JP2003262182A - Automatic transmission for two speed type hydraulic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and economical automatic transmission for a two speed type hydraulic motor reduced in the number of part items and facilitated in boring finish work of a housing thereof, without causing a lowering of volume efficiency due to a leak from a shuttle valve when traveling at a low speed. <P>SOLUTION: A two-speed control valve 50 has a two speed spool 2, a middle diameter spool 6 slidably inserted into a middle diameter blind hole 14 provided in one end of the two speed spool 2, and a small diameter spool 15 slidably inserted into a small diameter blind hole 15 provided in the other end of the two speed spool 2. When the pressure of a pilot load pressure port P is at a first set pressure P1 or less (at a position expressed in a figure 1), the pressure is supplied to a cylinder 17 to tilt a cam plate 11 and to rotate the hydraulic motor 10 at a high speed. When the pressure of the load pressure port P exceeds the first pressure P1, a communication passage 24 communicated with the inner end surface of a small diameter spool is communicated with a third drain port DR3 to automatically switch rotation of the two speed type hydraulic motor 10 to the low-speed rotation. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power shovel,
The present invention relates to a two-speed hydraulic motor control circuit for improving a two-speed control performance of a traveling two-speed hydraulic motor used in construction machines such as a shovel dozer. 2. Description of the Related Art A traveling motor such as a power shovel performs a low-speed and high-torque operation during an excavation operation and the like, and can obtain two types of traveling speeds, a high speed and a low speed, so that the moving motor can move at a high speed. A two-speed hydraulic motor is used. The use circuit of this two-speed hydraulic motor having a two-speed control valve and a sequence valve is disclosed in, for example, FIGS. 1 and 2 of JP-A-2001-55968. Although these are improvements, it is difficult to finish the hole in the housing due to the complicated stepped shape of the spool of the two-speed control valve.Also, since the high pressure is always selected by the shuttle valve, the shuttle valve can be operated even at low speed. And the volume efficiency is lowered, and the spring of the two-speed control valve is arranged outside the spool, making it difficult to design a compact design. SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to automatically control a high-speed operation of a two-speed hydraulic motor from a high speed to a low speed or from a low speed to a high speed in accordance with running resistance. In addition, the operability of the operator is improved, the complicated work is improved, the work efficiency is improved, and the number of parts is smaller than that of the conventional technology. Another object of the present invention is to provide an automatic transmission for a two-speed hydraulic motor, which does not leak from the shuttle valve and lower the volumetric efficiency. Therefore, according to the present invention, a two-speed hydraulic motor capable of obtaining two kinds of rotation speeds, high speed and low speed, for the same flow rate supplied from a pump. And a supply / drain line for supplying pump pressure oil to the second-speed hydraulic motor via a directional control valve and discharging return oil from the second-speed hydraulic motor, and selecting a rotation speed of the second-speed hydraulic motor. A two-speed hydraulic motor control having a two-speed control valve configured to supply high-pressure oil to a cylinder that tilts a swash plate of a high-speed hydraulic motor through a shuttle valve and to reduce the speed by discharging the hydraulic oil through a shuttle valve A second speed control valve having a circuit, the second speed spool slidably inserted into the housing, and a medium diameter spool slidably inserted into a medium diameter blind hole provided at one end of the second speed spool. With the medium spool facing the bottom of the medium blind hole And a small-diameter spool slidably inserted into a small-diameter blind hole provided at the other end of the second-speed spool, and a middle-diameter spool outer end face sequentially provided in the housing. One drain port, a first load pressure port, a first load output port, a second drain port, a pilot load pressure port, a third drain port, a second load output port, a second load pressure port, And a pilot pressure port communicating with an outer end face of the small-diameter spool. When the pressure of the pilot load pressure port is equal to or lower than a first set pressure, the second speed spool is at a first position, and the first load Pressure port and primary
Load output port and the second load output port and the second
