Method for gearshift control in a transmission

Abstract

Method for gearshift control in a transmission (100, 200, 300, 400, 500), wherein the transmission has a plurality of friction shift elements (138, 142, 144, 146, 148, 150) and a positive-locking shift element (140), wherein the plurality of friction shift elements and the positive-locking shift element (138, 142, 144, 146, 148, 150, 140) can be engaged in combinations of three to obtain a plurality of gear stages, characterized by the steps: - Shifting (S1) of the transmission into one (R1, R2) of the plurality of gear stages by positioning two (146, 148; 146, 150) of the plurality of friction shift elements and the positive-locking shift element (140) in an engaged state; and - Positioning (S2) another friction switching element (138) of the plurality of friction switching elements in an engaged state to reduce the chatter of the positive locking switching element (140) in gear stage (R1, R2).

Description

TECHNICAL AREA

[0001] The present invention relates to a method for controlling the gearshift in a transmission. The invention also relates to a transmission, a control unit for the gearshift, and a vehicle having such a transmission. The invention is applicable to vehicles, in particular construction machinery such as wheel loaders, semi-trailer loaders, dump trucks, etc. Although the invention is mainly described with regard to a semi-trailer loader, it may also be applicable to other types of vehicles, such as trucks. BACKGROUND

[0002] Heavy machinery is often used in connection with transporting heavy loads on construction sites or similar locations. These machines can be used for transport related to road or tunnel construction, sand pits, mines, forestry, and similar environments. Therefore, heavy machinery is frequently used with large and heavy loads on difficult terrain and slippery ground where there are no regular roads.

[0003] To meet the desired requirements in the areas where the machine is frequently used, a high-quality vehicle transmission is essential. The transmission is designed to adjust the vehicle's speed and tractive force depending on the specific driving situation. The transmission comprises a gear arrangement, which, depending on the specific transmission type, may include, for example, conventional gear sets with cylindrical gears meshing together, planetary gear sets, each comprising a sun gear, a ring gear, and a planet carrier, or a gear arrangement with a combination of conventional gear sets and one or more planetary gear sets.

[0004] US Patent 9,182,013 B2 describes a power-shift transmission comprising an input shaft and an output shaft. A plurality of planetary gear sets and a plurality of shifting elements are arranged between the input and output shafts to provide the desired gear ratios. Furthermore, at least one of the shifting elements is a positive-locking shifting element, in this case, a dog clutch. One objective of US Patent 9,182,013 B2 is to enable shifting into a gear while the dog clutch is engaged. This objective is achieved by using a support wheel that is engaged while the dog clutch is being synchronized. This allows the dog clutch to engage after synchronization, thereby performing the gear shift.

[0005] Although the transmission in US 9 182 013 B2 provides for the use of a jaw coupling, there is still a need for further improvements regarding the control of the transmission arrangement when such a jaw coupling is used.

[0006] Furthermore, DE 10 2013 205 610 A1 discloses a method for shifting a transmission, in particular a planetary automatic transmission, of a vehicle while driving. The transmission has at least one load-operated positive-lock switching device and at least one further switching element. During downshifting, the transmission shifts from an instantaneous gear to a lower target gear by closing the at least one load-operated positive-lock switching device and opening a further switching element. SUMMARY

[0007] An objective of the present invention is to provide a method for gearshift control in a transmission that improves the performance of the transmission when using a positive-locking shift element compared to the prior art. This objective is achieved at least partially by a method according to claim 1.

[0008] According to a first aspect of the present invention, a method for gearshift control in a transmission is provided, wherein the transmission has a plurality of friction shift elements and a positive-locking shift element, wherein the plurality of friction shift elements and the positive-locking shift element can be engaged in combinations of three to obtain a plurality of gear stages, wherein the method comprises the steps of shifting the transmission into one of a plurality of gear stages by positioning two of the plurality of friction shift elements and the positive-locking shift element in an engaged state; and positioning another friction shift element of the plurality of friction shift elements in an engaged state to reduce the chatter of the positive-locking shift element in the gear stage.

[0009] The term "positive locking switching element" shall be interpreted in the following and throughout this description as a switching element that cannot be positioned in a slip state. Therefore, the positive locking switching element is positioned either in an engaged state or in a disengaged state, where the engaged state means that the same rotational speed is provided to transmission components on each side of the positive locking switching element. A friction switching element, on the other hand, can be positioned in at least a partial engaged state, i.e., a slip state. Positive locking switching elements and friction switching elements can also be described as locking and connecting mechanisms, respectively, designed for the selective connection of transmission components. The transmission components can be, for example, a transmission housing and / or rotating components of the transmission.

[0010] Furthermore, the step of positioning the additional friction switching element in the engaged state must not occur after the step of shifting the transmission into one of the plurality of gear stages. How and when the additional friction switching element is brought into engagement is described in detail below. Consequently, the invention is not limited to the steps being performed in a specific sequential order. Likewise, the step of positioning two of the plurality of friction switching elements in the engaged state should not be designed such that the two friction switching elements must be positioned in a disengaged state in a previous gear stage before the shifting step is performed. Therefore, one or both of the two friction switching elements can be held in engagement when the transmission is shifted into the gear stage.Consequently, when the transmission is shifted into gear, one or both of the multitude of friction shift elements may already be in the engaged state, i.e., one or both of the friction shift elements may have been in the engaged state in the previous gear.

[0011] A positive-locking switching element can advantageously have circumferential clearance between, for example, teeth on the respective positive-locking switching element parts, wherein the circumferential clearance is advantageous when the positive-locking switching element is positioned in the engaged state. However, in situations where an alternating torque is applied to the positive-locking switching element, the circumferential clearance can cause chatter in the positive-locking switching element. The alternating torque can occur, for example, during the idling of a drive motor connected to the transmission. An advantage of the present invention is therefore that the chatter in the positive-locking switching element is reduced. The gear stage can be obtained by positioning two friction switching elements and the positive-locking switching element in the engaged state.However, the inventors unexpectedly discovered that another friction switching element can also be positioned in the engaged state, which reduces the chatter in the positive-locking switching element, while not affecting the transmission ratio of the specific gear stage.

[0012] According to an exemplary embodiment, a first part of the positive-locking switching element can be connected to a gearbox housing, and a second part of the positive-locking switching element can be connected to the gearbox housing via the further friction switching element.

[0013] This mechanically connects the second part of the positive-locking switching element to the gearbox housing, holding it sufficiently in position to reduce chatter in the positive-locking switching element.

[0014] According to an exemplary embodiment, a first rotating element of the transmission can be connected to the transmission housing by means of the positive-locking switching element, and a second rotating element of the transmission can be connected to the transmission housing by means of the further friction switching element, and the first rotating element and the second rotating element can be connected to each other by means of one of the two of the plurality of friction switching elements.

