WO1989000516A1

WO1989000516A1 - Transmission

Info

Publication number: WO1989000516A1
Application number: PCT/GB1988/000380
Authority: WO
Inventors: David Parsons; Alastair John Young; Roger Porter Jarvis; Harry Mellows Windsor
Original assignee: Automotive Products Plc
Priority date: 1987-07-17
Filing date: 1988-05-16
Publication date: 1989-01-26
Also published as: AU1705788A; GB8716974D0; GB9000647D0; GB2225822B; GB2225822A

Abstract

A motor vehicle has at least one ground running wheel driven by an internal combustion engine (10) via a transmission comprising a clutch (14) and a change-speed gearbox (12). Gearbox (12) has a plurality of mutually exclusively engageable gear ratios any desired one of which can be engaged by pivoting gear lever (16) manually, in direction (A) or (B) accordingly, about pivot (34) so that part of the gear lever (16) above the pivot (34) moves from one side of the gear shift pattern to the other side. Gear lever (16) comprises shaft (32) pivoted at (34) and a hand knob (42) on a tube (40) rockably pivoted at (44) on the shaft (32). When the tube (40) is rocked by manual force in direction (a) or (b) relatively to shaft (32) a signal is sent on line (64) or (66) to clutch control (18, 20) causing automatic dis-engagement of the clutch (14). Continued application of the manual force on the tube (40) causes the latter to push the shaft (32) which pivots in direction (A) or (B) to the opposite side of the gear shift pattern. On control (18, 20) receiving a signal on line (54) that a new gear ratio has been engaged, the control (18, 20) automatically re-engages the clutch (14). Springs (46) act to hold the tube (40) in a central or initial position relative to shaft (32) when no manual force is applied to knob (42). The clutch control (18, 20) includes an initiating device (68) which observes when the new gear ratio has been engaged and prevents a subsequent dis-engagement of the clutch (14) until the tube (40) has first been allowed to return to the initial position relative to the shaft (32).

Description

TRANSMISSION

This invention concerns a transmission for a motor vehicle.

The transmission is of the kind comprising a change speed gearbox in which its different gear ratios can be selected and de-selected as desired by the driver manually moving a gear lever, a clutch interposed between the engine of the vehicle and the gearbox, and a control causing automatic disengagement of the clutch when deselection of the currently selected gear ratio is initiated by the driver and automatic re-engagement of the clutch when a said gear ratio is selected. In such a transmission there is no need for the driver to act separately to operate the clutch for gear ratio changes, thus the vehicle does not need a driver operated pedal to work the clutch, but only requires accelerator and brake pedals.

According to the invention there is provided a transmission for a motor vehicle wherein the transmission is intended for transmitting rotary motion between an engine of the vehicle and at least one ground running wheel of said vehicle, said transmission comprising a change speed gearbox comprising at least first and second rotatable shafts, said second shaft being for transmitting rotary motion between said gearbox and a said ground running wheel, a plurality of rotatable gear ratios each being de-selectable and each being mutually exclusively selectable for transmitting rotary motion between said shafts through each selected one of said gear ratios, and gear ratio selection means including a gear lever which is manually movable to cause de-selection of any previously selected gear ratio and to cause selection of any desired said gear ratio, and clutch means connected with the first shaft and intended for interposing between said engine and said first shaft, the clutch means being engageable to transmit rotary motion between the said engine and first shaft and disengageable to interrupt that transmission, characterised by clutch control means to automatically engage and disengage said clutch means, said clutch control means comprising first observing means to observe when any said gear ratio is selected, said gear lever having a first part and a second part mounted on the first part and being movable with said first part in response to manual force applied to the second part for transmission to said first part, the gear lever being arranged such that the second part automatically adopts a pre-determined initial position relative to said first part when no manual force is applied to said second part, said second part being movable to a limited extent relative to the first part from said initial position when a manual force is applied to the second part, second observing means to observe movement of the second part relative to the first part from and into said initial position, said clutch control means being arranged such that when a said gear ratio is in a selected state and the second part of the gear lever is moved relative to the first part from said initial position, the second observing means provides a signal to which the clutch control means is responsive to cause disengagement of said clutch means, and subsequent to a de-selection of any said gear ratio, the next selection of a said gear ratio is observed by said first observing means which provides a signal to which the clutch control means is responsive to cause engagement of said clutch means, and said clutch control means being also arranged such that the clutch control means is inhibited from causing clutch disengagement subsequent to a said gear ratio selection until the clutch control means responds to a signal provided by the second observing meanβ when the latter observes movement of the second part of the gear lever relative to first part into said initial position whereafter movement of the second part of the gear lever relative to the first part from said initial position can initiate disengagement of said clutch means.

