KR101440848B1 - Continuously variable transmission - Google Patents

Abstract

The present invention relates to control of continuously variable vehicle transmissions. The transmission is coupled to a variator (not shown) coupled between the rotary transmission input 32 and the rotary transmission output 46 to provide continuous shifting at a transmission ratio, via a launching device such as a clutch 62, 10). The variator and launching device are configured and arranged to provide a target torque defined by the input signal. In accordance with the present invention, the same control signal is used to control both the torque capacity and the variator torque of the launching device. In such an arrangement, vehicle launching (i.e., movement from the stationary state) can be controlled in a linear manner by gradually raising the associated control signal, preferably the hydraulic signal. A method for applying the traction load to the lace 20, 22 of the variator and for setting the torque of the launching devices 62, 68 higher than the torque of the variator 10 is included in the additional subclaims.

Description

{CONTINUOUSLY VARIABLE TRANSMISSION}

The present invention relates to continuously variable transmissions. An aspect of the present invention relates to the control of a barrier variator in a transmission and of a launch device.

Continuously variable transmissions include devices that provide stepless shifting of transmission ratios. Such an apparatus is hereinafter referred to as a "variator. &Quot;

In a vehicle transmission, provision must be provided for "launching ", i. E. Accelerating the vehicle from a stationary starting point. In this regard, some transmissions rely on the use of a "launching device" such as a clutch. This serves to de-couple the driven wheel of the vehicle from the engine while the vehicle is stationary. To move the vehicle from a stationary starting point, the transmission is placed in a low gear, the engine is set to produce an appropriate torque, and the launching device is progressively engaged to increase the speed of the vehicle's driven wheel. However, the operation of such a process is somewhat complicated.

A well known alternative solution in the field of continuously variable transmissions is to apply the output of the variator to an epicyclic mixing gear, which makes it possible to achieve a condition referred to as "geared neutral" In such a gear neutral state, the transmission can effectively provide infinite speed deceleration without physically separating the transmission output from the transmission input. In this type of transmission, such launching devices are not required. Launching is accomplished simply by moving the variator ratio from the "gear neutral" value. However, essentially, such a transmission is somewhat structurally complicated with respect to gearing and has some problems with regard to control.

It would be useful to distinguish between "rate controlled" variators and "torque controlled" variators. The rate controlled variator has some physical mechanism for adjusting its own rate to reach the set value. For example, a known variator of the "half-toroidal" rolling-traction type has a position corresponding to the variator ratio and is operatively connected to the variator roller Valves having a portion operatively coupled (e.g., a valve spool) and another portion moved to set a variator ratio (e.g., a movable sleeve defining a valve port) . The valve condition depends on the relative position of these two parts, which controls the pressure applied to the piston / cylinder device acting on the valley roller. Consequently, a hydro-mechanical feedback loop, in which the valve continually compares the variator ratio to a desired value and adjusts the variator ratio to reach the target value, . The associated electronic device selects a target variator ratio and transmits a signal indicative of the ratio to the transmission.

In the torque-controlled variator, there is no such physical device for adjusting the variator ratio to the target value. Instead, the variator receives a control signal indicative of the torque to be generated. In the case of a known full-toroidal type variator as described in PCT / GB2005 / 03098 (WO 2006/027540, Torotrak Development Limited), this signal takes the form of a hydraulic pressure. In response, the variator generates a target torque at the input / output section. The actual drive ratio of the variator can be automatically changed to accommodate the speed change resulting from the application of such torque to the associated inertia. Thus, at the engine / input side of the transmission, the torque generated by the variator and the engine output torque are added to determine the net torque acting on the relevant portions and the rotational inertia of the engine, and the engine acceleration is determined. On the wheel / output side of the transmission, the torque generated by the variator is added to the torque applied from the outside due to braking, road gradients, etc., to determine the net torque that can be used for acceleration of the vehicle itself. Over-speed changes in both the input and the output include changes in variator ratios, and the variator automatically accepts them.

In a known torque-controlled type full-toroidal rolling-traction variator, the variator serves to generate a "reaction torque" corresponding to the control signal. The reaction torque is the sum of the torque at the input and output of the variator. Likewise, for spinning prevention, it may be specified to be a torque that must respond to the variator mountings.

