JP2001330099A - Continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuously variable transmission to improve Low return performance during rapid deceleration. SOLUTION: A change gear ratio varying mechanism is provided to run a belt 15 around and between a drive pulley 11 and a driven pulley 21 and very the belt winding diameters of the two pulleys in a mutually reverse direction and a tentioner device 50 is provided to generate a belt tension by pressing a belt. A motor 55 for tension regulation is provided to be capable of regulating a belt tension. When rapid deceleration of a vehicle is detected, the change gear ratio varying mechanism is changed in a speed to the low change gear ratio side and the tension regulating motor 55 is controlled to a value lower than a belt tension at which a slip occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a continuously variable transmission, and more particularly to a V-belt type continuously variable transmission for a vehicle.

[0002]

2. Description of the Related Art Various types of continuously variable transmissions have been proposed and some of them have been put to practical use. The continuously variable transmission includes a driving pulley, a driven pulley, and a belt wound between the two pulleys. By changing the belt winding diameter of the driving pulley and the driven pulley in the opposite direction, the gear ratio is changed. Is continuously variable. Therefore, there is an advantage that smooth running can be realized without any shift shock.

[0003] Japanese Patent Application Laid-Open No. Hei 5-280613 discloses a drive mechanism that changes the belt winding diameter of a driving pulley and a driven pulley, and a driving mechanism that changes the belt winding diameter of both pulleys in opposite directions. A speed changeover mechanism that changes the speed ratio by making the belt wrapped around both pulleys generate a belt thrust by pressing the slack side of the belt so that it becomes larger than the belt tension generated according to the speed ratio. There has been proposed a continuously variable transmission provided with a thrust generating mechanism for causing the same to be driven. The thrust generating mechanism includes an arm pivotally supported by a transmission case, a tension roller rotatably supported at the tip of the arm, and an arm in a direction in which the tension roller presses the back side of the belt on the loose side. And a spring that biases the rotation.

[0004]

As described above, in the case of a thrust generating mechanism having a structure in which the arm is rotated and biased by a spring to press the tension roller against the belt, the belt tension is maintained substantially constant by the biasing force of the spring. Therefore, there is a disadvantage that the Low (minimum speed ratio) return performance during sudden deceleration is poor. For example, if the brake is operated and the vehicle is suddenly decelerated while traveling at a high speed ratio, the continuously variable transmission moves the movable sheave of the driven pulley in the opening direction to move to the low speed ratio, and moves the movable sheave of the driven pulley in the closing direction. Let it. However, since a constant tension is applied to the belt by the tension roller, the belt hinders the movement of the movable sheave of the driven pulley, and a phenomenon occurs in which the belt cannot return to the Low position until the vehicle stops. In this case, the next time you start, you must start from the intermediate gear ratio.
There may be a feeling of backlash or the inability to start on an uphill. This phenomenon is particularly remarkable in a continuously variable transmission using a dry belt.

[0005] Therefore, an object of the present invention is to provide Lo during sudden deceleration.
It is to provide a continuously variable transmission with improved w return performance. It is another object of the present invention to provide a continuously variable transmission in which the belt life is improved by adjusting the belt tension to an optimum value.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a belt is wound between a driving pulley and a driven pulley, and the belt winding diameters of both pulleys are set in opposite directions. In the continuously variable transmission, a variable speed ratio mechanism is provided, and a tensioner device for obtaining a belt tension by pressing a belt between both pulleys is provided. A tension adjusting means provided in the apparatus for adjusting a belt tension, a means for detecting a sudden deceleration of the vehicle, a means for shifting a variable speed ratio mechanism to a low speed ratio side with the rapid deceleration of the vehicle, Means for controlling the tension adjusting means in a direction to decrease the belt tension in synchronization with the shift of the variable ratio mechanism to the lower speed ratio side. According to a second aspect of the present invention, a belt is wound between a driving pulley and a driven pulley, and a speed ratio variable mechanism is provided for changing the belt winding diameter of both pulleys in opposite directions. In a continuously variable transmission for continuously changing the engine power and transmitting the power to the wheels, a tension adjusting device for adjusting the belt tension is provided in the tensioner device. The above-mentioned tension adjusting means sets an initial tension of the belt that does not cause slippage, gradually reduces the belt tension from this initial tension until slippage occurs, and maintains the belt tension just before the occurrence of slippage. To provide a continuously variable transmission.