The transmission formed in accordance with the invention has a number of advantages. One is that once a driver has moved the gear lever (by pushing or pulling on the second part of the lever) to select a desired gear ratio and the clutch means is automatically re-engaged, the clutch means cannot automatically be disengaged should the driver's hand linger on the second part of the gear lever and thereby hold the second part out of the initial position. Further advantages of the transmission will be understood from the following description of the invention, given by way of example, with reference to the accompanying drawings in which:-

Fig.1 diagrammatically illustrates a transmission formed according to the invention, in combination with an engine for the vehicle;

Fig.2 illustrates a gear shift pattern to be followed by the gear lever in Fig.1 for selecting and de-selecting the different gear ratios in the gearbox in Fig.1;

Fig.3 illustrates a logic circuit included in an electronic control part of the clutch control means of the tranmission in Fig.1, and

Fig.4 illustrates a modification which can be applied to the circuit in Fig. 3.

With reference to Fig.1 the transmission is intended to be used in conjunction with an internal combustion engine 10 for a motor vehicle. The transmission comprises a change speed gearbox 12, a friction clutch within a bell-housing 14, a manually moveable gear lever 16 for selecting and de-selecting different gear ratios in the gearbox 12, and a clutch control for automatically engaging and disengaging the clutch; that clutch control including an electronic control 18 and a fluid flow control 20.

The gearbox 12 has a rotatable output shaft 22 to drive through any suitable known means one or more ground running wheels of the vehicle. The gearbox 12 also has a rotatable input shaft 21 (not shown). The friction clutch in the bell-housing 14 can be of any type known per se suitable when the clutch is engaged for transmitting rotary drive between the engine 10 and the gearbox input shaft, and the clutch being capable of being disengaged to interrupt that transmission. The clutch can be controllably and progressively disengaged and re-engaged using a release fork or lever 24 pivoted at 26 and interacting in known manner with the clutch. A fluid pressure piston and cylinder unit or actuator 28 acts on the pivoting lever 24 so that the rate and degree of engagement or disengagement of the clutch at any instant is controlled by the amount of fluid in the actuator 28. The amount of the fluid, which may be hydraulic fluid, acting in the actuator 28 is controlled by a fluid pressure supply and control system 30 which forms the fluid flow control 20 with the actuator.

Gearbox 12 is of any suitable kind. In this example it comprises six de-selectable and mutually exclusively selectable rotable gear ratios (hereinafter called gears for convenience) to transmit rotary motion between the shafts 21 and 22 and providing first, second, third, fourth, fifth and reverse gears represented in Fig.2 by the symbols 1, 2, 3 , 4, 5 and R respectively. The gear lever 16 includes a shaft 32 having a ball formation 34 for a pivot mounting of a type known per se permitting a degree of universal movement to the gear lever. The lower end of shaft 32 is connected by any means 36 known per se for conveying movement of the gear lever 16 to a selection crank arm 38 causing selection and de-selection of any desired gear when the portion of the gear lever 16 above the ball 34 is moved in accordance with the gear shift pattern in Fig.2. Besides shaft 32, gear lever 16 also comprises a tube 40 (shown in section) surmounted by a knob 42. Tube 40 is mounted by a pivot 44 on the shaft 32. The knob 42 is intended for the application of manual force directly thereto by the hand of the driver for changing gear. When no manual force is applied to the knob 42 the tube 40 adopts a centralised or initial position (shown in Fig. ) with respect to the shaft 32 under the action of resilient means 46 acting, between the shaft and the tube 40, along an axis transverse to both the axis of pivot 40 and the axis of the shaft 32. Due to the pivot point 44 the knob 42 can only pivot respectively to the shaft 32 in each of two directly opposite directions _ and b_ about the axis of pivot 4 when manual force, having a component along direction a. or b_, is applied to the knob. From the initial position the knob 42 can only pivot in direction a or b_ relatively to the shaft 32 to a limited extent, after which the tilted tube 40 acts on an upper part 33 (that part above the ball 34) of the shaft 32. Thus if the component of manual force continues to be applied and if the upper shaft part 33 is free to pivot about the ball pivot 34, in direction a or b_, the upper shaft part then pivots about the ball pivot in direction A or B which is essentially the same direction as a or b respectively.

