JPH10220567A - Belt type continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt type continuously variable transmission for quickly varying speed in the system where its speed-change drive mechanism slides its movable sheave, while preventing its belt and pulleys from causing frictional sounds. SOLUTION: A belt type continuously variable transmission employs a system, in which the actuation of switches S1 and S2 through the operation of a gearshift starts up a variable speed motor 35 at lower speed to thus slide a movable sheave 4b at lower speed such that it quietly starts to move a belt 9 running therein. After the lapse of a set period after the start-up of the motor 35, the transmission speeds up the motor 35 to quickly slide the sheave 4b such that it quickly moves the belt 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive mechanism for driving a speed change drive mechanism interlocking with a movable sheave of a split pulley, and sliding the movable sheave with the driving force of the speed change drive mechanism to reduce the belt winding diameter of the split pulley. The present invention relates to a belt-type continuously variable transmission provided with a shift operation mechanism that changes.

[0002]

2. Description of the Related Art The above-mentioned belt-type continuously variable transmission is designed so that a speed change operation can be performed by a light operation only for starting a speed change drive mechanism. In this type of belt-type continuously variable transmission, conventionally, the shift drive mechanism operates at a constant drive speed from the start until the shift operation is completed to slide the movable sheave.

[0003]

In the case of the above-mentioned conventional transmission technology, if the transmission drive mechanism is driven at a high speed so that the movable sheave can be slid quickly and the transmission can be shifted with good responsiveness, the transmission drive mechanism becomes The movable sheave is operated at a high speed from the start to rapidly start sliding. For this reason, when performing a speed change operation, a speed change sound in which the belt and the pulley are strongly rubbed is apt to be generated. An object of the present invention is to provide a belt-type continuously variable transmission capable of relatively quickly and quietly shifting.

[0004]

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

[Structure] A speed change mechanism for driving a speed change mechanism interlocked with a movable sheave of a split pulley, and sliding the movable sheave with the driving force of the speed change drive mechanism to change a belt winding diameter of the split pulley. In the belt-type continuously variable transmission, the transmission drive mechanism operates at a set elapsed time from the start, and operates at a speed lower than the set speed until the set elapsed time, and operates at the set speed after the set elapsed time has elapsed. Is provided with control means for automatically shifting the speed change drive mechanism.

[Operation] When changing the winding diameter of the belt by sliding the movable sheave, in the initial stage of movement, if the movable sheave slides quickly, the belt starts to move rapidly, and the friction noise between the belt and the pulley is generated. However, even after the movable sheave has moved to some extent, the friction noise between the belt and the pulley is less likely to be generated even if the movable sheave slides faster and the belt moves quickly compared to the initial stage of movement. In view of this, the time taken from the start of the sliding operation of the movable sheave until the friction noise is less likely to be generated is set as the set elapsed time. The drive speed of the speed change drive mechanism for producing the sliding speed of the movable sheave capable of rapidly moving the belt is set as the set speed. In other words, when a gearshift operation is performed, the gearshift drive mechanism slides the movable sheave while the gearshift is automatically controlled based on the set elapsed time and the set speed by the control means. The belt is gently moved so that the belt does not easily move, and after the friction noise is hardly generated, the belt is quickly moved so that the belt winding diameter changes quickly.

[Effect] When the variable speed drive mechanism slides the movable sheave while the speed is automatically controlled as described above, a friction noise is generated as compared with the case where the variable speed drive mechanism is driven at the set speed from the start. It is difficult for the gearshift drive mechanism to be able to shift gears with difficulty and quietly, and even after the set elapsed time has elapsed, the output speed changes more quickly than when driven at a speed lower than the set speed so that the gearshift can be performed with good responsiveness. Good shifting performance.

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

[0010] In the configuration according to the first aspect of the present invention, the set drive time is equal to the set elapsed time from the start.
The control means controls the speed change drive mechanism to perform a speed change control in a state in which the speed is continuously increased to the set speed until the time elapses.

