GB2585819A

GB2585819A - Vehicle drive lines

Info

Publication number: GB2585819A
Application number: GB1906964.0A
Authority: GB
Inventors: Chetwood Struve Benjamin
Original assignee: Raicam Clutch Ltd
Current assignee: Raicam Clutch Ltd
Priority date: 2019-05-17
Filing date: 2019-05-17
Publication date: 2021-01-27
Also published as: GB201906964D0

Abstract

A driveline 10 for a vehicle comprising an engine 11 connected to an input of a transmission 14 via a one-way sprag clutch 13, a launch clutch 16, and a torque converter or other launch facility being provided for the transmission. The one-way sprag clutch only delivers power to the transmission when the input speed from the engine equals or exceeds the input speed from the transmission, and the sprag clutch is lockable or has a parallel clutch to provide drive from the transmission to the engine when required to engine brake. Preferably, the one-way clutch or parallel clutch is controlled automatically to lock when brakes are applied. The one-way clutch may be locked, or the parallel clutch engaged automatically, when a battery is fully charged. If a road gradient is steep and additional braking torque is required, or a trailer is attached, the one-way clutch may be locked, or the parallel clutch may be engaged automatically. The connection to the trailer could act as a trigger to lock the one-way clutch or engage the parallel clutch.

Description

Vehicle Drive Lines This invention relates to vehicle drivelines.

In the Applicant's co-pending earlier UK patent applications Nos. 1900955.4 and 1904784.4 there are described and claim various drivelines for hybrid and non-hybrid vehicles which include a one-way sprag clutch to provide drive from the engine to the remainder of the driveline. These drivelines have one disadvantage which is the lack of engine braking.

It is an object of the present invention to overcome this disadvantage.

Thus in accordance with the present invention there is provided a driveline for a vehicle in which an engine is drivingly connected with an input of a transmission via a one-way sprag clutch to drive road wheels of the vehicle, a launch clutch, torque converter or other launch facility being provided for the transmission, and the one-way sprag clutch being arranged to only deliver power to the transmission when the sprag clutch input speed from the engine equals or exceeds the sprag clutch input speed from the transmission, the one-way clutch being lockable, or a separate clutch being provided in parallel to the one-way clutch, to provide drive from the transmission to the engine when required to provide engine braking.

Such a driveline can provide a coasting or sailing capability in which the engine becomes disconnected from the transmission when ever the input speed from the transmission exceeds the input speed from the engine allowing the engine speed to fall to idle speed (coasting) or to be switched off (sailing) thus significantly improving fuel consumption. Aso when the one-way clutch is locked or the parallel clutch engaged drive is established from the transmission to the engine to provide engine braking.

The one-way clutch or parallel clutch can be controlled manually by, for example, operation of a switch or button. Alternatively, the one-way clutch or parallel clutch can be controlled automatically so that, for example, when the brakes are applied the one-way clutch is locked or the parallel clutch engaged.

The one-way clutch can also be engaged automatically when, for example, a battery of a hybrid vehicle is fully charged as there is no longer anywhere to store the energy from regenerative braking. Also, when additional braking torque is required (for instance if the road gradient is very steep or a trailer is attached to the vehicle). It may be possible to use the connection of the trailer to the vehicle as a trigger to lock the one-way clutch or engage the parallel clutch.

The various driveline arrangements described in the above referred to Applicant's co-pending applications can all be provided with a lockable one-way clutch or a clutch in parallel with the one-way clutch.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:-Figure 1 shows schematically a basic non-hybrid vehicle driveline in accordance with the present invention; Figure 2 shows schematically a basic hybrid vehicle driveline in accordance with the present invention, and Figure 3 shows another form of hybrid driveline in accordance with the present invention.

Referring to the drawings, a driveline 10 for a vehicle has an internal combustion engine 11 which drives a flywheel 12 which drives a one-way sprag clutch 13 via a shaft 21. Clutch 13 drives a shaft 22 which in turn drives a transmission 14 and hence vehicle wheels 15 via a main launch clutch 16 and gearing 17. In the example shown clutch 16 is controlled by a clutch pedal 18 and ratios are selected in transmission 14 by a gear selector lever 19.

A lockable one-way clutch 13 transmits drive from the engine 11 to main launch clutch 16 in one direction only from the engine to the clutch 16 when unlocked but can be locked to provide drive from clutch 16 to the engine when required. A starter motor 20 engages flywheel 16 to enable the engine 11 to be started when required by the driveline control system when the vehicle is stationary and when in motion.

This simple driveline arrangement enables coasting and sailing modes to be easily provided and the fuel economy of the vehicle thus improved significantly. Also when required the one-way clutch 13 can be locked to provide engine braking. The one-way clutch 13 can be arranged to be locked automatically when the brakes of the vehicle are applied.

The vehicle can be launched by engine 11 and clutch 16 as, once the speed of shaft 21 equals or exceeds that of shaft 22, the engine 11 then powers the clutch 16 via one-way clutch 13 to allow the vehicle to make a conventional start. If the speed of shaft 22 exceed the speed of shaft 21 during use of the vehicle the engine is disconnected from clutch 16 and the vehicle operates in a coasting or sailing mode. When coasting the engine speed can be reduced to idle speed and when sailing the engine can be switched off. Starter motor 20 is used to restart the engine when required by the driveline control system.