In the gear shift pattern in Fig.2 line N lies between extreme positions 48 and 50 at opposite sides of the gear shift pattern. It is to either extreme position 48 or 50 that upper shaft part 33 must be moved along direction A or B (possibly combined with a movement in direction X or Y) when it is desired to select any gear in the division or group of gears consisting of first, third and fifth gear or in the division or group of gears consisting of the second, fourth and reverse gear. Therefore the knob 42 can only pivot, about axis 44, in a plane which is substantially 90°to extreme positions 48 and 50.

The gearbox 12 is provided with gear condition observing means 52 providing electrical signal outputs on line 54', 54A, 54 and line 56', 56A, 56 serving as inputs to the electronic control 1b. Observing means 52 is arranged to observe when any gear is selected and give an output on line 54 signifying that a gear i3 in the selected state. The observing means 52 is also arranged to observe when none of the gears is in a selected state and gives an output which represents that no gear is selected. Furthermore the observing means 52 is arranged to observe when the gearbox 12 is in a reference neutral state corresponding to the position of the upper shaft part 33 substantially coinciding with any point along the neutral line N in the gear shift pattern (Fig.2). When that happens the observing means 52 gives an output signal on line 56 signifying that the position of the upper shaft part 33 is coinciding with some point on line N whether the upper shaft part dwells on the line N or is merely crossing it quickly (i.e. whether the gearbox 12 is dwelling in the reference neutral state or has been moved quickly through that reference state). When the gearbox is not in the aforesaid reference neutral state (i.e., the upper shaft part 33 is not in coincidence with any point on line N) the observing means 52 provides a signal on line 56 to signify that condition of the gearbox. Elements 54A and 56A can be inverters, and in order to operate the electronic control 18 in the desired manner the observing means 52 is arranged to provide a signal which appears on line 54 at logic level "1" when any gear is in the selected state and at logic "0" when no gear is in a selected state and is arranged to provide a signal which appears on line 56 at logic "1" when the gearbox 12 is in the reference neutral state and at logic "0" when the gearbox is not.

In the gear lever 16 another observing means is provided which comprises a pair of spaced magnetic sensors 58 and 60 firmly attached to the upper part 33 of the shaft 32 and a permanent magnet 62 firmly attached to the knob 42. When the tube 40 and knob 42 are in the centralised or initial position relative to the shaft 32, the magnet 62 is mid-way between both the sensors 58 and 60 which are thus not influenced by the magnet and provide signals on lines 64 and 66 signifying that the tube 40 and knob 42 are not tilted in direction a or b_ relative to the shaft 32. When the tube 40 and knob 42 are tilted relative to shaft 32 in direction a or direction b_ the magnet 62 comes closer to either sensor 58 or 60 causing the appearance of a signal on line 64 or line 66 to signify that tilt. In order to operate the electronic control in the desired manner the sensor system is arranged so that a signal at logic level "0" appearing on line 64 indicates no tilt of knob 42 in direction a but one at logic "1" does indicate a tilt in direction _. Whilst a signal at logic "0" appearing on line 66 indicates no tilt of knob 42 in direction b_, but one at logic "1" does indicate a tilt in that direction. In the electronic control 18 there are an initiating circuit 68 and an actuating circuit 70 which sends signals on line 72 to actuate the fluid flow control 20. With particular reference to Fig.3 the initiating circuit 68 comprises AND gates 74, 76 and 78, NOT gates or inverters 80 and 82, OR gate 84, and NOR gates 86, 88, 90 and 92. In the initiating circuit 68, the sub-circuit 69 formed by gates 76, 80 and 84 is a latch.

