KR20180090015A - Hydro Static Transmission and Swash plate controlling methods of Hydro Static Transmission - Google Patents

Abstract

Disclosed are a hydrostatic continuously variable transmission including a variable-capacity hydraulic pump driven by power of a power source (engine) and a variable-capacity hydraulic motor driven in conjunction with a hydraulic pump and representing variable rotational speed according to a discharge flow rate of the hydraulic pump, and a method for controlling a swash plate of a variable-capacity hydraulic motor of the hydro static continuously variable transmission, capable of generating an appropriate output according to load conditions depending on driving environment or working environment. In the hydrostatic continuously variable transmission according to one aspect of the present invention, the hydraulic motor is a variable-capacity hydraulic motor in which the angle of a swash plate to a motor shaft is automatically variable according to the load on the motor shaft. The hydrostatic continuously variable transmission includes: an actuator part installed adjacent to a rear portion of a swash plate inside the hydraulic motor and operated by hydraulic pressure to adjust the angle of the swash plate with respect to the motor shaft; and a swash plate control valve which is installed at one side of a housing of the hydraulic motor and is switched such that oil is supplied to the actuator part or discharged from the actuator part in accordance with a change in the pressure of the oil supplied to the inside of the hydraulic motor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a hydrostatic stepless transmission, and more particularly, to a hydrostatic stepless transmission and a hydrostatic stepless transmission,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable capacity hydraulic motor swash plate angle control method for a constant pressure transmission and a constant pressure hydraulic transmission of a constant oil hydraulic type, and more particularly to a constant pressure hydraulic transmission and a constant pressure hydraulic transmission including a variable displacement hydraulic pump and a variable displacement hydraulic motor, The present invention relates to a variable displacement hydraulic motor swash plate angle control method.

Hydraulic Static Transmission (hereinafter referred to as "HST") is mainly used as a speed change device for a work vehicle requiring frequent shifting such as a small snow removal equipment, a weeding machine, a tractor, and a combine . The HST generally includes one variable displacement hydraulic pump and one or more constant capacity hydraulic motors, and consists of a check valve, a relief valve, and the like.

The HST, which is composed of the variable displacement hydraulic pump and the constant displacement hydraulic motor, is driven by the power source, for example, the rotational force output from the engine, to suck the hydraulic fluid and discharge it to the hydraulic motor side at a predetermined pressure. And the inner power transmission element is rotated by the rotational force to drive the wheel.

The rotational speed and the direction of the motor shaft of the hydraulic motor are determined by the flow rate of the variable displacement hydraulic pump and the magnitude of the circuit pressure load. To this end, the variable displacement hydraulic pump includes a cylinder block having a plurality of pistons, And a pump shaft for rotating the cylinder block, so that the swirl angle of the swash plate can be adjusted to adjust the delivery flow rate and pressure.

For example, when the swash plate gyration angle is '0' (the swash plate is disposed perpendicularly to the pump shaft), there is no discharge flow rate of the hydraulic pump, so that the swash plate is in a neutral state. When the swash plate gyration angle is inclined at a predetermined angle The hydraulic motor outputs power in the forward direction by the suction / discharge flow rate of the hydraulic pump determined in proportion to the angle. In the opposite case, the discharge direction of the flow rate is changed and the rotation direction of the hydraulic motor is also changed.

A hydraulic swash plate angle adjusting means for rotating the trunnion shaft for adjusting the swash plate angle of the swash plate of the hydraulic pump, for example, a hydraulic cylinder for speed change, is applied, and a control means such as a solenoid valve To control the operation of the hydraulic cylinder to control the angle of inclination of the swash plate.

The operation of the control means operated by the electric signal is controlled by the output signal of the ECU based on the detection information of the variable-speed-type position detecting means for detecting the operating position (or the operating amount) of the speed change operating mechanism, , The flow rate of the operating fluid supplied to the swash plate angle adjusting means is controlled through the control means in accordance with the control of the ECU, thereby adjusting the swash plate angle of the swash plate.

When the speed of the power source (engine) is set to a low speed and the shift angle is adjusted by adjusting the hydraulic angle of the swash plate of the hydraulic pump, a large load may be applied to the power source although the speed ratio, Stall is likely to occur. Careful operation of the shift operating mechanism is required to avoid occurrence of engine stall.

