GB2492066A

GB2492066A - A free rolling control method and system of a motor vehicle

Info

Publication number: GB2492066A
Application number: GB1110205.0A
Authority: GB
Inventors: Ian Halleron; Peter George Brittle; Martin Robekowski; Themi Philemon Petridis
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2011-06-16
Filing date: 2011-06-16
Publication date: 2012-12-26
Anticipated expiration: 2031-06-16
Also published as: CN102826082B; RU2012125158A; RU2602164C2; GB2492066B; DE102012209067A1; CN102826082A; GB201110205D0

Abstract

A method and system for controlling a motor vehicle (1, fig 1A) during an exit from a free rolling phase of operation, comprises adjusting an engine (2) speed to match an input speed of a transmission (3) so as to provide a smooth exit from the free rolling phase of operation to a normal phase of operation. The input speed of the transmission (3) is calculated based upon a composite final drive ratio, the gear ratio of the transmission (3) chosen for the exit and a speed at which the motor vehicle 1 is travelling. A predictive gear sensing system determines a next gear to be engaged and this ratio is used in calculating the input speed of the transmission (3). During the free rolling phase a clutch (10) is disengaged and the transmission (3) is in gear.

Description

A Method and System for Controlling a Motor Vehicle This invention relates to the control of a motor vehicle having an engine driving a transmission via a clutch and in particular to the control of such a motor vehicle during an exit from a free rolling phase of operation.

It is known for a motor vehicle having an engine driving a transmission via a clutch to use free rolling' to improve fuel economy. During a free rolling phase of operation, the engine is temporarily turned off and disconnected from the driven wheels while the motor vehicle is moving. Disconnecting the driveline removes engine friction and pumping losses from the forces decelerating the motor vehicle, thereby allowing it to coast further.

There are two ways in which the free rolling phase may be entered from the normal driven phase of operation.

Firstly, the driver may select neutral in the transmission and secondly, the clutch may be disengaged while a driving gear is still selected.

A difficulty with the use of free-rolling occurs when the free rolling phase has to be exited requiring the engine to be re-started and the driveline to be re-engaged.

If the free rolling' occurs with neutral selected in the transmission (FRIN), to exit free rolling', a driver presses the clutch pedal, selects a gear and then releases the clutch pedal to engage the clutch.

If the free rolling' occurs with the transmission in a driven gear but with an e-clutch disengaged (FRIG), to exit free rolling' the driver either presses the accelerator pedal to request a torque supply from the engine or presses the clutch and then selects a new gear and then releases the clutch pedal.

In all of these cases there is often a mismatch in speed between the engine and an input to the transmission when the clutch is engaged during the exit from this free rolling phase of operation. Any such mismatch of speed will result in a torque disturbance felt by the driver as a bump or jerk which is undesirable and will have a negative effect on driver satisfaction. In addition, if the mismatch is large then unnecessary clutch wear and additional fatigue of driveline components may occur.

It is an object of the invention to provide a method and system for controlling a motor vehicle during an exit from a free rolling phase of operation that facilitates a smooth exit from the free rolling phase of operation.

According to a first aspect of the invention there is provided a method for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation wherein the method comprises determining whether one or more conditions for exiting the free rolling phase of operation are present and, if the one or more conditions are present, starting the engine and adjusting the speed of the engine to a required engine speed based upon an input speed of the transmission.

The method may further comprise determining the input speed of the transmission and adjusting the engine speed to match the input speed of the transmission.

Determining the input speed of the transmission may comprise measuring the input speed of the transmission.

Determining the input speed of the transmission may comprise calculating the input speed based upon a current speed of the motor vehicle.

Calculating the input speed of the transmission may comprise using a gear ratio of the transmission selected for the exit in combination with current vehicle speed and a composite final drive ratio to calculate the input speed of the transmission.

The method may further comprise using a selected gear sensing system to determine the gear ratio selected for the exit and using the determined gear ratio in the calculation of the input speed of the transmission.

The method may further comprise using a predictive gear sensing system to predict the next to be engaged gear and using the gear ratio of the predicted next to be engaged gear in the calculation of the input speed of the transmission.

The method may further comprise using the predictive gear sensing system to determine the actual gear ratio selected for exit and using the actual gear ratio in the calculation of the input speed of the transmission.

During the free rolling phase of operation the clutch may be engaged and the transmission may be in neutral and the one or more conditions for exiting the free rolling phase of operation may comprise engagement of a forward gear of the transmission.

During the free rolling phase of operation the clutch may be disengaged and the transmission may be in gear and the one or more conditions for exiting the free rolling phase of operation comprise a request for the supply of torque from the engine.

According to a second aspect of the invention there is provided a system for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation wherein the system comprises a controller operable to determine whether one or more conditions for exiting the free rolling phase of operation are present and, if the one or more conditions are present, start the engine and adjust the speed of the engine to a required engine speed based upon an input speed of the transmission.

The system may further comprise a sensor to measure the input speed of the transmission and the required engine speed is an engine speed that matches the input speed of the transmission.

The controller may be operable to use a gear ratio of the transmission selected for the exit in combination with current vehicle speed and a composite final drive ratio to calculate the input speed of the transmission and the required engine speed may be an engine speed to match the calculated input speed of the transmission.

The transmission may be a manual transmission and the system may further comprise a selected gear sensing system for determining the gear ratio selected for the exit.

The transmission may be a manual transmission and the system may further comprise a predictive gear sensing system for predicting the next to be engaged gear and the controller may be operable to use the gear ratio of the predicted next to be engaged gear in the calculation of the input speed of the transmission.

In which case, the predictive gear sensing system may be further used to determine the actual gear ratio selected for exit and the actual gear ratio selected may be used by the controller in the calculation of the input speed of the transmission.

During the free rolling phase of operation the transmission may be in neutral and determining whether the one or more conditions for exiting the free rolling phase of operation may include the sensing of engagement of a forward gear of the transmission.

During the free rolling phase of operation the clutch may be disengaged and the transmission may be in gear and determining whether the one or more conditions for exiting the free rolling phase of operation may comprise sensing a reguest for the supply of torque from the engine.

