Automated non-synchronized gear-change transmission and method for gear change in such a transmission

[0001] This application claims the priority of German Patent Document No. 101 38 115.8, filed Aug. 3, 2001, the disclosure of which is expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The invention relates to an automated non-synchronized gear-change transmission for a motor vehicle and to a method for gear change in such a gear-change transmission.

[0003] DE 195 44 322 A1 discloses an automated non-synchronized gear-change transmission in the form of a vehicle transmission, with a pressure-oil lubrication device in the form of a lubricant distributor system. The lubricant is distributed to various wheels and bearings of the gear-change transmission by means of a fluid pump from a sump in a transmission case. The fluid pump is connected to a shaft in the gear-change transmission, the shaft being driven by a drive machine in the form of an engine, so that the fluid pump is driven rotatably by the shaft whenever the gear-change transmission is in operation.

[0004] By contrast, an object of the invention is to propose an automated non-synchronized gear-change transmission and a method for gear change in such a gear-change transmission, by which a particularly comfortable operation of the gear-change transmission becomes possible.

[0005] The gear-change transmission has a transmission input shaft and a pressure-oil lubrication device, by which lubricating oil can be delivered from a transmission sump to various wheels and bearings of the gear-change transmission. The pressure-oil lubrication device has a pump which can be driven at least indirectly by the transmission input shaft. A drive of the pump is connected positively or non-positively to the transmission input shaft. The pump may be driven, for example, directly by the transmission input shaft or by a countershaft which is operatively connected to the transmission input shaft. The pressure-oil lubrication device has a cross-section modification device, by which a flow cross section of the pressure-oil lubrication device can be modified on a delivery side of the pump. The drive torque to be applied for the pump and the drive power can consequently be modified. A rotational speed of the transmission input shaft can therefore be influenced. Gear changes can consequently be carried out in a particularly comfortable way.

[0006] When first gear or reverse gear is selected, with the motor vehicle at a standstill, a transmission output shaft is stationary. Since a clutch, which is arranged between a drive machine and the gear-change transmission, can transmit a little torque, even in the open state, the transmission input shaft can rotate. Unacceptably high rotational-speed differences may therefore occur between corresponding shift elements and gearwheels of the gears. A selection of the gears would lead to unacceptable noises. By the cross-section modification device of the pressure-oil lubrication device, the transmission input shaft can be braked to a standstill. A particularly comfortable selection of first gear and of reverse gear thus becomes possible. Moreover, the synchronous rings for first gear and reverse gear which are used in conventional gear-change transmissions may be dispensed with. This leads to a particularly cost-effective gear-change transmission.

[0007] In the gear-change transmission according to the invention having a pressure-oil lubrication device, components subject to high load can be supplied with lubricating oil. A reliable operation of the gear-change transmission can consequently be achieved. In gear-change transmissions without pressure-oil lubrication, splash lubrication is necessary. In this case, rotating gearwheels dip into the transmission sump and take up oil. By the rotation of the gearwheels, the oil is thrown away and is consequently distributed randomly for lubrication in the gear-change transmission. Dipping into the oil sump brings about a braking force on the gearwheels, with the result that a drag torque of the gear-change transmission rises and efficiency falls. This leads to increased fuel consumption of the motor vehicle. In the case of gear-change transmissions with pressure-oil lubrication, an oil level in the transmission sump may be lowered to an extent such that a dipping of gearwheels no longer occurs. Drag losses of the gear-change transmission are therefore lower than in the gear-change transmissions with splash lubrication. This leads advantageously to a lower fuel consumption of the motor vehicle. Moreover, the lubricating-oil quantity can be reduced, thus leading to a saving in terms of cost and weight.

[0008] In the method according to the invention, in the event of an upshift from an original gear into a target gear, after a disengagement of the original gear a flow cross section of the pressure-oil lubrication device is reduced on a delivery side of a pump which is connected positively or non-positively to an input shaft of the gear-change transmission. In the event of an upshift, the transmission input shaft must be brought to a synchronous rotational speed of the target gear which is lower than the rotational speed of the transmission input shaft in the original gear. The synchronous rotational speed is reached when a shift element of the target gear and a gearwheel of the target gear have the same or virtually the same rotational speed. By reducing cross section, the pressure of a lubricating oil rises downstream of the pump, with the result that the drive torque to be applied for the pump and the drive power rise. A rotational speed of the transmission input shaft therefore falls rapidly in the direction of the synchronous rotational speed. The rotational-speed difference therefore does not have to be absorbed by the shift element. The absorption of the rotational-speed difference by the shift element would lead t a jolt in the motor vehicle and to a pronounced generation of noise. The target gear can thus be selected comfortably and after a short time. Since there is no need for absorption, the useful life of the shift elements increases or the shift element can be made lighter and more cost-effective. A selection of the target gear after a short time is advantageous particularly in the case of a drive machine designed as an internal combustion engine with an exhaust-gas turbocharger. In such drive machines, a gas throughput falls during this shift, with the result that a rotational speed of the exhaust-gas turbocharger likewise falls. Consequently, a torque required after the gear change can be made available by the drive machine only with a delay. If the time until the target gear is selected is short, no delay arises.

