SE540468C2

SE540468C2 - Control of a transmission including an oil pump

Info

Publication number: SE540468C2
Application number: SE1551514A
Authority: SE
Inventors: Selling Tomas
Original assignee: Scania Cv Ab
Priority date: 2015-11-23
Filing date: 2015-11-23
Publication date: 2018-09-18
Also published as: SE1551514A1; DE102016013574A1

Abstract

A system (70) for controlling a vehicle transmission (2) compring a gearbox (4) and a clutch (7) is provided. The gearbox comprises a forward gear (23-25), a reverse gear (26), and an oil pump (60) arranged to provide lubrication for the gearbox and to be driven by an oil pump driving means (12) rotating in a normal operation direction. The oil pump driving means is arranged at, or upstream of, the reverse gear. The system comprises means (72) configured to determine if the oil pump driving means rotates in a direction opposite to the normal operation direction, and means (73) configured to, if the oil pump driving means rotates in the direction opposite to the normal operation direction, initiate maneuvering of the gearbox into neutral and then initiate changing of the rotational direction of the oil pump driving means to the normal operation direction. By this control strategy, the length of interruptions in the oil pump operation is reduced, whereby the risk of wear and damage of the gearbox is reduced.

Description

CONTROL OF A TRANSMISSION COMPRISING AN OIL PUMP Field of the invention The present invention generally relates to the field of controlling vehicle transmissions. In particular, the present invention relates to the field of controlling vehicle transmissions comprising a gearbox having an oil pump for providing lubrication of the gearbox.

Background of the invention Vehicle gearboxes need lubrication in order to reduce wear and damage and to provide a satisfying life time of the gearbox. For providing such lubrication an oil pump may be provided, which e.g. may be arranged to feed oil via conduits in one or more shafts of the gearbox towards gear wheels of the gearbox. Such oil pumps may be driven by an oil pump driving means including one of the shafts or one of the gear wheels of the gearbox. For example, the oil pump driving means may include a lay shaft or an intermediate gear wheel of a reverse gear of the gearbox in order for the oil pump to be located at a low position in the gearbox close to the oil level, which reduces the suction height for the oil pump. Thus, the oil pump driving means is normally arranged at, or upstream of, the reverse gear as seen in a direction of a torque transmission path extending from the engine towards a propeller shaft of the vehicle.

In order for the oil pump to be operated properly, the oil pump driving means must rotate in a certain direction, which is obtained when the vehicle moves forwards and a forward gear of the gearbox is engaged, as well as when the vehicle moves backwards and the reverse gear is engaged. When the oil pump driving means rotates in a direction opposite to that certain rotational direction, the oil pump is not operated and the lubrication of the gearbox is interrupted, which may cause wear and/or damage of the gearbox. Under certain circumstances, damage may occur already after a few seconds of interruption in the lubricant supply.

An example of a situation when the oil pump driving means rotates in such an opposite direction is when the vehicle has been reversing (that is, a reverse gear of the gearbox is engaged), uphill in a slope and then starts to travel forward, downhill in the slope, still having the reverse gear engaged and the clutch open. As the oil pump driving means is arranged at, or upstream of, the reverse gear, the engaged reverse gear will reverse the rotational direction of the oil pump driving means as the vehicle travels forwards. This will result in the oil pump not being operated and the lubrication of the gearbox being interrupted. If the slope is long, such as in mines, the length of the interruption may significantly increase the risk of wear and damage of the gearbox. A similar situation occurs when the vehicle travels backwards, downhill in a slope having the forward gear engaged (and the clutch open).

WO 2014/008902 A1 shows a gearbox comprising an oil pump driven by a lay shaft of the gearbox. A freewheel mechanism is provided in order to enable operation of the oil pump independent of the rotational direction of the lay shaft. A drawback with such a solution is that it requires several additional mechanical components in order to realise the freewheel mechanism, thereby rendering the gearbox design more complex.

Summary of the invention It would be advantageous to achieve a method and a system for controlling a transmission overcoming, or at least alleviating, the above mentioned drawbacks. In particular, it would be desirable to enable a method and a system for controlling a transmission that reduce the risk of wear and damage of a gearbox of the transmission. It would also be desirable to enable a less complex gearbox design.

To better address one or more of these concerns, a method of controlling a transmission and a system for controlling a transmission having the features defined in the independent claims are provided. Preferable embodiments are defined in the dependent claims.