According to a third aspect of the invention there is provided a motor vehicle having a a system for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation constructed in accordance with said second aspect of the invention.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1A is a diagrammatic representation of a motor vehicle according to one aspect of the invention; Fig.1B is a diagrammatic representation of part of the driveline of the motor vehicle shown in Fig.1A; Fig.2A is a diagrammatic view of part of a transmission of the motor vehicle shown in Fig.l showing the location of a 2D selected gear sensor and a 2D magnetic target; Fig.2B is a pictorial view showing the motion of a transmission turret shift selector cylinder, the axial (X axis) and rotational (Y axis) positions of which are sensed by the 2D selected gear sensor; Fig.3A is a first pictorial view of a turret selector cylinder follower; Fig.3B is a second pictorial view of the turret selector cylinder follower shown in Fig.3A; Fig.4 is a pictorial view of a transmission turret shift mechanism showing in more detail the turret selector cylinder shown in Fig.21B; Fig.5 is a more detailed view of the part of the transmission shown in Fig.2A showing the location of the 20 target and the 2D magnetic sensor array; Fig.6A is an enlarged cross-section through part of the turret selector cylinder follower shown in Figs.3A and 3B showing the turret selector follower in a Neutral gear position; Fig.6B is an enlarged cross-section through part of the turret selector cylinder follower shown in Figs.3A and 3B showing the turret selector follower in an Even gear pull-in position; Fig.6C is an enlarged cross-section through part of the turret selector cylinder follower shown in Figs.3A and 3B showing the turret selector follower in an Odd gear pull-in position; Fig.7A is diagram showing the relationship between transmission turret selector oylinder rotational and axial positions and the respeotive signal outputs from the 2D seleoted gear sensor; Fig.7B is an enlarged view of the relationship between transmission turret seleotor cylinder rotational position and signal output showing two in-plane or rotational check points according to one embodiment of a predictive gear sensing system according to the invention; Fig.8A is a schematic drawing of an H-gate selector mechanism showing a number of in-plane and between plane check points according to a second embodiment of a predictive gear sensing system according to the invention; Fig.8B is chart showing the relationship between transmission turret selector cylinder axial position and signal output showing the between plane check points indicated on Fig.8A; Fig.8C is chart showing the relationship between transmission turret selector cylinder rotational position and signal output showing the in-plane check points indicated on Fig.8A; Fig.8D is an underside view of an H-gate shift lever guide showing the location of a number of shift lever sensors forming part of a third embodiment of a predictive gear sensing system; Fig.9 is a chart showing the relationship between vehicle speed and engine speed for various transmission ratios; Fig.1O is simplified flow chart of a first embodiment of a method for predicting gear engagement; Fig.ll is simplified flow chart of a second embodiment of a method for predicting gear engagement; and Fig.l2 is a simplified flow chart of a method for controlling a motor vehicle during an exit from a free rolling phase of operation.

Referring firstly to Figs 1 to 6C there is shown a motor vehicle 1 having an engine 2 drivingly connected to a manual gearbox/ transmission 3 via a clutch 10. The transmission 3 includes a gear shift lever 11 by which the driver may select using an H-gate selector mechanism the various gears of the transmission 3.

An electronic processing unit in the form of a Powertrain Control Module (SCM) 4 is provided to control the powertrain of the motor vehicle 1. The PCM 4 includes an engine control unit 6 to control the operation of the engine 2 and a transmission state module 5 to determine the operating state of the transmission 3.

The PCM 4 is arranged to receive a number of inputs or signals from sensors 9 including one or more of engine speed from an engine speed sensor 9e, vehicle speed from a vehicle speed sensor 9v associated with a wheel W', clutch pedal position from a clutch pedal sensor 9c, throttle position from an accelerator pedal position sensor 9a, brake pedal position from a brake pedal sensor 9b and may also receive information regarding other components on the motor vehicle 1.

Some or all of the inputs from the sensors 9 may be used by engine control unit 6 to control the operation of the engine 2 and in particular the speed of the engine 2.

It will be appreciated that the engine control unit 6 and the transmission state module 5 could be separate processing units or be formed as part of a single electronic processor such as the PCM 4 as shown.

Referring to Fig.1IB the engine has an output 2a which drives the clutch 10 and which rotates at the same speed as a crankshaft of the engine 2. In practice the output 2a is formed by a flywheel of the engine 2. The clutch 10 is used to releasably couple the output 2a to an input 3i of the transmission 3 which in most cases is formed by an input shaft of the transmission 3.

It will be appreciated that when the clutch 10 is engaged with no slip the speed of the engine output 2a is the same as the speed of the transmission input 3i. When the clutch 10 is disengaged there is no direct relationship between engine output speed and transmission input speed but the transmission input speed is related to the speed of the vehicle and the gear ratio of the transmission 3 plus the composite final drive ratio' of the motor vehicle 1.

The term composite final drive ratio' as meant herein is the combination of the rolling ratio of the wheel W' with the actual final drive ratio of the driveline from which the input speed of the transmission 3 can be determined using the equation below:-V x {RT X Rd Where: -T1 is the rotational speed of the input 3i to the transmission 3 in revolutions per minute; V is the velocity of the motor vehicle 1 in metres per minute; RT is the selected gear ratio; and R is the composite final drive ratio.

-10 -For example, if the motor vehicle is moving at 20kph then for one transmission 3 arrangement the input speed of the transmission would be:-First Gear (lg) = 2000RPM (lokph/1000 RPM) Second gear (2g) = 1333RPM (l5kph/1000RPM) Third gear (3g) = 1000RPM (2okph/1000RPM) Fourth gear (4g) = 800RPM (25kph/1000RPM) Fifth gear (5g) = 667RPM (3okph/1000RPM) Sixth gear (6g) = 400RPM (Sokph/1000RPM) Where: -R1 First Gear = 4:1 R1 Second Gear = 2.67:1 R1 Third Gear = 2.0:1 R1 Fourth Gear = 1.6:1 R1 Fifth Gear = 1.33:1 R1 Sixth Gear = 0.8:1 And Rc = 1.5:1 It will be appreciated that the term manual transmission' as meant herein is a transmission in which the various gear ratios are manually selected by a driver of the motor vehicle 1 by the movement of the shift lever 11.

It will be further appreciated that engagement and disengagement of the clutch 10 is manually controlled by the driver of the motor vehicle 1 or electronically controlled in response to driver actions as in the case of an e-clutch.