[0015] This keeps the first rotating element stationary, which reduces the rattling in the positive-locking switching element. Consequently, the rattling in the positive-locking switching element is reduced by connecting the first and second rotating elements to each other by means of one or two of the multiple friction switching elements, and also by connecting the second rotating element to the gearbox housing by means of another friction switching element, in order to keep both the first and second rotating elements stationary.

[0016] According to an exemplary embodiment, the method can include the step of synchronizing the positive-locking switching element by means of the further friction switching element, wherein the further friction switching element is held in the engaged state after synchronization.

[0017] The term "synchronize" should be understood to mean that the relative rotational speed of the transmission components connected to the positive-locking switching element is reduced. The positive-locking switching element can thus be positioned in the engaged state when the relative rotational speed of the transmission components connected to the respective parts of the positive-locking switching element is below a predetermined threshold. This predetermined threshold is understood as the rotational speed below which it is expedient / desirable to engage the positive-locking switching element.

[0018] One advantage is that the positive-locking switching element can be efficiently positioned in the engaged state. This allows the positive-locking switching element to be designed as a so-called jaw coupling. Thus, according to an exemplary embodiment, the positive-locking switching element can be a jaw coupling. The use of a jaw coupling is advantageous because the torque is primarily transmitted by normal forces between the halves of the jaw coupling. This makes the positive-locking switching element more durable compared to, for example, a friction switching element. Furthermore, lower tensile losses occur when the positive-locking switching element is disengaged.

[0019] According to an exemplary embodiment, the method can include the step of synchronizing the positive-locking switching element by means of one of the two of the plurality of friction switching elements.

[0020] It should be easy to understand that when the positive-locking switching element is synchronized by means of either the other friction switching element or one of the two friction switching elements of the plurality, the other is held in an engaged state. It should therefore be easy to understand that the other friction switching element is held in engagement and contributes passively to the synchronization. Consequently, the synchronization of the positive-locking switching element is achieved by connecting the first and second rotating elements to each other by means of one of the two friction switching elements of the plurality, and also by connecting the second rotating element to the gearbox housing by means of the other friction switching element.

[0021] According to an exemplary embodiment, the method can include the step of synchronizing the positive-locking switching element by means of one of the two of the plurality of friction switching elements, wherein one of the two of the plurality of friction switching elements is held in the engaged state after synchronization.

[0022] Another advantage is that the friction shift elements used for synchronization can be kept engaged, which reduces chatter in the positive-locking shift element. Keeping the friction shift elements engaged even after the positive-locking shift element has been synchronized does not affect the gear ratio between an input shaft and an output shaft of the transmission. A further advantage is that the same friction shift elements can be used for both synchronization and chatter reduction. Consequently, it is not necessary to position a decoupled friction shift element in the engaged state after the positive-locking shift element has been synchronized.

[0023] According to an exemplary embodiment, the method can include the step of increasing a contact pressure between a pair of friction elements of the friction switching element used for synchronizing the positive locking switching element after initiating the engagement of the positive locking switching element.

[0024] This ensures that sufficient contact pressure of the friction switching element is maintained after the engagement of the positive-locking switching element has been initiated.

[0025] According to an exemplary embodiment, at least one of the plurality of friction switching elements can be designed to connect the transmission to a drive machine, wherein the method can include the step of decoupling the drive machine from the transmission by positioning the at least one of the plurality of friction switching elements in a disengaged state before shifting the transmission into one of the plurality of gear stages.

[0026] One advantage is that no torque is provided by the drive motor during gear shifting into one of the many gear positions.

[0027] According to an exemplary embodiment, the method can include the step of decoupling the drive motor from the gearbox before synchronizing the positive-locking switching element.

[0028] One advantage is that the synchronization of the positive-locking switching element can be carried out more quickly.

[0029] According to an exemplary embodiment, one of the multiple gear stages can be a reverse gear stage.

[0030] According to an exemplary embodiment, the transmission can be shifted into one of the multiple gear stages from a forward gear stage.

[0031] According to an exemplary embodiment, the transmission can have a first, a second, a third and a fourth planetary gear set, each comprising a sun gear, a planet carrier and a ring gear.

[0032] Planetary gear sets are advantageous because their combination allows for a large number of gears with different ratios. Furthermore, planetary gear sets, in combination with the numerous friction shift elements, can perform relatively smooth gear changes.

[0033] According to an exemplary embodiment, the first rotating element can be functionally connected to the planet carrier of the second planetary gear set, wherein the planet carrier of the second planetary gear set can further be functionally connected to the ring gear of the first planetary gear set, and wherein the planet carrier of the first planetary gear set can be functionally connected to an output shaft of the transmission.

[0034] Therefore, during synchronization, the rotational speed of the planet carrier of the second planetary gear set is reduced to approximately zero, and, as the chatter in the positive-locking shift element is reduced, the planet carrier of the second planetary gear set is essentially held stationary. A gear stage can also be achieved with respect to the output shaft of the transmission.

[0035] According to an exemplary embodiment, the second rotating element can be functionally connected to the ring gear of the third planetary gear set.

[0036] According to an exemplary embodiment, the sun gear of the second planetary gear set can be functionally connected to the sun gear of the first planetary gear set.

[0037] According to an exemplary embodiment, the planet carrier of the third planetary gear set can be functionally connected to the ring gear of the second planetary gear set.

[0038] According to an exemplary embodiment, seven switching elements can be engaged in combinations of three to obtain nine forward gears and three reverse gears.

[0039] According to a second aspect of the present invention, a control unit is provided for controlling the gear shifting in a transmission, wherein the transmission has a plurality of friction shift elements and a positive-locking shift element, wherein the plurality of friction shift elements and the positive-locking shift element can be engaged in combinations of three to obtain a plurality of gear stages, wherein the control unit is configured to control the shifting of the transmission into one of the plurality of gear stages by positioning two of the plurality of friction shift elements and the positive-locking shift element in an engaged state; and positioning a further friction shift element of the plurality of friction shift elements in an engaged state to reduce the chatter of the positive-locking shift element in the gear stage.

[0040] The effects and features of the second aspect are largely analogous to those described above with reference to the first aspect of the present invention.

[0041] According to a third aspect of the present invention, a vehicle is provided comprising a drive motor, a transmission and a control unit, as described above in relation to the second aspect of the present invention.

[0042] According to a fourth aspect of the present invention, a computer program is provided which includes program code facilities for performing the steps described above in relation to the first aspect of the present invention when the program is running on a computer.

[0043] According to a fifth aspect of the present invention, a computer-readable medium is provided on which a computer program is stored, comprising program facilities for performing the steps described above in relation to the first aspect of the present invention when the program facility is running on a computer.

[0044] The effects and features of the third, fourth and fifth aspects are largely analogous to those described above with reference to the first aspect of the present invention.