In the first aspect of the invention, the variable gear ratio mechanism changes the belt winding diameter of the driving pulley and the driven pulley in the opposite direction, and the tensioner device prevents the belt from slipping on the pulley. Is given a predetermined belt tension. The tensioner device of the present invention does not always apply a constant belt tension. When a sudden deceleration of the vehicle is detected and the variable gear ratio mechanism starts shifting to the lower gear ratio side, the tensioner device is synchronized with the start of the gear change of the variable gear ratio mechanism. To lower the belt tension. Therefore, the load on the transmission ratio variable mechanism due to the belt tension is reduced, the shift down can be performed smoothly and rapidly, and the vehicle can be reliably returned to the Low position in a short time until the vehicle stops. In addition, as a method of reducing the belt tension, for example, there is a method of reducing the belt tension to a minimum tension at which the slip does not occur, and a method of reducing the belt tension to a value at which the slip does not occur. Is
Since the load on the variable speed ratio mechanism becomes almost zero, the downshift can be performed very quickly.

As a speed ratio variable mechanism, for example, an actuator such as a ball screw mechanism is provided behind the movable sheave of each pulley, and the actuator is driven by a speed change motor to move the movable sheave in the reverse direction, thereby changing the speed ratio. And various mechanisms such as a hydraulic servo mechanism provided behind the movable sheave to change the gear ratio by hydraulic control can be used. Further, as the tensioner device, there are a device that presses the loose side of the belt from the outside, a device that presses the loose side of the belt from the inside, and a device that presses both the loose side and the tight side of the belt. As the tension adjusting means, there are an actuator using an assist motor and a gear mechanism, an actuator using an air pressure such as an engine negative pressure, an actuator using a hydraulic pressure, and the like.

When the tensioner device applies the belt tension only by the spring force, it is necessary to determine the spring specifications so that the belt does not slip under all conditions. Be shorter. On the other hand, in the second aspect, the belt tension is reduced stepwise from the initial tension and is maintained at the tension immediately before the occurrence of slippage. Therefore, the belt tension can be easily adjusted to the minimum necessary and the belt life is improved. be able to. As a method of setting the initial tension, for example, the required belt tension may be obtained from the pulley ratio, the input torque and the number of rotations, and this may be set as the initial tension. In this case, it is possible to reduce the time required to adjust the initial tension to the final belt tension.

According to a third aspect of the present invention, there is provided a tensioner device which includes a displaceable support member, a tension roller rotatably mounted on the support member, and a tension roller contacting the belt, and urging the support member to apply the tension roller to the belt. It is desirable that the tension adjusting means be an assist motor for adjusting the belt tension by adjusting the urging force of the spring to the support member. That is, when the tension roller is pressed against the belt by the spring alone, the spring force is substantially constant, so that the belt tension cannot be freely adjusted. Therefore, the belt force is adjusted to an arbitrary value by adding or subtracting the force of the assist motor to or from the spring force. Further, since the belt tension is obtained by adding or subtracting the assist motor to or from the spring force, the belt tension can be varied over a wide range even with an assist motor having relatively small generated torque.

[0011]

1 to 4 show a specific structure of an example of a continuously variable transmission according to the present invention, and FIG. 5 shows a skeleton structure thereof. This continuously variable transmission is an FF horizontal type transmission, and generally includes a starting mechanism 2 driven by an engine output shaft 1, an input shaft 3 as an output shaft of the starting mechanism 2, a power shaft 4,
A drive shaft 10 having a drive pulley 11, a driven shaft 20 having a driven pulley 21, a V-belt 15 wound around the drive pulley 11 and the driven pulley 21, a reduction shaft 30, an output shaft 32 connected to wheels, a speed change motor. 40, a tensioner device 50 and the like. The input shaft 3, the power shaft 4, the drive shaft 10, the driven shaft 20, the reduction shaft 30, and the output shaft 32 are all non-coaxial and arranged in parallel.

The starting mechanism 2 of this embodiment is constituted by a dry clutch, and by operating the release fork 2a by a starting control motor (not shown), it is possible to perform connection / disconnection control and half-clutch control. . The input shaft 3 is rotatably supported by a transmission case 6 via a bearing, and a forward gear 3a and a reverse gear 3b provided so as to be integrally rotatable with the input shaft 3 are connected to a second gear chamber of the transmission case 6. 6c.