Particularly, in the case of starting up the vehicle in a state where the work vehicle is operated with a slope of an uphill road with a large load or a work device connected to the work equipment, or when the vehicle is started at a stop, the engine stall may occur even with small operation mistakes. And the operator must directly perform a separate downshift operation in accordance with the load situation. Thus, conventionally, there is a limit to implement an appropriate shift according to various situations using only the hydraulic pump.

Japanese Patent Laid-Open No. 7-023610 Japanese Patent Laid-Open No. 2006-70943

SUMMARY OF THE INVENTION It is an object of the present invention to provide a variable displacement hydraulic motor in which a swivel angle is automatically changed according to a load size, Or a variable capacity hydraulic motor swash plate angle control method of a hydrostatic type continuously variable transmission and a hydrostatic type variable speed transmission capable of producing an appropriate output according to various load conditions depending on the working environment.

According to an aspect of the present invention,

A hydrostatic type transmission system comprising a variable displacement hydraulic pump driven by a power source of an engine and a hydraulic motor driven in conjunction with the hydraulic pump and having a variable rotational speed according to a discharge flow rate of the hydraulic pump,

Wherein the hydraulic motor is a variable displacement hydraulic motor in which the angle of the swash plate with respect to the motor shaft is automatically variable according to the load on the motor shaft,

An actuator unit installed to be connected to the swash plate rear portion inside the hydraulic motor and operated by hydraulic pressure to adjust the angle of the swash plate with respect to the motor shaft; And

And a swash plate control valve installed at one side of the housing of the hydraulic motor and configured such that the oil is supplied to the actuator portion according to the pressure fluctuation of the oil supplied to the inside or the oil passage is switched so as to discharge the oil inside the actuator portion, Hydraulic stepless speed change transmission is provided.

Wherein the actuator portion includes: a piston reciprocating in a pressure chamber behind the swash plate; And a piston shoe coupled to the piston and contacting the surface of the swash plate facing the piston.

In the swash plate control valve, a volume variable internal pressure chamber (C) is formed at a central portion by a stationary piston supported by the end cap, one or more grooves are formed in the circumferential direction at an outer surface portion, A control spool which moves in the axial direction relative to the fixed piston in response to a pressure variation of the oil acting on the fixed piston; A return spring for generating a restoring force against the pressure of the oil acting on the internal pressure chamber (C); And a fixed sleeve installed between the control spool and the valve body and having a plurality of holes corresponding to the grooves, wherein the oil pressure acting on the inner pressure chamber (C) The axial position of the control spool is determined and the connecting position of the groove and the hole and the flow passage area between the groove and the hole are variable.

At this time, if the pressure of oil acting on the internal pressure chamber C is larger than the reaction force of the return spring, the control spool is moved to one side so as to form a drain passage connecting the actuator portion to the oil tank side by the pressure of the oil .

On the contrary, when the pressure of the oil acting on the internal pressure chamber C is smaller than the reaction force of the return spring, the oil is supplied to the oil pressure chamber to form a flow path for connecting the actuator portion to the operating pressure line The control spool can be moved to the other side.

In addition, the present invention may further include a sensitivity adjusting unit that adjusts a reaction force of the return spring to adjust a load sensing degree of the control spool.

The sensitivity adjusting unit may include a position variable spring supporting the return spring and movably disposed on one side of the valve body along the displacement direction of the return spring; And a sensitivity adjusting screw which is in contact with the spring retainer and a part of which is screwed to an end of the valve body.

The stopper may include a stopper portion formed in the housing of the hydraulic motor so as to correspond to the swash plate one-side corner position and to prevent the swash plate from further decreasing when the angle of the swash plate with respect to the motor shaft reaches a minimum angle. As shown in FIG.

According to another aspect of the present invention as a solution to the problem,

A method for controlling a swash plate angle of a variable displacement hydraulic motor of a hydrostatic type continuously variable transmission according to one aspect,

The swash plate control valve controlling the swash plate angle by varying the axial position of the control spool according to the pressure fluctuation of the oil in the circuit due to the load change, A variable-capacity hydraulic motor swash plate angle control method of a constant-oil-pressure variable-speed-transmission transmission that allows an angle to be increased or decreased according to a load condition.

Here, the balance of the force between the oil pressure acting on the inner pressure chamber (C) of the control spool and the return spring for elastically supporting the control spool according to the load size is used to adjust the angle of the swash plate Can be varied.

