A TRANSMISSION CONTROL SYSTEM

Abstract: A transmission control system for a vehicle (10) is disclosed which includes a continuously variable transmission (CVT) (14). The invention provides a kit of parts to upgrade a base model to a higher specification model after initial purchase. The kit of parts provides an interchangeable shift mechanism (22, 24) with increased functionality and further includes alteration of the transmission controller software by a programming means to "enable" the additional features. Additional features available include an alteration to the spacing between simulated fixed ratios so as, for example, to simulate a close ratio manual transmission. Another option includes altering the number of simulated fixed ratios available using a sequential shift +/-.

Description: A Transmission Control System This invention relates to transmission control systems and in particular to a transmission control system for a vehicle and to a method of controlling such a system. It is known to provide a range of vehicles originating from a base model specification and to provide increased features and functionahty in vehicles higher up the model range. If, however, somebody who has purchased a base or low model range vehicle later wishes to upgrade it to a higher specification it can prove difficult to do so without major alterations to the vehicle and it often proves more cost effective to trade the vehicle in against a higher specification model. One example of such a situation occurs when the base model in a vehicle range has one transmission control system and a vehicle higher up the model range has a more sophisticated transmission control system to which an owner may wish to upgrade during his ownership of the vehicle. It is an object of this invention to provide an improved transmission control system for a vehicle and a method of controlhng such a transmission control system. According to the invention there is provided a transmission control system for a vehicle comprising a continuously variable transmission under the control of a transmission controller, the controller being arranged in use to control the output ratio of the transmission between at least two modes of operation of the continuously variable transmission, in one of which modes the ratio is varied only in a continuous manner and in a second of which modes the ratio is varied in a stepped mode of operation in which the output ratio is varied between simulated fixed ratios, wherein the controller can be selectively arranged in use to alter the range of available simulated fixed ratios. The range of simulated fixed ratios may be altered by a change in the spacing between said ratios. The spacing may be reduced between said ratios, whereby the controller may be altered in order to simulate a substantially close ratio manual transmission. The range of simulated fixed ratios may be altered to provide an increased or decreased number of said ratios and the controller may be arranged to alter the range of simulated fixed ratios in response to an input to the controller from a programming means. The alteration may be reversible and may be temporary. The invention also provides an alteration kit for a transmission control system according to the invention, the kit comprising a substitute transmission ratio selector mechanism which is substituted in use for an original transmission ratio selector mechanism used to operate the system in its unaltered state, the substitute transmission ratio selection mechanism comprising means to provide control over the altered range of simulated fixed ratios and which control means are not included in said original transmission ratio selection mechanism. The invention also provides a method of controlling a transmission control system of a vehicle comprising a continuously variable transmission, the transmission being under the control of a transmission controller arranged in use to control the output ratio of the transmission between at least two modes of operation, in one of which modes the ratio is varied only in a continuous manner and in a second of which modes the ratio is varied in a stepped mode of operation in which the output ratio is varied between simulated fixed ratios, the method including selectively altering the range of simulated available fixed ratios. The method may include varying the range of simulated fixed ratios by varying the spacing between said ratios. The method may include reducing the spacing between the simulated fixed ratios, whereby the method includes altering the controller in order to simulate a substantially close ratio manual transmission. The method may include altering the range of simulated fixed ratios by increasing or decreasing the number of said ratios and may include reprogramming the controller using a programming means in order to alter the range of simulated fixed ratios. The method may include altering said range of simulated fixed ratios in a reversible manner and may include altering said range of simulated fixed ratios temporarily. The method may include substituting a substitute transmission ratio selector mechanism for an original transmission ratio selector mechanism which is used to operate the system in its unaltered state, the substitute transmission ratio selection mechanism comprising means for controlhng the altered range of simulated fixed ratios and which control means are not included in said original transmission ratio selection mechanism The invention also provides a controller for a transmission control