[Operation] The speed change drive mechanism starts at a constant speed lower than the set speed, and slides the movable sheave while maintaining the start speed until the set elapsed time has elapsed. When the set elapsed time has elapsed, the speed change drive mechanism may be configured to perform speed change control so as to increase the speed to the set speed and slide the movable sheave. The movable sheave is slid while increasing the speed stepwise until the elapsed time elapses, and when the set elapsed time has elapsed from the start, the movable sheave is increased in speed to the set speed and the movable sheave is slid. Even so, the belt can start moving quietly and then quickly. But in this case,
The sliding speed of the movable sheave changes stepwise in the initial stage of the gear shift, and it becomes difficult for the belt to move smoothly. On the other hand, since the speed change drive mechanism is controlled so as to steplessly increase the speed from the start to the set speed, the sliding speed of the movable sheave increases smoothly at the beginning of the speed change, and the belt is quietly and smoothly. It starts moving and moves while effectively suppressing the generation of frictional noise.

[Effect] It is possible to obtain an extremely high speed change state so that the frictional noise can be effectively suppressed at the initial stage of the belt movement and the gear can be shifted quietly.

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

[0013] [Structure] In the structure of the invention according to claim 1 or 2, the transmission case in which the split pulley is provided is provided with an openable / closable vent, and the vent is closed when the speed change drive mechanism is in an operating state. And a control means for automatically opening and closing the vent so that the vent is opened when the speed change drive mechanism is stopped.

[Operation] When the speed change drive mechanism is operated, the ventilation port is automatically closed by the control means, so that even if a friction noise is generated, the speed change is performed so that it does not easily leak out of the speed change case through the ventilation hole. When the drive mechanism is stopped, the vent is automatically opened by the control means, and even if heat is generated, power is transmitted through the vent so that heat is easily radiated.

[Effect] In addition to the fact that the friction noise is not easily generated, it is difficult for the generated sound to come out of the transmission case. It is possible to obtain a highly reliable state so that it is easy to cause troubles such as seizure.

[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 sheave 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 engaged with the input shaft 3 by a key 5 so as to be integrally rotatable. The split pulley 4 that rotates integrally with the input shaft 3 is configured by the configured sheave 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 split pulley 7 that rotates integrally with the output shaft 6 is constituted by a sheave 7a integrally molded on one side and a sheave 7b slidably mounted on the other end side in the axial direction of the output shaft 6.

The transmission belt 9 is wound around the split pulley 4 on the input side and the split pulley 7 on the output side, and the transmission belt 9 is formed by a tension spring 10 composed of a coil spring attached to the boss portion of the sheave 7b of the output side split pulley 7. The transmission belt 9 and the split pulleys 4 and 7 are provided with a transmission tension to give a frictional force between the transmission belt 9 and the split pulleys 4 and 7 to rotate integrally. That is, one end of the tension spring 10 abuts against the outer side surface of the sheave 7 b of the split pulley 7, and the other end thereof is connected to the output shaft 6.
Is in contact with the spring receiving body 11 which is fitted to the outside. The spring receiving body 11 is supported by the output shaft 6 so as to be able to rotate only integrally by spline engagement with the output shaft 6. The sheave 7b is fitted to the output shaft 6 so as to be relatively rotatable, and a cam mechanism 12 is provided between the sheave 7b and the spring receiving body 11.
Is provided. The cam mechanism 12 is configured such that the boss portion of the sheave 7b is integrally rotatably engaged with the spring receiving body 11 so that the sheave 7b rotates integrally with the output shaft 6.
Further, the sheave 7b is slid toward the sheave 7a in proportion to an increase in the driving load applied to the output shaft 6. Therefore, the tension spring 10 uses the spring receiver 11 as a reaction force member, and a pair of sheaves 7 of the split pulley 7.
a, the movable sheave 7b slidably supported on the output shaft 6 among the movable sheaves 7b is slidably biased toward the fixed sheave 7a supported only slidably on the output shaft 6 for integral rotation; By urging the belt winding diameter of the split pulley 7 toward the enlarged side, a tension is applied to the transmission belt 9.

