DE102018130089A1 - Two-speed gearbox for an electrically drivable motor vehicle - Google Patents

Abstract

The invention proposes a two-speed transmission for an electrically drivable motor vehicle, with an input shaft (12) that can be connected to an electrical machine for introducing a torque, an output shaft (18) that can be connected to a drive wheel for deriving the torque, a first gear stage (14 ) to translate a speed of the input shaft (12) to the output shaft (18) with a first gear ratio, with a first driving gear (20) and a first driven gear (22), a second gear stage (16) for translating a speed of the input shaft (12) to the output shaft (18) with a second gear ratio different from the first gear ratio, with a second driving gear (24) and a second driven gear (26), a first freewheel (28) which connects the first driving gear (20) or associated with the first driven gear (22), and a friction clutch (30) which drives the second In order to be able to make the gearbox even more compact and to make it capable of recuperation, it is proposed that this friction clutch (30) be provided as the only friction clutch (30) that the first freewheel ( 28) and the friction clutch (30) are both arranged on the same shaft and that a second freewheel (36) is provided.

Description

The invention relates to a two-speed transmission for an electrically drivable motor vehicle, with the aid of which an output of an electrical machine can be converted. The invention relates to a two-speed gearbox for electric vehicles, having an input shaft that can be connected to an electrical machine for introducing a torque, an output shaft that can be connected to a drive wheel for transmitting the torque, a first gear stage for translating a speed of the input shaft to the output shaft with a first transmission ratio, with a first driving gear and a first driven gear, a second gear stage for translating a rotational speed of the input shaft to the output shaft with a second gear ratio different from the first gear ratio, with a second driving gear and a second driven gear, a first freewheel that corresponds to the first driving gear or the first driven gear is assigned, and a friction clutch that can connect the second driven gear to the output shaft. The invention is suitable for electrically assisted or purely electrically powered vehicles with batteries, that is to say for two-wheelers, such as bicycles, mopeds, scooters or motorcycles, for three-wheelers, such as rickshaws, or for “normal” vehicles with four wheels, from light vehicles to city buses.

When accelerating an electrically drivable motor vehicle from a standing start, an electrical machine can first accelerate from standstill with a substantially constant torque up to a basic speed. When the basic speed is reached, the drive power of the electrical machine remains essentially constant, so that the torque decreases for a higher speed. In order to achieve a large torque and speed spread, a two-speed transmission can be provided which provides different transmission ratios. Thus, a high gear ratio can be provided in a low speed range in order to provide the highest possible torque for acceleration, while a low gear ratio can be provided in a high speed range in order to be able to implement the highest possible vehicle speed. Compared to direct drives or single-speed drives, two-speed gearboxes keep the engine in its most efficient range over long distances in every driving cycle. This also ensures lower consumption - and emissions if an internal combustion engine or a hybrid is also used.

From the EP 2 305 501 A1 A two-speed gearbox for electric vehicles is known, with an input shaft that can be connected to an electrical machine for introducing a torque, an output shaft that can be connected to a drive wheel for discharging the torque, a first gear stage for translating a speed of the input shaft to the output shaft with a first transmission ratio a first driving gear and a first driven gear, a second gear stage for translating a rotational speed of the input shaft to the output shaft with a second gear ratio different from the first gear ratio, with a second driving gear and a second driven gear, a freewheel, the first driving gear or associated with the first driven gear, and a friction clutch that can connect the second driven gear to the output shaft. This transmission forms the preamble of claim 1. However, the transmission of the prior art contains two friction clutches to be operated and a separate locking ring, so that it has a relatively large construction and the gear change is relatively complicated.

It is the object of the invention to show measures which lead to a compact two-speed transmission which is more economical thanks to recuperation in an electrically drivable motor vehicle.

The object is achieved according to the invention by a two-speed transmission with the features of claim 1. Preferred embodiments of the invention are specified in the subclaims and the following description, which can each represent an aspect of the invention individually or in combination.

According to the invention, a two-speed gearbox for electric vehicles is proposed, with an input shaft that can be connected to an electrical machine for introducing a torque, an output shaft that can be connected to a drive wheel for transmitting the torque, a first gear stage for translating a speed of the input shaft to the output shaft with a first transmission ratio, with a first driving gear and a first driven gear, a second gear stage for translating a rotational speed of the input shaft to the output shaft with a second gear ratio different from the first gear ratio, with a second driving gear and a second driven gear, a first freewheel that corresponds to the first driving gear or the first driven gear is assigned, and a friction clutch that can connect the second driven gear to the output shaft, this friction clutch as the only one e friction clutch is provided, the first freewheel and the friction clutch are both arranged on the same shaft, namely the input shaft or the output shaft, and a second freewheel is provided

The two-speed transmission according to the invention has a simpler structure due to the absence of a second friction clutch and can therefore be made smaller. Eliminating the second friction clutch on the other shaft makes the transmission smaller, lighter, cheaper and less complex. Saving mass is advantageous. Shifting is easier because only a single clutch can be operated and a separate circlip system can be dispensed with. The inventors have recognized that this simpler solution also enables smooth, jerk-free switching, which can preferably be carried out automatically. Since a first freewheel is used, switching is smooth and seamless, whether mechanical or automatic. Since there are not two or three elements to be operated when shifting, a single simple electrical, electromechanical, electronic or hydraulic servomotor is sufficient to change gear.