, And the pilot load pressure port and each of the inner surfaces of the medium-diameter spool and the small-diameter spool are respectively communicated by communication passages provided in a second speed spool. When the pressure at the load pressure port exceeds a first set pressure, the second speed spool moves to a second position, the first and second load pressure ports are closed, and the first and second load pressure ports are closed. The second load output port is in communication with the second and third drain ports, respectively, and the communication passage communicating with the inner surface of the small diameter spool provided in the second speed spool is in communication with the third drain port. And when the pressure at the pilot load pressure port falls below a second set pressure which is lower than the first set pressure, the second speed spool returns to the first position. By providing an automatic transmission device for a secondary speed hydraulic motor, characterized in that it is adapted to move in and solve the problems in the conventional technology. In the automatic transmission for a two-speed hydraulic motor having such a structure, when the pressure of the pilot load pressure port communicating with the supply / discharge line is equal to or lower than the first set pressure, the second speed spool is moved to the first position shown in FIG. And the first load pressure port and the first load output port communicate with the first load output port and the second load pressure port, respectively, and tilt the swash plate of the two-speed hydraulic motor via the shuttle valve. The pressure oil of the supply / discharge line is supplied to the cylinder,
Tilt the swash plate to rotate the two-speed hydraulic motor at high speed. When the load on the two-speed hydraulic motor is small during operation on flat ground, etc., the pressure in the pilot load pressure port is small, so the two-speed control valve does not switch, and the pressure oil in the supply / discharge line continues to be supplied to the cylinder. The hydraulic motor rotates at high speed. [0006] When the load increases and the pressure in the load pressure port exceeds the first set pressure at the time of turning on a slope or the like, the second speed spool moves to the second position, and the first and second load pressures are changed. The ports are each closed and the first and second
Are connected to the second and third drain ports, respectively, and the pressure oil of the cylinder that tilts the swash plate of the two-speed hydraulic motor via the shuttle valve is discharged to the drain line. Automatically switches the rotation of the high-speed hydraulic motor to low-speed rotation. This increases the second-speed hydraulic motor capacity and lowers the pressure at the pilot load pressure port, but since the second set pressure is set lower than the first set pressure, the second-speed control valve remains switched, The two-speed hydraulic motor also remains at low speed. At this time, the second-speed control valve is turned off, and the shuttle valve is turned off, so that there is no leakage from the shuttle valve to lower the volumetric efficiency. When the slope is completed or the direction change is completed, the pressure at the pilot load pressure port further decreases. When the pressure becomes equal to or less than the second set pressure lower than the first set pressure, the pilot pressure communicated with one end of the second speed spool. The second speed spool returns to the first position by the pressure oil of the port, and the first load pressure port and the first load output port, and the second load output port and the second load pressure port respectively The pilot load pressure port and each of the inner surfaces of the medium-diameter spool and the small-diameter spool communicate with each other through communication passages provided in the second-speed spool. And automatically return to high-speed rotation. When the two-speed hydraulic motor is stopped, the load pressure line, that is, the pilot load pressure port becomes the tank pressure, and the second-speed control valve is not switched, so that the pressure oil in the supply / discharge line is supplied to the cylinder. The two-speed control valve of the present invention integrates the sequence valve and the two-speed control valve, and has a smaller number of parts compared to the prior art, making it easier to finish the hole in the housing, and is compact and economical. Next, an embodiment of the present invention will be described. FIG. 1A is a hydraulic circuit diagram of a two-speed hydraulic motor control circuit showing an embodiment of the present invention, in which a two-speed spool is at a first position, a hydraulic motor is rotating at a high speed,
(B) is a schematic sectional view of the second speed control valve at this time. FIG. 2A is a hydraulic circuit diagram of a two-speed hydraulic motor control circuit when the second-speed spool is at the second position and the hydraulic motor is switched from high-speed rotation to low-speed rotation, and FIG. It is a schematic sectional drawing of a speed control valve. FIG. 3 is an explanatory diagram showing a hysteresis characteristic of the switching control pressure of the two-speed hydraulic motor control circuit showing the example of the embodiment of the present invention. In the hydraulic circuit diagram of the two-speed hydraulic motor control circuit according to the embodiment of the present invention, two types of rotation speeds, high speed and low speed, can be obtained with respect to the pump flow rate supplied from a pump (not shown). A two-speed hydraulic motor 10 (hereinafter referred to as a “hydraulic motor”), a switching valve (not shown) for switching the rotation direction of the hydraulic motor, a shock preventer provided between the hydraulic motor 10 and the switching valve when the hydraulic motor stops, and A counterbalance valve 30 that functions to prevent leakage,
