JPH10213214A - Belt type continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the continuously variable transmission to shift in conditions where it is hard to generate frictional sound between a transmission belt and a pulley. SOLUTION: A spring receiving body 11 and a spring pushing body 21 are provided on one end side of a tension spring 10 for giving tensile force to a transmission belt 9. When a pulley part 4b of an input side split pulley 4 is slidably operated to shift, the spring pushing body 21 is automatically rotated- operated by a rotating-operating shaft 24 to slidably operate the spring receiving body 11 in the direction away from a split pulley 7 to reduce the energizing force of the tension spring 10, and thus to reduce the tensile force of the transmission belt 9 below a tensile force for transmission. When the shifting is completed, the spring pushing body 21 is automatically return-rotated and operated to slidably operate the spring receiving body 11 toward the split pulley 7 to increase the energizing force of the tension spring 10, and thus to return the tensile force of the transmission belt 9 to the tensile force for transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt-type continuously variable transmission provided with a speed change mechanism for changing an output rotation speed by sliding a pulley portion of a split pulley to change a belt winding diameter of the split pulley. Related to the device.

[0002]

2. Description of the Related Art In the above-mentioned belt type continuously variable transmission, conventionally, as shown in, for example, JP-A-8-156621, one pulley portion of an output side split pulley slides toward the other pulley portion. There has been a configuration in which a tension applying mechanism including a biasing coil spring is provided to apply a transmission tension to the transmission belt, thereby applying a frictional force necessary for transmission between the transmission belt and the belt pulley.

[0003]

Conventionally, when the belt winding diameter of the split pulley is changed due to a speed change operation, the transmission belt is provided along the belt winding side surface of the belt pulley while maintaining the transmission tension. Had to move. For this reason, at the time of gear shifting, a gear shift noise in which the transmission belt and the belt pulley are strongly rubbed is apt to be generated. The purpose of the present invention is
An object of the present invention is to provide a belt-type continuously variable transmission that can transmit power efficiently by applying a necessary transmission tension to a transmission belt, and that can change speed quietly.

[0004]

The constitution, operation and effect of the invention according to claim 1 are as follows.

[Constitution] In a belt-type continuously variable transmission having a shift operation mechanism for changing an output rotation speed by slidingly operating a pulley portion of a split pulley to change a belt winding diameter of the split pulley, a transmission belt is provided. A tension applying mechanism for applying a tension to a transmission state in which the tension is set to a transmission tension, and a transmission state in which the tension is set lower than the transmission tension. A switching operation mechanism for switching the mechanism between a transmission state and a transmission state is provided in a state in which the switching operation mechanism is linked to the transmission operation mechanism, and when the transmission operation mechanism is in the operating state, the switching operation mechanism switches the tension applying mechanism to the transmission state. Automatic switching operation, and when the shift operation mechanism is in the stop state, the switching operation mechanism automatically switches the tension applying mechanism to the transmission state. And Aru.

[Operation] When the speed change operation mechanism is operated for the speed change operation, the tension imparting mechanism is brought into a gear shift state for automatic switching by the switching operation mechanism, and the tension of the transmission belt is made lower than the tension for transmission. Let it. As a result, even if the transmission belt moves while rubbing against the belt pulley, the belt winding diameter changes in a state in which the transmission belt is not rubbed as strongly as in the related art, which has been moving with the transmission tension, and is less likely to generate friction noise. When the shift operation mechanism is stopped after the shift is completed, the tension applying mechanism is brought into a transmission state for automatic switching by the switching operation mechanism, and the tension of the transmission belt is returned to the transmission tension. Thus, power is transmitted between the transmission belt and the pulley in a state where frictional force required for transmission is generated and slip is unlikely to occur.

[Effect] The power transmission belt can be efficiently transmitted so that the transmission belt is in the transmission tension state and the belt and the pulley are hardly slipped except during the speed change, so that the driving target such as a traveling device can be efficiently driven. In spite of this, the gear has a good shifting property so that the speed can be changed quietly without rubbing the belt and the pulley as strongly as in the past.

