JP2008275057A - Inching valve structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inching valve structure enabling highly reliable control with respect to temperature compensation with simple structure. <P>SOLUTION: In this inching valve structure, a flow rate of hydraulic fluid supplied to a forward clutch or a reverse clutch is controlled by controlling the position of an inching piston 7 based on an electrical control signal. A positioning motor 12 is provided which linearly operates with respect to the axial direction of the inching piston 7 based the control signal. The positioning motor 12 is directly coupled to one end surface on a side opposite to an inching spring abutting surface in the inching piston 7, and the pressing force of an inching spring 13 is adjusted according to the position of the piston set by the positioning motor 12, thereby controlling the flow rate of the hydraulic fluid and regulating pressure of the hydraulic fluid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inching valve structure for a power shift transmission mounted on an industrial vehicle, and more particularly to an inching valve structure that can improve the reliability of temperature compensation with a simple structure.

In industrial vehicles such as forklifts and straddle carriers, and other construction vehicles such as motor graders, self-propelled scrapers (motor scrapers), bulldozers, wheeled tractor excavators (wheel loaders) An inching device that performs inching traveling while performing is provided. The inching device is a device that performs traveling control for moving the vehicle forward or backward at a slow speed, and is used to improve workability in an industrial vehicle, or to smoothly stop, start, or change direction.
In an inching device, inching travel is generally performed by controlling an inching valve by depressing an inching pedal or a brake pedal.

FIG. 4 shows an example of a power shift transmission provided with an inching device (see Patent Document 1). As shown in the figure, the pump 51 sucks up oil from the oil pan 52 and adjusts the pump discharge pressure by the regulator valve 53. The accumulator valve 54 is for smooth engagement of the clutch at the time of shifting.
The inching pedal 55 operates the inching valve 56 to reduce the main hydraulic pressure and enable the clutches 59 and 60 to be released or a half-clutch state. The forward / neutral / reverse switching lever 58 switches the positions by operating the selector valve 57 to send the main hydraulic pressure to the forward clutch 59 or the reverse clutch 60, or by draining the hydraulic pressure of both clutches.

  In the inching valve structure described above, the inching piston position of the inching valve has been conventionally controlled by mechanical force or hydraulic pressure. When the piston position is mechanically controlled, the piston position is mechanically controlled via a cable or a link mechanism by an inching pedal or a brake pedal. On the other hand, when the piston position is controlled by oil pressure, an inching piston and a control oil chamber are provided, and the piston position is controlled by variably setting the oil pressure of the control oil chamber by PWM control of a solenoid valve or the like.

An example of an inching valve structure in which the piston position of the inching valve is controlled by hydraulic control is shown in FIG. 5 (see Patent Document 2). In this inching valve, an inlet port 3, an outlet port 4, and oil discharge ports 5 and 6 for supplying and discharging hydraulic oil are formed in the valve body 2, and an inching piston 7 and a cylinder are formed in the valve body 2. A cylindrical spool valve body 8 is slidably fitted. The spool valve body 8 has an inner spool valve body 10 slidably fitted therein. An inching spring 13 is interposed between the inching piston 7 and one end face of the spool valve body 8, and a counter spring 14 is also interposed between the valve body 2 and the spool valve body 8.
A control oil passage 26 communicates with the control oil chamber 25 partitioned by the valve body 2 and the inching piston 7, and the control oil passage 26 is located in the control oil passage 26 in the middle of the control oil passage 26 in accordance with the depression amount of the inching pedal. An electromagnetic valve 27 for adjusting the hydraulic pressure is interposed. By adjusting the pressure to the inching piston with this electromagnetic valve 27, the spring force of the inching spring 13 is changed, and the hydraulic pressure supplied to the clutch is variably regulated.

  Patent Document 3 (Japanese Unexamined Patent Publication No. 7-232576) discloses an inching device having a simplified structure without impairing the inching traveling function. This is configured to include a proportional electromagnetic selector valve that detects the vehicle traveling direction and the amount of depression of the brake pedal, and controls the direction and flow rate of hydraulic oil based on the detected electrical signal.

No. 5-4606 JP-A-6-129520 JP-A-7-232576

As described above, in the conventional inching device, the piston position of the inching valve is adjusted by mechanical force or hydraulic control as described in Patent Literature 2 and Patent Literature 3 to variably regulate the clutch hydraulic pressure. It was.
However, when the piston position of the inching valve is controlled by a mechanical force, the inching pedal and the inching valve are connected by a cable or a link mechanism. There was a problem that the layout could not be set freely. Further, transmission vibration is transmitted to the inching valve, and it is difficult to maintain pressure regulation accuracy.
In addition, when the piston position of the inching valve is controlled by oil pressure, it is difficult to compensate for temperature changes. That is, since the change of the oil pressure with respect to the temperature change is sensitive, there is a risk that the pressure adjustment accuracy may be lowered or the control may be complicated, such as the need to adjust according to the temperature.
Accordingly, in view of the above-mentioned problems of the prior art, an object of the present invention is to provide an inching valve structure that enables highly reliable control for temperature compensation with a simple structure.