Typically, the variator relies on traction between the rotating portions for drive transfer. For example, in the case of a toroidal-race rolling-traction variator, the rollers are frictionally engaged with toroidally-recessed variator races, and through this frictional engagement, The drive is transmitted at a variable rate. In order to provide traction between the roller and the race, they must be deflected toward each other. The biasing force used to generate the traction in the variator is called the "traction load ". In principle, a fixed traction load may be used. However, this needs to be set to a sufficiently high level to avoid excessive slip between the roller and the race under all conditions. The selected traction load value will eventually become excessive in most cases, resulting in low energy efficiency and premature wear of the rolling parts. It is common to vary the traction load according to the applied torque. More specifically, in a torque-controlled variator, it is typical that the traction rod is changed in proportion to the reaction torque. This has the advantage of providing a constant traction coefficient. Adjustments to the traction load often have to be done very quickly, in order to prevent slip from sudden "transient" events such as emergency braking. This is done in some existing systems by using hydraulic pressure to apply a traction load. Specifically, the hydraulic pressure supplied to the control piston coupled to the variator rollers is also lead to the hydraulic actuator used to create the traction load, so that the force applied to the traction rod and the valley roller It changes in sympathy.

In this type of hydraulic system, hydraulic "end stops" are generally provided to limit movement of the variator rollers and to prevent driving out of the race. This can be done, for example, by configuring the fluid outlet from the cylinder containing one of the aforementioned pistons to be closed by the piston itself when it reaches the end of the intended travel, The pressure in the cylinder serves to suppress the movement of the piston. In addition, an increased pressure is applied to the traction rod actuator, which is necessary when the change in reaction torque due to the action of the end stop must be matched by a change in the corresponding traction load, It is necessary if it should not be generated.

The present invention is intended to provide an improved CVT. More concretely (not necessarily exclusive) is to provide a DVT that is simple in configuration and simple in control.

According to a first aspect of the present invention there is provided a rotary drive system comprising a rotary input connectable to a rotary driver, a rotary output connectable to a vehicle wheel, a variator coupled between the rotary input and the rotary output to provide a continuously variable rate of drive ratio, There is provided a continuously variable vehicle transmission including a launching device arranged to selectively couple (couple) / de-couple (disconnect) the rotary input and the rotary output, the launching device comprising: Wherein the transmission comprises a control device for applying the same control signal to the variator to set the target torque and to the launching device to set the torque capacity.

The torque capacity of the launching device (the launching device may take the form of a clutch) is the maximum torque that can be delivered to the variator and is dependent on the degree of engagement in the hydraulically driven clutch (e.g., ). By controlling both the variator torques and clutches using a single signal, the equipment required for transmission control can be significantly simplified as well as facilitating the control of the launching process.

According to a second aspect of the present invention there is provided a method of manufacturing a tire, comprising the steps of: forming at least one pair of partially-toroidal recessed laces, which together form a toroidal-shaped variator cavity and are mounted for rotation on a common variator axis; There is provided a variator comprising at least two rollers disposed between said races and running on partially-toroidal-shaped recessed faces and delivering the drive therebetween at a variator drive ratio, The rollers are mounted in such a way that they can be tilted in order to vary the degree of inclination of the roller axis relative to the variator axis and to allow a continuously variable shifting of the variator drive ratio which variator has one of the races of the variator mechanically Coupled to the connecting shaft through a traction loading device, The system traction loading device serves both to transmit torque between the connection shaft and the variator race and to apply a traction load force on the race which is a function of the transmitted torque, To provide traction necessary for the delivery of the drive, characterized in that it comprises mechanical abutments that limit roller inclination.

The combination of the mechanical traction load device (instead of the hydraulic device) and the mechanical end stop (instead of the hydraulic end stop) provides a great advantage. The mechanically generated traction load can be varied with the necessary speed. A change in variator torque resulting from the action of the end stop will automatically result in an appropriate change in the traction load since it is produced in response to the torque acting on the associated variator race and does not respond to the force applied to the roller At which time it is not necessary to operatively couple the end stops to the traction loading device.

