JPH0327413B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a device for maintaining a constant speed state in a tractor equipped with a hydraulic continuously variable transmission.

<Conventional technology> In general, tractors equipped with a hydraulic continuously variable transmission (hereinafter abbreviated as HST) are operated by switching between forward and reverse directions and changing gears by depressing a pedal. Typically, the pedal is always provided with spring pressure to return it to the neutral position.

However, as shown in Figure 16, the return torque generated from the HST to the neutral position is positive (in the neutral direction toward the deceleration side) due to the load acting on the HST (HST oil pressure) and the input rotation speed. (moment that tries to return the speed) or negative (moment that works toward the acceleration side), and as a result, the pressure force on the pedal also changes. Moreover, in the case of a tractor, it is normal to perform load work while moving forward at a constant speed.

<Problems to be Solved by the Invention> Nevertheless, in the past, a constant state of forward speed was maintained only by the amount of depression of the pedal, so the state of maintaining the forward speed was extremely unstable. This is unavoidable, and there are problems in that it causes fatigue during driving and that erroneous operations are also likely to occur.

In this regard, in order to hold the HST in the forward transmission state, a device for swinging the operating lever of the holding mechanism to the operating position is known as Utility Model Application No. 59-192430. If you do not press the button, move the operating lever 19 to the operating position (ON).
It cannot be operated by swinging. In other words, constant speed positioning is not performed by manual lever operation in advance independently of the pressing operation of the speed change pedal 14, so constant speed positioning cannot be performed accurately and easily. .

Furthermore, when the operating lever 19 is switched to the release position (OFF), the forward speed must be maintained at a constant state depending on the amount of depression of the pedal 14, and as a result, the above-mentioned problem still remains. arise.

Furthermore, in the above-mentioned known device, the front
In regulating the limit of depression in the backward direction, it is necessary to install a pair of stoppers 16a and 16b separate from the holding mechanism 17 and the swing arm 12, which makes the entire mechanism extremely complicated and expensive. The safety of the suspension is also disadvantageous.

<Means for Solving the Problems> The present invention is intended to solve these problems, and for this purpose, the operating arm of the hydraulic continuously variable transmission and its rotation control pedal are pivotally supported. Connect and
A tractor equipped with a hydraulic continuously variable transmission that can switch between forward and reverse directions and change each gear by depressing the pedal, and the operating arm is always given elastic force to return to the neutral state. In this case, a lever shaft that can be rotated about a horizontal axis is installed horizontally through the tractor body, and while the lever shaft is in a fixed state substantially parallel to the lever shaft, the pedal shaft, which is the swinging fulcrum of the pedal, is also connected from the tractor body. ,
A fulcrum shaft, which is the center of rotation of the constant speed setting cam plate, is separately provided in a protruding manner, and a cam pin integrally protruded from the pedal and a fitting notch formed in the constant speed setting cam plate are provided. , The constant speed setting cam plates can only be rotated from the neutral position in the forward operation direction, and when they are rotated in the deceleration direction in the forward state, they lock each other and set the constant speed. The pedal returns and rotates together with the cam plate, and when the constant speed setting cam plate is stopped and held in the neutral position, the pedal is released from the constant speed setting cam plate and rotates forward and backward independently.
The fixed speed setting cam plate is pivotally connected to one end of the lever shaft by a connecting rod, and the other end of the lever shaft is also connected to the other end of the lever shaft. A manually operated constant speed setting lever and a brake cam having an inclined cam surface are integrally fixed to the part, so that the constant speed setting cam plate can be rotated by the constant speed setting lever. A slide guide shaft protruding from the tractor body in a fixed state substantially parallel to the lever shaft is passed through the brake cam of the constant speed setting lever in an intersecting manner, and the inclined cam surface of the brake cam is fixed. A brake which applies constant braking elastic force to the brake cam is loosely fitted onto the guide shaft so that it can slide forward and backward, and an engagement elongated hole for receiving the guide shaft is opened through the brake cam. When the constant speed setting lever is rotated in the speed increasing direction in the forward state, the brake element relatively slides down the inclined cam surface of the brake cam that rotates together with the constant speed setting lever, and the brake cam is rotated in the forward direction as well. When the brake cam is rotated in the deceleration direction, the brake cam is arranged as an arc-shaped opening that can relatively slide up the inclined cam surface of the brake cam, thereby reducing the constant speed setting lever. The elastic force of the braking applied to the vehicle is set in such a manner that it acts more excessively during a rotational operation in the direction of deceleration than when the rotational force is applied in the direction of acceleration. That is.