The structure, operation and effect of the invention according to claim 2 are as follows.

In the structure according to the first aspect of the present invention, the tension imparting mechanism is attached to the output side split pulley so as to urge the pulley portion of the output side split pulley, and the speed change operation mechanism increases the speed. The switching operation mechanism automatically switches the tension imparting mechanism to the speed change state when in the side operation state, and the switching operation mechanism when the speed change operation mechanism is in the deceleration side operation state. Are configured to maintain the tension applying mechanism in the transmission state.

[Operation] When the belt moves inward in the radial direction of the output side split pulley, the speed changes to the speed increasing side, and when the belt moves outward, the speed changes to the decelerating side. That is, when shifting to the speed increasing side, the belt slides the pulley portion in the direction opposite to the sliding operation direction by the tension applying mechanism, and when the tension applying mechanism is in the transmission state, the belt and the belt are moved. The pulley is strongly rubbed, and a shifting sound is easily generated. Also, when shifting to the deceleration side, the pulley portion is slid in the same direction as the sliding operation direction by the tension applying mechanism. Even if the tension applying mechanism remains in the transmission state, the belt and the pulley increase. It does not rub as strongly as at high speeds, and is less likely to generate shifting noise. In this way, the tension imparting mechanism is switched to the gear shifting state during the speed change on the speed increasing side, and the tension imparting mechanism is kept operated in the transmission state during the gear shifting on the deceleration side. In contrast, the speed can be changed while reducing the frequency of switching operation of the switching operation mechanism and the tension imparting mechanism, and making it difficult to generate frictional noise in which the belt and the pulley rub strongly.

[Effect] In a state excellent in speed change so that the speed can be relatively quietly shifted to both the speed increasing side and the speed reducing side, and the switching operation mechanism and the tension applying mechanism are switched during the speed reduction side. It is possible to obtain a highly durable state so that it can be used for a long time.

The structure, operation and effect of the invention according to claim 3 are as follows.

[0013] In the configuration according to the first or second aspect of the present invention, the shift operation mechanism slides a pulley portion of a split pulley by a driving force of a speed change motor which is started by a switch operation of a speed change lever. And the switching operation mechanism is configured to perform a switching operation based on information from the switch.

[Operation] When the switch is operated by the speed change lever, the speed change motor operates the split pulley to change the speed, and the switching operation mechanism switches the tension applying mechanism based on information from the switch.

[Effect] The gear shifting operation can be easily performed with a light operating force just by switching a switch. In addition, a switch for that purpose is also used for detecting a shift operation of the switching operation mechanism, and a gear that can be shifted gently can be advantageously obtained in terms of structure.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a rotational output of an engine E is transmitted to an input belt pulley 1 of a belt-type continuously variable transmission H via a belt tension clutch C. The rotation output is transmitted to the pair of left and right crawler traveling devices A via the traveling mission M, and the rotational power of the output shaft M1 of the traveling mission M is transmitted to the reaper K to transmit the power of the combine. The structure is configured.

The belt-type continuously variable transmission H is configured as shown in FIGS. That is, as clearly shown in FIG. 2, an input shaft 3 to which the input belt pulley 1 is integrally rotatably connected to one end thereof is rotatably supported at one end of the transmission case 2. And a pulley portion 4a integrally molded on one end of the inner portion of the transmission case, and slidably mounted on the other end in the axial direction of the input shaft 3 and rotated integrally with the input shaft 3 by a key 5. The split pulley 4 that rotates integrally with the input shaft 3 is constituted by the pulley portion 4b. The other end of the transmission case 2 rotatably supports an output shaft 6 having a spline shaft end 6a for outputting to the traveling mission M located at one end, and one end of a portion of the output shaft 6 inside the transmission case. A pulley portion 7a integrally molded on one side and an output shaft 6 on the other end side.
And a pulley portion 7b that is slidably mounted in the axial direction of the shaft and that is configured to rotate integrally with the output shaft 6 by a key 8, thereby forming a split pulley 7 that rotates integrally with the output shaft 6.