Hence, according to a first aspect, a method of controlling a transmission of a vehicle is provided. The transmission comprises a gearbox. The gearbox comprises at least one forward gear, at least one reverse gear, and an oil pump arranged to provide lubrication for the gearbox and to be driven by an oil pump driving means when that oil pump driving means rotates in a normal operation direction. The oil pump driving means includes a shaft or a gear wheel of the gearbox and is arranged at, or upstream of, the reverse gear as seen in a direction of a main torque transmission path extending from an engine of the vehicle towards a propeller shaft of the vehicle. The method comprises determining if the oil pump driving means rotates in a direction opposite to the normal operation direction, and, if the oil pump driving means rotates in the direction opposite to the normal operation direction, initiating maneuvering of the gearbox into neutral and then initiating change of the rotational direction of the oil pump driving means to the normal operation direction.

According to a second aspect, a system for controlling a transmission of a vehicle is provided. The transmission comprises a gearbox. The gearbox comprises at least one forward gear, at least one reverse gear, and an oil pump arranged to provide lubrication for the gearbox and to be driven by an oil pump driving means when that oil pump driving means rotates in a normal operation direction. The oil pump driving means includes a shaft or a gear wheel of the gearbox and is arranged at, or upstream of, the reverse gear as seen in a direction of a main torque transmission path extending from an engine of the vehicle towards a propeller shaft of the vehicle. The system comprises means configured to determine if the oil pump driving means rotates in a direction opposite to the normal operation direction, and means configured to, if the oil pump driving means rotates in the direction opposite to the normal operation direction, initiate maneuvering of the gearbox into neutral and then initiate change of the rotational direction of the oil pump driving means to the normal operation direction.

In a situation as described in the background section of the present specification (when the vehicle travels forwards, downhill in a slope with the reverse gear engaged, or when the vehicle travels backwards, downhill in a slope with the forward gear engaged), the input shaft of the gearbox is caused to rotate in a direction opposite to the rotational direction of the engine and a clutch (or any corresponding means for adjusting the amount of torque acting on the input shaft) will not be able to close. With the present aspects, the gearbox is manoeuvred into neutral in such situations (that is, situations causing the oil pump driving means to rotate in the wrong direction). When the gearbox is manoeuvred into neutral, torque from the wheels is no longer transferred to the input shaft. The rotational direction of the input shaft can then be changed (that is, turned around) by the engine, whereby the rotational direction of the oil pump driving means is also changed to the normal operation direction. Turning around the rotational direction of the input shaft may be made by adjusting the amount of torque acting on the input shaft of the gearbox. Hence, the engine will turn the rotational direction of the oil pump driving means around to the normal operation direction again, whereby the oil pump will operate properly.

Hence, by the control strategy according to the present aspects, the length of interruptions in the oil pump operation (and thus, in the lubricant feed) is reduced, whereby the risk of wear and damage of the gearbox is reduced. Further, additional mechanical components may not be required, thereby enabling a less complex gearbox design compared to prior art.

Conventionally, an over speed protection may be provided for maneuvering the gearbox into neutral in case the speed of a clutch disk of a clutch of the transmission exceeds a certain threshold, such as around 2500 rpm.

However, in case the vehicle travels according to the situation identified above (that is, forwards, downhill in a slope with the reverse gear engaged, or backwards, downhill in a slope with the forward gear engaged with the clutch open), the speed of the clutch disk may not necessarily exceed such a threshold, but may continue to travel down the slope without the over speed protection being activated. With the present aspects, the gearbox may be maneuvered into neutral in any situation causing the oil pump driving means to rotate in the wrong direction irrespective of the over speed protection.

In the present specification, the term ”gear” may include a gear wheel or a set of gear wheels together obtaining a certain gear ratio when engaged. For example, the reverse gear may include one gear wheel on a main shaft of the gearbox, one gear wheel on a lay shaft of the gearbox and one intermediate gear wheel arranged between the other two gear wheels in order to reverse the rotational direction upon transmission by the intermediate gear wheel. Alternatively, the reverse gear may be included in a planetary gear (such as a range gear) arranged on the main shaft, wherein the reverse gear is engaged upon operation of one or more engagement sleeves, whereby the rotational direction is reversed when transmitted by the planetary gear. Such reverse gear incorporated in a range gear is described in more detail in PCT/SE15/050526, which is hereby incorporated by reference. Further, the forward gear may e.g. comprise one gear wheel on the main shaft and one gear wheel on the lay shaft arranged so as to transfer torque there between.