[0045] According to a sixth aspect of the present invention, a transmission is provided which has a plurality of friction switching elements and a positive-locking switching element, wherein the plurality of friction switching elements and the positive-locking switching element can be engaged in combinations of three to obtain a plurality of gear stages, wherein at least one of the plurality of gear stages of the transmission is obtained by positioning two of the plurality of friction switching elements and the positive-locking switching element in an engaged state, and by positioning a further friction switching element of the plurality of friction switching elements in the engaged state for the at least one gear stage in order to reduce the chatter of the positive-locking switching element in the gear stage.

[0046] This provides a transmission that is able to use a positive-locking shift element with reduced chatter when it is positioned in the engaged state for at least one gear stage.

[0047] Further effects and features of the sixth aspect of the present invention are largely analogous to those described above with reference to the first aspect.

[0048] Further features and advantages of the present invention will become apparent from studying the appended claims and the following description. The person skilled in the art will recognize that various features of the present invention can be combined to create embodiments other than those described below, without departing from the scope of the present invention. DEFINITIONS

[0049] The relationship between the rotational speeds of the different elements in a planetary gear set is defined as follows: ωS−ωPωR−ωP=R where ω S the rotational speed of the sun gear; ω P the rotational speed of the planet carrier; ω R the rotational speed of the ring gear; and R is the stationary transmission ratio of the planetary gear set.

[0050] The term “stationary gear ratio” R used here for a planetary gear set is defined as the ratio of the rotational speed of the sun gear to the rotational speed of the ring gear in a situation where the planet carrier is stationary, i.e.: R=−zRzS for single planetary gear wheels (Eq. 2) and R=+zRzS for double planetary gear wheels (Eq. 3) wherein Z R the number of teeth of the ring gear; and Z S The number of teeth on the sun gear.

[0051] Similarly, the term "ratio" in relation to a gearbox should be understood as referring to the number of revolutions of the gearbox's input shaft divided by the number of revolutions of the gearbox's output shaft. Furthermore, the term "stage" should be understood as the quotient obtained by dividing the ratio of one gear by the ratio of an adjacent gear in the gearbox. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The above-mentioned as well as additional aims, features and advantages of the present invention are better understood by the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein Fig. 1 is a side view showing a work machine in the form of a semi-trailer loader; Fig.Figures 2-6 schematically show gearboxes according to exemplary embodiments of the present invention; Fig. Figures 7-9 schematically show gear shift diagrams for three different gear shifts according to exemplary embodiments of the present invention; and Fig. 10. A flowchart of a procedure for controlling the gearshift in the Fig. Figures 2-6 show gear units according to an exemplary embodiment. DETAILED DESCRIPTION OF EXAMPLE EXECUTIONS OF THE INVENTION

[0053] The present invention is now described in more detail below with reference to the accompanying drawings, which show exemplary embodiments of the invention. However, the invention can be implemented in many different forms and should not be interpreted as limited to the embodiments presented here; rather, these embodiments are provided for the sake of thoroughness and completeness. Throughout this description, the same reference numerals refer to the same elements.

[0054] Fig.Figure 1 is a side view of a work machine 201 in the form of a semi-trailer loader, comprising a tractor unit 202 with a cab 203 for a driver and a trailer unit 204 with a platform on which a loading body 205, here in the form of a container, is arranged for receiving a load. The loading body 205 is preferably pivotally connected to the rear section and can be tilted by a pair of tilting cylinders 206, for example, hydraulic cylinders. The tractor unit 202 has a frame 207 and a pair of wheels 208 suspended from the frame 207. The trailer unit 204 has a frame 209 and two pairs of wheels 210, 211 suspended from the frame 209.

[0055] The working machine is frame-steered, i.e., there is an articulation 212 that connects the tractor unit 202 and the trailer unit 204 of the working machine 201. The tractor unit 202 and the trailer unit 204 are pivotally connected to each other for pivoting about a substantially vertical pivot axis 213.

[0056] The working machine preferably comprises a hydraulic system having two hydraulic cylinders 214 and steering cylinders arranged on opposite sides of the working machine for rotating the working machine by means of relative movement of the traction unit 202 and the trailer unit 204. However, the hydraulic cylinders can be replaced by any other linear actuator for steering the machine, such as an electromechanical linear actuator.

[0057] Furthermore, the semi-trailer loader comprises a drive unit 216, shown here as an internal combustion engine, and a transmission 218 with a transmission arrangement according to one of the below in relation to Fig. 2-6 described embodiments. Furthermore, the semi-trailer loader also has a control unit 600 for controlling the transmissions described below. The control unit 600 can be an existing control unit for controlling a transmission or a part thereof.

[0058] In the following description, the multitude of friction switching elements and the positive-locking switching element are also described as connection mechanisms and locking mechanisms, wherein a connection mechanism is designed to connect at least two rotating planetary elements to each other or at least one rotating planetary element to an input shaft or an output shaft, and a locking mechanism is designed to lock at least one rotating planetary element to a gearbox housing.

[0059] Now, with reference to Fig.Figure 2 illustrates an exemplary embodiment of a transmission 100 according to the present invention. The transmission 100 comprises a first planetary gear set 102, comprising a sun gear 102S, a planet carrier 102P and a ring gear 102R, a second planetary gear set 104, comprising a sun gear 104S, a planet carrier 104P and a ring gear 104R, a third planetary gear set 106, comprising a sun gear 106S, a planet carrier 106P and a ring gear 106R, and a fourth planetary gear set 108, comprising a sun gear 108S, a planet carrier 108P and a ring gear 108R. The gearbox 100 further comprises an input shaft 136 for receiving rotary motion / torque from the drive motor 216 of the vehicle 201 and an output shaft 112 for providing rotary motion / torque to the drive wheels of the vehicle 201.

[0060] The various elements of the planetary gear sets 102, 104, 106, 108 of the gearbox 100, i.e. the sun gear, the planet carrier and the ring gear, are in the Fig. The exemplary embodiment shown in Figure 2 is configured according to the following description. It should be readily apparent that the various elements described below are connected to one another either directly, i.e., functionally, or via a switching element, i.e., selectively. The elements can be functionally connected to one another by means of, for example, a connecting element. Such a connecting element can be, for example, a solid shaft, a hollow shaft, a drum, or any other suitable element for connecting two elements together, the elements being known to those skilled in the art. Therefore, no explicit explanation is given below regarding the device by which the elements are connected to one another.

[0061] The planet carrier 102P of the first planetary gear set 102 is functionally connected to the output shaft 112 of the gearbox 100; that is, the planet carrier 102P is directly connected to the output shaft 112 of the gearbox 100 at all times. Furthermore, the ring gear 102R of the first planetary gear set 102 is functionally connected to the planet carrier 104P of the second planetary gear set 104. The sun gear 102S of the first planetary gear set 102 is functionally connected to the sun gear 104S of the second planetary gear set 104. Furthermore, the sun gear 102S of the first planetary gear set 102 and the sun gear 104S of the second planetary gear set 104 can be selectively connected to a gearbox housing 160 of the gearbox 100 by means of a friction switching element in the form of a third locking mechanism 142.Therefore, when engaged, the third locking mechanism 142 initially reduces the rotational speed of the respective sun gears 102S, 104S and then locks the respective sun gears 102S, 104S to the gearbox housing 160.