An e-clutch is an electronically controlled clutch in which clutch pedal position is monitored using a sensor and the actual clutch engagement/disengagement is performed via an electronically controlled actuator.

-11 -The motor vehicle 1 includes a first embodiment of a predictive gear sensing system comprised of the transmission state module 5, a 2D magnetic target 8 and a 2D selected gear sensor 7 forming in combination a 2D selected gear sensor pair. The transmission state module 5 is arranged to receive signals from the selected gear sensor 7 attached to a casing 3B of the transmission 3. The selected gear sensor 7 is a 2D magnetic PWM sensor array that provides signals based upon variations in flux between the selected gear sensor 7 and the 2D magnetic target 8 associated with a shift selector member in the form of a turret selector cylinder 3A. The selected gear sensor 7 combines a rotary position sensor and an axial displacement sensor in a single 2D sensor array.

Figs.2A, 4 and 5 shows a typical H-gate' transmission configuration consisting of a shifter turret selector cylinder 3A located inside the main transmission casing 31B.

The shifter turret selector cylinder 3A rotates when the gear lever 11 is moved forwards and backwards to select respectively odd and even gears and it moves axially when the gear lever 11 is moved left and right to change the gear shift lever plane in which the gear lever moves. Reverse gear can be configured as an odd gear or an even gear depending upon the configuration of the transmission 3. It will be appreciated that the shifter turret selector cylinder could be arranged such that forward and backward movement results in axial movement of the selector cylinder and left right movement results in rotation of the selector cylinder and the output from the 2D sensor array would be interpreted accordingly.

The gear shift lever 11 is connected by a cable drive to a pair of levers 2lA, 2lB formed as part of the shifter turret assembly 20 which actuate the shifter turret selector cylinder 3A.

-12 -The 2D magnetic target 8 is attached to the shifter turret selector cylinder 3A and, in the example shown, the selected gear sensor 7 is located on the outside of the transmission housing 3B and detects axial and rotational movement of the magnetic target 8. However, it will be appreciated that the selected gear sensor 7 could be mounted inside the transmission casing 3B.

Figure 21B shows the movement of the magnetic target 8 when different gears are selected.

Figs.3A, 3B, 6A, 61B and 6C show a follower 3C which is attached to and rotates with the selector cylinder 3A, the follower 3C has three detents 3E, a central detent corresponding to a neutral gear position, an odd gear detent to one side of the neutral detent and an even gear detent to the other side of the neutral detent. A ball 3D is biased by a spring (indicated diagrammatically by the arrow 5' on Figs. 6a, 6B and 6C) for engagement with one of the detents 3E. The ball 3D is slidingly supported by the transmission casing 3B either directly or via a bracket. It will be appreciated that the ball 3D could be replaced by a spring biased pin having a hemi-sphericai end. The detents 3E define first, second and third rotational positions corresponding to a selection position for a first row of gears, a selection position for a second row of gears and a neutral position for the transmission 3 and in particular the peaks located between the neutral detent and the in-gear detents determine whether upon releasing the gear lever 11 the transmission 3 will move into gear (pull-in) or into neutral (no pull-in) as will be described in greater detail hereinafter.

Starting with the transmission 3 it can be seen that there is a physical link to the magnetic target 8 in the form of the mechanical connection of the magnetic target 8 to the selector cylinder 3A and a physical connection to the -13 -selected gear sensor 7 in the form of the mechanical connection of the selected gear sensor 7 to the transmission housing 3B.

There is a flux connection between the selected gear sensor 7 and the magnetic target 8 such that variations in flux can be sensed by the selected gear sensor 7 to provide a signal indicative of the axial and rotational positions of the selector cylinder 3A and hence whether the transmission 3 is in an odd gear, an even gear or neutral and which one of the odd and even gears is engaged.

The selected gear sensor 7 continuously outputs signals indicative of the rotational and axial positions of the selector cylinder 3A and these are used to predict the next gear to be engaged by comparing the output signals with various check points.

For example, by carrying out test work the pull-in rotational positions of the selector cylinder 3A can be established. The even and odd gear pull-in positions are shown in Figs. 6B and 60 respectively.

In Fig.6A the selector cylinder 3A is shown in the neutral position and in Figs. 6B and 60 the selector cylinder 3A is shown in positions corresponding to an even pull-in point (EPI) and an odd pull-in point (OPI) . The even pull-in point in this case is reached when the selector cylinder 3A is rotated C degrees from the neutral position and the odd pull-in point is reached when the selector rotation cylinder 3A is rotated -degrees from the neutral position. Clockwise rotation of the selector cylinder 3A is represented on Figs. 6A to 60 as a positive angle and counter clockwise rotation as a negative angle.

If the rotational position at which these pull-in positions (EPI and OPI) are reached is known and the -14 -selected gear sensor 7 is calibrated such that the transmission state module 5 is able to determine from the signals received from the selected gear sensor 7 when these rotational positions are reached then this can be used to predict, before a gear is actually engaged, whether the engaged gear will be an odd gear or an even gear. By combining this information with the axial position of the selector cylinder 3A determined from the axial position signal generated by the selected gear sensor 7 the transmission state module 5 is able to predict the next gear to be engaged.

It will be appreciated by those skilled in the art that the respective odd and even pull-in points are the rotational positions of the shift cylinder 3A where, the various forces acting will rotate the shift cylinder 3A so that the ball 3D fully engages with the respective detent 3E and the corresponding gear will be engaged. That is to say, at and beyond the pull-in point the transmission will automatically be pulled into gear and before the pull-in point is reached the transmission will revert to a neutral gear position.

Referring now to Figs 7A and 7B the two inputs to the transmission state module 5, a sensed rotational position signal (Y axis) and a sensed axial displacement signal (X-axis) . To be more precise, the selected gear sensor 7 outputs a PWM signal which is either in range (between 10% and 90% in this case) or out of range (>90% or < 10% in this case) . Input driver software in the transmission state module 5 interprets the PWM and, if the PWM is out of range (>90% or < 10%) the input driver software sets a guality signal to FAULT. It will be appreciated that the 10 to 90% range is provided by way of example and that the invention is not limited to the use of such a range.

-15 -If the PWM signal is in range (between 10% and 90%) the input driver software sets the quality signal to OK. The transmission state module 5 then oompares the PWM signal to thresholds to determine whether neutral is or is not selected, an odd gear is or is not seleoted, an even gear is or is not seleoted the odd gear pull-in point (OPI) has been reached and the even gear pull-in point (EPI) has been reached.

