Method and transmission control apparatus for operating a multiple-speed vehicle transmission

Abstract

Disclosed is a method for operating a multi-gear vehicle transmission having a plurality of shifting elements (A, B, C, D, E) for engaging gears of the vehicle transmission. In a neutral gear, in which some of the shifting elements (A, B) are already actuated, a transmission input (1) is decoupled from a transmission output (2) of the vehicle transmission. In a driving gear the transmission input (1) is coupled to the transmission output (2) of the vehicle transmission by closing the shifting elements (A, B, C, D, E) associated with the driving gear, in order to propel the vehicle. With the neutral gear engaged a transmission condition is determined, and if a transmission condition with elevated drag losses exists, then in addition to the shifting elements (A, B) actuated in the neutral gear a shifting element (D) associated with a reversing gear of the vehicle transmission is also closed.

Claims

1. A method for operating a multi-gear vehicle transmission that includes shifting elements for engaging gears of the vehicle transmission, the method comprising: decoupling a transmission drive input from a transmission drive output of the vehicle transmission when in a neutral gear, wherein some of the shifting elements of a driving gear are already actuated; coupling the transmission drive input and the transmission drive output of the vehicle transmission while in the driving gear by closing the shifting elements associated with the driving gear, in order to propel the vehicle; determining whether a transmission condition with elevated drag losses exists when the neutral gear is engaged; and closing a shifting element of the vehicle transmission associated with a reversing gear if the transmission condition with elevated drag losses exists, in addition to the shifting elements actuated in the neutral gear.

2. The method according to claim 1, wherein determining whether the transmission condition with elevated drag losses exists includes taking into account one or more of (i) a transmission temperature, (ii) an operating duration of the vehicle transmission since starting a motor of a drive motor that is or can be coupled to the vehicle transmission, and (iii) a temperature model of the vehicle transmission.

3. The method according to claim 1, wherein, in all the driving gears of the vehicle transmission, at least or exactly three shifting elements are closed.

4. The method according to claim 3, further comprising: closing a further shifting element of the vehicle transmission in addition to the shifting elements actuated in the neutral gear, performed together with engaging a forward starting gear of the vehicle transmission or with engaging the reversing gear of the vehicle transmission.

5. The method according to claim 1, further comprising determining whether the vehicle is in a rolling condition when the transmission condition with elevated drag losses exists.

6. The method according to claim 5, wherein determining whether the vehicle is in the rolling condition includes taking into account one or more of (i) a drive output rotation speed of the vehicle transmission, (ii) a wheel rotation speed of the vehicle, and (iii) an acceleration of the vehicle.

7. The method according to claim 5, comprising: detecting a reverse rolling condition; opening the shifting element of the reversing gear; and closing a shifting element of a forward starting gear.

8. The method according to claim 7, further comprising: determining that the transmission condition with elevated drag losses still exists; detecting a forward rolling condition of the vehicle; opening the shifting element of the forward starting gear after closing the shifting element of the forward starting gear; and closing the shifting element of the reversing gear.

9. The method according to claim 1 comprising: engaging the neutral gear when an operating temperature of the vehicle transmission has been reached or exceeded.

10. A transmission control unit configured to carry out a method according to claim 1.

11. The transmission control unit of claim 10 comprising computer executable code that when executed by the transmission control unit carries out the method according to claim 1.

12. A vehicle transmission comprising the transmission control unit according to claim 11.

13. A motor vehicle comprising the vehicle transmission according to claim 12.

14. The method according to claim 1, wherein determining whether the transmission condition with elevated drag losses exists includes taking into account one or more of (i) a lubricant temperature of the vehicle transmission, (ii) an operating duration of the vehicle transmission since starting a motor of a drive motor that is or can be coupled to the vehicle transmission, and (iii) a temperature model of the vehicle transmission.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention is explained in greater detail with reference to figures, from which preferred embodiments and features of the invention emerge. The figures show:

(2) FIG. 1: A schematic representation of an automatic transmission of planetary design;

(3) FIG. 2: An example of a shifting scheme for the automatic transmission of FIG. 1;

(4) FIG. 3: A schematic representation of a further automatic transmission of planetary design; and

(5) FIG. 4: An example of a shifting scheme for the automatic transmission of FIG. 3.

