A motor vehicle having an automatic transmission with a fixed gear ratio and a power split gear ratio, and at least two driving motors.

Abstract

The present invention provides a vehicle having at least two drive motors, at least one of which is an electric machine, a high-voltage battery, an automatic transmission having at least one fixed transmission ratio and at least one power split transmission ratio and / or series transmission ratio for changing the transmission ratio to the at least one fixed transmission ratio, and an electronic control unit for controlling the internal combustion engine and the electric machine during the period from engagement of a shift element to loading of the shift element as part of the transmission ratio change: - at a first time point, when the engaging shifting element can be considered to be at least in a tooth-on-tooth position, it is loaded with a set torque gradient up to a second time point, - during the set waiting time, the set torque is limited to the maximum allowable torque from the second point in time to the third point in time, After the waiting time has elapsed or when the engaged state is recognized, the engaging switching element is further loaded with a preset torque gradient. The torque transition can be set as described above.

Description

[Technical Field]

[0001] The present invention relates to a motor vehicle having at least two driving motors, at least one of which is an electric machine, a high-voltage battery, an automatic transmission having at least one fixed gear ratio (unchangeable gear ratio) and at least one power split or series gear ratio that performs gear ratio adjustment starting from the at least one fixed gear ratio (unchangeable gear ratio), and further having an electronic control unit. [Background technology]

[0002] Automatic transmissions for automobiles are known. Furthermore, automatic transmissions for hybrid electric vehicles (HEVs), which have at least one electric machine in addition to an internal combustion engine for drive, are also known. Modern automatic transmissions for HEVs (hybrid transmissions) are usually based on existing automatic transmissions. The electric machine for electrification is often located between the internal combustion engine and the transmission (so-called P2 hybrids). However, this type of hybridization does not provide any benefits to the transmission itself.

[0003] A suitable transmission for hybridization is, for example, a load-shiftable automatic transmission (powershift transmission) that provides various fixed gear ratios via friction-engaged shift elements. In these transmissions, at least one shift element is operated in a slipping motion during gear changes. The frictional work generated during the slipping motion is converted into heat, which must be removed from the friction-engaged shift element via a sufficient flow of cooling oil. Furthermore, friction-engaged shift elements generate significant drag losses when disengaged. The shift elements are usually hydraulically controlled. To ensure that they can transmit power when engaged, the friction plates of the shift elements must be continuously pressed against each other with a correspondingly high hydraulic pressure. The hydraulic pump required for this is used both for cooling and for operating the shift elements. However, its operation requires a constant amount of electrical power, which reduces overall efficiency.

[0004] According to the subject matter of Patent Document 1, an automatic transmission includes an internal combustion engine, at least two fixed gear ratios, three transmission shafts, a planetary gear mechanism, two shifting elements, and a variator. Here, a first side of the variator can be coupled to the first transmission shaft to transmit torque, and a second side of the variator can be coupled to the planetary gear mechanism via the second transmission shaft to change the gear ratio. This means that the second side of the variator, together with the internal combustion engine and the driven parts of the automatic transmission, is in a three-axis motion, and the second side of the variator acts on the internal combustion engine to change the gear ratio via the planetary gear mechanism. Here, the variator allows for stepless (continuous) gear ratio change. Therefore, further gear ratios, in particular any intermediate state between the fixed gear ratios, can be set independently of the fixed gear ratios. The variator is preferably formed by two electric machines. In this case, one electric machine operates as a generator and the other as a motor. By temporarily converting mechanical energy into electrical energy, the rotational speeds of the two electric machines can be decoupled, so that both electric machines can provide a variator function. The planetary gear mechanism can be a planetary-type planetary gear mechanism.

[0005] In a series transmission, there is no mechanical connection of the internal combustion engine to the vehicle drive shaft, and the drive power of the internal combustion engine is converted 100% to electrical power by the first electric machine and converted back to mechanical drive power at the drive shaft by the second electric machine. In contrast to a power split transmission, the variator transmits the full drive power in a series transmission. Since series to fixed ratio conversions and power split to fixed ratio conversions are equivalent within the scope of this invention, the following description of the invention will be given with respect to power split transmissions, but the same applies to series transmissions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102017217133 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to improve hybrid vehicles with automatic transmissions of the type mentioned at the outset with regard to the gear ratio change. [Means for solving the problem]

[0008] This problem is solved by the features of the independent claims. Advantageous developments are the subject of the dependent claims.