<Example> Hereinafter, the specific configuration of the present invention will be described in detail based on the illustrated example. FIGS. 1 to 6 show the neutral state of the HST operation pedal, T is the tractor body, The transmission case 10
HST is installed in the transmission system to the rear wheels inside the
(not shown) is incorporated. 11 is that HST
12 is a control shaft fitted and integrated with the operating shaft 11; 13 is a transmission case 1;
The control shaft 12 is a base plate fixedly attached to the right flank of the robot 0, and the control shaft 12 is led out through the base plate, so that the rotation of the operating shaft 11 can be controlled from the outside.

Reference numeral 14 denotes a flat plate-shaped operating arm fixed to the outer end of the control shaft 12, and this has a pair of upper and lower roller shafts 15 and 16 facing each other across the control shaft 12, which is the center of rotation. , are planted and fixed horizontally, and both roller shafts 1
5 and 16 further include idle rollers 1 for returning to neutrality.
7 and 18 are also fitted together. Regarding this point,
The floating roller 17 in the upper position has a mutual distance H1 between the roller shaft 15 and the control shaft 12,
Like the roller shaft 16 of the floating roller 18 at the lower position, the dimension is set to be longer than the mutual distance H2 between the control shaft 12 and the adjustment lever that is pulled by the expansion/contraction amount of the neutral return coil spring, which will be described later. The amount of rocking is kept substantially the same during the forward F operation and the reverse R operation.

Reference numeral 19 denotes an adjustment lever for returning to neutrality, which is bent into an L-shape as a whole, and has one half portion 19a that stands upright, and the other half portion 19b that extends rearward from its lower end almost horizontally. The lever shaft 20 is pivotally supported around a lever shaft 20 which is integrally protruded and fixed from the base plate 13 at the boundary position between the base plate 13 and the base plate 13. Reference numeral 21 denotes a tension coil spring for returning to neutral, which always presses and urges the middle half 19a of the adjustment lever 19 forward. The rear end of the other half portion 19b is connected and suspended between the upper and lower sides.

Further, 23 indicates both the above-mentioned floating rollers 17 and 18.
This adjustment arm is inserted between the front and rear of the half part 19a of the adjustment lever 19, and its lower end is attached to a mid-height position of the half part 19a by a pivot bolt 24. Therefore, the upper end part can freely move forward around the pivot bolt 24 while bearing the pressing force of the coil spring 21. When neutral N, a pair of upper and lower idle rollers 17,
18 are adapted to come into contact with the front surface of the adjustment arm 23 equally at once. Reference numeral 25 denotes an adjustment screw for adjusting the contact state in advance, and is a half portion 19a of the adjustment lever 19.
It is attached and held at the upper end position, and by moving it forward and backward, the adjustment arm 23 is moved to the adjustment lever 1.
9 can be pressed separately.

In that case, as is clear from FIG. 3, the mutual distance Y1 between the lever shaft 20, which forms the swinging fulcrum of the adjustment lever 19, and the roller shaft 15 of the floating roller 17 at the upper position is the same as that between the lever shaft 20 and the lower position. The roller shaft 16 of the floating roller 18 in
The single neutral return coil spring 21
While also serving as
It is configured so that it acts weakly on the floating roller 17 at the upper position and strongly acts on the floating roller 18 at the lower position.

Further, reference numeral 26 denotes a pedal shaft that extends horizontally in parallel with the control shaft 12 of the HST and the lever shaft 20 of the adjustment lever 19, and is integrally provided to protrude from the base plate 13 at a position in front of the operating arm 14. Before P swings around the pedal shaft 26,
This is a pedal for switching reverse movement, and the front position of the pedal is depressed downward when moving forward (F), and the rear position of the pedal is depressed downward when moving backward (R).

This pedal P includes a mounting barrel 27 that is loosely fitted onto the pedal shaft 26, a tread plate 29 that is fixed and integrated to the outside of the tip of the barrel 27 with a required number of bolts and nuts 28, and a body of the barrel 27. It consists of a swing plate 30 that is fitted and fixed in the middle, and is attached to the pedal shaft 26 in a manner that prevents it from coming off. Moreover, a pair of front and rear projecting ears 31 and 32 are provided at the upper end of the swing plate 30, and a cam pin 33 is provided from the rear ear piece 32.
is also projected inward.

