JPS5943641B2 - Hydraulic drive with stepwise speed conversion function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic drive device that achieves stepwise speed conversion using two hydraulic motors.

As shown in FIG. 1, a conventional hydraulic drive system having three speed stages connects a small-capacity motor 1 and a large-capacity motor 2 connected to a load, such as a winch drum (not shown), to a boost circuit (not shown). ) are hydraulically connected in series or in parallel by means of two directional control valves 4 and 5 connected to the motors via a check valve 3, and in the case of a parallel connection, pressure oil is supplied to one or both of both motors. .

Hereinafter, to simplify the explanation, it is assumed that the pump discharge flow rate is Q) the required flow rate of pressure oil per revolution of the small capacity motor 1 (hereinafter simply referred to as capacity) is q) and the capacity of the large capacity motor 2 is 2q.

Now, when the directional control valve 4 is switched from the functional position B to A, and the directional control valve 5 is switched from the functional position A to B, the pressure oil from the pump (not shown) is diverted to the pipes 6 and 1, and the small The amount of inflow to capacity motor 1 is l/3 ・Q) Large capacity motor 2
The amount of inflow to is 2/3 ・Q.

Therefore, the rotation speed of small capacity motor 1 is Q/3 ・1/q
=Q/3q) The rotation speed of large capacity motor 2 is 2Q/3 ・1
/2q::Q/3q, and the load is driven at low speed. Here, when only the directional control valve 4 is switched from the functional position A to B, all the pressure oil from the pump flows into the large-capacity motor 2, the rotation speed of the large-capacity motor 2 becomes Q/2q, and the load is driven at medium speed. On the other hand, the small capacity motor 1
, 10 and the directional control valves 4 and 5, and power loss occurs due to motor idling. Next, when the directional control valves 4 and 5 are switched from functional position B to A, the pressure oil from the pump flows only into the small capacity motor 1, the rotation speed of the small capacity motor 1 becomes Q/q, and the load becomes high speed. is driven by. In this case, the large capacity motor 2 pumps by receiving the return oil from the small capacity motor 1, and if the rotational speeds of both motors 1 and 2 are the same, the difference in capacity will cause a short circuit. That is, the flow rate Q obtained by subtracting the return flow rate Q from the small capacity motor 1 from the flow rate 2Q flowing to the large capacity motor 2 flows backward from the return pipe 11 via the pipes 12 and 9. As described above, in the conventional device, the small-capacity motor 1 idles at medium speeds, and the large-capacity motor 2 idles at high speeds, both of which cause power loss and cause oil temperature to rise due to the pipe resistance of the reactive flow.

In addition, structurally, the circuit required two large-flow switching valves 4 and 5, and it was necessary to connect a boost pipe to each switching valve. In view of the above points, the present invention provides at least one of the two hydraulic motors with a capacity ratio of 1:1.
2 is a two-speed variable speed motor in which the capacity of the smaller capacity side is the same as the capacity of the other hydraulic motor, and the two hydraulic motors are selectively connected in series and in parallel using one directional control valve. This is intended to improve the performance of this type of hydraulic drive device.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, a conduit 14 leads pressure oil from a pump (not shown) to a directional control valve 16 connected to the small capacity motor 1 via a branch conduit 15. In the functional position A, the directional control valve 16 connects the return line 17 of the small capacity motor 1 to the line 18.
is connected to the two-speed variable speed motor 19 via the conduit 2.
0 to the return line 21 of the two-speed motor 19, and in the functional position B, the return line 17 is connected to line 20 and the branch line 15 to line 18. Reference numeral 22 denotes a directional switching valve for changing the capacity of the two-stage variable speed motor 19, and a pilot pipe line 28 is branched from between a pair of check valves 26 and 27 opposite to each other in a pipe line 25 that communicates with the pipe line 18 and the return pipe line 21. 2
High-speed port 23 and low-speed port 2 of the variable speed motor 19
4.

In addition, in the figure, 29 is the conduit 20 and the boost circuit (not shown)
Check valves interposed between the check valves include a pressure switch 30 for switching the directional control valve 16, and a pressure switch 31 for switching the directional control valve 22.

Next, the operation according to the present invention will be explained.

