EP4248109A1

EP4248109A1 - Method for heating a gearbox

Info

Publication number: EP4248109A1
Application number: EP21794368.7A
Authority: EP
Inventors: Harald Fischer
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2020-11-20
Filing date: 2021-10-18
Publication date: 2023-09-27
Also published as: DE102020214635B4; US11994207B2; WO2022106129A1; DE102020214635A1; US20230407960A1; CN116507831A

Abstract

The invention relates to a method for heating a gearbox (3) with a torque converter (11), wherein different gears (R1, R2, R3, V1, V2, V3) can be engaged by selectively actuating clutches (K1, K2, K3, KR, KV), wherein the gearbox (3) is blocked on the output side, as a result of which a turbine shaft (12) of the torque converter (11) is fixed while a drive power is introduced into the gearbox (3) by means of a drive element (2), characterised in that the blocking is implemented by actuating the clutches (K1, K2, K3, KR, KV) in such a way that two mutually different gears (R1, R2, R3, V1, V2, V3) of one direction of travel are engaged simultaneously.

Description

Method of heating a gearbox

The present invention relates to a method for efficiently heating a transmission and the transmission oil contained therein. The transmission can be designed, for example, as an automatic/powershift transmission, dual-clutch transmission, automated manual transmission (for example with a countershaft design) or (hydrostatic-mechanical) power-split transmission (CVT). The method is primarily intended for transmissions in work machines, but can also be used for transmissions in other vehicles.

At lower temperatures, the shifting comfort and efficiency of a transmission can be significantly reduced due to the viscosity of the transmission oil. Furthermore, providing a sufficient amount of transmission oil at locations with a need for lubricating oil (e.g. bearings, shifting elements and gears) is made more difficult. An inhomogeneous temperature distribution in the transmission is also disadvantageous in terms of wear and service life of the components.

In order to counteract this, it is known to provide a warm-up function for warming up a transmission, in particular after a cold start. For example, US 2016/0084371 A1 discloses a heating function for an automatic transmission or the transmission oil contained therein in connection with a method for checking the fluid level. The engine speed is increased and an output-side turbine shaft of a torque converter of the transmission is rotationally fixed against the transmission housing by engaging a clutch and a brake.

The object of the present invention is to be seen as providing an improved method for heating a transmission and the transmission oil contained therein.

The object is achieved with the method according to the invention. In this case, clutches of a transmission with a torque converter are selectively actuated in order to engage different gears. Under an engaged gear is to be understood that a Transmission ratio between transmission input and transmission output is set. As part of the procedure, the transmission is blocked on the output side. This means that a turbine shaft of the torque converter is stationary while drive power is introduced into the transmission through an input element. As a result, power loss in the form of heat is generated in the torque converter. The drive element can be designed as an internal combustion engine or as an electric machine. Hybrid designs are also conceivable, in which drive power is generated by an internal combustion engine and/or an electric machine. According to the invention, the blocking of the transmission is implemented in that two different gears in one direction of travel are engaged at the same time. Depending on the design of the transmission, it can have several forward and reverse gears. Accordingly, the method can be carried out in the same way when different forward gears or reverse gears are engaged at the same time.

In a first step of the method, the relevant clutches are actuated to set two different gears. The clutches can be designed as positive or frictional shifting elements. In particular, these are actuated hydraulically or (electro-) mechanically. In the case of hydraulic actuation, pressure is applied to the clutches for actuation, as a result of which they are closed and a torque or rotary movement can be transmitted. For example, first and second gear can be engaged. As an option to the output-side blocking by means of the clutches, a service and/or parking brake of the vehicle and/or a parking lock of the transmission can also be actuated. However, by blocking by engaging two different gears, a higher input torque can be supported, so that a higher drive power can be introduced, a higher power loss can be generated and consequently a higher heat input can be brought about. As a result, the transmission heats up faster and more efficiently. The clutches are typically controlled by a transmission control unit, so that the method can also be carried out by this control unit. In a second step, a directional clutch is actuated. Typically, the transmission has two direction of travel clutches, one for forward travel and one for reverse travel. This allows the same number of forward and reverse gears to be displayed. After the clutches have been actuated in the manner described above, a speed of the drive element is increased in a third step, in particular raised from an idle speed to a warm-up speed.

