JP2002349651A - Belt tension system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a belt for belt tension system. SOLUTION: A belt tension system 60 is a clutch system, which has a couple of pulleys 52, 54 for power transmission system 55 and a belt 53 laid across these pulleys. Pressing a tension roller 62 to the belt to stretch it by turning a roller-driving electric motor 64 clockwise to pull a flexible wire rod 73 enables to transmit a power. Returning the tension roller with a returning operation of a return spring 63 for loosening the belt, by reversing a roller-driving electric motor to loosen the flexible wire rod will not enable to transmit a power. A belt tension system is equipped with a speed-switch-over system 90. The speed-switching system is one for switching the pulling and returning speed of the wire rod, so that the returning speed of the wire rod by returning the operation of the return spring becomes larger than the pulling speed of the flexible wire rod by the roller-driving electric motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in a belt tension mechanism.

[0002]

2. Description of the Related Art A belt tension mechanism uses a tension roller to tension or loosen a belt stretched over a pair of pulleys, thereby "turning on / off" power transmission.
It is called a belt tension clutch mechanism. Here, it is abbreviated as a belt tension mechanism. Since such a belt tension mechanism has a relatively simple configuration, it is often employed in various power transmission systems. As the belt tension mechanism, for example, JP-A-11-315896, "Clutch operating device for work vehicle" (hereinafter, referred to as "prior art") and JP-A-2001-81748, "belt tension mechanism of snow removing machine" ( Hereinafter, it is referred to as "conventional technology")
It has been known.

In the above prior art, as shown in FIGS. 5 and 6 of the publication, a transmission belt 44 is mounted on a pair of belt pulleys 41 and 43 (the numbers are cited in the publication. The same applies hereinafter). The present invention relates to a belt tension mechanism that transmits power by pressing and tensioning the tension wheel body 46a against the power transmission belt 44 and not transmitting power by returning the tension wheel body 46a and loosening the power transmission belt 44.

According to the prior art, the clutch cable 50 is rotated forward, the swing link 53 is swung via the output gear 50a and the gear 54, and the operation cable 5 is rotated.
7 to pull the tension wheel 46a to the transmission belt 4
4 can be pressed. The clutch motor 5
By rotating the swing link 53 in the reverse direction by reversing 0, and loosening the operation cable 57, the tension ring body 46 a can be returned by the return action of the cutting spring 47.

On the other hand, the above prior art is disclosed in FIG.
As shown in the figure, the belt 37 is wrapped around the small-diameter pulley 36 and the large-diameter pulley 38, the tension roll 62 is pressed against the belt 37 to transmit power, and the tension roll 62 is returned to loosen the belt 37. Wire winding belt tension mechanism 6 that does not transmit power
0.

According to the above conventional technique, the electric motor 6
The tension roll 62 can be pressed against the belt 37 by rotating the drum 4 forward and rotating the drum 74 through the gear set 75 and pulling the wire 73. Further, by rotating the electric motor 64 in the reverse direction to rotate the drum 74 in the reverse direction and loosening the wire 73, the tension roll 62 can be returned by the return action of the return spring 63.

[0007]

The above prior arts are
The operation cable 57 is driven by the forward / reverse rotation of the clutch motor 50.
Is a method of pulling or loosening. The pulling speed and the loosening speed of the operation cable 57 depend on the rotation speed of the clutch motor 50. For this reason, the clutch on / off operation speed is lower than other clutch mechanisms such as an electromagnetic clutch. During the clutch on / off operation, the half clutch state lasts longer than the other clutches. The half-clutch state is a state in which the transmission belt 44 has slipped on the belt pulleys 41 and 43 and the tension wheel body 46a. The slip time affects the durability of the transmission belt 44. The same applies to the above conventional technology.

An object of the present invention is to provide a technique capable of further improving the durability of a belt in a belt tension mechanism.