It can be seen on Fig.7A that the six speed transmission has a conventional H-gate arrangement with the odd gears and reverse arranged in one row and the even gears arranged in another row and that the gears are arranged in a number of gear shift lever planes in which there are arranged reverse gear, and then in the remaining planes two forward gears namely first and second gear (1/ 2 plane), third and fourth gears (3/ 4 plane) and fifth and sixth gears (5/ 6 plane) Referring now to Fig.7E if the PWM signal is substantially 90% then the transmission state module 5 interprets this as an indication that one of the even gears has been selected, if the PWM signal is substantially 10% then the transmission state module 5 interprets this as an indication that one of the odd gears has been selected, if the PWM signal is substantially 50% then the transmission state module 5 interprets this as an indication that neutral has been selected.

It will be appreciated that there may in practice be tolerance bands on all of these figures and, for example, the transmission state module 5 may well operate for the rotational direction with logic tests as follows:-If 85%< PWM < 90% Then engaged gear equals even; (1) If l0%< PWM < 15% Then engaged gear equals odd; (2) If 45%< PWM < 55% Then gear equals neutral. (3) -16 -In addition to these in-gear evaluations the transmission state module 5 also oompares the rotary position signal from the selected gear sensor 7 with two rotational oheok points for the even gear pull-in point (EPI) and for the odd gear pull-in point (OPI) whioh are used to prediot the next gear to be engaged.

For example, as shown on Fig.7B, the transmission state module 5 performs for the rotational direotion the following logio tests:-If PWM< 30% Then predioted next gear equals odd; (4) If PWM> 70% Then predioted next gear equals even. (5) Where, the predefined rotational oheok points EPI and aPI are 70% and 30% respectively.

Using this logio the transmission state sensor 5 is able to prediot by oombining it with the axial position of the shift cylinder 3A the next to be engaged gear before it is aotually engaged. This information oan then be sent several milliseconds earlier (20-4Oms) to other control systems requiring knowledge of gear selection such as a HMI gear indicator or the engine control unit 6 before the gear is actually engaged.

It will be appreciated that the selected gear sensor 7 could also be arranged such that when the transmission 3 is in neutral the corresponding nominal sensor signal is 50%, when the gear lever is moved forwards into one of the odd gears the sensor signal increases above 50% and when one of the even gears is selected the sensor signal decreases below 50% and so the logic tests given above would be reversed in sense e.g. -17 -If 85%< PWM < 90% Then engaged gear equals odd; (1') If 10%< PWM < 15% Then engaged gear equals even; (2') If 45%< PWM < 55% Then gear equals neutral. (3') If PWM< 30% Then predicted next gear equals even; (4') If PWM> 70% Then predicted next gear equals odd. (5') Referring back to Fig.7A the output signal from the selected gear sensor 7 for the axial or X axis direction is shown and it can be seen that for the six speed transmission shown by way of example: If PWM = 10% Reverse gear plane is selected; If PWM = 40% first/ second gear plane is selected; If PWM = 70% third/ fourth gear plane is selected; If PWM = 90% fifth/ sixth gear plane is selected; As before tolerance bands can be applied to these figures to allow for wear or inaccuracies of construction and so in practice the transmission state module may perform for the axial direction the logic tests: If 10% < PWM < 15% Reverse gear plane is selected; (6) If 37.5% < PWM < 42.5% first/ seccnd gear plane is selected; (7) If 67.5% < PWM < 72.5% third/ fourth gear plane is selected; (8) If 85% < PWM < 90% fifth! sixth gear plane is selected; (9) The transmission state module 5 can use the logic tests (4) and (5) above in combination with one of the tests (6) to (9) to predict the next to be engaged gear (N2G) as set out below in Table 1.

-18 -Test Passed Test (4) Passed Test (5) Passed 6 N2G = Reverse / 7 N2G = First N2G = Second 8 N2G = Third N2G = Fourth 9 N2G = Fifth N2G = Sixth

Table 1

The transmission state module 5 can then confirm, when the gear is actually engaged, the engaged gear (EG) after confirmation is received from the selected gear sensor 7 using the logic tests (1) and (2) above in combination with one of the tests (6) to (9) as set out below in Table 2.

Test Passed Test (2) Passed Test (1) Passed 6 EG = Reverse / 7 EG = First EG Second 8 EG = Third EG = Fourth 9 EG = Fifth EG = Sixth

Table 2

Therefore the predictive sensing system also provides information regarding which gear is actually engaged.

It will be appreciated that as referred to in respect of the rotational calibration the axial position calibration could be the opposite of that described above with 10% = sixth gear and 90% = Reverse in which case the logic tests for the plane would be different to those given above.

Although the predictive gear sensing system has been described with respect to the use of a PWM magnetic selected sensor which uses a 2D magnet and generates PWM outputs, the invention is not limited to the use of sensors producing a PWM output it is egually applicable for use with a displacement sensor which generates variable voltage outputs instead of PWM outputs.

-19 -It will also be appreciated that the predictive gear sensing system is not limited to the use of a single 2D magnetic sensor array 7 for the selected gear sensor it may also be put into effect using a 3D sensor and magnet arrangement or two separate sensors one for sensing rotary motion and one for sensing axial motion.

It will also be appreciated that the invention is not limited to a six forward speed transmission or to the positioning of reverse gear as shown in Fig. 7A and that the invention could be applied to transmissions having a different number of forward speeds or a different reverse gear position with equal benefit.

Referring now to Figs. BA to BC there is shown part of a second embodiment of a predictive gear sensing system which in most respects is identical to that previously described and so will not be described again in detail.

The primary difference between this second embodiment and the first embodiment described above is that, in addition to the in-plane check points related to the pull-in points located in the gear shift planes, a plurality of inter-plane check points located between the gear shift planes are also provided.

Referring firstly to Fig. BA there are shown a number of in-plane check points Ra, la, 2a, 3a, 4a, 5a and 6a. The check points Ra, la, 3a and 5a correspond to the odd gear pull-in point (DPI) referred to above and the check points 2a, 4a, and 6a correspond to the even gear pull-in point (EPI) referred to above. The predictive gear system operates as above with respect to these check points and as described above is able to predict the next to be engaged gear.

