Driver-aid method and device for shifting gears in an automatic transmission

A driver-aid method for shifting gears in an automatic transmission, wherein an automatic operating mode of the automatic transmission provides for shifting automatically by means of an optimization strategy based on information signals. Manual shifting of the gears of the vehicle by means of a control device is permitted even in automatic operating mode: a) if the shift requested manually by the driver is compatible with the set optimization strategy, a physical return is transmitted to the driver informing the driver of the compatibility of the shift requested; and b) if the shift requested manually by the driver is not compatible with the set optimization strategy, a physical return is transmitted to the driver informing the driver of the incompatibility of the shift requested.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a driver-aid method and device for shifting gears in an automatic transmission.

2. Related Art

As is known, vehicles with automatic transmissions are equipped with driver shift control devices on the driver's side.

For example, control devices are known comprising one or more levers enabling sequential shift of the automatic transmission by the driver, while others simply comprise manually operated buttons (normally two).

The control devices also provide for setting an automatic operating mode, in which shift is performed automatically by an automatic control according to a given optimization strategy.

Automatic transmissions of the above type normally also permit manual shift, even when an automatic shift strategy is operative.

In this case, however, the automatic shift strategy intervenes regardless, and the driver may only “anticipate”, but never prevent or delay, an automatic control strategy shift.

There is also a fully manual operating mode, in which shift is controlled fully independently by the driver, and automatic shift only comes into play in extreme situations, e.g. to prevent damage to the engine (engine speed too high) or to prevent the engine stalling (engine speed too low).

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a driver-aid method and device for shifting gears in an automatic transmission, which indicates to the driver the compatibility of a manual shift with a pre-set, currently operating optimization strategy.

According to an aspect of the present invention, there is provided a driver-aid device for shifting gears in an automatic transmission, including a control system which controls said automatic transmission, and which provides for an automatic operating mode of the automatic transmission wherein shifting is performed automatically by means of an optimization strategy based on information signals;

a control device being provided for manually shifting the gears on the vehicle;

including a device which scrutinizes the shift requested by the driver by means of said control device:if the shift requested manually by the driver is compatible with the set optimization strategy, a first signal (S1) is generated to transmit a physical return to the driver informing the driver of the compatibility of the shift requested, and the proposed shift is performed upon operation of said control system; andif the shift requested manually by the driver is not compatible with the set optimization strategy, a second signal (S2) is generated to transmit a physical return to the driver informing the driver of the incompatibility of the shift requested, and the proposed shift is performed after operation of said control system.

BRIEF DESCRIPTION OF THE DRAWINGS

A non-limiting embodiment of the invention will be described purely by way of example with reference to the accompanying drawing, which shows a block diagram of an automatic power train featuring a gear shift driver-aid device in accordance with the teachings of the present invention.

DETAILED DESCRIPTION

Number1in the accompanying drawing indicates as a whole a gear shift driver-aid device, in which a gear shift control device2of an automatic transmission cooperates, via data exchange along a data line D, with an electronic central control unit3controlling an automatic transmission assembly4.

Automatic transmission assembly4receives mechanical power from a shaft (not shown) of an internal combustion engine5(petrol or diesel fuel), and comprises a transmission6, and a clutch7interposed between an output shaft of engine5and the input shaft of transmission6which supplies mechanical power to the wheels of a vehicle (not shown).

Engine5cooperates with an electronic engine control circuit8which receives a number of information parameters INFO (engine speed, cooling water temperature, etc.) measured on engine5, and supplies control signals to an ignition system ACC (shown schematically) and to an injection system INJ (also shown schematically).

Electronic central control unit3cooperates with electronic engine control circuit8, to which it is connected over a two-way data transmission line9, and is also connected to sensors10for measuring parameters, such as vehicle speed, accelerator pedal position, and the pressure and temperature of a hydraulic circuit (not shown) supplying automatic transmission assembly4.

Electronic central control unit3is also connected to an actuator control device11for controlling shift of transmission6and release/engagement of clutch7in known manner by means of respective actuator assemblies11a,11b(shown schematically).

Central control unit3may also provide a conventional automatic operating mode of transmission assembly4, whereby the shift strategy is optimized by shifting automatically on the basis of information signals (e.g. engine speed, accelerator pedal position, vehicle speed) with no manual control on the part of the driver. Electronic central control unit3may also provide a special operating level of transmission assembly4(a racing operating mode), wherein gear shifting and engagement of clutch7are performed rapidly to simulate racing-type manual operation of the transmission assembly. Further, electronic central control unit3may provide a semiautomatic operating mode, as described below.

Electronic central control unit3is connected to control device2, which is fitted, for example, to a steering column control assembly13extending from the dashpanel14(shown partly and schematically) of the vehicle (not shown) and housing the steering column17of the vehicle (partly shown).

The steering column is fitted integrally at one end with a steering wheel14a, which is located at one end of steering column control assembly13, and is coaxial with a longitudinal axis A of the steering column.

Control device2comprises at least one lever15,16operated by the driver to shift gear and to select the operating mode of transmission assembly4(automatic or semiautomatic). When semiautomatic operating mode is selected, lever15,16also permits manual alteration of the automatic shift.