With the proposed invention, a battery-electric vehicle can be realized that switches automatically and offers many advantages in terms of reduced energy consumption, increased driving comfort, the ability to climb and the maximum speed.

Avoiding a shift gap (uninterrupted power flow when changing gears) increases performance and offers a superior driving experience. The inventive integration of the first freewheel and friction clutch leads to a smooth, smooth automatic shifting process. With the new transmission, the powertrain can be designed to be electrically smaller and still achieve high torque, which leads to a vehicle characteristic with high energy efficiency.

In particular, a control device can be provided that is designed to automatically change gear when a certain predefined threshold driving speed of the motor vehicle is exceeded and / or undershot and / or when a certain predefined threshold torque of the input shaft is exceeded and / or undershot. As a result, a suitable gear ratio can be switched automatically for the respective driving situation, without the driver of the motor vehicle having to do this manually.

A multi-disc clutch can be used as the friction clutch, which automatically engages or disengages depending on the vehicle speed or the load conditions. This quickly synchronized soft engagement or disengagement leads to a "short" slip zone during the transition from first to second gear and thus a quick gear change. The clutch can be operated purely electrically.

During starting and at low speeds, the new clutch mechanism fully opens and holds the only friction clutch so that the friction elements are separated from each other and do not transmit power. When the engine or vehicle speed increases, the vehicle switches to second gear, which is done by engaging the friction clutch and overtaking the first freewheel, which no longer transmits power as a result. During the upshift from first to second gear, the only friction clutch is actuated slowly, so it engages more and more until the torque transmitted by the clutch corresponds to the engine torque. The gear change is so smooth and without any jerk. Even if the engine torque is then reduced, the vehicle is in second gear, in which the first freewheel is overtaken or overrun.

Since the switching frequency is generally low and the first gear is actually only used for starting off or on the mountain, the second gear is usually engaged. Since, according to the invention, the only friction clutch does not have a long-lasting slip, but grips firmly, there is no risk of overheating in continuous operation. The thermal capacity of the friction clutch therefore does not have to be high, so that a smaller, relatively compact clutch can also be used.

The fact that only a single friction clutch - instead of two in the prior art - is provided and that this single friction clutch and the freewheel according to the invention are arranged on a single common shaft minimizes the space requirement of the transmission.

According to the invention, a second freewheel is now provided, which is preferably effective in the second gear stage. It is installed in such a way that during normal driving (drive from the electric motor to the drive wheel) it runs freely, i.e. it only acts as a bearing and does not transmit any torque, but in push mode (drive from the drive wheel to the electric motor) it locks, i.e. transfers the torque and thus torque from the drive wheel leads back to the electric motor so that the electric motor can act as a generator, recover electrical energy and store it in the battery. This increases the efficiency of the drive, making it more economical, or increasing the range. According to the invention, a soft-shifting two-speed transmission with a recuperation function is therefore achieved, so that it is competitive against single-stage gearboxes. A battery-powered vehicle with the transmission according to the invention is particularly pleasant when it switches automatically. It uses less energy and increases driving comfort, climbing ability and top speed.

• - Langsam fahren, Anfahren oder Bergauffahren im ersten Gang
• - Schnell fahren im 2. Gang
• - Neutralstellung (beim Langsamerwerden oder Bergabfahren, Segelmodus durch Öffnen der Reibungskupplung)
• - Energierekuperation durch Zurückleiten von Drehmoment vom Antriebsrad an den als Generator wirkenden Elektromotor und
• - Parkblockierstellung (durch Eingreifen der Reibungskupplung bei ausgeschaltetem Elektromotor)

The combination according to the invention of two freewheels, preferably of roller locks and / or sleeve freewheels (HFL, chiplessly manufactured roller freewheels, drawn cup roller locks), with a single friction clutch with the new clutch holding mechanism allows different operating modes with their different operating positions, namely:

• - Drive slowly, start off or go uphill in first gear
• - Driving fast in 2nd gear
• - Neutral position (when slowing down or driving downhill, sailing mode by opening the friction clutch)
• - Energy regeneration by returning torque from the drive wheel to the electric motor and
• - Parking blocking position (by engaging the friction clutch when the electric motor is switched off)

The parking lock can be achieved in that when the vehicle and the engine have come to a standstill, the friction clutch is engaged and at the same time a freewheel blocks a movement in the opposite direction. This saves a separate mechanism for the parking brake and an extra actuating element.

