JP2015017684A - Automatic shift switching valve for two-speed hydraulic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic shift switching valve for switching a two-speed hydraulic motor between a high-speed state and a low-speed state.SOLUTION: An automatic shift switching valve 7 includes a hollow two-speed spool 10, a first small-diameter spool C and a second small-diameter spool B fitted to both ends of the two-speed spool 10 movably in the axial direction, and a spring 8 provided between a hollow hole shoulder part 19 of the two-speed spool 10 and the second small-diameter spool B. An external pilot pressure Pis guided to the first small-diameter spool C and a two-speed spool outer end, and a high port pressure Pab of a hydraulic motor 1 to counteract the external pilot pressure Pis guided from a center port A.B into a hollow hole 20 so as to consistently operate on the inside faces of the first small-diameter spool C and the second small-diameter spool B in the second-speed spool 10. Drain ports DR are provided between an A' port and a Pport and between the A.B port and the Pport, respectively.

Description

  The present invention relates to a two-speed hydraulic motor for driving a crawler for construction machinery, and an automatic transmission switching valve for a two-speed hydraulic motor that automatically switches between a low speed and a high speed depending on the magnitude of a load acting on the motor.

Conventionally, there is an automatic shift switching valve of this type of two-speed hydraulic motor described in FIGS. 3 and 4 of Patent Document 1, for example. This switching valve for switching the low speed state and the high speed state of the two-speed motor is in a state of being switched to the high speed side position in response to the pilot pressure from the outside as shown in FIG. When the load acting on the hydraulic motor increases, the pressure of the high pressure port of the hydraulic motor enters the switching valve through the shuttle valve. When this pressure is opposed to the pilot pressure from the outside and becomes greater than a predetermined pressure, the switching valve is switched to the low speed side position, as shown in FIG.
Further, when the load of the hydraulic motor is reduced and the pressure entering the switching valve through the shuttle valve becomes equal to or lower than a predetermined pressure, the switching valve is switched to the high speed position, and the technology shown in FIG. It has been proposed by a person (for example, see Patent Document 1).

Japanese Patent No. 4160862

However, in Patent Document 1, a high pressure is generated at the A ′ port (or B ′ port) that supplies pressure oil while the hydraulic motor is operating. In the case of the prior art, since the A ′ port and the PP port are arranged side by side, an internal leak occurs from the A ′ port to the PP port due to the high pressure generated at the A ′ port.
A. Due to the high pressure generated in the B port, An internal leak also occurs from the B port through the second speed spool to the PP port. When the prior art is applied to a one-pump hydraulic system, the pilot pressure is taken out through the pressure reducing valve, so that the internal pressure of the PP port causes pressure buildup due to the internal leak described above.
For this reason, a relief valve is provided at the PP port to release internal leak to the tank and prevent the PP port pressure from rising above a predetermined value. This relief valve increases the cost of the actual machine.
The present invention has been made in connection with the 2-speed hydraulic motors automatic transmission selector valve according to the applicant, A'ports and P _P port, A. A. and A'port provided drain port DR between B port and the _{P P} port If high pressure is generated in the B port, the internal leakage relief to D _R, aims to pressure P _P port provides an automatic transmission switching valve 2 speed hydraulic motor to prevent rises above a predetermined value .

In order to solve the above-mentioned problems, the present invention provides an automatic variable switching valve for switching between a low speed state and a high speed state of a two-speed hydraulic motor, wherein the switching valve is movable in the axial direction into a large-diameter spool hole closed at both ends in a housing. A hollow two-speed spool fitted to the two-speed spool, and a first small-diameter spool C and a second small-diameter that are fitted to first and second small-diameter spool holes provided at both ends of the two-speed spool so as to be movable in the axial direction. A spool B, and a spring biased in a direction separating the hollow hole shoulder of the second speed spool and the second small diameter spool B, and one of the first small diameter spool C and the second speed spool An external pilot pressure is guided to the outer end of each of the inner surfaces of the first small-diameter spool C and the second small-diameter spool B in the second-speed spool so that the high-pressure port pressure of the hydraulic motor opposed to the external pilot pressure is always applied. To guide the hollow bore than the radial bore located approximately central port provided at the center in the center of the second speed spool of the switching valve so as to act, A'ports and P _P port, A. By providing a drain port DR between B port and the _{P P} port, A'port and A. If high pressure to the B port occurs, escape internal leakage into the drain port DR, pressure P _P port is characterized to prevent the rises above a predetermined value.

The present invention includes an A 'port and an A.P. If the pressure occurs in the B port, escape internal leakage into the drain port DR, pressure P _P port is prevented from rising above a predetermined value. This eliminates the need for a relief valve, thereby reducing the cost of the actual machine.

1 is a hydraulic circuit diagram including a schematic cross-sectional view when an automatic shift switching valve of a two-speed hydraulic motor according to an embodiment of the present invention is in a low speed side position. FIG. 2 is a hydraulic circuit diagram including a schematic cross-sectional view when the switching valve of FIG. 1 is at a high speed side position. 1 is a hydraulic circuit diagram including a schematic cross-sectional view when an automatic shift switching valve of a conventional two-speed hydraulic motor is at a low speed side position. FIG. 4 is a hydraulic circuit diagram including a schematic cross-sectional view when the switching valve of FIG. 3 is at a high speed side position.

Hereinafter, preferred embodiments of an automatic shift switching valve for a two-speed hydraulic motor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a hydraulic circuit diagram including a schematic sectional view when an automatic transmission switching valve of a two-speed hydraulic motor according to an embodiment of the present invention is at a low speed side position, and FIG. 2 is a diagram when the switching valve is at a high speed side position. 1 shows a hydraulic circuit diagram including a schematic cross-sectional view.

