circuit side.

Therefore, under the influence of the steering pump _P1 which increases the discharge amount as the engine speed increases, the flow rate supplied to the power cylinders 10, 11 also increases as the engine speed increases.

Furthermore, since the steering pump P ₁ and the auxiliary pump P ₂ are provided as described above, and their discharge amounts are combined and supplied to the power cylinders 10 and 11, the capacity of each pump can be reduced.

For example, if you want to obtain the control characteristics shown by curve k in Figure 4 with one pump, you will have to make the pump's discharge characteristics an extension of the straight line o-k ₁ to obtain the excess flow rate. I can't. However, if the capacity of the pump is increased as described above, the rate of change in the discharge amount of the pump increases between when the engine rotates at low speed and when the engine rotates at high speed. Therefore, the ratio of surplus flow when the engine rotates at low speed becomes extremely small compared to the ratio of surplus flow when the engine rotates at high speed. Therefore, if the power cylinders 10 and 11 are operated when the engine is rotating at low speed, the speed change of the working machine will increase.

But as above the steering pump P ₁
By providing the auxiliary pump P2 and the auxiliary pump _P2 , the capacity of the auxiliary pump that secures the surplus flow rate can be reduced. Since the capacity of the auxiliary pump can be made small, the rate of change in the discharge amount depending on the rotational speed of the engine can be kept small.

Therefore, the rate of change in the surplus flow rate between low-speed rotation and high-speed rotation of the engine can be reduced, and the rate of change in the speed of the working machine can also be kept small accordingly.

(Configuration of the present invention) The configuration of the present invention includes a flow control valve that supplies a constant controlled flow rate to the power cylinder side and supplies the surplus flow rate to other work equipment circuits, and a flow rate control valve that supplies oil from the flow control valve. A steering control circuit including a switching valve leading to a power cylinder, comprising a steering pump and an auxiliary pump, the steering pump being directly connected to the switching valve, and the auxiliary pump being connected to the switching valve via the flow rate control valve. It is characterized by the following points.

(Effects of the present invention) This invention combines the discharge oil of the auxiliary pump with the steering pump and supplies it.
A sufficient supply flow rate to the power cylinder is ensured. In other words, while the work equipment is operating,
Even if hydraulic oil is supplied to the power cylinder, the flow rate supplied to the working machine does not decrease, so changes in the speed of the working machine can be reduced.

Further, by providing the steering pump and the auxiliary pump as described above, the capacity of the auxiliary pump that secures the surplus flow rate can be reduced. Since the capacity of the auxiliary pump can be made small, the rate of change in the discharge amount depending on the rotational speed of the engine can be kept small.

Therefore, the rate of change in the surplus flow rate between low-speed rotation and high-speed rotation of the engine can be reduced, and the rate of change in the speed of the working machine can also be kept small accordingly.

Furthermore, since the steering pump is directly connected to the switching valve without going through the flow control valve, the flow rate supplied to the steering circuit can be increased as the engine speed increases.

[Brief explanation of the drawing]

Figure 1 is a conventional circuit diagram, Figure 2 is a conventional graph showing the relationship between engine speed and pump discharge amount, Figure 3 is a circuit diagram showing an embodiment of this invention, and Figure 4 is a diagram of this invention. 2 is a graph showing the relationship between the engine rotation speed and the pump discharge amount. P ₁ ... Steering pump, P ₂ ... Auxiliary pump, 10, 11 ... Power cylinder, F ... Flow rate control valve, V ... Switching valve.

Claims (1)

[Scope of utility model registration request] a flow rate control valve that supplies a predetermined controlled flow rate to a power cylinder side and supplies a surplus flow rate to another working machine circuit side according to a pressure difference before and after a throttle provided on a downstream side;
In a steering control circuit equipped with a switching valve that guides oil supplied from the flow rate control valve to the power cylinder, the steering pump and an auxiliary pump are provided, the steering pump is directly connected to the switching valve, and the auxiliary pump is connected to the It is connected to a switching valve via a control valve, and is characterized in that the oil supplied from the steering pump and the oil supplied from the auxiliary pump that has passed through the flow rate control valve are combined on the downstream side of the throttle. Steering control circuit.