As shown in FIGS. 2 and 3, the boss portion of the movable sheave 4b slidably supported on the input shaft 3 of the pair of sheaves 4a and 4b of the input split pulley 4 has a bearing. And a roller 32 rotatably mounted via a support shaft 32a on a plurality of outer peripheral surfaces of the pulley operating body 31 in a circumferential direction of the pulley operating body 31, which is rotatably supported via An operation cylinder 33 having a cam portion 33a acting on the roller 32 as shown in FIG. 5 at one end side and being rotatably attached to the cylindrical portion 2a of the transmission case 2 around the axis X of the input shaft 3 is provided. A fan-shaped operation gear 34, which is integrally rotatably mounted on the outer peripheral surface of the cylindrical body 33 located outside the transmission case 2, an electric transmission motor 35 in which an output gear 35a meshes with the operation gear 34, and a transmission motor 35. Link A pair of switches S1 and S2 attached to the operation gear 34, and an attachment cylinder portion 37a including an operation arm 36 for the switches S1 and S2, are attached to the outer peripheral surface side of the operation cylinder 33 so as to be relatively rotatable. The shift operation mechanism 3 is operated by each of the shift levers 37.
0 is configured.

The speed change motor 35 is mounted on a bracket 38 supported by the speed change case 2. The pulley operating body 31 is connected to the input shaft 3 by a bearing positioned between the pulley operating body 31 and the boss portion of the sheave 4b, and a bearing stopper ring for locking the bearing to the sheave 4b and the pulley operating body 31. Sheave 4b in the direction of the axis X
Move with.

A cooling vent 13 is provided on the front and rear sides of the output end of the transmission case 2. As shown in FIG. 6, the vent 13 is provided with a shutter device 20. The shutter device 20 includes a plurality of opening / closing plates 22 supported by a bracket 21 fixed to the transmission case 2. Each of the opening / closing plates 22 is supported so as to swing around the axis of the pivot pin 23 to open and close.
An electromagnetic shutter solenoid 26 is linked to one opening / closing operation rod 25 connected to the second operation pin 24. That is, by operating the shutter solenoid 26, the shutter device 20 can be opened and closed by the driving force of the solenoid 26 so that the vent 13 can be opened and closed.

As shown in FIG. 7, the switches S1, S
2 is the transmission motor 35 and the shutter solenoid 2
6 is associated with a control means 14 for operating the same. The control means 14 is constituted by a microcomputer, and sets in advance information from the switches S1 and S2, information from the timer means 15, the elapsed time setting means 16 and the driving speed setting means 17 provided in the control means 13. A predetermined signal is automatically output to the motor drive unit 35a and the solenoid drive unit 26a based on a given program, and the transmission motor 35 and the shutter solenoid 26 are automatically operated.

That is, as shown in FIG. 8A, when the switches S1 and S2 are turned off, the cutoff signal o is provided therebetween.
When ff is turned on, an on signal is output to the control means 13 during that time. When both of the switches S1 and S2 are turned off, the control means 14 sets the motor driving unit 35a
And outputs a signal to stop the transmission motor 35 to stop the transmission motor 35. When S1 of the switches S1 and S2 is switched from cut to on, the control means 14
Outputs a signal to drive the transmission motor 35 in the forward rotation direction to the motor drive unit 35a from the switching time point t1 to drive the transmission motor 35 in the forward rotation direction, and thereafter, the switch S1 is switched from ON to OFF. Is switched to the speed change motor 35 at the switching time point t3.
Is output, and the transmission motor 35 is stopped. When S2 of the switches S1 and S2 is switched from off to on, the control unit 14 outputs a signal to drive the speed change motor 35 in the reverse rotation direction from the time point t1 at which the change is made, and rotates the speed change motor 35 in the reverse direction. Then, when the switch S2 is switched from ON to OFF, the control means 13 outputs a signal to stop the transmission motor 35 at the switching time t3 and stops the transmission motor 35. . In addition, regardless of whether the shift motor 35 is driven in the forward rotation or the reverse rotation, when the switches S1 and S2 are switched from the off state to the on state, the control means 14 controls the time elapsed from the switching time t1. Is measured based on information from the timer means 15, and the measured elapsed time, the set elapsed time T preset by the elapsed time setting means 16, and the drive speed setting means 17
Based on the preset speed MV, a signal for shifting the speed change motor 35 is output to the motor drive unit 35a to control the speed change of the speed change motor 35 as shown in FIG. That is, the transmission motor 35 is steplessly increased to the set speed MV until the measured elapsed time reaches the set elapsed time T, and the measured elapsed time is the set elapsed time T. After that, the shift control is performed so that the drive speed of the shift motor 35 is maintained at the set speed MV. As the set elapsed time T, a time taken from the start of the sliding operation of the movable sheave 4b until the friction noise between the belt 9 and the pulleys 4 and 7 is hardly generated is set. As the set speed MV, a belt 9
After the friction noise between the pulleys and pulleys 4 and 7 is less likely to occur,
The drive speed of the speed change motor 35 is set to produce the sliding speed of the movable sheave 4b that can move the belt 9 quickly while suppressing the friction noise.

