Patent Application
20150031501
The present teachings generally include a vehicle, configured as a hybrid-electric vehicle, having a continuously variable transmission.
In general, a continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between a maximum gear ratio and a minimum gear ratio.
A typical belt-type continuously variable transmission includes two pulleys, each having two sheaves. A belt runs between the two pulleys, with the two sheaves of each of the pulleys sandwiching the belt therebetween. Frictional engagement between the sheaves of each pulley and the belt couples the belt to each of the pulleys to transfer torque from one pulley to the other. One of the pulleys may function as a drive or input pulley so that the other pulley (an output or driven pulley) can be driven by the drive pulley via the belt. The gear ratio is the ratio of the torque of the driven pulley to the torque of the drive pulley. The gear ratio may be changed by moving the two sheaves of one of the pulleys closer together and the two sheaves of the other pulley farther apart, causing the belt to ride higher or lower on the respective pulley.
A toroidal continuously variable transmission is made up of discs and roller mechanisms that transmit power between the discs. The toroidal continuously variable transmission includes at least one input disc, connected to the engine, and one output disc operatively connected to the transmission output. The input disc and output disc define a cavity therebetween. The cavity defines a toroidal surface. The roller mechanism is placed within the cavity and is configured to vary the torque transmission ratio as the roller mechanism moves across the torodial surface. A simple tilt of the roller mechanism within the cavity changes the relative diameter of engagement of the input disc and output disc and incrementally changes the torque transmission ratio, providing for smooth, nearly instantaneous changes in torque transmission ratio. Thus, toroidal continuously variable transmissions are able to handle extremely high torques at high efficiencies.
A hybrid-electric vehicle having a continuously variable transmission is provided. The vehicle includes a first set of drive wheels and a second set of drive wheels. The vehicle further includes a primary power source having a rotatable output member for transmitting torque to the continuously variable transmission.
The continuously variable transmission is configured to transmit torque from the primary power source to the first set of drive wheels. The continuously variable transmission may be one of a belt-type continuously variable transmission and a toroidal continuously variable transmission. The continuously variable transmission further includes a forward disconnect clutch configured to selectively couple and decouple the continuously variable transmission and the first set of drive wheels.
The hybrid-electric vehicle further includes an auxiliary power source. The auxiliary power source is operatively connected to the second set of drive wheels and configured to transmit torque thereto.
A method of transitioning an all-wheel drive hybrid electric vehicle between an electric-only mode and a hybrid operating mode, i.e. completing a “flying start,” is also provided. The method comprises the steps of: detecting a request, via a controller, for a change from an electric-only operating mode to a hybrid operating mode; signaling a desired change from the electric-only operating mode to the hybrid operating mode, with the controller; starting a first electric power component to crank an engine; determining a desired engine speed and a desired engine torque to generate the desired level of transmission output torque, with the controller; engaging a forward disconnect clutch to selectively couple the continuously variable transmission with a first set of drive wheels; and powering the vehicle with torque transferred from the continuously variable transmission to the first set of drive wheels and torque transferred from a second electronic power component to a second set of drive wheels in the hybrid operating mode.
The above features and advantages, and other features and advantages, of the present invention are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the invention, as defined in the appended claims, when taken in connection with the accompanying drawings.
The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims.
Referring to Figures, wherein like numerals indicate like parts throughout the several views, a hybrid-electric vehicle 10 is provided.
The first and second electronic power components 16, 20 receive power from a power storage device 28, which is electrically interconnected therewith. The power storage device 28 is configured to transmit power to and receive power from the first electronic power component 20, transmit power to the second electronic power component 16, and provide power to other electronic devices requiring power throughout the vehicle 10.
The internal combustion engine 18 includes a rotatable output member 30 configured to transmit torque to a continuously variable transmission 32a, 32b via a transmission input member 34. The transmission input member 34 may be fluidly coupled to the rotational output member 30 via a torque converter 73.
The first electronic power component 20 may be a first motor-generator unit, as shown in the example embodiment of
The hybrid vehicle 10 further includes a second axle, which is configured as a fully electronic rear axle or a “rear e-axle assembly” 22. The rear e-axle assembly 22 is operatively independent from the engine 18, the continuously variable transmission 32a, 32b, and the first electronic power component 20. The rear e-axle assembly 22 includes the second electronic power component 16, having a second electronic power component output 24. The second electronic power component 16 may be one of an electric motor and a second motor-generator unit as shown in
The second electronic power component 16 receives its electrical energy from the power storage device 28. Accordingly, the second electronic power component 16 is configured to drive the vehicle 10 independently of the engine 18 and provides the vehicle 10 with an on-demand electric axle drive. The on-demand electric axle drive results in the vehicle 10 being operated in a purely electric vehicle or “electric-only mode.” Furthermore, when both the first axle 44 and the rear e-axle assembly 22 are driven by their respective power sources 15, 17, the vehicle 10 is endowed with all-wheel drive, and may operate in an “electric all-wheel drive mode.”