When the output on line 94 from circuit 68 is at logic "0" the actuating circuit 70 operates to provide a signal on line 72 causing the fluid flow control 20 to disengage the clutch and hold the latter dis-engaged for as long as the signal on output line 94 remains at logic "0". On the other hand when the output signal on line 94 is at logic "1", the circuit 70 operates to provide a signal on line 72 causing the control 20 to engage the clutch and keep it engaged whilst line 94 remains at logic "1".

If, for example, we consider the situation where the first, third or fifth gear is selected, then the signal on line 54 is at logic "1" and the signal on line 56 is at logic "0"; furthermore the upper part 33 of the shaft 32 will be at some place, on extreme position 48, corresponding to the selected gear, and provided no manual force is applied to the knob 42 it will be in its initial or centralised position and thus the signals on lines 64 and 66 will each be at logic "1".. In this situation the output on line 94 is at logic "1", thus the clutch is engaged. Now when it is desired to change up or down a gear, that is to select second or fourth gear as appropriate in this example, the upper shaft part 33 will have to be moved from the extreme position 48 to extreme position 50, namely the shaft part 33 will have to move in direction B. To do that the driver would normally pull on the knob 42 causing it first to pivot in direction b_. Thus the signal on line 66 changes to logic "0" whilst that on line 64 remains at logic "1". Lines 54 and 56 are still at logic "1" and logic "0" respectively. Therefore the output on line 94 changes to logic "0" causing clutch dis-engagement. After the knob 42 has pivoted, continued pulling on it in direction B causes the upper shaft part 33 to pivot out of extreme position 48 causing de-selection of the selected gear so that the signal on line 54 goes to logic "0". Now (ignoring what happens when the gearbox is in the reference neutral position which will be explained below) irrespective of whether the knob 42 is in a state pivoted out of its centralised or initial position relative to upper shaft part 33 or is in the centralised or initial position, the logic value on line 94 will not change to logic "1" until the continued pulling of the upper shaft part 33 in direction B to extreme position 50 results in the selection of the desired new gear. At which point the signal on line 54 goes to logic "1" again, and line 94 goes to logic "1" causing re-engagement of the clutch .

Line 94 goes to logic "1" because the output from NOT gate 80 is at logic "1". When the gearbox is in a gear selected state and the clutch is engaged, the clutch cannot be disengaged until the output from NOT gate 80 is at logic "0". With the signals on lines 54 and 56 being at logic "1" and logic "0" respectively, the output from NOT gate 80 can only be changed from logic "1" to logic "0" by an output at logic "1" from AND gate 74 which only occurs when the two inputs to the AND gate 74 are each at logic "1". This only happens when the knob 42 and tube 40 are in the centralised or initial position. Thus when a gear change has been made so that a new gear has been selected and the clutch re-engaged because line 94 is at logic "1", then at the time the gear is selected, or thereafter, the knob 42 and tube 40 must be allowed to resume the initial or centralised position. Otherwise no pivoting of the knob 42 and tube 40 in either direction a or b from the initial or centralised position can cause the signal on line 94 to change from logic "1" to logic "0" to cause ^'clutch disengagement. Therefore should the driver continue holding the knob 42 and tube 40 pivoted in either direction a or b out of the initial or centralised position after the new gear has been selected, there can be no automatic disengagement of the clutch until the knob 42 and tube 40 have first been allowed to resume the initial or centralised position.

At the instant that a new gear is selected the knob 42 and the tube 40 are not likely to be in the centralised or initial position with respect to the upper shaft part 33 but are pivoted about the axis 44 in the direction that the upper shaft part 33 is being moved. This is due, for example, to frictional resistance in the gearbox (via the connecting means 36) tending to oppose the movement of the upper shaft part.

It will be readily understood that once a gear has been selected and the knob 42 and tube 40 have been allowed to adopt the centralised or initial position, that pivoting of the knob and tube in either direction a or b_ about the axis 44 will cause automatic clutch disengagement.

It will also be understood that when the gearbox 12 is in the reference neutral state (other than for a momentary period of time which is discussed below) corresponding with the upper shaft part 33 being on line N that the signal at logic "I" on line 56 results in the signal on line 94 being at logic "1", and thus the clutch to engage for as long as the gearbox is in the reference neutral state. Pushing or pulling the upper shaft part 33 in direction A or B from line N by manual force applied to the knob 42 results in the signal on line 56 going to logic "0" and thus the signal on line 94 goes to logic "0" too and the clutch disengages to allow selection of a forward gear or the reverse gear R. If the latter is the case, the clutch is automatically engaged when the signal on line 54 goes to logic "1" when reverse gear is selected and changes the signal on line 94 to logic "1".