Further, in the present specification, the expression “a shaft or gear wheel arranged at, or upstream of, the reverse gear” may include any shaft or gear wheel of the gearbox arranged such that its rotational direction is able to be reversed compared to the rotational direction of an output shaft of the gearbox when the reverse gear is engaged. That is, any shaft or gear wheel of the gearbox arranged such that its rotational direction is the same in both the situation when the vehicle travels forward with the forward gear engaged and when the vehicle travels backward with the reverse gear engaged. For example, in the case the reverse gear includes one gear wheel on the main shaft, one gear wheel on the lay shaft and one intermediate gear wheel, any shaft or gear wheel arranged upstream of the intermediate gear wheel (such as the lay shaft or the input shaft, but not the main shaft) as well as the intermediate gearwheel itself may be included in that expression. Further, in case the reverse gear is included in a range gear of the gearbox, any shaft or gear wheel arranged upstream of the range gear (such as the lay shaft, the input shaft or the main shaft, but not the output shaft of the gearbox) may be included in that expression. Accordingly, a shaft or gear wheel arranged downstream of the reverse gear may include any shaft or gear wheel of the gearbox arranged to have the same rotational direction as the output shaft of the gearbox irrespective of if the reverse gear is engaged or not.

Changing the rotational direction of the oil pump driving means may be made by controlling any means provided in the vehicle for adjusting the amount of torque acting on the input shaft of the gearbox. According to an embodiment, the transmission may comprise a clutch, wherein changing of the rotational direction of the oil pump driving means may be made by closing the clutch, whereby torque from the engine is transferred to the input shaft. Alternatively, the transmission may comprise a planetary gear coupled to an electric motor for adjusting the amount of torque transfer between the output shaft of the engine and the input shaft of the gearbox, wherein changing the rotational direction of the oil pump driving means may be made by controlling the speed of the electric motor so as to provide transfer of torque from the engine to the input shaft of the gearbox. Such transmissions may be comprised in hybrid vehicles and are described in more detail in WO 2015099591 A1 and WO 2015099594 A1, which are hereby incorporated by reference.

The determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction may be realised in several different ways, which will be described in the following.

According to an embodiment, the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction may comprise determining if the vehicle moves forwards, and determining if the reverse gear is engaged. The manoeuvring of the gearbox into neutral (and later on, the changing of the rotational direction of the oil pump driving means around) may be initiated if it is determined that the vehicle moves forwards and the reverse gear is engaged. With the present embodiment, situations may be detected when the vehicle travels forwards, downhill in a slope with the reverse gear engaged, which is a situation occurring relatively frequently e.g. in the mining industries. A truck may typically reverse upwards in a slope in the mine in order to tip a load on a specific location. When the tipping operation is accomplished and the truck is to travel downhill again, it happens that the driver forgets to disengage the reverse gear (e.g. by selecting a forward gear or neutral) when letting go of the brakes, which will result in the truck travelling forwards with the reverse gear engaged. Similar situations may occur for any vehicle travelling in a hilly terrain.

According to an embodiment (which optionally may be combined with the previously described embodiment), the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction may comprise determining if the vehicle moves backwards, and determining if the forward gear is engaged. The manoeuvring of the gearbox into neutral (and later on, the changing of the rotational direction of the oil pump driving means around) may be initiated if it is determined that the vehicle moves backwards and the forward gear is engaged. With the present embodiment, situations may be detected when the vehicle travels backwards, downhill in a slope with the forward gear engaged.

Any forward or backward movement of the vehicle may be detected in any suitable manner, such as by means of any sensing means able to detect the travelling direction of the vehicle or by GPS (global positioning system).

According to an example, the determining of if the vehicle moves forwards and/or the determining of if the vehicle moves backwards may comprise receiving information of a detected rotational direction of a shaft or gear wheel of the gearbox arranged downstream of the reverse gear (such as a main shaft and/or an output shaft of the gearbox), which shaft or gear wheel directly indicates the travel direction of the vehicle. Alternatively (or as a complement) information of a detected rotational direction of a shaft or gear wheel of the gearbox arranged at, or upstream of, the reverse gear (such as an input shaft, a lay shaft or an intermediate gear wheel of the reverse gear of the gearbox) as well as information of a detection of which gear of the gearbox is engaged may be received, which information together indicate the travel direction of the vehicle.

According to an embodiment, the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction may comprise receiving information of a detected rotational direction of a shaft or gear wheel of the gearbox arranged at, or upstream of, the reverse gear, such as of a detected rotational speed of the oil pump driving means itself. Any such shaft or gear wheel of the gearbox is arranged at the same side of the reverse gear as the oil pump driving means and may therefore rotate in the same direction as the oil pump driving means.

Alternatively (or as a complement), the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction may comprise receiving information of a detected rotational direction of a shaft or gear wheel of the gearbox arranged downstream of the reverse gear, and receiving information of a detection of which gear of the gearbox is engaged. Since such shaft or gear wheel of the gearbox is arranged at the opposite side of the reverse gear as the oil pump driving means, the information of the detected rotational direction may be complemented with information related to which gear (forward or reverse) is currently engaged in order to be able to determine the rotational direction of the oil pump driving means.

