FI ELD OF TH E I NVENTION AN D P RIOR ART

The present invention pertains to a system according to the preamble to clai m 1 for lubrication and cooling of a gearbox equipped with synchromeshes, and a method for control of a flow of transmission oil in such a system . The invention also pertains to a computer program and a computer program product comprising computer program code for the implementation of a method according to the invention, and an electronic control device. I n order to reduce the wear and thus extend the life of different components in a gearbox, these components are lubricated with transmission oil . The oil system in a gearbox in a motor vehicle usually comprises an oil pu mp in the form of a displacement pump of rotor type, connected to a side shaft in the gearbox in order to be operated by the same, so that the oil pu mp's pu mp rotor is operated to rotate with the same rotation speed as the side shaft. From an oil sump at the bottom of the gearbox, transmission oil is sucked up by the oil pump in order to be fed through oil channels in the gearbox, following which the transmission oil trickles back down into the oil sump. Certain types of gearboxes are equipped with synchromeshes, becoming activated in connection with a change of gear in the gearbox to achieve a synchronous rotation speed of two components, which become rotatably engaged with each other through the shifting operation. These synchromeshes emit a friction heat when they are active, and need to be cooled down to reduce wear and thus to extend the life of the synchromeshes. The required cooling of the synchromeshes occurs with the help of the circulating transmission oil , brought to flow past the synchromeshes to lead heat away from these. In order to improve the cooling ability of the transmission oil , the transmission oil may be led through an oil cooler before it is led into the oil channels in the gearbox. OBJ ECTIVE OF TH E I NVENTION

The objective of the present invention is to achieve a new and advantageous way of controlling the flow of transmission oil in a gearbox equipped with synchromeshes.

SUMMARY OF TH E I NVENTION

According to the present invention, said objective is achieved with a system having the characteristics defined in claim 1 .

The system according to the invention comprises :

- an oil conduit, which is connected to oil channels in the gearbox to enable the transmission oil to be fed from the oil conduit to said oil channels for lubrication and cooling of bearings and synchromeshes inside the gearbox,

- an oil pu mp for the generation of a flow of transmission oil through the oil conduit, in the direction towards said oil channels,

- a cooling device connected to the oil conduit for cooling of the transmission oil ,

- an electric engine for operation of the oil pump, and - an electronic control device, for control of the engine speed in the electric engine.

The electronic control device is arranged to control the electric engine's engine speed, so that it temporarily increases from a normal engine speed level to an elevated engine speed level , when it obtains information indicating that a shift event for change of gears in the gearbox has been initiated or is intended to be initiated. The engine speed increase of the electric engine leads to a corresponding rotation speed increase in the oil pump, and thus to a temporarily increased volume flow of transmission oil in the oil conduit and in said oil channels during the shift event, so that a temporarily increased cooling effect of the transmission oil flowing through the oil channels is obtained during the shift event. The increased volume flow of transmission oil during the shift event entails that the transmission oil's ability to deflect friction heat from the synchromeshes inside the gearbox increases, which in turn provides an improved cooling of the synchromeshes, and thus an increased service life of these. According to one embodiment of the invention , the electronic control device is arranged to control the electric engine at said temporary engine speed increase, so that it assumes an engine speed corresponding to a predetermined fixed set value. Thus, the solution according to the invention may be implemented in a relatively easy manner.

According to another embodiment of the invention, the electronic control device is arranged to control the electric engine at said temporary engine speed increase, so that it assumes an engine speed corresponding to a set value calculated by the electronic control device, based on a predetermined calculation model . Thus, the engine speed of the electric engine and thereby the rotation speed of the oil pu mp may be controlled based on criteria determined in advance, so that the volume flow of transmission oil during different shift events is adapted, depending on the cooling effect required for the respective shift events.

Other favourable features of the system according to the invention are set out in the dependent claims and the description below.

The invention also pertains to a method with the characteristics defined in claim 7, for control of a flow of transmission oil in a system for lubrication and cooling of a gearbox equipped with synchromeshes.

Other advantageous features of the method according to the invention are set out in the dependent claims and the description below.

