JP2001289176A - Travel control device - Google Patents

Abstract

(57) [Problem] A traveling control device configured to detect a load on an engine and automatically shift a continuously variable transmission according to the magnitude of the load is useful. Performing such control may be inconvenient. SOLUTION: A hydraulic pump 11 linked to an engine is connected.
The traveling control device of the present invention, which is provided in a vehicle including a hydraulic motor 21 that receives and drives the pressure oil from the hydraulic pump 11, is configured to have two control modes.
The first mode is a mode in which the angle of the pump swash plate 13 is changed according to the speed change pedal 27 and the motor swash plate 23 is fixed. In the second mode, the angle of the pump swash plate 13 is changed according to the speed change pedal 27, and the angle of the motor swash plate 23 is controlled according to the load of the engine. The first mode and the second mode correspond to the lever 36
Is configured to be switchable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel control device provided in a vehicle.

[0002]

2. Description of the Related Art Conventionally, a hydrostatic continuously variable transmission (hereinafter, referred to as "HST") is provided on a drive transmission path from an engine output shaft to an axle of a vehicle, and the HST detects an engine load. Control means for automatically shifting to a small reduction ratio side as the load of the engine decreases, and automatically shifting to a large reduction ratio side as the load increases. The traveling control device described above is known. This configuration shifts to the speed increase side when the engine load is small to make the engine more efficient, and when the engine load is large, it shifts to the deceleration side to automatically protect the engine from overload. , Very useful.

[0003]

[Problems to be solved by the invention]
Depending on the purpose or the like, the constant execution of the shift control according to the engine load as described above may rather cause inconvenience.

[0004] For example, when the travel control device for performing the above control is applied to a mower tractor, the following problems occur. That is, when the mower tractor travels on the road surface to move to a work place or the like, the above-described control in which the speed is changed according to the engine load in order to efficiently exert the engine performance and protect it from overload. Is valid. On the other hand, when the mower tractor performs lawn mowing work, the range of fluctuation of the engine load on the traveling road surface (turf surface) is small, and the possibility of engine overload is extremely low. Rather, if the vehicle speed is changed according to the change in engine load during lawn mowing, the mowing height becomes non-uniform, causing a poor appearance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a traveling control device capable of artificially switching between a state in which control for shifting according to an engine load is performed and a state in which control is not performed. It is something to offer.

[0006]

The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

That is, according to claim 1, there is provided an engine and a hydraulic pump interlocked with the engine.
A hydraulic motor driven by receiving pressure oil from the hydraulic pump, wherein the volume of the pump swash plate can be changed continuously by changing the angle of the pump swash plate; A travel control device provided in a vehicle including at least a vehicle whose volume can be continuously changed and an axle interlocked with the hydraulic motor,
a) a first mode in which the angle of the pump swash plate is changed in accordance with an operation position of a shift operation means provided in a vehicle to fix the angle of the motor swash plate; Changing the angle according to the operation position of the shift operation means,
A second mode for changing the angle of the motor swash plate in accordance with the load of the engine, and furthermore, it is possible to arbitrarily switch between the first mode and the second mode. It is what was constituted.

According to a second aspect of the present invention, there is provided an engine and a hydraulic pump interlocked with the engine, wherein the volume can be changed continuously by changing the angle of a pump swash plate. A vehicle comprising a hydraulic motor driven by receiving hydraulic oil, the volume of which can be changed continuously by changing the angle of a motor swash plate, and an axle interlocked with the hydraulic motor. A) a first mode in which the angle of the pump swash plate is changed in accordance with the operation position of a shift operation means provided in a vehicle, and the angle of the motor swash plate is fixed. And b) changing the number of revolutions of the engine in accordance with the operation position of the speed change operation means, changing the angle of the pump swash plate in accordance with the operation position of the speed change operation means, Corner And a second mode that changes according to the load of the engine, and is further configured to be able to arbitrarily switch between the first mode and the second mode. .

[0009]

Next, embodiments of the present invention will be described. The vehicle provided with the travel control device of the present invention has a drive transmission configuration from the engine to the axle as shown in FIG. 1, and is controlled by the axle drive device shown in FIGS. 2 to 4 by the travel control device. A hydraulic pump, a hydraulic motor, etc. are arranged. First, the axle drive device will be described. FIG. 1 is a skeleton diagram showing a power transmission configuration of a vehicle provided with the traveling control device of the present invention, and FIG. 2 is a plan view partially sectional view showing the configuration of an axle drive device provided in the vehicle. 3 is a sectional view taken along the line AA in FIG. 2, and FIG.
5 is a sectional view taken along the line BB in FIG.

This axle drive device 1 whose power transmission structure is shown in FIG. 1 has a housing 9 as shown in FIGS.
The upper housing 9t and the lower housing 9b are joined to each other at a horizontal and flat joining surface around them. A bearing portion for the motor shaft 22, which will be described later, is provided on the joint surface. A bearing portion for rotatably supporting the axles 50L and 50R is displaced upward from the joint surface and disposed in the upper housing 9t. (FIG. 4). As shown in FIGS. 1 and 2, the inner ends of the two axles 50L and 50R are differentially coupled by a differential mechanism 40, while the outer ends are respectively outward from the left and right outer walls of the housing 9. It is extended.

The interior of the housing 9 is as shown in FIG.
The housing 9 is partitioned into a first room R1 and a second room R2 by a partition wall 9i formed integrally with the housing 9. In the first room R1, a hydrostatic continuously variable transmission (hereinafter referred to as “HST”) is provided.
Called. ) 8 is accommodated, and in the second room R2, a drive train 30 composed of a gear train transmitting power from the motor shaft 22 to the differential mechanism 40, the differential mechanism 40 and the axle 50
L · 50R is stored. As shown in FIG. 2, the partition wall 9i includes a longitudinal portion parallel to the axles 50L and 50R and a vertical portion extending substantially perpendicularly to the longitudinal portion in plan view, and both portions are provided continuously. And the first room R
The first and second rooms R2 are arranged adjacent to each other.

An oil reservoir is formed in the first chamber R1 and the second chamber R2 to be filled with a common lubricating oil, and the lubricating oil also serves as a hydraulic oil for the HST8. An oil filter 81 is arranged on the partition wall 9i separating the two rooms R1 and R2 (FIGS. 2 and 3), and the first room R
The first and second chambers R2 can be circulated through the oil filter 81. Further, an oil circulation port is provided at an appropriate position of the housing 9 (not shown), and an external reservoir tank (not shown) is connected via a piping (not shown) formed of a rubber hose or the like. Rises and the volume of hydraulic oil in the room R1 and the room R2 increases, the amount of oil can be adjusted by flowing the increased amount to the reservoir tank.

As shown in FIG. 2, the first room R1 is located in the housing 9 in front of the axle 50R on one side, and
It is arranged on the side of the drive train 30 that transmits power from the motor shaft 22 to the differential mechanism 40.