According to the embodiment of the present invention, the hydraulic motor is configured as a variable displacement type. In particular, the swivel angle of the hydraulic motor is automatically adjusted using a circuit pressure that varies depending on the load size. Therefore, it is possible to exhibit proper output performance in accordance with various load situations depending on driving or working environment, and thus it is possible to actively cope with load situations.

In other words, it is possible to cope flexibly according to the load condition, and it is possible to provide an appropriate output according to the situation, so that the work efficiency of the working vehicle can be improved. Further, The load on the power source can be minimized, thereby reducing the fatigue of the driver due to operational fatigue and shifting shock caused by frequent downshifting.

1 is a cross-sectional view of a hydrostatic stepless speed change transmission in accordance with an aspect of the present invention;
FIG. 2 is a hydraulic circuit diagram of a transmission system including the hydrostatic type transmission of FIG. 1; FIG.
Fig. 3 is an enlarged sectional view of the swash plate control valve of Fig. 1; Fig.
4 is a cross-sectional view showing an operating state of the hydraulic motor in a high load operation.
Fig. 5 is a hydraulic circuit diagram of the transmission system showing the flow of working fluid during a high load operation. Fig.
6 is a transverse sectional view showing the operating state of the hydraulic motor in low load operation.
7 is a hydraulic circuit diagram of a shift system that indicates the flow of working fluid during low load operation.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It is to be understood that the terms "comprises", "having", and the like in the specification are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Also, the terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

In addition, the terms " part, "" unit," " module, "and the like, which are described in the specification, refer to a unit for processing at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software .

In the following description with reference to the accompanying drawings, the same reference numerals are given to the same constituent elements, and a duplicate description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Fig. 1 is a cross-sectional view of a hydrostatic stepless speed change transmission according to one aspect of the present invention, and Fig. 2 is a hydraulic circuit diagram of a transmission system including the hydrostatic stepless speed change transmission of Fig.

1 and 2, the hydrostatic stepless speed change transmission 10 is constituted by one variable capacity hydraulic pump 12 and one variable capacity hydraulic motor 16. As shown in FIG. The variable displacement hydraulic pump 12 is driven by a power source 20 such as an engine and the hydraulic motor 16 is driven in conjunction with the hydraulic pump 12 and is driven by a swivel angle ) The rotation speed and direction are determined according to the change in the discharge flow rate according to the change.

First, the configuration of the hydraulic pump will be described.

The variable displacement hydraulic pump 12 includes a cylinder block 124 on which a plurality of pistons 123 are mounted. A trunnion swash plate 122 (hereinafter referred to as a swash plate) for reciprocating the piston 123 is installed adjacent to the cylinder block 124 at one side of the cylinder block 124, And the cylinder block 124 is installed on the pump shaft 120 so as to rotate integrally with the pump shaft 120.

The hydraulic pump 12 is driven by a power source 20, e.g., engine power. To this end, the pump shaft 120 is directly connected to the output shaft of the power source 20 so as to be able to transmit power in a belt or chain manner. When the hydraulic pump 12 is driven by the output of the power source 20, the hydraulic pump 12 sucks the hydraulic fluid and discharges the hydraulic fluid to the hydraulic motor 16 side with a predetermined pressure. When the hydraulic motor 16 is driven by the hydraulic pump 12 To output the transmission power.

The rotation speed and direction of the motor shaft 160 of the hydraulic motor 16 are determined by the flow rate of the hydraulic pump 12 and the size of the circuit pressure load and are transmitted from the hydraulic pump 12 to the hydraulic motor 16 The flow rate and the pressure of the operating oil can be adjusted by changing the swivel angle of the swash plate 122 of the hydraulic pump 12 (the angle of the swash plate with respect to the pump shaft 120).

For example, when the swash plate 122 is at the "0" position, there is no discharge flow rate of the hydraulic pump 12, and the swash plate 122 is in a neutral state. When the swash plate angle is inclined at a predetermined angle in the forward direction, The hydraulic motor 16 outputs power in the forward direction by the suction / discharge flow rate of the hydraulic pump 12 to be determined. In the opposite case, the discharge direction of the flow rate changes, and the rotation direction of the hydraulic motor 16 also changes.