The power shaft 4 is provided so as to span the left and right side walls of the transmission case 6, and both ends are rotatably supported by bearings. A forward gear 4a that meshes with a forward gear 3a of the input shaft 3 is integrally provided at an end of the power shaft 4 on the engine side, and a reduction gear 4b is fixed to an opposite end of the power shaft 4 on the engine side. The reduction gear 4b of the power shaft 4 is a reduction gear 1 rotatably supported at an end of the drive shaft 10 on the side opposite to the engine.
0a, and the driving force is transmitted from the power shaft 4 to the drive shaft 10 at a reduction ratio suitable for belt driving. Reduction gear 10
a is selectively connected to the drive shaft 10 by a synchro-type forward switching unit 12 provided on the side of the drive shaft 10 opposite to the engine. That is, the switching unit 12 can switch between two positions, that is, the forward position D and the neutral position N. The reduction gear 4b, the reduction gear 10a, and the forward switching unit 12 constitute a forward direct coupling transmission mechanism 13. The forward direct coupling transmission mechanism 13 includes a first gear chamber 6 formed on the side of the transmission case 6 opposite the engine.
a. The inside of the first gear chamber 6a is lubricated with oil.

The drive pulley 11 includes a fixed sheave 11a fixed on the drive shaft 10, a movable sheave 11b supported on the drive shaft 10 so as to be movable in the axial direction, and a movable sheave 11b.
, And the actuator 14 is disposed on the engine side of the V-belt 15. The actuator 14 of this embodiment is a ball screw mechanism that is moved in the axial direction by a speed change motor 40. The actuator 14 has a female screw member 14b rotatably supported by a movable sheave 11b via a bearing 14a, and a transmission case 6. The transmission gear 14d is fixed to an outer peripheral portion of the female screw member 14b.
The transmission gear 14d is a gear having a larger diameter and a smaller thickness than the movable sheave 11b constituting the drive pulley 11.

The driven pulley 21 includes a fixed sheave 21a fixed on the driven shaft 20, a movable sheave 21b supported on the driven shaft 20 so as to be movable in the axial direction, and a movable sheave 21b.
And an actuator 22 provided behind the V-belt 15, and the actuator 22 is disposed on the side opposite to the engine with respect to the V-belt 15. This actuator 22 is also used as the drive pulley 11
A ball screw mechanism having a configuration similar to that of the actuator 14, comprising a female screw member 22 b rotatably supported by a movable sheave 21 b via a bearing 22 a, and a male screw member 22 c supported by the transmission case 6. A transmission gear 22d is fixed to an outer peripheral portion of the female screw member 22b. The transmission gear 22d is also a gear having a larger diameter and a smaller thickness than the movable sheave 21b constituting the driven pulley 21.

A reverse gear 24 is rotatably supported at a portion of the driven shaft 20 closer to the engine than the driven pulley 21. The reverse gear 24 meshes with a reverse gear 3 b fixed to the input shaft 3. . The gear 24 is selectively connected to the driven shaft 20 by a synchro-type reverse switching means 25. That is, the switching unit 25 is configured to switch the reverse position R and the neutral position N
Can be switched to the two positions. The reverse gear 3b, the gear 24, and the reverse switching means 25 constitute a reverse direct transmission mechanism 26.

A reduction gear 27 is formed integrally with the end of the driven shaft 20 on the engine side. The reduction gear 27 meshes with a gear 30 a fixed to the reduction shaft 30, and is formed integrally with the reduction shaft 30. And the ring gear 31a of the differential 31 via the gear 30b. Reduction axis 3
The speed reduction mechanism 29 is constituted by the zero gears 30a and 30b and the ring gear 31a. And the differential device 3
The wheels are driven via an output shaft 32 provided on the vehicle.
The reverse direct connection transmission mechanism 26, the reduction shaft 30, and the differential device 31 are formed on a second side formed on the engine side of the transmission case 6.
It is housed in the gear chamber 6b. The gear chamber 6b is lubricated with oil. The gear chamber 6b also accommodates a forward gear 3a of the input shaft 3 and a forward gear 4a of the power shaft 4, and is similarly lubricated.

The first gear chamber 6a and the second gear chamber 6b of the transmission case 6 are lubricated as described above, and the drive pulley 11 and the driven pulley 21 are divided into the first gear chamber 6a and the second gear chamber. 6b is disposed in a pulley chamber 6c sandwiched between the pulley chamber 6c and the pulley chamber 6b. In this embodiment, the pulley chamber 6c is a non-lubricated space,
The V belt 15 is also a dry drive belt.