system of a vehicle, the controller being arranged to operate according to the method of the invention. The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a prior art vehicle having a known transmission control system; Figure 2 is a schematic diagram of the vehicle of Figure 1 including a modified transmission control system in accordance with the invention; Figure 3 is a flow diagram outlining a protocol for alteration of a vehicle transmission; and, Figure 4 is a flow diagram outlining the manner of vehicle transmission set-up. Referring to Figure 1, a vehicle 10 has an engine 12 connected to a transmission 14 which provides drive to a rear axle 16. The transmission 14 is a continuously variable transmission (CVT) 14 and is controlled by a selector mechanism 18 through a CVT controller 20. The transmission selector 18 provides a limited range of options to the user, which comprise; park 'P', reverse 'R', neutral 'N', drive 'D' and low 'L'. In each position of the selector 18, the CVT controller is arranged to vary the output ratio of the CVT 14 in a continuous manner. Referring now to Figure 2, an upgrade kit is provided for the vehicle 10 of Figure 1. One version of the upgrade kit provides a replacement selection mechanism 22 which is interchangeable by substitution with the selection mechanism 18 and provides the additional functionality of a sequential shift + / A second version of the upgrade kit comprises a replacement steering wheel 24 which can be supplied instead of the shift mechanism. 22 or in addition to it. The steering wheel 24 includes its own sequential shift in the form of a pair of buttons + / -. The same CVT controller 20 is used whether the first stage upgrade kit 22 is chosen or the enhanced upgrade kit 22, 24. In each case, the CVT controller 20 is adapted to operate with the upgrade kit by an alteration to its software using a tuning aid programming means (not shown), thereby preventing the need for a customer to buy a new controller when upgrading the vehicle 10. The use of a CVT controller 20 to control an associated CVT 14 enables further enhancements to be added as optional extras available to the user of the CVT upgrade kits. Because it is the use of a control method in the CVT controller 20 which enables the simulation of the fixed ratios for the CVT 14 and thus also the sequential shift + / -, it is possible to provide an increased or a decreased number of simulated fixed ratios for different specification upgrade kits. The CVT controller 20 could also be modified to offer a CVT torque-down option of the type disclosed in the applicants' co-pending application PCT/GB98/01288 or a sports driving mode of the type disclosed in the applicants co-pending application GB9720172.7, the disclosures of both of which are incorporated herein by way of reference. In a further example of how this invention can be put into effect, the CVT controller 20 can also be modified to alter the spacing between the simulated fixed ratios by moving their operating points along their respective output characteristic curves, which are stored in a memory of the CVT controller 20. This feature could be used to alter the CVT 14 in its stepped mode to simulate a close ratio manual transmission, for example for motor sport applications. In this case it may be found desirable to make the alteration only temporary so that, for example, a user can drive on a road with normal ratios and only use the close ratios on a race track. The changes made by fitting an upgrade kit are reversible because, for example, if the vehicle 10 were to be passed to a different user such as a younger person with less driving experience, it may prove desirable to revert to a standard specification to keep insurance costs as low as possible. In a similar case, the invention can also be used to de-tune a vehicle by lowering its potential performance so that, for example, an inexperienced user can buy a high performance vehicle 10 and arrange for it to be reduced in performance until they have sufficient driving experience to cope with the higher performance and to then have it restored to full power later. In this manner, upgrade kits 22, 24 can be supplied after the initial purchase of the vehicle 10 in order to provide an increased number of control functions of the transmission 14 with respect to the control functions available using the originally fitted transmission selector 18. In Figure 3 a potential protocol or sequence of events which could lead to a desire by a vehicle owner to up-grade or down grade their vehicle is illustrated. Thus, initially a customer or vehicle owner orders a vehicle with a base model level of features A at decision stage 31. After an appropriate time period, that vehicle owner or a subsequent purchaser of the vehicle determines that they would like to up-grade the vehicle at decision stage 32 ad so returns to an appropriate source i.e. a vehicle dealer in order to arrange for the necessary changes. Clearly, there are a range of options, some alterations may be made without alteration to the installed vehicle equipment such as gear selection mechanism and so may only require changes to the transmission controller operational configuration or procedure whilst other options will require a combination of controller and equipment alterations. All the options available will be presented to the owner and a choice made a decision stage 33. Thus, in the example illustrated, additional features B and C are selected. The owner is then charged for these additional features