A transmission belt 9 is wound around the split pulley 4 on the input side and the split pulley 7 on the output side, and is transmitted by a tension spring 10 composed of a coil spring attached to a boss of a pulley portion 7b of the split pulley 7 on the output side. The transmission tension is applied to the belt 9 so that a frictional force is generated between the transmission belt 9 and the split pulleys 4 and 7 so that both rotate integrally. That is, one end of the tension spring 10 abuts against the side surface of the outside of the pulley portion 7 b of the split pulley 7, and the other end of the tension spring 10 abuts on the spring receiving body 11 fitted on the output shaft 6. As shown in FIG. 2, a cam body 22 fixed to the inner surface side of the speed change case 2 via a thrust ring 12 externally fitted to the output shaft 6 and a spring pressing body 21 as shown in FIG.
Supported by Accordingly, the tension spring 10 uses the spring receiving body 11 as a reaction force member to move the movable side pulley portion 7b slidably supported by the output shaft 6 of the pair of pulley portions 7a and 7b of the split pulley 7. The tension is applied to the transmission belt 9 by slidably biasing the pulley portion 7a on the fixed side, which is supported only on the output shaft 6 so as to be freely rotatable, and biasing the belt winding diameter of the split pulley 7 toward the enlarged side. give.

As shown in FIGS. 2 and 3, the movable pulley portion 4b of the pair of pulley portions 4a and 4b of the input side split pulley 4 which is slidably supported on the input shaft 3.
A cylindrical pulley operating body 31 whose boss portion is rotatably supported via a bearing, and is rotatably attached to a plurality of outer peripheral surfaces of the pulley operating body 31 in the circumferential direction via a support shaft 32a. 5 is provided with a cam portion 33a acting on the roller 32 as shown in FIG. 5 on one end side, and is attached to the cylindrical portion 2a of the transmission case 2 so as to be rotatable around the axis X of the input shaft 3. Body 33, this operation cylinder body 33
Fan-shaped operation gear 34 rotatably mounted on the outer peripheral surface side of the transmission case 2
The operation gear 3 is configured to operate the speed change motor 35 by linking with an electric speed change motor 35 in which an output gear 35a is meshed with a drive circuit (not shown) of the speed change motor 35.
4 is provided with a pair of switches S1 and S2 attached to the switch 4, an operation arm 36 for the switches S1 and S2, and a gear shift rotatably attached to the outer peripheral surface side of the operation cylinder 33 by an attachment cylinder 37a. The shift operation mechanism 30 is constituted by each of the levers 37. The speed change motor 35 includes a bracket 3 supported by the speed change case 2.
8 attached. The pulley operating body 31 is fixed to the input shaft 3 by a bearing located between the pulley operating body 31 and the pulley portion 4b, and a bearing stop ring for locking the bearing to the pulley operating body 31 and the pulley portion 4b. It moves together with the pulley portion 4b in the axial direction.

As shown in FIG. 3, an operation lever 42 interlocked by an operation cable 41 with an operation valve V of a hydraulically operated forward / reverse switching device (not shown) of the traveling mission M is provided. The supporting bracket 43 is swingably supported. This operation lever 4
A forward / reverse switching cam 44 having a cam groove 44a slidably engaged with the free end of the second gear 2 is rotatably attached to the operation gear 34 so that the speed change motor 35 can rotate the operation gear 34. Accordingly, the forward / reverse switching cam 44 rotates together with the operation gear 34 to swing the operation lever 42, and switches the operation valve V via the operation cable 41, thereby switching the forward / backward switching device to the forward side and the reverse side. , Or to switch to a neutral state in which transmission is stopped. Thereby, the switching operation of the forward / reverse switching device by the shift lever 37 is enabled.