As shown in FIG. 8 (c), when both the switches S1 and S2 are turned off, the control means 13 outputs a signal for opening the solenoid 26 to the solenoid driving section 26a, and outputs the signal to the shutter solenoid 26. Is operated to the opening side to open and operate the shutter device 20. One of the switches S1, S2 of the switches S1 and S2
When the switch 2 is switched from the cut to the on, the control means 13 outputs a signal to close and operate the solenoid 26 from the switch time t1, and operates the shutter solenoid 26 to the closing side to close the shutter device 20. .
Thereafter, when the switches S1 and S2 are switched from ON to OFF, a signal to open and operate the solenoid 26 is output at the switching time point t3, and the shutter solenoid 2 is turned ON.
6 is operated to the open side, and the shutter device 20 is returned to the open state and operated.

Thus, when the speed change motor 35 is in the operating state of sliding the movable sheave 4b, the control means 14 closes the ventilation port 13 during that time, and the speed change motor 3
When the sliding operation of the movable sheave 4b is stopped, the vent 13 is opened during that time.

As shown in FIG. 3, the transmission case 2 supports an operation lever 42 which is linked by an operation cable 41 to an operation valve V of a hydraulically operated forward / reverse switching device (not shown) provided in the traveling mission M. The bracket 43 is swingably supported. This operation lever 42
A forward / reverse switching cam 44 having a cam groove 44a whose free end is slidably engaged with the operation gear 34 is rotatably mounted integrally with the operation gear 34, and the transmission motor 35 rotates the operation gear 34 The forward / reverse switching cam 44 is rotated together with the operation gear 34 to swing the operation lever 42, and the operation valve V is switched via the operation cable 41, whereby the forward / backward switching device is moved to the forward side and the reverse side. It is configured to perform a switching operation or a switching operation to a neutral state where 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 the 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 positioned in the forward movement range F and the shift lever 39 is swung in a direction away from the neutral position N, 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, and the control means 14 drives the speed change motor 35 in the forward rotation direction, and the speed change motor 35 turns the operation gear 34 in the rotation direction f to turn the operation cylinder 33. Operate this operating cylinder 33
5 presses the pulley operating body 31 via the roller 32 on the inclined cam surface 33b of the cam portion 33a shown in FIG. 5 to slide the movable sheave 4b toward the fixed sheave 4a, thereby winding the belt of the split pulley 4. Increase the diameter. At this time, as the movement stroke of the shift lever 37 from the neutral position N is increased, the operating speed of the shift motor 35 is increased, and the operating cylinder 33 moves the roller 32 to the top of the inclined cam surface 33b. To increase the sliding stroke of the movable sheave 4b,
The belt winding diameter of the split pulley 4 becomes large. Conversely, when the shift lever 37 is swung in a direction approaching the neutral position N, the switch operating arm 36 swings in the swing direction r shown in FIG. The switch S2 of the pair of switches S1 and S2 is pressed by the unit 36a. Then, the switch S2 is turned on and the control means 14 drives the speed change motor 35 in the reverse rotation direction, and the speed change motor 35
Is rotated in the rotation direction r to rotate the operation cylinder 33,
The operating cylinder 33 moves the roller 32 to the bottom side of the inclined cam surface 33b, and slides the movable sheave 4b away from the fixed sheave 4a by the tension of the transmission belt 9, thereby obtaining a belt winding diameter of the split pulley 4. To shrink. At this time, as the shift lever 37 is moved closer to the neutral position N, the operating speed of the shift motor 35 is increased, and the operating cylinder 33 moves the roller 32 closer to the bottom end side of the inclined cam surface 33b to fix the roller 32 to the movable sheave 4b. In order to increase the interval with the sheave 4a, the belt winding diameter of the split pulley 4 is reduced.

