JP2654953B2 - Control device for 2-speed motor - Google Patents

Description

The present invention relates to a control device for a two-speed motor, and more particularly, to a control device for a two-speed motor that can be used as a hydraulic motor such as a power shovel, a bulldozer or a shovel dozer. .

(B) Conventional technology As a variable hydraulic actuator that can be used as a hydraulic motor that can be changed to high and low second speeds, for example, Japanese Patent Laid-Open
The thing disclosed in No. 7 gazette is known.

The variable hydraulic actuator includes a rotating shaft pivotally attached to a casing, a cylinder block connected to the rotating shaft, a plurality of plungers slidably inserted into a cylinder provided on the cylinder block, and a cylinder. A pair of left and right kidney ports for selectively connecting each cylinder to a high pressure side or a low pressure side with the rotation of the block, shoes held by each plunger, and a swash plate with which the shoes slide. A hydraulic drive member for forming a vertical surface portion and an inclined surface portion on the opposite surface side opposite to the smooth surface with which the shoe contacts, and displacing the tilt angle of the swash plate in opposition to the swash plate. In the motor provided, the hydraulic drive members are disposed at left and right positions corresponding to the pair of kidney ports, and each of the hydraulic drive members is located on the same side through a control valve. It is characterized in that directly or indirectly connected.

(C) Problems to be Solved by the Invention However, in a vehicle driven by a two-speed motor capable of changing between high and low speeds, the frequency in the high speed range is extremely high due to trackability and the like. The driving force may be insufficient when getting over an object. At this time, the operator had to operate the pilot operation valve each time to change the motor capacity.

(D) Means for Solving the Problems Accordingly, the present invention provides a two-speed motor which automatically performs the two-speed switching corresponding to the motor load and enables stable control in order to reduce the load on the operator. It is an object to provide a control device.

In order to achieve this object, the present invention provides a hydraulic drive member for guiding hydraulic oil from a hydraulic pump to a hydraulic motor via a hydraulic drive circuit and controlling a hydraulic drive member for controlling a swash plate tilt angle of the hydraulic motor in a two-speed mode. The pilot pressure is applied only to the small-diameter pressure receiving portion when the second-speed switching valve is moved to the pilot pressure operation side, and the small-diameter valve is moved when the second-speed switching valve is moved in the opposite direction to the pilot pressure operation side. In a control device for a two-speed motor in which pilot pressure acts on both a pressure receiving portion and a large-diameter pressure receiving portion, a pilot pressure from a pilot pump is guided to one of the two-speed switching valves and a parking brake is released to the other. And a drive pressure oil of the hydraulic motor, which passes through a cylinder for use, acts as a pilot pressure.

(E) Operation As described above, according to the present invention, the pilot pressure from the pilot pump is guided to one of the two-speed switching valves,
On the other hand, since the drive pressure oil of the hydraulic motor via the parking brake release cylinder is caused to act as pilot pressure, the switching control of the second speed switching valve can be performed in association with the parking brake release operation, The operator's operation is facilitated, and stability is obtained against a change in driving pressure due to a change in motor capacity.

(F) Embodiment Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings.

1 to 4 are views showing a preferred embodiment of the present invention. The hydraulic motor 1 is selectively connected to any one of the three positions of the counter balance bubble 4 via hydraulic drive circuits 2 and 3, and the counter balance valve 4
It is connected to one of the three positions of the switching control valve 6 via 5a and 5b, and each position of the switching control valve 6 is selectively connected to the pump 7 or the tank 8 at the time of switching.

On the other hand, the swash plate 9 of the hydraulic motor 1 is connected to the rods of the two second-speed pistons 10 and 11, which are hydraulic drive members, and when high pressure is introduced into the piston chamber, the rod extends against the spring 12 so that the swash plate 9 is inclined. The plate 9 is moved counterclockwise in FIG. 1 to control the hydraulic motor 1 at high speed. Conversely, when the piston chamber is connected to the tank side, the rod is compressed by the restoring force of the spring 12, and the swash plate 9 is rotated clockwise. In such a direction that the hydraulic motor 1 is controlled at a low speed.

The piston chambers of the second-speed pistons 10 and 11 are selected through the circuits 13 and 14 to either the left or right position of the second-speed switching valve 15, and when connected to the right position, high pressure is introduced into the piston chamber, and the piston chamber is shifted to the left position. When connected, it communicates with the tank 8 via a circuit.

As shown in FIGS. 2 and 3, the two-speed switching valve 15
Valve hole of body 16 incorporating counterbalance valve 4
It is slidably inserted into 16a. 2-speed switching valve 15
Are formed on the outer periphery with annular grooves 20 and 21 for opening and closing ports (not shown) in passages 18 and 19, respectively. The second speed switching valve 15 is provided with a first spool 27 disposed in the body 16.
And a second spool 28 slidably inserted into the first spool 27 and constantly urged to the left by the spring 17. Is composed of a small diameter portion 27a and a large diameter portion 27b.

Further, a pilot control circuit 29 facing the spring 17 on one side is connected to the second-speed switching valve 15, and this circuit 29 is connected to the pilot operation valve 30 via one of a left low-speed position and a right high-speed position. And selectively connected to the pump 7 or the tank 8.