That is, the speed change lever 37 is supported by the mounting cylinder portion 37a so as to be swingable about the axis Y, and the swing direction about this axis Y and the axis X of the input shaft 3 are provided. And the rocking operation is performed along a lever guide groove G shaped as shown in FIG. Then, when the shift lever 37 is operated to the neutral position N shown in FIG. 4, the forward / reverse switching device enters a neutral state, and the driving of the left and right crawler traveling devices A, A can be stopped. When the shift lever 37 is operated in the forward range F, the forward / reverse switching device is switched to the forward side, and the left and right crawler traveling devices A, A can be driven in the forward direction. And the left and right crawler traveling devices A, A can be driven to the reverse side.

When the shift lever 37 is moved in the direction away from the neutral position N when the shift lever 37 is located in the forward movement range F, the switch operating arm 36 is moved in the swing direction shown in FIG. f and the operating gear 3
The switch S1 of the pair of switches S1 and S2 is pressed by the operation pin portion 36a inserted into the through hole of No. 4. Then, the switch S1 is turned on to drive the transmission motor 35 in the forward rotation direction, and the transmission motor 35 rotates the operation gear 34 in the rotation direction f to rotate the operation cylinder 33. The operating cylinder 33 is a cam 33a.
5, the pulley operating body 31 is pressed via the roller 32 with the inclined cam surface 33b to slide the pulley portion 4b toward the pulley portion 4a, thereby increasing the belt winding diameter of the split pulley 4. . At this time, the larger the movement stroke of the shift lever 37 from the neutral position N, the larger the operation cylinder 33
Moves the roller 32 to the top of the inclined cam surface 33b to increase the sliding stroke of the pulley portion 4b, so that the belt winding diameter of the split pulley 4 increases. Conversely, when the shift lever 37 is swung in a direction approaching the neutral position N, the switch operating arm 36 is operated due to the lever operating force.
Swings in the swing direction r shown in FIG.
The switch S2 of the pair of switches S1 and S2 is pressed by a. Then, the switch S2 is turned on to drive the speed change motor 35 in the reverse rotation direction, and the speed change motor 35 turns the operation gear 34 in the rotation direction r to turn the operation cylinder 33. The operation cylinder 33 moves the roller 32 to the bottom side of the inclined cam surface 33b by the tension of the transmission belt 9 to slide the pulley portion 4b away from the pulley portion 4a, thereby reducing the belt winding diameter of the split pulley 4. Shrink. At this time, the shift lever 37 is moved to the neutral position N
As the operating cylinder 33 approaches the bottom end of the inclined cam surface 33b as the operating cylinder 33 approaches the bottom end, and the distance between the pulley portion 4b and the pulley portion 4a increases, the belt winding diameter of the split pulley 4 decreases. Become.

When the shift lever 37 is positioned in the reverse range R and the shift lever 37 is swung in a direction away from the neutral position N, the switch operating arm 36 swings in the swing direction r due to the lever operating force. And the operation pin portion 36a
Switch S of the pair of switches S1 and S2
2 is pressed. Then, the switch S2 is turned on, the speed change motor 35 is driven in the reverse rotation direction, the operation gear 34 is rotated in the rotation direction r, and the operation cylinder 33 is rotated. The pulley operating member 31 is pressed by the inclined cam surface 33c of the cam portion 33a shown in FIG.
To increase the belt winding diameter of the split pulley 4. At this time, as the moving stroke of the shift lever 37 from the neutral position N is increased, the operating cylinder 33 moves the roller 32 to the top of the inclined cam surface 33c to increase the sliding stroke of the pulley portion 4b. Split pulley 4
Belt winding diameter becomes large. Conversely, when the shift lever 37 is swung in a direction approaching the neutral position N, the switch operating arm 36 is swung in the swing direction f due to the lever operating force, and the switch pin 36a is pivoted by the operating pin portion 36a. Switch S1 of the switches S1 and S2 is pressed. Then, the switch S1 is turned on, the transmission motor 35 is driven in the forward rotation direction, the operation gear 34 is rotated in the rotation direction f, and the operation cylinder 33 is rotated, and the operation cylinder 33 is rotated. Moves the roller 32 to the bottom side of the inclined cam surface 33c under the tension of the transmission belt 9 to slide the pulley portion 4b away from the pulley portion 4a, thereby reducing the belt winding diameter of the split pulley 4. At this time, as the shift lever 37 is moved closer to the neutral position N, the operating cylinder 33 moves the roller 32 closer to the bottom end side of the inclined cam surface 33c to increase the distance between the pulley portion 4b and the pulley portion 4a. The belt winding diameter of the pulley 4 is reduced.