To circulate the lubricating oil in the first gear chamber 6a and the lubricating oil in the second gear chamber 6b separated in the axial direction,
A supply oil passage and a return oil passage are formed by the shaft hole 4c of the power shaft 4 and the radial gap 5 between the second transmission shaft 46 and the power shaft 4 described later. Either the shaft hole 4c or the radial gap 5 may be a supply oil passage or a return oil passage. By circulating the oil in the gap 5 between the power shaft 4 and the second transmission shaft 46 in this manner, the space between the two shafts can be lubricated.

The power transmission paths of the continuously variable transmission having the above-described configuration during forward movement and reverse movement will be described with reference to FIGS. At the time of forward travel, the shift lever is operated to switch the forward switching means 12 to the forward position D. At this time, the reverse switching means 25 automatically switches to the N position. As shown in FIG. 6, the power input from the starting mechanism 2 via the input shaft 3 is transmitted by a forward gear 3a, a forward gear 4a, a power shaft 4, a forward direct transmission mechanism 13 as shown by a thick arrow.
(Reduction gear 4b, reduction gear 10a, forward switching means 1
2), drive shaft 10, drive pulley 11, V-belt 15, driven pulley 21, driven shaft 20, reduction gear 27, reduction shaft 3
0, transmitted to the output shaft 32 via the differential device 31. On the other hand, at the time of reverse travel, the shift lever is operated to switch the reverse switching means 25 to the reverse position R. At this time, the forward switching means 12 automatically switches to the N position. As shown in FIG. 7, the power input from the starting mechanism 2 via the input shaft 3 is transmitted to the reverse direct transmission mechanism 26 as shown by the thick arrow.
(Reverse gear 3b, reverse gear 24, reverse switching means 2
5), transmitted to the output shaft 32 via the driven shaft 20, the reduction gear 27, the reduction shaft 30, and the differential device 31. As will be described later, a tensioner device 50 is provided to press the loose side of the V-belt 15 to apply a belt thrust. However, when the V-belt 15 rotates in the reverse direction, the loose side also reverses, so that the tensioner device 50 presses the tension side. So, V belt 1
5 is overloaded. However, in this embodiment, the driving pulley 11, the driven pulley 21, and the V belt 1
5 is driven only when the vehicle is moving forward and is not driven when the vehicle is moving backward, so that no reverse load is applied to the V-belt 15 and the load can be reduced.

Next, the variable speed ratio mechanism in the continuously variable transmission will be described. The speed change motor 40 is provided on the outer side of the transmission case 6, in particular, a portion obliquely above the drive pulley 11.
(See FIG. 1). Speed change motor 40
Is a servomotor having a brake 41, and its output gear 42 meshes with a reduction gear 43, and these gears 42,
Reference numeral 43 is housed in a motor housing 44 lubricated with oil and is assembled in advance. The shaft portion 43a of the reduction gear 43 projects from the motor housing 44. When the motor housing 44 is fixed to the transmission case 6, the shaft portion 43a
Is fitted with a sleeve-shaped first transmission shaft 45 rotatably supported by the transmission case 6, and is connected to be integrally rotatable. Since the motor housing 44 and the inside of the transmission case 6 are isolated from each other, it is possible to prevent the lubricating oil in the motor housing 44 from flowing into the transmission case 6. A gear 45a provided on the first transmission shaft 45 is a trapezoidal gear having a length corresponding to a movement stroke of the movable sheave 11b, and a transmission gear 14a provided on the drive pulley 21.
is engaged with d. When the gear 45a of the first speed-change shaft 45 is rotated, the speed-change gear 14d is rotated to follow, so that the movable sheave 11b can be moved in the axial direction by the action of the ball screw mechanism (actuator 14). That is, the belt winding diameter of the driving pulley 11 can be continuously changed.

The speed change gear 14d of the drive pulley 11 meshes with a first idler gear 46a of a sleeve-shaped second speed change shaft 46 which is inserted into the outer periphery of the power shaft 4 so as to be relatively rotatable. The idler gear 46b meshes with the transmission gear 22d of the driven pulley 21. These idler gears 46a and 46b are also provided on the gear 4 of the first transmission shaft 45.
Like 5a, it is configured by a trapezoidal gear having a length corresponding to the moving stroke of the movable sheaves 11b and 21b. The rotational force of the transmission motor 40 is transmitted to the transmission gear 22d of the driven pulley 21 via the first transmission shaft 45, the transmission gear 14d of the drive pulley 11, and the second transmission shaft 46. for that reason,
The movable sheave 11a of the driving pulley 11 and the movable sheave 21a of the driven pulley 21 can move in the axial direction while synchronizing with each other and changing the belt winding diameter in opposite directions.