  As shown in FIG. 1, an automatic variable switching valve 7 for switching between a low speed state and a high speed state of a two-speed hydraulic motor 1 is a large-diameter spool whose ends are closed by plugs 5 and 6 in a housing 4 partially indicated by a dotted line. A hollow two-speed spool 10 fitted in the hole 15 so as to be movable in the axial direction, and first and second small-diameter spool holes 16 and 17 provided at both ends of the second speed spool 10 are fitted so as to be movable in the axial direction. The first small-diameter spool C and the second small-diameter spool B combined with each other, and a spring 8 that urges the hollow hole shoulder 19 of the second-speed spool 10 and the second small-diameter spool B in a direction of separating.

A pilot pressure chamber 21 is formed at one outer end of each of the first small-diameter spool C and the second-speed spool, the external pilot pressure Pp is guided, and the high-pressure port pressure Pab of the hydraulic motor 1 opposed to the external pilot pressure Pp is always maintained. A central port A.V. provided at approximately the center of the switching valve 7 so as to act on each inner surface of the first small diameter spool C and the second small diameter spool B in the second speed spool 10. The high pressure port pressure Pab of the hydraulic motor 1 is guided from B to a hollow hole 20 through a radial hole 18 located at the center of the second speed spool 10.
2, the pressure Pcp in the control piston 2 communicates from the A ″ port or B ″ port of the switching valve 7 via the shuttle valve 3 to the A ′ port or B ′ port.

In addition, A'port and _{P P} port, and A. By providing the DR port between B port and the _{P P} port, A'port and A. When high pressure is generated at B port,
The internal leakage (dotted arrow X display of FIG. 1 and 2) escape into the drain port DR, pressure P _P port is prevented from rising above a predetermined value.
Thereby, since a relief valve becomes unnecessary, the cost reduction in an actual machine can be aimed at.

  When the high pressure port pressure Pab is higher than the first switching set pressure PHi → LO and the switching valve 7 is in the low speed position, the pressurizing chamber of the speed switching control piston 2 of the hydraulic motor 1 is communicated with the drain port DR. When Pab is lower than the second switching set pressure PLO → Hi and the switching valve 7 is in the high speed position, the pressurizing chamber of the speed switching control piston 2 of the hydraulic motor 1 communicates with the high pressure port pressure Pab of the hydraulic motor 1. Has been.

The automatic transmission switching valve 1 for a two-speed hydraulic motor according to an embodiment of the present invention is basically configured as described above. Next, the operation thereof will be described.
FIG. 1 shows a case where the load high pressure port pressure Pab acting on the hydraulic motor 1 is higher than the first switching set pressure PHi → LO, and the switching valve 7 is in the low speed side position. 12 through the counterbalance valve 11 to the central port A. B flows into the hollow hole 20 from the radial hole 18 of the second-speed spool 10 and presses the spool B in the right direction and the spool C in the left direction as viewed in FIG.

At this time, the A ′ port and A. If high pressure to the B port occurs, escape internal leakage (dotted arrow display in Figures 1 and 2) to the drain port DR, pressure P _P port is prevented from rising above a predetermined value.
In this case, the pressure chamber pressure Pcp of the control piston 2 of the hydraulic motor 1 is communicated from the B ″ port to the DR port of the switching valve 7 via the shuttle valve 3, and the hydraulic motor 1 is connected to the low speed side. Become position.

FIG. 2 shows a case where the high pressure port pressure Pab acting on the hydraulic motor 1 is lower than the second switching set pressure PLO → Hi, and the switching valve 7 is in the high speed side position, and the high pressure port pressure Pab passes through the counter balance valve 11. Central port A.B. B flows into the hollow hole 20 from the radial hole 18 of the second speed spool 10. The 2-speed spool 10 at the high-speed side position is pressed to the right.
At this time, the pressure Pcp in the control piston 2 communicates from the A ″ port or B ″ port of the switching valve 7 to the A ′ port or B ′ port via the shuttle valve 3. As a result, the load pressure P′a or P′b, which is the pressure Pab at the high pressure port of the hydraulic motor 1, flows into the control piston 2 through the switching valve 7 and the shuttle valve 3, and as shown by the one-dot chain line, Is the high speed side position.

1 2-speed hydraulic motor 2 Control piston 3 Shuttle valve 4 Housing 5, 6 Plug 7 Switching valve 8 Spring 10 2-speed spool
15 Large-diameter spool hole 16 First small-diameter spool hole 17 Second small-diameter spool hole 19 Hollow hole shoulder portion of 2-speed spool 20 Hollow hole of 2-speed spool 21 Pilot pressure chamber

Claims (1)

In the automatic variable switching valve that switches between a low speed state and a high speed state of a two-speed hydraulic motor, the switch valve is a hollow two-speed spool that is fitted in a large-diameter spool hole that is closed at both ends in the housing so as to be axially movable. A first small-diameter spool C and a second small-diameter spool B that are fitted in first and second small-diameter spool holes provided at both ends of the second-speed spool so as to be axially movable, and a hollow of the second-speed spool A spring that biases the hole shoulder and the second small-diameter spool B in a separating direction, and an external pilot pressure is applied to one outer end of each of the first small-diameter spool C and the second-speed spool. Of the switching valve so that the high pressure port pressure of the hydraulic motor that opposes the external pilot pressure always acts on the inner surfaces of the first small diameter spool C and the second small diameter spool B in the second speed spool. During ~ To guide the hollow bore than the radial hole located in the center of the second speed spool from the central port provided in, A'port and P _P port, A. By providing a drain port DR between B port and the _{P P} port, A'port and A. If the pressure occurs in the B port, escape internal leakage into the drain port DR, automatic transmission switching valve 2 speed hydraulic motor pressure P _P port is characterized to prevent the rises above a predetermined value.

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