The determining of the rotational direction of the oil pump driving means may then be based on the received information. If the information indicates a negative rotational direction (corresponding to the direction opposite to the normal operation direction), the manoeuvring of the gearbox into neutral may be initiated.

The detection of the rotational directions according to the previously described embodiments may e.g. be made by one or more sensors arranged to detect the rotational direction (and optionally the rotational speed) of the shaft or gear wheel in question. Such sensors for detecting rotational directions of the shafts and/or gear wheels of the gearbox may be used for several other purposes. Thus, according to the previously described embodiments, the determination of the rotational direction of the oil pump driving means may be performed with existing hardware equipment, thereby rendering the gearbox design less complex.

According to embodiments, the system according to the second aspect may comprise means configured to receive any of the information referred to in the previously described embodiments.

According to an embodiment, the initiating of the manoeuvring of the gearbox into neutral may be made a certain time after it has been determined that the oil pump driving means rotates in the direction opposite to the normal operation direction, such as after a predetermined time period or after a predetermined number of rotations of at least one of: the oil pump driving means, an input shaft, a main shaft and a lay shaft of the gearbox. Hence, the oil pump driving means may be allowed to rotate in the wrong direction for a certain time before the manoeuvring of the gearbox into neutral is initiated. This embodiment is advantageous for enabling the vehicle to start in an uphill slope. The forward gear may then be engaged while the vehicle moves slightly backwards before taking off in a forward direction. The delay in the initiation of the manoeuvring of the gearbox into neutral may be adapted such that the risk of damaging the gearbox due to lack of lubrication is kept low. Under certain circumstances, damage due to lack of lubrication may occur already after around 3 seconds. For example, the delay may be around a few seconds, such as around 2-5 seconds.

According to an embodiment, the oil pump driving means may be one in the group of: a lay shaft, an input shaft, a main shaft and an intermediate gear wheel of the reverse gear of the gearbox. In particular, if the gearbox comprises a conventional reverse gear, that is, a reverse gear comprising one gear wheel on the main shaft, one gear wheel on the lay shaft and one intermediate gear wheel arranged between the other two gear wheels, the oil pump driving means may be the lay shaft, the input shaft or the intermediate gear wheel of the reverse gear. In such a gearbox, the lay shaft and the input shaft are arranged upstream of the reverse gear, and the intermediate gear wheel is arranged at the reverse gear, and will thereby rotate in the same direction irrespective of if the vehicle travels forward with the forward gear engaged, or the vehicle travels backwards with the reverse gear engaged, thereby facilitating operation of the oil pump, which requires a certain rotational direction. Alternatively, if the gearbox comprises a reverse gear incorporated in the range gear, the oil pump driving means may be the main shaft, lay shaft or input shaft since all these three shafts will be located upstream of the reverse gear in the range gear and will thereby rotate in the same direction irrespective of if the vehicle travels forward with the forward gear engaged, or the vehicle travels backwards with the reverse gear engaged.

According to an embodiment, the oil pump may be designed so as to not be operated when the oil pump driving means rotates in the direction opposite to the normal operation direction. Thus, the oil pump may have a design enabling it to be operated only when the oil pump driving means rotate in the normal operation direction. This enables a less complex oil pump arrangement since the oil pump need only be operable for a single rotational direction. In case the oil pump driving means rotates in the other direction, the gearbox is manoeuvred into neutral such that the rotational direction can be turned back no normal again, as described above.

According to an embodiment, the normal operation direction of the oil pump driving means may be obtained when the vehicle moves forwards and the forward gear is engaged, and when the vehicle moves backwards and the reverse gear is engaged, respectively. This will be the case when the oil pump driving means is arranged at, or upstream of, the reverse gear.

According to an embodiment, the gearbox may be an automated manual transmission gearbox (AMT) and/or a dual clutch transmission gearbox (DCT).

According to an embodiment, a computer program is provided that, when run on a processor, enables the processor to carry out the method as defined in any one of the preceding embodiments.

According to an embodiment, a computer program product is provided. The computer program product comprises a computer readable medium on which a computer program according to the previously described embodiment is stored.

According to an embodiment, a vehicle is provided comprising a system as defined according to the second aspect.

According to an embodiment, the gearbox may comprise a discrete number of distinct gear ratios (that is, a finite number of gear ratios) in contrast to continuously variable transmissions.