On the other hand, the front lug 31 and the upper part of the operating arm 14 are pivotally connected to each other by a connecting rod 34, so that the cam pin 33 can be properly positioned at a specified position on a constant speed setting cam plate, which will be described later. In addition, the working length of the connecting rod 34 can be adjusted in advance to a longer or shorter length. 35 and 36 are pivot pins that connect the front and rear ends of the connecting rod 34 to the swing plate 30 and the operating arm 14, respectively; 37 is an oil damper that maintains an appropriate return speed to the neutral N position; A mounting bracket 38 fixed to the case 10 and an actuation arm 1
It is supported in a substantially horizontal state between the front and rear ends of the upper end of 4.

Therefore, when operating the forward movement F by depressing the pedal P, the upper part of the actuating arm 14 is pulled forward by the connecting rod 34 and is pivoted at the lower position of the actuating arm 14, as shown in FIG. Only the free rollers 18 that are present come into contact with the adjusting arm 23 . Conversely, when pressing the reverse R button, the 8th
As shown, the upper part of the actuating arm 14 is now pushed rearward by the connecting rod 34, so that only another idler roller 17, which is pivoted in the upper position of the actuating arm 14, comes into contact with the adjusting arm 23. Therefore, in either the forward or reverse operation, the coil spring 21 applies pressure to return the vehicle to the neutral direction.

At this time, since the cam pin 33 is also integrally attached to the swing plate 30 of the pedal P as described above, the cam pin 33 rotates along with the rocking motion caused by the depression of the pedal P. It is clear that the motor moves in an arc with the distance between the pedal shaft 26 and the pedal shaft 26 being a radius of a constant length.

In the present invention, in addition to the above-mentioned configuration in which the pedal P can be used to switch between forward and reverse travel and to change the respective speeds, the forward F speed can be manually operated using a separate constant speed setting lever, and the pedal P Even when the pedal pressure on the lever is released, the lever is configured to automatically maintain a preset constant speed state in a stable manner.

That is, in FIGS. 9 to 11 showing the configuration, numeral 39 is a constant speed setting lever that is manually operated from the driver's seat, and the mounting boss 40 at the base end of the lever extends through the steering support 41 of the tractor body T. The lever shaft 42 is fitted onto one end (left end) of the lever shaft 42, and is fixed by a spring pin 43 so as to be able to rotate together. 44 is the lever shaft 4
It is a bearing pipe that rotatably supports the steering support 2, and is fixedly suspended horizontally through the steering support 41. A steering support pipe 45 is integrally erected from the center of the steering support 41, into which the steering handle shaft is inserted. The steering support 41 has a hollow box shape,
It is fixedly installed on the clutch housing 46 of the tractor body T. Note that 47 is an operation guide for the constant speed setting lever 39.

Reference numeral 48 denotes a brake cam that continuously projects downward from the mounting boss 40 of the constant speed setting lever 39, and is made of metal so that it forms an approximately right triangle when viewed from the front and back direction of the tractor body T. The oblique side, which is plastically deformed from the plate and is exposed at the outer position, is determined so that it can act as a flat inclined cam surface 48a that gradually shifts toward the inner position as it goes upward. However, the inclination angle of the inclined cam surface 48a can be appropriately selected.

Reference numeral 49 designates an engagement elongated hole for receiving a guide support shaft, which is opened through the brake cam 48 including the inclined cam surface 48a thereof, and draws an arcuate locus of a constant radius with the lever shaft 42 as a pivot point. Moreover,
When viewed from the left and right sides of the tractor body T, these openings are arranged in an arc shape that is tilted forward and upward. In other words, as is particularly clear from FIG. 9, the opening front end 49a of the engagement elongated hole 49 is set to be located a certain distance L higher than the opening rear end 49b. .

50 is approximately parallel to the lever shaft 42,
This is a slide guide support shaft that projects laterally and horizontally from the steering support 41, and passes through the engaging elongated hole 49 of the brake cam 48 in an intersecting manner.
In this regard, in the figure, the guide support shaft 50 is connected to the lever shaft 4.
2, the guide support shaft 50 itself is in the form of a bolt, and its proximal threaded portion is fixed and integrated into the flank of the steering support 41. It is screwed into the boss 51 in a fixed state. 52 is a brake that slides forward and backward along its axial direction by being loosely fitted to the guide support shaft 50, and has a substantially hemispherical bowl shape, and its open surface is similar to that of the brake cam 48. It faces the inclined cam surface 48a.

