Claims:We claim
1. A electronically controlled continuously variable transmission (1000) for a motor vehicle comprising,
an actuating part (40),
an actuating part (110),
a belt (300),
a driving pulley (100) with a fixed pulley (10),
a moving pulley (20) attached to a moving boss (30),
a ramp plate (50) in frictional interaction with a crank shaft (65),
a spacer (55) being pushed against the ramp plate (50) by a drive pulley nut (70),
a driven pulley (200) with a moving pulley (115) fixed on a moving boss (125),
a fixed pulley (120) fixed on a fixed boss (170), a bush (130) positioned between the fixed boss (170) and the moving boss (125),
a pin (180) positioned in recesses (125a, 130a, 170a) provided in the moving boss (125), the bush (130) and the fixed boss (170),
the fixed boss (170) with splines (170b) interacting with splines (160a) provided on a drive shaft (160),
a fastening means (150) screwed on the drive shaft (160),
wherein said actuating part (40) is connected to the moving boss (30) via a bearing (45) and said actuator part (110) is connected to the moving boss (125) via a bearing (135).
2. A electronically controlled continuously variable transmission (1000) for motor vehicle as claimed in claim 1, wherein the actuating parts (40, 110) are linked to a linear actuator (400, 500) at a recess (40a, 110a) respectively.
3. An electronically controlled continuously variable transmission (1000) for motor vehicle as claimed in claim 2, wherein the linear actuator (400, 500) are further connected to a controller (450).
4. An electronically controlled continuously variable transmission (1000) for motor vehicle as claimed in claim 3, wherein the controller (450) is also connected to a sensor cluster (3), a sensor cluster (4), a wheel speed sensor (5) and an engine sensor cluster (6).
5. An electronically controlled continuously variable transmission (1000) as claimed in the preceding claims, wherein the controller (450) operates the linear actuator (400) to move the moving boss (30) of the driving pulley (100) and the linear actuator (500) moving the moving boss (125) of the driving pulley (200) respectively upon receiving inputs from the sensor cluster (3), the sensor cluster (4), the wheel speed sensor (5) and an engine sensor cluster (6).
, Description:FIELD OF INVENTION
The invention relates to a continuously variable transmission for motor vehicles. It more particularly relates to a continuously variable transmission whose operation is electronically controlled.
BACKGROUND OF THE INVENTION
Conventional Continuously Variable Transmissions (CVT) are known to provide a continuous stepless range of gear ratios for transmission of torque from engine to the transmission. They are most commonly used with a centrifugal clutch to allow for a smooth take-off from a standstill condition. CVTs themselves use a combination of centrifugal masses and springs to provide the required force for changing the gear ratio. The change in gear ratio occurs in accordance with the initially established balance between thrust forces on the driving pulley, spring force on driven pulley and thrust force on the driven pulley. This balanced setting does not necessarily account for the subsequent wear and tear of the moving components in a CVTs. Furthermore, once such balanced setting is decided, it cannot be altered without changing the centrifugal masses and the springs. Conventional CVT’s are hence not readily adaptable to change in driving requirements. Given that there is also a certain amount of belt slip that happens in any CVT, efficiency of torque transmission in them is also less as compare to a manual transmission. This tends to increase the fuel consumption as well.
To solve these problems numerous CVTs have been developed which use centrifugal masses and spring based mechanism in combination with actuators that are electronically operated. They are commonly identified as Electronically Controlled Continuously Variable Transmissions (ECVT). Logic for operation of the ECVTs can be programmed into the electronic components. It is worth noting that utilisation of rotating masses still does complicate the operation of the ECVTs. This is for the reason that inertia of the rotating masses still has to be accounted for by the electronic controller while changing the gear ratio. It must be noted that the rotating masses do not consistently function to support the operation of the electronically controlled actuator, the consumption of power to operate an ECVT tends to be high in driving conditions corresponding to city driving. In the ECVT disclosed by the Indian patent application 201717031142, the centrifugal masses (3 and 4) tend to decrease the power consumed by the adjustment drive (50) to increase the pulley diameter while accelerating. The same centrifugal masses (3 and 4) tend to increase the power consumption by the adjustment drive (50) to change the pulley diameter during deceleration.
