The present invention refers to an arrangement for a cruise control system for a motor vehicle according to the preamble to claim 1.

State of the art

It is becoming increasingly common for various types of motor vehicles to be provided with cruise control systems (constant speed maintenance systems).

The control units which currently exist for such cruise control systems are usually designed to be able to activate a number of predetermined functions such as setting and adopting a desired set speed and switching off with or without cancellation of the setting.

There are both simple solutions which comprise only these basic functions and more advanced designs which allow a number of set speeds to be stored. However, such advanced solutions are often complicated and relatively expensive, involve a number of buttons or controls and often require the operator to be well acquainted with how to achieve the various functions, which is unfortunate from a safety point of view.

In both cases the control unit is designed to activate only these specific functions.

There are at present no cruise control units which are designed to be adaptable to a variety of embodiments whereby a uniform design of control unit can be used, simply by applying different software to it, to adapt the cruise control system to being able to activate the specific functions desired for a particular vehicle.

Objects of the invention

The object of the present invention is to create an arrangement for a motor vehicle cruise control system which can easily be adapted to activate alternative functions without impairing safety.

To this end, the arrangement according to the invention is distinguished by the features expressed in the characterising portion of the main claim. A switch forming part of the arrangement has one position for a selectable function for

accessing a stored set speed whereby this position can only be reached by the switch first passing through another position at which a signal is given for switching off the system. This means that whatever function is chosen for the selectable position, the cruise control system is switched off when the function is activated and there is no risk of undesired acceleration.

According to an advantageous embodiment, the switch takes the form of a sliding contact which is urged towards a neutral position by a spring device.

According to a first embodiment, the selectable position corresponds to an ON/OFF function whereby alternate signals respectively activate the cruise control system and switch it off with cancellation of the set speed.

This solution also means that stopping the engine automatically switches off the system, which is thus in the OFF position the next time the cruise control system comes into operation. Such a solution has further great advantages from the safety point of view and may be extremely advantageous in vehicles which often have different drivers who are not familiar with the system, e.g. hire vehicles.

According to another embodiment, the cruise control system can store a number of different set speeds whereby the selectable position corresponds to a function for accessing another stored set speed and the memory is accessed according to a predetermined sequence. This solution is advantageous in vehicles in which the operator often uses the system.

Further features and advantages of the arrangement according to the invention emerge from the accompanying description and an embodiment example. The description refers to the accompanying diagrams in which all the numerical notations denote mutually corresponding items.

List of drawings

Figure 1 shows a control unit for a cruise control system situated on a flasher control lever in a motor vehicle.

Figure 2 shows schematically the control unit mechanism for signal transmission to the cruise control system.

Description of an embodiment

Figure 1 shows a control unit 1 for a cruise control system for a motor vehicle, e.g. a private car, situated on a flasher control lever 2 incorporated in the vehicle.

The control unit 1 has a first switch 4 which in the diagrams is in a normal position 6. The switch 4 is movable between the normal position 6 and a first and a second position 8, 10 in a first direction from the normal position 6 (to the left in the diagrams) and a third position 12 in an opposite direction from the normal position 6 (to the right in the diagrams). The switch 4 is here formed as a sliding contact and is urged towards the neutral position 6 by a spring device 7, which means that the first, second and third positions 8, 10, 12 are unstable. There is also a second switch 14 in the form of a spring-back push-button which is movable between an outer stable position 16 and a pressed-in unstable position 18. Moving the two switches 4, 14 between the various positions produces signals via a number of signal lines 20, 22, 24 (shown in figure 2) to a control unit 21 which forms part of the cruise control system and receives certain predetermined functions which are previously known per se and occur in many cruise control systems. In the embodiment example, the signals consist of a three-digit code whereby each signal line 20, 22, 24 can have two signal levels (signal or no signal).

The control unit 21 gives signals via a cluster of lines 25 in a known manner to the engine control system for controlling the drive power and hence the vehicle's speed.

The first position 8 of the sliding contact 4 corresponds to a function for temporarily switching off the cruise control system without cancelling its set speed, this is commonly called a TIP-OFF function, while the third position 12 corresponds to a function for adopting a speed set by the driver in the control unit 21, this is commonly called a RESUME function. It is previously known and commonly the case that control units for cruise control systems have TIP-OFF and RESUME functions situated on mutually opposite sides of the normal position.

In the arrangement according to the invention, the sliding contact 4 also assumes a second position 10 which is situated beyond the first position 8; this position 10 corresponds to a function for accessing a set speed stored in a memory unit (not shown here) situated in the control unit 21 and can only be reached by the sliding contact 4 passing through the first position 8 at which the control unit 21 receives the signal for the TIP-OFF function. The function for this second position 10 may be chosen according to the characteristics desired. This is done by choice of software for the control unit 21.