The invention also pertains to a computer program with the characteristics defined in claim 1 3, a computer program product with the characteristics defined in claim 1 4 and an electronic control device with the characteristics defined in claim 1 5.

BRI EF DESCRI PTION OF TH E DRAWI NGS The invention is described below with the help of example embodiments, with reference to the enclosed drawings. Shown in : is a diagram of a system according to one embodiment of the present invention , is a diagram of an electronic control device for the implementation of a method according to the invention, and

Fig. 3 is a flow chart illustrating a method according to one embodiment of the invention . DETAI LED DESCRI PTION OF EMBODI M ENTS ACCORD I NG TO TH E I NVENTION

Fig. 1 illustrates very schematically a gearbox 1 for a motor vehicle. The gearbox 1 is equipped with synchromeshes 2, 2' , 2" of a prior art type, controlled by an electronic control device 3.

The gearbox 1 may e.g . comprise a number of synchromeshes 2, each of which is arranged for connection of a rotating shaft in the gearbox 1 with a cogwheel , which is rotatably supported on the given shaft. When such a synchromesh 2 is activated by the control device 3 in connection with a shift event for change of gears in the gearbox 1 , the synchromesh 2 is arranged to achieve a synchronous rotation speed of a rotating shaft and a cogwheel rotatably supported on the shaft, before these are brought into a rotatable engagement with each other. Said shaft may e.g . consist of an input shaft, a layshaft or a main shaft of the gearbox 1 .

The gearbox 1 may also comprise a synchromesh 2' , which is arranged for mutual connection of an input shaft and a main shaft of the gearbox when, in connection with a change of gears in the gearbox, a direct connection between these shafts is to be set up. When such a synchromesh 2' is activated by the control device 3 in connection with a shift event for change of gears in the gearbox 1 , the synchromesh 2' is arranged to achieve a synchronous rotation speed of the input shaft and the main shaft, before these are brought in a rotatable engagement with each other. In cases where the gearbox 1 comprises a range gear unit with a planetary gear, the gearbox 1 may also comprise a synchromesh 2" , which is arranged to act on a ring wheel of said planetary gear in connection with a change of gears between a low range gear and a high range gear in the range gear unit. In the low range gear, the ring wheel is rotatably connected with a first coupling element, which is rotatably connected with the gearbox house of the gearbox, and in the high range gear the ring wheel is rotatably connected with a second coupling element, which is rotatably connected with the main shaft of the gearbox. When this synchromesh 2" is activated by the control device 3 in connection with a change of gears from a low range gear to a high range gear in the range gear unit, the synchromesh 2" is arranged to achieve a synchronous rotation speed of the ring wheel and said second coupling element, before these are brought into a rotatable engagement with each other. When this synchromesh 2" is activated by the control device 3 in connection with a change of gears from a high range gear to a low range gear in the range gear unit, the synchromesh 2" is arranged to brake the ring wheel to a standstill , before the ring wheel is brought into a rotatable engagement with said first coupling element.