The swash plate angle adjustment of the hydraulic pump 12 is implemented by a hydraulic swash plate angle adjusting means 126 for rotating the trunnion shaft (not shown) on both sides of the swash plate 122, for example, a hydraulic cylinder. The operation of the swash plate angle adjusting means 126 can be controlled by the hydraulic pressure interrupting operation of the hydraulic valve 128 (see FIG. 2) in which the internal passage state is switched by the operation of the driver shift lever 129.

Of course, although not specifically illustrated in the drawings, the control system may be implemented in an electronic control system in which the operation of the swash plate angle control solenoid valve (not shown) operated by a predetermined output signal from the ECU is controlled by hydraulic pressure control.

The electronic control performed by the ECU further includes a method of controlling the swash plate angle control solenoid valve by controlling the signal of the ECU based on the operating position detection information of the speed change operation mechanism such as a speed change pedal or a lever, There is a method of controlling the solenoid valve based on vehicle load information that is grasped from the information.

The swash plate angle control is performed by a shift position detecting means (variable resistance switch) that detects an operation position for the shift operation mechanism (or an operation amount) of the shift operation mechanism, Determining the control value from the information provided by the means and controlling the operation of the swash plate angle control solenoid valve with the determined control value.

That is, in the swash plate angle control using the shift operating mechanism, the operating position of the shift operating mechanism intended by the driver is determined on the basis of the detection information of the shift position detecting means, and a predetermined control The swash plate angle control solenoid valve of the hydraulic pump controls the swash plate angle of the hydraulic pump 12 to directly adjust the output of the hydraulic pump 12 according to the situation.

The flow amount discharged from the hydraulic pump 12 by the speed change operation mechanism is sent to the hydraulic motor 16. At this time, the hydraulic motor 16 rotates faster as the flow rate delivered by the swash plate of the hydraulic pump 12 becomes larger .

The flow rate of the hydraulic fluid discharged from the hydraulic pump 12 is transferred to the hydraulic motor 16 and the hydraulic motor 16 is rotated. At this time, if the torque for driving the vehicle is changed by an external factor, The swash plate 162 of the variable-type hydraulic motor 16 is changed to the low-capacity side to actively control the output (torque) to the output shaft 16 and the output shaft 16, thereby reducing the rotation speed and increasing the output torque.

In the case of the automatic control for controlling the swash plate angle based on the vehicle load information, the ECU determines the load state of the vehicle from the information provided by the vehicle angle detecting means, selects an appropriate control value set corresponding to the detected load amount, The swash plate angle control can be realized by controlling the operation of the swash plate angle control means 126 by outputting the selected control value to the swash plate angle control solenoid valve.

The load detecting means used to determine the vehicle load in the swash plate angle automatic control may include means for detecting the actual rotational speed of the power source and rotational speed setting position detecting means for detecting the operational displacement of the speed change operating mechanism. That is, the actual rotational speed (Actual RPM) of the power source and the target rotational speed (Target PRM) set according to the operating position of the shift operating mechanism.

The following describes the hydraulic motor.

Like the above-described hydraulic pump, the hydraulic motor 16 applied to the embodiment of the present invention also has a variable capacity structure. That is, the angle of the swash plate 162 is changed with respect to the motor shaft 160 outputting the continuously-variable power, so that the capacity of the motor is varied to change the rotational speed and torque of the output power output through the motor shaft 160 It has a structure that can be appropriately changed in accordance with the situation.

The hydraulic motor 16 has a cylinder block 164 on which a plurality of pistons 163 are mounted, a swash plate 162 for reciprocating the piston 163, and a motor shaft 160 for rotating the cylinder block 164 . An actuator section 166 for generating a driving force for adjusting the swash plate angle θ and a swash plate control valve 166 for controlling the flow of the driving pressure fluid to the actuator section 166, (168).

A swash plate (162) reciprocating the piston (163) is installed on one side of the cylinder block (164) on which the plurality of pistons (163) are mounted, and is installed adjacent to the rear side of the cylinder block And the cylinder block 164 is rotatably mounted on a motor shaft 160 that outputs the final continuously variable shifted power to the outside (preferably, the auxiliary speed change portion). The cylinder block 164 rotates the motor shaft 160 on the motor shaft 160, As shown in Fig.

The actuator portion 166 is provided to be connected to the rear portion of the swash plate 162. The actuator unit 166 is operated by an oil pressure provided through an operating pressure line 30 according to a switching state of the swash plate control valve 168 so that the inclination angle of the swash plate 162 with respect to the motor shaft 160 So that the driving force is regulated. As shown in the drawing, the actuator unit 166 can be preferably configured in the form of a single acting cylinder.