In the example shown, lever15,16is also connected to steering column control assembly13, but may obviously be located anywhere within the passenger compartment of the vehicle.

More specifically, in the example shown, a first and a second lever15,16are fitted to steering column control assembly13to enable the driver of the vehicle (not shown) to control transmission assembly4. Alternatively, the first and second lever15,16may be fitted to steering wheel14a.

More specifically, control device2generates signals which are interpreted by central control unit3to control transmission assembly4, and in particular:an up-shift signal UP to shift up, for example, one gear;a down-shift signal DWN to down-shift, for example, one gear;a neutral signal NTRL to shift transmission6into neutral; anda reverse signal REV to shift transmission6into reverse.

The first and second lever15,16also enable the driver of the vehicle to select (in known manner) a first and second operating mode of transmission assembly4, known as automatic shift mode and semiautomatic shift mode respectively, by transmitting a SWITCH signal to electronic central control unit3.

In semiautomatic shift mode, shifting of transmission6is performed manually by the driver by means of first and second lever15,16.

In automatic shift mode, shifting of transmission6is controlled entirely by electronic central control unit3, which, as stated, implements a shift optimizing strategy to increase or decrease the transmission ratio (according to known optimization strategies) as a function of given input parameters, such as vehicle speed, accelerator pedal position, vehicle load, and/or slope of the road along which the vehicle is travelling, etc.

On receiving the SWITCH signal with the transmission assembly in semiautomatic shift mode, electronic central control unit3disables semiautomatic shift mode and enables automatic shift mode.

On receiving the SWITCH signal with transmission assembly4in automatic shift mode, electronic central control unit3disables automatic shift mode and enables semiautomatic shift mode.

First and second lever15,16also enable the driver of the vehicle to select a first and second performance level of transmission assembly4by means of a PERF signal. More specifically, the first performance level, known as basic operating mode, allows the driver to select a first release/engage speed of clutch7and a first shift speed; and the second performance level, corresponding to racing operating mode, allows the driver to select a second release/engage speed of clutch7and a second shift speed. The first speed in basic operating mode is lower than the second speed in racing operating mode.

On receiving the PERF signal with transmission assembly4in basic operating mode, electronic central control unit3disables basic operating mode and enables racing operating mode; and, conversely, on receiving the PERF signal with transmission assembly4in racing operating mode, electronic central control unit3disables racing operating mode and enables basic operating mode.

When automatic operating mode is activated, in which shifting is performed automatically according to a predetermined known strategy, electronic central control unit3also permits manual up- or down-shifting.

When the above strategy is operative, however, the driver can only “anticipate”, and never prevent or delay, an automatic optimization strategy shift.

The driver's “suggestion”, however, is implemented by comparing the gear requested by the driver manually operating lever15,16with the proposed (automatic strategy) gear, to determine (by known comparing operations) whether the requested shift is compatible with the set automatic optimization strategy.

More specifically:if the shift requested manually by the driver is compatible with the set automatic shift strategy, a control signal S1for controlling control device2is generated whereby movement of one (or both) of levers15,16involves very little effort, and, once the lever15,16is moved, the shift is commanded and actually performed; andif the shift requested manually by the driver is not compatible with the set automatic shift strategy, a control signal S2for controlling control device2is generated whereby movement of one (or both) of levers15,16involves greater effort, and, once the lever is moved, the shift is commanded and actually performed.

Alternatively, a device may be provided to vibrate lever15,16in the presence of control signal S1(or S2) and produce a tactile sensation immediately informing the driver that the proposed gear is compatible (or incompatible) with the set automatic optimization strategy.

A “physical” return (stiffening or vibration of the levers), i.e. a force feedback in reaction to action by the driver, is thus transmitted to the driver by means of levers15,16.

In the example shown, the driver realizes immediately when a shift is incompatible, by having to exert extra force to move lever/s15,16.

The driver may therefore push lever15,16with a minimum amount of effort, when the shift is compatible; the lever yields, and the shift is performed. By exerting greater force on lever15,16, the shift may be performed at any time.

The above operating mode of lever15,16provides for maximizing vehicle performance by telling the driver the right time to perform a given shift.

One possible physical embodiment, for example, may comprise a return spring20,21on lever15,16, and, in series with spring20,21, an electromagnetic actuator24,25which, when energized (in the presence of signal S2), compresses the spring to increase the resistance to movement of lever15,16. Once lever15,16is moved, the shift signal is generated.

Alternatively, a mechanism may be provided to preload return spring20,21of the lever, and which is activated in the presence of signal S2, with a shape-memory actuator (not shown).

In another embodiment, lever15,16may move from a rest position to an intermediate semistable position (achieved in known manner, for example, by means of a ball held by a spring inside a seat—not shown), and from there to a final shift position by means of further manual control. As before, the stiffness of the spring is regulated to permit movement with a minimum amount of effort into the final position in the presence of signal S1, and with greater effort in the presence of signal S2.

If shift is button-controlled, tactile feedback may be by vibrating the button. In this mode, in fact, the driver tends to keep one finger (thumb or forefinger) on the button to shift rapidly, so that vibration indicates the right time to press the button according to the set optimization strategy.