The gearbox 1 has an input shaft 4 which, via a coupling device 5, may be connected with a drive shaft 6 of a drive engine 7. With the help of the coupling device 5, the input shaft 4 of the gearbox may be brought into a transmission connection with, as well as disconnected from, said drive shaft 6. The drive engine 7 may e.g. consist of a combustion engine. Fig. 1 illustrates a system 1 0 for lubrication and cooling of the gearbox 1 . This system 1 0 comprises an oil conduit 1 1 , which is connected to oil channels 1 2 in the gearbox to enable the transmission oil to be fed from the oil conduit 1 1 to said oil channels 1 2, for lubrication and cooling of bearings and synchromeshes 2, 2' , 2" inside the gearbox 1 . The system 1 0 also comprises and oil pu mp 1 3 in the form of a displacement pump of rotor type, for generation of a flow of transmission oil through the oil conduit 1 1 in the direction towards said oil channels 1 2. A cooling device 1 4 in the form of a conventional oil cooler is connected to the oil conduit 1 1 for cooling of the transmission oil . The cooling device 1 4 is connected with the oil conduit 1 1 , between the oil pump 1 3 and said oil channels 1 2. A thermostat 1 5 is arranged inside the oil conduit 1 1 , between the oil pump 1 3 and the cooling device 1 4. Depending on the temperature of the transmission oil flowing inside the oil conduit 1 1 , the thermostat 1 5 leads the transmission oil to the cooling device 1 4, to be cooled in this before the transmission oil is led further along to the oil channels 1 2 in the gearbox, or directly to these oil channels 1 2 via a bypass conduit 1 6 without passing through the cooling device 1 4. An oil filter 1 7 of conventional type is arranged inside the oil conduit 1 1 , between the oil pu mp 1 3 and the thermostat 1 5, for filtration of the transmission oil flowing through the oil conduit 1 1 . An oil sump 1 8 is arranged at the bottom of the gearbox 1 . From this oil sump 1 8, transmission oil is sucked up by the oil pump 1 3 in order to be fed through the oil conduit 1 1 . After its passage through the oil channels 1 2 in the gearbox 1 , the transmission oil trickles back down into the oil sump 1 8. The system 1 0 comprises an electric engine 1 9 for the operation of the oil pump 1 3 and an electronic control device 20 for control of the engine speed of the electric engine 1 9. The electronic control device 20 is arranged to receive information, e.g . from the control device 3, indicating when a shift event for change of gears in the gearbox 1 has been initiated, or is intended to be initiated.

In a normal case, when the electronic control device 20 has not received any information indicating that a shift event for change of gears in the gearbox 1 has been initiated or is intended to be initiated, the electronic control device 20 is arranged to control the engine speed of the electric engine 1 9 according to an engine speed level , which is here referred to as a normal engine speed level . When the electronic control device 20 controls the electric engine 1 9 according to the normal engine speed level , the electronic control device 20 may e.g. be arranged to determine the desired engine speed N for the electric engine 1 9, according to the following formula:

_ N _eng

Rs where :

N is the desired engine speed for the electric engine 1 9,

N _eng is the engine speed of the drive engine's drive shaft 6, and

R, is the gearing of a split gear unit comprised in the gearbox 1 .

When the electronic control device 20 obtains information from the control device 3, indicating that a shift event for change of gears in the gearbox 1 has been initiated or is intended to be initiated, the electronic control device 20 is arranged to generate a temporary engine speed increase in the electric engine 1 9, so that the electric engine's engine speed temporarily increases from the normal engine speed level to an elevated engine speed level , in order thus to achieve a temporarily increased volu me flow of transmission oil in the oil conduit 1 1 and in said oil channels 1 2 during the shift event and thus a temporarily increased cooling effect of the transmission oil flowing through the oil channels 1 2. Thereby an improved cooling of the synchromeshes 2, 2' , 2" is obtained during the shift event. According to a first alternative, the electronic control device 20 is arranged to control the electric engine 1 9 at said temporary engine speed increase, so that it assumes an engine speed corresponding to a predetermined fixed set value, which advantageously corresponds to a predetermined value of the maxi mum allowed engine speed for the electric engine 1 9.

According to a second alternative, the electronic control device 20 is arranged to control the electric engine 1 9 at said temporary engine speed increase, so that it assumes an engine speed corresponding to a set value N _caic , calculated by the electronic control device 20 based on a predetermined calculation model . The electronic control device 20 may e.g. be arranged to determine said set value N _caic according to the following formula:

where :

N _ca ic is the calculated set value for the engine speed of the electric engine 1 9,

N _eng is the engine speed of the drive engine's drive shaft 6,

N _main is the engine speed of the main shaft of the gearbox,

N _max is the maximum allowed engine speed for the electric engine 1 9,

R _sn is the split gear unit's gear ratio for the new gear intended to be engaged during the given shift event,

R _sp is the split gear unit's gear ratio for the most recently engaged gear,

R _mn is the gear ratio of the main gear unit of the gearbox for the new gear intended to be engaged during the given shift event, and D _ref is a predetermined reference engine speed difference, which may be set at e.g. 1 ,000 rpm .

