DE112017002814T5 - Method and system for controlling the change of the transmission ratio in a vehicle - Google Patents

Abstract

The present invention relates to a method for controlling the change in gear ratio in a transmission (103) of a vehicle (100), wherein the transmission (103) for transmitting energy from a power source (101) to at least one drive wheel (113, 114) of the Vehicle (100) is provided, wherein the transmission (103) comprises a plurality of selectable gear ratios, wherein the change of the gear ratio is controlled by a vehicle control system, the vehicle further comprises a driver operable means for requesting energy from the power source, wherein the method comprises the steps of: detecting a reduced adhesion of at least one drive wheel of the vehicle, determining whether the actuation by the driver of the driver-operable means for requesting energy indicates reduced adhesion, and influencing an operation of changing the Translation ratio in the Get (103) when actuation of the driver operable means for requesting energy by the driver indicates reduced adhesion.

Description

Field of the invention

The present invention relates to vehicles, and more particularly to a method and system for controlling a change in gear ratio in a vehicle. The present invention also relates to a vehicle and to a computer program and computer program product implementing the method according to the invention.

Background of the invention

There are several types of vehicle powertrains. For example, vehicle transmissions may be of an automatic type, with a vehicle control system fully controlling the processes of changing the transmission ratio. The transmissions used in these systems may include, for example, conventional automatic transmissions with torque converters, but also automated manual transmissions.

Automatic gear shifting in utility (heavy) vehicles, especially in long distance vehicles, often involves a control system-controlled gear shift from manual transmissions, i. automatic control of transmissions with a discrete number of fixed gear ratios (i.e., gears). In the operation of such vehicles, the transmission is often controlled by the vehicle control system to select the gear ratio depending on the current driving conditions.

In general, it is often desirable to drive the vehicle with as high a gear as possible (i.e., the lowest possible gear ratio taking into account the circumstances) in order to reduce the rotational speed of the power source, often an internal combustion engine, and thus reduce fuel consumption. Therefore, when choosing the gear ratio, fuel consumption is often an issue. However, the vehicle should generally also be driven at a gear ratio capable of propelling the vehicle in a desired manner. This is generally the case, but when the vehicle is accelerating or decelerating, it is often necessary for the transmission of the vehicle to be tuned to a gear ratio that is capable or capable of providing enough power to drive the vehicle without undesirable deceleration , eg when driving uphill. Often, it is also desirable that the gearshift operation not be performed in situations where a gearshift may have a negative impact on the driving of the vehicle.

Brief description of the invention

An object of the present invention is to provide a method and system which improves the control of change in gear ratio, especially in situations where a change in gear ratio may affect the driving of the vehicle, e.g. by reducing the ability of a vehicle to handle an uphill section of the road. This object is achieved by a method according to claim 1.

• - Erfassen einer reduzierten Haftung mindestens eines Antriebsrads des Fahrzeugs,
• - Bestimmen, ob das Betätigen der vom Fahrer betätigbaren Einrichtung zum Anfordern von Energie durch den Fahrer auf eine reduzierte Haftung hinweist, und
• - Beeinflussen eines Vorgangs der Änderung des Übersetzungsverhältnisses in dem Getriebe, wenn das Betätigen der vom Fahrer betätigbaren Einrichtung zum Anfordern von Energie durch den Fahrer auf eine reduzierte Haftung hinweist.

According to the present invention there is provided a method of controlling the change in gear ratio in a transmission of a vehicle, the transmission being for transmitting energy from a power source to at least one drive wheel of the vehicle, the transmission including a plurality of selectable gear ratios the transmission ratio change is controlled by a vehicle control system, the vehicle further comprising driver-operable means for requesting energy from the energy source, the method comprising the steps of:

• Detecting a reduced adhesion of at least one drive wheel of the vehicle,
• Determining whether actuation of the driver-operable means for requesting energy by the driver indicates reduced adhesion, and
• Influencing an operation of changing the gear ratio in the transmission when the operation of the driver-operable means for requesting energy by the driver indicates reduced adhesion.

In vehicles in general, transmissions of the type used in the past in manual transmission vehicles, but in which gearshifting is automatic via the vehicle control system, are frequently used. This is for example Such transmissions are commonly provided to include a discrete number of different gear ratios (gears), with gear ratios of heavy vehicle gearboxes often being distributed such that one or more of the lowest gear ratios (highest gears ) are capable of driving the vehicle at a constant speed when the vehicle is traveling on substantially level terrain.