[0009] The method according to the invention can be used for single and multiple shifts.

[0010] In a preferred embodiment of the invention, the cross-section modification device reduces the flow cross section of the pressure-oil lubrication device during upshifts from an original gear into a target gear for the purpose of reducing a rotational speed of the transmission input shaft. The drive torque to be applied for the pump and the drive power are consequently increased. A rotational speed of the transmission input shaft therefore falls rapidly in the direction of the synchronous rotational speed. The target gear can therefore be selected comfortably and quickly. The duration of the upshift is very short, and, consequently, an interruption in traction on driven wheels of the motor vehicle is also short. The pump, in conjunction with the cross-section modification device, therefore acts as a central synchronization device for upshifts. Synchronization in the case of downshifts can be carried out by the drive machine, with the clutch closed or partially closed.

[0011] In another embodiment of the invention, the cross-section modification device is arranged on an oil distribution duct of the pressure-oil lubrication device. The oil distribution duct follows the pump. The lubricating oil is led by the oil distribution duct to the components to be lubricated. This leads to a particularly cost-effective refinement of the gear-change transmission, since a conventional pump can be used.

[0012] In still another embodiment of the invention, the cross-section modification device has an actuator which can be activated by a control device and the activation takes place as a function of at least one state variable of the motor vehicle and/or of the gear-change transmission. The actuator may be designed, for example, as an electromagnet, stepping motor, solenoid valve or hydraulic slide. Activation may take place, for example, as a function of the type of shift (traction upshift, traction downshift, overrun upshift, overrun downshift), the original or target gear, vehicle acceleration, vehicle speed, torque output by the drive machine, the position of a power requirement member and/or the rotational speed of the drive machine. This allows a particularly comfortable operation of the gear-change transmission, since a braking of the transmission input shaft can be activated in a highly specific manner.

[0013] In a further embodiment of the invention, the cross-section modification device can be actuated by an actuating device, by which shift elements of the gear-change transmission can also be actuated. The shift elements may be designed, for example, as sliding sleeves. In an automated gear-change transmission, the shift elements are actuated by a suitable actuating device which has actuators activated by a control device. The actuating device may have, for example, a shift roller or shift rods. This constitutes a particularly cost-effective refinement, since additional actuators do not have to be used.

[0014] In a still further embodiment of the invention, the pressure-oil lubrication device has a pressure-limiting device on the delivery side. The pressure-limiting device may be designed, for example, as a pressure relief valve. In the case of a reduced flow cross section on the delivery side of the pump, the pressure of the lubricating oil on the delivery side and therefore the drive torque to be applied for the pump depend closely on a driving rotational speed of the pump. If the pressure-oil lubrication device has a pressure-limiting device, the pressure is independent of the driving rotational speed within a wide rotational-speed range. Consequently, gear changes can be controlled or regulated more effectively and a more comfortable operation of the gear-change transmission is ensured.

[0015] In a yet further embodiment, the pressure-oil lubrication device has at least one heat exchange element. The heat exchange element may be designed, for example, as a (air) cooler or a heat exchanger.

[0016] By means of the heat exchanger, the lubricating oil can exchange heat with lubricants or coolants of other assemblies of the motor vehicle, such as, for example, cooling fluid or lubricating oil of the drive machine. A temperature of the gear-change transmission can consequently be influenced specifically. If the gear-change transmission is at a low temperature, efficiency is poorer than in an optimum temperature range. In order to increase the efficiency of the gear-change transmission as quickly as possible when the motor vehicle is started, the generated heat can be utilized by other assemblies such as drive machines. This leads advantageously to a low fuel consumption of the motor vehicle. By cooling the lubricant, it is possible to ensure that a defined temperature of the gear-change transmission is not exceeded. This increases the useful life of the gear-change transmission.