There may be a risk, as the upper shaft part 33 moves between one extreme position 48 or 50 and the other, that an aberration may occur in which the knob 42 _tid the tube 40, for some part of that movement, prematurely resume the initial or centralised position with respect to the upper shaft part under the effect of the resilient means 46, if resistance to the movement of the upper shaft part is only slight. This would mean that the signal at logic "0" on line 64 or 66 would revert to logic "1" for the period of the aberation. That is undesirable because if the signal on line 64 or 66 is at logic "1" whilst the gearbox is momentarilly in the reference neutral state, during the course of a gear change, the signal on line 94 will go momentarily to logic "1" causing momentary re-engagement of the clutch until the signal on line 56 goes to logic "0" again causing the signal on line 94 to revert to logic "0".

To prevent such momentary re-engagement of the clutch it is preferred to modify the circuit in Fig.3 as shown in Fig. , by providing time delays 96 and 98 in the input lines 64 and 66. Each time delay consists of a diode, a resistance, and an earthed capacitance. As long as the signal input to either time delay is at logic "0" the signal is immediately applied to the AND gate 74, but when the input signal to either time delay 96 or 98 changes from logic "0" to logic "1" the output from the time delay continues at logic "0" for a pre-determined period of time before changing to logic "I". The aforesaid pre-determined period of time may be, for example, about 0.1 seconds, sufficient during normal gear changing for the upper shaft part 33 to be moved from one extreme position 48 or 50 to the other in the gear shift pattern. Should the knob 42 and tube 40 have been pivoted back to the initial or centralised .position then whilst the gearbox is momentarily in the reference neutral state, the output at logic "0" from the AND gate 74 (due to one or other of the time delays) ensures^' that the output from AND gate 78 remains at logic "0". Therefore, the output from NOR gate 92 continues at logic "1" to ensure the output on line 94 continues at logic "0" which ensures the clutch remains disengaged during the time the gearbox is momentarily in the reference neutral state.

When the vehicle is being driven with the engine 10 delivering low driving torque, there is a risk that a very slight force on the gear lever 16 can cause the gearbox 12 to slip out of gear but not into the reference neutral state. Therefore, the signals on lines 54 and 56 would now both be at logic "0". The slight force mentioned above could be so slight as to be unable to overcome the force exerted by the resilient means 46 and thus the tube 40 and knob 42 would not be tilted from the initial or centralised position. Therefore, the signals on lines 64 and 66 would each continue at logic "l". This combined with the signals at logic "0" on both lines 54 and 56 cause the signal on line 94 to go to logic "0", causing automatic disengagement of the clutch. If desired NOR gate 88 can be omitted including its connection to the NOR gate 90 which need only be a two input gate. When gate 88 is omitted, its two input connections to line 54 and latch 69 respectively are also omitted. If desired the function of the initiating circuit 68 can be replaced by a microprocessor or other computer means suitably programmed and responsive to digitised signals corresponding to those on lines 54, 56, 64 and 66 so that the clutch engagements and disengagements occur as described above.