[0062] The ring gear 104R of the second planetary gear set 104 is functionally connected to the planet carrier 106P of the third planetary gear set 106. Furthermore, the planet carrier 104P of the second planetary gear set 104 can be selectively connected to the sun gear 106S of the third planetary gear set 106 by means of a friction switching element in the form of a second connecting mechanism 144. The planet carrier 104P of the second planetary gear set 104 can also be selectively connected to the ring gear 106R of the third planetary gear set 106 by means of a friction switching element in the form of a first connecting mechanism 146. In addition, the planet carrier 104P of the second planetary gear set 104 can be selectively connected to the gear housing 160 by means of a positive-locking switching element in the form of a second locking mechanism 140.Therefore, when engaged, the second locking mechanism 140 locks the planet carrier 104P to the gearbox housing 160. The second locking mechanism 140 can, for example, be designed as a jaw coupling. As further described in... Fig. As shown in Figure 2, the second locking mechanism 140 has a first part 140a which is connected to the gear housing 160 and a second part 140b which is connected to the planet carrier 104P of the second planetary gear set 104 and to the first connecting mechanism 146.

[0063] The sun gear 106S of the third planetary gear set 106 is functionally connected to the ring gear 108R of the fourth planetary gear set 108. The ring gear 106R of the third planetary gear set 106 is functionally connected to the sun gear 108S of the fourth planetary gear set 108. The ring gear 106R of the third planetary gear set 106 and the sun gear 108S of the fourth planetary gear set 108 can be selectively connected to the gearbox housing 160 by means of a friction switching element in the form of a first locking mechanism 138. Therefore, when engaged, the first locking mechanism 138 initially reduces the rotational speed of the ring gear 106R and the sun gear 108S and then locks the ring gear 106R and the sun gear 108S to the gearbox housing 160.

[0064] Furthermore, and as in Fig.As shown in Figure 2, the transmission has a first rotating element 101. The first rotating element 101 is functionally connected to the second part 140b of the positive-locking switching element 140, the planet carrier 104P of the second planetary gear set 104, and a first section of the first connecting mechanism 146. Therefore, the first rotating element 101 rotates at the same speed as each of these components. Furthermore, the transmission also has a second rotating element 103. The second rotating element 103 is functionally connected to the first locking mechanism 138, the ring gear 106R of the third planetary gear set 106, and a second section of the first connecting mechanism 146. Therefore, the second rotating element 103 rotates at the same speed as each of these components.This allows the first 101 and the second 103 rotating elements to be connected by positioning the first connecting mechanism 146 in the engaged state, i.e., connecting the first and second sections of the first connecting mechanism 146. Furthermore, by locking the first locking mechanism 138 to the gear housing 160, the first 101 and second 103 rotating elements are held stationary.

[0065] Finally, the input shaft 136 can be selectively connected to the ring gear 108R of the fourth planetary gear set 108 and the sun gear 106S of the third planetary gear set 106 by means of a friction switching element in the form of a third connecting mechanism 148, and can be selectively connected to the planet carrier 108P of the fourth planetary gear set 108 by means of a friction switching element in the form of a fourth connecting mechanism 150.

[0066] According to the in Fig.In the exemplary embodiment shown in 2, the steady-state transmission ratio of each of the first 102, second 104, third 106, and fourth 108 planetary gear sets is negative. According to a non-limiting example, the steady-state transmission ratio for each of the planetary gear sets can be as described below in Table 1. Table 1 - Exemplary stationary translation ratios for the embodiment shown in Fig. 2. First planetary gear set (102) Second planetary gear set (104) Third planetary gear set (106) Fourth planetary gear set (108) -2,825 -1,625 -1,700 -2,650

[0067] Referring to Fig. Figure 3 shows another exemplary embodiment of the gearbox 200. The gearbox 200 of the in Fig. The exemplary embodiment shown in 3 is in many respects similar to the one described in Fig. The gearbox 100 shown in section 2 is similar. Therefore, the following mainly describes the parts that are different from gearbox 100 in the diagram. Fig. They are two different things.

[0068] The planet carrier 108P of the fourth planetary gear set 108 is functionally connected to the input shaft 136 of the gearbox 200. Furthermore, the ring gear 106R of the third planetary gear set 106 is functionally connected to the sun gear 108S of the fourth planetary gear set 108. Additionally, the sun gear 106S of the third planetary gear set 106 is selectively connected to the input shaft 136 by means of a friction switching element in the form of a third connection mechanism 148, and can be selectively connected to the ring gear 108R of the fourth planetary gear set 108 by means of a friction switching element in the form of a fourth connection mechanism 150.

[0069] According to the in Fig.In the exemplary embodiment shown in Figure 3, the steady-state transmission ratio of each of the first 102, second 104, third 106, and fourth 108 planetary gear sets is negative. According to a non-limiting example, the steady-state transmission ratio for each of the planetary gear sets can be as described below in Table 2. Table 2 - Exemplary stationary translation ratios for the embodiment shown in Fig. 3. First planetary gear set (102) Second planetary gear set (104) Third planetary gear set (106) Fourth planetary gear set (108) -2,825 -1,625 -1,700 -2,650

[0070] Referring to Fig. Figure 4 shows another exemplary embodiment of the gearbox 300. The gearbox 300 of the in Fig. The exemplary embodiment shown in section 4 is in many respects similar to the one described in section 4. Fig. 2 and Fig. The three gearboxes shown are similar. Therefore, the following mainly describes the differences in comparison to these gearboxes.

[0071] The sun gear 106S of the third planetary gear set 106 is functionally connected to the ring gear 108R of the fourth planetary gear set 108. The planet carrier 108P of the fourth planetary gear set 108 is also functionally connected to the input shaft 136 of the gearbox 300. Furthermore, the sun gear 108S of the fourth planetary gear set 108 can be selectively connected to the input shaft 136 and the planet carrier 108P of the fourth planetary gear set 108 by means of a friction switching element in the form of a third connection mechanism 148. Finally, the ring gear 106R of the third planetary gear set 106 can be selectively connected to the sun gear 108S of the fourth planetary gear set 108 by means of a friction switching element in the form of a fourth connection mechanism 150.