When the shift lever 37 is operated in either the forward range F or the reverse range R, or in any direction away from or near the neutral position N, the speed is changed. When the lever 37 is stopped at a desired operating position and the switches S1 and S2 are separated from the operation pin portion 36a as the transmission motor 35 rotates the operation gear 34, the switches S1 and S2 return to the off state and the transmission motor 35
To stop. Thereby, the sliding operation of the pulley portion 4b by the operating cylinder 33 is stopped, and the belt winding diameter of the split pulley 4 is maintained at a size corresponding to the operating position of the shift lever 37. When the operation position of the pulley portion 4b of the input side split pulley 4 is determined and the belt winding diameter is determined, the belt winding diameter of the output side split pulley 7 is
And the rotation speed of the output shaft 6 becomes the speed corresponding to the operation position of the speed change lever 37.

As shown in FIGS. 2 and 6, the spring pressing body 21 is rotatably supported on the output shaft 6, and
An operating shaft 2 having a fork 23 engaged with an arm portion 21a extending from the spring pressing body 21 at one end side so as to be integrally rotatable.
4 is rotatably inserted through the transmission case 2 and the operation shaft 2
4. A switching operation mechanism 20 for switching the tension spring 10 between the transmission state and the speed change state by the spring pressing body 21 and the cam body 22 is constituted. That is, the operation shaft 24 is rotated by a pair of operation levers 25 which are rotatably provided integrally with the end of the operation shaft 24 located outside the transmission case. Then, the operation shaft 24 is moved to the fork 23
By pivoting the arm portion 21a about the axis of the output shaft 6, the spring pressing body 21 is rotated about the axis of the output shaft 6 so that the transmission position shown in FIG.
The shift position is switched to the shift position shown in FIG. Fig. 7 (a)
As shown in FIG. 5, when the spring pressing body 21 is operated to the transmission position, the projections 21b, which are present in one side of the spring pressing body 21 and are distributed in the circumferential direction, ride on the pushing projections 22a of the cam body 22. . Then, for this climb, the spring pressing body 21 is slid in a direction away from the transmission case 2, and the spring receiving body 11 is slid through the thrust ring 12 toward the split pulley 7. In addition, the elastic deformation of the tension spring 10 is increased. For this reason, the tension spring 1
0 increases the operating force for slidingly urging the pulley portion 7b toward the pulley portion 7a, and reduces the tension of the transmission belt 9 by the friction between the transmission belt 9 and the pulleys 4 and 7 for transmission. To a transmission tension where the frictional force is high. On the other hand, as shown in FIG. 7B, when the spring pressing body 21 is operated to the shift position, the projection 21b of the spring pressing body 21 is disengaged from the pushing projection 22a of the cam body 22 to the side thereof. Then, due to this displacement and the operating force due to the elastic restoring force of the tension spring 10, the spring pressing body 21 is slid toward the speed change case 2, and the spring receiving body 11 is moved by the elastic restoring force of the tension spring 10. By sliding the tension spring 10 away from the split pulley 7, the amount of elastic deformation of the tension spring 10 is reduced. For this reason, the tension spring 10 reduces the operation force for urging the pulley portion 7b to slide toward the pulley portion 7a, and makes the tension of the transmission belt 9 lower than the transmission tension.