Here, to simplify the explanation, the capacity ratio of the two-stage variable speed motor 19 is assumed to be 1:2, and the small capacity side thereof has the same capacity as the small capacity motor 1. Now, the directional control valve 22 is switched from the functional position B to A, the pilot pressure is guided to the low speed port 24, and the two-stage variable speed motor 19 is made into a large capacity motor with a capacity of 2q, and then the directional control valve 16 is switched from the functional position A to B. When the small capacity motor 1 and the two-speed variable speed motor 19 are connected in parallel, the inflow amount to the small capacity motor 1 is 1,/3・Ql.
The inflow amount to 9 is 2/3・Q, the rotation speed of small capacity motor 1 is Q/3q, and the rotation speed of 12-speed motor 19 is 2Q/3.
・Motoring together with l/2q=Q/3q, load 32
is driven at low speed. Here, the directional control valve 22 is switched from the functional position A to the functional position B, and the pilot pressure is transferred to the high-speed port 23.
If the two-stage variable speed motor 19 is made into a small capacity motor with a capacity q, both the small capacity motor 1 and the two-stage variable speed motor 19 will be motored with the inflow amount 1/2 and Q1 rotation speed Q/2q, and the load 32 will be Driven at medium speed. Next, directional control valve 1
6 is switched from the functional position B to A and the small capacity motor 1 and the two-speed variable speed motor 19 are connected in series. Two-speed variable speed motor 1 from which the return oil of the capacity motor 1 flows
9 will be pumping. In this case, the capacity of the two-stage variable speed motor 19 is l of the capacity of the large capacity motor 2 of the conventional device.
/2, and since the reactive flow via the short-circuit pipe becomes zero, the power loss due to pumping of the two-stage variable speed motor 19 is much smaller than in the conventional device. In the embodiment shown in FIG. 3, both of the two hydraulic motors 19 and 33 are two-speed variable speed motors, and the melting amount and capacity ratio of both motors are equal. Similar to that of the two-stage variable speed motor 19 in the embodiment shown in the figure, the conduit 14 and the return conduit 17 are communicated with each other by a conduit 36 in which a pair of checker valves 34, 35 facing each other are interposed, and the check valves 34, 3
A pilot pipe 37 that can be branched from between 5 and 5 is connected to a directional control valve 38
It is selectively connected to the high speed port 39 and the low speed port 40 of the two-stage variable speed motor 33.

In this embodiment, the two-stage variable speed motor 33 has a small capacity q
The same effect as that of the embodiment shown in FIG. 2 can be obtained by using the two hydraulic motors 19 and 33.
Both have a large capacity of 2q, and by switching the directional control valve 16 from functional position A to B and connecting the two hydraulic motors 19 and 33 in hydraulic parallel, the second hydraulic motor can be operated without idling the motor. The low speed obtained in the example shown in the figure (
Even slower than Q/3q) (Q/2×1/2q=Q/4
q) speed stage is obtained.

Therefore, the speed can be changed in four stages, including when used with a small capacity. As described above, according to the present invention, idling of the motor occurs only at high speeds, and in this case, the idling motor is switched to a small capacity motor by the two-speed variable speed motor 19, so power loss is minimized, and the two-speed variable speed motor 1
Since the small capacity side of the motor 9 has the same capacity as the small capacity motor 1, the ineffective flow through the short-circuit pipe during idling becomes zero, thereby minimizing power loss and increase in oil temperature due to pipe resistance.

In addition, the three-speed hydraulic first drive device (second
Compared to the same three-speed conventional device (Fig. 1), the one in Figure 1 has two directional control valves that are used to switch the boat of the two-speed motor, and it is smaller, and there is only one boost pipe. This has the effect of helping to make the circuit more compact.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway hydraulic circuit diagram of a conventional device, and FIGS. 2 and 3 are partially cutaway hydraulic circuit diagrams showing an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. In a hydraulic drive device in which the load is changed in several stages by switching the conduits of two hydraulic motors, at least one of the two hydraulic motors has a capacity ratio. 1
: 2 is a two-speed variable speed motor whose capacity on the small capacity side is the same as the capacity of the other hydraulic motor, and the two hydraulic motors are selectively connected in series and parallel using one directional control valve. A hydraulic drive device having a stepwise speed conversion function. 2. A hydraulic drive device having a stepwise speed conversion function according to claim 1, wherein the other hydraulic motor is a two-speed variable speed motor having the same capacity ratio and capacity as the one two-speed variable speed motor.