According to a third aspect of the present invention there is provided a method of controlling a continuously variable vehicle transmission comprising a rotary input connectable to a rotary driver, a rotary output connectable to a vehicle wheel, A variator coupled between the rotary input and the rotary output to provide a continuously variable transmission of the drive ratio, and a launching device arranged to selectively couple / de-couple the rotary input and the rotary output, , The method comprising controlling the variator to provide a target reaction torque and controlling the torque capacity of the launching device in sympathy with the variator reaction torque, When the torque applied to the device exceeds the torque of the launching device It is always smaller than the capacity.

This simplifies the coordinate control of the reaction torque and the torque capacity of the launching apparatus. This method also enables a highly advantageous launching method by progressively increasing the variator reaction torque and the launching device torque capacity, wherein the torque capacity of the launching device is at least sufficient for the slipping of the launching device, The torque applied by the actuator is always exceeded so that the transmission is maintained at a minimum ratio by the associated torque through the launching device.

By way of example, specific embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic illustration of a continuously variable transmission ("CVT") constructed in accordance with the present invention.
FIG. 2A is a view showing a traction load device used in a continuously variable transmission in more detail along a radial direction. FIG.
2B is a perspective view showing the rear side of the variator race.
3 is a view schematically showing a hydraulic control apparatus of a CVT.
Fig. 4 is an axial view showing specific parts of a variator used in a CVT. Fig.

1 shows a CVT using a variator 10 of a toroidal-race rolling traction type. More specifically, it is a twin cavity, full-toroidal variator. It has first and second input raceways 12, 14 having respective sides 16, 18 of a semi-toroidally recessed shape. Between the input races there are first and second output raceways 20,22 which each have a semi-toroidal recessed surface 24,26 so that the first input and output race 12 20 and a second toroidal cavity 30 is formed between the second input and output laces 22, The lace has a common axis of rotation defined by the main shaft denoted by the numeral 32 and the lace is rotated about such axis of rotation.

Each cavity 28,30 receives a set of respective rollers 34,36. Each roller is mounted for rotation about a roller axis as shown at 38 and travels on the toroidal surfaces of the associated input and output races to transfer the drive from one to the other. In addition, the mounting portions of the rollers (not shown in FIG. 1, but briefly described below) allow their inclination changes, that is, the roller shaft 38 and the main shaft 32, Lt; / RTI > The main shaft 32 acts as a rotary input for the variator and is coupled to a rotary driver (not shown in the figure through intermediate gearing or directly) such as an engine, Will have the form of an internal combustion engine as schematically shown in FIG. Likewise, the present invention may be practiced using various types of rotary drivers, such as electric motors, external combustion engines, and the like. The input race 12,14 of the variator is fixed to the main shaft 32 such that the input race 12,14 of the variator is rotated together with the main shaft 32 and driven by the engine 40. [ The output part races 20 and 22 can be rotated relative to the main shaft 32. [ This is provided in the illustrated embodiment by roller bearings 42 and 44 and output raceways are mounted to the main shaft 32 via the roller bearings 42 and 44, respectively. The drive is transferred from the input race 12,14 through the rollers 34,36 to the output race 20,22 (or vice versa under "over-run" conditions) at variable drive ratios. The output sections 20, 22 can be operatively coupled to a final drive 46 connected to the vehicle wheels, as will be briefly described below.

In the depicted variator 10, a traction rod is provided by a mechanical (non-hydraulic) traction loading device 48, which mechanical (non-hydraulic) traction loading device has a force proportional to the output torque of the variator 14, 16, 18 to engage with the varifier rollers 34, 36 using a "traction rod". This is accomplished by pressing the two innermost races (which in the illustrated embodiment are output raceways 20, 22) away from each other. The traction load is transmitted through the rollers 34 and 36 to the outermost races in which the outermost lace is the input race 12,14 which again is related to the force on the main shaft 32 So that the main shaft 32 is positioned in tension. By configuring the traction rod relative to the main shaft 32 in this manner, the need for a thrust bearing that can withstand the traction rod can be eliminated.