Reference numeral 53 indicates a friction plate inserted between the two facing each other, and 54 indicates a brake cam 4 as well.
A friction plate is interposed between the vertical surface 48b of No. 8 and the receiving boss 51, and both serve to prevent wear. 55 is a compression coil spring that always applies a braking force to the inclined cam surface 48a of the brake cam 48;
It is wound around the guide support shaft 50 while being located between the brake element 52 and the spring presser foot 56.
Reference numeral 57 designates a double nut for positioning and fixing the presser foot 56, and is screwed onto the threaded end portion of the guide support shaft 50. Therefore, by moving the nut 57 forward and backward, it is possible to adjust the strength of the braking bullet force in advance.

By rotating the constant speed setting lever 39 integrally with the lever shaft 42 so as to tilt it forward A, the speed of the HST can be increased according to the amount of rotation, and vice versa. By operating the rotation as if folding it down, the amount of rotation is the same.
Although it is specified that HST can be slowed down,
Based on the above configuration, when the constant speed setting lever 39 is rotated in the speed increasing direction A, the 12th and 13th
Brake cam 48 rotates integrally with this as shown in the figure.
The brake 52 on the guide support shaft 50 acts as if it slides down the inclined cam surface 48a relative to the guide shaft 50,
The braking force exerted by the coil spring 55 is weakened.

On the other hand, when the constant speed setting lever 39 is rotated in the deceleration direction B, as shown in FIGS. It will slide up the surface 48a, and as a result, the coil spring 55 will be forcibly compressed, thereby increasing the braking force. As a result, the constant speed state during the forward movement F of the HST is stably maintained. Note that, as will be described later, the constant speed setting lever 39 cannot be operated during reverse R.

Furthermore, referring to FIGS. 3 to 5, reference numeral 58 denotes a rotating arm that is fixedly integrated with the other end (right end) of the lever shaft 42, and is connected by a constant speed setting cam plate 59 and a connecting rod 60. It is pivotally connected. Therefore, the cam plate 59 can be rotated by the lever 39. 61 is the connecting rod 60
A pivot pin between the upper end and the tip of the rotating arm 58, 62 is a pivot pin between the lower end of the connecting rod 60 and the front upper end of the cam plate 59, and 63 is interposed in the middle of the connecting rod 60. This is a turnbuckle with a cylindrical shape, by means of which the working length of the connecting rod 60 can be preadjusted.

The constant speed setting cam plate 59 is interposed between the swing plate 30 of the pedal P and the base plate 13. 64 is the pedal shaft 26
At the upper position, it is a fulcrum shaft that integrally projects from the base plate 13 so as to be horizontally suspended parallel to the pedal shaft 26, and the constant speed setting cam plate 59 is rotatable around this fulcrum shaft 64. To,
Its substantially upper center position is fitted to the fulcrum shaft 64. In that case, the constant speed setting cam plate 59 can be rotated in conjunction with the constant speed setting lever 39 described above from the neutral N state of the HST toward the forward F operating direction, but conversely, it can be rotated in the reverse R operating direction. It is assembled to the cam pin 33 of the pedal P and the pedal 26 in the following manner so that it cannot be rotated until the pedal P is turned.

That is, 65 is a fitting notch formed in the rear half of the cam plate 59 in order to operatively connect the constant speed setting cam plate 59 with the pedal P, and the contour shape of the opening is particularly clear from FIG. As shown, a semicircular surrounding surface S1 corresponding to the substantially semicircular circumferential surface of the mounting shaft cylinder 27 in the pedal P, and an arcuate cam pin guide surface S2 parallel to the arcuate trajectory of the cam pin 33.
and the guide surface S2 and the surrounding surface S1 are made continuous,
and a constant speed setting cam plate 59 centered on the fulcrum shaft 64
The circular arc surface S3, which can be the radius of rotation of the cam pin 33, and the circular arc surface S3 that protrudes outward from the opening from the arc locus of the circular movement of the cam pin 33, and are removably engaged with the cam pin 33. It is divided into a cam pin engaging/disengaging surface S4 and a so-called step surface S5 which connects the cam pin engaging/disengaging surface S4 and the surrounding surface S1.

