CN210461659U

CN210461659U - Continuously variable transmission system

Info

Publication number: CN210461659U
Application number: CN201790000943.1U
Authority: CN
Inventors: B·E·J·M·蕾纳尔特斯
Original assignee: Punch Powertrain NV
Current assignee: Nanjing Bangqi Automatic Transmission Co ltd
Priority date: 2016-06-07
Filing date: 2017-06-06
Publication date: 2020-05-05
Anticipated expiration: 2027-06-06
Also published as: WO2017211808A1; BE1023743B1

Abstract

A continuously variable transmission system for a vehicle is arranged for use during coasting. The system includes a transmission having at least one friction member configured for hydraulic actuation to apply a clamping force to a torque transmitting member coupled to the at least one friction member. The transmission is configured to inhibit hydraulic actuation of the at least one friction member during coasting while still providing a clamping force of the at least one friction member to the torque transmitting member that is sufficient to prevent slippage.

Description

Continuously variable transmission system

Technical Field

The utility model relates to a continuously variable transmission system. More specifically, the present invention relates to a continuously variable transmission system optimized for coasting.

Background

In a car, "coasting" refers to a specific manoeuvre in which the vehicle is running at a normal running speed, for example in the interval between 30km/h and 120km/h, the driver does not depress the accelerator pedal and the cruise control is deactivated. If these conditions are met for a certain period of time and the vehicle is equipped with appropriate hardware to shut down the engine and restart the engine without driver intervention, the control strategy manages the engine stop and keeps the vehicle in the coast mode until the engine restart meets the enabling conditions.

The main purpose of introducing coasting is to have a low fuel consumption. Although the driver does not depress the accelerator pedal and the cruise control does not adjust the vehicle speed, a certain amount of fuel is injected into the engine at the time of engine start to avoid engine stall. Such fuel quantities may be up to approximately 8 or 9% of the total in a typical driving cycle.

A Continuously Variable Transmission (CVT) is an automatic transmission that allows changes through a continuous range of effective gear ratios. The input from the prime mover to the input shaft can be used to deliver variable output speed and torque at the output shaft, while the input can be maintained at a constant angular rate. The CVT may include a transmission for providing mechanical power transfer. The transmission may comprise two friction members, wherein a first friction member is connected to a second friction member via a torque transmitting member such as a (push) belt or a chain. The first conical pulley may be connected to the input shaft. The second conical pulley may be connected to the output shaft. The first sheave may include a fixed sheave and an axially movable sheave. The second sheave may include a fixed sheave and an axially movable sheave. A belt, such as a segmented steel V-belt, may be provided, which is clamped between two pairs of conical sheaves of the pulley, wherein the gap between the sheaves, and thus the running radius of the belt, is adjustable by axial movement of the movable sheave. The transmission is capable of continuously changing its transmission ratio.

SUMMERY OF THE UTILITY MODEL

The object of the utility model is to provide a Continuously Variable Transmission (CVT) that carries out optimization to coasting.

In a powertrain for enabling coasting, a transmission is requested to quickly open the powertrain when coasting is enabled, and similarly, the powertrain is quickly ready to engage once the engine restarts.

According to a first aspect, a continuously variable transmission system is provided. The CVT system is arranged for use during coasting of the vehicle. The CVT system includes a transmission having at least one friction member configured for hydraulic actuation and a torque transmitting member coupled to the at least one friction member. The transmission may be arranged to inhibit hydraulic actuation of the at least one friction member during coasting whilst still providing a clamping force of the at least one friction member to the torque transmitting member, the clamping force being sufficient to prevent slippage. This provides the advantage of: during coasting, slipping of the torque transmitting member relative to the at least one friction member can be avoided. This prevents the torque transmitting member and/or the friction member from being damaged during coasting. Furthermore, inhibiting the hydraulic actuation of the at least one friction member during coasting provides the advantage of: more energy is saved during taxiing. If the oil pump has to be operated during coasting to actuate at least one friction member to provide a clamping force sufficient to avoid slipping, energy is consumed by the oil pump during coasting.

It should be understood that the oil pump can be driven by the engine. Therefore, during coasting, when the engine has stopped, the engine cannot drive the oil pump. Thus, inhibiting the hydraulic actuation of at least one friction member during coasting provides the advantage of: there is no need to provide an additional gasoline pump such as an electric oil pump. Therefore, the CVT system advantageously has no electric oil pump. Alternatively, the CVT system is arranged to stop the electric oil pump during coasting.

Optionally, the CVT system is arranged such that during coasting, the amount of oil inside the hydraulic circuit is sufficient to ensure that the mechanical components of the CVT system are lubricated.