After the set speed has been maintained for a defined period of time, it is lowered again in a fourth step before the previously closed direction-of-travel clutch is opened in a fifth step. The duration of the increase in the speed of the drive element can be specified in a fixed manner, or assigned individually using other parameters. In particular, the duration of the increase in speed must be limited in order to avoid overheating. In a sixth step, a flushing process is initiated, by means of which the open clutches are flushed and circulation of the transmission oil is achieved. This leads, among other things, to a homogeneous heat distribution.

At the end of the process, a sensor can measure the temperature directly or indirectly, with a check being carried out to determine whether a defined target temperature has been reached or even exceeded. Then the heating process would be terminated. If the target temperature has not been reached, steps two to six are repeated. The sequence of steps two to six corresponds to a cycle.

In a development, the cycle duration can vary, in particular can be shortened with an increasing number of cycles. The cycle duration can also depend on the determined temperature of the transmission. Also, the duration could be shortened with increasing temperature. However, a fixed number of cycles can also be specified, and a number of cycles can also result from a temperature at the start of the method. When the target temperature is reached at the end of the relevant cycle, in a seventh step, the relevant directional clutch is also opened and the method is ended.

Advantageously, two adjacent gears are engaged simultaneously for the blocking of the transmission on the output side. For example, this is the first and second gear. But any other combination is also conceivable. Engaging adjacent gears has the advantage that similarly high torques can be supported or transmitted. The further the engaged gears are apart (e.g. first gear and third gear), the greater the imbalance in the torque that can be supported.

Monitoring of an output speed is optionally provided. This is to ensure that the vehicle does not move in an unacceptable manner during the transmission heating process. Accordingly, no speed may occur on the output side. As soon as an (inadmissible) speed is detected, the method is aborted and the transmission is switched to a safe state. To do this, either the actuated travel direction clutch and/or all clutches can be opened.

The method can be started either by manual input from an operator or automatically. Ambient and/or transmission parameters (temperature) can be taken into account in particular for an automated initiation of the method. When the vehicle is started, it can also be provided that the operator is informed that he should initiate the method.

According to another aspect of the present invention, a vehicle is included with a drive member and a transmission with clutches and a torque converter. The transmission also has a control device, for example a transmission control unit. The control device is suitable and set up to carry out the method according to the invention. The control device can be designed separately, integrated in a transmission control unit, an engine control unit or a higher-level control unit. The present invention is explained in more detail with reference to the following figures. show:

FIG. 1: a diagram of the time sequence when the method is carried out; FIG. 2: a schematic representation of a transmission;

FIG. 3: an embodiment of a vehicle with a control device for carrying out the method;

FIG. 4: a switching matrix for actuating the transmission according to FIG. 2;

FIG. 5: a schematic representation of the steps of the method.

FIG. 1 shows a time sequence of the method according to the invention for heating a transmission 3 in a greatly simplified diagram that is not true to scale. A time t is plotted on the abscissa, while a speed n and a pressure p are specified on the ordinate. Furthermore, the profile of the pressure pK12 is shown by broken lines, this corresponding to the actuating pressure of a first and second clutch K1, K2. These are applied simultaneously and with the same pressure pK12. The progression of the rotational speed nA of a drive element 2 is shown with broken lines. The progression of the pressure pKV is indicated with a continuous line, this corresponding to the actuation pressure of the forward (travel direction) clutch KV. In the embodiment of the method shown here, a rearward (direction of travel) clutch KR remains in an unactuated state, and instead of the forward clutch KV, it could be operated in the same way to carry out the method. According to the idea of the invention, the transmission 3 is now blocked on the output side by actuating clutches K1, K2, K3 in such a way that a power loss in the form of heat is generated in a torque converter 11 by the drive power introduced, which heats up the transmission 3.

At a point in time tO, the drive element 2 is in a deactivated state, which is why the speed nA assumes the value nO. At time t1, the drive element 2 starts, whereupon the rotational speed n1 is reached (in leaps and bounds). This corresponds, for example, to the idling speed of the drive element 2 insofar as this is designed as an internal combustion engine. Until time t2 the pressures pKV and pK12 show the pressure pO. Consequently, the first and second clutches K1, K2 and the clutch KV are not subjected to pressure.