Moreover, the boundary step between the cam pin guide surface S2 and the cam pin engaging/disengaging surface S4 in such a fitting notch 65 is the same as the cam pin 3 when the pedal P is in the neutral position N.
This is predetermined as the designated position of No. 3. Then, move the constant speed setting lever 39 described above to the ninth position.
As shown in the figure, the opening rear end 49b of the engagement elongated hole 49 corresponds to the neutral N operating state.
When the rear part of the pedal P is depressed as shown in FIG. 8 while the pedal is stopped at the set position, the cam pin 33 is guided along the cam pin guide surface S2 of the fitting notch 65 and moves in a constant arc. When the cam pin 33 rotates toward the operating direction of the reverse R by the range W1 and the front position of the pedal P is depressed as shown in FIG. The rotational change is made so that the constant arc movement range W2 is directed toward the forward movement direction F while being separated from the movement direction.

Further, the constant speed setting lever 39 is rotated from the corresponding position of the neutral N state to the forward direction A as shown in FIG. From the neutral N state,
When rotating the forward F by an arbitrary amount in the direction of operation as shown in FIG. 15, the speed of the forward F is increased by the arbitrary rotation amount. When the pedal pressure is released, the cam pin 33 of the pedal P is moved against the cam pin engaging/disengaging surface S4 of the fitting notch 65 whose angle has changed based on the constant speed setting cam plate 59 which has already rotated around the fulcrum shaft 64. As a result, even if the coil spring 21 receives pressure to return to the neutral direction, it is locked in a stable fixed state in which it does not naturally return and rotate.

Moreover, in this case, the brake 52, which applies a braking elastic force to the brake cam 48 of the constant speed setting lever 39, is directed toward the rear B where the brake cam 48 is decelerating, and the inclined cam surface of the brake cam 48 is 48a, and the coil spring 55 exerts a pressing force that strengthens the braking, so that the forward movement F The constant speed state during operation is automatically and extremely stably fixed and maintained. Incidentally, until the cam pin 33 of the pedal P is engaged with the cam pin engaging/disengaging surface S4 of the constant speed setting cam plate 59, while receiving the braking action from the brake element 52, the coil spring 21 is relatively Upon receiving strong return pressure, the pedal P automatically returns to the position specified by the constant speed setting lever 39 and rotates.

Furthermore, as shown in FIG. 15, there is still a cam pin between the specified constant speed position held in advance by the constant speed setting cam plate 59 and lever 39 and the maximum speed end position. 33, if the allowable speed increase range X for arc movement remains, the pedal P can be pressed deeper independently of the cam plate 59 and the lever 39 to freely increase the speed. It is possible.

Regardless of whether or not the allowable speed increase range The cam plate 59 and the lever 39 remain engaged with the cam pin engaging/disengaging surface S4, and the constant speed setting lever 39 remains under the elastic force of braking by the brake element 52, and the cam plate 59 and the lever 39 are integrally and forcefully engaged with the pedal P. As a result, the forward speed is reduced by an arbitrary amount corresponding to the depression.

As soon as the deceleration progresses and the neutral N position is reached, the constant speed setting cam plate 59 and lever 39 are locked in a stopped state in which they cannot rotate in the reverse R operation direction. From that neutral state,
As described above with reference to FIG. 8, by further depressing the rear position of the pedal P, the gear change operation for reverse R can be performed.

A pedal P assembled so as to be able to operate in conjunction with such a constant speed setting cam plate 59 and lever 39.
As described above, since the pedal P is pivotally connected to the operating arm 14 that rotates the operating shaft 11 of the HST by the connecting rod 34, the front and rear positions of the pedal P must be depressed and operated separately. As a result, the HST can be controlled to be maintained in the forward F and reverse R shift states by an arbitrary amount corresponding to the depression.

In addition, especially for tractors that are normally used for load work in forward F, the HST installed on this tractor
The elastic force for returning to the neutral position, which is a characteristic of
By manual operation in step 9, it is possible to keep the door locked and locked at all times.