It is noted that embodiments of the invention relates to all possible combinations of features recited in the claims. Further, it will be appreciated that the various embodiments described for the method are all combinable with the system as defined in accordance with the second aspect of the present invention.

Brief description of the drawings These and other aspects will now be described in more detail in the following illustrative and non-limiting detailed description of embodiments, with reference to the appended drawings.

Figure 1 shows a vehicle according to an embodiment.

Figure 2 shows a transmission of the vehicle according to an embodiment.

Figure 3 shows a first driving situation of the vehicle.

Figure 4 shows a second driving situation of the vehicle.

Figure 5 illustrates a method of controlling a transmission according to an embodiment.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted. Like reference numerals refer to like elements throughout the description.

Detailed description of embodiments A vehicle 1 according to an embodiment will be described with reference to Figure 1. The vehicle 1 may e.g. be a heavy vehicle, such as a truck, or any other type of vehicle. The vehicle 1 may comprise an engine 3, a transmission 2 arranged to transmit torque from the engine 3 towards driving wheels 6 via a propeller shaft of the vehicle 1. The transmission 2 may comprise a gearbox 4. The transmission 2 may further comprise means for adjusting transfer of torque between the engine 3 and the gearbox 4, such as a clutch (not shown in Figure 1). Alternatively, such means may comprise a planetary gear coupled to an electric motor that can be controlled so as to adjust the amount of torque transferred from an output shaft of the engine to an input shaft of the gearbox (e.g. if the vehicle is a hybrid vehicle). It will be appreciated that any other kind of means for adjusting the transfer of torque between the output shaft of the engine 3 and the gearbox 4 may be envisaged.

A torque transmission path extends in direction from the engine 3 via the transmission 2 and the propeller shaft 5 to the driving wheels 6.

Figure 2 schematically illustrates the transmission 2 of the vehicle 1 in more detail and a system 70 of the vehicle for controlling the transmission 2. In the present example, the transmission 2 comprises a clutch 7 connected to the engine via a shaft 8, and to an input shaft 10 of the gearbox 4. The gearbox 4 may further comprise a main shaft 14, a lay shaft 12 and one or more forward gears 23-25, each one arranged to, when engaged, cause the vehicle 1 to be propelled in a forward direction. One or more of the forward gears 23-25 may comprise one gear wheel 28 arranged on the main shaft 14 and one gear wheel 27 arranged on the lay shaft 12 so as to enable transfer of torque there between. The gearbox 4 may further comprise at least one reverse gear 26 arranged to, when engaged, cause the vehicle 1 to be propelled in a backward direction. For example, the reverse gear 26 may comprise one gear wheel 29 arranged on the main shaft 14, one gearwheel 31 arranged on the lay shaft 12 and one intermediate gear wheel 30 arranged between the other two gear wheels 29, 31 of the reverse gear 26.

It will be appreciated that the gear wheels illustrated in Figure 2 are merely schematically depicted with similar sizes for illustrating the principles of the gearbox 4 and they are not drawn to scale. In reality, the gear wheels may be dimensioned in different ways so as to achieve the desired gear ratios.

One or more coupling sleeves 41 may be arranged for enabling engagement of the gears 21-26. In case none of the gears 21-26, 18 of the gearbox is engaged, the gearbox 4 is in neutral and no torque is transmitted between the engine and the output shaft 15. Coupling sleeves as such, and how to operate them in order to engage a particular gear is known to the skilled person and will therefore not be described in more detailed herein.

Optionally, a split gear 16 may be comprised in the gearbox 4. Further, the gearbox 4 may optionally comprise a range gear 18, which may be a planetary gear. The range gear 18 may comprise a sun gear wheel 47, planet gear wheels 46 and a ring gear wheel 45. The range gear 18 may be connected to an output shaft 15 of the gearbox 4. Split gears and range gears as such are known to the skilled person and will therefore not be described in more detail herein. According to an example (not shown), the reverse gear may be incorporated in the range gear.

The gearbox 4 may further comprise an oil pump 60 arranged to provide lubrication for the gearbox 4. For example, lubricant may be fed by the oil pump 60 via conduits in one or more of the shafts 10, 12, 14 (not shown) to one or more of the gear wheels of the gearbox 4. The oil pump 60 may be driven by an oil pump driving means arranged at, or upstream of, the reverse gear 26 as seen in the direction of the torque transmission path. In the present example, the oil pump driving means is constituted by the lay shaft 12. Other possible oil pump driving means are the input shaft 10 or the intermediate gear wheel 30 of the reverse gear 26 since these are arranged at, or upstream of, the reverse gear 26. In case the reverse gear is incorporated in the range gear, the oil pump driving means may be constituted by any one of the main shaft, the lay shaft and the input shaft, since all these shafts are arranged upstream of the range gear.