In another ECVT disclosed in the Indian patent application 201717030599, an adjustment device (5) comprising of a servo drive (50), a spindle (30), a spindle nut (31) and a lever (4) has been provided. The servo drive’s (50) axis is parallel to the axis of rotation of the movable cone pulley (21). It is therefore required to be linked with a spindle (30), spindle nut (31) and a lever (4). The lever (4) then connects with a bearing bush (8). The position of the moveable cone pulley (21) connected with the bearing bush (8) changes when the servo drive (50) operates. Even though the mechanism does away with the centrifugal masses it uses a servo drive (50), a spindle (30), a spindle nut (31) and a lever (4) for changing the gear ratio. Therefore, the number of components still remains high. It may also be noted that in the disclosed ECVT, the lever (4) essentially acts as a cantilever and is under stress during operation. The complexity of construction of the ECVT being high, the ECVT disclosed may not be easily manufactured and readily provided in motor vehicles.
It can be observed that none of the prior art mechanisms are compact enough to be used on both the driving and driven pulley without greatly increasing the overall size of the transmission. It is therefore an object of the current invention to provide a compact mechanism for an ECVT in which both the driving and driven pulley diameters can be varied by electronically controlled actuators.
It is another objective of the current invention to provide an ECVT that is readily adaptable to changing operating conditions to give maximum torque transmission efficiency.
It is yet another objective of the current invention to provide an ECVT for a motor vehicle that reduces fuel consumption.
It is still objective of the current invention to provide an ECVT for a motor vehicle that has a simple construction with reduced number of parts.
It is one more objective of the current invention is to provide an ECVT that can be easily manufactured and readily provided in a motor vehicle.
SUMMARY OF THE INVENTION
A electronically controlled continuously variable transmission for a motor vehicle is disclosed which comprises of a driving pulley with a fixed pulley , a moving pulley attached to a moving boss, a ramp plate in frictional interaction with a crank shaft, a spacer being pushed against the ramp plate by a drive pulley nut, a driven pulley with a moving pulley fixed on a moving boss, a fixed pulley fixed on a fixed boss, a bush positioned between the fixed boss and the moving boss, a pin positioned in recesses provided in the moving boss and the fixed boss, the fixed boss with splines interacting with splines provided on a drive shaft, a nut screwed on the drive shaft and a belt for transmitting torque between the driving and driven pulleys. The ECVT is provided with actuating parts connected to the moving bosses via a bearings.
Typically, the actuating parts are also connected to the linear actuators provided for them.
Typically, the linear actuators provided are further connected to a controller.
Typically, the controller is further connected to the sensor clusters provided for the driving and driven pulley, a wheel speed sensor and an engine sensor cluster.
The controller operates the linear actuators to effect a change in diameters of the driving and driven pulleys. The belt length being constant, the change in diameter of the driving and driven pulleys allows the ECVT to achieve different gear ratios. The need for providing a centrifugal clutch is eliminated as the driving and driven pulley diameters can be altered to allow belt slip as required.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1a illustrates a known ECVT.
Figure 1b illustrates another known ECVT.
Figure 2a illustrates the isometric view of ECVT as per an embodiment of the current invention.
Figure 2b illustrates the layout of the ECVT as per an embodiment of the current invention.
Figure 3a illustrates the isometric view of driving pulley as per an embodiment of the current invention.
Figure 3b illustrates the cross-sectional view of driving pulley as per an embodiment of the current invention.
Figure 4a illustrates the isometric view of driven pulley as per an embodiment of the current invention.
Figure 4b illustrates the cross-sectional view of driving pulley as per an embodiment of the current invention.
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiment of the an Electronically Controlled Continuously Variable Transmission (ECVT) will now be described with reference to accompanying diagrams. The preferred embodiment must not be viewed as restricting the scope of and ambit of the disclosure.
ECVTs utilise a combination of centrifugal masses, springs and electronically controlled actuators to change the diameter of the driving and driven pulleys. In the ECVT disclosed in the Indian patent application 201717031142 (as shown in figure 1a), the centrifugal masses (3 and 4) tend to negatively affect power consumed by the adjustment drive (50) in city like driving conditions. In another ECVT disclosed in the Indian patent application 201717030599 (as shown in figure 1b), the use of centrifugal masses in combination with an electronically controlled actuator to change the pulley diameter has been eliminated. An adjustment device (5) comprising of a servo drive (50), a spindle (30), a spindle nut (31) and a lever (4) has been provided instead. Even though the mechanism does away with the centrifugal masses the number of sub-components provided still remains high. These disclosed mechanisms cannot be provided on both driving and driven pulley without significantly increasing the overall size of the ECVT. Furthermore, they have a complicated construction which reduces their ease of manufacturing. Therefore, they may not be readily provided in motor vehicles. In order to overcome these shortcomings and other stated limitations, an ECVT (1000) is hereon described. The ECVT (1000) may be readily provided in two, three and low powered four wheelers motor vehicles.