When such vehicles are driving uphill, at least at heavy load, gear shifting to a higher gear ratio (lower gear) is often required to provide sufficient energy to properly cope with the uphill section of the road in the desired manner. In particular, when driving uphill, there is often a minimum gear ratio, below which the vehicle loses speed due to lack of drive energy. This involves demands on the way the gears are chosen when a gearshift operation is to be performed.

If a gear shift operation is not performed at least to the highest gear (the lowest gear ratio) at which this criterion is satisfied, the vehicle is further decelerated. There are strategies for making such a gear selection to avoid situations in which the vehicle is losing too much speed, and the gear shift operation is often performed when one or more criteria are met. For example, a gear shift to a lower gear (higher gear ratio) may be provided so as to be performed when it is determined that the engine speed after the gear shift does not exceed a predetermined calibrated speed limit which may not be exceeded.

However, there are situations that can make a gear shift difficult. In particular, the present invention relates to situations in which it is detected that at least one drive wheel of the vehicle has reduced adhesion, i. the friction between at least one drive wheel (tire) and the surface on which the vehicle is traveling may not be sufficient to transmit the force required to drive the vehicle. The reduced adhesion may e.g. on slippery conditions, such as Be attributed to snow, ice and / or rolled split. Detection of reduced adhesion may be accomplished, for example, by sensing the speed of the vehicle drive wheels, and when one or more wheels begin to rotate at speeds that exceed the speeds of non-driven wheels of the vehicle or other drive wheels by more than a predetermined amount or by turning, it can be determined that the adhesion is reduced and one or more wheels slip.

Gear shifting in such situations, particularly when the vehicle is driving uphill, may adversely affect the ability of the vehicle to actually cope with the uphill section of the road. For example, when a gearshift is performed, when one or more drive wheels spin, or when the drive wheels of the vehicle hardly have enough adhesion, the interruption of the drive force applied to the drive wheels during gearshift and the associated increase in drive force after gearshifting can often lead to the liability is completely lost. This may cause the vehicle to lose speed and may require further gear shifts, which may ultimately result in the vehicle resting on an uphill section of the slippery road.

For this reason, a gear shift may be suspended, i. will not be allowed if a wheel slip is detected and one or more wheels spin to reduce the risk of such situations. On the other hand, when the wheel slip is no longer detected, the gear shifts are again controlled according to the general criteria prevailing before the wheel spin detection. However, it has been found that the mere fact that the driving wheels of the vehicle are no longer spinning may not be sufficient to ensure that slippery conditions no longer prevail and thus situations of the above type may still occur. Even if the gearshift operation is suspended as soon as a wheel slip is detected, gear shifts may be suspended in situations where the reduction of the grip is very transient and the gearshift operation suspended is in fact unfounded.

According to the present invention, the processes of changing the transmission ratio can be influenced in situations in which a reduced adhesion of at least one driving wheel is detected, but only as a function of the actual conditions prevailing.

According to the invention, when a reduced grip is detected and this detection may include a step of detecting the wheel slip of at least one drive wheel of the vehicle, it is not sufficient to suspend or otherwise influence a gear shift operation. Instead, it is also determined according to the invention whether the actuation of the driver-operable means for requesting energy by the driver also indicates reduced liability. That is, driver behavior is taken into account to determine whether the detected wheel slip can be considered transient and no further action is required, or whether it is likely that slippery conditions are still likely to prevail. Thus, if the driver-operable device for requesting energy by the driver also operates at a reduced level Liability, the changes in the gear ratio are affected.

According to the invention, the processes of changing the gear ratio are only affected when the actuation of the driver-operable means for requesting energy by the driver has indicated a reduced liability. That is, it may be determined from the manner in which the driver actuates the driver operable energy requesting device whether the driving conditions can be considered to be actually slippery and that a gearshift operation should be affected accordingly. If, for example, a wheel slip is detected and the driver reduces in this context, e.g. simultaneously or after, the request for drive energy, e.g. by at least partially releasing an accelerator pedal, this can be used as confirmation that the conditions are still slippery and that gearshifting should be avoided as much as possible. At a minimum, in such situations, shifting to a higher gear (lower gear ratio) should be avoided since, e.g. a possible loss of speed of the vehicle due to the slippery conditions may substantially immediately necessitate a further gear shift to a lower gear, wherein the process of changing the gear ratio only results in reducing the ability of the vehicle to handle the uphill road section.