DETAILED DESCRIPTION

(6) In a schematic representation, FIG. 1 shows the arrangement of shafts AN, AB, 1, 2, 3, 4, 5, 6, 7, 8 and planetary gearsets RS1, RS2, RS3, RS4 and shifting elements A, B, C, D, E of a preferred multi-gear vehicle transmission of planetary design. For greater clarity only the upper half of the vehicle transmission is shown. In particular, the lower half is a mirror image structure of this upper half. The drive input shaft AN is usually coupled to a drive motor of the vehicle or can be coupled to it by way of a separate clutch such as a hydrodynamic torque converter. The drive output shaft AB is usually coupled to drive wheels of the vehicle or can be coupled thereto.

(7) In FIG. 1 a transmission control unit 10 is also shown, which serves to actuate the shifting elements A, B, C, D, E of the transmission. Thus, the control unit 10 enables the shifting elements A, B, C, D, E to be selectively opened and closed. In that way the gear appropriate for the situation at the time or called for by a driver of the vehicle can be engaged. For this, appropriate information is fed into the control unit 10 via the input of the control unit. The control unit 10 processes that information and emits appropriate signals for actuating the shifting elements A, B, C, D, E via the output of the control unit.

(8) Among other things, the information T and the information n.sub.AB are fed into the control unit 10. The information T is a temperature signal which represents the transmission temperature. The temperature signal T is for example determined by a temperature sensor of the transmission. The information n.sub.AB is a rotation speed signal which represents the rotation speed of the drive output shaft AB.

(9) Usually, the shifting elements A, B, C, D, E are actuated by means of a pressure medium. For that purpose, with each shifting element A, B, C, D, E there is associated an actuating piston which can be acted upon individually by the pressure of the pressure medium. For that purpose, the control unit 10 actuates the valves associated with the actuating piston concerned. As the pressure medium, in the transmission shown in FIG. 1 the lubricant of the transmission (transmission oil) is usually used.

(10) The transmission can be shifted to a neutral gear, in which the drive input shaft AN is decoupled from the drive output shaft AB. For this an appropriate number of the shifting elements A, B, C, D, E are opened, specifically the shifting elements C, D, E. On the other hand some of the shifting elements A, B, C, D, E, specifically the shifting elements A and B associated with a starting gear, can already be actuated in the neutral gear in such manner that the shifting element A is preferably closed and the shifting element B preferably pre-filled. The driving gears of the transmission serve to propel the vehicle. In this case, eight forward gears and one reversing gear are available as driving gears. With the transmission shown in FIG. 1, in the driving gears in each case three of the five shifting elements A, B, C, D, E are always closed and the other two shifting elements A, B, C, E are open. To carry out a gearshift and thereby to carry out a shifting process, at least one of the previously open shifting elements A, B,C, D, and E of the automatic transmission is closed or engaged and at least one of the previously closed shifting elements A, B, C, D, and E is opened or disengaged.

(11) In the starting gear the vehicle is accelerated from rest or from very low speeds. Thus, the starting gear has a relatively high gear ratio. Depending on the load condition and the desired travel direction, suitable starting gears of the transmission in particular are the first gear (shifting elements A, B, C closed and D, E open), or the second gear (shifting elements A, B, E closed and C, D open) or the reversing gear (shifting elements A, B, D closed and C, E open).

(12) FIG. 2 shows an example shifting scheme of the automatic transmission of FIG. 1. In each gear three shifting elements A, B, C, D, E are closed and two shifting elements A, B, C, D, E are open. The shilling elements are in the form of brakes A, B and clutches C, D, E.

(13) The first forward gear is obtained by dosing the brakes A and B and the clutch C, the second forward gear by closing the brakes A and B and the clutch E, the third forward gear by closing the brake B and the clutches C and E, the fourth forward gear by closing the brake B and the clutches D and E, the fifth forward gear by, closing the brake B and the clutches C and D, the sixth forward gear by closing the clutches C, D and E, the seventh forward gear by closing the brake A and the clutches C and D and the eighth forward gear by closing the brake A and the clutches D and E. The reversing gear is obtained by closing the brakes A and B and the clutch D.