-20 -In addition to theses in-plane oheok points Ra, la, 2a, 3a, 4a, 5a and 6a, there are also a number of inter-plane check points R/lb, l/2b, 3/4b and 1/2a, 3/4a, 5/6a.

The function of the inter-plane check points is to provide an early indication of the potential plane to be selected while the transmission 3 is still in neutral.

Fig.8B shows the inter-plane check points R/lb, l/2b, 3/4b, l/2a, 3/4a and 5/6a as %PWM outputs from the axial displacement sensor output of the selected gear sensor 7 and Fig.8C replicates Fig.7B with the in-plane check points on Fig.8C (Ra, la, 3a and 5a and 2a, 4a and 6a) corresponding respectively to the aPI and EPI check points on Fig.7B.

Because the inter-plane check points are set-points they are not affected by tolerances in the mechanism and so single values can be used.

For example, the check points shown on Figs. 8a and BB have the assigned %PWM values of: R/lb = 17.5% 1/2a = 32.5% 1/2b = 45% 3/4a = 65% 3/4b = 75% 5/6a = 85% These are used to determine early in the gear selection process the plane likely to be selected and thus one of two potential gear ratios.

Therefore a predictive gear sensing system according to this second embodiment is able to provide further time in which to take any other action such as harmonising engine -21 -speed and transmission input speed by providing an early indication of the action required.

It will be appreciated that the time taken for a driver to move the gear shift lever ii from neutral into a driving gear position is relatively short and so any additional information provided early in a gear selection process is potentially very useful to a system requiring knowledge of the selected gear.

Referring now to Fig.iO there is shown the basic steps required to perform a first embodiment of a method for predicting a gear to be engaged in a multi-speed manual transmission of the type previously described.

The method commences at box 100 with a Key-on event and then in box 110 the driver disengages the clutch in preparation for a gear change or the selection of a gear.

The method then advances to box 120 where the selected gear sensor 7 is used to monitor the movement of a gear shift member such as the shift cylinder 3A and in box 130 the gear shift lever plane is determined. That is to say, in box 130 it is determined in which of the gear shift planes the gear lever 11 currently resides.

Then in box 140 it is determined whether one of the pull in points or in-plane check points EPI, OPI has been reached. If one of the in-plane check points EPI, OPI has been reached then the method advances to box 150 but if neither of the in-plane check points EPI, OPI has been reached the method loops back to box 130 and will continue to loop around the boxes 130, 140 until an in-plane check point EPI, OPI has been reached.

In box 150 it is determined which of the in-plane check points has been reached and based upon this decision the -22 -method advances to either box 160 if the odd gear in-plane check point OPI has been reached or to box 170 if the even gear in-plane check point EPI has been reached.

In boxes 160 and 170 the plane information from box 130 is combined with the information regarding whether the gear to be selected is odd or even to provide a prediction of the next gear to be selected and in box 180 this is provided to any systems requiring this information.

The method then advances to box 190 where it is determined whether a Key-off event has occurred, if it has the method ends at box 200 and if it has not the method continues to box 195 where the gear actually selected is stored for future use and then this information is provided in box 196 to the systems requiring the gear state knowledge as a confirmation of the prediction supplied in box 180.

The method then continues to box 197 where the driver re-engages the clutch 10 and then pauses at box 197 until the driver next disengages the clutch 10 at which point in time it moves back to box 110 to start the method again.

Referring now to Fig.11 there is shown the basic steps required to perform a second embodiment of a method for predicting a gear to be engaged in a multi-speed manual transmission of the type previously described.

The method commences at box 1100 with a Key-on event and then in box 1110 the driver disengages the clutch 10 in preparation for a gear change or the selection of a gear and currently stored values for axial and rotational position are read or a currently selected gear state is read.

The method then advances to box 1120 where the selected gear sensor 7 is used to monitor the movement of a gear shift member such as the shift cylinder 3A and in box 1125 -23 -it is determined whether the gear shift lever is being moved in the same plane (the %PWM signal is substantially constant), in an up gear direction corresponding to an upshift (the %PWM signal is increasing) or in a down gear direction corresponding to a downshift (the %PWM signal is decreasing) . Based upon this determination the method advances to box 1200 if there is no change in-plane, to box 1130 if it is an upchange and to box 1140 if it is a down change.

In box 1130 it is checked whether an upchange inter-plane check point has been passed and, if so, the method advances to box 1150 but, if not, loops back to 1120.

Similarly in box 1140 it is checked whether a downchange inter-plane check point has been passed and, if so, the method advances to box 1150 but, if not, loops back to 1120.

Boxes 1130 and 1140 allow for the use of different upchange and downchange inter plane check points but it will be appreciated if the same check points are used irrespective of gear change direction the method could advance from box 1120 to a box checking whether any inter plane check points have been passed and then, if they have, onto box 1150 but, if they have not, back to 1120.

In box 1150 an interim future gear shift lever plane based upon the check point passed is provided to any systems requiring knowledge of whether the next gear is likely to be higher or lower than the previously engaged gear. This may be a multi-stage step with the information being updated as various inter-plane check points are passed until in box 1200 a pull-in point is passed. That is to say, if the test in box 1200 is failed, the method could alternatively loop back to step 1150 and not as shown to box 1120.

Continuing now with box 1200 it is determined whether a pull-in point that is to say, an in-plane check point, has -24 -been reached. The in-plane check points EPI, aPI are used as before to determine whether the gear to be selected is an odd one or an even one. If a pull-in point has not been reached the method loops back to 1120 and, if a pull-in point has been reached, the method advances to box 1300 where the gear shift lever plane is determined and it is determined whether the pull-in point reached is for an odd gear or an even gear.

Then in boxes 1600 and 1700 the determined gear shift plane from box 1300 that the gear lever 11 currently resides in is combined with the pull-in direction knowledge to produce a prediction of the next selected gear.

Then in box 1800 this prediction is provided to any systems requiring this information.

The method then advances to box 1900 where it is determined whether a Key-off event has occurred, if it has the method ends at box 2000 and if it has not the method continues to box 1950 where the gear actually selected is stored for future use and then this information is provided in box 1960 to the systems requiring the gear state knowledge as a confirmation of the prediction supplied in box 1800.