In the electric-only operating mode, the vehicle 10 operates on power supplied solely by the second electric power component 16. In hybrid operating mode, the vehicle 10 operates on power supplied by the internal combustion engine 18 and the second electric power component 16. The vehicle 10 is further capable of operating in an engine-only mode, wherein the vehicle 10 operates and is propelled via power supplied solely by the internal combustion engine 18.
The vehicle 10 is configured to operate in several powertrain configurations. The vehicle 10 may operate as a rear-wheel drive vehicle, through the use of the rear e-axle assembly 22. The vehicle 10 may operate as an all-wheel drive vehicle, through the use of the rear e-axle assembly 22 simultaneously with the front-wheel drive configuration in which torque is transmitted to the first set of drive wheels 12 from the internal combustion engine 18. The vehicle 10 may operate as a front-wheel drive vehicle, in which torque is transmitted solely to the first set of drive wheels 12 from the internal combustion engine 18.
The continuously variable transmission 32a, 32b can change steplessly through an infinite number of effective gear ratios, between a maximum gear ratio and a minimum gear ratio. The continuously variable transmission 32a, 32b is configured to transmit torque from the engine 18 and/or first electronic power component 20 to the first set of drive wheels 12. The continuously variable transmission 32a, 32b may be one of a belt-type continuously variable transmission 32a (shown in
Referring to
The belt-type continuously variable transmission 32a may further include the transmission input member 34, which is operatively connected to the output member 30 of the primary power source 15. For example, the output member 30 may be an engine crankshaft or the like which allows for the transmission input member 34 to rotate therewith.
The belt-type continuously variable transmission 32a further includes the first pulley 36. The first pulley 36 includes a first pulley axle 46 operatively connected to and configured to rotate with the transmission input member 34, when the transmission input member 34 receives a rotational input. The transmission input member 34 and the first pulley axle 46 extend along and rotate about an input axis 48. The first pulley 36 may alternatively be referred to as an input pulley or a drive pulley. The first pulley 36 is rotatable with the transmission input member 34 and first axle 46 about the input axis 48. The input pulley 36 is split perpendicular to the input axis 48 to define an annular input groove 50 therebetween. The annular input groove 50 is disposed perpendicular to the input axis 48.
The first pulley 36 includes a moveable input sheave 52, and a stationary input sheave 54. The moveable input sheave 52 is axially moveable along the input axis 48 relative to the first pulley axle 46. For example, the moveable input sheave 52 may be attached to the first pulley axle 46 via a splined connection, thereby allowing axial movement of the moveable input sheave 52 along the input axis 48. The stationary input sheave 54 is disposed opposite the moveable input sheave 52. The stationary input sheave 54 is axially fixed along the input axis 48 relative to the first pulley axle 46. As such, the stationary input sheave 54 does not move in the axial direction of the input axis 48 along the first pulley axle 46. The moveable input sheave 52 and the stationary input sheave 54 each include an input groove surface 56. The input groove surface 56 of each of the moveable input sheave 52 and the stationary input sheave 54 are disposed opposite each other to define the annular input groove 50 therebetween.
The second pulley 38 includes a second pulley axle 58, which is operatively connected to the transmission output member 42. The transmission output member 42 and the second pulley axle 58 extend along and rotate about an output axis 60. The input axis 48 and the output axis 60 are parallel with each other and spaced from each other a fixed distance 57. The second pulley 38 may alternatively be referred to as an output pulley or a driven pulley. The second pulley 38 is rotatable with the second pulley axle 58 about the output axis 60. The second pulley 38 is split perpendicular to the output axis 60 to define an annular output groove 62 therebetween. The annular output groove 62 is disposed perpendicular to the output axis 60. The second pulley axle 58 is operatively connected and configured to rotate with the transmission output member 42, when the forward disconnect clutch 35 is applied.
The second pulley 38 further includes a moveable output sheave 64, and a stationary output sheave 66. The moveable output sheave 64 is axially moveable along the output axis 60 relative to the second pulley axle 58. For example, the moveable output sheave 64 may be attached to the second axle 58 via a splined connection, thereby allowing axial movement of the moveable output sheave 64 along the output axis 60. The stationary output sheave 66 is disposed opposite the moveable output sheave 64. The stationary output sheave 66 is axially fixed along the output axis 60 relative to the second pulley axle 58. As such, the stationary output sheave 66 does not move in the axial direction of the output axis 60 along the second pulley axle 58. The moveable output sheave 64 and the stationary output sheave 66 each include an output groove surface 68. The output groove surface 68 of each of the moveable output sheave 64 and the stationary output sheave 66 are disposed opposite each other to define the annular output groove 62 therebetween.