[0072] According to the in Fig.In the exemplary embodiment shown in Figure 4, the steady-state transmission ratio of each of the first 102, second 104, third 106, and fourth 108 planetary gear sets is negative. According to a non-limiting example, the steady-state transmission ratio for each of the planetary gear sets can be as described below in Table 3. Table 3 - Exemplary stationary translation ratios for the embodiment shown in Fig. 4. First planetary gear set (102) Second planetary gear set (104) Third planetary gear set (106) Fourth planetary gear set (108) -2,825 -1,625 -1,700 -2,650

[0073] Referring to Fig. Figure 5 shows another exemplary embodiment of the gearbox 400. The gearbox 400 of the in Fig. The exemplary embodiment shown in Figure 5 is similar in many respects to the gearboxes described above, and therefore the differences compared to these gearboxes will mainly be described below.

[0074] The sun gear 106S of the third planetary gear set 106 is functionally connected to the planet carrier 108P of the fourth planetary gear set 108. The planet carrier 106P of the third planetary gear set 106 is also functionally connected to the sun gear 108S of the fourth planetary gear set 108. Furthermore, the input shaft 136 can be selectively connected to the sun gear 106S of the third planetary gear set 106 and the planet carrier 108P of the fourth planetary gear set 108 by means of a friction switching element in the form of a third connection mechanism 148, and selectively connected to the ring gear 108R of the fourth planetary gear set 108 by means of a friction switching element in the form of a fourth connection mechanism 150.

[0075] According to the in Fig.In the exemplary embodiment shown in Figure 5, the steady-state transmission ratio of each of the first 102, second 104, and third 106 planetary gear sets is negative. However, the steady-state transmission ratio of the fourth planetary gear set 108 is positive. According to a non-limiting example, the steady-state transmission ratio for each of the planetary gear sets can be as described below in Table 4. Table 4 - Exemplary stationary translation ratios for the embodiment shown in Fig. 5. First planetary gear set (102) Second planetary gear set (104) Third planetary gear set (106) Fourth planetary gear set (108) -2,825 -1,625 -1,700 2,300

[0076] Finally, with reference to Fig. Figure 6 shows another exemplary embodiment of the gearbox 500. The gearbox 500 of the in Fig. The exemplary embodiment shown in 6 is similar in many respects to the gearboxes described above, and therefore the differences compared to these gearboxes will mainly be described below.

[0077] The sun gear 106S of the third planetary gear set 106 is functionally connected to the sun gear 108S of the fourth planetary gear set 108. The planet carrier 106P of the third planetary gear set 106 is also functionally connected to the planet carrier 108P of the fourth planetary gear set 108. Furthermore, the input shaft 136 is selectively connected to the sun gear 106S of the third planetary gear set 106 and the sun gear 108S of the fourth planetary gear set 108 by means of a friction switching element in the form of a third connection mechanism 148, and can be selectively connected to the ring gear 108R of the fourth planetary gear set 108 by means of a friction switching element in the form of a fourth connection mechanism 150.

[0078] According to the in Fig.In the exemplary embodiment shown in Figure 6, the steady-state transmission ratio of each of the first 102, second 104, and third 106 planetary gear sets is negative. However, the steady-state transmission ratio of the fourth planetary gear set 108 is positive. According to a non-limiting example, the steady-state transmission ratio for each of the planetary gear sets can be as described below in Table 5. Table 5 - Exemplary stationary translation ratios for the embodiment shown in Fig. 6. First planetary gear set (102) Second planetary gear set (104) Third planetary gear set (106) Fourth planetary gear set (108) -2,825 -1,625 -1,700 1,770

[0079] Since the fourth planetary gear set 108 has a positive stationary gear ratio and due to the fact that the planet carrier 108P of the fourth planetary gear set 108 is functionally connected to the planet carrier 106P of the third planetary gear set 106, and that the sun gear 108S of the fourth planetary gear set 108 is functionally connected to the sun gear 106S of the third planetary gear set 106, the third 106 and fourth 108 planetary gear sets can be designed as a Ravigneaux compound planetary gear set.

[0080] The in Fig. The exemplary embodiments shown in figures 2-6 and described above are designed to assume the gears shown in Table 6 below. Fig.The transmissions shown in Figures 2-6 have nine forward gears and three reverse gears. In Table 6 below, the locking mechanisms are simply referred to as "brakes," while the coupling mechanisms are simply referred to as "clutches." A cell marked with a dot indicates an engaged state, and an empty cell indicates a disengaged state. Table 6 also shows non-limiting examples of the gear ratios and stages achievable with the transmission for the various gears. The gear ratios and stages shown in Table 6 are derived from the exemplary steady-state gear ratios shown in Tables 1-5 above. Table 6 - Shift diagram, gear ratios and stages for the different gears. aisle brakes Clutches Relationship Level 138 140 142 148 150 144 146 1 ● ● ● 5,91 1,38 2 ● ● ● 4,29 3 ● ● ● 2,99 1,44 4 ● 2,19 1,37 5 ● ● ● 1,72 1,27 1,27 6 ● ● ● 1,35 1,35 7 ● ● ● 1,00 1,27 8 ● ● ● 0,79 1,38 9 ● ● ● 0,57 R1 ● ● ● ● -6,36 1,38 R2 ● ● ● ● -4,61 1,96 R3 ● ● ● -2,35

[0081] As shown in Table 6 above, the gearboxes in Fig.The transmission has nine forward gears and three reverse gears (designated with an R). Gear shifting can preferably be performed by single-stage or two-stage shifting. Single-stage shifting means shifting from one gear to the next, for example, shifting from first to second, second to third, third to second, etc. Two-stage shifting means shifting without the next, for example, shifting from first to third, second to fourth, third to first, etc.

[0082] As can be seen from Table 6, single-stage forward gear shifting involves only individual switching operations of the linkage mechanisms and the locking mechanisms; that is, when single-stage gear shifts are performed, only one of the linkage / locking mechanisms switches from an engaged state to a disengaged state, and only one of the linkage / locking mechanisms switches from a disengaged state to an engaged state. For example, when shifting from first gear to second gear, only the third linkage mechanism 148 switches from an engaged state to a disengaged state, and only the fourth linkage mechanism 150 switches from a disengaged state to an engaged state.

[0083] Furthermore, as shown in Table 6, there is only one occasion in two-stage gear shifting where double shifting occurs. Double shifting is understood to mean that two coupling / locking mechanisms change from an engaged state to a disengaged state, and two coupling / locking mechanisms change from a disengaged state to an engaged state. In two-stage gear shifting, this occurs when shifting from first to third gear or, conversely, from third to first gear. When shifting from first to third gear, the first locking mechanism 138 and the third coupling mechanism 148 change from an engaged state to a disengaged state, and the first 146 and the fourth 150 coupling mechanism change from a disengaged state to an engaged state.

[0084] One advantage of this transmission is that only a small number of linkage / locking mechanisms require activation / deactivation during gear changes. Specifically, during single-stage gear changes, only single shifts occur, and during two-stage gear changes, only a double shift occurs, which happens when shifting between first and third forward gears.