The method then continues to box 1970 where the driver re-engages the clutch 10 and then pauses at box 1970 until the driver next disengages the clutch 10 at which point in time it moves back to box 1110 to start the method again.

It will be appreciated that the two embodiments of a method for predicting a next to be engaged gear described above are provided by way of example and that the invention is not limited to the specific steps disclosed or the order in which the steps are performed.

-25 -Referring now to Fig.8D there is shown a prediotive gear sensor forming part of a third embodiment of a predictive gear sensing system that could be used to replace the two preferred embodiments described above.

In this case the motion of the shift lever ii is monitored using a large number of separate sensors SR, Si, S2, S3, S4, S5, S6; PR, Pi, P2, P3, P4, P5 and P6. The gear lever has a magnetic target (not shown) attached to it and when it passes by or is in close proximity to one of the sensors SR, Si, S2, S3, S4, S5, S6; PR, Pi, P2, P3, P4, P5 and P6 magnetic coupling occurs which is monitored by the transmission state module 5 so as to form a predictive gear sensing system.

There are two types of sensor shown, the first type SR, Si, S2, S3, S4, S5 and S6 each provide a signal that can be used to indicate when the transmission 3 is fully in the respective gear with which they are associated and the second type PR, Pi, P2, P3, P4, P5 and P6 are check point sensors that provide a signal that can be used to indicate when the transmission 3 is almost in-gear. That is to say, the second type of sensor are used to indicate when the pull-in points referred to above have been reached but not only provide an indication of whether the gear to be engaged is odd or even also provide the plane information so that they are definitive of the gear to be engaged. In Fig.8D the shift lever ii is shown in a first gear selected position hG and in a neutral position uN.

It will be appreciated that further sensors (not shown) could be located between the planes of the H-gate to provide feedback of between plane movement thereby providing information similar to that provided by the check points R/ib, h/2b, 3/4b and i/2a, 3/4a, 5/6a shown on Fig.8A.

-26 -The use of suoh a prediotive gear sensing system oan therefore in some circumstanoes provide more time in whioh to harmonise or synchronise the engine speed with the speed of the input 3i to the transmission 3.

In a manual transmission arrangement as soon as the clutch 10 is disengaged there is no relationship between the speed of the engine 2 and the input speed of the transmission 3 and even if a speed sensor is fitted to the input 3i of the transmission 3 it will not provide specific information until a gear is actually engaged that is to say, during the period when neutral is selected the final speed of the input 3i to the transmission 3 is not known.

Therefore the only time available for adjusting engine speed is the time after the gear is actually engaged while the driver is engaging the clutch 10.

However, in accordance with some embodiments of this invention the next to be engaged gear can be predicted using a predictive gear sensing system so that more time is provided in order to synchronise the speed of the engine output 2a with the input 3i to the transmission 3. That is to say, the required synchronising speed is known before the gear is actually engaged in the case of a FRIN system or FRIG system when a new gear is selected either when a pull-in check point is passed or when an inter plane or between plane check point is traversed thereby providing more time to adjust the engine speed to the required speed.

Referring now to Fig.9 there is shown a chart referencing engine speed against vehicle speed for the motor vehicle 1 shown in Fig.1.

The line X-X shows for a vehicle speed of 20 kph the various engine speeds lg-6g for first through sixth gear.

-27 -From Fig.9 it can be seen that the corresponding engine speeds are:-First gear 2000RPM; second gear 1333RPM; third gear 1000RPM; fourth gear 800RPM; fifth gear 667RPM; and sixth gear 400RPM.

Therefore depending upon the gear selected for the exit from the free rolling phase of operation the engine 2 will theoretically need to be adjusted to an engine speed ranging from 2000RPM to 400 RPM. However, in practice a driver is likely to know that at such a low road speed only first, second and third gears are likely to be suitable for an exit from the free rolling phase of operation. In some embodiments of the invention the system includes a driver warning device if the selected gear is too high or too low.

For example, if the engine speed is below 1000RPM or above 3000RPM, the driver is provided with a warning which may be an audible warning a visual warning such as a the illumination of a warning light or both.

In another embodiment in which the clutch 10 is an e-clutch then engagement of the clutch 10 can be inhibited if the selected gear is too high or too low.

Also if the speed of the motor vehicle 1 falls during the free rolling phase of operation below a predetermined minimum value the free rolling exit can be aborted and the electronic controller can operate in the manner of a conventional stop-start controller. That is to say, if the vehicle speed is zero or approximates to zero the vehicle is no longer free rolling it is stationary.

A system for controlling the motor vehicle 1 during an exit from a free rolling phase of operation operates in accordance with one embodiment in the following manner.

-28 -The powertrain control module 4 receives inputs from the various sensors and, in particular, from the vehicle speed sensor 9v, the engine speed sensor 9e and the selected gear sensor 7.

The speed of the motor vehicle 1 is used to provide an estimate of the reguired engine speed and is continually monitored and updated. It will be appreciated that other means for providing vehicle speed information could be used as an input of vehicle speed such as, for example, global positioning system (GPS) information and that the invention is not restricted to the use of a vehicle speed sensor.

The transmission state module 5 is operable to provide to the engine control unit 6 information concerning either the currently engaged gear or the predicted next to be engaged gear in the manner described above and the engine control unit 6 uses this information to adjust the engine speed to the reguired engine speed based upon information regarding the current vehicle speed. In this way errors in the synchronisation speed are reduced to a minimum and a smooth take up of the drive can be assured. If the information used is based up the predicted next to be engaged gear then the reguired engine speed can be validated or finely tuned when the gear actually engaged is known.

It will also be appreciated that in other embodiments the information supplied to the engine control unit 6 could be the reguired engine speed and that, in such a case, the engine control unit 6 simply provides the control functionality to drive the engine speed to the required speed.

Therefore in summary, a system for controlling the exit from a free rolling phase of operation comprises the engine 2 to provide drive to the transmission 3 via the clutch 10, a gear sensor to provide information indicative of the -29 -engagement state of the transmission 3 to the powertrain control module 4 and in particular to the transmission state module 5, an engine control unit 6 to control and adjust the speed of the engine 2 and a source of information indicative of the speed of the motor vehicle 1 for use by the powertrain control module 4.

With reference to Fig.12 there is shown a generic embodiment of a method for controlling a motor vehicle having a FRIN system during an exit from a free rolling phase of operation.