[0009] The invention relates to a motor vehicle having at least two drive motors, at least one of which is an electric machine, a high-voltage battery, an automatic transmission with at least one fixed transmission ratio (fixed transmission ratio) and at least one power split transmission (E-CVT) and / or one series transmission with a transmission ratio change to the at least one fixed transmission ratio, and an electronic control unit with a functional module for controlling the internal combustion engine and the electric machine as part of the transmission ratio change between the engagement of the shifting element of the (new) fixed transmission ratio and the loading of the shifting element of the (new) fixed transmission ratio in such a way that the torque curve can be set as follows: - at a first time point, the engaging shifting element can be considered to be at least in a tooth-on-tooth position, and is loaded with a set torque gradient up to a second time point, - during the set waiting time, the set torque is limited to the maximum allowable torque from the second point in time to the third point in time, After the waiting time has elapsed or when the engaged state is recognized, the engaging shifting element is further loaded with a preset torque gradient, preferably until the torque at the fixed gear ratio under full load is achieved.

[0010] For example, it is relevant to start with a power-split transmission (E-CVT) and go to just one fixed transmission ratio.

[0011] In particular, the invention relates to a motor vehicle having an automatic transmission with an internal combustion engine, at least one electric machine, at least two fixed gear ratios and a variator for changing the gear ratio between these two fixed gear ratios, the variator having, for example, two electric machines, although one electric machine may also be sufficient, in which case the variator consists of the electric machine and a high-voltage battery.

[0012] The motor vehicle according to the invention further comprises an electronic control unit that is configured to be able to implement a method for secure engagement of a positively engaging shifting element as part of a gear change in a DHT transmission.

[0013] The present application is based on the following ideas:

[0014] The use of positively coupled shifting elements in DHT drives is motivated by minimizing drag and actuation losses in the transmission.

[0015] However, positively locking shifting elements have the disadvantage that they can only achieve a positive connection in a small angular range over the torsional rotation (relative rotation) of the two clutch elements, which means that they are in a so-called tooth-on-tooth position over the remaining angular range of torsional rotation.

[0016] Usually, attempts are made to minimize this drawback by the geometric design of the clutch elements, for example using fang or sloping roof shapes, where the torsional rotation of the two clutch elements relative to each other is ensured by the force of the actuator.

[0017] However, the geometric solution still masks the problem of tooth-on-tooth position to a certain extent and has the additional drawback of making the working path itself larger.

[0018] However, positive engagement is essential to avoid excessive rotational speed differences due to delayed engagement of the shifting elements, due to the torque impulse occurring on engagement, which increases in proportion to the rotational speed difference being reduced, and which can cause comfort problems and damage to materials when limiting values ​​depending on the gears and shifting elements are exceeded.

[0019] The invention therefore proposes a functional solution which makes it possible to engage or connect form-locking switching elements, preferably with blunt switching elements, but also with any type of form-locking switching element.

[0020] Due to the actuation force of the actuator of the shifting element, friction forces and the resulting friction torques also act in the tooth-on-tooth position, which prevent the two clutch elements from torsionally rotating. In contrast to conventional transmissions, this friction torque can be overcome precisely in the DHT.

[0021] By controlling the internal combustion engine and electric machine so that a transmitted torque just slightly exceeds the friction torque acts on the switching element to be engaged, a torsional rotation of the clutch element occurs, and the switching element can be engaged or connected.

[0022] The difference between the transmitted torque and the acting friction torque must not exceed a certain value, which depends on the gear to be engaged, both for reasons of comfort and for reasons of material damage.

[0023] In order to be able to carry out the engagement process in a controlled manner from the tooth-on-tooth position, it is proposed to start loading the engaging switching element already in the tooth-on-tooth position, which will increase the torque so that it overcomes the friction torque.