Optionally, the CVT system includes a clutch disposed between the engine and the transmission. The CVT system may be arranged to set the clutch to a mode in which it does not transmit torque and preferably does not slip.

Alternatively, the transmission includes a first friction member coupled to an input shaft of the transmission and a second friction member coupled to an output shaft of the transmission. The first friction member may be a first conical pulley. The second friction member may be a second conical pulley. The first sheave may include a fixed sheave and an axially movable sheave. The second sheave may include a fixed sheave and an axially movable sheave. The torque transmitting member may be a belt such as a push belt or a chain. The strip may be a segmented steel V-belt. The belt may be clamped between two pairs of conical sheaves of the pulley. The gap between the sheaves and thus the belt running radius can be adjusted by the axial movement of the movable sheave. The transmission is capable of continuously changing its transmission ratio.

Optionally, the transmission is arranged to inhibit hydraulic actuation of the second friction member during coasting whilst still providing a clamping force of the second friction member on the torque transmitting member, the clamping force being sufficient to prevent slipping.

Optionally, the transmission is arranged to inhibit hydraulically actuating the first friction member during coasting, while still providing a clamping force of the first friction member on the torque transmitting member, the clamping force being sufficient to prevent slipping.

Optionally, the at least one friction member is biased such that in the absence of actuation of the at least one friction member, the clamping force of the at least one friction member on the torque transfer member is sufficient to prevent slippage of the torque transfer member relative to the friction member. The biasing can be provided by a biasing member, such as a spring, for example a biasing spring.

The biasing member is capable of applying a predetermined force to the at least one friction member such that the at least one friction member is capable of applying a clamping force to the torque transmitting member sufficient to prevent the torque transmitting member from slipping relative to the friction member. Alternatively or additionally, the biasing member can apply a predetermined force to at least one friction member to enable the transmission to produce a certain gear ratio during a coasting maneuver. The predetermined biasing force of the biasing member can be determined based on the clamping force required to prevent slippage. It should be noted that the higher the required clamping force, the higher the required biasing force. Higher biasing forces can be achieved by stiffer springs. The predetermined biasing force of the biasing member can be determined based on a geometry of the at least one friction member. For example, when the friction member is a pulley, the larger the pulley, the higher the biasing force required. The predetermined biasing force of the biasing member can be determined based on the geometry and type of the strap (e.g., chain, pushbelt).

Optionally, the CVT system comprises a Transmission Control Unit (TCU). The TCU may be configured to receive a request to enable a heading mode of the CVT system. In the event a request to enable a heading mode is received, the TCU may suspend hydraulic actuation of the at least one friction member. In the event that a request is received to enable the coast mode, the TCU may cause the clutch to enter a mode in which it is not transmitting torque and preferably not slipping. The TCU may for example bring the clutch below a so-called bite point. In one embodiment, the TCU may cause the pressure on the clutch plates to be below 0.3 bar.

The TCU may be configured to suspend hydraulic actuation of the at least one friction member until the TCU receives a request to terminate the heading mode, and resume the drive mode in which the engine provides torque. The TCU may be set to maintain the clutch in such a mode: in this mode, the clutch does not transmit torque and preferably does not slip until the TCU receives a request to terminate the coast mode and resumes the drive mode in which the engine provides torque.

According to a second aspect, a continuously variable transmission system for a vehicle is provided. The CVT system is arranged for use during coasting of the vehicle. The CVT system includes a transmission having at least one friction member configured for hydraulic actuation and a torque transmitting member coupled to the at least one friction member. The system does not have an electric oil pump for providing hydraulic pressure for actuating at least one friction member. Alternatively, the system comprises an electric oil pump for providing hydraulic pressure for actuating the at least one friction member, and the system is arranged for stopping the electric oil pump during coasting.

According to a third aspect, a continuously variable transmission system for a vehicle is provided. The CVT system includes a transmission having at least one friction member configured for actuation to apply a clamping force to a torque transmitting member coupled to the at least one friction member. The at least one friction member is biased such that a clamping force of the at least one friction member on the torque transfer member is sufficient to prevent slippage of the torque transfer member relative to the friction member in the absence of actuation of the at least one friction member. This provides the advantage of: slipping of the torque transmitting member relative to the at least one friction member can be avoided while the at least one friction member is not actuated, for example during coasting. This prevents the torque transmitting member and/or the friction member from being damaged while the at least one friction member is not actuated, for example during coasting. Furthermore, inhibiting actuation of the at least one friction member provides the advantage of energy savings.