Therefore, in order to solve such a problem, the present invention is configured such that an inching piston and a spool valve body linked to the inching piston are slidably inserted into the valve body, and the inching piston and the spool valve body are interposed between the inching piston and the spool valve body. An inching spring is interposed and a counter spring is interposed between the spool valve body and the valve body, and the inching spring is attached to the spool valve body based on the axial position of the inching piston. An urging force is set, and the flow rate of the hydraulic oil supplied to the forward or reverse clutch is controlled by adjusting the position of the spool valve body to the valve closing side or the valve opening side according to the urging force. Inching valve structure
A positioning motor comprising a motor that operates linearly with respect to the axial direction of the inching piston, or a motor that includes an operating mechanism that operates linearly, and a driven portion of the positioning motor is an inching spring of the inching piston It is directly connected to one end surface opposite to the contact surface, and the position of the inching piston is variably controlled by the positioning motor based on an electrical control signal.

Further, in these inventions, the positioning motor is controlled based on an electrical control signal from an inching opening degree sensor that detects a depression amount of an inching pedal.
According to the present invention, the piston position of the inching valve is controlled by the positioning motor directly connected to the inching piston (including the case where the operation mechanism is interposed), and the flow rate control (pressure regulation) of the hydraulic oil supplied to the clutch is performed. Therefore, the structure can be simplified as compared with the conventional hydraulic type and mechanical type, reliability for temperature compensation is improved, and high-precision and simple control is possible.

  As described above, according to the present invention, since the positioning motor directly connected to the inching piston is used as the driving means of the inching valve, an inching valve having high reliability with respect to temperature compensation is provided with a simple structure. Is possible.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
FIG. 1 is a schematic cross-sectional view showing an inching valve structure according to an embodiment of the present invention, FIG. 2 is a diagram showing a hydraulic circuit of a transmission to which the embodiment of the present invention is applied, and FIG. 3 shows an embodiment of the present invention. It is a schematic sectional drawing which shows an example of the motor to comprise.
This embodiment is suitably applied to industrial vehicles such as forklifts and straddle carriers, etc., or construction engineering machines such as motor graders, self-propelled scrapers (motor scrapers), bulldozers, wheeled tractor excavators (wheel loaders). The present invention relates to an inching valve structure of a power shift transmission mounted on this industrial vehicle.

First, with reference to FIG. 2, the hydraulic circuit of the transmission provided with the inching valve structure according to the present embodiment will be described. This hydraulic circuit is substantially the same as the circuit shown in FIG. Note that this hydraulic circuit is an example, and the inching valve structure of this embodiment can of course be applied to a transmission having other circuits.
As shown in FIG. 2, the hydraulic oil sucked up by the gear pump 31 from the oil sump 30 is supplied to the main regulator valve 33 via the oil passage 40, and the discharge pressure is regulated by the main regulator valve 33. . The hydraulic oil regulated by the main regulator valve 33 is sent to the torque converter via the oil passage 44 and also sent to the inching valve 1 via the oil passage 42. An orifice 43 is provided on the oil passage 42.
Further, a part of the hydraulic oil from the main regulator valve 33 is also sent to the accumulator valve 34 via the oil passage 41. The accumulator valve 34 is for smooth engagement of the clutch at the time of shifting.

The inching valve 1 operates a positioning motor based on an electrical control signal from an unillustrated inching pedal (or brake pedal), and adjusts the position of an inching piston directly connected to the motor, thereby selecting a selector valve 35 (clutch The main hydraulic pressure supplied to 36, 37) is regulated.
The hydraulic oil from the inching valve 1 is sent to the forward clutch 36 or the reverse clutch 37 via the selector valve 35. In this inching valve 1, the hydraulic oil in the engaged state of the clutches 36 and 37 is lowered according to the depression amount of the inching pedal to realize the released or half-clutch state. The specific structure of the inching valve 1 will be described later.
The selector valve 35 is operated by manual operation of a forward / neutral / reverse switching lever (see FIG. 4), and hydraulic oil is sent to the forward clutch circuit 46 or the reverse clutch circuit 47. Here, a description will be given of a power shift transmission of forward 1st speed / reverse 1st speed, but the present embodiment can also be applied to a configuration capable of multi-stage shift such as for forward 2 speed and for reverse 2 speed. In this case, a shift valve (not shown) is provided between the selector valve and the forward / reverse clutches 36, 37, the shift valve is operated by opening / closing the electromagnetic valve, and connected to the forward / reverse clutches 36, 37. 46 and 47 may be switched.