As shown in FIG. 8, a rotating reel 52 connected to a pair of operating levers 25 of the operating shaft 24 via an operating cable 51, and a rotating support shaft 5 of the rotating reel 52.
2a, a gear 53 rotatably connected to and rotatably operating the rotary reel 52, an electric motor 54 in which an output gear 54a is meshed with the gear 53, and a link between the electric motor 54 and the pair of switches S1 and S2. A linking mechanism 50 for linking the switching operation mechanism 20 and the speed change operation mechanism 30 with each of the control devices 55 is configured.

The control device 55 has an operation position sensor 56 for detecting which operation position the shift lever 37 is in the forward range F or the reverse range R, and a rotational position of the rotary reel 52. A rotary position sensor 57, which is a rotary potentiometer linked to the rotary support shaft 52a, is linked to the rotary shaft 52a. As shown in FIG. 3, the operation position sensor 56 is constituted by a rotary potentiometer attached to the bracket 38. The extension end side of the operation lever 56a extending integrally rotatable from the rotation operation shaft of the potentiometer engages with the cam groove 34a of the operation gear 34, and when the operation gear 34 is rotated, this rotation is performed. The operation lever 56a is rocked by the power. This allows
The operation position sensor 56 detects whether the shift lever 37 is operated in the forward movement range F or the reverse movement range R based on the rotation position of the operation gear 34, and performs control by converting the detection result into an electric signal. Output to the device 55. Control device 5
5 detects whether the spring pressing body 21 is in the transmission position or the shift position based on the detection result by the rotation position sensor 57, and this detection result, the detection result by the operation position sensor 56, The pair of switches S1,
The spring pressing body 21 is automatically switched by automatically operating the electric motor 54 based on the information from S2. That is, the shift lever 3
7 is operated in the forward movement range F, and the switch S1 is turned on and the switch S2 is turned off, the operation arm 25 is turned off.
The electric motor 54 is operated to operate the spring pressing body 21 to the first operation position P1 shown in FIG. When the shift lever 37 is operated in the forward movement range F and the switch S1 is turned off and the switch S2 is turned on, the operation arm 25 is moved to the second operation position P shown in FIG.
Then, the electric motor 54 is operated so as to be operated to the position 2, and the spring pressing body 21 is operated to the transmission position. The shift lever 37 is operated in the reverse range R, the switch S1 is turned off, and the switch S
When 2 is entered, the electric motor 54 is operated to operate the operation arm 25 to the first operation position P1, and the spring pressing body 21 is switched to the shift position. When the shift lever 37 is operated in the forward movement range F and the switch S1 is turned on and the switch S2 is turned off, the electric motor 5 is operated to operate the operation arm 25 to the second operation position P2.
4 to operate the spring pressing body 21 to the transmission position. Even if the shift lever 37 is operated to any one of the neutral position N, the forward range F, and the reverse range R, when any of the switches S1 and S2 is turned off, the operation arm 25 is operated to the second operation position P2. By operating the electric motor 54, the spring pressing body 21 is operated to the transmission position.