[0017] In a method according to the invention, for gear change in an automated non-synchronized gear-change transmission of a motor vehicle, a clutch arranged between a drive machine and the gear-change transmission is at least partially closed at least between the disengagement of the original gear and a selection of the target gear. The clutch may be closed completely or only partially. Consequently, an output shaft of the drive machine is connected to the transmission input shaft of the gear-change transmission. In the case of an upshift, therefore, by the flow cross section being reduced, a rotational speed of the drive machine is also reduced. The gear change can therefore proceed particularly quickly.

[0018] Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]
FIG. 1 shows a diagrammatic illustration of a gear-change transmission in the neutral position, with six forward gears and one reverse gear.

[0020]
FIG. 2 shows a diagrammatic illustration of a pressure-oil lubrication device with a cross-section modification device, a bypass line, a pressure-limiting device and a heat exchange element.

[0021]
FIG. 3 shows a diagrammatic illustration of a pressure-oil lubrication device according to FIG. 2 with a bypass line.

[0022]
FIG. 4 shows an actuating device for shift elements and a cross-section modification device with a shift roller.

[0023]
FIG. 5 shows a section through an actuating device for shift elements and a cross-section modification device.

[0024]
FIG. 6 shows a block diagram of a control program for an upshift.

DETAILED DESCRIPTION OF THE DRAWINGS

[0025] According to FIG. 1, a gear-change transmission 10 has a transmission input shaft 11 which can be coupled via a clutch 12 to a coaxially arranged output shaft 13 of a drive machine (not illustrated). The clutch 12 can be engaged and disengaged by an actuating device (not illustrated), which is activated by a control device 34. A gearwheel 14 is nonrotationally connected to the transmission input shaft 11 and meshes with a gearwheel 15 which is nonrotatably connected to a countershaft 16 arranged parallel to the transmission input shaft 11. Fixed wheels 17, 18, 19, 20 and 21 for the 6th, 3rd, 4th, 2nd and 1st gears are arranged nonrotationally on the countershaft 16. The fixed wheels 17, 18, 19, 20 and 21 mesh in each case with associated loose wheels 22, 23, 24, 25 and 26 which are arranged rotatably on a transmission output shaft 27 arranged preferably coaxially with the transmission input shaft 11. The loose wheel 22 can be nonrotationally connected to the transmission output shaft 27 by a sliding sleeve 28, the loose wheels 23 and 24 by a sliding sleeve 29, the loose wheel 25 by a sliding sleeve 30 and the loose wheel 26 by a sliding sleeve 31. For this purpose, the sliding sleeves 28, 29, 30, 31 can be moved axially within certain limits on the transmission output shaft 27 by an actuating device (not illustrated) which has an actuator activated by the control device 34. The actuating device may have, for example, a shift roller.

[0026] A pump 35 is arranged at the clutch-side end 36 of the countershaft 16 coaxially to the countershaft 16 and is driven by the countershaft 16. A pressure-oil lubrication device 37 has a suction side 38, which is arranged upstream of the pump 35, and a delivery side 39, which is arranged downstream of the pump 35. On the suction side 38, the pump 35 sucks lubricating oil, via a suction line 40, out of a transmission sump 41 which is arranged on the bottom of a case not illustrated, of the gear-change transmission 10. On the delivery side 39, the pump 35 is followed by an oil distribution duct 42, by which the lubricating oil is distributed to components to be lubricated (gearwheel 14, loose wheels 22, 24). Arranged on the oil distribution duct 42 is a cross-section modification device in the form of a solenoid valve 43 having an electromagnet 46 which can be activated by the control device 34. A flow cross section of the oil distribution duct 42 can be modified by the solenoid valve 43. Moreover, a heat exchanger 44 is arranged on the oil distribution duct 42. The heat exchanger 44 has the lubricating oil flowing through in the oil distribution duct 42 and a cooling fluid of the drive machine (not illustrated) flowing through in the cooling-fluid duct 45. Heat exchange between the lubricating oil and the cooling fluid is thus possible.