With respect to actuating the driver requesting power, the step of determining whether the driver's actuatable driver-requesting means for energizing the driver indicates reduced adhesion may not only comprise the step of detecting a request to reduce the energy from the energy source.

Instead, it may also be determined, e.g. a manner in which the demand for energy follows a pattern, such as e.g. the driver first needs to request energy from the power source, e.g. quickly, reduced, followed by a comparatively slower increase in the demand for energy, as can be interpreted as actuation of the driver operable device for requesting energy by the driver in order to achieve the highest possible tractive effort. According to the embodiments of the invention, it is determined whether, after detecting a decrease in the requested energy from the power source, an increase in requested energy from the power source to a request for less energy than prior to the decrease in the requested energy is detected If the processes of change of the transmission ratio are influenced according to the invention.

According to the invention, processes of changing the gear ratio may be provided so as to be influenced for at least a predetermined period of time, from the time when a reduced adhesion of the at least one driving wheel is no longer detected, or from the time when the actuation the driver-operable device indicates slippery conditions by the driver. That is, the gearshift operation may be provided to be affected for at least a suitable period of time to avoid situations in which the vehicle is again losing adhesion when the gearshift operation is prematurely approved after detection of reduced adhesion.

The step of influencing the gear change ratio operations may also be arranged to terminate when the driver's activation of the means for requesting energy no longer indicates reduced adhesion, such when the driver requests high energy from the power source, which can be taken as an indication that the driver is no longer feeling slippery.

Moreover, according to the embodiments of the invention, it is not required that the wheel slip be detected, while the simultaneous operation of the means for requesting energy by the driver from the power source also indicates slippery conditions. Instead, it may be determined whether the actuation of the means for requesting energy by the driver within a predetermined time period before and / or after the beginning and / or end of the wheel spin operation indicates slippery conditions, and if so, the gear shift operation according to the invention be provided so that it is affected as soon as such a notice is detected.

In addition, the driver-operable means for requesting energy from the power source may be e.g. an accelerator pedal or other driver-operable device, such as a lever or knob for regulating the energy supplied by the vehicle's power source. In turn, the energy source may include an internal combustion engine, one or more electrical machines, or a combination thereof.

The gearshift operation can be influenced in various ways. For example, changing the gear ratio delayed or suspended. In addition, the change of the gear ratio can be delayed or suspended in a lower gear ratio, while according to the embodiments of the invention, the change of the gear ratio can still be done uninfluenced in a higher gear ratio, ie only a change of the gear ratio in a lower gear ratio is delayed or suspended.

The gearshift may be delayed, for example, by changing the dependence of the speed of the power source during gearshifting, so that the driving of a current gear can be maintained for longer periods of time by allowing the engine to operate at higher speeds before going into a higher gear (lower gear ratio) or by allowing the engine to reach lower speeds before shifting to a lower gear (higher gear ratio) than the restrictions prevailing at the beginning of the gear shift according to the invention. For example, the vehicle may be forced to sustain driving of a current gear, as long as the speed of the power source does not fall below a minimum speed limit. The gear shift can also be prevented altogether, as long as a continued driving at a current gear is possible.

According to embodiments of the invention, it is also necessary for the driver to perform at least one more action. For example, it may be necessary for the driver to change the load on the drive shaft, e.g. to increase the pressure of the drive shaft and thus improve the adhesion. In addition or alternatively, it may be necessary for the driver to be e.g. a differential locks, indicating that there are actually slippery conditions.

Further features of the embodiments of the present invention and their advantages are given in the detailed description of the exemplary embodiments listed below and the accompanying drawings.

list of figures

• 1A shows a powertrain of an exemplary vehicle;
• 1B shows an example of a control unit in a vehicle control system;
• 2 shows an exemplary method according to an embodiment of the present invention;
• 3 shows an example of influencing the change in the gear ratio.

Detailed Description of the Exemplary Embodiments

1A schematically illustrates a powertrain of an exemplary vehicle 100 The powertrain includes an energy source, in the present example an internal combustion engine 101 in the conventional manner via an output shaft of the internal combustion engine 101 usually via a flywheel 102 , via a clutch 106 with a gear 103 connected is. An output shaft 107 from the transmission 103 drives drive wheels 113 . 114 via a final drive 108 , such as a common differential, and drive axles 104 . 105 that with the final drive 108 connected to.