Actuator portion 166 specifically includes a piston 166b and a piston shoe 166c. The piston 166c reciprocates within the pressure chamber 166a formed at the rear of the swash plate 162 and changes the swash plate angle θ so that the piston shoe 166c is reciprocated in a swash plate 162). ≪ / RTI >

When the swash plate control valve 168 is switched to the side allowing the oil supply to the actuator portion 166, the oil provided by the working pressure line 30 is supplied to the actuator portion 166 through the internal flow path of the end block 14 And the swash plate 162 is rotated in a direction in which the angle with respect to the motor shaft 160 is reduced. As a result, the allowable capacity of the motor is reduced, the number of revolutions of the motor shaft 160 is increased, and the torque is reduced

Conversely, when the swash plate control valve 168 is switched to the drain side, the supply of oil to the actuator portion 166 is interrupted, and the drain flow path for returning the oil filled in the actuator portion 166 to the oil tank T side is opened. As a result, the oil in the pressure chamber 166a escapes and the piston 166b retracts. As a result, the swash plate 162 is rotated in the direction of increasing the allowable capacity of the motor, 160).

The swash plate control valve 168 may be installed at one side of the housing (not shown) of the hydraulic motor 16. The swash plate control valve 168 controls the operation of the actuator unit 166 by interrupting the flow of the oil to the actuator unit 166. The swash plate control valve 168 controls the operation of the actuator unit 166 according to the circuit pressure fluctuation, The axial position of the valve body 168a can be varied to switch the flow path.

1, reference numeral 169 denotes a stopper portion that defines a swash plate angle θ, that is, a minimum value of the inclination angle of the swash plate 162 with respect to the motor shaft 160. The stopper portion 169 is a stopper portion, When the angle of the swash plate 162 with respect to the motor shaft 160 reaches the minimum angle (? _Min ), the swash plate 162 is not angled To the extent that it does not diminish.

3 is an enlarged cross-sectional view of the swash plate control valve of FIG.

Referring to Figure 3 and to Figure 1 which is attached heretofore, the swash plate control valve 168 includes a control spool 168a, a return spring 168b, and a fixed sleeve 168c.

The control spool 168a has an inner pressure chamber C formed at its center. And a fixed piston 168d supported on an end cap 168e so as to be able to move in the axial direction in accordance with a variation in the pilot pressure acting on the internal pressure chamber C. [ That is, the control spool 168a can be relatively linearly moved with respect to the fixed piston 168d according to the pressure fluctuation of the oil filled in the internal pressure chamber C.

At least one groove dividing the flow path is formed in the outer surface of the control spool 168a in the arc direction. Two grooves (h1, h2) having different widths, depths, and axial positions are preferably formed. The groove h1 and the inner pressure chamber C are radially spaced from each other so that the oil supplied through the groove h1 into which the oil flows from among the two grooves h1 and h2 can be filled in the inner pressure chamber C, And are connected to each other through a channel (sign is omitted).

The return spring 168b generates a restoring force corresponding to the movement of the control spool 168a that performs a relative movement with respect to the fixed piston 168d in the valve body in accordance with the pressure fluctuation of the oil acting on the inner pressure chamber C The fixed sleeve 168c has holes h3, h4 and h5 corresponding to the grooves h1 and h2 and is connected to the control spool 168a and the control spool 168a. Valve body (not shown).

The axial position of the control spool 168a with respect to the fixed sleeve 168c according to the balance of the pressure between the oil pressure acting on the inner pressure chamber C and the return spring 168b depending on the load condition And the swash plate angle? Is changed by changing the connecting positions of the grooves h1 and h2 and the holes h3 to h5 and the channel area between the grooves and the holes. That is, the swash plate angle &thetas; can be appropriately and flexibly varied according to the load size.

When a large load is applied to the motor shaft 160 (during a high load operation), the circuit pressure of the hydraulic circuit rises naturally. When the raised circuit pressure becomes larger than the set pressure set by the elasticity coefficient of the return spring 168b, that is, the oil pressure acting on the internal pressure chamber C is larger than the reaction force of the return spring 168b due to the circuit pressure rise, (See Figs. 4 and 5) so as to form a drain passage connecting the actuator portion 166 to the oil tank T side.