[0024] In order to limit the difference between the transmitted torque and the acting friction torque, once a predetermined value, which can be parameterized or applied, has been exceeded, the torque generation in the switching element is stopped or at least slowed down, causing the switching element to rotate torsionally and ultimately engage below the level of the applied torque in the switching element and the level of the rotational speed difference.

[0025] After the applied time period has elapsed or when the engaged state is recognized, the original torque generation continues at the shifting element that is now fully engaged.

[0026] In order to minimize or reduce the friction torque generated by the actuator from the value of static friction to the value of sliding friction, a pulsing operation of the switching element actuator is preferably carried out.

[0027] Here, the pulse frequency is preferably applied or parameterized so that the actuator force continues to reach its required value on average, but at the lowest point in the course of its change, drops to 70%, 50%, 30% or even 0% of the required value.

[0028] The present invention will now be described with reference to the drawings. [Brief explanation of the drawings]

[0029] [Figure 1]1 shows state 1 of the overall shift flow during a gear change from a first fixed gear ratio to a second fixed gear ratio using an automatic transmission according to the present invention. FIG. [Figure 2] 1 shows a schematic diagram of the main components of a vehicle or transmission according to the invention and their states during state 1 of the overall shifting flow. FIG. [Figure 3] 1 shows state 2 of the overall shift flow during a gear change from a first fixed gear ratio to a second fixed gear ratio using an automatic transmission according to the present invention. FIG. [Figure 4] 1 is a diagram showing a schematic representation of the main components of a vehicle or transmission according to the invention and their states during state 2 of the overall shifting flow. [Figure 5] 3 shows state 3 of the overall shift flow during a gear change from a first fixed transmission ratio to a second fixed transmission ratio using the automatic transmission according to the present invention. FIG. [Figure 6] 1 shows a schematic diagram of the main components of a vehicle or transmission according to the invention and their states during state 3 of the overall shifting flow. FIG. [Figure 7] 4 shows state 4 of the overall shift flow during a gear change from a first fixed transmission ratio to a second fixed transmission ratio using an automatic transmission according to the present invention. FIG. [Figure 8] 1 shows a schematic diagram of the main components of a vehicle or transmission according to the invention and their states during state 4 of the overall shifting flow. [Figure 9] 5 shows state 5 of the overall shift flow during a gear change from a first fixed transmission ratio to a second fixed transmission ratio using an automatic transmission according to the present invention. FIG. [Figure 10] 1 shows a schematic diagram of the main components of a vehicle or transmission according to the invention and their states during state 5 of the overall shifting flow. [Figure 11] 6 shows states 6 and 7 of the overall shift flow during a gear change from a first fixed ratio to a second fixed ratio using an automatic transmission according to the present invention. FIG. [Figure 12]1 shows a schematic diagram of the main components of a vehicle or transmission according to the invention and their states in states 6 and 7 of the overall shifting flow. [Figure 13] FIG. 1 shows the basic intermediate steps of the invention between states 5 and 6 of the overall shifting flow during a gear change from a first fixed transmission ratio to a second fixed transmission ratio using an automatic transmission according to the invention. [Figure 14] 3 shows a schematic diagram of the torque profile produced by the present invention in the switching element in question; DETAILED DESCRIPTION OF THE INVENTION

[0030] Figure 1 shows State 1, which is the initial state when first gear (fixed gear ratio G1) is engaged, before a gear change is commanded. A gear change is then commanded in the electronic control unit SG by an appropriate input signal.

[0031] FIG. 2 shows the most important components of the present invention, and this is also true for FIGS.

[0032] FIG. 2 shows a hybrid vehicle, which includes a DHT automatic transmission (hybrid-specific transmission), an internal combustion engine VM, a first electric machine EMA, a second electric machine EMB, a high-voltage battery HVS, and an electronic control unit SG.

[0033] The automatic transmission has a power-splitting planetary gear mechanism UG in the form of a planetary gear mechanism, a variator incorporating both electric machines EMA and EMB, and a first shift element K1 provided for engaging a first fixed transmission ratio (constant transmission ratio) G1 (hereinafter also referred to as fixed transmission ratio G1) and a second shift element B2 provided for engaging a second fixed transmission ratio G2.

[0034] The number of two gear ratios is mentioned here only for the sake of clarity, and in practice a greater number of gear ratios may be used.

