JPH0217201A - Stepless speed control device for hydraulic motor - Google Patents

Abstract

PURPOSE:To improve responsiveness by connecting a bypass passage going round a stepless speed control valve to a capacity changing means for a hydraulic motor, and interveniently equipping a changeover valve becoming open at a time of lowering in delivery pressure of a pump in the by pass passage. CONSTITUTION:A bypass passage 8 going round a stepless speed control valve 20 is provided between a capacity changing means for a hydraulic motor 1 and a tank 10. This bypass passage 8 is provided with a changeover valve 21 becoming open at a time of lowering in delivery pressure of a pump. Hunting phenomenon, thereby, can be prevented on account of moderate reaction time delay brought by an orifice 18, in usual capacity control. Again, when load becomes lighter than a fixed value, the bypass passage 8 becomes open for being able to raise revolution speed on the hydraulic motor 1 at a stretch, therefore responsibility can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a continuously variable transmission control device for keeping the output of a hydraulic motor constant regardless of the load.

(Prior Art) Some hydraulic motors that drive twin-inch motors have their motor capacity controlled by a circuit as shown in FIG. 4, for example, in order to keep the output constant regardless of load fluctuations.

In this figure, the hydraulic motor 1 is a star-shaped piston motor, and is driven by a hydraulic pump 9 via a directional control valve 7. The hydraulic motor 1 is equipped with an eccentric drum 2 driven by pistons 3 and 4 as shown in FIG. 5 as capacity changing means, and is configured so that the motor capacity changes according to the amount of eccentricity of the eccentric drum 2. . The oil chambers 5 and 6 that drive the pistons 3 and 4 operate according to the discharge pressure of the hydraulic pump 9 511
Hydraulic pump 9 and tank 1 via step-change control valve 20
0.

As shown in FIG. 6, this continuously variable speed control valve 20 applies the discharge pressure of the hydraulic pump 9 to a pilot spool 12 that projects from a spool 11 in the axial direction, and urges this pressure and the spool 1 in the opposite direction. The spool 11 is held at a position balanced with the repulsive force of the spring 13. A boat 14 and an oil chamber 6 communicate with the oil chamber 5 of the eccentric drum 2.
A boat 15 is connected to a boat 16 leading to a tank 10 or a boat 17 leading to a boat 16 through which oil discharged from the hydraulic pump 9 is guided depending on the holding position of the spool 11.

For example, in the state shown in this figure, boat 14 is connected to boat 17,
The boat 15 is connected to the boat 16, and due to the action of the pump discharge pressure to the oil chamber 6 of the eccentric drum 2, the eccentricity of the eccentric drum 2 is small, the hydraulic motor 1 is kept at a small capacity, and rotates at high speed with low torque. are doing. From this state, when the load on the hydraulic motor 1 increases, the discharge pressure of the hydraulic pump 9 also increases, and the spool 11 slides to the left in the figure due to the discharge pressure guided to the pilot spool 12. Eventually, the boat 1
4 is connected to the boat 16, and the boat 15 is connected to the boat 17.

As a result, the discharge pressure acts on the oil chamber 5, and the eccentric drum 2 returns the hydraulic oil in the oil chamber 6 to the tank 10 via the boats 15 and 1.7, and expands its eccentricity as the discharge pressure increases. displacement in the direction. As a result, the capacity of the hydraulic motor 1 increases, and the operating state changes to high torque and low rotation.

In other words, when the load on the hydraulic motor 1 reaches a certain value T, as shown in the graph of FIG. Displacement begins in the direction of eccentric expansion. Then, the load T at which the displacement of the eccentric drum 2 becomes maximum! The eccentric drum 2 expands the amount of eccentricity according to the increase in load, and the hydraulic motor 1
Increase the capacity of. As a result, as long as the load is between T and T2, the hydraulic motor 1 is operated at a constant horsepower regardless of load fluctuations.

Incidentally, the reaction Ic from the load fluctuation of the hydraulic motor 1 to the displacement of the eccentric drum 2! If the jump is short, there is a risk of causing a so-called hunting phenomenon in which the pump capacity changes periodically. Therefore, in order to bring about an appropriate delay in the response of the eccentric drum 2, the boat 17 connected to the tank 10 of the continuously variable speed control valve 20 is An orifice 18 is interposed therein.

(Invention Section M) By the way, when this hydraulic motor 1 is used, for example, as a drive means for a winch that winds up a wire, the rotation of the hydraulic motor 1 should be increased as soon as the wire becomes unloaded to speed up the winding of the wire. However, even in such a case, the hydraulic motor 1 is The problem was that the capacity decreased slowly, and it took extra time to wind up the wire.