The reason for using a motor with a brake as the speed change motor 40 is that the gear train (42, 43, 45, 14d, 46a, 46a,
46b and 22d) are all constituted by reversible gears, and the gear train may rotate due to the reaction force of the movable sheave due to the belt tension and the gear ratio may change. This is to prevent rotation.

Next, a mechanism for applying a belt thrust to the V-belt 15 will be described. Pulleys 11, 21 as described above
The belt winding diameter of the V belt 15 is varied by the speed change motor 40, but the belt winding diameter of the V belt 15
And the pulleys 11 and 21 slip. Therefore, a tensioner device 50 as shown in FIGS. 3 and 4 is provided to apply a belt thrust (belt tension) according to the transmission torque. The tensioner device 50 includes a tension roller 51, and the tension roller 51 is swingably supported by an arm 53 via a link 52. The swing shaft 53a of the arm 53 is
And is urged toward the V-belt 15 by a spring 54. Therefore, the tension roller 51 presses the loose side of the V-belt 15 inward with a predetermined load. By pressing the V-belt 15 inward from the outside in this way, a predetermined belt thrust is obtained, and the V-belt 15 against the pulleys 11 and 21 is obtained.
The winding length of the belt 15 is lengthened to increase the transmission efficiency. The link 52 has a shaft 52a at one end thereof and an arm 5
The center of the tension roller 51 is rotatably supported by a shaft 52b at the other end. A gear portion 53b is formed on the outer peripheral surface of the distal end portion of the arm 53, and a pinion gear 56 of a tension adjustment assist motor 55 meshes with the gear portion 53b. The spring 54 gives an initial thrust, and the assist motor 55
Is driven in either the forward or reverse direction, so that the motor thrust is adjusted with respect to the initial thrust so that an optimum belt thrust is obtained. In the case of a vehicle having a relatively small change in transmission torque, the assist motor 55 may be omitted, and the thrust may be applied only by the spring 54. Further, the tension roller 51 is not limited to pressing the V belt 15 from the outside to the inside, but may press from the inside to the outside.

The tensioner device 50 can control the belt tension to an arbitrary value by adding an assist force of the assist motor 55 to the initial tension of the belt 15 due to the spring force of the spring 54. Assuming that the belt tension by the spring force of the spring 54 is Ts and the belt tension by the assist motor 55 is Ta, the final belt tension Tb can be expressed as Tb = Ts ± Ta. For example, Ts = 500 N · m, Ta
= 200 N · m, Tb is 300 N · m to 700
It can be variable in the range of N · m. Therefore,
Even with the assist motor 55 having a relatively small generated torque, the belt tension can be varied over a wide range.

In the case of the tensioner device 50 described above, the tension roller 51 does not interfere with the pulleys 11 and 21.
The tension roller 51 is connected to an arm 53 through a link 52.
Attached to. The reason will be described with reference to FIGS. That is, when the tension roller 51 is directly attached to the arm 53 as in the related art, the tension roller 51 moves on a rotation locus about the swing shaft 53a of the arm 53, so that the continuously variable transmission changes from low to high.
When the gear is shifted to h, the tension roller 51 may interfere with one of the pulleys. In particular, in order to reduce the load on the V-belt 15, interference is likely to occur when a large-diameter tension roller 51 is used. On the other hand, when the tension roller 51 is attached to the arm 53 via the link 52, a two-degree-of-freedom link structure is obtained, and the Low roller shown in FIG.
(Lowest speed ratio) state, Mid (intermediate ratio) state shown in FIG. 9,
At each gear ratio in the High (highest speed ratio) state shown in FIG. 10, the angle θ between the arm 53 and the link 52 automatically changes, and the tension roller 51 automatically turns the pulley 1.
It can be moved to a position where there is no interference with 1, 21. Therefore,
Even when the large-diameter tension roller 51 is used as in the embodiment, the interference between the tension roller 51 and the pulleys 11 and 21 can be reliably prevented. The link structure is not limited to the two-degree-of-freedom link structure, but may be a three-degree-of-freedom link structure using two links.