According to a first embodiment, the second position 10 corresponds to a ON/OFF function whereby alternate signals respectively activate the cruise control system and switch it off with cancellation of set speed.

According to a second embodiment, the control unit 21 can impose a number of different set speeds where the second position 10 corresponds to a function for accessing other set speeds and where the memory is accessed according to a predetermined sequence. This solution requires either that a third switch (not shown here) for the ON/OFF function is situated somewhere else, e.g. on the instrument panel, or that the first signal after the voltage of the control unit 1 has been set produces an ON function. Various characteristics of the respective embodiments are described later on. The invention thus means that thecruise control system can be adapted to different functions without having to alter the structural design of the control unit 1.

Pressing in the push-button 14 brings in the function for speed setting, this is commonly called the SET function.

Holding the push-button 14 in the pressed-in position 18 gives the control unit a signal to accelerate the vehicle at a predetermined rate until the button 14 is let back to the stable position 16. A decelerating function is correspondingly achieved by holding the sliding contact 4 in the third position 12. Both these functions are also previously known.

Figure 2 shows schematically the mechanism of the control unit 1 for conveying signals to the cruise control system. It shows a contact unit 5 associated with the sliding contact 4 and a contact unit 15 associated with the push-button 14. First, second and third signal lines 20, 22, 24 connect the control unit 1 to the cruise control

system control unit 21. An incoming line 26 carries the power supply for the control unit 1 and is advantageously connected to the vehicle's electrical system.

When the sliding contact 4 is in the neutral position 6, it is not connected to the incoming line 26, thus no signal can be conveyed to the control unit 21.

Moving the sliding contact 4 from the normal position 6 to the first position 8 puts the contact unit 5 in contact with a first contact device 80 containing a first contact part 82 connected to the incoming line 26, a second contact part 86 connected to the second signal line 22 and a third contact part 88 connected to the third signal line 24. Contact between the contact unit 5 and the first contact device 80 thus results in a signal being conveyed from the incoming line 26 to the control unit 21 via the second and third signal lines 22, 24. This signal gives as previously mentioned the TIP-OFF function.

As this position 8 is not an end position, the operator should get a confirmation that the position 8 has been assumed, which may for example be achieved by the sliding contact 4 cooperating in a known manner with a clicking device.

Moving the sliding contact 4 to the second position 10 analogously creates contact between the contact unit 5 and a second contact device 100 containing a first contact part 102 connected to the incoming line 26, a second contact part 104 connected to the first signal line 20, a third contact part 106 connected to the second signal line 22 and a fourth contact part 108 connected to the third signal line 24. Contact between the contact unit 5 and the second contact device 100 thus conveys a signal from the incoming line 26 to the control unit 21 via all the signal lines 20, 22, 24. As previously mentioned, the function of the signal depends on the choice of software for the control unit 21.

Finally, moving the sliding contact 4 to the third position 12 likewise analogously creates contact between the contact unit 5 and a third contact device 120 containing a first contact part 122 connected to the incoming line 26 and a second contact part 128 connected to the third signal line 24. Contact between the contact unit 5 and the third contact device 120 thus conveys a signal from the incoming line 26 to the control unit 21 via only the third signal line 24. This signal gives as previously mentioned the RESUME function.

Pressing the push-button 14 in to the position 18 creates contact between the contact unit 15 and a fourth contact device 180 containing a first contact part 182 connected to the incoming line 26 and a second contact part 186 connected to the second signal line 22. Contact between the contact unit 15 and the third contact device 180 thus conveys a signal from the incoming line 26 to the control unit 21 via the second signal line 22. This signal gives as previuosly mentioned the SET function.

It is advantageous for the contact unit 5 of the sliding contact 4 and the contact parts 82, 86, 88, 102, 104, 106, 108, 122, 128 of the various contact devices 80, 100, 120 to be formed as sliding contact surfaces, thereby keeping them free from oxide. This means that low currents can be permitted by the control unit 1 , resulting in low effect development and consequently less heat in the control unit 21.

As shown in Figure 2, the first contact parts 82, 102 of the first and second contact devices 80, 100 consist of a common contact surface. The same also applies to the third contact parts 86, 106 of the first and second contact devices 80, 100 and to the fourth contact parts 88, 108, 128 of the three contact devices 80, 100, 120. It also shows that moving the contact unit 5 of the sliding contact 4 to the first position 8 creates contact with the second contact part 86 before the first one 82, since the second contact part 86 has a longer extent a in the direction of the neutral position 6.