The formulae specified above are based on a case where the oil pump 1 3 is operated by the electric engine 1 9 without any intermediary gear unit, i .e. where the oil pump's pu mp rotor rotates with the same engine speed as the output shaft 21 of the electric engine 1 9. In case a gear unit is arranged between the electric engine 1 9 and the oil pump 1 3, the formulae specified above may be completed with a constant, representing represents the gear ratio between the electric engine's output shaft and the oil pu mp's pump rotor.

After the engine speed increase specified above has been executed, the electronic control device 20 is arranged to control the electric engine's engine speed, so that it is reduced from the elevated engine speed level to the normal engine speed level , when the electronic control device 20 has determined that a predetermined condition is met. According to a first alternative, the electronic control device 20 is arranged to control the electric engine's engine speed so that it is reduced from the elevated engine speed level to the normal engine speed level , when the electronic control device 20 has determined that a given time has elapsed since the point in time when the electronic control device 20 initiated the temporary engine speed increase. According to a second alternative, the electronic control device 20 is arranged to control the electric engine's engine speed so that it is reduced from the elevated engine speed level to the normal engine speed level , when the electronic control device 20 has determined that the current shift event has been completed, e.g . by having received information indicating this from the control device 3.

The electronic control device 20 described above may be implemented through one single electronic control device in the motor vehicle, as illustrated in Fig. 1 . The electronic control device 20 could , however, be implemented through two or more mutually collaborating electronic control devices in the motor vehicle.

Fig. 3 shows a flow chart illustrating an embodiment of a method according to the present invention, for the control of a flow of transmission oil in a system 1 0 of the type described above. In a first step S1 , the electronic control device 20 determines whether a shift event for change of gears in the gearbox 1 has been initiated . If, in step S1 , the electronic control device 20 has determined that no shift event has been initiated, this step S1 is repeated after a certain time delay. If, in step 1 , the electronic control device 20 has determined that a shift event has been initiated , the electronic control device 20 calculates, in a subsequent step S2, a set value N _ca/c for an elevated engine speed of the electric engine 1 9. In a third step S3, the electric engine 1 9 is controlled by the electronic control device 20 to assu me an engine speed corresponding to said set value N _caic , so that the engine speed of the electric engine 1 9 increases from a normal engine speed level to an elevated engine speed level . In a fourth step S4, the electronic control device 20 determines whether the shift event has been completed. If, in step S4, the electronic control device 20 has determined that the shift event has not been completed, this step S4 is repeated after a certain time delay. If, in step S4, the electronic control device 20 has determined that the shift event has been completed, the electronic control device 20 controls the electric engine's engine speed in a fifth step S5, so that it is reduced from the elevated engine speed level to the normal engine speed level . Subsequently, the first step S 1 mentioned above is repeated.

A computer program code, for the implementation of a method according to the invention, is suitably included in a computer program, loadable into the internal memory of a computer, such as the internal memory of an electronic control device of a motor vehicle. Such a computer program is suitably provided via a computer program product comprising a data storage medium readable by an electronic control device, which data storage mediu m has the computer program stored thereon. Said data storage medium is e.g. an optical data storage medium in the form of a CD-ROM , a DVD, etc. , a magnetic data storage medium in the form of a hard disk drive, a diskette, a cassette, etc. , or a Flash memory or a ROM , PROM , EPROM or EE PROM type memory.

Fig. 2 illustrates very schematically an electronic control device 30 comprising an execution means 31 , such as a central processor unit (CPU) , for the execution of a computer software. The execution means 31 communicates with a memory 32, e.g. a RAM memory, via a data bus 33. The control device 30 also comprises a data storage medium 34, e.g . in the form of a Flash memory or a ROM , P ROM , EPROM or E EPROM type memory. The execution means 31 communicates with the data storage means 34 via the data bus 33. A computer program, comprising computer program code for the implementation of a method according to the invention, e.g. in accordance with the embodiment illustrated in Fig . 3, is stored in the data storage mediu m 34.

The system and the method according to the invention are specifically designed to be used in a heavy goods vehicle, such as a bus, a tractor or a truck. The invention is not limited in any way to the embodiments described above, but nu merous possible modifications thereof should be obvious to a person skilled in the area, without such person departing from the spirit of the invention as defined by the appended claims.