The pivot 53a of the arm 53 is arranged near the drive pulley 11 for the following reason. That is, as shown in FIG. 8 to FIG. 10, the V-belt 15
, The pressing force T1 in the vertical direction changes, and a belt tension proportional to the pressing load T1 is generated. The pressing load T1 is given as a vector sum of a spring load T2 of the spring 54 and a load T3 in a direction perpendicular to the spring load T2.
Here, the biasing force by the assist motor 55 is neglected. By arranging the swing shaft 53a of the arm 53 near the drive pulley 11 as described above, a low to high
h, the angle θ between the arm 53 and the link 52 changes, and the pressing load T1 is Mid, Hi compared to when the pressing load T1 is Low.
gh is smaller. Therefore, even when the assist motor 55 is not used, it is small during Mid and High,
It is possible to obtain a large belt tension at the time of Low.

FIG. 11 is a control system diagram for performing the speed change control and the belt tension control according to the present invention. The controller 60 is composed of an electronic control unit, and includes a foot brake signal, a throttle opening, an engine speed (input speed),
Various signals such as the vehicle speed, the rotational position of the speed change motor 40, the rotational speed of the drive pulley 11, the rotational speed of the driven pulley 21, and the rotational angle of the arm 52 are input. From the rotational position of the speed change motor 40, a calculated speed ratio (pulley ratio) is obtained. The actual gear ratio (pulley ratio) is calculated from the rotation speed signal of the driving pulley 11 and the rotation speed signal of the driven pulley 21. The belt tension Tb is estimated from the rotation angle signal of the arm 52. The controller 60 controls the speed change motor 40, the tension adjustment assist motor 55, and the like based on these input signals.

Here, a method for adjusting the belt tension to an optimum value by using the control system will be described with reference to FIG. First, the assist motor 55 is controlled based on the initial setting data to apply an initial tension γ to the belt (step S1). The initial setting data is an initial tension characteristic set for driving the belt 15 without slipping.
As shown in FIG. 3, the relationship between the effective tension of the belt and the gear ratio,
The relationship between the effective tension of the belt and the input torque and the relationship between the effective tension of the belt and the input rotation speed are stored as a three-dimensional map. In the relationship between the effective belt tension and the gear ratio,
The tension on the low speed ratio side is set to be larger than that on the high speed ratio side. Further, the relationship between the effective tension of the belt and the input torque is set so that the belt tension increases as the input torque increases. Further, the relationship between the effective tension of the belt and the input rotation speed is set so that the belt tension becomes maximum at the resonance point of the belt. Next, the controller 60 obtains a calculated speed ratio (pulley ratio) A from the rotational position of the speed change motor 40, and obtains the actual speed ratio (from the speed signal of the driving pulley 11 and the speed signal of the driven pulley 21). (Pulley ratio) B is calculated (Step S)
2). Next, the belt tension is reduced stepwise by a constant value α from the initial tension γ by the assist motor 55 (step S3). Next, it is determined whether or not a belt slip has occurred (step S4). Specifically, B / A is compared with a set value β (β> 1), and it is determined that there is no slip when B / A ≦ β, and that there is slip when B / A> β. If it is determined that the belt has not slipped, the count n is incremented by 1, and the process returns to step S3 (step S5). When it is determined that there is a belt slip, the tension γ− (n−
1) Fix the belt tension in the state of α (Step S)
6). By the above method, the optimum belt tension characteristic when the gear ratio, the input torque and the input rotation speed are changed is determined and stored in the controller 60 as a three-dimensional map.
Thereafter, if the assist motor 55 is controlled based on this map, the belt can be driven without applying excessive tension to the belt and without causing belt slippage, and the belt life can be improved. Since the belt 15 wears and elongates with time, it is desirable to update the belt tension to an optimal one by performing the above-mentioned belt tension adjustment work periodically.

Next, control for improving the low return performance at the time of sudden deceleration using the above control system will be described. In general, in the case of a V-belt type continuously variable transmission, low (minimum speed ratio) return performance during sudden deceleration is poor. The cause is, for example, when the brake is operated and the vehicle is suddenly decelerated while traveling at a high speed ratio, the continuously variable transmission tries to shift to the low speed ratio, opening the movable sheave of the driving pulley in the opening direction and closing the movable sheave of the driven pulley in the closing direction. This is because the belt is given a predetermined tension, so that the belt hinders the movement of the movable sheave of the driven pulley and cannot return to the Low position until the vehicle stops. Therefore, in the present invention, only at the time of sudden deceleration, the belt tension is temporarily reduced to a region where belt slippage occurs, and the Low return performance at the time of sudden deceleration is improved.