The present invention solves the above problems? ! In view of the above, it is an object of the present invention to provide a continuously variable transmission control device that has both a hunting prevention function and a rapid capacity adjustment function when the load becomes lighter than a certain level.

(Means for Achieving the Object) The present invention provides an oil chamber for driving a capacity changing means of a hydraulic motor to a larger capacity side. 111II is selectively connected to the hydraulic pump and the tank via a continuously variable speed control valve that responds to the discharge pressure of the hydraulic pump that drives the hydraulic motor, and a contact part with the tank 17th
In the continuously variable transmission control device for a hydraulic motor with a filter interposed therein, a bypass circuit is provided for directly connecting an oil chamber for driving the capacity changing means of the hydraulic motor toward a larger capacity side to the tank bypassing the seventeenth filter, and This bypass circuit is opened when the pump discharge pressure decreases (it is equipped with a switching valve).

(Function) As the load on the hydraulic motor changes, the discharge pressure of the hydraulic pump changes, and the hydraulic motor changes accordingly! ! ! The oil chamber that drives the F amount changing means toward the large capacity side and the oil chamber that drives it toward the small capacity side are
By selectively connecting the hydraulic pump and the tank, the capacity of the hydraulic motor changes steplessly according to the load. The OLIIS installed in the tank connection section provides resistance to the outflow of hydraulic oil from these oil chambers, thereby slowing down this change in capacity.

On the other hand, when the load on the hydraulic motor becomes lighter and the discharge pressure of the hydraulic pump drops below a certain level, the switching valve opens the bypass passage and switches the oil chamber that drives the volume changing means to the larger capacity side to the 17th oil chamber.
Since it bypasses the filter and communicates directly with the tank, the flow of hydraulic oil is accelerated, the hydraulic motor quickly changes to a small capacity, and immediately shifts to high speed rotation.

(Embodiment) An embodiment of the present invention is shown in FIGS. 1 to 3. It should be noted that the same components as those in the conventional example are given the same numbers and detailed explanations will be omitted.

The continuously variable transmission control device shown in FIG. 1 has a configuration similar to that of the conventional example, but is provided with a bypass circuit 8 that bypasses the continuously variable transmission control valve 20, and a bypass circuit 8 that bypasses the continuously variable transmission control valve 20 is provided in the middle of the bypass circuit 8, which is switched in accordance with the discharge pressure of the hydraulic pump 9. A valve 21 is installed. Switching valve 2
1, as shown in FIG.
25 and the sliding spool 22 connects to the bypass circuit 8.
The boat 24 and the boat 25 that make up the boat 24 and 25 communicate with each other or are cut off from each other. That is, the boat 24 communicates with the boat 14, and the boat 25 bypasses the orifice 18 and directly communicates with the tank 10. The discharge pressure of the hydraulic pump 9 is constantly guided to the boat 23 via the boat 16, and the spool 22
is biased by a spring 26 in a direction opposite to the pump discharge pressure guided to the boat 23, and slides to the left as shown in the figure due to the normal pump discharge pressure, thereby communicating the boats 24 and 25.

Next, the action will be explained.

The hydraulic motor 1 is driven by a hydraulic pump 9, and a continuously variable speed control valve 20 is controlled by an eccentric drum based on the discharge pressure of the hydraulic pump 9 so that a constant horsepower is output under normal loads regardless of load fluctuations. 2 eccentricity is adjusted steplessly by W4.

That is, when the pump discharge pressure increases, the pressure in the oil chamber 5, which is supplied with the pump discharge pressure through the continuously variable speed control valve 20 as shown in FIG. Hydraulic motor 1 by increasing
Decrease the rotation speed.

Furthermore, when the pump discharge pressure decreases, due to the load exerted on the eccentric drum 2 by the hydraulic motor 1 during operation in the direction of eccentricity reduction, the eccentric dome 2 is displaced toward the eccentricity reduction side in accordance with the pressure drop in the oil chamber 5, and the motor The rotation speed of the hydraulic motor 1 is increased by decreasing the capacity.

With this displacement of the eccentric drum 2, hydraulic oil flows through the boats 14 and 17 between the oil chamber 6 and the tank 10.
Oriais 1 installed on boat 17 for this distribution.
8 resists, so that the motor capacity changes gradually with respect to load fluctuations during normal operation. For this reason,
The hunting phenomenon associated with load fluctuations does not occur, and the hydraulic motor 1 is operated stably.