At time t2, the first and second clutches K1, K2 are pressurized, with the pressure increasing at a first gradient. At time t3, the pressure pK12 reaches the value p1, which corresponds to a fully engaged clutch K1, K2. Thus, the transmission of a maximum torque is possible. When the value p1 for the pressure pK12 is reached, the clutch KV is pressurized. As a result, the pressure pKV increases. A time offset (not shown here) can also be provided between reaching the value p1 for the pressure pK12 and the beginning of the pressure build-up in relation to the pressure pKV, so that this does not occur at exactly the same point in time t3. The pressure is applied with a second gradient, which can be different from or identical to the first gradient. At time t4, the pressure pKV also reaches the value p1. At the same time, or optionally with a time offset not shown here, the speed nA increases from the value n1 to the value n2 at time t5. This is done using a third gradient, which is typically different from the first and second gradients. The speed nA remains at the value n2 up to the point in time t6 and falls back to the value n1 in an interval between the points in time t6 and t7. This can be done with the negative third gradient or any other gradient. At time t7, the pressure pKV is then reduced until it has again assumed the value pO at time t8. This can be done with the second gradient, or with any other gradient. Optionally, a time offset can also be provided here. Up to time t9, the speed nA remains at the value n1 and the pressure pKV at the value pO. A flushing process takes place in this interval in order to distribute the heated transmission oil in the transmission 3 and flush the clutches K3, KV, KR.

The interval between t3 and 9 describes a first cycle I for heating the transmission 3. If the target temperature for the transmission 3 or the transmission oil has not yet been reached, the first cycle I is followed by an identical second cycle II and possibly a third cycle III on. The pressure pKV increases with time From point t9 to point in time t10 as in the first cycle I, at point in time t10 the speed nA is increased until point in time t11. In the interval between times t12 and t13, the speed nA is reduced and in the interval from time t13 to time t14, the pressure pKV falls again to the value pO. This is followed by a flushing process up to time t15.

The sequence of the third cycle III corresponds to the first and second cycle I, II. At the time t15 the pressure pKV increases and at the time t16 the speed nA. Speed nA and pressure pKV remain unchanged up to time t18, with speed nA dropping again to value n1 in the interval from t18 to t19 before pressure pKV drops again to value pO in interval t19 to t20. The third cycle III ends when the scavenging process is completed at time t21.

In the example shown here, the target temperature was reached at the end of the third cycle III. Since it is not necessary to carry out another cycle I, II, III, the pressure pK12 drops to the value pO in the interval from t21 to t22. The pressure pK12 kept the value p1 constant from the time t3 to the time t21. At time t22 the method is complete. The regular operation of the vehicle 1 can be started.

For example, an increase of 0.8 bar/s can be provided for the first and second gradient, so that a nominal pressure of p1=16 bar is reached after approx. 20 s. Furthermore, for example, n1=800 rpm and n2=1,500 rpm can be provided as speed values.

In a development not shown here, provision can also be made for the pressure to be applied to the clutch KV not only at the point in time t3, ie when the value p1 for the pressure pK12 is reached, but at an earlier point in time. In particular, this could take place halfway through the interval between times t2 and t3. Because already at this point in time, the first and second clutches K1, K2 are already subjected to a pressure which is sufficient to counteract the torque transmitted by the clutch KV. When the vehicle 1 is designed with an electric machine as the drive element 2, the speed n1 can also be identical to the speed n0. In other words, no idling speed has to be started up or maintained. Otherwise, the procedure is to be carried out in the same way with this adjustment.

FIG. 2 shows a transmission 3 in a schematic representation. A rotational movement or torque is introduced by the drive element 2 (not shown) via a drive shaft 4. In the present case, the transmission 3 has a torque converter 11, which is supported on a housing G and, with a turbine shaft 12, initiates the rotational movement into the transmission 3 for translation. A gear wheel Z1 is connected in a torque-proof manner to the turbine shaft 12 . The gear Z1 meshes with a gear Z2, which is rotatably mounted on a shaft W1. The gear wheel Z2 can be connected via the clutch KR to a gear wheel Z4 that is rotatably arranged on the shaft W1. The gear wheel Z4 meshes with a gear wheel Z5, which is illustrated by the arrow represented by dashed lines. The gear wheel Z5 is arranged on a shaft W2 in a torque-proof manner. A gear wheel Z3 is also arranged rotatably on the turbine shaft 12 and also meshes with the gear wheel Z5. The gear wheel Z3 can be connected to the gear wheel Z1 via the clutch KV. In other words, a rotational movement is transmitted to the gear wheel Z5 either when the clutch KR is actuated or when the clutch KV is actuated.