B and C at stage 34 by the dealer and that dealer then orders the necessary additional parts and obtains an authorisation from normally the original vehicle manufacturer (OVM) in order to effect the necessary changes to the transmission controller etc. at stage 35. With such an authorisation code the dealer can alter the transmission controller operational procedures to reflect the additional features by simple access to the controller through a maintenance or service diagnostic tool interrogation port at an input stage 36. Once all the necessary changes to the controller and any equipment replacements have been made the now up-graded or at least altered vehicle is returned to the vehicle owner at stage 37. As indicated previously the features which may be altered or added to the transmission control regime include closer available gear ratios or sequential gear shift + / - switching or a greater or lesser number of gear ratio transient stage as the vehicle is accelerated or slowed. In short, the present control system allows a vehicle owner to alter his vehicle to more appropriately reflect their life style, experience or expectations. It will also be understood that the present invention allows a vehicle dealer to alter at their own choice their vehicle stock, both new and used, in order to more instantly respond to the current customer requirements. Thus, a customer may be able to see a stock vehicle and then have it altered to meet their specific requirements rather than wait for a new vehicle to be delivered from the factory or wait for a suitable used vehicle to become available. Furthermore, any temporary or loan vehicle give to a service or repair customer may be altered to the transmission control specification that customer is familiar with. Alternatively, the transmission set-up could be varied dependent upon weather conditions, driver experience or simple driver preference through appropriate sensors or switch gear. In Figure 4 a flow diagram illustrating how a vehicle transmission control arrangement is set-up in accordance with the present invention is depicted. Thus, at a vehicle start-up stage 41, a transmission controller for the vehicle is initialised and control features A, B and C are transferred to a transmission set-up and control module 42 from respective feature control modules 43, 44, 45. These modules 43, 44, 45 in effect store the necessary instruction set for their respective transmission control feature A, B, C so that the transmission control set-up module 42 can retrieve these instruction set(s) when required. Typically, as indicated above, the instruction sets for features A, B, C will normally be input to the modules 43, 44, 45 by a vehicle dealer or original vehicle manufacturer (OVM) through a service port or duct 46 comprising schematically respective data input conduits 47, 48, 49. It will be understood to avoid complication, it may be that a full range of instruction sets for features A, B, C will be loaded to the transmission controller in respective modules 43, 44, 45 by the OVM and so the dealer or other personnel then mere requires from the OVM an appropriate authorisation code in order to activate the desired instruction set for that transmission feature A, B, C. In such circumstances, the module 42 may only receive an instruction set for one feature i.e. A whilst access to the other features B, C through their instruction set is barred until authorisation is received for interrogation by the module 42 to provide those features B, C. Once the modules 43, 44, 45 have been appropriately authorised by the dealer or otherwise, it will be understood further control may be effected by current driver choice or vehicle owner choice or operational circumstances in terms of engine condition or weather conditions through suitable sensors or specific switching by the owner or driver. In such circumstances, it will be understood that there will be a control loop in which continued vehicle operation will be monitored periodically at a vehicle operation stage 50. Thus, if the vehicle is still operating then there is a return through the control loop 51 to the vehicle start stage 41 where the appropriate switches and sensors will be polled in order to determine which of the modules 43, 44, 45 should remain activated for input to the transmission set-up module 42 in view of current requirements and/or operational conditions. Alternatively, the instruction sets in modules 43, 44, 45 for features A, B, C could be adjusted to suit those requirements and/or conditions or simply to prevent radical changes to vehicle performance which may be confusing to the driver and possibly dangerous. Clearly, if vehicle operation should stop then the control loop 51 is broken and restarted at the vehicle start stage 41. The instruction sets provided in modules 43, 44, 45 may take the form of operand values for inclusion in existing system transmission control procedures embedded and generic to the transmission controller. Thus, as indicated previously, changing between the available gear ratios will not require too complicate an alteration to the existing system transmission control method or procedures inherent to the vehicle. In such circumstances, the potential for operational errors due to transmission control up-grade or alteration input is diminished. Furthermore, the system control procedure of the controller may include appropriate check stages in order to flag any inadmissible instruction set combinations as a further safety feature to avoid errors etc.