The traction loading device 48 utilizes a simple ramp arrangement to deliver the output torque, and this ramp arrangement is capable of moving the axial direction, which is a function of the transmitted torque (more specifically, in the present invention, proportional) Thereby creating a traction load.

2A and 2B clearly show the configuration of the traction loading device 48. As shown in Fig. The output section drive gear 50 is fixedly attached to the rear surface of the output section race 22. On the face spaced from the output portion race 22, the output drive gear 50 has a set of ramp-shaped recesses, which is shown in Fig. 2a as a dotted line 52. On its rear side, the output section race 20 has a corresponding set of ramp-shaped recesses 54, which is best seen in FIG. 2b. The recesses 52 and 54 are provided with a part-circular section as viewed in the circumferential direction as in Fig. 1, in order to accommodate the roller 56 formed as a spherical ball in this embodiment do. In the radial direction, the recesses 52 and 54 have a shallow "V" shape. When the deepest regions of the recesses 52 and 54 are aligned such that the ball 56 is located in the deepest regions of the recesses 52 and 54 as in Figure 2a, The separation of the output portion race 20 is minimized. However, the case where the variator output portion needs to withstand the torque will have to be considered. It should be noted that the output section race 20 can be rotated relative to the output section drive gear 50 by bearings 42, As the output torque causes relative rotation of these portions, the deepest regions of the recesses 52 and 54 begin to misalign and the ball 56 rises along the "V" shaped recess , Pushes the output race 20 away from the output drive gear 50 and thereby creates the required traction load. This relative rotation is interrupted when the resulting traction load is balanced by the transmitted torque. Thereby, as described above, the traction load becomes a function of the output torque. A more accurate characteristic of such a function depends on the formation of the recesses 52 and 54, one in the illustrated embodiment being proportional to the other.

The described transmission may provide both forward and reverse gears, i. E., Reversing the direction of rotation of the final drive 46. This is accomplished by providing two routes for power take off from the output sections 20,22. The first of these passes via a first set of teeth 58 formed in the output drive gear 50, the first set of teeth driving the chain gear 60 through the drive chain, The drive chain will move on the teeth 58 and the chain gear 60, though not shown in FIG. 1, for clarity. The rotated chain gear 60 is operatively coupled to one side of the forward clutch 62 and the other side of the forward clutch is operatively coupled to the final drive 46. A second route for power take-off is via a second set of teeth 64 formed on the output drive gear 50. These teeth 64 engage the gear wheel 66 and the gear wheel 66 is operatively coupled to one side of the reverse clutch 68 and the other side of the reverse clutch is again engaged with the final drive 46 ). ≪ / RTI > It should be noted that, due to the use of the drive, the first route 58, 60, 62 for power take-off does not provide an inversion of the rotational direction. Due to the use of the gear pair, the second route 64, 66, 68 for power take-off provides directional reversal. As a result, the engagement of the forward clutch 62 rotates the final drive in one direction, and the engagement of the clutch 68 rotates the final drive in the opposite direction. It should be noted that in this particular embodiment it is constructed in such a way as to prevent the forward and reverse clutches 62 and 68 from being engaged at the same time.

The final drive 46 includes a gearing 70 that is ultimately connected to a vehicle wheel (not shown).

As described above, the mounting portions for the rollers 34 and 36 are omitted in Fig. One suitable form of mounting is shown in Fig. In FIG. 4, one of the variator races 12, 14, 20, or 22 and two rollers 34 and 36 will be visible. Their position is influenced via the control lever 72, which is pivotally mounted on a fulcrum 74 received within the slot 76 of the control lever. The control lever has a lever arm 78 integrally formed with the cross-piece 80 and projecting radially as a whole to form an inverted "T" shape. At both ends of the cross-piece 80, the ball couplings 82 and 84 couple the cross-pieces to respective roller-bearers 86 and 88, And is rotatably mounted. It should also be noted that although not shown in FIG. 4, the two ball couplings 82, 84 are not located in a common radial plane. In Figure 1, the radial plane at the center of the toroidal cavity is indicated by dashed line 90. The two ball couplings 82 and 84 are each displaced from the center plane 90 and rest on both sides of the plane so that the lines from the center of each ball coupling to the respective rollers 34 and 36 And is inclined with respect to the radial plane. This inclination is called "castor angle ". It will be clear from the drawings that, when the control lever 72 is moved, correspondingly both rollers move clockwise or counterclockwise about the axis of the main shaft 32. In such a case, the rollers are subjected to a steering effect by variator races (in a manner known to those skilled in the art). As a result, both rollers are tilted about the aforementioned line / axis passing through the center of the ball coupling and roller. The steering effect on the rollers ensures that the rollers always have a tilt angle at which the axes of the rollers intersect the axis of the main shaft 32. Due to the caster angle, they are always able to find the tilt angle that provides the intersection. As a result, the tilt of the rollers (and other variator ratios) becomes a function of the position of the control lever 72.