Supply / drain line 3 for discharging return oil from the two-speed hydraulic motor,
The two-speed control valve 40 for selecting the rotation speed of the hydraulic motor 10 and the cylinder 17 for tilting the swash plate 11 of the hydraulic motor 10 are connected via a shuttle valve 90. The hydraulic motor 10 is provided with supply / discharge ports 10a and 10b for supplying and discharging pressure oil, and a cylinder 17 having a cylinder piston capable of changing the motor capacity by tilting a swash plate 11 of the hydraulic motor. The cylinder 17 is provided with a cylinder port 17a, and the two-speed control valve 40
Port 17 of cylinder 17 for tilting swash plate 11
Supplying hydraulic oil to a through the shuttle valve 90 reduces the hydraulic motor capacity to increase the speed of the hydraulic motor 10, and increases the hydraulic motor capacity by discharging the hydraulic oil from the cylinder 17 to decrease the hydraulic motor capacity. Has been. Reference numeral 19 denotes a reduction gear connected to the hydraulic motor output shaft, and reference numeral 8 denotes a drain line. The counter balance valve 30 includes left and right inlet ports 30a and 30b connected to left and right outlet ports of a switching valve (not shown) and valve side supply / discharge main lines A and B, left and right load ports 30c and 30d, and a pilot load. Output port 3
It has 0n. The counterbalance valve has throttled pilot lines 34 and 34 connected to the supply and discharge lines 3 and 4, and can be switched to the left and right positions by the pressure oil of the valve side supply and discharge main lines A and B. , 33 to the neutral position. At the neutral position n, the left and right inlet ports 30a, 30b and the left and right load ports 30c, 30d are communicated via check valves 31, 31, and the left and right inlet ports and the output port are communicated via throttles 32, 32. FIG.
Referring to (b), at the left position a, the left inlet port and the left load port are connected via the check valve 31, and at the left position b, the right inlet port and the right load port are connected via the check valve 31,
Each is made to communicate. The supply / discharge ports 10a, 10b of the hydraulic motor 10 and the load ports 30c, 30d of the counter balance valve 30 are connected by supply / discharge lines 3, 4, respectively. As shown in FIG. 1B, the two-speed control valve 40
A second-speed spool 2 slidably inserted into the housing 1, a middle-diameter spool 6 slidably inserted into a middle-diameter blind hole 14 provided at one end of the second-speed spool 2,
A spring 18 for urging the small-diameter blind hole 15 at the other end of the second speed spool 2, and a small-diameter spool 16 slidably inserted into the small-diameter blind hole 15 provided at the other end of the second-speed spool 2. A first drain port DR1 communicating with the outer end face 20 of the medium diameter spool, a first load pressure port A 'connected to the supply / discharge line 3, a first load output port A ″, and a second drain port DR2. , A pilot load pressure port P communicating with the pilot load output port 30n of the counter balance valve 30, a third drain port DR3, a second load output port B ″, and a second load pressure port connected to the supply / discharge line 4. B 'and small-diameter spool outer end face 2
It has a pilot pressure port Pp that is in communication with a pilot pressure source (not shown) that communicates with 1. In operation, the two-speed control valve 40
When the pressure of the pilot load pressure port P communicating with the supply / discharge main lines A and B is equal to or lower than the first set pressure P1, the second speed spool 2 is pushed by the pressure oil of the second pilot pressure port Pp. In the first position shown in FIG. 1, the first load pressure port A 'communicates with the first load output port A ", and the second load output port B' communicates with the second load pressure port B". In addition, the pilot load pressure port P is communicated with the inner side surfaces of the medium diameter spool 6 and the small diameter spool 16 by communication passages 23 and 24 provided in the second speed spool 2 respectively. The hydraulic oil in the supply / discharge lines 3 and 4 is supplied to the cylinder 17 through the second speed control valve 40 and the shuttle valve 90, and the swash plate 11 is tilted to
0 is rotated at high speed. 2-speed hydraulic motor 1 for operation on level ground
When the load to zero is small, the pressure in the pilot load pressure port P is small, so the second speed control valve 40 is not switched,
The two-speed hydraulic motor 10 rotates at high speed as it is. The relationship between the force acting on each spool at the first position of the second speed spool 2 of the second speed control valve 40 shown in FIG. 1B is briefly described as follows. ,
Each pressure receiving area of the medium diameter spool 6 and the small diameter spool 16 is represented by d.
1, d2, the force of the spring 18 is Ps, and the pressure of each port is indicated by the sign of each port. The force FL for pushing the second speed spool 2 to the left is FL = D × Pp, and the second speed spool 2 The force FR that pushes left is FR = P × (d1-
d2) + Ps, and at the position shown in FIG.