The internal combustion engine 101 is from the vehicle control system via a control unit 115 controlled. The coupling 106 and the gearbox 103 are also from the vehicle control system via a control unit 116 controlled.

The gear 103 can be set to a plurality of different (discrete) gear ratios, wherein the vehicle control system for each driving situation, a suitable gear ratio is selected.

In general, a gearshift operation is performed when the engine speed 101 reaches a speed at which the conditions for a gear shift are met. When shifting to a lower gear (higher gear ratio), a condition for performing a gearshift operation may be that the engine speed after a completed gearshift operation must not exceed a certain engine speed limit, which is often a calibrated maximum engine speed which must not be exceeded. This maximum calibrated engine speed may be different for different gears and / or vehicle speeds. As a result, a gear shift to a lower gear is generally performed as soon as it is determined that the rotational speed of the engine in the new gear does not exceed this rotational speed limit. Alternatively or additionally, the speed limits for the speed of a current gear can be set.

As discussed above, there are situations in which the gear shift only after such Criteria may have negative effects on the driving of the vehicle, and embodiments of the invention provide a method for controlling the change in the gear ratio in a way that can facilitate, for example, a vehicle managing an uphill road section when the adhesion between the vehicle drive wheels and the Surface on which the vehicle drives, is reduced.

An exemplary procedure 200 According to embodiments of the present invention, at least partially, for example, in the control unit 116 for controlling the clutch 106 and the transmission 103 can be implemented is in 2 shown. As noted above, the functions of a vehicle are generally controlled by a number of control units, and control systems in vehicles of the type disclosed generally include a communication bus system having one or more communication buses for connecting a series of electronic control units (ECU) or controllers to various components Board the vehicle. Such a control system may include a large number of control units, and the control of a particular function may be divided into two or more thereof.

For simplicity's sake 1A only the control units 115 - 116 but vehicles 100 The type shown are often equipped with significantly more control units, as the skilled person will understand. The control units 115 - 116 are provided to communicate with each other and with various components in the communication bus system and other lines 1 partially characterized by connecting lines A.

Embodiments of the present invention may be used in any suitable control unit in the vehicle 100 be implemented and not necessarily in the control unit 115 be implemented. The control of the transmission 103 In accordance with embodiments of the present invention, it is generally conditional upon receiving signals from other controllers and / or vehicle components, and it is generally the case that disclosed type controllers are typically configured to receive sensor signals from various parts of the vehicle 100 to recieve. The control unit 116 For example, it receives signals from the engine control unit 115 where these signals may include signals related to engine operation as well as driver demand for energy and, thus, operator depression of, for example, an accelerator pedal. The control unit 116 also supplies signals to the control unit 115 For example, to control the engine speed and delivered energy during gearshifting. The control unit 116 It also receives signals, eg from one or more other controllers related to detected wheel slip. Control units of the type shown are also usually designed to provide control signals to various parts and components of the vehicle, eg for controlling the clutch 106 and the transmission 103 ,

Such control is often performed by programmed instructions. The programmed instructions typically include a computer program that, when executed in a computer or control unit, causes the computer / controller to perform the desired control, such as method steps, in accordance with embodiments of the present invention. The computer program is typically part of a computer program product, the computer program product being a suitable storage medium 121 (please refer 1B) with a in the storage medium 121 stored computer program 126 includes. The computer program can be stored non-volatile in the storage medium. The digital storage medium 121 For example, it may include one of the following group, which includes ROM (Read Only Memory), Programmable Read Only Memory (PROM), Erasable PROM (EPROM), Flash Memory, Electrically Erasable PROM (EEPROM), a hard disk unit, and so on. and may be provided in or in connection with the control unit, whereupon the computer program is executed by the control unit. The behavior of the vehicle in a particular situation can thus be adjusted by changing the instructions of the computer program.

An exemplary control unit (the control unit 116 ) is schematic in 1B illustrated, wherein the control unit is a processing unit 120 For example, it may include any suitable type of processor or microcomputer, such as a Digital Signal Processor (DSP) or Application Specific Integrated Circuit (ASIC) circuit. The processing unit 120 is with a storage unit 121 connected to the processing unit 120 for example, the stored program code 126 and / or the stored data that supplies the processing unit 120 needed to perform calculations. The processing unit 120 It is also intended to provide partial or final results of calculations in the memory unit 121 stores.