[0009]

In order to achieve the above object, a first aspect of the present invention is to provide a power transmission system for transmitting the power of a driving source to a load, a pair of pulleys and a belt extending over the pair of pulleys. A belt tension mechanism that transmits power by pressing the belt and tensioning the belt, and that does not transmit power by returning the tension roller and loosening the belt, this belt tension mechanism rotates the roller drive motor forward. Then, the tension roller is pressed against the belt by pulling a flexible wire such as a wire or a rope, and the tension roller is returned by the return action of the return member by rotating the roller driving motor in reverse to loosen the flexible wire. In the belt tension mechanism, when the flexible wire is drawn by the roller driving motor, Than pulling speed, wire return speed when returning the flexible wire at back action of the return member, characterized in that with a speed switching mechanism for switching to be larger.

The wire returning speed when returning the flexible wire by the return action of the return member is higher than the wire drawing speed when pulling the flexible wire by the roller driving motor. When switching from clutch on to clutch off, the tension roller returns quickly. As a result, the slip time during which the belt slips on the pulley or the tension roller can be reduced. Since the slip time can be shortened in this way, the durability of the belt can be further increased.

According to a second aspect of the present invention, the belt tension mechanism is arranged such that a rotating body driven forward and backward by a roller driving motor is driven.
A pulling member for drawing the flexible wire is disposed so as to be relatively rotatable, and a speed switching mechanism is interposed between the rotating body and the pulling member. The pulling member is connected to release the speed switching mechanism when the rotating body rotates in the reverse direction.

The operation of switching the connection / disconnection of the pulling member to / from the rotating body rotated forward / reversely by the motor for driving the roller can be reliably and promptly performed by the speed switching mechanism. Further, the belt tension mechanism with the speed switching mechanism can be simplified.

According to a third aspect of the present invention, the speed switching mechanism includes a ratchet groove provided on the pulling member, a ratchet claw swingably mounted on the rotating body so as to be engaged with the ratchet groove when the rotating body rotates forward, and a ratchet claw. A first spring that rebounds in a direction to hang the ratchet groove, a release cam member that is swingably attached to the rotating body and pushes the ratchet claw out of the ratchet groove by hitting the stopper when the rotating body starts reverse rotation; The release cam member includes a second spring that resiliently moves in a direction in which the ratchet pawl comes out of the ratchet groove.

Normally, the pulling member is connected to the rotating body by locking the ratchet mechanism (the combination of the ratchet groove and the ratchet pawl). At the start of reverse rotation of the rotating body, the release cam member together with the rotating body starts reverse rotation and hits the stopper. The ratchet mechanism is unlocked by swinging the release cam member against the stopper. As a result, the pulling member comes off the rotating body. The detached pull member
It reverses rapidly due to the return action of the return member. At the same time, the tension roller quickly returns due to the return action of the return member. Since the tension roller returns quickly,
The belt slip time is short. The speed switching mechanism can have a simple configuration, and the connection / disconnection switching operation of the pulling member with respect to the rotating body can be performed reliably and promptly.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that "before", "after",
“Left” and “right” follow the direction seen from the worker. Also, the drawings should be viewed in the direction of reference numerals. Hereinafter, an example in which the belt tension mechanism is applied to a snow remover will be described.

FIG. 1 is a side view of a snow blower according to the present invention. A snow blower 10 as a working machine has an idler wheel 11,
A body frame 21 is connected to a rear portion of a crawler frame 16 having three lower rolling wheels 12, 13, and 14 rotatably at a lower part so as to be able to swing up and down.
1, the engine 22 is mounted on the vehicle body frame 21, and the driving wheels 2 are mounted on the rear of the vehicle body frame 21.
3 and the crawler belt 24 is wound around the drive wheel 23 and the idler wheel 11. The pivot shaft 25 connecting the body frame 21 to the crawler frame 16 is moved forward, the drive wheel 23 is moved backward, and Wheel 14 is pivot shaft 25
And the drive wheel 23, and the pivot shaft 2
This is a crawler type vehicle in which an upper rolling wheel 26 for supporting a crawler belt 24 at an upper intermediate position between the wheel 5 and the driving wheel 23 is attached to the crawler frame 16.

The snow removing section 30 includes, as basic elements, an auger 31, a blower 32, a snow removing section housing 33, a sled 34, and a shooter 35 driven by the engine 22.
2. By transmitting the power of the engine 22 in the order of the drive pulley 36, the belt 37, the driven pulley 38, the drive shaft 39, the gear case 41, and the auger shaft 42, the auger 31 is rotated to scrape snow on the road in the front and back directions of the drawing. As a result, it can be sent to the blower 32 and the snow can be projected through the shooter 35 by the centrifugal force of the blower 32.