Claims

1. A transmission for a motor vehicle wherein the transmission is intended for transmitting rotary motion between an engine (10) of the vehicle and at least one ground running wheel of said vehicle, said transmission comprising a change speed gearbox (12) comprising at least first and second rotatable shafts (21, 22), said second shaft (22) being for transmitting rotary motion between said gearbox (12) and a said ground running wheel, a plurality of rotatable gear ratios each being de-selectable and each being mutually exclusively selectable for transmitting rotary motion between said shafts (21, 22) through each selected one of said gear ratios, and gear ratio selection means including a gear lever (16) which is manually movable to cause de-selection of any previously selected gear ratio and to cause selection of any desired said gear ratio and, clutch means (14) connected with the first shaft (21) and intended for interposing between said engine (10) and said first shaft (21), the clutch means v*4) being engageable to transmit rotary motion between the said engine (10) and first shaft (21) and disengageable to interrupt that transmission, characterised by clutch control means (18, 20) to automatically engage and disengage said clutch means (14), said clutch control means (18, 20) comprising first observing means (52) to observe when any said gear ratio is selected, said gear lever (16) having a first part (33) and a second part (40) mounted on the first part (33) and being movable with said first part (33) in response to manual ^"force applied to the second part (40) for transmission to said first part (33), the gear lever (16) being arranged such that the second part (40) automatically adopts a pre-determined in-itial position relative to said first part (33) when no manual force is applied to said second part (40), said second part (40) being movable (a, b) to a limited extent relative to the first part (33) from said initial position when a manual force is applied to the second part (40)^ second observing means (58, 60, 62) to observe movement of the second part (40) relative to the first part (33) from and into said initial position, said clutch control means (18, 20) being arranged such that when a said gear ratio is in a selected state and the second part (40) of the gear lever (16) is moved (a, b) relative to the first part (33) from said initial position the second observing means (58, 60, 62) provides a signal to which the clutch control means (18, 20) is responsive to cause disengagement of said clutch means (14), and subsequent to a de-selection of any said gear ratio the next selection of a said gear ratio is observed by said first observing means (52) which provides a signal to which the clutch control means (18, 20) is responsive to cause engagement of said clutch means (14), and said clutch control means (18, 20) being also arranged such that the clutch control means (18, 20) is inhibited from causing clutch disengagement subsequent to a said gear ratio selection until the clutch control means (18, 20) responds to a signal provided by the second observing means (58, 60, 62) when the latter observes movement (a, b) of the second part (40) of the gear lever (16) relative the first part (33) into said initial position whereafter movement (a, b) of the second part (40) of the gear lever (16) relative to the first part (33) from said initial position can- initiate disengagement of said clutch means (14).

2. A transmission as claimed in Claim 1, characterised in that the second part (40) of the gear lever (16) is movable substantially only in first and second opposite directions (a, b) with respect to the first part (33) .

3. A transmission as claimed in Claim 2, characterised in that the first part (33) of the gear lever (16) is movable (A, B) from one extreme position (48) to another extreme position (50) to cause de-selection of a said gear ratio and the selection of another said ratio, and said first direction (a) is towards one of the extreme positions (48) and the second direction (b) is towards the other extreme position (50).

4. A transmission as claimed in Claim 1 , characterised in that the first part (33) of the gear lever (16) is movable from an extreme position (48, 50) to cause de-selection of a said gear ratio and the selection of another said ratio, said first observing means (52) is arranged to observe when the first part

(33) of the gear lever (16) moves into and moves out of a reference neutral position (N) which lies between the two said extreme positions (48, 50), and said control means (18, 20) is arranged to cause automatic engagement of the clutch means (14) when said first part (33) of the gear lever (16) is in said reference neutral position (N) for longer than a pre-determined period of time, and to cause automatic disengagement of the clutch means (14) when the first part (33) of the gear lever (16) is moved out of said reference neutral position (N) and no gear is in a selected state.

5. A transmission as claimed in Claim 4, characterised in that the control means (18, 20) is arranged to ignore the presence of the first part (33) of the gear lever (16) in the reference neutral state and maintain said clutch means (14) disengaged provided the duration of said presence is less than said predetermined period of time.

6. A transmission as claimed in Claim 1, characterised in that said clutch control means (18, 20) is so arranged that when the first observing means (52) observes a de-selection of a selected gear ratio but the second observing means (58, 60, 62) does not observe movement of the second part (40) of the gear lever (16) relative to said first part (33) from the initial or centralised position^' the clutch control means (18, 20) initiates a disengagement of the clutch means(llf).

7. A transmission as claimed in any one preceding claim, characterised in that said control means (18, 20) comprises computer means programmed for the control means (18, 20) and clutch means (14) to operate in the manner set forth in that claim in reponse to signals initiated by the first (52) and second (58, 60, 62) observing means.

8. A transmission for a motor vehicle wherein the transmission is intended for transmitting rotory motion between an engine of the vehicle and at least one ground running wheel, said transmission being arranged and controlled substantially as hereinbefore described with reference to Figs.1 to.3 or Figs. 1 to 4 of the accompanying drawings.