Next, an inching valve structure according to the present embodiment will be described with reference to FIG.
This inching valve structure has a valve body 2, and the valve body 2 includes an inlet port 3 communicating with an upstream oil passage 40, an outlet port 4 communicating with a downstream oil passage 42, and the oil described above. Two oil discharge ports 5 and 6 connected to the reservoir 30 (see FIG. 2) are formed.
The valve body 2 is slidably fitted with an inching piston 7 and a cylindrical spool valve body 8. The inching piston 7 is disposed so as to slide in a cylinder 11 formed on one end side of the valve body 2. An inner spool valve body 10 is provided in the spool valve body 8 in which an annular groove 9 for communicating the inlet port 3 and the outlet port 4 on the outer peripheral surface or communicating the outlet port 4 and the oil discharge port 6 is formed. It is slidably fitted.

Further, in this embodiment, a positioning motor 12 for adjusting the position of the inching piston 7 is connected to one end surface (left end surface in the drawing) of the inching piston 7 facing the cylinder 11 side of the valve body 2.
The positioning motor 12 includes a motor that operates linearly with respect to the axial direction of the inching piston 7 or a motor that includes an operation mechanism that operates linearly.
For example, an ultrasonic motor is preferably used as the high-precision motor that linearly drives. Moreover, as a motor provided with the operation mechanism, for example, a stepping motor or a servo motor is preferably used. This operating mechanism is a mechanism that converts rotational motion into linear motion, and examples thereof include a rack and pinion mechanism and a ball screw mechanism.
The driven portion 12 ′ of the positioning motor 12 operates as if it reciprocates linearly. The driven portion 12 'is directly connected to one end surface (the left end surface in the figure) of the inching piston 7 opposite to the inching spring contact surface.

  The positioning motor 12 generates a linear motion force in the direction of the arrow in the figure, and sets the axial position of the inching piston 7 to a predetermined position. At this time, the depression amount of the inching pedal (or brake pedal) is detected by the inching opening degree sensor, and the positioning motor 12 is driven based on the electrical control signal from the inching opening degree sensor. Thereby, the inching piston 7 connected to the positioning motor 12 is variably controlled to a predetermined position corresponding to the depression amount. FIG. 3 shows an example of the positioning motor 12. As shown in the figure, the motor 12 includes a cylindrical casing 121 having a bottom, and in the casing 121, a brush holder 122 in which a brush is accommodated, and a commutator 123 disposed on the inner peripheral side of the brush. A core 124 having a coil and a magnet 125 installed on the outer peripheral side of the core are disposed. Then, power is supplied to the brush based on a control circuit (not shown), current flows from the brush to the coil of the core 124 via the commutator 123, and the core 124 is rotationally driven by the magnetic flux of the magnet 125. This rotational force is transmitted to a shaft (not shown), and a linear motion is generated from the shaft through the differential mechanism. In order to obtain a predetermined amount of movement by the inching piston 7 using this linear motion, it is performed by controlling the power supply amount by a control circuit that receives an electrical control signal from the inching opening degree sensor.

An inching spring 13 having a predetermined spring force is interposed between the inching piston 7 whose outer peripheral surface faces one oil discharge port 5 and one end surface of the spool valve body 8, and the other end of the valve body 2. A counter spring 14 for biasing the inner spool valve body 10 to the other end surface of the inching piston 7 is also interposed between the side (right side in the drawing) and the inner spool valve body 10.
An oil hole 16 is formed at the center of the inner spool valve body 10 so as to face the pressure regulating oil chamber 15 surrounded by the other end side of the valve body 2 and the other end side of the spool valve body 8. An oil draining oil hole 18 that can communicate with the oil draining port 6 is formed on one end side of the oil hole 16 through an oil hole 17 formed on one end side of the spool valve body 8. 16 is formed with an adjustment oil hole 20 that can communicate with the inlet port 3 or the outlet port 4 through an oil hole 19 facing an annular groove 9 formed in the center of the spool valve body 8. ing.