In addition, the control unit 112 with devices 122 . 123 . 124 . 125 for receiving and sending input and output signals fitted. These input and output signals may include waveforms, pulses or other attributes that the devices 122 . 125 for receiving input signals as information for processing by the processing unit 120 can capture. The devices 123 . 124 for transmitting output signals are provided to receive calculation results from the processing unit 120 into output signals which are transmitted to other parts of the vehicle control system and / or the component (s) for which the signals are intended. Each of the connections to the devices for receiving and transmitting the respective input and output signals may include one or more cables, a data bus such as a Controller Area Network Bus (CAN), a Media Oriented Systems Transport (MOST) bus, or a different bus configuration or a wireless connection.

Again with reference to the in 2 shown exemplary method 200 the procedure begins in step 201 determining whether reduced grip is detected with respect to one or more vehicle drive wheels, eg, by detecting wheel slippage that may be determined in any suitable manner, eg, by detecting a sudden increase in the wheel speed of one or more drive wheels and / or corresponding increase in the speed of the internal combustion engine.

The method according to the invention may be arranged to be performed whenever reduced adhesion is detected, or e.g. only when the vehicle is traveling on an uphill section of the road, where further criteria such as e.g. Can affect road gradient and / or current vehicle weight, whether the gear shift operation is to be influenced according to the invention or not. For example, a deceleration of the vehicle may be determined if the method according to the invention is provided so that it can only be performed if the vehicle deceleration exceeds a certain deceleration. When the vehicle deceleration is low, the effect of a gearshift operation is less harmful to the driving of the vehicle than when the vehicle deceleration is high, as may be the case when a heavily laden vehicle is driving on an uphill section of the road.

Therefore, the method according to embodiments of the invention may include the further step of determining an instantaneous deceleration of the vehicle 100 wherein the vehicle deceleration may be determined by any suitable means as known in the art. According to these embodiments, if it is determined that the vehicle deceleration exceeds a deceleration limit, the method may be arranged to continue according to the following steps, while otherwise the method may be terminated.

If it is determined that the vehicle 100 a reduced adhesion experiences, for example by wheel slip, the method goes to step 202 in which the liability of the vehicle is further evaluated by determining whether an operator's operation, in this example of the accelerator pedal, also indicates reduced adhesion. This can be determined in various ways, eg, by determining whether the driver, in connection with the detection of eg wheel slip, reduces the demand for energy from the internal combustion engine. In general, when a driver notices reduced grip conditions, a demand for energy from the engine is reduced to restore adhesion. Conversely, it is highly unlikely that the driver will sustain a high energy requirement when the wheels start to spin unless the driver realizes that the reduced liability is very transient and the liability is restored immediately. Therefore, according to embodiments of the invention, a reduction in the demand for energy from the internal combustion engine, for example, detected by detecting a released accelerator pedal, may be used as an indication that the adhesion has actually been reduced and still is.

According to embodiments of the invention, not only is it determined whether the demand for energy from the internal combustion engine is reduced, but it is also determined whether the reduction is followed by an increase in the demand for energy and it can be determined whether the increase is at most an increase eg is a certain percentage of the requirement that prevailed prior to the detection of reduced liability. Such behavior may be taken as an indication that the driver is seeking liability and trying to maximize the force transmitted to the driving wheels of the vehicle as much as possible. According to embodiments of the inventions, it may be determined whether the increase is followed by a further reduction in the demand for energy to determine that the conditions are such that the adhesion is still reduced and the gearshift should be affected.

When in step 202 is determined that the driving of the vehicle undergoes reduced adhesion, the method moves to step 203 continue, in which the gear shift is affected. Otherwise, the method may be provided to step 201 returns. According to Embodiments of the invention affect the operations of changing the gear ratio when the driver's depression of the accelerator pedal indicates reduced adhesion within a first time period from detecting reduced adhesion of the at least one drive wheel. That is, it is not necessary that the accelerator pedal be operated by the driver at the same time as the wheel slip is detected, but the accelerator pedal may be operated by the driver within a period of time from the detection of the wheel slip. For example, a suitable number of seconds may be used as a time limit. In this way, the driver gets time to react when one or more wheels start to skid, and so long as the driver actually responds within a set period of time, the gear shift is affected according to the invention.