Optionally, at least one friction member is provided for hydraulic actuation. The at least one friction member is then biased such that, in the absence of hydraulic actuation of the at least one friction member, the clamping force of the at least one friction member on the torque transfer member is sufficient to prevent slippage of the torque transfer member relative to the friction member.

Alternatively, the transmission includes a first friction member coupled to an input shaft of the transmission and a second friction member coupled to an output shaft of the transmission. The first friction member may be a first conical pulley. The second friction member may be a second conical pulley. The first sheave may include a fixed sheave and an axially movable sheave. The second sheave may include a fixed sheave and an axially movable sheave. The torque transmitting member may be a chain or a belt such as a push belt. The strip may be a segmented steel V-belt. The belt may be clamped between two pairs of conical sheaves of the pulley. The gap between the sheaves and thus the belt running radius can be adjusted by the axial movement of the movable sheave. The transmission is capable of continuously changing its transmission ratio.

Optionally, the second friction member is biased such that in the absence of actuation of the second friction member, the clamping force of the second friction member on the torque transfer member is sufficient to prevent slippage of the torque transfer member relative to the second friction member.

Optionally, the first friction member is biased such that in the absence of actuation of the first friction member, the clamping force of the first friction member on the torque transfer member is sufficient to prevent slippage of the torque transfer member relative to the first friction member.

Alternatively, the bias is provided by a spring, such as a compression spring, to press the movable sheave in the direction of the fixed sheave. It should be noted that the biasing spring may be used in continuously variable transmission systems arranged for hydraulic actuation of the sheave, which systems are not adapted to operate in a coasting mode. It should be noted that the biasing spring according to the present invention provides a higher biasing force to prevent the torque transmitting member from slipping relative to the friction member when the friction member is not hydraulically actuated. For example, the biasing spring for preventing friction may have a stiffness at least twice, preferably at least 2.5 times, that of the biasing spring that cannot be used for preventing slipping.

The present invention also relates to a drive train comprising an engine and a continuously variable transmission as described herein.

The present invention also relates to a vehicle comprising a continuously variable transmission as described herein.

The present invention also relates to a method of operating a continuously variable transmission system having a transmission with at least one friction member and a torque transmitting member coupled to the at least one friction member. The method comprises the following steps: during driving, at least one friction member is hydraulically actuated to provide a clamping force onto the torque transfer member, the clamping force being sufficient to transfer torque. The method comprises the following steps: during coasting, the at least one friction member is inhibited from being hydraulically actuated while still providing a clamping force of the at least one friction member to the torque transmitting member that is sufficient to prevent slippage. The method may include enabling a coast mode. Enabling the coast mode includes disengaging the clutch, stopping the engine, and stopping hydraulically actuating the at least one friction member. Enabling the coast mode may be controlled by the control unit. The method may include terminating the coast mode. Terminating the coast mode includes resuming hydraulically actuating the at least one friction member, starting the engine, and engaging the clutch. The termination of the coast mode may be controlled by the control unit.

It will be appreciated that any of the aspects, features and options described in terms of the CVT system apply equally to the drive train and the method described. Further, it should be apparent that any one or more of the above-described aspects, features and options can be combined.

Drawings

The invention is further elucidated on the basis of exemplary embodiments shown in the drawings. The exemplary embodiments are given by way of non-limiting illustration. It should be noted that these drawings are only schematic representations of embodiments of the invention, which are given by way of non-limiting example.

In the drawings:

fig. 1 shows a schematic diagram of an embodiment of a CVT system.

Detailed Description

Fig. 1 shows a schematic diagram of an example of a Continuously Variable Transmission (CVT) system 1. The CVT system comprises a variator 2 which allows a change through a continuous range of effective transmission ratios. The transmission 2 includes a first friction member 4 coupled to an input shaft 6 of the transmission 2 and a second friction member 8 coupled to an output shaft 10 of the transmission 2. In fig. 1, the first friction member 4 is a first conical pulley. In fig. 1, the second friction member 8 is a second conical pulley. The first pulley 4 includes a fixed sheave 4a and an axially movable sheave 4 b. The second pulley 8 includes a fixed sheave 8a and an axially movable sheave 8 b.

The first friction member 4 is connected to the second friction member 8 through a torque transmitting member 12. In this example, the torque transmitting member 12 is a chain or a belt such as a push belt. The strip may for example be a segmented steel V-belt. The strip 12 is clamped between two pairs of

conical sheaves

4a, 4b, 8a, 8b of the pulleys 4, 8.

In fig. 1, the second friction member 8, i.e., the movable sheave 8b of the second pulley 8, is biased. The biasing force is provided by a biasing member 14. In this example, the biasing member 14 is a compression spring.