[0035] Furthermore, the automatic transmission has two transmission shafts: an input shaft as a drive shaft used to connect the automatic transmission to the internal combustion engine VM in a torque-transmitting manner, and an output shaft as a driven shaft used to connect the automatic transmission to the wheels R of the vehicle in a torque-transmitting manner.

[0036] An automatic transmission may have more than two fixed gear ratios, in which case there will be a correspondingly greater number of shifting elements provided for engaging the additional gear ratios, either individual shifting elements for multiple gear ratios or combinations of shifting elements for a single gear ratio.

[0037] The planetary gear mechanism UG includes a carrier 1, an internal gear 2, and a sun gear 3. The planetary gear mechanism UG is coupled to transmit torque to both an input shaft and an output shaft. The planetary gear mechanism UG further includes a shaft by which the planetary gear mechanism can be coupled to transmit torque to the input shaft via a first switching element K1, which here forms a clutch, and to a second switching element B2, which here forms a brake. This shaft here has the effect of adjusting the rotational speed of the internal combustion engine VM. In other embodiments, the switching elements K1 and B2 may be provided for any torque transmission function.

[0038] The switching elements K1, B2 are each configured as pawl clutches, i.e., they are positively engaging (meshing) switching elements that require little pressure to stay in the engaged position. In other embodiments, the switching elements K1, B2 may also be any other suitable switching elements, such as frictionally engaging switching elements.

[0039] The variator function for changing the transmission ratio is provided by the first electric machine EMA operating as a generator and the second electric machine EMB operating as an electric motor, which allows kinetic energy to be converted into electrical energy and vice versa, thereby decoupling the rotational speeds of the electric machines EMA and EMB from each other.

[0040] The automatic transmission shifts (gear shifts) from the first fixed gear ratio G1 to the second fixed gear ratio G2 in accordance with the shifting flow described with reference to Figures 3, 5, 7, 9, 11 and 13.

[0041] 1 and 2, a first fixed transmission ratio G1 is engaged, i.e., the first shift element K1 is engaged and the second shift element B2 is disengaged. Furthermore, the variator is disengaged, i.e., the electric machine is not coupled to transmit torque to either the input or output shaft. All rotational speeds nG1 are the same. The first electric machine EMA can be operated as a generator to charge the high-voltage battery HVS.

[0042] To change over to the second fixed transmission ratio G2, the shifting element K1 of the current (old) fixed transmission ratio G1 is now unloaded according to FIG.

[0043] As can be seen in Figure 4, the variator is torque-coupled to the output shaft and via a shaft to the planetary gear set UG. In other words, the second electric machine EMB operates as an electric motor together with the driven parts, or together with the internal gear 2, or together with the wheels R, and is powered by the high-voltage battery HVS. The internal combustion engine VM is at a standstill or can be stopped.

[0044] The variator in turn disengages the first shift element K1 via the output shaft by means of a torque superposition (K1 is shown in dashed lines).

[0045] The essential part of the present invention is used at this timing, which will be explained again with reference to FIGS.

[0046] As shown in bold in FIG. 5, state 3, the switching element K1 is disengaged, as shown in FIG. 6 with K1 disconnected.

[0047] Next, according to FIG. 7, state 4 is reached, i.e., a preferably electrically infinitely variable gear ratio change in a power-split transmission (E-CVT). This is represented in FIG. 8 by a speed shift at sun gear 3. After the first shift element K1 is decoupled, the second gear ratio (fixed gear ratio) G2 is thus set via the infinitely variable gear ratio change of the variator or electric machine EMA. Brake B2 is still decoupled at this time.

[0048] This means that the three-axis operation eliminates the rotational speed difference in the second switching element B2.

[0049] FIG. 9 shows state 5 with the switching element B2 for the new fixed transmission ratio G2 engaged.

[0050] As can be seen in Figure 10, the second switching element B2 is now connected as soon as the rotational speed difference has reduced to zero or below a predefined limit value. This allows the second switching element B2 to take over the load of the variator, which can then be disengaged (see the electric machine EMB in Figure 10, dashed line). The brake B2 is not yet loaded (B2 dashed line).