FL> FR. When the load increases and the pressure at the load pressure port P exceeds the first set pressure P1 at the time of turning on a slope or the like, the second speed control valve 40 is switched, and the second speed spool 2 is moved to the position shown in FIG. Move to the second position shown in FIG.
Are closed, and the first load output port and the second load output port A ", B" communicate with the second and third drain ports DR2, DR3, respectively. The communication passage 24 communicating with the inner surface of the small-diameter spool provided in the second-speed spool 2 communicates with the third drain port DR3. The communication with the shuttle valve 90 is interrupted at 40, and the shuttle valve 90 is connected to the second and third drain ports D.
The pressure oil of the cylinder 17
And the rotation of the second-speed hydraulic motor 10 is automatically switched to low-speed rotation by discharging from the third drain ports DR2 and DR3. As a result, the capacity of the second-speed hydraulic motor increases and the pressure at the load pressure port P also decreases, but since the second set pressure P2 is set lower than the first set pressure P1, the second-speed control valve 40 is switched. And the two-speed hydraulic motor also remains at a reduced speed. At this time, the second-speed control valve is turned off, and the shuttle valve 90 is also turned off, so that there is no leakage from the shuttle valve 90 to reduce the volumetric efficiency. The relationship between the forces acting on each spool at the second position of the second speed spool 2 of the second speed control valve 40 shown in FIG. 2 (b) will be briefly described. The force FL for pushing in the direction becomes FL = D × Pp, and the force FR for pushing the second speed spool 2 rightward becomes FR = P × d1 + Ps. At the position shown in FIG. 2B, FR> FL. When the slope is completed or the direction is changed, the pressure at the pilot load pressure port further decreases. When the pressure becomes equal to or lower than the second set pressure P2 lower than the first set pressure P1, the pilot load pressure port is communicated with one end of the second speed spool. FIG. 1 shows that the second-speed spool is driven by pressure oil at the pilot pressure port P.
Returning to the first position shown in (b), the first load pressure port A ′ and the first load output port A ″ and the second load output port B ′ and the second load pressure port B ″ respectively The pilot load pressure port P and the inner surfaces of the medium-diameter spool and the small-diameter spool are in communication with communication passages 23 and 24 provided in the second speed spool 2, respectively. Is supplied to the cylinder 17 to reduce the capacity of the hydraulic motor 10 and automatically return to high-speed rotation. The pilot pressure source (not shown) and the pilot pressure port Pp can be switched by an ON-OFF electromagnetic switching valve (not shown).
, The pressure at the pilot pressure port Pp becomes 0,
Since the two-speed control valve does not switch, the two-speed hydraulic motor also remains at low speed. When the second-speed hydraulic motor is stopped, the load pressure line, that is, the pilot load pressure port is at the tank pressure, and the second-speed control valve is not switched, so the pressure oil in the supply / discharge line is supplied to the cylinder. The two-speed control valve of the present invention integrates the sequence valve and the two-speed control valve,
Compared with the prior art, the number of parts is small, the hole finishing of the housing is easy, compact and economical. When returning from the second position of the second speed spool 2 of the second speed control valve 40 shown in FIG. 2B to the first position of the second speed spool 2 shown in FIG. To briefly show the relationship of the acting forces, similarly, the force FL for pushing the second speed spool 2 to the left is FL = D × Pp, and the force FR for pushing the second speed spool 2 to the right is FR = P × d1
+ Ps, FL> FR when returning from the position shown in FIG. 2 (b) to the first position, and the second speed spool 2 does not return to the position shown in FIG. 2 (b) while P2 rises to P1. FIG. 3 shows a hysteresis characteristic of the switching control pressure of the two-speed hydraulic motor control circuit according to the embodiment of the present invention.