The operation of the inching valve 1 will be described.
In a state where the driver does not depress the inching pedal, the positioning motor 12 is set so that the inching piston 7 is positioned on the right side of the valve body 2. At this time, the spool valve body 8 is biased to the right side of the valve body 2 together with the inching piston 7, and the inner spool valve body 10 is biased to the other end surface of the inching piston 7 by the spring force of the counter spring 14. Yes. As a result, the inlet port 3 connected to the upstream oil passage 40 and the outlet port 14 connected to the downstream oil passage 42 are in communication with each other via the annular groove 9, and the low line pressure from the downstream oil passage 42 is low. Is supplied to the clutches 36 and 37 via the oil passage 42 and the front selector valve 35 (see FIG. 2), while the pressure adjusting oil chamber 15 has an oil hole 16, an oil hole 18 for oil discharge, and an oil hole 17. It is in a state of communicating with the oil draining port 6 through.

  When the driver depresses the inching pedal from this state, an inching opening degree sensor (not shown) detects the opening degree and converts it into an electrical control signal, which is sent to the positioning motor 12. The positioning motor 12 is driven based on the control signal, and moves the inching piston 7 from the rightmost end toward the left side according to the depression amount. Then, due to the spring force of the inching spring 13 and the counter spring 14, the annular spring receiving portion 21 formed on the other end side of the inner spool valve body 10 contacts the step portion 22 formed on the inner peripheral surface of the spool valve body 8. Until then, the inching piston 7 and the inner spool valve body 10 move. As a result, the pressure adjusting oil chamber 15 is in communication with the inlet port 3 through the oil hole 16, the adjusting oil hole 20, and the oil hole 19, and the low line pressure is also supplied into the pressure adjusting oil chamber 15.

From this point, when the inching pedal is further depressed, the inching piston 7 is further moved to the left by the positioning motor 12, whereby the spool valve body 8 is also moved to the left at the same time. As a result, the spool valve body 8 can close the inlet port 3 according to the change in the depression amount of the inching pedal, and at the same time, the outlet port 4 and the oil discharge port 6 can communicate with each other through the annular groove 9. The hydraulic oil supplied to the clutches 36 and 37 side is discharged through the selector valve 35 and the oil passage 42. In this way, the hydraulic oil is adjusted to a hydraulic pressure proportional to the position of the inching piston 7 by the positioning motor 12 and the spring force of the inching spring 13 according to the depression amount of the inching pedal, so that the clutch is released from the half-clutch state. Control is performed such that 36 and 37 are completely opened.
The configurations of the various spools, springs, oil passages and the like described above are not limited to this, and the positioning motor mechanism according to the present embodiment can be applied to other configurations.

  According to the present embodiment, the piston position of the inching valve 1 is controlled by the positioning motor (including the case where the operation mechanism is interposed) directly connected to the inching piston 7 to control the flow rate of hydraulic oil supplied to the clutch ( Therefore, the structure can be simplified as compared with the conventional hydraulic type and mechanical type, the reliability for temperature compensation is improved, and high-precision and simple control is possible.

It is typical sectional drawing which shows the inching valve structure which concerns on the Example of this invention. It is a figure which shows the hydraulic circuit of the transmission with which the Example of this invention is applied. It is a schematic sectional drawing which shows an example of the motor with which the Example of this invention comprises. It is a control circuit diagram of a conventional transmission. It is typical sectional drawing which shows the conventional inching valve structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inching valve 2 Valve body 3 Inlet port 4 Outlet port 5, 6 Oil discharge port 7 Inching piston 8 Spool valve body 10 Inner spool valve body 11 Cylinder 12 Positioning motor 13 Inching spring 14 Counter spring 33 Main regulator valve 34 Accumulator valve 35 Selector Valve 38 Torque converter

Claims (2)

An inching piston and a spool valve body linked to the inching piston are slidably fitted in the valve body, an inching spring is interposed between the inching piston and the spool valve body, and the spool valve body A counter spring is interposed between the valve main body, and a biasing force to the spool valve body by the inching spring is set based on an axial position of the inching piston, and the spool according to the biasing force is set. In the inching valve structure in which the flow rate of the hydraulic oil supplied to the forward or reverse clutch is controlled by adjusting the position of the valve body to the valve closing side or the valve opening side.
A positioning motor comprising a motor that operates linearly with respect to the axial direction of the inching piston, or a motor that includes an operating mechanism that operates linearly, and a driven portion of the positioning motor is an inching spring of the inching piston An inching valve structure characterized in that it is directly connected to one end surface opposite to the contact surface, and the position of the inching piston is variably controlled by the positioning motor based on an electrical control signal.   2. The inching valve structure according to claim 1, wherein the positioning motor is controlled based on an electrical control signal from an inching opening degree sensor that detects a depression amount of an inching pedal.

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