The first pulley 36 has a first pulley diameter and the second pulley 38 has a second pulley diameter. The ratio of the second pulley diameter to the first pulley diameter defines the transmission torque ratio.
The belt-type continuously variable transmission 32a may further include clutch assembly 61 contained within a clutch housing 63. The clutch assembly 61 includes the forward disconnect clutch 35 operatively connected to the clutch housing 63, a hollow shaft 65 disposed about the transmission output member 42, and a planetary gear set 67.
The forward disconnect clutch 35 acts as a disconnect clutch, which selectively couples and decouples the continuously variable transmission 32a and the first set of drive wheels 12. When applied, the forward disconnect clutch 35 couples the clutch housing 63 and the hollow shaft 65, allowing the clutch housing 63, forward disconnect clutch 35, and the hollow shaft 65 to rotate in unison with the transmission output member 42. The hollow shaft 65 and the clutch housing 63 are further operatively connected to the planetary gear set 67 and configured to transfer torque thereto, when the forward clutch 35 is applied. Essentially, when the forward disconnect clutch 35 is applied, the clutch assembly 61 transmits the output rotation from the transmission output member 42 to the planetary gear set 67.
The continuously variable transmission 32a may further include at least one transfer gear 59 configured receive torque from the planetary gear set 67 and transmit torque to a front differential 69. The front differential 69 is configured to receive torque form the at least one transfer gear 59 and transmit torque to the first set of drive wheels 12 via an output device, i.e., the first axle 44.
When the forward clutch 35 is applied, the clutch assembly 61 transmits the output rotation from the transmission output member 42 to the first set of drive wheels 12. When the forward clutch 35 is disengaged, the output rotation from the transmission output member 42 is not transmitted to the first set of drive wheels 12. This disengagement of the continuously variable transmission 32a from the first set of drive wheels 12 allows the continuously variable transmission 32a to operate in a low loss state when the vehicle 10 is operating in electric-only mode, powered solely by the rear e-axle assembly 22.
Referring to
The toroidal continuously variable transmission 32b includes a pair of opposed drive discs 70a, 70b, a driven disc 72, and a plurality of roller mechanisms 74. The pair of opposed drive discs 70a, 70b includes a first drive disc 70a and a second drive disc 70b. The first drive disc 70a, the second drive disc 70b, and the driven disc 72 are disposed along and rotatable about the input axis 71. Each of the first drive disc 70a and the second drive disc 70b is operatively connected to and integrally rotatable with the transmission input member 34.
The driven disc 72 is disposed coaxially between the first drive disc 70a and the second drive disc 70b. The first drive disc 70a and the driven disc 72 define a first cavity 76, having a first toroidal surface 78. The second drive disc 70b and the driven disc 72 define a second cavity 80, having a second toroidal surface 82.
At least one roller mechanism 74 is disposed within each of the first cavity 76 and the second cavity 80. Each respective roller mechanism 74 is rotatable about its own respective roller mechanism axis, and is configured to transfer torque from one of the first drive disc 70a and second drive disc 70b to the driven disc 72. Each roller mechanism 74 moves along one of the respective first toroidal surface 78 and second toroidal surface 82 to vary the ratio between the speed of the transmission input member 34 and the driven disc 72.
When the roller mechanism 74 is in contact with the respective drive disc 70a, 70b near its center, the roller mechanism 74 contacts the driven disc 72 near its exterior rim 85, resulting in a reduction in speed and an increase in torque (i.e., low gear). When the roller mechanism 74 is in contact with the respective drive disc 70a, 70b near its exterior rim 86a, 86b, the roller mechanism 74 is correspondingly in contact with the driven disc 72 near its center. This results in an increase in speed and a decrease in torque (i.e., high gear).
Each respective roller mechanism 74 is operatively connected to and supported by a trunnion 84. Each trunnion 84 is configured to tilt or rotate its corresponding roller mechanism 74 about its respective roller mechanism axis. A simple tilt of the roller mechanism 74 within the cavity 76, 80 changes the relative diameter of engagement of one of the respective first drive disc 70a and second drive disc 70b and the driven disc 72, thereby incrementally changing the torque transmission ratio.
Referring to
The driven disc 72 functions as the transmission output. The driven disc 72 is operatively connected to the first transfer gear 88. The first transfer gear 88 is configured to receive torque from the driven disc 72 and further configured to transmit torque to the first intermediate shaft 90.