[0051] In Figure 11, state 6 is reached, followed directly by state 7 or state 1 again, in which a new shift element B2 can be loaded (fully closed B2 in Figure 12). The gear change flow ends in Figure 12.

[0052] FIG. 13 shows an intermediate state according to the invention between states 5 and 6, which is achieved by a functional module ZVV (tooth stress protection) in the control unit SG or by a method implemented by the control unit SG, the effect of which on the torque curve M at the switching element SE (here B2) is shown in FIG. 14 for time t.

[0053] The following is an example in which the torque transition M is obtained as shown in FIG.

[0054] A form-locking switching element SE (e.g. B2) with an effective radius of e.g. 100 mm in a tooth-on-tooth position is subjected to an actuation force of e.g. 200 N. The assumed coefficient of friction is e.g. 0.15. This results in an estimated friction torque M1 of 3 Nm to be overcome. Based on the effective mass moment of inertia (J), the ratio of the rotational speed difference gradient to the effective torque (M-M1) is obtained, which is here 10 rad / Nms 2 The switching element SE must rotate torsionally through a worst case of 28° to allow engagement, but must not engage with a rotational speed difference of more than 10 rad / s.

[0055] From this, the period T2-T1 (t=2×Δφ / Δω) of 0.1 s (standby time) in Figure 14 and the angular acceleration of 100 rad / s 2Based on the ratio of the rotational speed difference gradient to the effective torque (M-M1), the maximum permissible additional torque dM is 10 Nm. Therefore, the switching element SE must not exceed 3 Nm + 10 Nm = 13 Nm (M1 + dM = M2). Thus, over the waiting time T2-T1 (here, 0.1 s), the reduced torque plateau M2 (M1 + dM) is set to 13 Nm. Before and after the waiting time T2-T1, the torque gradient dM / dt initially required for the switching element SE, i.e., the set torque gradient dM / dt, is implemented from T0 to T1 and from T2 to T3. T0 here is the point in time at which it can be assumed that the actuator of the switching element SE has since moved the switching element SE at least to a tooth-on-tooth position (which, in the ideal case, would of course be in the engaged region). To avoid damage or discomfort, it is only after T0 that the torque M is allowed to be applied to the new engaging positively-locking shift element SE (here B2) according to the proposed functional flow. A torque gradient dM / dt is set from T2 to T3 until the torque M3 at the fully loaded fixed ratio, here G2, is achieved.

[0056] If the torque is to be increased slightly rather than kept constant in the time range from T1 to T2, it still must not exceed 13 Nm, but the period for positive engagement will be longer since the required torsional rotation angle must still be achieved (see dashed line in Figure 14).

[0057] Thus, FIG. 14 shows an example of an engagement process of the switching element SE in conjunction with control of the internal combustion engine VM and / or motor-generator EMA in a DHT to ensure engagement of the switching element SE, including from all possible tooth-on-tooth positions.

[0058] Summary of the overall switching flow with intermediate states according to the invention starting from a current fixed transmission ratio: - Release of the old switching element K1 from the load by the electric machine (state 2). - Activation of the function module DZA for rotational speed adaptation (which causes a load change at the switching element K1 to be switched off and simultaneously controls the actuator for decoupling the switching element K1). - Decouple the old switching element K1 (state 3) (Switches to E-CVT mode). -E-CVT mode adapts the rotational speed to change the gear ratio in the transmission (nG1⇒nG2) (state 4). - Engagement of a new switching element (B2) (state 5). - activation of the function module ZVV according to the invention in the control unit SG for carrying out the method for secure engagement of the positively locking switching element SE (here B2), - Loading of the new switching element (B2) (state 6) and -"Down" the electric machines EMA and EMB (state 7 = state 1) ⇒ new fixed gear ratio G2.