[0085] Furthermore, it should also be evident from Table 6 that the second locking mechanism 140, i.e. the positive locking switching element 140, is positioned in a disengaged state in all forward gears and in an engaged state in all reverse gears.

[0086] With further reference to Table 6, the following describes the shifting into reverse gears, in particular into first and second reverse gears R1 and R2. As shown in Table 6, first and second reverse gears R1 and R2 are achieved by three friction shift elements and the positive-locking shift element 140, which are in the engaged state. It should be readily apparent that first and second reverse gears R1 and R2 can be achieved with the same ratio, with only two friction shift elements and the positive-locking shift element 140 in the engaged state. The additional friction shift element engaged in first and second reverse gears R1 and R2 is preferably engaged to reduce chatter in the positive-locking shift element 140.The following describes exemplary embodiments of the method for switching into the first and second reverse gears R1, R2, and in particular which further friction switching element in the form of the first locking mechanism 138 is positioned in the engaged state to reduce the chattering in the positive-locking switching element 140.

[0087] Therefore, reference will be made to Fig. Figures 7-9 illustrate schematic gearshift diagrams for three different gearshifts according to exemplary embodiments thereof. Fig.Figures 7-9 show a corresponding schematic diagram with reference to the desired pressure of the various friction switching elements and the positive-locking switching element, where P_max indicates that the switching element is in a fully engaged state, and P = 0 indicates that the switching element is in a fully disengaged state. The horizontal axis also shows the time frame for executing the corresponding gear shift, with the time frame comprising a variety of points in time described below. It should be readily apparent that the maximum pressure levels are normalized for ease of understanding.

[0088] First, the following will be applied: Fig.Reference is made to Figure 7, which is a schematic illustration of the shift from the first forward gear 1 in Table 6 to the first reverse gear R1 according to an exemplary embodiment. In an initial step, as shown above in Table 6, the first forward gear is obtained by positioning the first 138 and the third 142 locking mechanism and the third linkage mechanism 148 in the engaged state, i.e., arranged in the fully engaged state as defined above. The remaining linkage / locking mechanisms 140, 144, 146, 150 are positioned in the disengaged state. When the gear shift is initiated, the contact pressure of the third locking mechanism 142 and the third linkage mechanism 148 is reduced. In particular, the contact pressure of the third linkage mechanism 148 is reduced to almost zero at a first time point T1 and maintained at this pressure level until an eighth time point T8.The contact pressure of the third locking mechanism 142 is reduced to a low pressure level at a second time point T2, where it is maintained until it is reduced to zero at a fourth time point T4. The first locking mechanism 138 is continuously held in the fully engaged state.

[0089] At time T3, the first connection mechanism 146 initiates engagement. The initiation of engagement is illustrated by a filling pulse beginning at time T3, followed by a ramp function in which the contact pressure is increased until the first connection mechanism 146 is fully engaged at time T6. The first connection mechanism 146 is thus used as a synchronizing switching element for the second connection mechanism 140, i.e., the positive-locking switching element 140. As in Fig.As shown in Figure 7, the positive locking switching element 140 is applied at a fifth time T5, i.e., initiation of engagement, when the differential speed of the positive locking switching element 140 has reached a predetermined limit caused by the increased contact pressure of the first connection mechanism 146.

[0090] According to the in Fig. In the illustrated example 7, the first connection mechanism 146 is fully engaged at the sixth time point T6. The positive-locking switching element 140 is fully engaged at a seventh time point T7.

[0091] Finally, when the positive-locking switching element 140 has been fully engaged, the gear shift into the first reverse gear R1 is completed by increasing the pressure level of the third linking mechanism 148 from the eighth time point T8 to a ninth time point T9, illustrated here by means of two pressure ramps.

[0092] As in Fig. As shown in Figure 7, the contact pressure of the third connection mechanism 148 is reduced to a pressure level of almost zero at the first time point T1. This reduction sufficiently decouples the transmission from the combustion engine, while simultaneously allowing the third connection mechanism 148 to reconnect at the eighth time point T8 without requiring a filling pulse.

[0093] As in Fig.As shown in Figure 7, the first locking mechanism 138, the first 146 and third 148 connecting mechanisms, and the positive-locking switching element 140 are in the engaged state when the first reverse gear R1 is finally engaged at time ninth T9. The first reverse gear R1 can also be derived from Table 6 above. It should be readily apparent that the first reverse gear R1 can be obtained without the first locking mechanism 138 being in the engaged state at time ninth T9. However, keeping the first locking mechanism 138 in the engaged state reduces chatter in the positive-locking switching element 140.

[0094] Now, reference is made to Fig.Figure 8, which is a schematic illustration of the shift from the third forward gear 3 in Table 6 to the first reverse gear R1 according to an exemplary embodiment. In an initial step, as shown above in Table 6, the third forward gear is obtained by positioning the third locking mechanism 142, and the first 146 and fourth 150 coupling mechanisms in the engaged state, i.e., arranged in the fully engaged state as defined above. The remaining coupling / locking mechanisms 138, 140, 148, 144 are positioned in the disengaged state. When the gear shift is initiated, the contact pressure of the third locking mechanism 142 and the fourth coupling mechanism 150 is reduced.In particular, the contact pressure of the fourth connecting mechanism 150 is reduced to zero at a first time point T1, while the contact pressure of the third locking mechanism 142 is reduced to a low pressure level at a second time point T2 and subsequently further reduced to zero at a fourth time point T4. The first connecting mechanism 146 is continuously held in the fully engaged state.

[0095] At time T3, the first locking mechanism 138 initiates engagement. The initiation of engagement is illustrated by a filling pulse initiated at time T3, followed by a ramp function in which the contact pressure is increased until the first locking mechanism 138 is fully engaged at a sixth time T6. The first locking mechanism 138 is thus used as a synchronizing switching element for the second locking mechanism 140, i.e., the positive-locking switching element 140. As in Fig. As shown in Figure 8, the positive locking switching element 140 is applied at a fifth time T5, i.e., initiation of engagement, when the differential speed of the positive locking switching element 140 has reached a predetermined limit caused by the increased contact pressure of the first locking mechanism 138.

[0096] The first locking mechanism 138 is fully engaged at the sixth time point T6. The positive-locking switching element 140 is fully engaged at the seventh time point T7.

[0097] Finally, when the positive-locking switching element 140 is fully engaged, the engagement of the third connection mechanism 148 occurs at an eighth time point T8. The third connection mechanism 148 is engaged by a filling pulse followed by a ramp function, whereby the contact pressure is increased until the third connection mechanism 148 is fully engaged at a ninth time point T9.

[0098] As in Fig.As shown in Figure 8, the first locking mechanism 138, the first 146 and third 148 connecting mechanisms, and the positive-locking switching element 140 are in the engaged state when the first reverse gear R1 is finally engaged at time ninth T9. The first reverse gear R1 can also be derived from Table 6 above. It should be readily apparent that the first reverse gear R1 can be obtained without the first locking mechanism 138 being in the engaged state at time ninth T9. However, keeping the first locking mechanism 138 in the engaged state reduces chatter in the positive-locking switching element 140.