In the configuration of Figure 4, the movement of the control lever 72, defined by the slot 76 and generally along the radial direction, is equalized by the rollers received by the individual rollers, It is important to make it possible.

An actuator 92 is used to apply a controllable biasing force to the lever arm 78. In this embodiment, the actuator 92 is a double-acting hydraulic device. That is, it accommodates two opposing hydraulic pressures, and the force exerted is determined by the deviation of these two pressures, so that the force can be left or right in FIG. It should also be noted that, in this embodiment, one actuator controls each lever 72 of both variator cavities 28,30. Although the second control lever is not shown in Fig. 4, the bar 94 extends from one control lever 72 to the other and the piston 96 of the actuator 92 pivots to the mid- Lt; / RTI > The position of the piston 96 corresponds to the position of the mid-point of the bar, but in order to equalize the roller loading between the two cavities as necessary, the relative positions of the two control levers may be slightly changed.

The hydraulic devices used to control the CVT will be described below with reference to FIG. In Figure 3, box 98 schematically represents an apparatus for providing hydraulic fluid at an adjustable pressure. Appropriate means for accomplishing this are well known to those skilled in the art. This pressure is delivered to the variator crossover valve 100 and the pressure can be applied to one side of the piston 96 through the crossover valve to press the control lever 72 in one direction or another direction. In Figure 3, the discharge from the low pressure side of the piston is shown connected to a sump 102, but in effect, to prevent all associated chambers from being emptied, It can be connected. Actuator 92 applies a force to both control levers 72, the size of which is determined by pressure feed 98 and the direction is controlled by variator crossover valve 100. By adjusting this force, control over the variator reaction torque is achieved.

The pressure from the source 98 is also transferred to the clutch select valve 104. This valve serves to selectively apply the above-described hydraulic pressure to the forward clutch 62 or the reverse clutch 68. [ An inactive clutch is exhaused to the sump 102 through the same valve. Accordingly, the clutch select valve 104 determines whether the transmission is operated forward or backward, and determines the force by which the pressure supply 98 engages the active clutch, thereby determining the torque capacity. The shutoff valve 105 between the pressure supply 98 and the clutch select valve 104 serves to selectively disconnect these parts when the vehicle is neutral.

As described above, it is common that some means are provided to limit the maximum and minimum variator ratios. In the absence of such means, there is a risk that the rollers 34, 36 will be too tilted to leave the variator races 12, 14, 20, 22, resulting in a major disaster. As described above, in the prior art, "end stops" are typically implemented hydraulically. However, in the described embodiment of the present invention, simple mechanical stops are placed on the path of travel of the roller. Specifically, these stops limit the movement of the single actuator 92, 96 used to control all of the rollers. They may in principle be of a variety of different shapes, but are shown as buffers 106 and 108 in the actuator 92 in FIG. 3, and the buffers are simply referred to as the piston 96 when it reaches the end of the transfer path will be.

The area of the piston 96 in the forward and reverse clutches 62 and 68 and the area of the pistons are adjusted so that the torque capacity of the active clutches 62 and 68 may exceed the output torque of the variator. (The latter pistons are not shown in the drawings, but the construction of a suitable clutch will be known to the person skilled in the art), and both clutches receive the same hydraulic pressure from the source 98. Accordingly, it is possible to consider what may occur during vehicle launching. Prior to launching, the pressure to the clutch select valve 104 is relieved by the shutoff valve 105. No clutch is engaged, so that the vehicle wheels are separated from the variator. In order to initiate the launching, the clutch select valve 104 is set to provide forward or reverse, the pressure supply 98 is set to a suitably low value, and then the state of the shut- . Since the torque capacity of the clutch always exceeds the output torque of the variator, as determined by the end stop buffer 106, the variator will be initially forced to apply the minimum rate. In order to avoid "clunk" caused by the clutch torque driving the variator to the end of the ratio range, the variator will have a minimum ratio The crossover valve 100 is initially set.