<Effects of the Invention> As described above, in the present invention, the operating arm 14 of the hydraulic continuously variable transmission and its rotation control pedal P are pivotally connected, and when the pedal P is depressed,
In a tractor equipped with a hydraulic continuously variable transmission, which is capable of switching between forward and reverse movement and each gear change, and which constantly applies elastic pressure to return to a neutral state on its operating arm 14, the tractor body T A lever shaft 42 that can be rotated around a horizontal axis is passed through and horizontally mounted, and in a fixed state substantially parallel to the lever shaft 42, the pedal shaft 26, which is the swinging fulcrum of the pedal P, is also connected from the tractor body T. , a fulcrum shaft 64, which is the center of rotation of the constant speed setting cam plate 59, is provided separately, and
Cam pin 3 integrally protrudes from the pedal P
3 and a fitting notch 65 formed as an opening in the constant speed setting cam plate 59, the constant speed setting cam plate 59 can be rotated only when the constant speed setting cam plate 59 is directed from the neutral N position toward the forward F operation direction, and When the pedal P is rotated in the deceleration direction B in the forward movement F state, the pedals P are rotated back together with the constant speed setting cam plate 59 as they engage with each other.
Similarly, when the constant speed setting cam plate 59 is stopped and held at the neutral N position, the pedal P is released from the constant speed setting cam plate 59 and can independently rotate freely in both the forward and reverse depressing operation directions. At the same time, the constant speed setting cam plate 59 is pivotally connected to one end of the lever shaft 42 by a connecting rod 60, and a manually operated constant speed setting cam plate 59 is connected to the other end of the lever shaft 42. A lever 39 and a brake cam 48 having an inclined cam surface 48a are integrally fixed, and the constant speed setting lever 39 controls the constant speed setting cam plate 5.
A slide guide support shaft 50, which also projects from the tractor body in a fixed state substantially parallel to the lever shaft 42, intersects with the brake cam 48 of the constant speed setting lever 39. A brake element 52 which is passed through the brake cam 48 in a shape and applies constant braking elastic force to the inclined cam surface 48a of the brake cam 48 is loosely fitted onto the guide support shaft 50 so as to be able to slide forward and backward.
When the constant speed setting lever 39 is rotated in the speed increasing direction A in the forward state F, the engagement elongated hole 49 for receiving the guide support shaft, which is opened through the brake cam 48, is rotated integrally with the brake cam 48. Inclined cam surface 48a of the moving brake cam 48
When the brake element 52 relatively slides down and is rotated in the deceleration direction B in the forward movement F state, the brake element 52 also relatively slides down on the inclined cam surface 48a of the brake cam 48. By arranging the opening in the form of an arc that can be applied in a sliding manner, the braking elastic force applied to the constant speed setting lever 39 can be made stronger than that when the lever is rotated in the speed increasing direction A. Since the relationship is set so that the rotational operation in the deceleration direction B has an excessive effect, it goes without saying that by pressing the pedal P, it is possible to switch between forward and reverse driving and change the respective speeds. , by manually operating the constant speed setting lever 39 in advance and rotationally setting the constant speed setting cam plate 59 to the desired forward speed position, separately from the depressing operation of the pedal P. The positioning and constant speed state during forward F can be stably and reliably maintained, and there is no risk of erroneous operation or operator fatigue as with the conventional technology mentioned at the beginning, and various types of tractors can be controlled during forward F. It has the effect of allowing you to perform heavy-duty work safely and comfortably.

That is, in the case of the present invention, from the tractor body T,
Pedal shaft 26, rotational fulcrum shaft 64 of constant speed setting cam plate 59, and rotation lever 42 of constant speed setting lever 39
A total of three cams are installed in a substantially parallel horizontal state, and the pedal P and the constant speed setting cam plate 59 each have their own rotational movement about the separate pedal shaft 26 and fulcrum shaft 64. It is a prerequisite that it can be done.

The constant speed setting cam plate 59, which rotates around the fulcrum shaft 64, is pivotally connected to one end of the lever shaft 42 of the constant speed setting lever 39 via a connecting rod 60. Setting lever 39
It is designed to be rotated by the manual operation of the pedal P independently of the depression operation of the pedal P.

Therefore, as in the known device mentioned at the beginning, when positioning the constant speed state in the forward direction F,
There is no need to depress the pedal P, and the constant speed setting lever 39 can be prepositioned only by manual operation. Because of the manual operation method, the desired constant speed positioning can be performed accurately and easily.

In this regard, in the above-mentioned known device, the operating lever 19 of the holding mechanism 17 is swung to the operating position (ON) while the pedal 14 is depressed. In other words, the constant speed state in forward motion is still determined by the amount of depression of the pedal 14,
This is simply locked later by the holding mechanism 17. Therefore, it still causes fatigue during driving and it is not possible to accurately position the vehicle in a constant speed state. Furthermore, if the operating lever 19 is switched to the release position (OFF), the holding mechanism 17 will not work at all even during forward movement, and the above problem will continue to occur.

Furthermore, in the case of the above-mentioned known device, a pair of special stoppers 1 are provided separately from the holding mechanism 17 and the swinging arm 12 in order to regulate the depression limit of the pedal 14.
However, in the present invention, there is no need to install such special stoppers 16a, 16b.