In this manner, a pair of pulleys 36 and 38 and a belt 37 extending over these are interposed in the power transmission system 43 for transmitting the power of the engine 22 to the auger 31 and the blower 32 as loads.

On the other hand, the traveling system 50 includes a continuously variable transmission 51 driven by the engine 22, idler wheels 11, lower rolling wheels 12,
13, 14, a driving wheel 23 and a crawler belt 24 as basic elements, an engine 22, a driving pulley 52, a belt 53,
By transmitting the power of the engine 22 in the order of the driven pulley 54, the continuously variable transmission 51, and the drive wheels 23, the crawler belt 24 can be rotated to travel on the road.

In this manner, a pair of pulleys 52, 54 and a belt 53 extending between them are interposed in the traveling power transmission system 55 for transmitting the power of the engine 22 to the crawler belt 24 as a load. In the figure, 27 is an engine cover, 28 is a fan for cooling the engine, and 29 is a hydraulic cylinder for adjusting the auger height.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 and shows that a belt tension mechanism 60 is provided in the traveling power transmission system 55. The belt tension mechanism 60 acts on a belt 53 wound around a small-diameter drive pulley 52 and a large-diameter driven pulley 54.
Power is transmitted by pressing belt 2 and stretching belt 53,
By returning the tension roller 62 and loosening the belt 53, power can be prevented from being transmitted.

More specifically, the belt tension mechanism 60 includes a tension roller 62 attached to the clutch arm 61, a return spring 63 as a return member for returning the tension roller 62, and a motor 6 for driving the roller.
4 as a drive source, a tensioner mechanism 65 for pressing the tension roller 62 against the belt 37 against the returning action of the return spring 63, and a roller driving motor 64 based on information that the engine switch 66 or the clutch switch 67 is turned off. And a control unit 68 that controls the roller driving motor 64 so that the tension roller 62 is returned to return the tension roller 62 to loosen the belt 37.

The tensioner mechanism 65 includes, for example, a tension rod 71 connected to the clutch arm 61, a tension spring 72 connected to the other end of the tension rod 71,
It comprises a flexible wire 73 such as a wire or a rope connected to the other end of the tension spring 72, and a tension mechanism 74 for pulling the flexible wire 73.

The action of tensioning the belt 37 is as follows. The control unit 68 having received the information that the engine switch 66 and the clutch switch 67 have been turned on issues a forward rotation command to the motor rotation direction control unit 78, sets the positive / negative electrode in the motor rotation direction control unit 78, and drives the roller. Motor 64 is rotated forward. When the roller driving motor 64 rotates forward by receiving the power supply from the battery 75, the pulling member 85 rotates forward, and the flexible wire 73 and the tension rod 71 are pulled.
Turn the clutch arm 61 shown by the imaginary line clockwise,
The belt 37 is tensioned by the tension roller (solid line) 62. The forward rotation of the roller driving motor 64 continues until the pin 76 extending from the tension rod 71 is detected by the first switch 77.

The action of loosening the belt 37 is as follows. The control unit 6 having received information that the main switch (engine switch) 66 or the clutch switch 67 has been turned off
8 issues a reverse rotation command to the motor rotation direction control unit 78, and the motor rotation direction control unit 78 reverses the positive electrode / negative electrode to reverse the roller driving motor 64. Since the flexible wire 73 and the tension rod 71 are in the loose state, the pulling action of the return spring 63 is effective, and the clutch arm 61 and the tension roller 62 shown by solid lines return to the positions of the imaginary lines, and the belt 37 is in the loose state. To The return of the clutch arm 61 is determined by the second switch 79
The control unit 68 stops the operation (reverse rotation) of the roller driving motor 64 based on the detection signal.

According to such a belt tension mechanism 60, the tension driving roller 62 is pressed against the belt 53 by rotating the motor 64 for driving the roller forward and pulling the flexible wire 73, and the motor 64 for driving the roller is rotated in the reverse direction. The tension wire 62 can be returned by the return action of the return spring (return member) 63 by loosening the flexible wire 73.