The engagement of the active clutch applies torque to the wheels being driven, and the vehicle thereby begins to accelerate. At some point during the launching, the state of the variator crossover valve 100 is changed so that the applied hydraulic pressure forces the piston 96 away from the buffer 106 to increase the ratio of the variator. The timing of such a change is not important as long as it is done during the sleep of the active clutch, which is maintained at a minimum rate by the torque acted upon by the active clutches 62, 68 whatever the variator is at any event during that time It will be. As the vehicle accelerates, the pressure from the source 98 gradually increases and sleeping of the active clutch is stopped at some point. Thereafter, a continuous increase in hydraulic pressure will allow the piston 96 to be moved away from the end buffer 106, thereby increasing the variator ratio as the vehicle accelerates.

During subsequent acceleration and braking, it is expected that no slipping of the active clutch will occur, since the load applied to the clutch by the variator is less than the torque capacity of its clutch.

As this effect, the management of launching can be controlled in a particularly progressive manner and a transmission which is considerably simpler than the known CVT with respect to the hydraulic system is provided.

BACKGROUND OF THE INVENTION Modern motor vehicles commonly employ electronic devices that implement a coordinated strategy for engine and transmission control. The CVT considered here could also be controlled in this way. In this example, the two most basic quantities to be controlled are the variator reaction torque (set by the pressure supply 98) and the engine output torque (set by the torque demand supplied to the engine control).

It should be understood that the foregoing embodiments are presented by way of example only, and that those skilled in the art will be able to practice the invention in many different ways. For example, the illustrated embodiment utilized a mechanical contact to limit the movement of the rollers and thus the proportion of the variator. However, it is known in the art to use a hydraulic device instead, and in such a hydraulic device, an outlet port from the actuator 92 is formed on the cylinder side so that excessive movement of the piston in both directions closes the outlet port And thus provide an end-stop function. Configurations of the same type may be used in embodiments of the present invention. In addition, although the embodiments described use mechanical ball and ramp devices to provide a traction load, such functionality may be implemented in other embodiments by hydraulic pressure. It is known, for example, to supply the same pressure to both the hydraulic pistons / cylinder devices that act on actuators 92 and one of the variator races to provide an end load, and the same is true for embodiments of the present invention .

Claims (15)

As a variator,
Wherein the variator comprises at least one pair of partially-toroidal recessed race forming together a toroidal cavity of valley, and adapted to rotate on a common variator axis, and at least one pair of recessed race- - two or more rollers running on a toroidal-shaped recessed surface and delivering the drive between them at a variator drive ratio, said rollers being arranged to vary the degree of inclination of the roller axis relative to the valley- Wherein the variator couples one of the races of the variator to the connecting shaft via a mechanical traction loading device, the mechanical traction loading device comprising: The connection shaft And the traction loading force exerts a force on the race to force the valley race to engage with the rollers and to move the valley races Characterized in that it provides traction necessary for delivery, and comprises mechanical abutments that limit roller inclination.
Barrieter.
The method according to claim 1,
Wherein the traction loading apparatus comprises first and second portions, the first and second portions being mounted for rotation about a common axis, and wherein one of the first and second portions The rotation is formed to effect axial displacement of one part relative to the other part
Barrieter.
3. The method of claim 2,
Wherein the first portion of the traction loading device includes at least one cam surface extending circumferentially and inclined relative to the radial plane and at least one follower moving on the cam surface and bearing on the second portion, Containing
Barrieter.
4. The method according to any one of claims 1 to 3,
The rollers are operatively coupled to a hydraulic piston / cylinder arrangement, the mechanical contacts being positioned to contact the piston to limit movement of the piston and to limit roller inclination
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