FIG. 14 shows an example of a shift control method during rapid deceleration. First, it is determined whether or not the foot brake has been operated during traveling (step S7). That is, there is no need to perform the control of the present invention in the case of natural deceleration, such as when decelerating without operating the foot brake. Next, it is determined whether or not the vehicle is in a rapid deceleration state (step S8). That is, when the vehicle is not decelerated while stepping on the foot brake, such as when traveling on a downhill, it is not necessary to perform the control of the present invention. When the foot brake is operated and the vehicle is in a rapid deceleration state, the speed change motor 40 is driven in the Low (minimum speed ratio) direction (step S9). Low speed motor 40
At the same time as driving in the direction, the belt is controlled to slip by the assist motor 55 (step S10). Specifically, the assist motor 55 is driven to reduce the belt tension to a value equal to or less than the slip occurrence limit value. Here, the slip occurrence limit value corresponds to γ-nα in FIG. When the belt tension is reduced to a value lower than the slip occurrence limit value, the movement of the driven pulley in the closing direction of the movable sheave becomes smooth, and the driven pulley rapidly becomes low.
Can return to position. At the time of rapid deceleration, almost no torque is applied between the driving pulley and the driven pulley, so that there is no problem in running even if the belt tension is reduced below the slip occurrence limit value. Next, it is determined whether or not the gear ratio has returned to Low (step S11). If it is determined that the position has returned to the low position, the slip control of the assist motor 55 is ended (step S12).

FIG. 15 shows another embodiment of the tensioner device. The tensioner device 70 presses the loose side of the belt 15 wound between the driving pulley 11 and the driven pulley 21 from the inside to the outside by the tension roller 73, and the belt 15 is pressed against the pulleys 11 and 21. The belt tension is applied to prevent slippage. The tensioner device 70 includes an actuator 71 having two chambers 71a and 71b separated by a diaphragm 72. A spring 74 for urging the tension roller 73 outward is disposed in one chamber 71b. The tension roller 73 is connected to the diaphragm 72 via a rod 75. The chambers 71 a and 71 b are connected to a pressure source 77 via a switching valve 76. As the pressure source 77, for example, an engine negative pressure can be used. If the engine negative pressure is used in this manner, a high belt tension can be immediately applied by guiding the engine negative pressure to the chamber 71a during engine braking. If the chambers 71a and 71b for guiding the engine negative pressure are switched by the switching valve 76, the belt tension can be adjusted according to the running state.

FIG. 16 shows still another embodiment of the tensioner device. This tensioner device 80 presses the slack side of the belt 15 wound between the driving pulley 11 and the driven pulley 21 from the inside to the outside by a tension roller 82 as in FIG. A hydraulic cylinder is used as 81. A piston rod 83 of the hydraulic cylinder 81 is connected to one end of an arm 84 supported coaxially and swingably with the driven pulley 21, and a tension roller 82 is rotatably attached to the other end of the arm 84. Inside the hydraulic cylinder 81, an arm 84 is connected to a tension roller 82 by a belt 15.
A spring 85 is provided for rotating and biasing the belt 15 in a direction in which the belt 15 is pressed against the belt 15, and applies an initial tension to the belt 15. When hydraulic pressure is supplied to one chamber 81a of the hydraulic cylinder 81, the pressing force of the tension roller 82 increases, and the belt tension also increases.
Conversely, when hydraulic pressure is supplied to the other chamber 81b, the pressing force of the tension roller 82 decreases, and the belt tension also decreases.
In this way, by switching or controlling the hydraulic pressure to the hydraulic cylinder 81, the belt tension can be freely controlled.

[0034]

As is apparent from the above description, claim 1
According to the invention described in (1), when the rapid speed reduction of the vehicle is detected and the variable speed ratio mechanism starts shifting to the lower speed ratio side, the belt tension is reduced in synchronization with the start of the speed change of the variable speed ratio mechanism. Therefore, the belt tension does not hinder the speed change operation of the variable speed ratio mechanism, and the shift down can be performed smoothly and rapidly.
It is possible to reliably return to the Low position in a short time until the vehicle stops. According to the second aspect of the present invention, the tensioner device is provided with tension adjusting means for adjusting the belt tension, and the tension adjusting means sets an initial tension of the belt that does not cause slippage, and calculates the initial tension from the initial tension. Since the belt tension is reduced stepwise until slippage occurs and is maintained at the tension immediately before slippage occurs, the belt tension can be adjusted to the minimum necessary and the belt life can be improved.