Since the oil pump driving means 12 is arranged at, or upstream of, the reverse gear, the oil pump driving means 12 will rotate in a certain normal operation direction both in a situation when the vehicle travels forward with one of the forward gears 23-25 engaged and in a situation when the vehicle travels backwards when the reverse gear 26 is engaged. These two situations will hereinafter be referred to as normal driving situations. While the output shaft 15 (and the main shaft 14 in case the reverse gear 26 is arranged as illustrated in Figure 2) will change rotational direction depending on the travel direction of the vehicle (forward or backward), the intermediate gear wheel 30, the lay shaft 12, and the input shaft 10 will have the same rotational direction in both of the two normal driving situations identified above, since the reverse gear 26 when engaged will reverse the rotational direction of the output shaft 15. The oil pump 60 may be arranged to be operated only when the oil pump driving means 12 rotates in the normal operation direction.

The gearbox 4 may further comprise one or more sensors 51-54 for detecting rotational directions (and optionally also speeds) of any one of the shafts 10, 12, 14 and/or of the intermediate gear wheel 30. Optionally, a sensor may be arranged to detect the rotational direction of the output shaft 15 (not shown). For illustrative purpose, the gearbox 4 according to the present example comprises four sensors for detecting the rotational directions of the shafts 10, 12, 14 and of the intermediate gearwheel 30. However, the gearbox 4 may comprise any suitable number of sensors, such as merely one sensor for detecting the rotational speed of one of the shafts 10, 12, 14, 15 and the intermediate gearwheel 30.

The vehicle may further comprise a system 70 for controlling the transmission 2. The system 70 may e.g. be comprised in a control unit of the vehicle. The system 70 may comprise means 71 configured to receive information related to a detected rotational direction of any one of the main shaft 14, the lay shaft 12, the input shaft 10, the output shaft 15 or the intermediate gear wheel 30. The rotational direction may be detected by any one of the sensors 51-54 (or any other sensing means). Optionally, the means 71 may further be configured to receive information related to if one of the forward gears 23-25 or if the reverse gear 26 is engaged.

The system 70 may further comprise means 72 arranged to determine if the oil pump driving means 12 rotates in a direction opposite to the normal operation direction. The determining of if the oil pump driving means rotates in a direction opposite to the normal operation direction may be made in several different ways.

According to a first example, the means 71 may be configured to simply receive information related to a detected rotational speed of any of the shafts and/or gear wheels of the gearbox arranged at, or upstream of, the reverse gear 26, such as of the oil pump driving means itself, which in the present example is the lay shaft 12. According to a further example, the received information may be related to a detected rotation direction of the oil pump itself, which rotation direction is the same as the rotation direction of the oil pump driving means. The means 72 may be configured to make the determination of if the oil pump driving means rotates in a direction opposite to the normal operation direction based on that information.

According to a second example, the means 71 may be configured to receive information related to a detected rotational speed of any of the shafts and/or gear wheels of the gearbox arranged downstream of the reverse gear 26 (such as the main shaft 14 or the output shaft 15 in the present example), and information related to a detection of if one of the forward gears 23-25 or the reverse gear 26 is engaged. The means 72 may then determine the rotational direction of the oil pump driving means based on the information received by the means 71. For example, if it is detected that the main shaft 14 rotates in a negative direction (corresponding to the vehicle travelling backwards) and it is detected that one of the forward gears 21-15 are engaged, the means 72 may determine that the oil pump driving means rotates in the wrong direction.

According to a third example, the means 72 may be configured to determine a travel direction (such as a forward and/or backward direction) of the vehicle and which gear is engaged. The determination of the travel direction may be made based on information from any means able to detect the travel direction of the vehicle, such as an accelerometer a GPS device. Alternatively, the determination of the travel direction may be based on the information related to the detected rotational direction of the main shaft 14 and/or the output shaft 15, which directly indicates the travel direction of the vehicle. According to a further alternative, the determination of the travel direction may be based on the information related to the detected rotational direction of the lay shaft 12, the input shaft 10 and/or the intermediate gear wheel 30 and the information related to which gear is engaged.

In case the reverse gear is incorporated in the range gear, the travel direction may be determined based on the rotational speed of the main shaft and on which gear is engaged.

The gear presently engaged may e.g. be determined based on information received from sensors (not shown) arranged to detect the positions of the coupling sleeves 41.

Based on the determination of the travel direction of the vehicle and on the determination of which gear is engaged, the means 72 may be configured to determine if the oil pump driving means rotates in the direction opposite to the normal operation direction. The oil pump driving means rotates in the direction opposite to the normal operation direction if it is determined that the vehicle travels forward and the reverse gear 26 is engaged, and preferably also if it is determined that the vehicle travels backwards and one of the forward gears 23-25 is engaged.