The order in which the various contact parts 82, 86, 88, 102, 104, 106, 108, 122, 128 are brought into contact with the sliding contact 4 for the desired signal to be conveyed to the control unit 21 has to be clearly defined. If, for example, the distance a was zero or negative, moving the sliding contact 4 to the first position 8 for TIP-OFF function might convey signals via only the third signal line 24 in the initial stage of the contact creation phase, which the control unit 21 would interpret as RESUME. This might result in unexpected retardation of the vehicle and simultaneous absence of the disconnection expected by the driver, which would obviously be extremely inappropriate. This embodiment's long continuous contact surface 88, 108, 128 on the third signal line also eliminates one of the greatest conceivable safety risks, namely that signals at the time of trying to disconnect might only be conveyed via the second signal line 22, which would produce the SET function resulting in unexpected acceleration.

The embodiment described has a further advantage in the event of both the switches 4, 14 being inadvertently moved to the right with simultaneous conveying of signals to the control unit 21 via the second and third lines 22, 24, which the control unit would interpret as TIP- OFF, i.e. a disconnecting function. This embodiment means that critical functions which can make the vehicle accelerate can only be achieved by moving one of the switches 4, 14 to the right.

The invention also means that reaching the second position 10 involves the sliding contact 4 first passing through the first position 8 at which the cruise control system is switched off by the TIP-OFF function. The spring device 7 returns the sliding contact 4 to the neutral position after the operator action has ceased, thereby again passing through the first position 8. Thus the cruise control system is always switched off after completion of signal transmission from the second position 10 irrespective of the particular function which this position 10 has in the cruise control system.

As previously mentioned, the function of the second position 10 can be varied by changing the software of the control unit 21 according to the characteristics desired.

According to a first embodiment, the second position 10 corresponds to an ON/OFF function whereby alternate signals respectively activate the cruise control system and switch the system off with cancellation of set speed.

Such a solution has great advantages from a safety point of view and may be extremely advantageous for vehicles which often have different drivers who are unfamiliar with the system, e.g. hire vehicles. This solution means that stopping the engine automatically switches off the cruise control system, which will thus be in the OFF position the next time the vehicle starts up. To be able to use the system, it is therefore necessary first to move the sliding contact 4 to the second position 10, which reduces the risk of operators not familiar with the cruise control system unintentionally activating it by the push-button 14. As the signal from the second position 10 is conveyed via all the signal lines 20, 22, 24, all of these must function for it to be possible to activate the system. If the second or third signal lines 22, 24 do not convey signals to the control unit 21 when the sliding contact 4 is in the

second position 10, the control unit will interpret this as a fault in the control unit 1 , making it impossible to activate the cruise control system.

According to a second embodiment, the memory unit of the control unit 21 can store a number of different set speeds if the second position 10 corresponds to a function for accessing another stored set speed where the memory is accessed according to a predetermined sequence. This means that a memory is "opened" by moving the sliding contact 4 to the second position 10. Thereafter the push-button 14 is used to set in a known manner the desired speed, which is then adopted by moving the sliding contact 4 to the third position 12 for RESUME function.

This solution is advantageous for vehicles where the operator often uses the cruise control system. It is advantageous for two set speeds to be stored in the memory unit of the control unit 21, which is accessed alternately by moving the first switch to the second position 10 repeatedly. The sliding contact 4 has of course here too first to pass through the first position 8 at which the cruise control system is switched off by the TIP-OFF function after completion of signal transmission from the second position 10. This means that there can be no undesired acceleration when changing set speed. This solution does however require either a third switch for the ON/OFF function situated somewhere else, e.g. on the instrument panel, or an ON function resulting from the first movement of the sliding contact 4 to the second position 10 after the voltage of the control unit 1 has been set. This latter alternative involves the disadvantage that the cruise control system can only be switched off by disconnecting the power supply to the control unit 1, e.g. by stopping the engine. It is advantageous for a separate third switch to be designed so that stopping the engine automatically switches off the cruise control system, which will thus be in the OFF position the next time the cruise control system comes into operation. Here too it is the case that the signal from the second position 10 is conveyed via all the signal lines 20, 22, 24, so all of these must function for it to be possible to activate the system. If the control unit 21 of the cruise control system is provided with a diagnostic unit, the system could be automatically disconnected if the second or third signal lines 22, 24 do not convey signals to the control unit 21 when the sliding contact 4 is in the second position 10, owing to the control unit 21 interpreting this as a fault in the control unit 1.

In this second embodiment it is advantageous to provide some indication on the instrument panel so that the operator can easily obtain information about the current state of the cruise control system, such as ON/OFF, current memory, set speed, etc.

Accordingly, the invention means that the cruise control system can be adapted to various functions without having to alter the structural design of the control unit 1. As reaching the selectable second position 10 involves passing through the first position 8 at which the control unit 21 disconnects the cruise control system by the TIP-OFF function, there is no risk of unexpected acceleration, irrespective of what function the second position 10 has.

The embodiments described above may not create any limitation on the invention, which may be utilised in a multiplicity of alternative forms, e.g. the sliding contact may be replaced by a toggle switch and the design and mutual positioning of the various signal lines and contact parts may be varied infinitely so long as the control unit receives unambiguous signals.