When the shift lever 37 is positioned in the reverse range R and the shift lever 37 is operated to swing 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 control means 14 drives the speed change motor 35 in the reverse rotation direction, and the operation gear 34 is rotated in the rotation direction r to rotate the operation cylinder 33. Operation cylinder 33
5 pushes the pulley operating body 31 via the roller 32 on the inclined cam surface 33c of the cam portion 33a shown in FIG. 5, slides the movable sheave 4b toward the fixed sheave 4a, and winds the split pulley 4 around the belt. Increase the diameter. At this time, as the movement stroke of the shift lever 37 from the neutral position N is increased, the operation speed of the shift motor 35 is increased, and the operating cylinder 33 moves the roller 32 to the top of the inclined cam surface 33c. To increase the sliding stroke of the movable sheave 4b,
The belt winding diameter of the split pulley 4 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 switches S1 and S2 of
Is pressed. Then, the switch S1 is turned on, the control means 14 drives the speed change motor 35 in the forward rotation direction, and the operation gear 34 is rotated in the rotation direction f to rotate the operation cylinder 33, This operation cylinder 33
Moves the roller 32 to the bottom side of the inclined cam surface 33c, slides the movable sheave 4b away from the fixed sheave 4a by the tension of the transmission belt 9, and reduces 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 speed of the shift motor 35 is increased, and the operating cylinder 33 moves the roller 32 closer to the bottom end side of the inclined cam surface 33c to fix it to the movable sheave 4b. In order to increase the interval with the sheave 4a, the belt winding diameter of the split pulley 4 is reduced.

When the shift lever 37 is operated in either the forward range F or the reverse range R, or when the shift lever 37 is operated in any direction away from or approaching the neutral position N, the speed is changed. When the lever 37 is stopped at a desired operation 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 control means 14 stops the transmission motor 35. Thereby, the operation cylinder 3
3, the sliding operation of the movable sheave 4b is stopped, and the belt winding diameter of the split pulley 4 is maintained at a size corresponding to the operation position of the shift lever 37. When the operating position of the movable sheave 4 b is determined on the input side split pulley 4 and the belt winding diameter is determined, the belt winding diameter of the output side split pulley 7 is set to the input side split pulley due to the tension of the transmission belt 9. 4 and the rotation speed of the output shaft 6 becomes a speed corresponding to the operation position of the shift lever 37.

That is, at the time of forward movement, the shift lever 37 is swung in a direction away from the neutral position N to turn on the switch S1, and at the time of reverse drive, the shift lever 37 is swung in the direction away from the neutral position N. The switch S2 is turned on to start the speed change motor 35 via the control means 14. Then, the movable sheave 4b of the input side split pulley 4 slides toward the fixed sheave 4a by the driving force of the speed change motor 35 to change the belt winding diameter of the input side split pulley 4 to the enlarged side, and the output side The movable sheave 7b of the split pulley 7 is fixed by the tension of the transmission belt 9 to the fixed sheave 7a.
To change the belt winding diameter of the output side split pulley 7 to the reduction side. As a result, the rotation speed of the output shaft 6 changes to a higher speed than before the speed change operation.

When moving forward, the shift lever 37 is moved to the neutral position N
By turning the switch S2 to the on position by swinging in the direction approaching the control position, and turning the switch S1 to the on position by swinging the shift lever 37 in the direction toward the neutral position N during reverse travel, The transmission motor 35 is started via the transmission. Then, the operating cylinder 33 is rotated by the driving force of the speed change motor 35, and the movable sheave 4b of the input side split pulley 4 slides away from the fixed sheave 4a by the tension of the belt 9, and the input side split pulley 4 The movable sheave 7b of the output side split pulley 7 slides toward the fixed sheave 7a by the tension of the belt 9 to increase the belt winding diameter of the output side split pulley 7 on the enlarged side. Change to As a result, the rotation speed of the output shaft 6 changes to a lower speed than before the speed change operation.