If the oil pump driving means rotates in the direction opposite to the normal operation direction, the oil pump 60 may not be operated properly and lubrication of the gearbox will be interrupted.

The system 70 may further comprise means 73 configured to initiate manoeuvring of the gearbox 4 into neutral if it is determined that the oil pump driving means rotates in the direction opposite to the normal operation direction. The means 73 may be further configured to subsequently initiate changing of the rotational direction of the oil pump driving means, such as by initiating closing of the clutch 7 or by controlling any other means for transferring torque from the engine to the input shaft 12. When the oil pump driving means is turned around to the normal operation direction again, the oil pump 60 will operate normally again.

Preferably, the initiation of the manoeuvring of the gearbox 4 into neutral may be slightly delayed from the point in time when it is determined that the oil pump driving means rotates in the wrong direction. For example, the delay may be based on a predetermined time period, such as after a few seconds, or on a predetermined number of rounds that any of the shafts or gear wheels of the gearbox 4 has taken. The delay may reduce the risk of initiation of manoeuvring of the gearbox 4 into neutral in situations where this is not desired, such as when the vehicle is to start uphill in a slope.

Figure 3 shows a first driving situation, in which a vehicle 1 travels forwards, downhill in a slope with the reverse gear engaged. This is a typical situation in which the oil pump driving means is caused to rotate in the wrong direction. This situation may have been proceeded by a situation in which the vehicle has been reversing uphill in the slope. As the vehicle 1 starts to travel downhill, the system may detect the abnormal rotational direction of the oil pump driving means (as described in more detail above) and may therefore initiate manoeuvring of the gearbox into neutral and then closing of the clutch, whereby the oil pump will operate properly again.

Figure 4 shows a second driving situation in which the oil pump driving means is caused to rotate in the wrong direction. In the second driving situation, the vehicle 1 travels backwards, downhill in a slope with the forward gear engaged. This situation may have been proceeded by a situation in which the vehicle 1 has been propelled forwards, uphill in the slope. In similarity with the first driving situation, the system may detect the abnormal rotational direction of the oil pump driving means as the vehicle 1 starts to travel downhill, and may therefore initiate maneuvering of the gearbox into neutral and then closing of the clutch, whereby the oil pump will operate properly again.

A method of controlling the transmission of the vehicle according to an embodiment will be described with reference to Figure 5. The method 500 may be performed by the system described above with reference to Figure 2. Further, steps taken by system as described in the examples above may form part of the present method 500.

The method 500 may comprise determining 501 if the oil pump driving means rotates in a direction opposite to the normal operation direction, and if it is determined that the oil pump driving means rotates in the direction opposite to the normal operation direction, initiating 502 maneuvering of the gearbox into neutral and then initiating 503 changing of the rotational direction of the oil pump driving means to the normal operation direction. For example, the determining 501 of if the oil pump driving means rotates in the direction opposite to the normal operation direction may comprise determining 504 the travel direcion of the vehicle (such as by receiving 506 information of a detected rotational direction of a shaft or gear wheel of the gearbox arranged downstream of the reverse gear), and determining 505 which gear is engaged (e.g. by receiving information 507 of a detection of which gear of the gearbox is engaged). As an alternative, the determining 501 of if the oil pump driving means rotates in the direction opposite to the normal operation direction may comprise receiving 509 information of a detected rotational speed of any one of the shafts or gear wheels of the gearbox arranged at, or upstream of, the reverse gear.

The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The systems and methods disclosed in the present specification may be implemented as software, firmware, hardware or a combination thereof. In a hardware implementation, the division of tasks between functional means/units referred to in the above description does not necessarily correspond to the division into physical units; to the contrary, one physical component may have multiple functionalities, and one task may be carried out by several physical components in cooperation. Reference is made to the discussion above, where it was emphasized that the system for controlling a transmission may be embodied in hardware, software or middleware executing under the operating system of a host computer system. Certain means or all means may be implemented as software executed by a digital signal processor or microprocessor, or be implemented as hardware or as an application-specific integrated circuit. Such software may be distributed on computer readable medium, which may comprise computer storage medium (or non-transitory medium) and communication medium (or transitory medium). As is well known to a person skilled in the art, the term computer storage medium includes both volatile and nonvolatile, removable and nonremovable medium implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage medium includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Further, it is well known to the skilled person that communication medium typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media.