Claims: CLAIMS 1. A transmission control system for a vehicle comprising a continuously variable transmission under the control of a transmission controller, the controller being arranged in use to control the output ratio of the transmission between at least two modes of operation of the continuously variable transmission, in one of which modes the ratio is varied only in a continuous manner and in a second of which modes the ratio is varied in a stepped mode of operation in which the output ratio is varied between simulated fixed ratios, wherein the controller can be selectively arranged in use to alter the range of simulated fixed ratios. 2. A system according to Claim 1, wherein the range of simulated fixed ratios is altered by a change in the spacing between said ratios. 3. A system according to Claim 2, wherein the spacing is reduced between said ratios, whereby the controller is altered in order to simulate a substantially close ratio manual transmission. 4. A system according to any preceding claim, wherein the range of simulated fixed ratios is altered to provide an increased or decreased number of said ratios. 5. A system according to any preceding claim, wherein the controller is arranged to alter the range of simulated fixed ratios in response to an input to the controller from a programming means. 6. A system according to any preceding claim, wherein the alteration is reversible. 7. A system according to any preceding claim, wherein the alteration is temporary. 8. A transmission control system substantially as described herein with reference to the accompanying drawings. 9. An alteration kit for a transmission control system according to any preceding claim, the kit comprising a substitute transmission ratio selector mechanism which is substituted in use for an original transmission ratio selector mechanism used to operate the system in its unaltered state, the substitute transmission ratio selection mechanism comprising means to provide control over the altered range of simulated fixed ratios and which control means are not included in said original transmission ratio selection mechanism. 10. A method of controlhng a transmission control system of a vehicle comprising a continuously variable transmission, the transmission being under the control of a transmission controller arranged in use to control the output ratio of the transmission between at least two modes of operation, in one of which modes the ratio is varied only in a continuous manner and in a second of which modes the ratio is varied in a stepped mode of operation in which the output ratio is varied between simulated fixed ratios, the method including selectively altering the range of simulated fixed ratios. 11. A method according to Claim 10, including varying the range of simulated fixed ratios by varying the spacing between said ratios. 12. A method according to Claim 11, including reducing the spacing between the simulated fixed ratios, whereby the method includes altering the controller in order to simulate a substantially close ratio manual transmission. 13. A method according to any one of Claims 10 to 12, including altering the range of simulated fixed ratios by increasing or decreasing the number of said ratios. 14. A method according to any one of Claims 10 to 13, including reprogramming the controller using a programming means in order to alter the range of simulated fixed ratios. 15. A method according to any one of Claims 10 to 14, including altering said range of simulated fixed ratios in a reversible manner. 16. A method according to any one of Claims 10 to 15, including altering said range of simulated fixed ratios temporarily. 17. A method according to any one of Claims 10 to 16, including substituting a substitute transmission ratio selector mechanism for an original transmission ratio selector mechanism which is used to operate the system in its unaltered state, the substitute transmission ratio selection mechanism comprising means for controlling the altered range of simulated fixed ratios and which control means are not included in said original transmission ratio selection mechanism 18. A method substantially as described herein with reference to the accompanying drawings. 9. A controller for a transmission control system of a vehicle, the controller being arranged to operate according to the method of any one of Claims 10 to 18.

Inventors: JACKSON NEIL DAVID, SMITH ANDREW CHARLES OSBORNE, JACKSON, NEIL, DAVID, SMITH, ANDREW, CHARLES, OSBORNE
Applicants: JACKSON NEIL DAVID, ROVER GROUP, SMITH ANDREW CHARLES OSBORNE, JACKSON, NEIL, DAVID, ROVER GROUP LIMITED, SMITH, ANDREW, CHARLES, OSBORNE
Application year: 1999
Main classification: F16H61
IPC codes: F16H61