[0099] Now, reference is made to Fig.Figure 9, which is a schematic illustration of the shift from the fourth forward gear 4 in Table 6 to the second reverse gear R2 according to an exemplary embodiment. In an initial step, as shown above in Table 6, the fourth forward gear is obtained by positioning the third locking mechanism 142, the third connecting mechanism 148, and the fourth connecting mechanism 150 in the engaged state, i.e., arranged in the fully engaged state as defined above. The remaining connecting / locking mechanisms 138, 140, 144, and 146 are positioned in the disengaged state. When the gear shift is initiated, the contact pressure of the third locking mechanism 142, the third connecting mechanism 148, and the fourth connecting mechanism 150 is reduced. In particular, the contact pressure of the third connecting mechanism 148 is reduced to zero at a first time T1.The contact pressure of the third locking mechanism 142 is reduced to a low pressure level at a third time point T3, until it is finally reduced to zero at a fifth time point T5. The contact pressure of the fourth connecting mechanism 150 is reduced to almost zero at a second time point T2 and maintained at this pressure level until an eleventh time point T11.

[0100] At a fourth time point T4, the first locking mechanism 138 initiates engagement. The initiation of engagement is illustrated by a filling pulse initiated at the fourth time point T4, which is followed by a ramp function in which the contact pressure is increased until the first locking mechanism 138 is fully engaged at a seventh time point T7.

[0101] At a sixth time point T6, the first connecting mechanism 146 initiates engagement. The initiation of engagement is illustrated by a filling pulse initiated at the sixth time point T6, followed by a ramp function in which the contact pressure is increased until the first connecting mechanism 146 is fully engaged at a ninth time point T9. The first connecting mechanism 146, in combination with the fully engaged first locking mechanism 138, is thus used as a synchronizing switching element for the second locking mechanism 140, i.e., the positive-locking switching element 140. As in Fig.As shown in Figure 9, the positive locking switching element 140 is applied at an eighth time T8, i.e., initiation of engagement, when the differential speed of the positive locking switching element 140 has reached a predetermined limit caused by the increased contact pressure of the first connection mechanism 146.

[0102] The first connecting mechanism 146 is fully engaged at the ninth time point T9. The positive-locking switching element 140 is fully engaged at the tenth time point T10.

[0103] Finally, when the positive-locking switching element 140 has been fully engaged, the fourth connecting mechanism 150 can be fully engaged at a twelfth time T12, as illustrated here by two pressure ramps.

[0104] As in Fig.As shown in Figure 9, the contact pressure of the fourth connection mechanism 150 is reduced to a pressure level of almost zero at the second time point T2. This reduction sufficiently decouples the transmission from the combustion engine, while simultaneously allowing the fourth connection mechanism 150 to reconnect at the eleventh time point T11 without requiring a filling pulse.

[0105] As further in Fig.As shown in Figure 9, the first locking mechanism 138, the first connecting mechanism 146, the fourth connecting mechanism 150, and the positive-locking switching element 140 are in the engaged state when the second reverse gear R2 is finally engaged at time 12. The second reverse gear R2 can also be derived from Table 6 above. It should be readily apparent that the second reverse gear R2 can be obtained without the first locking mechanism 138 being in the engaged state at time 12. However, keeping the first locking mechanism 138 in the engaged state reduces the chatter in the positive-locking switching element 140.

[0106] With the above description of the Fig.Paragraphs 7-9 clearly explain to a person skilled in the art how gear changes from other forward gears to reverse gears, or between corresponding forward or reverse gears, are to be carried out. Consequently, no further description is considered necessary for such gear changes.

[0107] Furthermore, the illustrations in the Fig. Figures 7-9 are to be regarded as schematic representations, where, for example, the ramp functions and filling pulses may take on different forms and longer / shorter time periods may last, etc.

[0108] Furthermore, the first R1 and second R2 reverse gears can also be achieved by first positioning the transmission in a corresponding first and second synchronization gear state. This synchronization gear state enables the positive-locking shift element 140 to synchronize before engaging. The first synchronization gear state preferably has the same overall gear ratio as the first reverse gear R1, and the second synchronization gear state preferably has the same overall gear ratio as the second reverse gear R2. The first synchronization gear state can be achieved by engaging the first locking mechanism 138, the first connecting mechanism 146, and the third connecting mechanism 148.The second synchronization state can be achieved by engaging the first locking mechanism 138, the first connecting mechanism 146 and the fourth connecting mechanism 150.

[0109] Now, the focus will shift to... Fig. 10 Referenced in which a flowchart of a procedure for controlling a gear shift in the above with reference to Fig. The procedure described in Sections 2-6 illustrates the transmissions and, in particular, a case in which the second locking mechanism 140 is designed as a claw clutch. The illustrated procedure can be carried out when shifting from any forward gear into the first R1 or second R2 reverse gear. It should be readily apparent that the Fig. The 10 illustrated process steps should not be interpreted in such a way that they must be carried out in the illustrated successive order, as described below.

[0110] In an initial step S0, the second locking mechanism 140, i.e., the positive-locking switching element 140, is synchronized. This can be achieved by locking the first locking mechanism 138 to the gear housing 160 and by partially engaging, i.e., slipping, the first connecting mechanism 146. This reduces the rotational speed of the planet carrier 104P of the second planetary gear set 104 to a predetermined threshold value. Alternatively, the synchronization of the positive-locking switching element 140 can be achieved by positioning the first connecting mechanism 146 in an engaged state, so that the planet carrier 104P of the second planetary gear set 104 is mechanically connected to the ring gear 106R of the third planetary gear set 106, and by partially engaging, i.e., slipping, the first locking mechanism 138.a slip condition, is positioned so that the rotational speed of the planet carrier 104P of the second planetary gear set 104 falls below the predetermined threshold value. Alternatively, the step of reducing the rotational speed of the planet carrier 104P of the second planetary gear set 104 can be carried out by partially engaging both the first locking mechanism 138 and the first connecting mechanism 146, i.e., allowing them to slip, until the rotational speed of the planet carrier 104P of the second planetary gear set 104 falls below the predetermined threshold value.

[0111] When the rotational speed of the planet carrier 104P of the second planetary gear set 104 is below the predetermined threshold, the positive-locking switching element 140 is engaged. The predetermined threshold should be understood as a rotational speed limit up to which the positive-locking switching element 140 can engage without damaging its components. As a non-limiting example, the rotational speed of the planet carrier 104P should be below 50 revolutions per minute.