Next, the HST placed in the first room
8 will be described. In the first room R1, the center section 10 of the HST 8 is detachably mounted. As shown in FIG. 2, the center section 10 is disposed so that its longitudinal direction is perpendicular to the axles 50L and 50R in plan view, and its front portion has a vertical surface (axles 50L and 5L).
(A plane perpendicular to 0R), and the hydraulic motor 21 is disposed here with the vertical plane as the motor mounting surface 10m. On the other hand, a horizontal surface is formed at the rear part of the center section 10, and the hydraulic pump 11 is disposed here with the horizontal surface as the pump attachment surface 10p. A pump shaft 12 is supported vertically at the center of the pump attachment surface 10p.

FIGS. 2 and 3 show the hydraulic pump 11.
This will be described with reference to FIG. That is, a cylinder block 14 is rotatably slidably disposed on the pump attachment surface 10p of the center section 10, and a plurality of cylinder holes are formed in the cylinder block 14, and each of the cylinder holes is biased. The pistons 15, 15, ... are reciprocally fitted via springs. The movable swash plate 13 is in contact with the heads of the pistons 15. In this specification, the “pump swash plate” means the movable swash plate 13 provided in the hydraulic pump 11. The pump shaft 12 also serves as an input shaft, and
Are arranged vertically along the rotation axis of the cylinder block 14, and are spline-fitted to the cylinder block 14 so that relative rotation is impossible. As shown in FIG. 4, the upper end of the pump shaft 12 projects upward from the upper wall of the upper housing 9t, the input pulley 6 is fixed to the projected portion, and the cooling fan 7 is further attached. As shown in FIG. 1, the power of the output shaft 3 of the engine 2 is input to the input pulley 6 via the output pulley 4 and the belt 5. With this configuration, the piston contact surface of the pump swash plate 13 is tilted by an arbitrary angle from a plane (horizontal plane) perpendicular to the rotation axis of the hydraulic pump 11,
The discharge amount and discharge direction of the oil from the hydraulic pump 11 can be changed, and the discharged pressure oil is supplied to a hydraulic oil circulation circuit (111.1) to be described later formed in the center section 10.
The oil is supplied to a hydraulic motor 21 described below via 12).

The pump swash plate 13 is a trunnion-type movable swash plate. Both ends of the swash plate 13 are curved downward, and trunnion shafts 60 are provided concentrically at their respective ends.
One is supported by the partition wall 9i, and the other is supported by a side cover attached to the side wall of the housing 9 and penetrates and extends to the outside (FIG. 2). Fixed. The control arm 61 is linked to a link mechanism 100a described later (FIG. 1). The link mechanism 100a is configured to control the control arm 61 in accordance with the operation of a speed change pedal 27 that is a speed change operation means provided in the vehicle.
The speed change pedal 27 constitutes a speed change operation means of the vehicle, has two front and rear tread portions, and is configured to advance when depressed on the front side and to reverse when depressed on the rear side. The speed can be increased according to the quantity. With this configuration, when the control arm 61 is rotated in the vehicle longitudinal direction by depressing the shift pedal 27, the pump swash plate 13 tilts around the trunnion shaft 60, and the output of the hydraulic pump 11 is output as described above. Can be changed.

Further, a throttle arm 134 for adjusting the opening of the carburetor 130 of the engine 2 is connected to the output side of the link mechanism 100a.
The throttle arm 134 is tilt-controlled in accordance with the position of the accelerator lever 20 for controlling the rotation speed of the throttle arm 134. The detailed configuration of the link mechanism 100a will be described later.

As shown in FIG. 2, a neutral return arm 13a is integrally formed on the pump swash plate 13 in a convex shape.
An engagement pin 67 protrudes from the tip. On the other hand, a neutral return spring 69, which is a torsion coil spring, is externally fitted on the trunnion shaft 60 in the housing 9, and both ends of the neutral return spring 69 extend in the direction of the neutral return arm 13a while crossing each other. The eccentric shaft 66 provided on the inner wall of the upper housing 9t and the engaging pin 67 are sandwiched between the ends of the extended portion. With the above configuration, when the control arm 61 is rotated by depressing the speed change pedal 27, one end of the neutral return spring 69 is expanded by the engagement pin 67, and the other end is eccentric. 66, the control arm 61
To the neutralizing force. Therefore, when the operating force on the control arm 61 is released, the engaging pin 67 is returned to its neutral position defined by the eccentric shaft 66 and held by the restoring force of the neutral return spring 69. The portion of the eccentric shaft 66 extending outside the housing is formed as an adjusting screw, and the neutral position of the pump swash plate 13 is adjusted by arbitrarily rotating and displacing the eccentric shaft 66 via the screw portion. Can be.

Next, the configuration of the hydraulic motor 21 will be described.
As shown in FIG. 2, a cylinder block 24 is mounted on the motor-attached surface 10m of the center section 10 so as to be rotatable and slidable with its axis of rotation oriented in a direction parallel to the axles 50L and 50R. A plurality of cylinder holes are formed in the cylinder block 24, and a plurality of pistons 25 are reciprocally fitted in the respective cylinder holes via urging springs. Upper housing 9t and lower housing 9b
The movable swash plate 23 is disposed between the movable swash plate 23 and the head of the piston 25 is in contact with the movable swash plate 23. In this specification, the “motor swash plate” refers to the hydraulic motor 2.
1 means the movable swash plate 23 provided in the device 1. Then, the motor shaft 22 is spline-fitted onto the rotation axis of the cylinder block 24 so as not to rotate relatively, and the motor shaft 22 is supported in the left-right horizontal direction (direction parallel to the axles 50L and 50R). In this manner, an axial piston type variable displacement hydraulic motor in which the directions of the pistons 25 are parallel to the motor shaft 22 is configured.

The rear surface of the motor swash plate 23 is formed in a convex arc surface as shown in FIG. 4, and a support portion 109 for closely contacting the convex arc surface and slidably supporting the convex arc surface.
Is provided between the upper and lower housing halves 9t and 9b. The support portion 109 has a concave arc surface 109a that matches the convex arc surface of the motor swash plate 23, and the motor swash plate 23 slides the convex arc surface in close contact with the concave arc surface 109a. By doing so, it is configured to tilt while being guided.

The motor swash plate 23 has an operation arm 23a formed by extending a substantially central portion of a lower edge of the motor swash plate 23 downward as shown in FIGS. And center section 1
A motor swash plate control mechanism 100b, which will be described later, is provided in a lower portion of a substantially half portion located on the side where the hydraulic motor 21 is attached. The motor swash plate control mechanism 100b is for tilting the motor swash plate 23, and includes a piston 35 that receives pressure oil from a charge pump 16 described later and pushes the operation arm 23a of the motor swash plate 23. A return piston 88 for applying an urging force to push the motor swash plate 23 back against the piston 35;
It is composed of a valve for switching between supply and stop of the pressurized oil. The detailed configuration of the motor swash plate control mechanism 100b will be described later.