The ECVT (1000) as per the current invention primarily comprises of a driving pulley (100), a driven pulley (200) and a belt (300) (refer figure 2a). In addition to these stated mechanical components it further comprises (refer figure 2b) of a linear actuator (400) for driving pulley, a controller (450), a linear actuator (500) for driven pulley, a sensor cluster (3) for driving pulley (for sensing position and RPM), a sensor cluster (4) for driven pulley (for sensing position and RPM), an engine sensor cluster (6) for motor vehicle engine (2) (for sensing the engine RPM, fuel consumption, torque etc.), a wheel speed sensor (5) (for sensing RPM of the wheel (700)).
The controller (450) (refer figure 2b) receives its input from the sensor cluster (3) for the driving pulley (100), the sensor cluster (4) for the driven pulley (200), the engine (2) an engine sensor cluster (6) and the wheel speed sensor (5). It transmits its output to the linear actuator (400) for driving pulley (100) and the linear actuator (500) for driven pulley (200). The belt (300) length being constant, the operation of the linear actuator (400) and the linear actuator (500) in unison varies the gear ratio and torque transmitted by the ECVT (1000). The torque is transmitted from the engine (2) to the driving pulley (100) then through the belt (300) to the driven pulley (200). The driven pulley (200) transmits the torque to a reduction gear series (600) before it is further transmitted to the wheel (700).
The driving pulley (100) (as shown in figure 3a) is provided with a fixed pulley (10), air circulation ribs (15), a moving pulley (20), a moving pulley boss (30), a support ring (35) and an actuator part (40). The fixed driving fan (15) fixed on the fixed pulley (10) circulate air within the ECVT (1000) when the driving pulley (100) rotates. This keeps the temperature of the ECVT (1000) mechanism within an acceptable limit. As shown in figure 3b, a ramp plate (50) is fixed over the crank shaft (65) by a spacer (55), a washer (75) and a drive pulley nut (70) during the assembly. The drive pulley nut (70) screwed over the crank shaft (65) pushes the spacer (55) against the ramp plate (50) which then comes in a firm frictional contact with a surface (65a) of the crank shaft (65). The ramp plate (50) has a recess (50a) which is capable of sliding over a projection (20a) provided on the moving pulley (20). The interaction between the ramp plate (50) and the moving pulley (20) via the recess (50a) and projection (20a) enables the ramp plate (50) to transfer torque to the moving pulley (20).
The moving pulley (20) (refer Figure 3b) is attached to the moving pulley boss (30). A bush (60) is provided between the moving pulley boss (30) and the spacer (55). The bush (30) allows the moving pulley boss (30) to slide over the spacer (55). The lugs (30a) of the moving pulley boss (30) pass through the openings (10a) provided in the fixed pulley (10). The lugs (30a) are supported by a support ring (35) separately provided on the drive pulley nut (70). The actuator part (40) is attached to the moving pulley boss (30) via a bearing (45). The circlips (44 and 46) fix the bearing (45) firmly over the moving pulley boss (30) and the actuator part (40). The actuator part (40) is further linked with the liner actuator (400) at recess (40a). The actuator part (40) moves the moving pulley boss (30) when the linear actuator (400) is operated by the controller (450). The controller (450) can therefore effect changes in the diameter of the driving pulley (100).
The driven pulley (200) (as shown in figures 4a and 4b) comprises of an actuator part (110), a moving pulley (115), a fixed pulley (120) and a fixed boss (170). It is further provided with the sub-components (refer figure 4b) a moving boss (125), a bush (130), a circlip (134), a bearing (135), a circlip (136), a washer (140), a fastening means (150) (which may be a nut), a drive shaft (160) and a pin (180). The fixed pulley (120) is fixed over the fixed boss (170). The fixed boss (170) is provided with splines (170b) on its inner surface which interact with the corresponding splines (160a) provided on the outer surface of the drive shaft (160). The fastening means (150) screwed over the drive shaft (160) with the washer (140) prevents any movement of the fixed boss (170) over the drive shaft (160).