In this case, when the oil filled in the actuator portion 166 is drawn out by the thrust of the piston 163 on the cylinder block 164 side of the hydraulic motor 16, the oil pressure in the direction In the direction of increasing the capacity of the swash plate 162). As a result, the capacity of the hydraulic motor 16 to the capacity of the hydraulic pump 16 is greatly increased to decrease the number of revolutions of the motor shaft 160, but it is possible to cope with high load operation by increasing the output torque.

Conversely, when the pressure of the oil acting on the internal pressure chamber C is smaller than the reaction force of the return spring 168b (during a low load or no load operation), the actuator portion 166 is operated by the restoring force of the return spring 168b The control spool 168a is moved in a direction to connect with the pressure line (Pilot Line) 30. [ The control spool 168a is moved in the axial direction in the direction of forming the oil passage for allowing the oil supply to the actuator portion 166 (see Figs. 6 and 7).

A predetermined pressure oil flowing through the working pressure line 30 is supplied to the actuator section 166 through the swash plate control valve 168 and the piston constituting the actuator section 166 is rotated by the swash plate angle? The swash plate angle [theta] is changed to the set minimum inclination angle [theta] _min by pushing the swash plate 162 in the direction in which the capacity of the hydraulic motor 16 is reduced, One power suitable for a no-load operating condition is output through the motor shaft 160.

The load value applied to the motor shaft 160 may vary depending on the specification and size of the vehicle to which the transmission according to one aspect of the present invention is applied. The fluctuation range of the circuit pressure can also be varied. The swash plate control valve 168 applied to the present embodiment has a structure in which the control spool 168a is moved in the axial direction to switch the flow path according to the balance between the reaction force of the return spring 168b and the circuit pressure .

Therefore, if the reaction force (elastic modulus) of the return spring 168b is appropriately adjusted, the sensitivity of the swash plate control valve 168 is adjusted as desired according to the load value that varies depending on the specification or the size of the vehicle, . The swash plate control valve 168 is provided with a sensitivity adjusting unit 165 for adjusting the load sensing degree of the control spool 168a through the reaction force adjustment of the return spring 168b.

The sensitivity adjusting unit 165 may be configured to include a variable spring holding unit 165a and a sensitivity adjusting screw 165b as shown in the drawing. The control spool 168a adjusts the compression state of the return spring 168b by varying the position of the variable spring 172a in the valve body by forward and reverse rotation of the sensitivity adjusting screw 165b, To adjust the operating sensitivity of the system.

The adjustable spring support member 165a may be a plate-like member having a predetermined thickness and may support the return spring 168b and may be installed on one side of the valve body so as to be movable along the displacement direction of the return spring 168b And the sensitivity adjusting screw 165b may be in contact with the spring retainer 165a and a part of which may be screwed to the end portion of the valve body and include an adjusting handle at an end portion extending outward from the valve body.

Hereinafter, the operation principle of the hydrostatic stepless speed change transmission according to one aspect of the present invention will be described in connection with a swash plate angle control method of a variable displacement hydraulic motor according to another aspect of the present invention, .

The swash plate angle control of the hydraulic motor 16 according to another aspect of the present invention is performed such that the angle of the swash plate 162 with respect to the motor shaft 160 of the hydraulic motor 16 automatically increases or decreases according to the load conditions, The operation of the actuator unit 166 is controlled by using the swash plate control valve 168 whose axial position of the control spool 168a is varied in accordance with the pressure fluctuation of the oil in the circuit due to the load change .

Preferably, the control spool 168a (168a) is controlled in accordance with the balance between the oil pressure (Pilot pressure) acting on the inner pressure chamber C of the control spool 168a and the return spring 168b, Is determined and the angle of the swash plate 162 is changed in accordance with the load conditions so that the hydraulic motor 16 can output an appropriate output in response to the load without any manual operation or electrical control.

Hereinafter, a more detailed description will be given with reference to the drawings.

Figs. 4 to 7 are operational states of the present invention. Fig. 4 and Fig. 5 are cross-sectional views of the hydraulic circuit and the hydraulic motor showing the flow of the working fluid and the operating state of the hydraulic motor during the high- A hydraulic circuit diagram showing the operating fluid flow and an operating state of the hydraulic motor at low load operation and a cross-sectional view of the hydraulic motor are shown respectively.