Claims

1. Method (500) of controlling a transmission (2) of a vehicle (1), the transmission comprising a gearbox (4) comprising: at least one forward gear (23-25), at least one reverse gear (26), and an oil pump (60) arranged to provide lubrication for the gearbox and to be driven by an oil pump driving means when that oil pump driving means rotates in a normal operation direction, wherein the oil pump driving means includes a shaft (10, 12, 14) or a gear wheel (30) of the gearbox and is arranged at, or upstream of, the reverse gear as seen in a direction of a main torque transmission path extending from an engine (3) of the vehicle towards a propeller shaft (5) of the vehicle, the method comprising: determining (501) if the oil pump driving means rotates in a direction opposite to the normal operation direction, and if it is determined that the oil pump driving means rotates in the direction opposite to the normal operation direction, initiating (502) maneuvering of the gearbox into neutral and then initiating (503) change of the rotational direction of the oil pump driving means to the normal operation direction.

2. The method as defined in claim 1, wherein the transmission comprises a clutch, wherein change of the rotational direction of the oil pump driving means is made by closing the clutch.

3. The method as defined in claim 1 or 2, wherein the transmission comprises a planetary gear coupled to an electric motor for adjusting the amount of torque transfer between an output shaft of the engine and an input shaft of the gearbox, wherein change of the rotational direction of the oil pump driving means is made by controlling the speed of the electric motor so as to provide transfer of torque from the engine to the input shaft of the gearbox.

4. The method as defined in any one of the preceding claims, wherein the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction comprises: determining (504) if the vehicle moves forwards, and determining (505) if the reverse gear is engaged, wherein maneuvering of the gearbox into neutral is initiated if it is determined that the vehicle moves forwards and the reverse gear is engaged.

5. The method as defined in any one of the preceding claims, wherein the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction comprises: determining (504) if the vehicle moves backwards, and determining (505) if the forward gear is engaged, wherein maneuvering of the gearbox into neutral is initiated if it is determined that the vehicle moves backwards and the forward gear is engaged.

6. The method as defined in any one of the preceding claims, wherein the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction comprises: receiving (509) information of a detected rotational direction of a shaft or gear wheel of the gearbox arranged at, or upstream of, the reverse gear.

7. The method as defined in any one of the preceding claims, wherein the determining of if the oil pump driving means rotates in the direction opposite to the normal operation direction comprises: receiving information (506) of a detected rotational direction of a shaft or gear wheel of the gearbox arranged downstream of the reverse gear, and receiving information (507) of a detection of which gear of the gearbox is engaged.

8. The method as defined in any one of the preceding claims, wherein the initiating of the maneuvering of the gearbox into neutral is made a certain time after it is determined that the oil pump driving means rotates in the direction opposite to the normal operation direction, such as after a predetermined time period or after a predetermined number of rotations of at least one of: the oil pump driving means, an input shaft, a main shaft and a lay shaft of the gearbox.

9. The method as defined in any one of the preceding claims, wherein the oil pump driving means is one in the group of: a lay shaft (12), an input shaft (10), a main shaft (14) and an intermediate gear wheel (30) of the reverse gear of the gearbox.

10. The method as defined in any one of the preceding claims, wherein the oil pump is designed so as to not be operated when the oil pump driving means rotates in the direction opposite to the normal operation direction.

11.The method as defined in any one of the preceding claims, wherein the normal operation direction of the oil pump driving means is obtained when the vehicle moves forwards and the forward gear is engaged, and when the vehicle moves backwards and the reverse gear is engaged, respectively.

12. Computer program that, when run on a processor, enables the processor to carry out the method as defined in any one of the preceding claims.

13. Computer program product comprising a computer readable medium on which a computer program according to claim 12 is stored.

14. System (70) for controlling a transmission (2) of a vehicle (1), the transmission comprising a gearbox (4) comprising: at least one forward gear (23-25), at least one reverse gear (26), and an oil pump (60) arranged to provide lubrication for the gearbox and to be driven by an oil pump driving means when that oil pump driving means rotates in a normal operation direction, wherein the oil pump driving means includes a shaft (10, 12, 14) or a gear wheel (30) of the gearbox and is arranged at, or upstream of, the reverse gear as seen in a direction of a main torque transmission path extending from an engine (3) of the vehicle towards a propeller shaft (5) of the vehicle, the system comprising: means (72) configured to determine if the oil pump driving means rotates in a direction opposite to the normal operation direction, and means (73) configured to, if the oil pump driving means rotates in the direction opposite to the normal operation direction, initiate maneuvering of the gearbox into neutral and then initiate changing of the rotational direction of the oil pump driving means to the normal operation direction.

15. Vehicle (1) comprising a system as defined in claim 14.