In fig. 1, the CVT system 1 comprises a clutch 16 for engagement and disengagement of an input shaft 18 of the CVT system with and from the input shaft 6 of the transmission 2.

The CVT system 1 can be used as follows. When the CVT system 1 is used in a vehicle, the CVT system 1 will transmit the engine, which torque is present at the input shaft 18, to the output shaft 10 during normal driving conditions. Torque may be transferred from the output shaft 10 to one or more wheels of the vehicle. The play between the

sheaves

4a, 4b, 8a, 8b and thus the running radius of the strip 12 can be adjusted by the axial movement of the

movable sheaves

4b, 8 b. The transmission 2 can thus continuously change its transmission ratio. In order to provide sufficient clamping force between the sheaves 4, 8 and the belt 12 to avoid slipping of the belt relative to the sheaves 4, 8, the

movable sheaves

4b, 8b are clamped against the belt 12. This clamping is performed hydraulically using

hydraulic actuators

4c, 8 c. The clamping force is sufficient to prevent slippage.

The CVT system 1 can also be used during a coasting mode. The main purpose of introducing coasting is to have a low fuel consumption. While the driver is not depressing the accelerator pedal and the cruise control is not adjusting the vehicle speed, there is a certain amount of fuel injected at engine start to avoid engine stall. Such fuel quantities may amount to 8-9% of the total during a typical driving cycle. Thus, during the coast mode, the engine is stopped. Thus, no torque is provided at the input shaft 18. When coasting starts, the CVT system 1 is requested to quickly release the clutch 16. When coasting is stopped, it is similarly necessary to quickly engage clutch 16 once the engine is restarted.

In this example, the

hydraulic actuators

4c, 8c are actuated using pressurized oil. The oil is pressurized using an oil pump (not shown). The oil pump is driven by the engine. Thus, during the coast mode, when the engine is stopped, there may be insufficient oil pressure present to actuate the

hydraulic actuators

4c, 8 c. However, during coasting, the output shaft 10 is still connected to the rotating wheels of the vehicle. Thus, insufficient oil pressure may increase the risk of the belt 12 slipping with respect to the pulleys 4, 8, in particular the second pulley 8. This risk is mitigated by sizing the biasing member 14. Biasing member 14 causes the biasing force on secondary movable sheave 8b to be sufficient to prevent belt 12 from slipping relative to secondary pulley 8.

It should be noted that the biasing member may be used in continuously variable transmission systems arranged for hydraulic actuation of the sheaves, which systems are not adapted to operate in a coasting mode. It should be noted that the biasing spring 14 of fig. 1 provides a high biasing force to prevent the belt 12 from slipping relative to the second pulley 8 when the second pulley 8 is not hydraulically actuated. The choice of a stiffer spring 14 at the second pulley 8 brings benefits in terms of reliability of the system 1, since even in the case of low hydraulic forces, the stiffer spring ensures the required clamping force on the strap 12 for any critical situation. The biasing member 14 according to fig. 1 also provides that the transmission ratio of the transmission 2 can be in the desired operating range of 0.443 to 0.7 to allow a smooth restart of the engine and a smooth reengagement of the clutch 16. Furthermore, this transmission ratio allows the system 1 to operate at low primary speeds of the first pulley 4. The low primary speed may minimize centrifugal force at the input shaft 6 and, therefore, may contribute to the system 1 having low pressure on the plates of the clutch 16.

The control algorithm developed for coasting also ensures a quick restart of the transmission. The TCU monitors the driver's actions to react quickly to torque demands; thus, the TCU can quickly fill the hydraulic circuit while the engine is restarted and cause the driveline to engage in an extremely short time. This may provide the driver with a fast and smooth response to the vehicle.

It should be noted that hydraulic pressure may be provided during the coast mode using an oil pump, such as an electrically driven oil pump, which is not driven by the engine. However, the use of such an oil pump during coasting increases the energy consumption during coasting. Therefore, the CVT system 1 of fig. 1 does not have an electric oil pump. It should be noted that even if the CVT system 1 is provided with the electric oil pump, the electric oil pump can be turned off during coasting because the biasing member 14 effectively prevents slipping.