A gear wheel Z6 is also arranged on the shaft W2, but is rotatable in comparison to the gear wheel Z5. This gear wheel can be connected to the gear wheel Z5 via the clutch K1. On an output shaft 5, a gear wheel Z7 can be rotated and gear wheels Z8 and Z10 are arranged in a torque-proof manner. The gear wheel Z7 and the gear wheel Z8 can be connected to one another via the clutch K2. Gear Z7 meshes with gear Z5, while gear Z8 meshes with gear Z6.

The gear wheel Z7 further meshes with a gear wheel Z9, which is arranged on a shaft W3 in a rotationally fixed manner. Furthermore, a gear wheel Z11 is rotatably arranged on the shaft W3 and meshes with the gear wheel Z10. The gear wheel Z11 and the gear wheel Z9 can be connected to one another via the clutch K3. The gears Z1 to Z11 are typically designed as straight or helical spur gears. A non-rotatable arrangement means that the relevant gears Z1, Z2, Z5, Z8, Z9, Z10 are designed as fixed gears and thus rotate at the same speed in the same direction of rotation of the relevant shaft 12, 5, W1, W2, W3 . A rotatable arrangement, on the other hand, means that the relevant gears Z3, Z4, Z6, Z7, Z11 are designed as idler gears, so that a relative movement between the idler gears and the relevant shafts 12, 5, W1, W2, W3 is possible. In other words, loose wheels and the relevant shafts 12, 5, W1, W2, W3 can rotate freely with respect to one another. By actuating a clutch K1, K2, K3, KV, KR, a non-rotatable connection of the idler gears to a shaft 12, 5, W1, W2, W3 or a fixed gear can be produced.

FIG. 3 shows, in a highly simplified representation, an embodiment of a vehicle 1 in which the method according to the invention is implemented. In the present case, the vehicle 1 is designed as a working machine, in particular as a wheel loader. The application of the method according to the invention is not limited to wheel loaders or work machines, rather the implementation is described here in more detail only as an example.

The vehicle 1 has a drive element 2 and a transmission 3 . The drive element 2 and the transmission 3 are operatively connected to one another via a drive shaft 4 . In other words, a rotational movement or a torque of the drive element 2 is introduced into the transmission 3 via the drive shaft 4 . The torque or the rotational movement of the drive element 2 is stepped up or down by the transmission 3 and transmitted to a vehicle axle 7 , 8 by means of the output shaft 5 in accordance with the gear ratio set in each case. As a result, wheels 6 of the vehicle axles 7, 8 are driven. One or more vehicle axles 7, 8 can be driven. The vehicle 1 also has an attachment 9, which in the present case is designed as a lifting frame with a shovel.

The vehicle 1 has in the embodiment shown here a separate control device 10, which transmits signals to the drive element 2 and the Transmission 3 is connected. The signal-transmitting connection is shown in Figure 3 by dotted lines. Alternatively, the control device 10 can also be integrated in the transmission 3 or the drive element 2, for example in a transmission or engine control unit. The method according to the invention is carried out in the control device 10 and corresponding signals for controlling the drive element 2 and the transmission 3 are generated and sent. In the same way, signals, for example relating to an actuation state or relating to device-specific parameters, can be transmitted from the drive element 2 and/or the transmission 3 to the control device 10 and processed by the latter.

FIG. 4 shows a switching matrix for actuating the transmission 3. An actuated clutch KV, KR, K1, K2, K3 is represented by an X. By alternately actuating the clutches KV, KR, K1, K2, K3, a total of six different gears V1, V2, V3, R1, R2, R3 can be realized by the transmission 3. These are divided into three forward gears V1, V2, V3 and three reverse gears R1, R2, R3. For the provision of the first forward gear V1, the forward (travel direction) clutch KV and the first clutch K1 are in an actuated state. The second forward gear V2 is realized by actuating the forward (travel direction) clutch KV and the second clutch K2. The third forward gear V3 is implemented when the forward (direction of travel) clutch KV and the third clutch K3 are actuated.