The method starts at box 300 with a key-on event and then advances to box 305 where the engine 2 is running and the motor vehicle 1 is operating in a normal phase of operation as per any other motor vehicle.

The method then advances to box 310 where there is a check as to whether the conditions for entry to a free rolling phase of operation are present. In the case of a FRIN system these conditions comprise the placing of the transmission 3 into a neutral state while the motor vehicle 1 is still moving. The conditions may also include the requirement for the speed of the motor vehicle 1 to be between predetermined limits. If the entry conditions are not met the method cycles through boxes 305 and 310 until such time as the entry conditions are met at which time the method advances to box 312 where the engine 2 is stopped and the motor vehicle 1 has entered the free rolling phase of operation.

The method then advances to box 315 where it is checked whether the conditions for exiting the free rolling phase of operation which in the case of a FRIN system will include the disengagement of the clutch 10 and the engagement of a driving gear or in the case of a system using a predictive -30 -gear sensing system until an indication is provided that a gear is to be engaged.

If these conditions are not present, the engine 2 will remain stopped, the motor vehicle 1 will remain in the free rolling phase of operation and the method loops back to box 312. The method will continue to loop around the boxes 312 and 315 until the conditions for exiting the free rolling phase are met.

When the conditions in box 315 are met the method advances to box 318 where the gear engaged for the exit is established or the predicted gear for the exit in the case of a system using a predictive gear sensing system is established and the engine 2 is started. It will be appreciated that starting the engine 2 may be a separate step carried out after or simultaneously with the step of determining the gear for exit.

The method then advances to box 320 where the required engine speed for the exit is determined. This can be either be by direct measurement of the rotational speed of the input 3i to the transmission 3 using a sensor or by means of calculation based upon engaged or predicted to be engaged gear.

As soon as the required engine speed is known the method advances to box 325 where the speed of the engine 2 is adjusted by the engine control unit 6 to match the required engine speed.

The method then advances to box 328 where it is determined whether the clutch 10 has actually been engaged.

If the clutch has not been engaged, the method loops back through box 329 to box 320 and the boxes 320, 325 and 328 are re-executed if the vehicle speed is above a predetermined minimum speed (V) which is a speed close to -31 -zero. If the vehicle speed is below the minimum speed (V1) then in box 329 this is detected and the method ends at box 360.

If in box 328 it is determined that the clutch has been engaged, the exit from the free rolling phase is complete and the method then advances to box 330 to check whether a key-off event has occurred.

If a key-off event has not occurred, the method returns from box 330 back to box 305 but, if a key-off event has occurred, the method advances from box 330 to box 350 where it ends.

If the speed of the motor vehicle 1 is constant during the period of time between gear engagement and clutch engagement no engine speed fine tuning adjustments will be reguired. But if the motor vehicle speed 1 has changed then the loop back from box 328 to 320 ensures that such changes in vehicle speed will be taken into account when determining the required engine speed and this fine tuning process will continue until the driver engages the clutch 10.

The method will now be described with reference to Fig.12 with respect to a FRIG system in which free rolling occurs in a driving gear.

The method starts at box 300 with a key-on event and then advances to box 305 where the engine 2 is running and the motor vehicle 1 is operating in a normal phase of operation.

The method then advances to box 310 where there is a check as to whether the conditions for entry to a free rolling phase of operation are present. In the case of a FRIG system these conditions comprise the lack of a request for the supply of torque from the engine 2 and the automatic -32 -disengagement of the clutch 10 while the motor vehicle 1 is still moving. That is to say, the clutch pedal is depressed and the accelerator pedal is not depressed. The conditions may also include the requirement for the speed of the motor vehicle 1 to be between predetermined limits. If the entry conditions are not met the method cycles through boxes 305 and 310 until such time as the entry conditions are met at which time the method advances to box 312 where the engine 2 is stopped and the motor vehicle 1 has entered the free rolling phase of operation. The method then advances to box 315 where it is checked whether the conditions for exiting the free rolling phase of operation which in the case of a FRIG system will include the requesting by the driver of the motor vehicle 1 for the supply of torque by the action of depressing the accelerator pedal.

If these conditions are not present the engine 2 will remain stopped, the motor vehicle 1 will remain in the free rolling phase of operation and the method loops back to box 312. The method will continue to loop around the boxes 312 and 315 until the conditions for exiting the free rolling phase are met.

When the conditions in box 315 are met, the method advances to box 318 where the gear engaged for the exit is established. In most cases this will be the same gear that free rolling was entered with but it is possible that the driver could select another gear during the free rolling phase of operation or during the exit from the free rolling phase of operation. The gear chosen for exit is therefore established, either by use of a selected gear sensing system or, in the case of a system using a predictive gear sensing system, the predicted gear chosen for the exit can be established during the exit procedure and the engine 2 is started. It will be appreciated that starting the engine 2 may be a separate step carried out after or simultaneously with the step of determining the gear for exit.

-33 -The method then advances to box 320 where the required engine speed for the exit is determined. As before, this can be either be by direct measurement of the rotational speed of the input 3i to the transmission 3 using a sensor or by means of calculation based upon engaged or predicted to be engaged gear.

If the clutch has not been engaged, the method loops back through box 329 to box 320 and the boxes 320, 325 and 328 are re-executed if the vehicle speed is above a predetermined minimum speed (V1) which is a speed close to zero. If the vehicle speed is below the minimum speed (V1) then in box 329 this is detected and the method ends at box 360.

If a key-off event has not occurred, the method returns from box 330 back to box 305. If a key-off event has occurred then the method advances from box 330 to box 350 where it ends.

If the speed of the motor vehicle 1 is constant during the period of time between gear engagement and clutch engagement no engine speed fine tuning adjustments will be required. But if the motor vehicle speed 1 has changed then -34 -the loop back from box 328 to 320 ensures that such changes in vehicle speed will be taken into account when determining the required engine speed and this fine tuning process will continue until the driver engages the clutch 10.

It will be appreciated that the two embodiments of a method for controlling a motor vehicle during an exit from a free rolling phase of operation described above are provided by way of example and that the invention is not limited to the specific steps disclosed or the order in which the steps are performed.

It will also be appreciated that if at any time during operation of the vehicle the ignition key is moved to an off position then the method will end at box 350.