Next, the configuration of the hydraulic oil circulation circuits 111 and 112 formed inside the center section 10 will be described. That is, a pair of first and second bow-shaped ports are provided on the pump mounting surface 10p of the center section 10 (not shown), and a first bow-shaped port 95 and a second bow-shaped port 96 are also provided on the motor mounting surface 10m. A pair is provided (FIG. 3). As shown in FIG. 3, two upper and lower oil passages (a first oil passage 91 and a second oil passage 92) are bored in parallel in the center section 10 along the longitudinal direction. . A first bow-shaped port of the pump-attached surface 10p and a first bow-shaped port 95 of the motor-attached surface 10m are obliquely drilled in the first oil passage 91 and the center section 10, and the first The second bow-shaped port of the pump-attached surface 10p and the second bow-shaped port 96 of the motor-attached surface 10m communicate with each other through a communication oil passage 90 connected to the oil passage 91 via the second oil passage 92. Is communicated.

With the above-described configuration, the hydraulic pump 11 and the hydraulic motor 2
1 is a first circuit 111 for fluid connection, and the second oil passage 92 is a second circuit 112 for fluid connection between the hydraulic pump 11 and the hydraulic motor 21. With these two circuits 111 and 112, HST8
This constitutes the hydraulic oil circulation circuit. With this configuration, when the operator steps on the front tread portion of the speed change pedal 27, the pump swash plate 13 tilts, the hydraulic pump 11 performs a pumping action, and the pressure on the first circuit 111 side increases, Since the second circuit 112 side has a negative pressure,
The hydraulic motor 21 is driven in the forward direction. On the other hand, when the operator steps on the rear tread portion of the speed change pedal 27, the tilting direction of the pump swash plate 13 is opposite to the above case. Is increased, and the first circuit 111 side becomes negative pressure, so that the hydraulic motor 21 is driven in the reverse direction. The driving force of the hydraulic motor 21 is applied to the axle 50L * via the drive train 30 and the differential mechanism 40 described later.
This is transmitted to 50R, and the axles 50L and 50R are driven.

Next, the hydraulic oil circulation circuits 111 and 112
A configuration for compensating for a decrease in hydraulic oil generated in the interior will be described. A common charge oil passage 93 extending in the vertical direction is formed so as to intersect the first oil passage 91 and the second oil passage 92 (FIG. 3).
Check valves 26, 26 for preventing backflow to the air are respectively provided. A charge port is formed at the lower end (opening end) of the charge oil passage 93 and opens to the lower surface of the center section 10. The remaining oil used to drive the mechanism 100b is supplied. The charge pump 16 is a conventional colloid pump, and as shown in FIG.
And an inner rotor and an outer rotor (not shown) are accommodated in the charge pump case 16a, and a suction filter 17 for filtering oil, which is externally attached to a side portion of the housing 9, is provided at a suction port thereof. ing.
The oil discharged from the discharge port of the charge pump 16 is introduced into the motor swash plate control mechanism 100b through an appropriate path, and the remaining pressure oil used is returned to the charge pump case 16a again. Are supplied to the hydraulic oil circulation circuits 111 and 112 from the charge ports. Also,
In order to regulate the charge pressure acting on the charge port, the relief valve 76 is connected to the charge pump case 16.
a (FIGS. 1 and 3). The pump shaft 12 of the hydraulic pump 11 extends downward while penetrating the center section 10 so as to drive the inner rotor and the outer rotor of the charge pump 16,
The pump shaft 12 also serves as a drive shaft of the charge pump 16.

A check valve 19 for preventing freewheeling is connected to the charge oil passage 93, and when the vehicle is stopped on a slope, the hydraulic motor 21 is driven by the axle 50.
The check valve 19 is opened by negative pressure to self-prime the oil in the housing by reducing the amount of hydraulic oil in the hydraulic oil circulation circuits 111 and 112 by performing a pump action by receiving a driving force from the L · 50R side. It is prevented by.

Further, when the mower tractor of this embodiment is connected to the rear end of the vehicle and towed, etc., the hydraulic oil circulation circuit 1
A configuration for bypassing 11 and 112 will be described. That is, as shown in FIG. 4, the camshaft 77 is vertically disposed and rotatably supported by the upper housing 9t. One end of the camshaft 77 is protruded above the housing 9, and the protruding portion is provided with a lever 78. The base end is fixed. The center section 10 is provided with a vertical groove 97 for disposing a lower portion of the cam shaft 77, and the groove 97 is provided near the motor mounting surface 10m. A lower end of the cam shaft 77 is partially cut off to form a cam portion 80. Further, a small-diameter through-hole is formed in the center section 10 in parallel with the motor shaft 22, and one end of the through-hole is connected to the motor mounting surface 1.
0 m and the other end is opened in the groove 97. A pin 79 is disposed in the through hole so that the pin 79 can reciprocate. One end of the pin 79 is close to the cylinder block 24 and the other end is projected into the groove 97. 80.

By rotating the lever 78 in this configuration, the cam shaft 77 is rotated, and the cam portion 80 is
, The tip of the pin 79 projects from the motor-attached surface 10m to push the cylinder block 24, thereby separating the cylinder block 24 from the motor-attached surface 10m. As a result, the hydraulic oil circulation circuits 111 and 112 are bypassed to the oil sump in the housing, and the motor shaft 22 of the hydraulic motor 21 is rotated.
Can be freely rotated. When a vehicle equipped with the present axle drive device is connected to the rear end of another vehicle and towed, etc., the axle 50L interlockingly connected to the motor shaft 22 is used. -The rotation of 50R is made free so that the occurrence of traction resistance can be prevented.

Next, the drive train 30, which transmits power from the motor shaft 22 to a differential mechanism 40 described later, will be described. As shown in FIG. 4, one end of the motor shaft 22 is supported by a bearing hole provided at the center of the motor attachment surface 10m of the center section 10, and the other side is provided with the partition wall 9.
While being supported by the joint surface of i via the bearing 29, the tip thereof is made to protrude into the second chamber R2. Bearing 2
9 is provided with a seal to prevent the oil in the two chambers R1 and R2 from flowing through the bearing 29.
As shown in FIGS. 2 and 4, an output gear 31 is fixed to a portion of the motor shaft 22 that protrudes into the second chamber R2, and a brake disk 32 is further provided. And
A brake device 33 for braking the motor shaft 22 by applying a braking force to the brake disk 32 is provided at a position near the brake disk 32.

Behind the motor shaft 22, a reduction shaft 39 is rotatably supported in parallel with the motor shaft 22, and a wide small-diameter gear 38 is engraved on the outer periphery of the reduction shaft 39.
Further, a large-diameter gear 37 having a central hole that matches the tooth profile of the small-diameter gear 38 is fitted and installed on the small-diameter gear 38 so that relative rotation is impossible. The large-diameter gear 37 meshes with the output gear 31 fixed on the motor shaft 22, and the small-diameter gear 38 meshes with an input gear 41 of a differential mechanism 40 described later.