The CVT system 1 may further include a Transmission Control Unit (TCU) 20. When the coast mode is executed, the TCU20 receives a request from an Engine Control Unit (ECU) to open the driveline as quickly as possible. In such a case, the TCU needs to ensure that this maneuver is performed without damaging the transmission itself and its components. The pressure on the clutch plates of the clutch 16 is preferably below the so-called nip point, for example of about 0.3 bar, to avoid torque transfer and any slip which would lead to high heat generation and ultimately to consistent clutch wear. The pressure exerted on the second pulley 8 is preferably high enough to have a sufficient clamping force on the strip 12, which strip would otherwise eventually slip and thereby be damaged. The amount of oil inside the hydraulic circuit of the CVT system 1 is preferably sufficient to ensure continuous lubrication of the mechanical components and to have a quick restart once the coasting manoeuvre is completed.

When the conditions for the coast mode are met, the ECU may send a request to enable the coast mode to a motor Management Mode (MMU) and to the TCU 20. In this example, the TCU20 is configured to receive a request to enable a coast mode of the CVT system 1. Upon receiving a request to enable the coast mode, the TCU20 causes the clutch 16 to go below the engagement point and suspends hydraulic actuation of the pulleys 4, 8. It is also possible that TCU20 allows the actuation hydraulic pressure to be reduced due to engine shut down. The MMU can then cause the engine to stop. The CVT system 1 is now in a coasting mode.

The coast mode may be terminated when the driver actuates the accelerator or cruise control. The ECU may send a request to the TCU20 to terminate the coast mode. In the event that a request to terminate the coast mode is received, the TCU20 again hydraulically actuates the pulleys 4, 8. The MMU restarts the engine, and TCU20 engages clutch 16.

The invention is described herein with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit of the invention. Features may be described herein as part of the same or separate embodiments for clarity and conciseness of description, however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also contemplated.

For example, the TCU and/or ECU may be implemented as dedicated electronic circuits. The TCU and/or ECU may also be partially implemented as software code portions executing on a programmable computer.

However, other modifications, variations, and alternatives are also possible. The specification, drawings, and examples are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

For purposes of clarity and brevity, the drawings described herein as part of the same or separate embodiments, it is to be appreciated, however, that the scope of the present invention may include embodiments having combinations of all or some of the features described.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words 'a' and 'an' should not be construed as limited to 'only one', but are instead used to mean 'at least one', and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A continuously variable transmission system for a vehicle, the continuously variable transmission system being arranged for use during coasting, and the continuously variable transmission system comprising:

a transmission having at least one friction member configured for hydraulic actuation to apply a clamping force to a torque transmitting member coupled to the at least one friction member,

wherein the transmission is arranged to inhibit hydraulic actuation of the at least one friction member during coasting whilst still providing a clamping force of the at least one friction member on the torque transmitting member, the clamping force being sufficient to prevent slipping,

wherein an amount of oil inside a hydraulic circuit of the continuously variable transmission system is set to be sufficient to ensure continuous lubrication of mechanical components of the continuously variable transmission system.

2. The variable transmission system of claim 1, wherein the at least one friction member is biased such that a clamping force of the at least one friction member on the torque transmitting member is sufficient to prevent slippage of the torque transmitting member relative to the friction member in the absence of hydraulic actuation of the at least one friction member.

3. The variable transmission system of claim 1, wherein the at least one friction member is biased such that a gear ratio of the transmission is in a range of 0.443-0.7.

4. A continuously variable transmission system according to claim 1 or 2, characterized in that the system has no electric oil pump or that the system comprises an electric oil pump but that the system is arranged for stopping the electric oil pump during coasting.

5. A continuously variable transmission system for a vehicle, the continuously variable transmission system being arranged for use during coasting, and the continuously variable transmission system comprising:

a transmission having at least one friction member configured for hydraulic actuation and a torque transmitting member coupled to the at least one friction member,

wherein the system is free of an electric oil pump for providing hydraulic pressure to actuate the at least one friction member, or comprises an electric oil pump for providing hydraulic pressure to actuate the at least one friction member, but is arranged to stop the electric oil pump during coasting,

6. The continuously variable transmission system according to claim 5, comprising a transmission control unit arranged for receiving a request for enabling a coast mode of the continuously variable transmission system and arranged to suspend hydraulic actuation of the at least one friction member in case of receiving a request for enabling a coast mode.

7. A continuously variable transmission system as claimed in claim 6, in which the transmission control unit is arranged, on receipt of a request to enable a coast mode, to cause the clutch to enter a mode in which it does not transmit torque and preferably does not slip.

8. Continuously variable transmission system according to claim 6 or 7, wherein the transmission control unit is arranged for receiving a request for termination of a coasting mode, and is arranged to hydraulically actuate the at least one friction member in case of receiving a request for termination of a coasting mode.

9. A driveline comprising an engine and a continuously variable transmission according to any one of claims 1-8.

10. A vehicle comprising a continuously variable transmission according to any one of claims 1 to 8.