Thus, the switching operation mechanism 20 is linked to the shift operation mechanism 30 by the linkage mechanism 50, and detects whether the shift operation mechanism 30 is in the operating state or the stopped state by the switches S1 and S2. When the speed change operation mechanism 30 is in the operating state, the speed change operation mechanism 30 operates on either the speed increasing side or the deceleration side based on the detection result by the switches S1 and S2 and the detection result by the operation position sensor 56. State is detected, and the speed change operation mechanism 30 is detected.
In conjunction with the switching between the operating state and the stopped state, the automatic switching operation is performed as follows. That is, when the speed change operating mechanism 30 switches to an operation state in which the pulley portion 4b slides toward the fixed pulley portion 4a, the switching operation mechanism 20 automatically switches the tension spring 10 to the speed change state. While the transmission operation mechanism 30 is in the operating state, the tension spring 10 is maintained in the transmission state. When the shift operating mechanism 30 switches to the stop state in which the pulley portion 4b is maintained at the operating position corresponding to the operating position of the shift lever 39, the switching operating mechanism 20 automatically switches the tension spring 10 to the transmission state. Then, the tension spring 10 is maintained in the transmission state while the speed change operation mechanism 30 is in the stop state. When the shift operation mechanism 30 is switched to an operation state in which the pulley portion 4b is slid in a direction away from the fixed side pulley portion 4a, the switching operation mechanism 20 becomes the tension spring 1
0 is not switched to the transmission state, and is maintained in the transmission state.

That is, when the vehicle is moving forward, the shift lever 37 is operated to swing away from the neutral position N to turn on the switch S1, and when the vehicle is moving backward, the shift lever 37 is operated to swing away from the neutral position N. The switch S2 is turned on. Then, the shift operation mechanism 30 switches the switches S1,
When S2 enters, the speed change motor 35 is started, and the driving force of the speed change motor 35 causes the pulley portion 4b of the input side split pulley 4 to slide toward the fixed side pulley portion 4a to shift the belt of the input side split pulley 4. The winding diameter is changed to the enlarged side, and the pulley portion 7b of the output side split pulley 7 is slid in a direction away from the fixed side pulley portion 7a by the tension of the transmission belt 9 to wind the belt of the output side split pulley 7. Change the diameter to the reduction side. At this time, the switching operation mechanism 20 automatically switches the tension spring 10 to the speed change state by the linkage with the speed change operation mechanism 30 by the linkage mechanism 50, and the transmission belt 9.
Is lower than the transmission tension. This allows
Transmission belt 9 that moves in the radial direction of split pulleys 4 and 7
Then, the friction noise between the split pulleys 4 and 7 is hardly generated.
When the operation gear 34 is rotated to a position corresponding to the operation position of the transmission lever 37 and both switches S1 and S2 are turned off, the transmission operation mechanism 30 stops the transmission motor 35 by turning off the switches S1 and S2 and inputs. Side pulley 4
Of the pulley portion 4b is stopped, and the belt winding diameter of the input side split pulley 4 and the output side split pulley 7 is set to a diameter corresponding to the operation position of the shift lever 37. As a result, the rotation speed of the output shaft 6 becomes higher than that before the shift operation and becomes the rotation speed corresponding to the operation position of the shift lever 37. That is,
The speed changes to the speed increasing side. At this time, the switching operation mechanism 20
Automatically changes the tension spring 10 to the transmission state by the linkage with the speed change operation mechanism 30 by the linkage mechanism 50, and the tension of the transmission belt 9 returns to the transmission tension and the transmission belt 9
A frictional force required for transmission is generated between the split pulleys 4 and 7, and the rotational force of the output split pulley 4 is reduced by the output split pulley 7.
It is transmitted efficiently.