The differential mechanism 40 will be described with reference to FIGS. A pair of left and right axles 5 arranged concentrically
In addition, differential side gears 44, which are bevel gears, are provided on the inner end sides of 0L and 50R so that they cannot rotate relative to each other.
L · 50R is further extended inwardly in a butt-shape, and the center hole of the input gear 41 is arranged so as to fit outside at the butt portion on the inner end side thereof, and is rotatable and slidable with respect to the left and right axles 50L and 50R. And Further, a through hole 48 is provided in the input gear 41, and a pinion shaft 49 and left and right differential side gears 44 and 4 supported by the pinion shaft 49 are provided in the through hole 48.
4 and the bevel pinions 43 are engaged with each other. The bevel pinion 43 is supported on a pinion shaft 49 via a friction body 56, whereby the bevel pinion 4
3, so that a predetermined braking force is always generated.
This constitutes a so-called limited slip differential mechanism.

The differential mechanism is provided with a differential lock mechanism. Specifically, a lock body 47 is slidably disposed on one axle 50R and provided on the lock body 47. The locking claw 47a is inserted and locked in the engagement hole 42 opened in the input gear 41, and the lock body 47 is configured to be slidable on the axle 50R while maintaining this locked state. . Further, a concave portion 44a is provided in the differential gear 44 on one side.
Are formed, and the recess 4 is formed by the sliding of the lock body.
4 a is configured so as to be freely detachable from the lock body 47. With this configuration, the differential mechanism 40 is locked by the operation of the operator, and the left and right axles 50L and 50R can be integrally rotated.

Next, a first configuration example of the travel control device of the present invention will be described. FIG. 5 is a diagram showing a first configuration example of the travel control device of the present invention, and FIG. 6 is a diagram showing a state where the piston is driven from the state of FIG. 4 and the motor swash plate is tilted. FIG. 7 is a diagram showing a state in which the shift pedal is depressed in the lawn mowing mode in the travel control device of the first configuration example, and FIG. 8 is the same as in the case of depressing the shift pedal in the travel mode. FIG. 9 is a diagram showing a state of control when it is small, and FIG. 9 is a diagram showing a state of control when the load on the engine increases from a state shown in FIG. 8 and exceeds a predetermined value.

The traveling control device includes the speed change pedal 2
7, a link mechanism 100a for inputting the states of the accelerator lever 20 and the work mode switching lever 36 and controlling the throttle arm 134 and the control arm 61 of the hydraulic pump 11 accordingly, and the work mode switching The motor swash plate control mechanism 100b controls the tilt of the motor swash plate 23 according to the operating position of the lever 36 and the load on the engine 2.

First, the link mechanism 100a will be described. That is, as shown in FIG. 5, in the link mechanism 100a, the output arm 27a of the speed change pedal 27 is connected via the link 51 to the tip of the control arm 61 for tilting the pump swash plate 13. ing.
Therefore, when the operator steps on the shift pedal 27,
As shown in FIG. 7, the control arm 61 is tilted,
The pump swash plate 13 is tilted via the above-described trunnion shaft 60, and the volume of the hydraulic pump 11 is changed. Further, an output arm portion 20a of the accelerator lever 20 is connected to a throttle arm 134 of the engine 2 via a wire 64, and controls the tilt of the throttle arm 134 in accordance with the operation position of the accelerator lever 20, thereby controlling the carburetor. Is changed to control the rotation speed of the engine 2. The accelerator lever 20 is provided with a return spring 52 for urging the accelerator lever 20 to the idling position, and generates a frictional force against the urging force of the return spring 52 to operate the accelerator lever 20. A friction mechanism 45 for holding the position is provided at an appropriate position of the accelerator lever 20.

Next, the configuration of the motor swash plate control mechanism 100b will be described. The motor swash plate control mechanism 100b includes a piston 3 for pushing and tilting the motor swash plate 23.
5 and a return piston 88, and a circuit for supplying hydraulic pressure to the piston 35.

First, the structure of the piston 35 and the return piston 88 will be described. That is, as shown in FIGS. 3 and 4, the lower surface of the substantially half portion of the center section 10 on the side where the hydraulic motor 21 is provided is provided with a first extending portion 10 a that extends in a convex shape. The extension 10a is provided with a second extension 10b extending along the longitudinal direction of the motor shaft 22 of the hydraulic motor 21. The tip of the second extension 10b is located near the motor swash plate 23. Is located. This second extension 1
0b, a cylinder chamber 106 is bored, and the cylinder chamber 106 is opened at the tip of the second extension 10b,
A piston 35 is fitted into the opening. The piston 35 includes a cylindrical sliding portion 121 and a pressing portion 122 that is swingably connected to a tip of the sliding portion 121 via a sphere. The pressing portion 122 includes an operation arm 23 described later.
A pressing surface for pressing a is formed.

The opening end side of the cylinder chamber 106 has its inner diameter matched with the outer diameter of the cylindrical sliding portion 121, and the sliding portion 121 slides back and forth in the cylinder chamber 106 while maintaining an oil-tight state. I can move. Further, the cylinder chamber 10
6, a step 106a is provided. When the piston 35 is retracted by a predetermined distance, the end of the sliding portion 121 comes into contact with the step 106a as shown in FIG. 35 so that the motor swash plate 23 is not retracted.
(The minimum value of the tilt angle). On the other hand, the operation arm 23 is attached to the motor swash plate 23 as described above.
The operating arm 23a is in contact with the pressing surface of the piston 35.

A return piston 88 is provided on the side of the operation arm 23a opposite to the side where the piston 35 is provided. Specifically, the support portion 10 supporting the motor swash plate 23
9, a piston support hole 125 is formed, and the return piston 88 is fitted in the piston support hole 125 via a return spring 84 so as to be slidable in a reciprocating manner. This return piston 88
Is similar in shape to the piston 35, and has a cylindrical sliding portion 85 and a receiving portion 86 that is swingably connected to the tip of the sliding portion 85 via a sphere. A receiving surface is formed in the receiving portion 86, and the receiving surface is connected to the operation arm 23a.
Contact. The piston support hole 125 penetrates through the housing 9 to form an open end on the side wall of the housing 9, and an adjusting screw 87 is screwed into the open end. The spring can be moved back and forth in the longitudinal direction, and one end of the return spring 84 is in contact with the tip. With this configuration, the elasticity of the return spring 84 can be adjusted by rotating the adjusting screw 87. The piston support hole 125 is provided with a step 125a, and when the return piston 88 is retracted by a set distance, the end of the sliding section 85 contacts the step 125a as shown in FIG. Prevents the return piston 88 from being retracted, and defines the maximum tilt position (maximum tilt angle) of the motor swash plate 23.

In this configuration, the operation of tilting the motor swash plate 23 according to the pressure in the cylinder chamber 106 will be described. That is, when the pressure in the cylinder chamber 106 is zero, the return piston 88 pushes the operation arm 23a and retracts the piston 35. The piston 35 is in a state as shown in FIG. 4 in which the end thereof is in contact with the step 106a, and at this time, the tilt angle of the motor swash plate 23 is minimized. When the pressure in the cylinder chamber 106 increases from this state and exceeds the value defined by the return spring 84, the piston 35 is driven in the protruding direction against the return piston 88 and pushes the operation arm 23a. As a result, the motor swash plate 23 is tilted, and the return piston 88 comes into contact with the stepped portion 125a, so that the piston 35 cannot be extended any more, as shown in FIG. Is the largest. As described above, according to the pressure in the cylinder chamber 106, the motor swash plate 23 has the state shown in FIG. 4 in which the tilt angle is minimum (A1) and the state shown in FIG. 6 in which the tilt angle is maximum (A2). The tilting posture is controlled in two stages so as to be in one of the states.