Let's start with the operation under high load operation.

Referring to FIGS. 4 and 5, when a large load is applied to the motor shaft 160 (during a high load operation), the circuit pressure of the hydraulic circuit rises naturally. When the raised circuit pressure is equal to or higher than the set pressure set by the return spring 168b, the control spool 168a is moved to one side (to the left in the drawing) by the relative movement with respect to the fixed piston 168d, .

That is, when a large load is applied to the motor shaft 160 and the circuit pressure rises and the oil pressure acting on the inner pressure chamber C becomes larger than the reaction force of the return spring 168b, the control spool 168a against the fixed piston 168d, The control spool 168a is moved in the axial direction so as to form a drain flow path connecting the actuator portion 166 to the oil tank T side (see arrows in Fig. 4).

The oil filled in the actuator portion 166 is pulled out by the thrust of the piston 163 on the cylinder block 164 side of the hydraulic motor 16 and the oil pressure in the direction of increasing the swash plate angle? The swash plate 162 is rotated. As a result, the capacity of the hydraulic motor 16 to the capacity of the hydraulic pump 16 is greatly increased to decrease the number of revolutions of the motor shaft 160, but it is possible to cope with high load operation by increasing the output torque.

That is, when the swash plate control valve 168 is switched to the drain side by increasing the circuit pressure by the load, the supply of the working fluid to the actuator unit 166 is interrupted, and the drain, which returns the working fluid filled in the actuator to the oil tank T side The oil passage is opened and the piston is retracted. As a result, the swash plate 162 is rotated in the direction of increasing the allowable capacity of the motor, so that the low-rotation high-torque power is output through the motor shaft 160.

Next, referring to FIG. 6 and FIG. 7, operation at low load (or no load) operation will be described.

6 and 7, when the pressure of the oil acting on the inner pressure chamber C is smaller than the reaction force of the return spring 168b (in the case of low load or no load operation) in the state shown in FIG. 4, The control spool 168a is moved to the original position where the actuator portion 166 is connected to the operating pressure line 30 (Pilot Line) by the elastic restoring force of the spring 168b.

In other words, the control spool 168a is moved in the axial direction in the direction of forming the oil passage for allowing the oil to be supplied to the actuator portion 166 (see arrows).

The oil of the predetermined pressure in the working pressure line 30 is supplied to the actuator portion 166 through the swash plate control valve 168 and the swash plate 162 is moved in the direction in which the swash plate angle? The swash plate angle [theta] is changed to the set minimum inclination angle [theta] _min so that the capacity of the hydraulic motor 16 is varied to the minimum capacity within a variable range so that a power suitable for the bottom part or the no- (160).

The swash plate control valve 168 is switched to the side for allowing the oil supply to the actuator portion 166 so that the oil of the predetermined pressure is supplied to the actuator portion 166 and the motor shaft 160 The swash plate 162 is rotated in the direction in which the angle with respect to the motor shaft 160 is reduced. As a result, the allowable capacity of the motor becomes small and the power of the high rotation low torque is output through the motor shaft 160.

On the other hand, when the swash plate angle?, I.e., the inclination angle of the swash plate 162 with respect to the motor shaft 160 reaches the set minimum swing angle defined by the stopper portion 169 by the oil supply to the actuator portion 166, The swash plate angle θ and the capacity of the hydraulic motor 16 are not further reduced because a part of the swash plate 162 is caught by the stopper portion 169 and is further restricted in rotation.

According to the hydrostatic stepless speed change transmission and its control method according to the embodiment of the present invention as described above, the hydraulic motor is configured as a variable displacement type, and the flow rate of the working fluid is controlled by the control value outputted from the load information, The swivel angle of the swivel is automatically adjusted. Therefore, it is possible to actively cope with load situations that vary depending on driving or working environment.

In other words, it is possible to cope flexibly according to the load condition, and it is possible to provide an appropriate output according to the situation, so that the work efficiency of the working vehicle can be improved. Further, The load of the power source can be minimized, thereby reducing the fatigue of the driver due to operational fatigue and shifting shock caused by frequent downshifts.

In the foregoing detailed description of the present invention, only specific embodiments thereof have been described. It is to be understood, however, that the invention is not to be limited to the specific forms thereof, which are to be considered as being limited to the specific embodiments, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. .