FIG. 3 is a control flow chart of the belt tension mechanism according to the present invention, where STxx indicates step numbers. ST01: Check whether the main switch is on. If YES, proceed to the next step. If NO, proceed to ST05. ST02: Check whether the clutch switch is on. If YES, proceed to the next step. If NO, proceed to ST05. ST03: Check whether the first switch means (SW1) is on. ST04: When ST03 is NO, the roller driving motor is rotated forward. This normal rotation is continued until SW1 is turned on in ST03.

ST05: When the main switch is not on in ST01, or when the clutch switch is not on in ST02, that is, when it is off, it is checked whether the second switch means (SW2) is on. ST06: When NO in ST05, the roller driving motor is reversed. This reverse rotation is continued until SW2 is turned on in ST05. ST01, ST02, ST05, ST0
According to 6, when the main switch or the clutch switch is switched from on to off, the belt can be automatically returned to the loose state.

FIG. 4 is a side view of a pulling mechanism according to the present invention. The pulling mechanism 74 includes a base 81 having a flat bottom plate 81a, a roller driving motor 64 mounted on the bottom plate 81a of the base 81, and a roller. A drive gear 82 attached to the output shaft 64a of the drive motor 64; a support shaft 83 raised from the bottom plate 81a of the base 81; a driven gear 84 and a pull member 85 rotatably attached to the support shaft 83; It comprises a speed switching mechanism 90 for switching the connection state between the pulling member 85 and the pulling member 85, and a stopper 86 for regulating the rotation angle of the pulling member 85.

The roller driving motor 64 has a built-in worm gear reduction mechanism 64b, and can output a reduced output from the output shaft 64a. The drive gear 82 and the driven gear 84 are spur gears that mesh with each other. The base 81 is
The crawler frame 16 and the body frame 2 shown in FIG.
1. A fixing member to be attached to the snow removing section housing 33 or the like.

The pulling member 85 is a disk-shaped reel rotatable relative to a driven gear 84 as a rotating body, and includes a winding groove 85a for winding the flexible wire 73 and a flexible wire 73.
And a hook groove 85b for hooking the end of the hook. Further, the pulling member 85 includes a ratchet groove 85c formed on the outer peripheral surface,
Stopper groove 8 formed in a plane portion along the outer periphery in an arc shape
5d. Stoppers 86 are provided at both ends (one end 85e and the other end 85f) of the stopper groove 85d in the longitudinal direction of the groove.
, The rotation angle of the pulling member 85 can be regulated.

The speed switching mechanism 90 is interposed between the driven gear 84 and the pulling member 85 so that when the driven gear 84 rotates forward (rotates counterclockwise in the figure), the driven gear 84 is connected to the driven gear 84. The pulling member 85 is connected, and when the driven gear 84 rotates in reverse (rotates counterclockwise in the figure), the driven gear 84
This is a mechanism for releasing the connection of the pulling member 85 to.

More specifically, the speed switching mechanism 90 includes a ratchet groove 85c provided in the pulling member 85, a ratchet claw 92 swingably attached to the driven gear 84, and a release cam member 93 swingably attached to the driven gear 84. And a second spring 104 set to resilient the ratchet claw 92 and a releasable cam member 93.

The ratchet pawl 92 is a member that hooks the pawl portion 92a into the ratchet groove 85c when the driven gear 84 rotates forward. The release cam member 93 is a member that swings by hitting the fixed-side stopper 86 when the driven gear 84 starts reverse rotation, and pushes the ratchet claw 92 out of the ratchet groove 85c.

The first spring 102 has a ratchet pawl 9
2 is repelled in a direction to hang the ratchet groove 85c. Second
The spring 104 springs the release cam member 93 in a direction in which the ratchet claw 92 is disengaged from the ratchet groove 85c.

The second switch means 79 is attached to the edge 81b of the base 81 via the stay 111, and the displacement of the release cam member 93 is detected by the second switch means 79, so that the roller drive motor 64 is driven. The stop timing at the time of reverse rotation can be detected.