Next, a circuit for supplying pressure oil to the piston 35 will be described. A piston drive oil passage 140 is formed at an appropriate position in the center section 10, and oil discharged from the charge pump 16 is guided to the piston drive oil passage 140 via an oil passage (not shown) (FIG. 5). Two valves of a two-position switching type, that is, a first valve 131 and a second valve 132 are connected to the piston drive oil passage 140, and a relief valve for regulating the oil pressure of the piston drive oil passage 140. 104 are connected and provided.

The first valve 131 has three ports of A, B, and C. Port A is connected to the piston driving oil passage 1.
40, port B as drain port, port C
Is connected to an oil passage 135 for tilting the motor swash plate 23 according to the load of the engine 2. In order to switch the first valve 131, a shuttle valve 141 is interposed between the two circuits 111 and 112 constituting the hydraulic oil circulation circuit of the HST.
The output of 41 is connected to the pilot circuit 145 of the first valve 131. Accordingly, the first circuit 111 has a high pressure when the vehicle is moving forward, and the second circuit 112 has a high pressure when the vehicle is moving backward. In any case, the pressure oil of the high pressure side circuit is guided to the pilot circuit 145. Has become.

The hydraulic pressure of the pilot circuit 145 is applied to the urging spring 133 attached to the first valve 131.
Is not exceeded, the port A is blocked, and the port B and the port C are communicated with each other, so that the pressure oil in the oil passage 135 is drained. On the other hand, when the hydraulic pressure of the pilot circuit 145 exceeds the spring force of the biasing spring 133, the first valve 131 is switched, and the port A is communicated with the port C, so that the charge pump 16 Pressure oil is supplied.

Further, the second valve 132 also has AB
C has three ports, with port A communicating with the piston drive oil passage 140 and port B communicating with the oil passage 135. The port C communicates with the cylinder chamber 106 that houses the piston 35 via an appropriate path. The second valve 132 is a manual valve, and is linked to the work mode switching lever 36 so that the valve 132 is switched by a switching operation of a work mode switching lever 36 provided at an appropriate position in the driver's seat. They are linked via a wire mechanism. The work mode switching lever 36 has two operation positions, that is, a "mowing mode" position m1 and a "running mode" position m2, so that these two operation positions can be arbitrarily switched.

The operation of the second valve 132 will be described. That is, when the work mode switching lever 36 is in the “mower mode” position m1, the second valve 132
Connects the port A and the port C to make the pressure in the cylinder chamber 106 equal to the pressure of the piston driving oil passage 140, and blocks the port C to close the oil passage 135. On the other hand, the work mode switching lever 3
6 is in the "running mode" position m2, the port A is blocked to stop the supply of pressure oil from the charge pump 16, while the port B and the port C are communicated,
The pressure in the cylinder chamber 106 is made equal to the pressure in the oil passage 135.

Next, how the traveling control device having the above configuration controls the mower tractor will be described with reference to different cases.

That is, when the work mode switching lever 36 is operated to the "mow mowing mode" position m1, the traveling control device is in the first mode, the mowing mode, and the engine 2, the pump swash plate 13, the motor The swash plate 23 is controlled to be in the following states. That is, as shown in FIGS. 5 and 7, the operation position of the accelerator lever 20 of the engine 2 is held by the friction mechanism 45, and the throttle arm 134 linked to the accelerator lever 20 via the wire 64 also responds thereto. Since the carburetor is maintained at the inclined position, the opening of the carburetor is constant, and the engine 2 maintains a constant rotational speed. Further, as shown in FIG. 7, the pump swash plate 13 is tilted according to the amount of depression of the shift pedal 27, and the gear ratio is changed by changing the discharge volume of the hydraulic pump 11. Also, as shown in FIG.
Between the piston drive oil passage 140 and the second valve 132
And the pressure in the cylinder chamber 106 becomes equal to the pressure in the piston drive oil passage 140. Here, the relief valve 104 and the like are set so that the pressure of the piston drive oil passage 140 is sufficiently large with respect to the spring force of the return spring 84 of the return piston 88.
The piston 35 is extended to the maximum and the motor swash plate 23 is extended.
Is fixed in a state where its tilt angle is the maximum angle A2.
Accordingly, the capacity of the hydraulic motor 21 is maximized, and the setting at the time of starting is a large reduction ratio in the entire HST 8.

That is, when the mower tractor performs mowing work in the workplace, it is necessary to drive the mower tractor at a low speed at a constant speed from the viewpoint of preventing mowing unevenness. In this regard, according to this configuration example, when the work mode switching lever 36 is set to the “work mode” position m1, the rotation speed of the engine 2 is constant as described above, and the motor swash plate 23 is also in a state of a large reduction ratio. Since the control is performed so as to be fixed, the vehicle speed is maintained at a constant low speed if the depression amount of the shift pedal 27 is constant, and appropriate control according to the above-described necessity is performed. . Further, since the control for changing the gear ratio according to the fluctuation of the load of the engine 2 as described later is not performed, the unevenness of the mowing marks is prevented, and the work is beautiful.

On the other hand, when the work mode switching lever 36 is operated to the "traveling mode" position m2, the traveling control device enters the traveling mode which is the second mode, and the engine 2, the pump swash plate 13, the motor swash plate 23 are controlled so as to be in the following states. That is, FIG.
As shown in FIG. 7, the operation position of the accelerator lever 20 is held by the friction mechanism 45, and the throttle arm 134 linked to the accelerator lever 20 via the wire 64 is also maintained at the corresponding inclined position.
The opening of the carburetor becomes constant, and the engine 2 maintains a constant rotational speed. The pump swash plate 13 is shown in FIG.
As shown in the figure, the hydraulic pump 11 is tilted in accordance with the operation position of the shift pedal 27, and the discharge volume of the hydraulic pump 11 is changed.

On the other hand, as for the motor swash plate 23, as shown in FIG.
Since 06 is drained by the first valve 131 and the second valve 132, the pressure in the cylinder chamber 106 becomes zero and the piston 35 is set to the most retracted position,
The motor swash plate 23 has a minimum tilt angle A1 as shown in FIG.
Is fixed. Accordingly, the capacity of the hydraulic motor 21 is minimized, and when the vehicle starts, the HST 8 as a whole has a small reduction ratio.