(14) Below, a preferred procedure for operating the above-described automatic transmission with the neutral gear engaged is explained. This procedure is carried out by the transmission control unit 10, which is correspondingly designed to do that. As already described above, the engagement of the neutral gear is called for, for example, by a driver of the vehicle or automatically.

(15) For the neutral gear at least the shifting elements C, D, E are opened. In this example the first gear serves as the starting gear. To engage the first gear, the shifting elements A, B, C must be closed and the shifting elements D and E open.

(16) When the neutral gear is engaged it is first determined whether the transmission is in a condition with elevated drag losses. This is done specifically in that the control unit 10 compares the current temperature T of the transmission with a threshold value. For example, the threshold value might be 40° C. If the temperature T determined is lower than that, the transmission is still relatively cold and the transmission lubricant correspondingly has high viscosity. Accordingly, the drag losses in the transmission can be expected to be relatively elevated so that the transmission is in an elevated drag-loss condition. If the temperature determined is higher the transmission is sufficiently hot and the transmission lubricant correspondingly has low viscosity. Accordingly, the drag losses in the transmission can be expected to be low so that the transmission is not in an elevated drag-loss condition.

(17) If a transmission condition with elevated drag losses has been recognized, then it is provided that in addition to the shifting elements A, B actuated in the neutral gear, the shifting element D for the reversing gear is also closed. The shifting element D is not one of the shifting elements A, B, C to be actuated for the first gear of the vehicle transmission. By closing the shifting element D of the reversing gear, a rotation speed direction at the drive output of the vehicle transmission is reversed, whereby the elevated drag losses in the vehicle transmission are reduced. By reducing the drag losses of the vehicle transmission, the torque present at the transmission output is also reduced, so that an undesired rolling condition of the vehicle is prevented.

(18) If the operating temperature of the vehicle transmission is reached before the driver or an automatic system calls for a driving gear, then the neutral gear is engaged in the vehicle transmission. In that case the clutches C, D, E are opened and the brake B is pre-filled, while the brake A is closed. If the vehicle transmission has reached its operating temperature, then the drag losses of the vehicle transmission with the neutral gear engaged are so low that the vehicle does not change to an undesired rolling condition.

(19) By virtue of the procedure described, an undesired rolling condition of the vehicle when the vehicle transmission is cold, i.e. when drag losses are elevated, can be reliably avoided.

(20) The method according to the invention can also be used with other multi-gear vehicle transmissions. For example, the method according to the invention can also be used with automatic transmissions which may be designed, for example, as 5-gear, 6-gear, 7-gear, 9-gear or 10-gear transmissions. The number of gearsets, the number of shifting elements and the number of shifting elements of the vehicle transmission closed in the driving gear can also be different.

(21) Thus, FIG. 3 shows a second example transmission structure of an example automatic transmission for a motor vehicle in which the method according to the invention can be used. A drive aggregate (not shown) can be coupled to a transmission input 15 of the automatic transmission and a drive output of the motor vehicle (not shown) can be coupled to a transmission output 16 of the automatic transmission.

(22) The automatic transmission shown in FIG. 3 is of planetary design and has a total of six shafts 17, 18, 19, 20, 21 and 22, wherein the shaft 19 is a transmission input shaft and the shaft 22 is a transmission output shaft. The shafts 17 to 22 of the automatic transmission of FIG. 3 are drive-connected on the one hand by gearsets 23, 24, and 25 and on the other hand by transmission-internal shifting elements A2, B2, C2, D2, and E2. The shifting elements A2, B2, C2, D2, and E2 are actuated by a transmission control unit (not shown here).

(23) The automatic transmission shown in FIG. 3 has three gearsets 23, 24, and 25 and five shifting elements A2, B2, C2, D2, and E2, the shifting elements A2 and B2 being in the form of clutches while the shifting elements C2, D2, and E2 are in the form of brakes. With the automatic transmission shown in FIG. 3 a total of six forward gears and one reversing gear can be engaged, and in each of these gears two shifting elements are closed and three shifting elements are open. To carry out a gearshift and thus a shifting process, at least one of the previously open shifting elements A2, B2, C2, D2, and E2 of the automatic transmission is closed or engaged and at least one of the previously closed shifting elements A2, B2, C2, D2, and E2 is opened or disengaged. The transmission structure shown in FIG. 3 is presented purely as an example. In addition to the frictional shifting elements interlocking shifting elements can also be present.