In either case of shifting to the speed increasing side or the speed decreasing side, the speed change motor 35 is controlled by the control means 14 for the automatic speed change control until the set elapsed time T elapses from the time of starting. When the set elapsed time T elapses, the speed reaches the set speed MV and operates while maintaining the set speed MV, and the movable sheave 4b starts sliding gently. At the same time, a sliding operation is performed so as to gradually increase the speed to the set speed MV. As a result, the belt 9 is initially pulled out of the pulleys 4 and 7.
Then, it moves while gradually increasing the speed gently so that a friction sound with the pulleys is hardly generated, and thereafter moves quickly while hardly generating a friction noise with the pulleys 4 and 7. At this time, the control means 14 has automatically closed the vent 13,
Even if frictional noise is generated between the belt 9 and the pulleys 4 and 7, the gears are not easily leaked from the ventilation port 13, so that the speed can be changed quietly and quickly. Then, the movable sheave 4 by the speed change motor 35
After the sliding operation of b is stopped and the shift is completed, the control means 14 automatically opens the air vent 13 to radiate heat from the air vent 13 easily. It is transmitted in a state that is difficult to do.

In the case of the shift operation mechanism 30, when the shift lever 37 is switched from one of the forward range F and the reverse range R to the other, the switches S1 and S2 are turned on and the shift motor 35 is driven. , Roller 32 is inclined cam surface 33
During the movement of the portion 33e between the bottom end of b and the bottom end of the inclined cam surface 33c, the sliding operation of the movable sheave 4b is not performed, so that no shifting load is applied to the shifting motor 35. For this reason, the speed setting motor MV is set at the set speed MV from the start.
As shown in FIG. 9, when the speed change motor 35 is started when the roller 32 is located at the inter-cam surface portion 33e, the speed change motor is driven while the roller 32 moves on the cam surface portion 33e. The drive speed of the roller 35 increases to the higher speed NV than the set speed MV, and the roller 32
3e, the speed change motor 35 is set at the set speed MV in the initial stage after climbing the inclined cam surfaces 33b and 33c.
The movable sheave 4b is suddenly started at a higher speed than at a higher speed, so that a frictional noise is likely to be generated at an early stage of the shift.
However, the speed change motor 35 is driven at a speed lower than the set speed MV in the initial stage of the speed change by the speed change control by the control means 14, so that the roller 32 is
3e, even if the rotation speed of the speed change motor 35 is increased due to the no-load drive, the increased rotation speed becomes lower than the high speed NV, and the roller 32
The sliding operation of the movable sheave 4b is started relatively quietly even when the vehicle gets on the inclined cam surfaces 33b, 33c, and the shift can be performed while suppressing the generation of friction noise at the beginning of the shift.

[Another Embodiment] The present invention is also applicable to a case in which a hydraulic cylinder or the like is used in place of the speed change motor 35 so as to slide the movable sheave 4b. Therefore, the transmission motor 35 and the hydraulic cylinder are collectively referred to as a transmission drive mechanism.

[Brief description of the drawings]

FIG. 1 is a schematic diagram 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 a speed change operation unit.

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

FIG. 5 is an explanatory view of a cam portion of the operation cylinder.

FIG. 6 is a cross-sectional view of a shutter device for a vent.

FIG. 7 is a block diagram of a control system.

FIG. 8 is an explanatory diagram of a shift motor shift control.

FIG. 9 is an explanatory diagram showing a speed change of a speed change motor when there is no speed change control;

[Explanation of symbols]

 2 Transmission case 4 Split pulley 4b Movable sheave 13 Vent 14 Control means 30 Transmission operation mechanism t1 At start T Set elapsed time MV Set speed

Claims (3)

[Claims] A shift operation mechanism for driving a shift drive mechanism interlocked with a movable sheave of a split pulley and sliding a movable sheave with a driving force of the shift drive mechanism to change a belt winding diameter of the split pulley. A belt-type continuously variable transmission, wherein the speed change drive mechanism operates at a lower speed than a set speed until a set elapsed time from the start, and operates at the set speed after the set elapsed time has elapsed. A belt-type continuously variable transmission provided with control means for automatically shifting the transmission drive mechanism. 2. The control means controls the speed change drive mechanism to shift in a state in which the speed change drive mechanism continuously increases the speed to the set speed until the set elapsed time elapses from the start. The belt-type continuously variable transmission according to claim 1, wherein the transmission is configured as follows. 3. A transmission case in which the split pulley is housed is provided with an openable / closable vent, so that the vent is closed when the speed change drive mechanism is in an operating state, and the speed change drive mechanism is stopped. The belt-type continuously variable transmission according to claim 1 or 2, further comprising control means for automatically opening and closing the vent so that the vent opens when the belt is opened.