That is, in the case of the present invention, the cam pin 33 is integrally projected from the pedal P which swings around the pedal shaft 26, while the cam pin 33 is integrally projected from the pedal P which swings around the pedal shaft 26, while the cam pin 33 is integrally projected from the pedal P which swings around the pedal shaft 26. Speed setting cam plate 5
9 is formed with a fitting notch 65 for the cam pin 33.

Regarding the fitted state between the cam pin 33 and the fitting notch 65, the constant speed setting cam plate 59 can only rotate from the neutral N position toward the forward F operating direction, and When the pedal P is rotated in the deceleration direction B in the state shown in FIG. The relationship is set so that the pedal P can be released from the cam plate 59 and rotate independently in both forward and reverse depression operation directions.

Therefore, as is clear from FIGS. 7, 8, and 15, the depression limit of the pedal P is the constant speed setting cam plate 59.
When the cam plate 59 is stopped and held at the neutral N position, the pedal P can be depressed in the forward and reverse directions, making it extremely safe. The cam plate 59 can also be used for regulating the depression of the pedal P.

In particular, in the present invention, when the constant speed setting cam plate 59 is rotated in the deceleration direction B in the forward state F as described above, the fitting notch 65 and the pedal P
The cam pin 33 of the cam plate 59 engages with the cam pin 33, and the pedal P rotates back together with the cam plate 59, automatically maintaining the set deceleration state. Constant speed setting lever 39
The manual operation in the direction of deceleration B allows for easy operation, and has the effect of easily and safely handling a wide range of agricultural operations in which soil and load conditions change from time to time.

In addition, the above-mentioned known device locks the constant speed state in forward motion after depressing the pedal and simply switches between the operating position (ON) and the release position (OFF), so the operating lever is The braking force acting on 19 is also always uniform. On the contrary,
In the present invention, the elastic force of braking applied to the constant speed setting lever 39 is greater when the lever is rotated in the deceleration direction B than when it is rotated in the speed increase direction A. The relationship is set to work.

That is, in the case of the present invention, the constant speed setting cam plate 59 is pivotally connected to one end of the lever shaft 42 passing through the tractor body T via a connecting rod 60; At the other end, in addition to a constant speed setting lever 39 that manually rotates the cam plate 59, a brake cam 48 having an inclined cam surface 48a is also fixed so that it can rotate integrally with the lever shaft 42. It is set up.

In a fixed state substantially parallel to the lever shaft 42, the slide guide support shaft 50 protruding from the tractor body T is fixed to the brake cam 4.
A brake element 52 extends through the slide guide support shaft 5 intersectingly with the brake cam 8 and applies constant braking force to the inclined cam surface 48a of the brake cam 48.
It is loosely fitted so that it can slide forward and backward to zero.

Furthermore, the brake cam 48 also has an engagement elongated hole 49 for receiving the slide guide support shaft 50 that is opened through the brake cam 48, and the engagement elongated hole 49 has an arc-shaped opening in particular. When the brake 52 is rotated in the speed direction A, the brake 52 relatively slides down the inclined cam surface 48a of the brake cam 48, which rotates together with the brake cam 48, whereas when the brake 52 is rotated in the deceleration direction B, , its brake 52
Similarly, the inclined cam surface 48a of the brake cam 48
It is formed so that it can be slid up relatively.

Therefore, as mentioned above, from the neutral N state, forward F
The constant speed setting cam plate 59 and the constant speed setting lever 39, which can only be rotated in the operating direction of However, the fitting notch 65 of the constant speed setting cam plate 59 and the cam pin 33 of the pedal P are subjected to an excessive braking force particularly in the deceleration direction B, and as described above, the fitting notch 65 of the constant speed setting cam plate 59 and the cam pin 33 of the pedal P are Since they are designed to lock each other during rotational operation, the constant speed state of forward movement F can be locked and held extremely stably and firmly. Such an effect cannot be expected from the configuration of the above-mentioned known device.