In this state, the switching valve 21 is held by the discharge pressure of the hydraulic pump 9 guided to the boat 23 so that the spool 22 is held to the right of the position shown in FIG. 2 against the spring 26, thereby preventing communication between the boats 24 and 25. is blocked. Therefore, all the hydraulic oil flowing between the oil chamber 6 and the tank 10 passes through the oriice 18.

However, if the load on the hydraulic motor 1 is removed and the discharge pressure of the hydraulic pump 9 drops below a certain level,
In the switching valve 21, due to the pressure drop in the boat 23,
The spool 22, biased by the spring 26, slides to the position shown in FIG. 2, bringing the boats 24 and 25 into communication. Furthermore, in the continuously variable speed control valve 20, the spool 11, which is biased by the spring 13, slides to the position shown in FIG. 2 due to a decrease in the pressure acting on the pilot spool 12.
Boat 15 is connected to boat 16 and boat 14 is connected to boat 17.

As a result, the eccentric drum 2 is displaced in the same direction due to the pump discharge pressure supplied to the oil chamber 6 via the boat 15 and the load exerted by the hydraulic motor 1 in the direction of eccentricity reduction. At this time, the hydraulic oil in the oil chamber 5 flows back to the tank 10 without resistance through the bypass passage 8 opened by the communication between the boats 24 and 25 without going through the orifice 18, so the eccentric drum 2 is quickly displaced. The capacity of the hydraulic motor 1 immediately becomes minimum.

Therefore, the rotational speed of the hydraulic motor 1 becomes maximum, and when driving a winch, for example, the wire is hoisted at high speed at the same time as the load is removed.

Note that when a load above a certain level is applied to the hydraulic motor 1 again, the spool 22 of the switching valve 21 slides due to the pump discharge pressure and cuts off the communication between the boats 24 and 25, so that the normal capacity control of the hydraulic motor 1 is resumed. It is done.

If a notch 27 as shown in FIG. 3 is formed in the spool 22 used for the switching valve 21, communication between the boats 24 and 25 will be established gradually as the pump discharge pressure decreases.
It is also possible to gradually increase the displacement speed of the eccentric drum 2 as the discharge pressure decreases.

(Effects of the Invention) As described above, the continuously variable transmission control device of the present invention allows communication between the oil chamber that drives the capacity changing means of the hydraulic motor toward the large capacity side and the tank through the orifice in the normal control state. Separately, a bypass passage that communicates directly is provided, and a switching valve that opens when the pump discharge pressure decreases is installed in this bypass passage, so that when the load on the hydraulic motor falls below a certain level, the change in volume 1i of the volume 1i change means Hydraulic oil quickly flows between the oil chamber and the tank via the bypass passage, completing the capacity change in a short time.

For this reason, in normal capacity control, the hunting phenomenon is prevented by the moderate reaction time delay brought about by the orifice, and when the load becomes light below a certain level, the rotation of the hydraulic motor is suddenly increased to improve work efficiency. can do well.

[Brief Description of the Drawings] Fig. 1 is a drive circuit diagram of a hydraulic motor showing an embodiment of the present invention, Fig. 2 is a sectional view of a continuously variable transmission control device, and Fig. 3 is a diagram of a spool used in a switching valve. FIG. 7 is a side view of the spool showing another configuration. 4 to 7 show conventional examples, FIG. 4 is a drive circuit diagram of a hydraulic motor, FIG. 5 is a front view of an eccentric drum, and FIG.
The figure is a sectional view of the continuously variable speed control valve, and FIG. 7 is a graph showing the control characteristics of the hydraulic motor. 1... Hydraulic motor, 2... Eccentric drum, 5, 6...
・Oil chamber, 8... Bypass passage, 9... Hydraulic pump,
10...Tank, 11.22...Spool, 12.
...Pilot spool, 13.26...Spring, 14-17.23-25...Boat, 18...Orifice, 20...Continuously variable speed control valve, 21...
switching valve. (Sho 173)

Claims (1)

[Claims] The oil chamber that drives the capacity change means of the hydraulic motor toward the large capacity side and the oil chamber that drives it toward the small capacity side are selectively controlled via a continuously variable speed control valve that responds to the discharge pressure of the hydraulic pump that drives the hydraulic motor. In addition to connecting the hydraulic pump and tank,
In this stepless variable speed control device for a hydraulic motor that has an orifice interposed in the connection part with the tank, a bypass bypass that bypasses the orifice and directly connects the oil chamber that drives the capacity changing means of the hydraulic motor to the larger capacity side. 1. A continuously variable speed control device for a hydraulic motor, comprising a circuit and a switching valve that opens the bypass circuit when the pump discharge pressure decreases.