FIG. 5 is a sectional view taken along the line 5-5 in FIG. 4, in which the support shaft 83 is a bolt / nut mounted on the bottom plate 81a, and the driven gear 84 and the pulling member 85 are mounted via the bush 87. Is shown. The base 81 is formed by bending an edge 81b from the edge of the bottom plate 81a.
Attach 6a. The stopper 86 is a round bar member bent and formed in a substantially U-shape that is open to the bottom plate 81a side. A straight base end portion 86a extends toward the bottom plate 81a, and a straight distal end portion 86b is a stopper. Groove 85
d towards the bottom of d. In the figure, 89 is an annular cushion material made of rubber, and 112, 113 and 114 are washers.

FIG. 6 is an exploded view of a speed switching mechanism according to the present invention, in which a ratchet pawl 92 and a release cam member 93 are swingably mounted on a support shaft 91 which is raised from a driven gear 84 (see FIG. 4). Is shown. Ratchet claws 92
A member having an acute-angled claw portion 92a formed at one end of a swing and a pin 92b in the vicinity thereof, and a driven convex portion 92c formed at the other end of the swing. The claw portion 92a is a hook portion to be hooked on the ratchet groove 85c (see FIG. 4).

The release cam member 93 is a flat plate having a substantially elliptical shape in a plan view, which is superimposed on the ratchet claw 92 and rotatable relative to the ratchet claw 92. And the projection 93b for extrusion.
Is formed. The protrusion 93 b for pushing is formed so that the ratchet claw 9 is in contact with the contact surface 92 d of the protrusion 92 c for driving.
The driving member extends to the second side.

Meanwhile, the support shaft 91 has a long slit 91a formed at the tip end surface, and the first spring 102
In addition, a second spring 104 is attached. The first spring 102 and the second spring 104 are torsion coil springs arranged on the same coil center, and these torsion coil springs are integrally formed to be a single member. This single member is called "torsion coil spring 94".
It is.

To be more specific, “the torsion coil spring 9
4 ”is a first arm portion 101 on one end side, and a first spring 102 wound in a coil shape from the end of the first arm portion 101.
A straight portion 103 provided at the winding end of the first spring 102; a second spring 104 further wound in a coil shape from the end of the straight portion 103; and a second arm provided at the winding end of the second spring 104. The part 105 is a double torsion type coil spring formed of one wire.

The first arm portion 101 has a U-shaped hook 101a at the tip, and the second arm portion 105 has an L-shaped hook 105a at the tip. First and second springs 102,
The straight portion 103 between 104 extends in the coil radial direction through the coil center.

The first and second springs 102,
104, and the straight portion 103 is inserted into the slit 91a and hung.
The torsion coil spring 94 can be attached by hooking the U-shaped hook 101a on b and the L-shaped hook 105a on the hook hole 93c of the release cam member 93.
In this way, the first spring 102 and the second spring 104 can perform an independent torsion spring action.

The two first springs, which have independent spring action,
-Since the second springs 102 and 104 are formed as a single part, the number of parts can be reduced, and the second springs 102 and 104 can be easily arranged in a narrow space. Note that the first and second
The springs 102 and 104 may be made into two parts.

The first spring 102 and the second spring 104 perform a spring action so that they are resiliently resilient in a direction in which the pushing projection 93b comes into contact with the contact surface 92d of the driven projection 92c. That is, the first spring 102 is
2 springs clockwise in the figure, and the second spring 104 springs the release cam member 93 counterclockwise in the figure.

However, the first spring 102 and the second spring 104 have substantially the same coil diameter, number of turns, and pitch. The length of the first arm portion 101 is larger than the length of the second arm portion 105. Therefore, the torque of the first spring 102 to resilient the ratchet pawl 92 clockwise in the figure is greater than the torque of the second spring 104 to resiliently release the release cam member 93 in the counterclockwise direction. Reference numeral 95 denotes a retaining pin.

FIG. 7 is a side view of the speed switching mechanism according to the present invention, and shows a support shaft 9 parallel to the support shaft 83 (see FIG. 5).
1 is mounted on the driven gear 84, the ratchet pawl 92 and the release cam member 93 are superimposed on the driven gear 84 in this order, and the cam portion 93a of the release cam member 93 is moved outwardly of the driven gear 84 so that the release cam member 93 moves. When the cam portion 93a
Indicates that the stopper 86 is disposed so as to contact the base end portion 86a of the stopper 86 indicated by an imaginary line.