The lockable one-way clutch could be incorporated into the launch clutch 16 to provide a more compact arrangement.

Figure 2 shows a hybrid driveline which includes a twin mass flywheel 26 to damp torsional vibrations in the driveline and the lockable one-way sprag clutch 13 is incorporated in the twin mass flywheel for further compactness. The Lockable sprag clutch 13 operates as previously described.

An electric power unit 28 is connected offset from the axis of rotation of the input shaft of the transmission via a drive belt 29. In this arrangement the electric motor is connected to the opposite end of the transmission input shaft to which the engine is connected. This allows easier packaging of the driveline without major changes to existing transmissions.

In the further alternative arrangement shown in Figure 3 the electric power unit 31 is connected with the same end of the transmission input shaft as the engine. If the electric power unit has sufficient torque to launch the vehicle under all conditions the launch clutch 16 can be eliminated as shown (giving two pedal operation of the vehicle) so that the electric power unit can occupy the space vacated by the launch clutch and its release mechanism as shown in Figure 3. This allows hybridisation of the driveline without any increase in axial length. Gear shifting intention sensors must be used to control the electric power unit and the engine to remove torque from the driveline and synchronise speeds to allow ratio changes. This requirement is particularly necessary in view of the additional inertia added to the transmission input shaft by the electric power unit. The gear shift intention sensing (e.g. on movement of the gear selector lever or the shift rails inside the transmission) as mentioned above may be augmented or replaced by an algorithm which learns driver intentions.

In the arrangements shown in Figures 2 and 3 the twin mass flywheel with integral lockable one-way sprag clutch may be deleted if vibrations in the driveline allow and replaced by a conventional flywheel and a lockable one-way sprag clutch in series.

The above hybrid driveline arrangements can be operated in an electric driving mode when sprag clutch input speed from the engine is at a lower level than the sprag clutch input speed from the electric power unit so no power flows through the sprag clutch from the engine to the transmission.

The hybrid driveline can be operated in an engine powered mode when the speed of the engine input into the sprag clutch is equal to or exceeds the sprag clutch speed from the electric power unit so that power is transmitted from the engine through the sprag clutch to the transmission, the electric power unit being optionally utilisable to also power the wheels in this mode.

In the above hybrid driveline the vehicle can be launched powered by the electric power unit when the engine switched is off so that the sprag clutch is open and the launch is achieved by the launch clutch, torque converter or other launch facility provided.

The vehicle can be launched powered by engine power passing through the sprag clutch and the launch is achieved by the launch clutch, torque converter or other launch facility provided.

Additional power can be provided by the electric power unit providing that the power unit speed input into the sprag clutch does not exceed the speed input of the engine into the sprag clutch.

The driveline can be operated in a regenerating overrunning mode in which the road wheels drive the electric power unit and the engine is running at a speed below the speed of the power unit so the sprag clutch is open and the power unit can charge an associated battery.

Although the transmission is shown in the above driveline arrangements as a manual transmission with a single launch clutch it may comprise an automatic gearbox with a torque converter or a twin clutch transmission.

Th e provision of a lockable one-way sprag clutch enables engine braking to be provided when required by locking the one-way clutch to provide drive from the transmission to the engine. The lockable one-way clutch may be replaced by a non-lockable one way clutch and another clutch in parallel with the one way clutch to provide drive from the transmission to the engine when required. For example, in Figure 1 a further clutch may be provided between the flywheel 12 and launch clutch 16.

Claims

CLAIMS1) A driveline for a vehicle in which an engine is drivingly connected with an input of a transmission via a one-way sprag clutch to drive road wheels of the vehicle, a launch clutch, torque converter or other launch facility being provided for the transmission, and the one-way sprag clutch being arranged to only deliver power to the transmission when the sprag clutch input speed from the engine equals or exceeds the sprag clutch input speed from the transmission, the one-way clutch being lockable, or a separate clutch being provided in parallel to the one-way clutch, to provide drive from the transmission to the engine when required to provide engine braking.
2) A driveline according to claim 1 in which the one-way clutch or parallel clutch is controlled automatically so that when brakes on an associated vehicle are applied the one-way clutch is locked or the parallel clutch engaged.
3) A hybrid vehicle driveline according to claim 1 in which the one-way clutch is locked or parallel clutch is engaged automatically when a battery of the hybrid vehicle is fully charged as there is no longer anywhere to store the energy from regenerative braking.
4) A driveline according to claim 1 in which the one-way clutch is locked or parallel clutch is engaged automatically when additional braking torque is required if road gradient is very steep.
5) A driveline according to claim 1 in which the one-way clutch is locked or parallel clutch is engaged automatically when a trailer is attached to the associated vehicle.
6) A driveline according to claim 5 in which the connection of the trailer to the vehicle acts as a trigger to lock the one-way clutch or engage the parallel clutch.