Therefore, in step 203 the control of the gearshift, that is, the operations of the gearshift, are influenced as a result of the double reference to reduced adhesion of the vehicle. The gear shifts may be provided so that they can be influenced in various ways. According to embodiments of the invention, any changes in the gear ratio are delayed or suspended. According to embodiments of the invention, changes in the gear ratio may be delayed or suspended into lower gear ratios, while changes in gear ratio to higher gear ratios may still be permissible. When in step 204 determining that slippery conditions are no longer present, for example as indicated by the driver depressing the accelerator pedal or by no further indications of slippery conditions within a predetermined period of time, the influence according to the invention is suspended and the normal control of the gearshift in step 205 resumed and the procedure in step 206 completed.

As discussed above, according to embodiments of the invention, in influencing gear change ratio operations, it may also include changing a criterion with respect to when a gear shift should be performed. This criterion may relate to when a gearshift is performed with respect to the engine speed, wherein a gearshift may be influenced to permit driving to a current gear ratio at higher and / or lower engine speed as compared to in the case when there is no reduced liability. This can e.g. in situations where the vehicle is being decelerated due to insufficient power to drive the vehicle or otherwise the vehicle speed is changing so that normal gearshift criteria would otherwise trigger a change in gear ratio.

This is in 3 shown. 3 shows a situation in which the vehicle 100 is delayed and forced to be driven over a longer period of time than normally with a current gear. The x-axis represents the time and the y-axis the speed n of the internal combustion engine.

The solid line 301 represents the change in the speed n of the internal combustion engine for a situation in which the vehicle 100 in an uphill section, and in a situation where the vehicle loses speed. The dashed line 302 represents a speed limit n _{lim of} the internal combustion engine, which must not be exceeded after a gear shift to a lower gear (ie change of the gear ratio in a higher gear ratio).

Starting from the time t ₀ , in the by the solid line 301 illustrated situation loses the vehicle 100 continuously at speed (deceleration) and thus also the speed n of the internal combustion engine 101 continuously reduced. The requirements of a gearshift in the general case are met at time t ₁ , for example, that the speed of the engine after the gearshift does not exceed the speed limit n _lim and / or reaches a minimum speed n _change . If the gearshift operation according to the present invention is not affected, normally at that time, according to the dashed line 303 , a gear shift be performed. In the inventive influence on operations of changing the transmission ratio of the gear shift operation is not performed, but delayed. This can be achieved, for example, by reducing the maximum permissible rotational speed of the internal combustion engine n _lim after a gearshift to a second rpm _{limit value} n _{lim_slip} , so that the criteria for the gearshift operation at time t _{1 are} no longer met. Alternatively or additionally, the criterion may instead be set so that the vehicle is forced to continue in a current gear until the engine speed n of the engine 101 is reduced to the rotational speed n _{change_slip} , which is lower than the rotational speed of the internal combustion engine n _change at which the gearshift operation is normally performed. In this way, the criteria for carrying out the process of changing the transmission ratio are only met when the vehicle 100 is further delayed and the vehicle 100 thereby being driven for a longer period of time in the current gear.

Consequently, in the situation corresponding to the solid line 301 when the vehicle 100 reached the time t ₁ , no gearshift performed, since the new gearshift criteria are not met due to the detected wheel slip. Instead, the vehicle becomes 100 is controlled so that it continues in the current gear, while the vehicle speed and thus the speed of the engine n can be further reduced and the gearshift operation can thereby be at least delayed. However, the speed of the internal combustion engine in a current gear can sometime, when the vehicle decelerates further, reach a speed at which a gear shift can not be avoided, for example, because the engine speed reaches the minimum allowable speed n _{change_slip} , eg idle speed of Motors is or is located near it. According to the present example, this happens at time t ₂ , which is why a gear shift is performed, but according to the invention with a delay.

In addition, according to embodiments of the invention, the process of changing the gear ratio is only affected if the driver takes at least one further measure, which indicates a reduced liability. Such measures may be, for example, detection that the driver changes the load applied to the wheel shafts, e.g. by reducing the load applied to an auxiliary axle to thereby increase the load applied to the drive wheels to improve the chances of obtaining sufficient grip. The driver may also take other measures, such as locking a differential to increase the ability to negotiate a reduced traction road section. Consequently, the gearshift operation according to embodiments of the invention is only influenced if at least one of these further indications of reduced adhesion is detected.