FIG. 8 is an exploded view of the pulling mechanism according to the present invention, and shows the relationship between each member of the pulling mechanism 74 and the speed switching mechanism 90 with respect to the base 81. 96 is a washer.

Next, the belt tension mechanism 6 having the above configuration
The operation of 0 will be described with reference to FIGS. FIG. 9 is an operation diagram (part 1) of the belt tension mechanism according to the present invention, and shows that the belt tension mechanism 60 is in an off state. In the off state, the tension roller 62 returns to loosen the belt 53, and the driving pulley 52
From the drive pulley 54 to the driven pulley 54. The roller driving motor 64 is stopped. One end 85e is stopper 8
The pulling member 85 is prevented from rotating clockwise in the figure by abutting the tip portion 86b of the sixth through the cushion material 89.

As described above, the torque at which the first spring 102 springs the ratchet pawl 92 clockwise in the figure is larger than the torque at which the second spring 104 springs the release cam member 93 counterclockwise in the figure. Therefore,
The claw portion 92a enters the ratchet groove 85c.

FIG. 10 is an operation diagram (part 2) of the belt tension mechanism according to the present invention, and shows a start point of the clutch-on operation. By rotating the roller driving motor 64 in the normal direction, the driven gear 84 moves in the direction of the arrow Lr (counterclockwise in the figure).
, Ie, forward rotation. For this reason, the claw portion 92a rotates forward with the driven gear 84 and engages with the ratchet groove 85c to rotate the pulling member 85 forward. That is, the ratchet mechanism formed by the combination of the ratchet groove 85c and the ratchet claw 92 is locked. As described above, when the driven gear 84 rotates forward, the pulling member 85 can be connected to the driven gear 84 by the speed switching mechanism 90.

When the pulling member 85 rotates forward, the pulling member 85 winds up and pulls the flexible wire 73, swings the clutch arm 61, and allows the tension roller 62 to approach the belt 53.

FIG. 11 is a diagram (part 3) of the operation of the belt tension mechanism according to the present invention, showing a state during the clutch-on operation. The driven gear 84, the ratchet pawl 92, and the release cam member 93 further rotate forward as the roller drive motor 64 continues to rotate forward. As a result, the cam portion 9 of the release cam member 93
3a hits the base end portion 86a of the stopper 86 and swings clockwise in the drawing. In this way, the release cam member 93 once escapes from the base end portion 86a, and after returning, returns to its original state by the elastic force of the second spring 104.

FIG. 12 is an operation diagram (part 4) of the belt tension mechanism according to the present invention.
Indicates that the motor stopped after further continuing normal rotation. By continuing the forward rotation of the roller driving motor 64 in this manner,
The pulling member 85 further pulls the flexible wire 73 and presses the tension roller 62 against the belt 53 to stretch the belt 53. As a result, the clutch-on operation is completed. Power can be transmitted from the driving pulley 52 to the driven pulley 54 via the belt 53.

As is apparent from the above description, the wire drawing speed when the flexible wire 73 is drawn by the roller driving motor 64 is a value corresponding to the rotation speed of the roller driving motor 64. To perform the clutch-off operation from the clutch-on state, the roller driving motor 64 is reversed.

FIG. 13 is an operation diagram (part 5) of the belt tension mechanism according to the present invention, and shows that the clutch off operation has started. The driven gear 84, the ratchet pawl 92, and the release cam member 93 rotate in the direction of the arrow Rr, that is, reversely rotate, by reversing the roller driving motor 64. As a result, the cam portion 93a of the release cam member 93 is
6 and swings counterclockwise in the figure against the base end portion 86a. In this manner, the release cam member 93 is connected to the base end 8.
Escape from 6a once. When the release cam member 93 swings in the counterclockwise direction in the drawing, the pushing protrusion 93b pushes the driven protrusion 92c in the counterclockwise direction in the drawing. When the ratchet claw 92 swings counterclockwise in the drawing, the claw portion 92a comes off the ratchet groove 85c. That is, the ratchet mechanism is unlocked. In this way, when the driven gear 84 rotates in the reverse direction, the speed switching mechanism 90 is released, and the connection state of the pulling member 85 to the driven gear 84 can be released.

