WO1991015377A1

WO1991015377A1 - A device for operating a motor-vehicle gearbox

Info

Publication number: WO1991015377A1
Application number: PCT/EP1991/000591
Authority: WO
Inventors: Giovanni Nicodano
Original assignee: Giovanni Nicodano
Priority date: 1990-03-30
Filing date: 1991-03-27
Publication date: 1991-10-17
Also published as: IT1240160B; IT9067237A0; IT9067237A1

Abstract

A gear-changing device for a motor-vehicle transmission unit including a gearbox connected to the engine of the vehicle with the interposition of a clutch and having a plurality of members for engaging the gears associated with respective control actuators. An electronic control unit receives a signal indicative of the operation of the clutch and selects the gear to be engaged in dependence on the speed and acceleration of the vehicle detected at a moment close to that at which the clutch is operated.

Description

A device for operating a motor-vehicle gearbox

The present invention relates to a gear-changing device for a motor-vehicle transmission unit, including:

- a gearbox including a main shaft which is connected to the engine of the vehicle with the interposition of a clutch and a driven shaft connected to the driving wheels of the vehicle,

- a plurality of members for engaging the gears, associated with respective actuator means, and

- an electronic control unit which is arranged to detect operating parameters indicative of the conditions of movement of the vehicle in order to select the gear to be engaged in dependence on the operating parameters detected and to operate the actuator means in order to engage the selected gear.

A device of the type indicated above is known from European patent application No. 276 609. The known device described in EP 276 609 has an actuator which operates the clutch and acts under the control of a processing unit. In this known device, the processing unit operates the gearbox completely automatically; it selects the moment at which the gear is to be changed in dependence on the speed of rotation of the engine, operates the clutch, selects the gear to be engaged and operates the actuators which engage the selected gear.

The main disadvantage of the known device mentioned above lies in the fact that, like other automatic gear-changing devices, it makes the way in which the vehicle is driven completely impersonal. In fact, the selection of the moment to change gear and the speed with which the driver operates the clutch and accelerator pedals during gear-changing have a substantial effect on the style in which the vehicle is driven.

In order to solve this problem, the subject of the present invention is a gear-changing device of the type specified at the beginning, characterised in that the clutch is operated by a pedal which can be controlled by the driver, in that sensor means are provided for detecting the operation of the clutch, and in that the control unit is arranged to receive a signal indicative of the operation of the clutch from the sensor means and to select the gear to be engaged in dependence on the operating parameters detected at a moment close to the moment at which the clutch is operated.

As will become clear from the following description, the device according to the present invention performs automatically only those operations which do not affect the driving style of the driver, that is, only the selection and engagement of the gear. In fact, the selection of the gear to be engaged under certain conditions of speed and acceleration of the vehicle is a fixed choice so the disengagement of the previous gear and the engagement of the new gear is a purely mechanical operation which does not depend on the style of the driver. The device of the invention leaves the driver free, however, to select the moment at which the gear is changed and to operate the clutch and accelerator pedals directly according to his personal driving style.

Further characteristics and advantages of the present invention will become clear from the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which:

Figure 1 is a schematic view of an operating device according to the present• invention, and

Figure 2 is a schematic view of an actuator for operating a member for engaging the gears.

With reference to the drawings, a motor-vehicle gearbox, indicated 1, includes a main shaft 2 carrying a first set of gears 4 which are meshed permanently with corresponding gears 6 carried by a driven shaft 8. The main shaft 2 is connected to the engine 10 of the vehicle with the interposition of a conventional clutch 12 and the driven shaft 8 is connected to the driving wheels of the vehicle in known manner. In conventional manner, the driven shaft 8 has engagement members 14 associated with the gears 6 of the driven shaft 8 and movable between neutral positions and engagement positions in which they connect gears 6 for rotation with the driven shaft 8. In manual gearboxes, the engagement members 14 are made to slide by a control lever operated by the driver. In the gearbox shown in Figure 1, each engagement member 14 has an associated control actuator 16 for sliding it between its neutral position and its engagement position. The actuators 16 are connected to an electronic control unit 18 which operates them in the manner which will be explained below.

The clutch 12 is operated by a pedal 20, as is usual with manual gearboxes. A proximity sensor 22 is associated with the pedal 20 and sends the control unit

18 a signal indicative of the operation of the pedal 20 and hence of the driver's intention to change gear.

The driven shaft 8 of the gearbox 1 is associated with a speed sensor 24 which detects the speed of rotation of the driven shaft (which is proportional to the speed of the vehicle) . The speed sensor 24 sends the control unit 18 a signal indicative of the speed detected at regular intervals. The unit 18 compares the current speed V. with the speed V„ detected on the previous occasion. The value ,-V₂ is proportional to the mean acceleration of the vehicle during the interval between two successive detections.

When the pedal 20 for operating the clutch 12 is operated, the control unit 18 selects the gear to be engaged in dependence on the speed and acceleration values detected at a moment close to that at which the pedal 20 is operated.