[Brief explanation of drawings]

Figures 1 and 2 are right and left side views schematically showing the tractor according to the present invention, Figure 3 is an enlarged side view of the assembled state of the pedal and constant speed setting cam plate, and Figures 4 and 5. The figure is a partially enlarged cross-sectional view taken along the - line and the V-V line in Figure 3, Figures 6 to 8 show forward/reverse switching and gear shifting, and Figure 6 is a side view of the neutral state. , Figures 7 and 8 are side views of the forward operation state and reverse operation state by depressing the pedal, and Figure 9
The figure is an enlarged side view of the installation state of the constant speed setting lever, Figures 10 and 11 are the same front view and partially cutaway front view, and Figures 12 to 15 show the constant speed holding function. Figures 12 and 13 are a side view and a front view showing the state of speed increasing operation using the constant speed setting lever in comparison with Figures 9 and 10, and Figure 14 shows the process of increasing and decelerating operation using the lever. Fig. 15 is a side view showing the constant speed action process of the cam plate in comparison with Fig. 7;
It is a line graph showing the return torque acting on the operating shaft of the HST. 11...HST operation axis, 12...HST control axis,
13...base plate, 14...operating arm,
19... Adjustment lever, 21... Neutral return coil spring, 26... Pedal shaft, 30... Swing plate, 33... Cam pin, 34, 60... Connection rod, 39... Constant speed setting lever, 42... Lever shaft, 48...brake cam, 49...engaging elongated hole, 50...slide guide support shaft, 52...brake element, 55...braking coil spring, 58...rotating arm, 59...constant speed Setting cam plate, 64... Fulcrum shaft, 65... Fitting notch, T... Tractor body,
P...pedal, W1, W2...cam pin arc movement range, X...acceleration allowable range.

Claims (1)

[Scope of Claims] 1. The operating arm 14 of the hydraulic continuously variable transmission and its rotation control pedal P are pivotally connected, and by depressing the pedal P, switching between forward and reverse and each of them is possible. In a tractor equipped with a fluid-type continuously variable transmission which is capable of changing speeds and whose operating arm 14 is always given elastic force to return to a neutral state, the tractor body T can be rotated around a horizontal axis. The lever shaft 42 is hung horizontally through the lever shaft 42, and in a fixed state substantially parallel to the lever shaft 42, the pedal shaft 26, which is the rocking fulcrum of the pedal P, and the rotation of the constant speed setting cam plate 59 are also connected from the tractor body T. A fulcrum shaft 64 serving as a center of motion is separately provided in a protruding manner, and
Cam pin 3 integrally protrudes from the pedal P
3 and a fitting notch 65 formed as an opening in the constant speed setting cam plate 59, the constant speed setting cam plate 59 can be rotated only when the constant speed setting cam plate 59 is directed from the neutral N position toward the forward F operation direction, and When the pedal P is rotated in the deceleration direction B in the forward movement F state, the pedals P are rotated back together with the constant speed setting cam plate 59 as they engage with each other.
Similarly, when the constant speed setting cam plate 59 is stopped and held at the neutral N position, the pedal P is released from the constant speed setting cam plate 59 and freely rotates independently in both forward and reverse depressing operation directions. At the same time, the constant speed setting cam plate 59 is pivotally connected to one end of the lever shaft 42 by a connecting rod 60, and a manually operated constant speed setting cam plate 59 is also connected to the other end of the lever shaft 42 by a connecting rod 60. A setting lever 39 and a brake cam 48 on which an inclined cam surface 48a is formed are integrally fixed, and the constant speed setting lever 39 controls the constant speed setting cam plate 5.
9 so that it can be rotated, and a lever shaft 42 is also connected from the tractor body T.
A slide guide support shaft 50 protruding in a fixed state substantially parallel to the brake cam 48 of the constant speed setting lever 39 is passed through the brake cam 48 of the constant speed setting lever 39 in an intersecting manner, and the inclined cam surface 48a of the brake cam 48 is provided with constant braking pressure. The brake 52 that applies force is loosely fitted onto the guide support shaft 50 so that it can slide forward and backward, and the engagement elongated hole 49 for receiving the guide support shaft is opened through the brake cam 48 as described above. When the constant speed setting lever 39 is rotated in the speed increasing direction A in the forward state F, the inclined cam surface 48a of the brake cam 48 rotates together with the constant speed setting lever 39.
When the brake element 52 relatively slides down and is rotated in the deceleration direction B in the forward movement F state, the brake element 52 also relatively slides down on the inclined cam surface 48a of the brake cam 48. By arranging the opening in the form of an arc that can be applied in a sliding manner, the braking elastic force applied to the constant speed setting lever 39 can be made stronger than that when the lever is rotated in the speed increasing direction A. A device for maintaining a constant speed state in a tractor equipped with a hydraulic continuously variable transmission, characterized in that the relationship is set so that the rotational operation in the deceleration direction B exerts an excessive force.