At the moment when the claw portion 92a comes off from the ratchet groove 85c, the flexible wire 73 is quickly returned by the return action of the elastic force of the return spring 63. For this reason, the pulling member 85 reverses rapidly. Since the elastic force of the return spring 63 is used, the wire return speed when returning the flexible wire 73 by the return action of the return spring 63 is not affected by the rotation speed of the roller driving motor 64.

Therefore, the wire returning speed is much higher than the wire drawing speed when the flexible wire 73 is drawn by the roller driving motor 64. By returning the tension roller 62 and quickly loosening the belt 53, power can be prevented from being transmitted. Since the tension roller 62 returns quickly, the slip time of the belt 53 can be reduced. By shortening the slip time, the durability of the belt 53 can be further increased. The roller drive motor 64 continues to rotate in the reverse direction. As is clear from the above description, the speed switching mechanism 90 plays a role of a quick return mechanism (quick return mechanism).

FIG. 14 is an operation diagram (part 6) of the belt tension mechanism according to the present invention, showing a state during the clutch-off operation. The release cam member 93 once escapes from the base end portion 86a, and returns after being passed by the elastic force of the second spring 104. At that time, the pulling member 85 is set to the arrow R
Since it is returned in the r direction, the phase of the ratchet groove 85c is out of phase. The claw portion 92a comes off the ratchet groove 85c and slips on the outer peripheral surface 85g of the pulling member 85.

Thereafter, the driven gear 84, the ratchet pawl 92, and the release cam member 93 return to the positions shown in FIG. 9 as the roller driving motor 64 further rotates in the reverse direction. At this time, the return of the cam portion 93a is indicated by the second switch means 79 (FIG. 1).
4), and based on this detection signal, the roller driving motor 64 stops the reverse rotation operation.

FIG. 15 is a view showing a modification of the tension mechanism according to the present invention.
The arm 85h extends from the outer peripheral surface of the flexible wire 73, and the end of the flexible wire 73 is connected to the arm 85h. Since the arm 85h is provided, the winding groove 85a shown in FIG. 4 is unnecessary. Other configurations are the same as those shown in FIGS. 1 to 14 described above, and are denoted by the same reference numerals and description thereof will be omitted.

In the embodiment of the present invention, the belt tension mechanism 60 is connected to the traveling power transmission system 5 of the snow blower 10.
Although the example adopted in No. 5 was explained, it is not limited to this and can be adopted in various power transmission systems.
For example, the present invention can be applied to the power transmission system 43 of the snow removing unit 30. Further, the drive source of the power transmission system is not limited to the engine 14, and may be, for example, an electric motor. Furthermore, the rotating body driven forward and reverse by the roller driving motor 64 is not limited to the driven gear 84.

[0063]

According to the present invention, the following effects are exhibited by the above configuration. Claim 1 is that, in the belt tension mechanism, the wire returning speed when returning the flexible wire by the return action of the return member is higher than the wire pulling speed when pulling the flexible wire by the roller driving motor, The provision of the speed switching mechanism for switching so as to increase the speed makes it possible to quickly return the tension roller when switching from clutch on to clutch off. As a result, the slip time during which the belt slips on the pulley or the tension roller can be reduced. By shortening the slip time, the durability of the belt can be further increased.

According to a second aspect of the present invention, the belt tension mechanism is arranged such that a rotating body driven forward and reverse by a roller driving motor is driven.
A pulling member for drawing the flexible wire is disposed so as to be relatively rotatable, and a speed switching mechanism is interposed between the rotating body and the pulling member. Since the pulling member is connected and the speed switching mechanism is released when the rotating body rotates in the reverse direction, the switching operation of the pulling member with respect to the rotating body that is normally and reversely rotated by the roller driving motor is performed by the speed switching mechanism. It can be performed reliably and quickly. Further, the belt tension mechanism with the speed switching mechanism can be simplified.