Here, the pilot circuit 145 for switching the first valve 131 includes a shuttle valve 1
41 connects the hydraulic oil circulation circuits 111 and 112 to the higher pressure side. Therefore, the hydraulic oil circulation circuit 1
When the circuit pressure on the high pressure side of the valves 11 and 112 increases and exceeds the value specified by the biasing spring 133 of the first valve 131, the first valve 131 switches as shown in FIG. And the port C are communicated with each other, and pressurized oil is supplied to the cylinder chamber 106 to extend and drive the piston 35 to the maximum. Therefore, the tilt angle of the motor swash plate 23 is set to the maximum angle A2 as shown in FIG. The reduction ratio of the entire HST8 is increased. On the other hand, when the circuit pressure on the high pressure side of the hydraulic oil circulation circuits 111 and 112 is lower than the value specified by the biasing spring 133, the oil passage 135 and the cylinder chamber are operated by the first valve 131 as shown in FIG. The pressure at 106 is reduced to zero, and the piston 35 retreats to the maximum, the tilt angle of the motor swash plate 23 is set to the minimum angle A1 as shown in FIG. 4, and the reduction ratio of the entire HST 8 is reduced.

Here, the relationship between the load of the engine 2 for driving the vehicle and the pressure of the hydraulic oil circulation circuits 111 and 112 will be described in relation to the control of the motor swash plate 23. That is, when the vehicle is running, various forms of resistance are generated on the axles 50L and 50R, and the main ones are road surface resistance, air resistance, acceleration resistance, and gradient resistance.
These resistances generated at 0R correspond to the drive train 3
0, and is input to the motor shaft 22 of the hydraulic motor 21 as a torque in a direction against driving the motor shaft 22. Therefore, when the above-described resistance is large, the force required to rotate the motor shaft 22 against the above-described torque also increases, and as a result, the hydraulic pressure required to drive the hydraulic motor 21 increases, and accordingly, During traveling of the vehicle, the greater the resistance input to the axles 50L and 50R, the greater the pressure of the first circuit 111 (or the second circuit 112). On the other hand, a large resistance means that the load on the engine 2 is large. Therefore, it can be said that the greater the pressure of the hydraulic oil circulation circuits 111 and 112, the greater the load acting on the engine 2.
In other words, the above-described control of detecting the pressure of the hydraulic oil circulation circuits 111 and 112 and tilting the motor swash plate 23 based on the detected pressure causes the motor swash plate 23 to change in accordance with the magnitude of the load on the engine 2. This is substantially the same as tilt control.

Therefore, according to this configuration, when the load on the engine 2 is large, the HST 8 is increased by increasing the tilt angle of the motor swash plate 23 and increasing the volume of the hydraulic motor 21.
As a whole, a large reduction ratio is used to prevent the engine 2 from being overloaded, while when the load of the engine 2 is small, the tilt angle of the motor swash plate 23 is made small and the volume of the hydraulic motor 21 is made small, so that the entire HST 8 is The control is performed so as to have a small reduction ratio, so that the performance of the engine 2 is efficiently exhibited.

That is, when the mower tractor travels on a road surface to move between work sites, it is desirable that the mower tractor be able to travel at a high speed from the viewpoint of shortening the traveling time, and frequently according to the surrounding conditions and the like. It is necessary to repeat starting and stopping,
In some cases, it is necessary to climb a hill. In this regard, according to this configuration example, when the work mode switching lever 36 is set to the above-described “running mode” position m2, the reduction ratio is changed according to the load on the engine 2 as described above. While satisfying the request, the engine 2 is controlled to be protected from overload and to perform its performance efficiently.

The above configuration example is merely an example, and another configuration example may be adopted. For example, the following configuration is also possible. FIG. 10 is a diagram showing a configuration of a travel control device of a second configuration example. FIG. 11 is a diagram illustrating a state in which the shift pedal is depressed in the lawn mowing mode in the travel control device of the second configuration example. FIG. 12 is a diagram showing a state of control when the load of the engine is small when the shift pedal is depressed as the driving mode. FIG. 13 shows a state where the load of the engine increases from the state of FIG. FIG. 6 is a diagram showing a state of control when the value exceeds.

That is, the travel control device according to the second configuration example includes a link mechanism and a motor swash plate control mechanism as in the first configuration example, and the link mechanism 100a is different from the link mechanism 100a of the first configuration example. And a mechanism for linking the shift pedal 27 and the carburetor. Other configurations, for example, the motor swash plate control mechanism 100b are exactly the same as those of the first configuration example.

Hereinafter, the configuration of the link mechanism 100a 'will be described. That is, as shown in FIG.
0a ', a link 5 is provided at the tip of the control arm 61 for tilting the pump swash plate 13.
1, an output arm 27a of the speed change pedal 27 is connected. Therefore, when the operator steps on the speed change pedal 27, the control arm 61 is tilted, and the pump swash plate 13 is tilted via the trunnion shaft 60 described above.
The volume of the hydraulic pump 11 is changed.

A transmission shaft 53 is fixed to the base end of the control arm 61 in addition to the trunnion shaft 60.
It is configured to rotate integrally with the control arm 61. A clutch slider is slidably disposed on the transmission shaft 53 via a spline.
The clutch device 54 is configured so as to be freely engageable and disengageable with respect to the intermediate shaft 55 that is arranged concentrically with the clutch shaft 54. The intermediate shaft 55
Is fixed to the arm member 57. The arm member 57 has two output arms, and one ends of the links 62 and 63 are pivotally connected to tips of the output arms.

A cam plate 58 is provided near the arm member 57. The cam plate 58 is rotatably supported at one end thereof, and has two concentric arc-shaped grooves formed around the center of rotation 58a. And
When the links 62 and 63 are connected to the concentric arc-shaped grooves, and the speed change pedal 27 is not depressed in a neutral state, the ends of the links 62 and 63 are respectively connected to the ends of the grooves as shown in FIG. It is configured to be located. One end of a wire 59 is locked at an appropriate position on the cam plate 58, and the other end of the wire 59 is connected to the throttle arm 134.

In this configuration, the clutch device 54
Is in contact with the transmission shaft 53 and the intermediate shaft 55, and when the front tread portion of the transmission pedal 27 is depressed, the link 51 and the control arm are connected to the transmission pedal 27 as shown in FIG. The transmission shaft 53 linked via 61 is rotated, the intermediate shaft 55 connected to the transmission shaft 53 is rotated, and the arm member 57 is rotated in the direction of arrow y shown in FIG. Therefore, the link 62 is connected to the cam plate 5
The link 63 slides inside the groove of the cam plate 58 while pulling one end of the groove 8 to rotate the cam plate 58. The rotated cam plate 58 pulls the wire 59 and tilts the throttle arm 134 to increase the carburetor opening and control the engine 2 to increase the rotation speed. When the tread portion on the rear side of the speed change pedal 27 is depressed, the direction in which the arm member 57 rotates is reversed, and the link 63 is connected to the cam plate 58.
One end of the groove is pulled to rotate the cam plate 58, and one end of the link 62 slides inside the groove of the cam plate 58. Therefore, also in this case, the cam plate 5
The cam plate 58 controls the cam plate 58 to pull the wire 59 and tilt the throttle arm 134 to increase the opening of the carburetor and increase the rotation speed of the engine 2. I do. Therefore, in both forward and reverse travels, control is performed to increase the rotation speed of the engine 2 in accordance with the amount of depression of the shift pedal 27.