When moving forward, the shift lever 37 is moved to the neutral position N
The switch S2 is turned on by swinging in the direction approaching the position. When the vehicle is moving backward, the shift lever 37 is swung in the direction approaching the neutral position N to turn on the switch S1. Then, the shift operation mechanism 30 starts the shift motor 35 by turning on the switches S1 and S2, and the shift motor 35
The pulling portion 4b of the input side split pulley 4 is slid to move away from the fixed side pulley portion 4a by the driving force to change the belt winding diameter of the input side split pulley 4 to the reduction side, and the output side split pulley. The pulley portion 7b of FIG. 7 is slid toward the fixed pulley portion 7a by the operation force of the tension spring 10 to change the belt winding diameter of the output side split pulley 7 to the enlarged side. At this time, the switching operation mechanism 20 maintains the tension spring 10 in the transmission state by the linkage with the speed change operation mechanism 30 by the linkage mechanism 50. When the operation gear 34 is rotated to the position corresponding to the operation position of the transmission lever 37 and both switches S1 and S2 are turned off, the transmission operation mechanism 30 stops the transmission motor 35 by turning off the switches S1 and S2 and performs input. The sliding of the pulley portion 4b of the side split pulley 4 is stopped, and the belt winding diameter of the input side split pulley 4 and the output side split pulley 7 is set to a diameter corresponding to the operation position of the speed change lever 37. As a result, the rotation speed of the output shaft 6 becomes lower than that before the shift operation and becomes the rotation speed corresponding to the operation position of the shift lever 37. That is, the speed changes to the deceleration side. The tension of the transmission belt 9 is maintained at a transmission tension by a tension spring 10, and the transmission belt 9 and the split pulleys 4, 7 are maintained.
, A frictional force required for transmission is generated, and the rotating power of the output side split pulley 4 is efficiently transmitted to the output side split pulley 7.

[Another Embodiment] Instead of the tension spring 10,
A means for slidably urging the pulley portion 7b by hydraulic pressure to apply tension to the transmission belt 9 or a tension having a tension pulley acting on the transmission belt 9 between the input side belt pulley and the output side belt pulley. The present invention may be embodied by adopting a means including an arm and a tension spring that urges the tension arm to swing. Therefore, the tension spring 10, the hydraulic means, and the tension pulley means are collectively referred to as a tension applying mechanism.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a transmission structure of a combine.

FIG. 2 is a sectional view of a belt-type continuously variable transmission.

FIG. 3 is a side view of the speed change operation mechanism.

FIG. 4 is an explanatory diagram of an operation position of a shift lever.

FIG. 5 is an explanatory diagram of an operation section of the operation cylinder.

FIG. 6 is a sectional view of a switching operation mechanism.

FIG. 7 is an explanatory view showing a switching operation of a tension spring by a switching operation mechanism.

FIG. 8 is an explanatory view of a link mechanism.

[Explanation of symbols]

 Reference Signs List 4 split pulley 4b pulley portion 7 output side split pulley 7b output side pulley portion 9 transmission belt 10 tension applying mechanism 20 switching operation mechanism 30 speed change operation mechanism 35 speed change motor 37 speed change lever S1, S2 switch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16H 59:68 63:06

Claims (3)

[Claims] 1. A belt-type continuously variable transmission provided with a speed change mechanism for changing an output rotation speed by slidingly operating a pulley portion of a split pulley to change a belt winding diameter of the split pulley, comprising: A tension imparting mechanism for imparting tension to the belt is provided so as to be freely switchable between a transmission state in which the tension is set to a transmission tension and a shift state in which the tension is reduced below the transmission tension; A switching operation mechanism for switching the application mechanism between the transmission state and the transmission state is provided in a state in which the transmission operation mechanism is linked to the transmission operation mechanism. State, and when the speed change operation mechanism is in the stop state, the switching operation mechanism automatically switches the tension applying mechanism to the transmission state. Belt-type continuously variable transmission. 2. A tensioning mechanism is attached to an output split pulley so as to urge the pulley portion of the output split pulley to slide and urge the pulley portion. A switching operation mechanism automatically switches the tension applying mechanism to a shift state, and the switching operation mechanism maintains the tension applying mechanism in a transmission state when the shift operation mechanism is in a deceleration-side operation state. The belt-type continuously variable transmission according to claim 1, wherein the belt-type continuously variable transmission is configured to be operated. 3. The speed change operation mechanism according to claim 1, wherein the speed change operation mechanism is configured to perform a speed change operation by sliding operation of a pulley portion of a split pulley with a driving force of a speed change motor that is started by a switch operation of a speed change lever. 3. The belt-type continuously variable transmission according to claim 1, wherein the mechanism is configured to perform a switching operation based on information from the switch.