In the same way, three reverse gears R1, R2, R3 can be represented, in which case, in analogy to the forward gears V1, V2, V3, the rear (direction of travel) clutch KR is actuated with the relevant clutch K1, K2, K3. As a result, a (direction of travel) clutch KV, KR and a (gear) clutch K1, K2, K3 are simultaneously in an actuated state for the representation of a gear V1, V2, V3, R1, R2, R3.

FIG. 5 shows a schematic representation of steps S1, S2, S3, S4, S5, S6, S7 of the method according to the invention. In this case, in a first step S1, the clutches K1, K2, K3 are actuated to set two different gears R1, R2, R3, V1, V2, V3. In a second step S2, a clutch KR, KV operated in one direction, for example the clutch KV. In a third step S3, the speed nA of the drive element 2 is increased until it is lowered again in a fourth step S4. In a fifth step S5, the clutch KR, KV actuated in the second step S2 is opened in one direction of travel, and a flushing process is then initiated in a sixth step S6. The second to sixth steps S2, S3, S4, S5, S6 represent a cycle I, II, III in the sense of the disclosure relating to FIG. 1. Steps S2 to S6 are repeated cyclically until a target temperature of the transmission (3) is reached. When the target temperature is reached after completion of the relevant cycle I, II, III, the clutches K1, K2, K3 actuated in the first step S1 are opened in a seventh step S7. After the seventh step S7 has been carried out, the method is complete. The regular operation of the vehicle 1 can be started.

reference sign

1 vehicle 2 drive element 3 gearbox 4 input shaft 5 output shaft 6 wheel

7, 8 vehicle axis

9 attachment

10 control device

11 torque converter

G housing

I, II, III (warm-up) cycle KR, KV (direction) clutch K1, K2, K3 (speed) clutch n, nO, n1, n2 speed nA speed drive element p, pO, p1 pressure pK12 pressure K1, K2 pKV pressure KV

R1 , R2, R3 (reverse) gear S1 - S7 (process) steps tO - 122 point in time V1 , V2, V3 (forward) gear W1 - W3 shaft Z1 - Z1 1 gear

Claims

patent claims

1 . Method for heating a transmission (3) with a torque converter (1 1), wherein by selectively actuating clutches (K1, K2, K3, KR, KV) different gears (R1, R2, R3, V1, V2, V3) are engaged whereby the transmission (3) is blocked on the output side, as a result of which a turbine shaft (12) of the torque converter (11) is stationary while a drive element (2) introduces drive power into the transmission (3), characterized in that the blocking is characterized is implemented in that the clutches (K1, K2, K3, KR, KV) are actuated in such a way that at the same time two different gears (R1, R2, R3, V1, V2, V3) are engaged in one direction of travel.

2. The method according to claim 1, characterized in that

- In a first step (S1) clutches (K1, K2, K3) are actuated for setting two different gears;

- In a second step (S2), a clutch (KR, KV) is actuated in one direction;

- In a third step (S3), a speed (nA) of the drive element (2) is increased.

3. The method according to claim 2, characterized in that

- In a fourth step (S4), the speed (nA) is reduced;

- In a fifth step (S5), the clutch (KR, KV) actuated in the second step (S2) is opened in one direction of travel;

- In a sixth step (S6), a flushing process is initiated.

4. The method according to claim 3, characterized in that the second to sixth steps (S2, S3, S4, S5, S6) are repeated cyclically until a target temperature of the transmission (3) is reached.

5. The method according to claim 4, characterized in that when the target temperature is reached in a seventh step (S7), the clutches (K1, K2, K3) actuated in the first step (S1) are opened.

6. The method according to any one of the preceding claims, characterized in that two adjacent gears are inserted simultaneously for the blocking.

7. The method according to any one of the preceding claims, characterized in that a monitoring of an output speed is provided, with the transmission (3) being transferred to a safe state and the heating process being aborted as soon as an impermissible speed value is detected on an output shaft (5). becomes.

8. The method according to any one of the preceding claims, characterized in that the method is started automatically by manual input and/or.

9. Vehicle (1) with a drive element (2) and a transmission (3) with clutches (K1, K2, K3, KR, KV) and a control device (10), the control device (10) being suitable and set up for this purpose, to carry out the method according to any one of the preceding claims.