Incidentally, of the two links 62 and 63,
The link 62 on the side pulling the cam plate 58 when the front tread portion of the speed change pedal 27 is depressed is connected to the groove on the side near the rotation center 58a of the cam plate 58, and the link 63 on the other side. Is connected to a groove farther from the rotation center 58a. Thus, when the speed change pedal 27 is depressed forward, the rotation center 58a of the cam plate 58
When the portion closer to the cam plate 58 is pulled by the link 62 and the step is stepped on the rear side, the portion farther from the rotation center 58a of the cam plate 58 is pulled by the link 63. Therefore, for the same stepping amount, the cam plate 58 is more depressed when depressed rearward than when depressed forward.
Is small, the amount of pulling of the wire 59 is reduced accordingly, and the amount of tilt of the throttle arm 134 is reduced. In other words, this configuration suppresses the degree of increase in the rotation speed of the engine 2 in accordance with the amount of depression of the speed change pedal 27 during reverse travel. Generally, it is rare that the vehicle is suddenly accelerated or climbed uphill while moving backward. Therefore, the above-described control for suppressing an increase in the number of revolutions of the engine 2 when the vehicle is moving backward is reasonable. Useful from.

The throttle arm 134 has a wire 6
The other end of the wire 64 is connected to the output arm 20 a of the accelerator lever 20. Therefore, when the accelerator lever 20 is tilted, the throttle arm 134 is tilted and controlled according to the operating position, and the fuel injection amount of the carburetor is changed to change the rotation speed of the engine 2. The accelerator lever 20 is provided with a return spring 52 for urging the accelerator lever 20 to the idling position, and generates a frictional force against the urging force of the return spring 52 to operate the accelerator lever 20. A friction mechanism 45 for holding the position is provided at an appropriate position of the accelerator lever 20.

Further, the motor swash plate control mechanism 100b
The work mode switching lever 36 for switching the second valve 132 is also configured to be linked to the clutch device 54 and the friction mechanism 45. When the lever 36 is operated, the second valve 132 At the same time as 132 is switched, the states of the clutch device 54 and the friction mechanism 45 are switched.

Next, how the traveling control device having the above-described configuration controls the mower tractor will be described with reference to different cases.

That is, when the work mode switching lever 36 is operated to the "mow mowing mode" position m1, the traveling control device enters the first mode, the mowing mode, and the engine 2, the pump swash plate 13, the motor The swash plate 23 is controlled to be in the following states. That is, as shown in FIG. 11, the friction mechanism 45 of the engine 2 is turned on.
As a result, the operation position of the accelerator lever 20 is maintained, and the throttle arm 134 linked to the accelerator lever 20 via the wire 64 is also maintained at the corresponding inclined position. As a result, the opening of the carburetor becomes constant and the engine 2
Maintains a constant rotation speed. The clutch device 54
Since the engagement is released, the control for tilting the throttle arm 134 in accordance with the shift pedal 27 is not performed. Further, as shown in FIG. 11, the pump swash plate 13 is tilted in accordance with the operation position of the shift pedal 27,
The gear ratio is changed by changing the discharge volume of the hydraulic pump 11. Further, since the second valve 132 is in a state as shown in FIG. 11, the motor swash plate 23 has the same configuration as the motor swash plate control mechanism 100b in the first configuration example. The tilt angle is fixed at the maximum. Therefore, the capacity of the hydraulic motor 21 is maximized, and the entire HST 8 has a large reduction ratio.

That is, when the mower tractor performs mowing work in the workplace, it is necessary to drive the mower tractor at a low speed at a constant speed from the viewpoint of preventing mowing unevenness. In this regard, according to this configuration example, when the work mode switching lever 36 is set to the “work mode” position m1, the rotation speed of the engine 2 is constant as described above, and the motor swash plate 23 is also in a state of a large reduction ratio. Since the control is performed so as to be fixed, the vehicle speed is maintained at a constant low speed if the depression amount of the shift pedal 27 is constant, and appropriate control according to the above-described necessity is performed. . In addition, since the control for changing the gear ratio according to the change in the load of the engine 2 is not performed,
The unevenness of mowing marks is prevented, and the work is beautiful.

On the other hand, when the work mode switching lever 36 is operated to the “travel mode” position m2, the travel control device
The engine 2, the pump swash plate 13, and the motor swash plate 23 are controlled to be in the following states, respectively. That is, engine 2
As shown in FIG. 12, the friction mechanism is forcibly turned off and the accelerator lever 20 is turned off.
Is released from the frictional engagement state. On the other hand, since the clutch device 54 is in the engaged state, the throttle arm 134 is tilted in accordance with the amount of depression of the shift pedal 27, and control is performed to freely change the rotation speed of the engine 2. Further, as shown in FIG. 12, the pump swash plate 13 is tilted according to the operation position of the shift pedal 27, and the discharge volume of the hydraulic pump 11 is changed. On the other hand, the second valve 1
32 is switched from the state shown in FIG. 11 to the state shown in FIG. 12, so that the same control as that of the motor swash plate control mechanism 100b in the first configuration example is performed on the motor swash plate 23. . That is, when the load on the engine is small, the piston 35 is moved backward to the maximum as shown in FIG. 12 to tilt the motor swash plate 23 so that the entire HST 8 has a small reduction ratio. When the value exceeds the value, the first valve 131 is switched as shown in FIG. 13 to extend the piston 35 to the maximum, and the motor swash plate 23 is tilted so that the entire HST 8 has a large reduction ratio.

Therefore, according to this configuration, when the load on the engine 2 is large, the HST 8 is increased by increasing the tilt angle of the motor swash plate 23 and increasing the volume of the hydraulic motor 21.
As a whole, a large reduction ratio is used to prevent the engine 2 from being overloaded, while when the load of the engine 2 is small, the tilt angle of the motor swash plate 23 is made small and the volume of the hydraulic motor 21 is made small, so that the entire HST 8 is made. The control is performed so as to have a small reduction ratio, so that the performance of the engine 2 is efficiently exhibited. Further, when the shift pedal 27 is depressed, the tilt angle of the pump swash plate 13 is changed to a small reduction ratio, and the rotation speed of the engine 2 is also increased. Therefore, the output increase of the engine 2 and the output increase of the HST 8 are combined. As a result, the speed of the vehicle is increased. This means that the acceleration performance of the vehicle is further improved.

That is, when the mower tractor travels on a road surface to move between work sites, it is desirable that the mower tractor be able to travel at a high speed from the viewpoint of shortening the travel time. The suspension must be repeated,
In some cases, it is necessary to perform climbing. In this regard,
According to the present configuration example, when the work mode switching lever 36 is set to the above-mentioned “running mode” position m2, the output of the engine 2 is controlled to be changed together with the gear ratio according to the shift pedal, and the load of the engine 2 is reduced. Accordingly, the reduction ratio of HST8 is changed. Therefore, while satisfying the above requirements, the engine 2 can be efficiently used while protecting the engine 2 from overload, and the vehicle can be run more lightly.

The embodiments of the present invention have been described above. However, the technical scope of the present invention is not limited to the above-described embodiments, and the present invention can be clearly understood from the matters described in the present specification and the drawings. It covers a whole range of technical ideas that are truly intended.