(24) FIG. 4 shows an example shifting scheme for the automatic transmission according to FIG. 3. In each gear two of the shifting elements A2, B2, C2, D2, and E2 are closed and three of the shifting elements A2, B2, C2, D2, and E2 are open. The shifting elements are in the form of clutches A2, B2 and brakes C2, D2, and E2.

(25) The first forward gear is obtained by closing the clutch A2 and the brake E2, the second forward gear by closing the clutch A2 and the brake D2. the third forward gear by closing the clutch A2 and the brake C2, the fourth forward gear by closing the clutches A2 and B2, the fifth forward gear by closing the clutch B2 and the brake C2, and the sixth forward gear by closing the clutch B2 and the brake D2. The reversing gear is obtained by closing the brakes C2 and E2.

(26) For the neutral gear at least the shifting elements A2, B2, C2, and D2 are opened. In this example, as the starting gear the first gear is again used. To engage the first gear the shifting elements A2 and E2 have to be closed while the shilling elements B2, C2, and D2 are open.

(27) When the neutral gear is engaged, it is first of all determined whether the transmission is in the condition of elevated drag losses. Whether the transmission is in the condition of elevated drag losses can be determined as already described above.

(28) If a condition with elevated drag losses has been recognized, then it is provided that the shifting element C2 of the reversing gear of the vehicle transmission is closed in addition to the shifting element E2 actuated in the neutral gear. The shifting element C2 is not one of the shifting elements A2, E2 to be actuated for the first gear of the vehicle transmission. By closing the shifting element C2 of the reversing gear, a torque direction at the drive output of the vehicle transmission is reversed, whereby the elevated drag losses of the vehicle transmission are reduced. By reducing the drag losses of the vehicle transmission, the torque at the drive output of the transmission is also reduced, whereby an undesired rolling condition of the vehicle is prevented.

(29) If the operating temperature of the vehicle transmission has been reached before the driver or an automatic system calls for a driving gear, then as already described above the neutral gear can be engaged in the vehicle transmission. For this the clutches A2, B2 and the brakes C2, D2 are opened, while the brake E2 can be pre-filled or closed. If the vehicle transmission has reached its operating temperature, then the drag losses in the vehicle transmission with the neutral gear engaged are so low that the vehicle does not change to an undesired rolling condition.

(30) By virtue of the method proposed an undesired rolling condition of the vehicle when the vehicle transmission is cold, i.e. in a transmission condition with elevated drag losses, can be reliably avoided.

INDEXES

(31) 1 Shaft

(32) 2 Shaft

(33) 3 Shaft

(34) 4 Shaft

(35) 5 Shaft

(36) 6 Shaft

(37) 7 Shaft

(38) 8 Shaft

(39) 10 Transmission control unit

(40) 15 Transmission input

(41) 16 Transmission output

(42) 17 Shaft

(43) 18 Shaft

(44) 19 Shaft

(45) 20 Shaft

(46) 21 Shaft

(47) 22 Shaft

(48) 23 Gearset

(49) 24 Gearset

(50) 25 Gearset

(51) A Shifting element/Brake

(52) B Shifting element/Brake

(53) C Shifting element/Clutch

(54) D Shifting element/Clutch

(55) E Shifting element/Clutch

(56) AN Drive input shaft

(57) AB Drive output shaft

(58) GG Housing

(59) RS1 Planetary gearset

(60) RS2 Planetary gearset

(61) RS3 Planetary gearset

(62) RS4 Planetary gearset

(63) SO3 Sun gear

(64) A2 Shifting element/Disk clutch

(65) B2 Shifting element/Disk clutch

(66) C2 Shifting element/Disk brake

(67) D2 Shifting element/Disk brake

(68) E2 Shifting element/Disk brake