It is. According to the present invention, in the high-speed operation of the two-speed hydraulic motor, the pressure oil acting on the inner pressure-receiving surface of the small-diameter spool is turned on and off in accordance with the switching position of the second-speed spool. Hysteresis can be obtained, and the spring force can be made sufficiently small with respect to the hydraulic pressure, enabling reliable control without depending on the spring force. In addition, since there is no restriction on the spring, there is no restriction on the spring, so each spool diameter can be freely selected, and the necessary hysteresis can be obtained, so that smooth switching can be performed. Alternatively, automatic control is performed from a low speed to a high speed to improve the operability of the operator, improve complicated work, and improve work efficiency. By inserting a spring between the bottom of the medium-diameter hole provided at one end of the two-speed spool and the medium-diameter spool, a more compact design is possible, and the sequence valve is integrated with the two-speed control valve compared to the prior art. The present invention provides an automatic transmission for a two-speed hydraulic motor that has a small number of parts, facilitates hole finishing of a housing, is economical, and does not cause a reduction in volumetric efficiency due to leakage from a shuttle valve even at a low speed. Was.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a hydraulic circuit diagram of a two-speed hydraulic motor control circuit showing an embodiment of the present invention, in which a two-speed spool is at a first position and a hydraulic motor rotates at high speed. (B) is a schematic sectional view of the two-speed control valve at this time. FIG. 2A is a hydraulic circuit diagram of a second-speed hydraulic motor control circuit when the second-speed spool is at a second position and the hydraulic motor is switched from high-speed rotation to low-speed rotation, and FIG. FIG. 2 is a schematic sectional view of the second speed control valve of FIG. FIG. 3 is an explanatory diagram showing a hysteresis characteristic of a switching control pressure of a two-speed hydraulic motor control circuit showing an example of an embodiment of the present invention. [Explanation of symbols] 1 housing 2 2nd speed spool 3
4 Supply / discharge line 5 Pilot load pressure line 6
Medium diameter spool 10 Two-speed hydraulic motor 11 Swash plate 16
Small diameter spool 17 Cylinder 17a Cylinder port 40
Two-speed control valves A, B supply / discharge main line A 'first load pressure port A "first load output port B' second load pressure port B" second load output port DR1 first drain port DR2 Second drain port DR3 Third drain port P Pilot load pressure port Pp Pilot pressure port

Continuation of front page    F term (reference) 2D003 AA01 AB01 BA01 BA02 CA02                       DA03                 3H084 AA01 AA45 BB11 CC39 CC47                       CC51 CC70                 3H089 AA20 BB15 BB27 CC09 DB06                       DB09 DB78 DB79 FF07 GG02                       JJ01

Claims (1)

Claims: 1. A two-speed hydraulic motor capable of obtaining two kinds of rotation speeds, high speed and low speed, for the same flow rate supplied from a pump, and to the two-speed hydraulic motor. A supply / discharge line for supplying pump pressure oil via a directional control valve and discharging return oil from the second-speed hydraulic motor, and selecting a rotation speed of the second-speed hydraulic motor by tilting the swash plate of the second-speed hydraulic motor. A two-speed hydraulic motor control circuit having a two-speed control valve having a high-speed by supplying pressure oil to a rotating cylinder via a shuttle valve and a low-speed by discharging the pressurized oil; The control valve includes a second-speed spool slidably inserted into the housing, a middle-diameter spool slidably inserted into a middle-diameter blind hole provided at one end of the second-speed spool, and a middle-diameter blind formed by sliding the middle-diameter spool. A spring that biases against the bottom of the hole, A small-diameter spool slidably inserted into a small-diameter blind hole provided at the other end of the spool, a first drain port communicating with an outer end face of the medium-diameter spool sequentially provided in the housing, and a first load. A pressure port, a first load output port,
A pilot port having a second drain port, a pilot load pressure port, a third drain port, a second load output port, a second load pressure port, and a pilot pressure port communicating with the outer end face of the small diameter spool; When the pressure of the load pressure port is equal to or lower than the first set pressure, the second speed spool is at the first position, and the first load pressure port and the first load output port, and the second load output port and the second load output port are connected to each other. The second load pressure port is in communication with each of the load pressure ports, and the pilot load pressure port and each of the inner surfaces of the medium-diameter spool and the small-diameter spool are in communication with communication passages provided in a second-speed spool, respectively. When the pressure at the pilot load pressure port exceeds a first set pressure, the second speed spool moves to a second position and the first and second speed spools move. The load pressure port is closed, the first and second load output ports communicate with the second and third drain ports, respectively, and an inner surface of the small diameter spool provided on a second speed spool. A communication passage communicating with the third drain port communicates with the third drain port, and further, when the pressure at the pilot load pressure port becomes equal to or lower than a second set pressure lower than the first set pressure, the second speed spool is reset. An automatic transmission for a two-speed hydraulic motor, wherein the automatic transmission is moved to a first position.