As a further addition, the system may be further operable to monitor the vehicle speed during operation of the motor vehicle in the free rolling phase of operation and continuously inform the driver via a display of a suggested gear for the exit from the free rolling phase of operation.

Therefore in summary, the invention presented here

involves adjusting the engine speed to match the transmission input shaft speed in the time between the engine starting and the clutch being engaged. By removing or minimising any speed mismatch, torque disturbances are removed or minimised and the driver feels a smooth re-engagement of driving torque. Determination of the input shaft speed requires either direct measurement or estimation based on vehicle speed and knowledge of the selected gear.

The selected gear can be determined by the use of a selected gear sensing system or by the use of a predictive gear sensing system either of which may determine the gear by measuring the position and rotation of a shift turret or -35 -shift shaft forming part of an H-gate gear shift meohanism for the transmission.

Although the invention is particularly advantageous with respeot to a manual transmission having an H-gate gear shift meohanism it oan be applied to other manual transmissions or automated manual transmissions suoh as for example a twin olutoh transmission having a first olutoh for the odd gears and a seoond olutch for the even gears. In whioh case, the relevant clutch will be the clutch for the gear chosen for exit from the free rolling phase of operation.

The term selected gear system' as meant herein is a system in which a sensor is used to determine the currently engaged gear either by sensing the position of components within the transmission or components of a shift mechanism used to shift gear and provide an output that is supplied to an electronic unit which interprets the signal or signals from the sensor so as to provide an indication of the currently engaged gear. That is to say, a selected gear sensor system could comprise of the selected gear sensor 7 and transmission state module 5 as shown in Fig. lA or a sensor array such as that shown in Fig.8D and the transmission state module 5.

The term predictive gear sensing system' as meant herein is a system in which a sensor is used to sense the position of components within the transmission or components of a shift mechanism used to shift gear and provide an output to an electronic unit. The electronic unit is arranged to interpret the signal or signals from the sensor so as to provide an indication of the next to be engaged gear. That is to say, a predictive gear sensing system' could comprise a selected gear system' with the addition of check points that when traversed can be interpreted by the -36 -transmission state module to provide an indication of the next to be engaged gear.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention as set out in the appended claims.

Claims

-37 -Claims 1. A method for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation wherein the method comprises determining whether one or more conditions for exiting the free rolling phase of operation are present and, if the one or more conditions are present, starting the engine and adjusting the speed of the engine to a required engine speed based upon an input speed of the transmission.
2. A method as claimed in claim 1 wherein the method further comprises determining the input speed of the transmission and adjusting the engine speed to match the input speed of the transmission.
3. A method as claimed in claim 2 wherein determining the input speed of the transmission comprises measuring the input speed of the transmission.
4. A method as claimed in claim 2 wherein determining the input speed of the transmission comprises calculating the input speed based upon a current speed of the motor vehicle.
5. A method as claimed in claim 4 wherein calculating the input speed of the transmission comprises using a gear ratio of the transmission selected for the exit in combination with current vehicle speed and a composite final drive ratio to calculate the input speed of the transmission.
6. A method as claimed in claim 5 wherein the method further comprises using a selected gear sensing system to determine the gear ratio selected for the exit and using the determined gear ratio in the calculation of the input speed of the transmission.

-38 -
7. A method as claimed in claim 5 wherein the method further comprises using a predictive gear sensing system to predict the next to be engaged gear and using the gear ratio of the predicted next to be engaged gear in the calculation of the input speed of the transmission.
8. A method as claimed in claim 7 wherein the method further comprises using the predictive gear sensing system to determine the actual gear ratio selected for exit and using the actual gear ratio in the calculation of the input speed of the transmission.
9. A method as claimed in any of claims 1 to 8 wherein during the free rolling phase of operation the clutch is engaged and the transmission is in neutral and the one or more conditions for exiting the free rolling phase of operation comprise engagement of a forward gear of the transmission.
10. A method as claimed in any of claims 1 to 6 wherein during the free rolling phase of operation the clutch is disengaged and the transmission is in gear and the one or more conditions for exiting the free rolling phase of operation comprise a request for the supply of torque from the engine.
11. A system for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation wherein the system comprises a controller operable to determine whether one or more conditions for exiting the free rolling phase of operation are present and, if the one or more conditions are present, start the engine and adjust the speed of the engine to a required engine speed based upon an input speed of the transmission.

-39 -
12. A system as claimed in claim 11 wherein the system further comprises a sensor to measure the input speed of the transmission and the required engine speed is an engine speed that matches the input speed of the transmission.
13. A system as claimed in claim 11 wherein the controller is operable to use a gear ratio of the transmission selected for the exit in combination with current vehicle speed and a composite final drive ratio to calculate the input speed of the transmission and the required engine speed is an engine speed to match the calculated input speed of the transmission.
14. A system as claimed in claim 13 wherein the transmission is a manual transmission and the system further comprises a selected gear sensing system for determining the gear ratio selected for the exit.
15. A system as claimed in claim 13 wherein the transmission is a manual transmission and the system further comprises a predictive gear sensing system for predicting the next to be engaged gear and the controller is operable to use the gear ratio of the predicted next to be engaged gear in the calculation of the input speed of the transmission.
16. A system as claimed in claim 15 wherein the predictive gear sensing system is further used to determine the actual gear ratio selected for exit and the actual gear ratio selected is used by the controller in the calculation of the input speed of the transmission.
17. A system as claimed in any of claims 11 to 16 wherein during the free rolling phase of operation the transmission is in neutral and determining whether the one or more conditions for exiting the free rolling phase of -40 -operation include the sensing of engagement of a forward gear of the transmission.
18. A system as claimed in and of claims 11 to 16 wherein during the free rolling phase of operation the clutch is disengaged and the transmission is in gear and determining whether the one or more conditions for exiting the free rolling phase of operation comprise sensing a reguest for the supply of torgue from the engine.
19. A motor vehicle having a system as claimed in any of claims 11 to 18.
20. A method for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation substantially as described herein with reference to the accompanying drawing.
21. A system for controlling a motor vehicle having an engine driving a transmission via a clutch during an exit from a free rolling phase of operation substantially as described herein with reference to the accompanying drawing.
22. A motor vehicle substantially as described herein with reference to the accompanying drawing.