[0027]
FIG. 2 shows a diagrammatic illustration of a pressure-oil lubrication device 137. The pressure-oil lubrication device 137 has a pump 135 which is driven by a transmission input shaft 111 of a gear-change transmission. The pressure-oil lubrication device 137 has a suction side 138, which is arranged upstream of the pump 135, and a delivery side 139, which is arranged downstream of the pump 135. On the suction side 138, the pump 135 sucks lubricating oil out of a transmission sump 141 via a suction line 140. The pump 135 conveys the lubricating oil on the delivery side into an oil distribution duct 142, on which a cross-section modification device in the form of an adjustable throttle 143 is arranged. A flow cross section of the oil distribution duct 142 can be modified by the throttle 143. The throttle 143 is actuated by a shift roller (not illustrated), which also actuates the sliding sleeves 28, 29, 30, 31 from FIG. 1. Downstream of the throttle 143, in this diagrammatic illustration, the oil distribution duct 142 terminates in a lubrication system 146. All the feedlines and lubricating orifices for distributing the lubricating oil in the gear-change transmission are combined in the lubrication system 146. The lubricating oil runs out of the lubrication system 146 via an outflow line 147 back into the transmission sump 141.

[0028] The throttle 143 can be bypassed by a line 150 which branches off from the oil distribution duct 142 upstream of the throttle 143 and which issues into the oil distribution duct 142 again downstream of the throttle 143. A pressure-limiting device in the form of a pressure-limiting valve 151 is arranged in the line 150. When, with the throttle 143 closed, the pressure of the lubricating oil between the throttle 143 and the pump 135 exceeds a threshold value, the pressure-relief valve 151 opens the line 150 and lubricating oil can flow out into the lubrication system 146. When the pressure of the lubricating oil falls below the threshold value again, the pressure-relief valve 151 shuts off the line 150 again. This ensures that the pressure of the lubricating oil does not exceed the threshold value. The maximum drive torque of the pump 135 can be fixed by the selection of the threshold value.

[0029]
FIG. 3 shows a diagrammatic illustration of a pressure-oil lubrication device 237. The pressure-oil lubrication device 237 has, in comparison with the pressure-oil lubrication device 137 from FIG. 2, a bypass line 248. The bypass line 248 branches off from an oil distribution duct 242 upstream of a throttle 243 and issues into the oil distribution duct 242 again downstream of the throttle 243. Arranged in the bypass line 248 is a valve 249, by which the bypass line 248 can be opened or shut off. In the non-activated state, the valve 249 shuts off the bypass line 248. The valve 249 is likewise actuated by the roller (not illustrated), by which the throttle 243 is also actuated.

[0030] In the case of an upshift, the throttle 243 is closed and the valve 249 keeps the bypass line shut off. The pressure of the lubricating oil consequently rises downstream of a pump 235. In the case of a downshift, the throttle 243 is likewise closed by being coupled to the actuating device of the shift elements. Since, in the case of a downshift, a transmission input shaft 211 has to be accelerated, an increased drive torque of the pump 235 is undesirable. For this reason, the bypass line 248 is opened by the valve 249 and the lubricating oil can flow out in the direction of a lubrication system 246.

[0031] According to FIG. 4, an actuating device 360 has a shift roller 361. Guide tracks 362, 363, 364, 365, by means of which the sliding sleeves 28, 29, 30 and 31 from FIG. 1 are actuated, are introduced into the shift roller 361. The shift roller 361 can be rotated about its axis of rotation A-A by means of an electric motor 366 which is activated by the control device 34 from FIG. 1.

[0032] A mainly hollow-cylindrical contour disk 367 is arranged coaxially on a circumference of the shift roller 361. FIG. 5 shows a section through the actuating device 360 perpendicularly to the axis of rotation A-A, along the sectional axis B-B. The contour disk 367 has a plurality of recesses 368 on the circumference. The recesses 368 are symmetrical to the section axis B-B and extend over the entire axial extent of the contour disk 367. According to FIG. 4, the contour disk 367 is operatively connected to a diaphragm 343 by a connecting rod 369 which is arranged along the sectional axis B-B. One end 370 of the connecting rod 369 is located on the circumference of the contour disk 367; the other end 371 of the connecting rod 369 bears on a lower surface 372 of a diaphragm body 373. Arranged on the opposite surface 374 of the diaphragm body 373 is a spring 375, by which the diaphragm body 373 and the connecting rod 369 are pressed towards the contour disk 367 along the sectional axis B-B. The diaphragm body 373 is designed mainly cylindrically and symmetrically to the sectional axis B-B and is guided in a housing 376. The diaphragm body 373 has on an outer surface 377 a peripheral recess 378.