The moving pulley (115) is fixed over the moving boss (125). A pin (180) (shown in figure 4b) passes through a recess (125a) in the moving boss (125), a recess 130a in the bush 130 and a recess (170a) in the fixed boss (170). A retainer cup (145) provided over the moving boss (125) prevents the pin (180) from coming out. The recess (170a) is larger than the recess (125a). This allows movement of the moving boss (125) over the fixed boss (170) in the limits defined by interaction of the pin (180) and the recesses (125a, 130a and 170a). A bush (130) is fixed within the moving boss (125). The bush (130) allows the moving boss (125) to slide over the fixed boss (170). The actuator part (110) is linked to the moving boss (125) via a bearing (135). The circlips (134 and 136) hold the bearing (135) in its position between the actuator part (110) and the moving boss (125). The actuator part (110) is further linked with the linear actuator (500) at the recess (110a). The actuator part (110) moves the moving boss (125) when the linear actuator (500) is actuated by the controller (450). The controller (450) can therefore effect changes in the diameter of the driven pulley (200).
The construction of the driving and driven pulley (100 and 200) allows linear actuators (400 and 500) to be provided for effecting change in their respective diameter. This eliminates the need for utilising centrifugal masses as provided in conventional CVTs. Their construction also eliminates the need for providing screw based mechanisms with motors either alone or in combination with centrifugal masses as provided in conventional ECVTs. The set of steps associated with manufacturing and assembling them are therefore also eliminated. This makes the ECVT (1000) comparably easier to manufacture and provide in two, three and low powered four wheeler motor vehicle. Furthermore, the driving and driven pulley (100 and 200) can be bought into a home position where their diameter is such that the belt (300) continuously slips over both the pulleys. This eliminates the need to provide a centrifugal clutch for facilitating a smooth take-off of the motor vehicle from stand still condition.
The ECVT (1000) operation starts after the motor vehicle is started and a throttle input is provided by the motor vehicle operator. The throttle input provided effects a change in the engine (2) RPM. The engine sensor cluster (6) (refer figure 2b) senses the change in engine (2) RPM and provides an input to the controller (450). Based upon the continuous inputs from sensors (3, 4, 5 and 6) (refer figures 2b), the controller (450) causes the operation the linear actuators (400, 500). The position of the moving boss (30) and the moving boss (125) respectively linked to the linear actuator (400) and the linear actuator (500) therefore changes. The driving and driven pulley (100 and 200) diameter is hence adjusted by the controller (450) to transmit the engine (2) output as required. The engine (2) output is then transmitted to the reduction gears (600) via the ECVT (1000). The reduction gears (600) then transmit the output to the wheel (700). In event there is no change in inputs from the sensors (3, 4, 5 and 6), further operation of the linear actuators (400, 500) stops. The ECVT (1000) therefore allows the engine to operate in its efficient RPM range. The ECVT (1000) also eliminates the need for providing a centrifugal clutch for ensuring smooth take-off of the vehicle at the time of the starting of the motor vehicle.
Controlling both the driving and driven pulley (100 and 200) diameter allows the ECVT (1000) to achieve a better torque transmission efficiency. It also makes the ECVT (1000) more adaptable to change in driving conditions. This reduces the overall fuel consumption as engine operates in its efficient RPM range. It is can also be noted that the ECVT (1000) does not have any centrifugal masses and screw based mechanisms with motors for effecting change in the driving and driven pulley diameters. This reduces the total number of components and the size of the ECVT as compared to a conventional ECVT. It also eliminates the steps of manufacturing and assembling these sub-components into the ECVT. The ECVT (1000) is therefore easier to manufacture and provide in two, three and low powered four wheeler motor vehicle.
List of Reference Numbers
2 – Engine/ power unit
3 – Sensor cluster
4 – Sensor cluster
5 – Wheel speed sensor
6 – Engine sensor cluster (rpm, fuel consumption, torque etc.)
10 – Fixed pulley
10a- Openings
15 – Fixed driving fan
20 – Moving pulley
20a- Projection
30 – Moving pulley boss
30a - Lugs
35 – Support ring
40 – Actuator part
40a- Recess
44 – Circlip
45 – Bearing
46 – Circlip

50 – Ramp plate
50a- Recess
55 – Spacer
60 – Bush
65 – Crank shaft
65a – Surface
70 – Drive pulley nut
75 – Washer
80 – Washer
100 – Driver pulley assembly
110 – Actuator part
110a- Recess
115 – Moving pulley
120 – Fixed pulley
125 – Moving boss
125a- Recess
130 – Bush
130a- Recess
134 – Circlip
135 – Bearing
136 – Circlip
140 – Washer
145 – Retainer cup
150 – Fastening means
160 – Drive shaft
160a- Splines
170 – Fixed boss
170a- Recess
170b- Splines
180 – Pin
200 – Driven pulley assembly
300 – Belt
400 – Linear actuator for
450 - Controller
500 - Linear actuator for
600 – Reduction gears
700 – Wheel
1000 –ECVT