Finally, embodiments of the invention have been exemplified above for a particular example of a vehicle, but are applicable to any vehicle in which the vehicle control system controls the gear shift operation. The invention also includes a vehicle having a system implementing the invention.

Claims (15)

A method of controlling the change in gear ratio in a transmission (103) of a vehicle (100), wherein the transmission (103) provides for transmitting energy from a power source (101) to at least one drive wheel (113, 114) of the vehicle (100) wherein the transmission (103) comprises a plurality of selectable gear ratios, the change in gear ratio being controlled by a vehicle control system, the vehicle further comprising driver operable means for requesting energy from the power source, the method comprising the steps from: Detecting a reduced adhesion of at least one drive wheel of the vehicle, Determining whether actuation of the driver-operable means for requesting energy by the driver indicates reduced adhesion, and Influencing an operation of changing the gear ratio in the transmission (103) when the operation of the driver-operable means for requesting energy by the driver indicates reduced adhesion. Method according to Claim 1 wherein the step of detecting the reduced adhesion of at least one drive wheel of the vehicle comprises a step of: detecting a wheel slip of at least one drive wheel of the vehicle. Method according to Claim 1 or 2 wherein the step of influencing a gear change ratio operation in the transmission (103) comprises a step of: - delaying or suspending a change in the gear ratio to a lower gear ratio. Method according to one of Claims 1 - 3 wherein the step of influencing the process of changing the gear ratio in the transmission (103) comprises a step of: - delaying or suspending a change in gear ratio. Method according to one of Claims 1 - 4 wherein the step of influencing an operation of Changing the gear ratio in the transmission (103) comprises a step of: changing a gear shift criterion with respect to rotational speeds of the power source and gear ratios of the transmission, so that the driving is allowed at a current gear ratio at higher and / or lower rotational speeds of the power source, Compared to the case when no reduced adhesion of at least one drive wheel is detected. Method according to one of Claims 1 - 5 wherein the step of influencing a gear change ratio operation in the transmission (103) comprises: - influencing an operation of changing the gear ratio in the transmission (103) when the driver-operable means for requesting power by the driver is operated indicates a reduced adhesion within a first time period from the detection of a reduced adhesion of the at least one drive wheel. Method according to one of Claims 1 - 6 wherein the step of influencing a gear ratio change operation in the transmission (103) comprises: - influencing the gear ratio change operation for at least a second time period from when a reduced adhesion of the at least one drive wheel is no longer detected. Method according to one of Claims 1 - 6 comprising the step of: terminating the step of influencing the process of changing the gear ratio when the actuation of the means for requesting energy by the driver no longer indicates reduced adhesion. Method according to one of Claims 1 - 8th wherein the step of determining whether the driver activating the driver-operable means for requesting energy by the driver indicates reduced adhesion comprises a step of: - detecting a request to reduce the energy from the energy source. Method according to one of Claims 1 - 9 wherein the step of determining whether the driver actuating the driver-operable energy requesting device is indicative of reduced adhesion comprises the steps of: detecting a decrease in the requested energy from the energy source and detecting an increase in the requested one Energy from the energy source is requested on a request for less energy than prior to the acceptance of the requested energy. Method according to one of Claims 1 - 9 comprising, prior to the step of affecting a process of changing the gear ratio in the transmission (103), a step of: - detecting at least one further action taken by the driver indicative of reduced adhesion. A computer program with a program code that allows the computer, if the program code is executed in a computer, the method of any one of the preceding Claims 1 - 11 perform. A computer program product comprising a computer readable medium and a computer program Claim 12 wherein the computer program is contained in the computer readable medium. A system for controlling the change in gear ratio in a transmission (103) of a vehicle (100), the transmission (103) for transmitting energy from a power source (101) to at least one drive wheel (113, 114) of the vehicle (100) wherein the transmission (103) comprises a plurality of selectable gear ratios, the change in gear ratio being controlled by a vehicle control system, the vehicle further comprising a driver actuated means for requesting energy from the power source, the system being characterized in that it comprises: - a device adapted to detect a reduced adhesion of at least one driving wheel of the vehicle, - a device adapted to determine whether the actuation of the driver-operable device is to request energy the driver points to a reduced liability, and - a device, ie e is adapted to influence a process of changing the gear ratio when the actuation of the driver-operable means for requesting energy by the driver indicates a reduced liability. Vehicle, characterized in that it is a system according to Claim 14 includes.

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