[0112] The transmission is now shifted into one of the gears R1, R2, or S1. In addition to the positive-locking shift element 140, at least two friction shift elements are positioned in the engaged state. When the first reverse gear R1 is engaged, the first 146 and the third 148 linkage mechanism are engaged. When the second reverse gear R2 is engaged, the first 146 and the fourth 150 linkage mechanism are engaged.

[0113] However, for both the first R1 and the second R2 reverse gear, there is also another friction switching element, i.e. the first locking mechanism 138, positioned in the engaged state S2 to reduce the rattling of the positive locking switching element 140.

[0114] The steps of shifting the transmission (S1) into one of the gear stages and positioning another friction shift element (S2) in the engaged state do not need to occur in a specific sequence. Consequently, the term "positioning" should be understood to include an element that is already positioned in the engaged state when the process step of shifting the transmission (S1) into the gear stage is executed.

Claims

[1] Method for gear shift control in a transmission (100, 200, 300, 400, 500), wherein the transmission has a plurality of friction shift elements (138, 142, 144, 146, 148, 150) and a positive-locking shift element (140), wherein the plurality of friction shift elements and the positive-locking shift element (138, 142, 144, 146, 148, 150, 140) can be engaged in combinations of three to obtain a plurality of gear stages, characterized by the steps: - Shifting (S1) of the transmission into one (R1, R2) of the plurality of gear stages by positioning two (146, 148; 146, 150) of the plurality of friction shift elements and the positive-locking shift element (140) in an engaged state; and - Positioning (S2) another friction switching element (138) of the plurality of friction switching elements in an engaged state to reduce the chatter of the positive locking switching element (140) in gear stage (R1, R2). [2] Method according to claim 1, characterized by connecting a first part (140a) of the positive locking switching element (140) to a gearbox housing (160) and connecting a second part (140b) of the positive locking switching element (140) to the gearbox housing (160) via the further friction switching element (138). [3] Method according to claim 2, characterized by the connection of a first rotating element (101) of the transmission to the transmission housing (160) by means of the positive-locking switching element (140), and of a second rotating element (103) of the transmission to the transmission housing (160) by means of the further friction switching element (138), and the connection of the first rotating element (101) and the second rotating element (103) to each other by means of one (146) of the two of the plurality of friction switching elements. [4] Method according to any one of the preceding claims, characterized by the step: - Synchronizing (S0) the positive locking switching element (140) by means of the further friction switching element (138), wherein the further friction switching element (138) is held in the engaged state after synchronization. [5] Method according to any one of claims 1 to 3, characterized by the step: - Synchronizing (S0) the positive locking switching element (140) by means of one (146) of the two of the plurality of friction switching elements. [6] Method according to claim 4 or 5, characterized by the step: - Increasing a contact pressure between a pair of friction elements of the friction switching element (138, 146) used for synchronizing the positive locking switching element (140) after initiating the engagement of the positive locking switching element (140). [7] Method according to one of the preceding claims, wherein at least one of the plurality of friction switching elements (148, 150) is designed to connect the transmission to a drive machine, characterized by the step: - Decoupling the drive motor from the transmission by positioning at least one of the plurality of friction switching elements (148, 150) in a disengaged state before shifting the transmission into one (R1, R2) of the plurality of gear stages. [8] Method according to claim 4 or 5 and 7, characterized by the step: - Decoupling the drive motor from the gearbox prior to synchronizing the positive-locking switching element (140). [9] Method according to any one of the preceding claims, characterized by , that one (R1, R2) of the multitude of gear stages is a reverse gear stage. [10] Method according to claim 9, characterized by, that the transmission is shifted into one (R1, R2) of the multitude of gear stages from a forward gear stage. [11] Method according to any one of the preceding claims, characterized by , that the transmission has a first (102), a second (104), a third (106) and a fourth (108) planetary gear set, each comprising a sun gear, a planet carrier and a ring gear. [12] Method according to claims 3 and 11, characterized by , that the first rotating element (101) is functionally connected to the planet carrier (104P) of the second planetary gear set (104), wherein the planet carrier (104P) of the second planetary gear set (104) is further functionally connected to the ring gear (102R) of the first planetary gear set (102), wherein the planet carrier (102P) of the first planetary gear set (102) is functionally connected to an output shaft (112) of the transmission. [13] Method according to claims 3 and 11 or 12, characterized by , that the second rotating element (103) is functionally connected to the ring gear (106R) of the third planetary gear set (106). [14] Method according to any one of claims 11 to 13, characterized by , that the sun gear (104S) of the second planetary gear set (104) is functionally connected to the sun gear (102S) of the first planetary gear set (102). [15] Method according to any one of claims 11 to 14, characterized by , that the planet carrier (106P) of the third planetary gear set (106) is functionally connected to the ring gear (104R) of the second planetary gear set (104). [16] Method according to any one of the preceding claims, characterized by , that the positive locking switching element (140) is a claw coupling. [17] Method according to any one of the preceding claims, characterized by, that seven switching elements (138, 142, 144, 146, 148, 150, 140) can be engaged in combinations of three to obtain nine forward gears and three reverse gears. [18] Control unit (600) for controlling the gearshift in a transmission (100, 200, 300, 400, 500), wherein the transmission has a plurality of friction shift elements (138, 142, 144, 146, 148, 150) and a positive-locking shift element (140); wherein the plurality of friction shift elements and the positive-locking shift element (138, 142, 144, 146, 148, 150, 140) can be engaged in combinations of three to obtain a plurality of gear stages, characterized by , that the control unit (600) is configured to control: - Shifting the transmission into one (R1, R2) of the plurality of gear stages by positioning two (146, 148; 146, 150) of the plurality of friction shift elements and the positive-locking shift element (140) in an engaged state; and - Positioning another friction switching element (138) of the plurality of friction switching elements in an engaged state to reduce the chatter of the positive-locking switching element (140) in gear stage (R1, R2). [19] Vehicle comprising a drive motor, a transmission and a control unit according to claim 18. [20] Computer program comprising program code facilities for performing the steps according to any one of claims 1 to 17 when the program is running on a computer. [21] Computer-readable medium on which a computer program is stored, comprising program code facilities for performing the steps according to any one of claims 1 to 17, when the program code facility is running on a computer. [22] Transmission comprising a plurality of friction switching elements (138, 142, 144, 146, 148, 150) and a positive-locking switching element (140), wherein the plurality of friction switching elements and the positive-locking switching element (138, 142, 144, 146, 148, 150, 140) can be engaged in combinations of three to obtain a plurality of gear stages, characterized by , that at least one (R1, R2) of the plurality of gear stages of the transmission is obtained by positioning two (146, 148; 146, 150) of the plurality of friction switching elements and the positive-locking switching element (140) in an engaged state, and that a further friction switching element (138) of the plurality of friction switching elements for the at least one (R1, R2) gear stage is positioned in the engaged state in order to reduce the chatter of the positive-locking switching element (140) in the gear stage (R1, R2).

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