The toroidal continuously variable transmission 32b further includes a clutch assembly 92 contained within a clutch housing 93. The clutch assembly 92 includes a forward disconnect clutch 35 operatively connected to the clutch housing 93, a hollow shaft 95 disposed about the first intermediate shaft 90, and a planetary gear set 101.
The forward clutch 35 acts as a disconnect clutch, which selectively couples and decouples the continuously variable transmission 32b and the first set of drive wheels 12. When applied, the forward disconnect clutch 35 couples the clutch housing 93 and the hollow shaft 95, allowing the clutch housing 93, forward disconnect clutch 35, and the hollow shaft 95 to rotate in unison with the first intermediate shaft 90. The hollow shaft 95 and the clutch housing 93 are further operatively connected to the planetary gear set 101 and configured to transfer torque thereto, when the forward clutch 35 is applied.
When the forward disconnect clutch 35 is applied, the clutch assembly 92 transmits the output rotation from the first intermediate shaft 90 to the planetary gear set 101. When the forward disconnect clutch 35 is disengaged, the clutch assembly 92 does not transmit the output rotation from the first intermediate shaft 90 to the planetary gear set 101. This disengagement of the continuously variable transmission 32b from the first set of drive wheels 12 allows the continuously variable transmission 32b to operate in a low loss state when the vehicle 10 is operating in electric-only mode, powered by the rear e-axle assembly 22.
The planetary gear set 101 is configured to selectively receive torque from the first intermediate shaft 90 via the clutch assembly 92, when the forward disconnect clutch 35 is applied. The second transfer gear 94 is operatively connected to and configured to receive torque from the planetary gear set 101, when the forward disconnect clutch 35 is applied. The second transfer gear 94 may further be operatively connected to and configured to transfer torque to the third transfer gear 96. The third transfer gear 96 may be operatively connected to and configured to transfer torque to the second intermediate shaft 98. The second intermediate shaft 98 may be operatively connected to and configured to transmit torque to the fourth transfer gear 100. The fourth transfer gear 100 may be operatively connected to and configured to transmit torque to the front differential 102.
The front differential 102 is operatively connected to and may be housed within the fourth transfer gear 100. The front differential 102 is configured to receive torque from the fourth transfer gear 100 and further configured to transmit torque from the continuously variable transmission 32b to the first set of drive wheels 12, via an output device, i.e., the first axle 44.
Referring back to
The controller 150 is configured to receive a request for the engine 18 to be started, when the vehicle 10 is being driven by the rear e-axle 22, which is powered solely via the second electronic power component 16. The controller 150 is programmed to control the application of the forward disconnect clutch 35 inside the continuously variable transmission 32a, 32b. The controller 150 is further configured to control the engine 18 to generate the desired level of transmission output torque according to the selected drive mode, i.e., electric-only operating mode, hybrid operating mode, and engine-only operating mode.
Referring to
The flying start of the engine 18 is accomplished by the controller 150 that is responsible for phasing in of engine torque for driving the vehicle 10. When the vehicle 10 is driven in electric-only mode, the vehicle 10 is powered solely by the second electronic power component 16, while the engine 18 is shut-off and the continuously variable transmission 32a, 32b is placed in neutral, to operate in a low loss state in order to conserve fuel and improve the vehicle's operating efficiency. The engine 18 may be shut-off when the vehicle 10 is maintaining a steady cruising speed, which may be sustained solely by the torque output of the second electronic power component 16. Additionally, the engine 18 may be shut-off when the vehicle 10 is in a coast mode, i.e., when decelerating or the vehicle is stopped. At any time when the vehicle 10 is operating on torque supplied solely by the second electronic power component 16, the engine 18 may need to be restarted to place the vehicle 10 in hybrid mode or engine-only mode. In such situations, the engine 18 is called upon to generate an appropriate level of engine torque to result in the required amount of transmission torque, i.e., transmission torque at the transmission output 42, 72.
The flying start is accomplished by the controller 150, when the controller 150 completes the following steps, detailed in
At step 202, the controller 150 signals a desired change from the present operating mode to the target operating mode.
At step 203, the controller 150 starts the first electric power component 20 with power from the power storage device 28, allowing the first electronic power component 20 to crank the engine 18 in order to generate the desired level of transmission output torque.
At step 204, the controller 150 determines a desired engine speed and a gear ratio of the continuously variable transmission 32a, 32b to produce the desired level of transmission output torque;
At step 205, the controller 150 engages the forward disconnect clutch 35 to couple the continuously variable transmission 32a, 32b with the first set of drive wheels 12.
At step 206, the vehicle 10 is powered with torque transferred from the continuously variable transmission 32a, 32b to the first set of drive wheels 12 and torque transferred from the second electric power component 16 to a second set of drive wheels 14 in the target operating mode, i.e., the hybrid operating mode.
The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims.