The table given below shows the criteria according to which the control unit 18 selects the gear to be engaged.

V

The speeds which define the various ranges are expressed in km/h and naturally are intended to be purely indicative. Thus, if the value of V,-V-, at the moment when the pedal 20 is operated is, for example, -2 (deceleration) and the vehicle speed V- is 40 km/h, the control unit 18 selects third gear. If at the same speed (40 km/h) the value of V--V_? were -7

(braking) , the control unit would select second gear.

Since the driver may wish to change down, for example, in order to overtake quickly, without having effected a minimum deceleration, it is necessary to arrange for the release of the accelerator pedal or a light touch on the brake to be sufficient to change gear under the conditions in which V.-V\, ^ -5.

A pair of push-buttons, indicated 26 and 28, are also connected to the control unit 18 and can be operated by the driver to select reverse gear (this operation is enabled when V. < 5 km/h) and neutral.

Figure 2 shows a preferred embodiment of the control actuator 16 which slides the engagement member 14 under the control of the unit 18. As can be seen in Figure 2, each actuator 16 includes a pair of levers 30 articulated about parallel fixed axes32 perpendicular to the direction in which the engagement member 14 slides. The levers 30 are articulated to each other at 34 about an axis parallel to the articulation axes 32. Each lever 30 carries a thrust and coupling member 36 articulated to one end of the lever at 38. An electromagnet 40 is interposed between each thrust and coupling member 36 and the respective lever 30 and causes the member 36 to pivot between a raised position, shown in Figure 2, and a lowered position, not illustrated. When the pedal 20 is operated, the levers 30 are pivoted in the senses indicated by the arrows A by a system of levers (not shown) or by actuator means, likewise not shown. During the pivoting of the levers 30, the end portions 42 of the members 36 act against an appendage 44 of the engagement member 14. During this first stage of the operation, all the engagement members 14 are brought to their neutral positions. The control unit 18 then selects the gear to be engaged and operates the electromagnet 40 corresponding to the gear selected.

The electromagnet 40 selected is activated and urges the member 36 to its lowered position. The end 42 of the member 36 engages a recess 48 in the engagement member 14 so that the latter is drawn into its engagement position by the return of the levers 30 to their rest positions shown in Figure 2.

Naturally, the principle of the invention remaining the same, the details of construction and forms of embodiment may be varied widely with respect to those described and illustrated, without thereby departing from the scope of the present invention.

Claims

1. A gear-changing device for a motor-vehicle transmission unit, including:

- a gearbox (1) including a main shaft (2) which is connected to the engine (10) of the vehicle with the interposition of a clutch (12) and a driven shaft (8) connected to the driving wheels of the vehicle,

- a plurality of members (14) for engaging the gears, associated with respective actuator means (16) , and

- an electronic control unit (18) which is arranged to detect operating parameters indicative of the conditions of movement of the vehicle in order to select the gear to be engaged in dependence on the operating parameters detected and to operate the actuator means (16) in order to engage the selected gear,

characterised in that the clutch (12) is operated by a pedal (20) which can be controlled by the driver, in that sensor means (22) are provided for detecting the operation of the clutch (12) , and in that the control unit (18) is arranged to receive a signal indicative of the operation of the clutch (12) from the sensor means (22) and to select the gear to be engaged in dependence on the operating parameters detected at a moment close to the moment at which the clutch (12) is operated.

2. A device according to Claim 1, characterised in that the control unit (18) is arranged to receive a signal indicative of the speed of the vehicle at a moment close to that at which the pedal (20) for operating the clutch (12) is operated, to compare that speed with predetermined speeds defining a plurality of ranges each corresponding to a gear of the gearbox, and to select the gear which corresponds to the range including the previously-detected vehicle speed.

3. A device according to Claim 2, characterised in that the control unit (18) is arranged to detect the acceleration of the vehicle at a time close to that at which the pedal (20) for operating the clutch (12) is operated and, in dependence on the acceleration, to select a set of speeds defining the ranges.

4. A device according to Claim 1, characterised in that each member (14) for engaging the gears is made to slide between an engagement position and a neutral position by a lever (30) articulated about an axis (32) perpendicular to the direction in which the engagement member (14) slides and operatively associated with the pedal (20) for operating the clutch (12) .

5. A device according to Claim 4, characterised in that each member (14) for engaging the gears is associated with two levers (30) for causing the engagement member

(14) to slide in opposite directions.

6. A device according to Claim 5, characterised in that each lever (30) carries a thrust and coupling member

(36) movable between a first operating position - in which it urges the engagement member (14) from an engagement position to a neutral position as a result of the movement of the lever (30) - and a second operating position - in which it is coupled with the engagement member (14) and moves it from its neutral position to its engagement position as a result of the movement of the lever (30) , an actuator (40) being associated with each thrust and coupling member (36) for causing the thrust and coupling member (36) to move between its first and second operating positions.