10: transmission 12: hydraulic pump
16: Hydraulic motor 20: Power source
30: working pressure line 160: motor shaft (output shaft)
162: swash plate (motor side) 165: sensitivity adjusting section
165a: spring retainer 165b: sensitivity adjusting screw
166: Actuator part 166a: Pressure chamber
166b: piston 166c: piston shoe
168: swash plate control valve 168a: control spool
168b: return spring 168c: fixed sleeve
168d: fixed piston 168e: end cap
169: Stopper part H1: Hydraulic pump hinge pin
H2: Hydraulic motor hinge pin

Claims (10)

A hydrostatic type transmission system comprising a variable displacement hydraulic pump driven by a power source of an engine and a hydraulic motor driven in conjunction with the hydraulic pump and having a variable rotational speed according to a discharge flow rate of the hydraulic pump,
Wherein the hydraulic motor is a variable displacement hydraulic motor in which the angle of the swash plate with respect to the motor shaft is automatically variable according to the load on the motor shaft,
An actuator unit installed to be connected to the swash plate rear portion inside the hydraulic motor and operated by hydraulic pressure to adjust the angle of the swash plate with respect to the motor shaft; And
And a swash plate control valve which is installed at one side of the housing of the hydraulic motor and in which the oil is supplied to the actuator portion in accordance with the pressure fluctuation of the oil supplied to the inside or the oil passage is switched so as to discharge the oil inside the actuator portion, Transmission Transmission.
The method according to claim 1,
The actuator unit includes:
A piston reciprocating in a pressure chamber behind the swash plate;
And a piston shoe coupled to the piston and contacting the surface of the swash plate facing the piston.
The method according to claim 1,
The swash plate control valve includes:
Wherein a volume variable internal pressure chamber (C) is formed at the center by a fixed piston supported by the end cap, one or more grooves are formed in the outer surface portion in a circular arc direction, and a pressure fluctuation A control spool that moves relative to the stationary piston in the axial direction according to the rotation of the stationary piston;
A return spring for generating a restoring force against the pressure of the oil acting on the internal pressure chamber (C);
And a fixed sleeve installed between the control spool and the valve body and having a plurality of holes corresponding to the grooves,
The axial position of the control spool is determined according to the balance between the oil pressure acting on the inner pressure chamber C and the return spring in accordance with the load, and the connection position of the groove and the hole, Wherein the oil passage area between the first oil passage and the second oil passage is variable.
The method of claim 3,
The control spool is moved to one side so as to form a drain passage connecting the actuator portion to the oil tank side by the pressure of the oil when the pressure of the oil acting on the internal pressure chamber C is larger than the reaction force of the return spring. Hydraulic transmissions.
The method of claim 3,
When the pressure of the oil acting on the inner pressure chamber C is smaller than the reaction force of the return spring, the control spool is operated to connect the actuator portion to the operating pressure line (Pilot Line) side by the elastic restoring force of the return spring. Is shifted to the other side. ≪ IMAGE >
The method of claim 3,
And a sensitivity adjusting unit adjusting the reaction force of the return spring to adjust the load sensing degree of the control spool.
The method according to claim 6,
The sensitivity adjuster includes:
A variable spring spring supporting the return spring and movably installed in one end of the valve body along the displacement direction of the return spring; And
And a sensitivity adjusting screw which is in contact with the spring retainer and is partly screwed to an end of the valve body.
The method according to claim 1,
And a stopper portion that is formed in a housing of the hydraulic motor so as to correspond to the swash plate one side edge position and regulates the swash plate angle so that the swash plate angle is no longer reduced when the angle of the swash plate with respect to the motor shaft reaches a minimum angle, Hydraulic stepless transmission.
9. A method for controlling a swash plate angle of a variable displacement hydraulic motor of a constant-pressure-type stepless speed change transmission as set forth in any one of claims 1 to 8,
A variable displacement hydraulic motor swash plate using a swash plate control valve in which an axial position of a control spool is varied in accordance with a pressure variation of oil in a circuit due to a change in load in control of operation of an actuator for adjusting an angle of the swash plate; Angle control method.
10. The method of claim 9,
The balance of the force between the oil pressure acting on the inner pressure chamber (C) of the control spool and the return spring elastically supporting the control spool according to the load size is used to vary the angle of the swash plate A variable displacement hydraulic motor swashplate angle control method for a hydrostatic stepless speed change transmission.

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