A third aspect of the present invention provides a speed switching mechanism comprising a ratchet groove provided in a pulling member, a ratchet pawl swingably mounted on the rotating body so as to be engaged with the ratchet groove when the rotating body rotates normally, and a ratchet pawl. A first spring that rebounds in a direction to hang the ratchet groove, a release cam member that is swingably attached to the rotating body and pushes the ratchet claw out of the ratchet groove by hitting the stopper when the rotating body starts reverse rotation; Since the release cam member is constituted by the second spring resilient in a direction in which the ratchet pawl comes out of the ratchet groove, the speed switching mechanism can be simplified, and the connection / disconnection switching of the pulling member with respect to the rotating body can be performed. The operation can be performed reliably and promptly.

[Brief description of the drawings]

FIG. 1 is a side view of a snow blower according to the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a control flow chart of the belt tension mechanism according to the present invention.

FIG. 4 is a side view of a tension mechanism according to the present invention.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is an exploded view of a speed switching mechanism according to the present invention.

FIG. 7 is a side view of the speed switching mechanism according to the present invention.

FIG. 8 is an exploded view of a tension mechanism according to the present invention.

FIG. 9 is an operation diagram (part 1) of the belt tension mechanism according to the present invention.

FIG. 10 is an operation diagram (part 2) of the belt tension mechanism according to the present invention.

FIG. 11 is an operation diagram (part 3) of the belt tension mechanism according to the present invention.

FIG. 12 is an operation diagram (part 4) of the belt tension mechanism according to the present invention.

FIG. 13 is an operation diagram (part 5) of the belt tension mechanism according to the present invention.

FIG. 14 is an operation diagram (part 6) of the belt tension mechanism according to the present invention.

FIG. 15 is a modified example of the tension mechanism according to the present invention.

[Explanation of symbols]

Reference numeral 22: drive source (engine), 52, 54: pair of pulleys, 53: belt, 55: power transmission system, 60: belt tension mechanism, 62: tension roller, 63: return member (return spring), 64: roller drive Motor 73, flexible wire 84, rotating body (driven gear), 8
5: Pulling member, 85c: Ratchet groove, 86: Stopper, 90: Speed switching mechanism, 92: Ratchet pawl, 93
... Release cam member, 102 first spring, 104 second spring.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideyuki Sakamoto 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3J049 AA01 BB05 BB23 BC04 BD02 BD03 BH02 CA06

Claims (3)

[Claims] A power transmission system for transmitting the power of a drive source to a load is provided with a pair of pulleys and a belt wrapped around the pair of pulleys. The tension roller is pressed to stretch the belt to transmit power, and the tension roller is transmitted. A belt tensioning mechanism that does not transmit power by returning and loosening the belt, wherein the belt tensioning mechanism rotates the roller driving motor forward to draw a flexible wire such as a wire or a rope. A belt tension mechanism that presses a tension roller against the belt and reverses the roller driving motor to loosen the flexible wire, thereby returning the tension roller by a return action of a return member; The mechanism is higher than the wire drawing speed when the flexible wire is drawn by the roller driving motor.
A belt tension mechanism, comprising: a speed switching mechanism for switching the wire return speed when returning the flexible wire by the return action of the return member so as to increase. 2. The belt tension mechanism further comprises: a pulling member for pulling the flexible wire, which is rotatable relative to a rotating body driven forward / reversely by the roller driving motor;
By interposing the speed switching mechanism between the rotating body and the pulling member, the pulling member is connected to the rotating body by the speed switching mechanism during normal rotation of the rotating body, and the speed switching mechanism during reverse rotation of the rotating body. The belt tension mechanism according to claim 1, wherein the belt tension mechanism is configured to be released. 3. The speed switching mechanism includes a ratchet groove provided on the pulling member, a ratchet pawl swingably attached to the rotating body so as to be engaged with the ratchet groove when the rotating body rotates forward, and a ratchet claw. A first spring that rebounds in a direction to be hooked on the ratchet groove, a release cam member that is swingably attached to the rotating body and pushes the ratchet claw out of the ratchet groove by hitting the stopper when the rotating body starts reverse rotation; 3. The belt tension mechanism according to claim 2, wherein said release cam member comprises a second spring resiliently resilient in a direction in which said ratchet pawl comes out of said ratchet groove.