[Brief description of the drawings]

FIG. 1 is a developed sectional view of an example of a continuously variable transmission according to the present invention.

FIG. 2 is a side view of the internal structure of the continuously variable transmission of FIG.

FIG. 3 is a sectional view of a pulley portion of the continuously variable transmission of FIG.

FIG. 4 is an enlarged sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a skeleton diagram of the continuously variable transmission of FIG. 1;

FIG. 6 is a skeleton diagram showing a power transmission path of the continuously variable transmission during forward movement.

FIG. 7 is a skeleton diagram showing a power transmission path of the continuously variable transmission during reverse travel.

FIG. 8 is a diagram showing a contact position between a tension roller and a belt at a low speed ratio.

FIG. 9 is a diagram illustrating a contact position between a tension roller and a belt at an intermediate ratio.

FIG. 10 is a diagram showing a contact position between a tension roller and a belt at a high speed ratio.

FIG. 11 is a diagram showing a control system for performing speed change control and belt tension control according to the present invention.

FIG. 12 is a flowchart of a belt tension control method according to the present invention.

FIG. 13 is an initial tension characteristic diagram for belt tension control according to the present invention.

FIG. 14 is a flowchart illustrating an example of a shift control method according to the present invention.

FIG. 15 shows another embodiment of the tensioner device.

FIG. 16 shows still another embodiment of the tensioner device.

[Explanation of symbols]

 Reference Signs List 10 drive shaft 11 drive pulley 14 actuator (ball screw mechanism) 15 V belt 20 driven shaft 21 driven pulley 22 actuator (ball screw mechanism) 40 speed change motor 50 tensioner device 54 spring 55 assist motor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) F16H 59:42 F16H 59:42 59:44 59:44 59:54 59:54 59:70 59:70 63 : 06 63:06 (72) Inventor Yasuyuki Tenma 2-1-1, Taoyuan, Ikeda-shi, Osaka Daihatsu Industry Co., Ltd. (72) Inventor Masayuki Miyashita 2-1-1, Taoyuan, Ikeda-shi, Osaka Daihatsu Kogyo F term in reference (reference) 3J050 AA03 BA03 BB05 CC01 CC08 CC10 CE09 DA01 3J552 MA07 MA13 MA26 NA01 NB01 PA15 PA32 PA35 PA63 QB07 RA06 RB19 SA34 SB10 TA01 TB09 TB17 VA14W VA14Y VA17Z VA32Z VA37Z VA74Z VB01Z VC01Z VC03V

Claims (3)

[Claims] A belt is wound between a driving pulley and a driven pulley, and a speed ratio variable mechanism is provided for varying the belt winding diameter of both pulleys in opposite directions. In a continuously variable transmission that includes a tensioner device that obtains belt tension and continuously changes the engine power and transmits the power to the wheels, a tension adjustment device that is provided in the tensioner device and that can adjust the belt tension; Means for detecting deceleration, means for shifting the variable speed ratio mechanism to the lower speed ratio side in response to rapid deceleration of the vehicle, and a direction in which the belt tension is reduced in synchronization with the speed change of the variable speed ratio mechanism to the lower speed ratio side. And a means for controlling the tension adjusting means. 2. A variable speed ratio mechanism for wrapping a belt between a driving pulley and a driven pulley, and varying the belt wrapping diameter of the two pulleys in opposite directions, and pressing the belt between the two pulleys. In a continuously variable transmission that provides a tensioner device that obtains belt tension and that continuously changes the engine power and transmits the power to the wheels, the tensioner device includes a tension adjustment unit that can adjust a belt tension. , Set the initial tension of the belt that does not cause slip,
A continuously variable transmission characterized in that the belt tension is reduced stepwise from the initial tension until slippage occurs, and is maintained at the tension immediately before slippage occurs. 3. A tensioner device comprising: a displaceable support member; a tension roller rotatably mounted on the support member and in contact with the belt; and a spring for urging the support member to press the tension roller against the belt. With
The continuously variable transmission according to claim 1, wherein the tension adjusting unit is an assist motor that adjusts a belt tension by adjusting a biasing force of the spring on a support member.