[0059] Summary of the method implemented using the functional module ZVV according to the invention: - Applying a torque (M) to the engaging shifting element (SE; B2) with a set torque gradient (dM / dt) starts at a time (T0) when it can be considered to be at least in a tooth-on-tooth position (the gear may also happen to be already engaged); - the friction torque (M1) to be overcome is estimated, in particular depending on the effective radius, the assumed friction coefficient and the available actuation force of the actuator of the switching element (SE); The waiting time (T2-T1) is determined depending on the effective mass moment of inertia, the maximum torsional rotation angle, and the maximum rotational speed difference gradient that is set; - during the waiting time (T2-T1), the maximum allowable torque (M1) is set, which is determined from the estimated friction torque (M1) to be overcome and the additional torque (dM); The additional torque (dM) is determined in particular from the ratio of the present rotational speed difference gradient to the effective torque (M-M1) or based on the effective mass moment of inertia (J) relative to the engaging switching element. After the waiting time (T2-T1) has elapsed (or when the transmission ratio is already engaged without a tooth-on-tooth position), the set torque gradient (dM / dt) is again set for torque control until the fully loaded torque (M2) is achieved (at time T3) at the new fixed transmission ratio (here G2).

Claims

1. A motor vehicle having at least two drive motors (12, EMA, EMB), at least one of which is an electric machine (EMA), a high-voltage battery (HVS), an automatic transmission having at least one fixed transmission ratio (G1, G2) and at least one power-split transmission (E-CVT) and / or at least one series transmission for changing the transmission ratio to the at least one fixed transmission ratio (G1; G2), and an electronic control unit (SG) for controlling the internal combustion engine (VM) and the electric machine (EMA) during the period from engagement of a shift element (SE; B2) to loading of the shift element (SE; B2) as part of the transmission ratio change. the engaging switching element (SE; B2) is a positively locking switching element configured as a pawl clutch and is loaded with a set torque gradient (dM / dt) at a first time point (T0), which can be considered to be at least in a tooth-on-tooth position, up to a second time point (T1); - during a set waiting time, the set torque (M) is limited to the maximum allowed torque (M2) from the second time point (T1) to the third time point (T2); After the waiting time has elapsed or when the engaged state is recognized, the engaging switching element (SE; B2) is further loaded with a preset torque gradient (dM / dt). A motor vehicle equipped with a functional module (ZVV) capable of setting the torque transition in such a manner.

2. 2. The vehicle according to claim 1, wherein the torque (M) is controlled in a pulsed manner during a set waiting time.

3. 3. A vehicle according to claim 1 or 2, characterized in that the maximum permissible torque (M2) is determined from the estimated friction torque (M1) to be overcome and the additional torque (dM).

4. 4. A vehicle according to claim 1, wherein the friction torque (M1) to be overcome is estimated as a function of the effective radius, the assumed coefficient of friction and the available actuation force of the actuator of the switching element.

5. 5. A motor vehicle according to claim 1, wherein the additional torque (dM) is determined depending on the set maximum permissible rotational speed difference of the switching element and the effective mass moment of inertia (J).

6. 6. The vehicle according to claim 1, wherein the set waiting time is determined according to the effective mass moment of inertia (J), the maximum torsional rotation angle, and the set maximum rotational speed difference gradient.

7. 7. An automatic transmission for a motor vehicle according to claim 1, comprising a planetary gear mechanism (UG), at least one shifting element (K1 and / or B2), at least one electric machine (EMA) as a drive motor which is part of a variator, and an actuator controllable by an electronic control unit (SG) via a functional module (ZVV).

8. An electronic control unit (SG) for a motor vehicle according to any one of claims 1 to 6 or for an automatic transmission according to claim 7, comprising a functional module (ZVV).

9. 7. A method for shifting an automatic transmission in a motor vehicle according to any one of claims 1 to 6, comprising using an electronic control unit (SG) to control the internal combustion engine (VM) and the electric machine (EMA) during the period from engagement of the switching element (SE; B2) to loading of the switching element (SE; B2) as part of a gear ratio change, the method comprising: - at a first time point (T0), which can be considered as at least a tooth-on-tooth position, the engaging switching element (SE; B2) is loaded with a set torque gradient (dM / dt) up to a second time point (T1), - during a set waiting time, the set torque (M) is limited to the maximum allowed torque (M2) from the second time point (T1) to the third time point (T2); After the waiting time has elapsed or when the engaged state is recognized, the engaging switching element (SE; B2) is further loaded with a preset torque gradient (dM / dt). How to set the torque transition.

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