Reference numeral 29a indicates a pressure reducing valve. In addition, said 2
The speed switching valve 15 is connected to control circuits 31, 32, and the control circuits 31, 32 are directly connected to the hydraulic drive circuits 2, 3. For this reason, the second speed switching valve 15 is a pilot control circuit.
When switching to the right position by the high pressure from 29, the control circuits 31, 32 are connected to the piston chambers of the second-speed pistons 10, 11 via the circuits 13, 14 via the right position.

The parking brake release cylinder 33 is connected to the second speed switching valve 15 via a circuit 34 so that the release pressure of the release cylinder 33 can directly act on the second speed switching valve 15.

 Next, the operation will be described.

In the state shown (pilot pressure 0), the second-speed piston working pressure is released to the tank 8 and the hydraulic motor 1 has a large capacity. In this state, when the pilot operation valve 30 is switched to the second speed position, the pilot pressure acts on the small diameter portion 27a of the first spool 27 of the second speed switching valve 15,
As a result, the pilot pressure overcomes the elastic force of the spring 17 and switches the first spool 27 to the right.

Then, the motor operating pressures M1 and M2 (see FIG. 3) are respectively guided to the second speed pistons 10 and 11 via the second speed switching valve 15, and the hydraulic motor 1 has a small capacity. Here, when the load on the hydraulic motor 1 increases, the drive pressure P1 or P2 increases, and the pressure becomes high. P1 or P2 acts via the counterbalance valve 4 in a chamber 26 defined between the first spool 27 and the second spool 28, and the first spool 27
Moves to the left by the hydraulic pressure corresponding to the pressure receiving area of the spool 28, closes the openings from the working pressures M1, M2 to the second-speed pistons 10, 11, and opens the opening C1 from the second-speed pistons 10, 11 to T1. , C2
open.

On the other hand, the orifice 22 provided on the small diameter portion 27a of the first spool 27 is also closed, and the chamber 23 provided on the outer peripheral side of the small diameter portion 27a of the first spool 27 is opened to the tank 8. As a result, the hydraulic motor 1 has a large capacity and the driving pressure is reduced.
The pilot pressure receiving area of the spool 27 is small, and a large capacity is maintained.

Next, when the load of the hydraulic motor 1 decreases, the driving pressure P1 or P2 decreases, and the hydraulic pressure of the first spool 27 by the pilot pressure overcomes the hydraulic pressure of the first spool 27 by the P1 or P2. Then, the first spool 27 is moved rightward to switch the hydraulic motor 1 to a small capacity.

In the above-described configuration, the present embodiment is different from FIG.
As shown in the figure, the first spool 27 of the second speed switching valve 15
The driving pressure P1 or P2 of the hydraulic motor 1 is applied in a direction opposite to the pilot pressure via the parking brake release cylinder 33.

In this way, by applying the driving pressure P1 or P2 in the direction opposite to the pilot pressure via the parking brake release cylinder 33, the pilot pressure is suppressed low, and the release cylinder is released.
By limiting the peak pressure of the driving pressure generated within the moving time of 33, it is possible to prevent the speed change from the second speed to the first speed due to the moving volume of the brake piston 33a. Control can be performed stably.

(G) Advantage of the Invention By introducing the pilot pressure from the pilot pump to one of the two-speed switching valves and using the drive pressure oil of the hydraulic motor via the cylinder for releasing the parking brake as the pilot pressure, to the other. Since the switching control of the second-speed switching valve can be performed in association with the releasing operation of the parking brake, the operation of the operator becomes easy, and the peak pressure of the driving pressure generated within the moving time of the releasing cylinder is further reduced. The restriction has an excellent effect that stable control can be performed for a change in driving pressure due to a change in motor capacity.

In the present invention, since only the high-pressure side pressure is selected and controlled, a change in the control range due to a change in the back pressure (low-pressure side) can be prevented, and the control point (cut-in pressure, cut-off Out pressure) can be stabilized.

[Brief description of the drawings]

1 is a hydraulic circuit diagram according to one embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a hydraulic motor according to one embodiment of the present invention, and FIG. 3 is a cross-sectional view of FIG. 2 taken along line III-III. FIG. 4 is a hydraulic circuit diagram according to another embodiment of the present invention. 1 to hydraulic motor, 15 to 2 speed switching valve 27 to 1st spool, 27a to small diameter section 27b to large diameter section, 28 to 2nd spool 33 to release cylinder

Claims (1)

(57) [Claims] 1. A hydraulic oil is guided from a hydraulic pump to a hydraulic motor via a hydraulic drive circuit, and a hydraulic drive member for controlling a swash plate tilt angle of the hydraulic motor is driven by switching control of a two-speed switching valve. The pilot pressure acts only on the small-diameter pressure receiving portion when the second-speed switching valve moves to the pilot pressure acting side, and the small-diameter pressure receiving portion and the large-diameter pressure receiving portion move when moved in the direction opposite to the pilot pressure acting side. In the control device for a two-speed motor, the pilot pressure is applied to both of the two-speed switching valve, the pilot pressure from the pilot pump is guided to one of the two-speed switching valves, and the hydraulic pressure is passed to the other through a parking brake release cylinder. A control device for a two-speed motor, wherein the drive pressure oil of the motor acts as pilot pressure.