[0070]

The present invention is configured as described above.
The following effects are obtained.

That is, as set forth in claim 1, there is provided an engine and a hydraulic pump interlocked with the engine.
A hydraulic motor driven by receiving pressure oil from the hydraulic pump, wherein the volume of the pump swash plate can be changed continuously by changing the angle of the pump swash plate; A travel control device provided in a vehicle including at least a vehicle whose volume can be continuously changed and an axle interlocked with the hydraulic motor,
a) a first mode in which the angle of the pump swash plate is changed in accordance with an operation position of a shift operation means provided in a vehicle to fix the angle of the motor swash plate; Changing the angle according to the operation position of the shift operation means,
A second mode for changing the angle of the motor swash plate in accordance with the load of the engine, and furthermore, it is possible to arbitrarily switch between the first mode and the second mode. The first mode that can obtain a stable running speed regardless of the engine load,
By changing the gear ratio according to the load of the engine, a second mode can be provided in which the engine can be protected from overload even during sudden acceleration or climbing a steep slope. In addition, since these two modes can be switched arbitrarily, by appropriately switching and using the mode in accordance with a change in the use or purpose of the vehicle, it is possible to perform a control suitable for the usage mode of the vehicle. is there. For example, when the travel control device of the present invention is applied to a mower tractor, when mowing is performed, the first mode is used to prevent the mowing unevenness while keeping the traveling speed constant, while moving between work sites. As a second mode, when the engine load increases during sudden acceleration or climbing a slope, the engine is automatically decelerated to protect the engine, and when traveling on a flat road, the engine load is small. Increase the speed and make the most of the engine capacity,
This makes it possible to use the vehicle in such a manner that the vehicle travels at high speed to reduce the traveling time.

According to a second aspect of the present invention, there is provided an engine and a hydraulic pump interlocked with the engine, wherein the volume can be continuously changed by changing the angle of the pump swash plate. A hydraulic motor driven by receiving the hydraulic oil, the volume of which can be continuously changed by changing the angle of the motor swash plate, and an axle interlocked with the hydraulic motor. In a travel control device provided in a vehicle, a) changing an angle of the pump swash plate in accordance with an operation position of a shift operation means provided in the vehicle to fix an angle of the motor swash plate; And b) changing the number of revolutions of the engine according to the operation position of the speed change operation means, and changing the angle of the pump swash plate according to the operation position of the speed change operation means. Corner of The second mode is changed according to the load of the engine, and further, the engine is configured to be able to arbitrarily switch between the first mode and the second mode. The first mode, in which a stable running speed can be obtained regardless of the load, and the gear ratio is changed according to the load of the engine to prevent engine troubles while efficiently using its ability, By changing the gear ratio and the number of revolutions of the engine in accordance with the operation position of the means, it is possible to additionally provide a second mode that makes it easier to accelerate suddenly or climb a steep slope. In addition, since these two modes can be switched arbitrarily, by appropriately switching and using the mode in accordance with a change in the use or purpose of the vehicle, it is possible to perform a control suitable for the usage mode of the vehicle. is there. For example, when the travel control device of the present invention is applied to a mower tractor, when mowing is performed, the first mode is used to prevent the mowing unevenness while keeping the traveling speed constant, while moving between work sites. As a second mode, when the engine load increases during sudden acceleration or climbing a slope, the engine is automatically decelerated to protect the engine, and when traveling on a flat road, the engine load is small. It is possible to use the engine in such a manner that the speed is increased so that the engine performance is efficiently exhibited and the traveling time is reduced by performing high-speed traveling. In the second mode, control is performed to change both the speed ratio and the engine speed in accordance with the operation position of the speed change operation means. The increase in the output of the transmission and the increase in the engine output are combined and superimposed to increase the speed of the vehicle.
As a result, for example, when climbing a steep slope or the like, the vehicle can climb up while strongly accelerating, and it is possible to provide the operator with a light traveling feeling close to the feeling of a car.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram showing a power transmission configuration of a vehicle including a travel control device according to the present invention.

FIG. 2 is a plan view, partly in section, showing the configuration of an axle drive device provided in the vehicle.

FIG. 3 is a sectional view taken along the line AA in FIG. 2;

FIG. 4 is a sectional view taken along a line BB in FIG. 2;

FIG. 5 is a diagram showing a first configuration example of a travel control device of the present invention.

FIG. 6 is a view showing a state in which a piston is driven from the state of FIG. 4 and a motor swash plate is tilted.

FIG. 7 is a diagram illustrating a state in which the shift pedal is depressed in the lawn mowing mode in the travel control device of the first configuration example.

FIG. 8 is a diagram showing a state of control when the load on the engine is small when the shift pedal is depressed in the traveling mode.

FIG. 9 is a view showing a state of control when the load on the engine increases from a state shown in FIG. 8 and exceeds a predetermined value.

FIG. 10 is a diagram showing a configuration of a travel control device of a second configuration example.

FIG. 11 is a diagram showing a state in which a shift pedal is depressed in a lawn mowing mode in the travel control device of the second configuration example.

FIG. 12 is a diagram showing a state of control when the load on the engine is small when the shift pedal is depressed in the traveling mode.

FIG. 13 is a view showing a state of control when the load on the engine increases from a state shown in FIG. 12 and exceeds a predetermined value.

[Explanation of symbols]

 2 Engine 11 Hydraulic pump 13 Pump swash plate 21 Hydraulic motor 23 Motor swash plate 27 Speed change pedal (speed change operation means) 100 Travel control device 50L / 50R Axle

Claims (2)

[Claims] An engine and a hydraulic pump interlocked with the engine, the volume of which can be changed steplessly by changing the angle of a pump swash plate, and a hydraulic oil received from the hydraulic pump. A hydraulic motor driven by a hydraulic motor, the volume of which can be changed continuously by changing the angle of a motor swash plate, and an axle interlocked with the hydraulic motor. In the travel control device, a) a first mode in which an angle of the pump swash plate is changed according to an operation position of a shift operation means provided in a vehicle to fix an angle of the motor swash plate; A second mode in which the angle of the pump swash plate is changed in accordance with the operation position of the shift operation means, and the angle of the motor swash plate is changed in accordance with the load on the engine. The first Characterized by being configured to be able to switch between over de and the second mode arbitrarily, travel control device. 2. An engine and a hydraulic pump interlockingly connected to the engine, wherein the volume can be continuously changed by changing an angle of a pump swash plate, and a pressure oil from the hydraulic pump is received. A hydraulic motor driven by a hydraulic motor, the volume of which can be changed continuously by changing the angle of a motor swash plate, and an axle interlocked with the hydraulic motor. In the travel control device, a) a first mode in which an angle of the pump swash plate is changed according to an operation position of a shift operation means provided in a vehicle to fix an angle of the motor swash plate; The number of revolutions of the engine is changed according to the operation position of the speed change operation means, the angle of the pump swash plate is changed according to the operation position of the speed change operation means, and the angle of the motor swash plate is changed. Engine A second mode that changes according to the load of the vehicle, and further configured to be able to arbitrarily switch between the first mode and the second mode. Control device.