[0033] The diaphragm 343 is arranged in an oil distribution duct 342. By means of a displacement of the diaphragm body 373 along the sectional axis B-B, the flow cross section of the oil distribution duct 342 can be modified. The flow cross section depends on whether and to what extent the lubricating oil can flow along the recess 378. The position of the diaphragm body 373 and therefore the flow cross section are determined by the radial extent of the contour disk 367 at the point at which the end 370 of the connecting rod 369 comes to bear. In the position of the diaphragm body 373, as shown in FIG. 4, there is a maximum flow cross section.

[0034]
FIG. 5 shows a section through the actuating device 360 along the sectional axis B-B. Driving tabs 379 are arranged on the circumference of the shift roller 361. The driving tabs 379 are pivotable about a fastening point 380 and are pressed radially outwards against an inner surface 382 of the contour disk 367 by springs 381. Wedges 383 are arranged on the inner surface 382 of the contour disk 367. The wedges 383 are arranged in such a way that, in the event of a clockwise rotation of the shift roller 361 (downshift), the driving tabs 379 are pressed radially inwards by the wedges 383 counter to the force of the springs 381. The contour disk 367 therefore remains stationary. In the event of anti-clockwise rotation (upshifts), the driving tabs 379 stand against the wedges 383 and co-rotate the contour disc 367. During a rotation of the contour disc 367, the end 370 of the connecting rod 369 slides on the circumference of the contour disc 369 and transmits the changes in the radial extent of the contour disc 367 to the diaphragm body 373. When the end 370 is located in a recess 368, there is a maximum flow cross section.

[0035] The functioning of the driving tabs 379, springs 381 and wedges 383 corresponds to the functioning of a freewheel known.

[0036]
FIG. 6 illustrates a block diagram of a control program for an upshift by one gear from an original gear into a target gear by an actuating device 360, according to FIGS. 4 and 5 and a pressure-oil lubrication device 137 according to FIG. 2. The control program is executed by the control device 34 from FIG. 1.

[0037] In block 401, the control program is started by an upshift requirement. The shift requirement is generated either by a vehicle driver by a suitable operating device or by the control device 34 on the basis of state variables of the motor vehicle, such as vehicle speed, vehicle acceleration or rotational speed of the drive machine.

[0038] In block 402, the clutch 12 is opened and the torque made available by the drive machine is reduced. In block 403, the original gear is disengaged by a rotation of the shift roller 361. By a further rotation of the shift roller 361 in block 404, the throttle 143 is closed. By virtue of this, the pressure of the lubricating oil on the delivery side 139 and the drive torque necessary for the pump 135 rise. This drive torque acts as a braking torque on the transmission input shaft 111 and decelerates the latter. In block 405, a check is made as to whether the rotational-speed difference between the rotational speed of the transmission input shaft 111 and the synchronous rotational speed of the target gear has undershot a threshold value. If the check is negative, the check is repeated until a positive result is obtained. In this case, in block 406, the throttle 143 is opened again by a further rotation of the shift roller 361. In block 407, the shift roller 361 is again rotated further and, consequently, the target gear is selected. Subsequently, in block 408, the clutch is closed again and the available torque of the drive machine is set according to the instructions of the vehicle driver. In block 409, the shift is concluded.

[0039] The gear-change transmission may also be designed as a transmission in which the selection and disengagement of the gears are carried out by the vehicle driver and only the actuation of the clutch takes place by actuators.

[0040] The gear-change transmission may also be designed as a transmission with synchronizing devices, such as synchronous rings. In this case, the pressure-oil lubrication device together with the cross-section modification device relieves the synchronizing devices and therefore increases their useful life.

[0041] The valve of the bypass line, by which the cross-section modification device can be bypassed, may also be actuated by an actuator which is activated by a control device.

[0042] In the case of an upshift, it is not necessary for all the steps required to be executed in succession. The steps, such as the opening of the clutch and the disengagement of the original gear, may also be executed in parallel.

[0043] The clutch may also remain closed completely or partially in the case of an upshift. Consequently, the rotational speed of the drive machine can also be reduced at the same time as that of the transmission input shaft.

[0044] If the cross-section modification device is activated by a control device, the flow cross section during upshifts is narrowed only when this is necessary because of state variables of the motor vehicle and/or of the gear-change transmission. The flow cross section may then also be narrowed to a differing extent.

[0045] The pump of the pressure-oil lubrication device may convey the lubricating oil out of a separate lubricating-oil tank instead of out of the transmission sump.

[0046] The embodiments described are merely illustrative refinements.

[0047] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. A combination of the features described for different embodiments is likewise possible. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Automated non-synchronized gear-change transmission and method for gear change in such a transmission

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