In the context of the invention, the clutch and the freewheel can be arranged on the input shaft or on the output shaft. However, it is preferred to provide the clutch and freewheel on the output shaft. Then the input shaft can be constructed in a particularly simple manner and contain the first driving gear and the second driving gear as fixed gears.

Clutch and freewheels can be arranged side by side on their common shaft. In a preferred embodiment, the first or both freewheels and the friction clutch can be integrated in a common housing. It is particularly suitable if the clutch housing of the friction clutch is used for this purpose. This results in a particularly space-saving, compact construction of the invention. The friction clutch, freewheels and the two driven gears then form a compact unit that takes up little space.

The first freewheel is preferably integrated into the first driven gear, in that the hub of the first freewheel is also the hub of the gear. This also leads to a particularly compact design.

The construction is even more space-saving and compact if the second driven gearwheel is located directly at the clutch, preferably on the side of the clutch actuation.

It is also particularly space-saving if the clutch housing is provided with a clutch housing profile, that is to say a spline, and is arranged on the output shaft in a rotationally fixed manner in order to transmit torque to the output shaft.

The friction clutch, like any other clutch known per se, can be operated by hand, foot or actuator operation (engaging, disengaging). Levers or cables can be used. A release pin (pin or pin) arranged centrally in the middle of the clutch can preferably be provided, which can be engaged or released by pressing or releasing the clutch. Spring preloaded clutches are common, which are released when released - i.e. do not transmit torque - and grip with a pressed pin - i.e. transmit torque. The friction clutch can be operated mechanically by hand or foot. However, electrical actuation is particularly preferred, which converts the rotary movement of an electric (servo) motor into a reciprocating movement of a clutch actuation via an electromechanically acting actuator (actuator) and thus opens and closes the clutch in cooperation with preloaded springs.

• 1: einen Schnitt durch ein erfindungsgemäßes Zwei-Gang-Getriebe im ersten Gang,
• 2: einen Schnitt durch das Zwei-Gang-Getriebe der 1 im zweiten Gang,
• 3: einen Schnitt durch das Zwei-Gang-Getriebe der 1 im Rekuperationsbetrieb,
• 4: eine perspektivische Ansicht einer Motor-Getriebeeinheit,
• 5: ein rotierendes Bauteil des Zwei-Gang-Getriebes der 1,
• 6: das rotierende Bauteil der 5,
• 7: ein weiteres rotierendes Bauteil des Zwei-Gang-Getriebes der 1,

In the following, the invention is explained by way of example with reference to the attached drawings using preferred exemplary embodiments, the features shown below being able to represent an aspect of the invention both individually and in combination. Show it:

• 1 : a section through an inventive two-speed transmission in first gear,
• 2nd : a cut through the two-speed gearbox of the 1 in second gear,
• 3rd : a cut through the two-speed gearbox of the 1 in recuperation mode,
• 4th : a perspective view of a motor gear unit,
• 5 : a rotating component of the two-speed gearbox 1 ,
• 6 : the rotating component of the 5 ,
• 7 : another rotating component of the two-speed gearbox 1 ,

This in 1 illustrated two-speed transmission 10th has an input shaft 12 on, which can be rotatably connected to a motor shaft of an electrical machine of a motor vehicle. The input shaft 12 can have a first gear 14 and a second gear 16 with different gear ratios with an output shaft 18th be coupled to one with the output shaft 18th to drive the coupled drive wheel of the motor vehicle. On the output shaft 18th is a driving role for this 44 provided that transmits the torque to the drive wheel via a (not shown) belt. It is also possible to use sprockets and a chain. The first gear 14 has a first driven gear 20th on that as a fixed gear on the input shaft 12 is arranged and with one with the output shaft 18th connected first driven gear 22 combs. The second gear 16 has a second driving gear 24th on that as a fixed gear on the input shaft 12 is arranged and with one with the output shaft 18th connected second driven gear 26 combs. On the output shaft 18th are now the first freewheel according to the invention 28 , the only friction clutch 30th and the second freewheel 36 . The friction clutch 30th has a clutch housing 40 with the clutch housing profile 42 , which rotates with the output shaft 18th connected is. The friction clutch has for actuation 30th a central release pin 32 on that via a clutch actuation mechanism 34 can be operated.

To explain the function of the transmission according to the invention 10th shows 1 the power flow (dotted line) in first gear. The motor drives the input shaft 12 with the two fixed wheels 20th and 24th . The clutch actuation mechanism 34 has moved up to its starting position and touches the release pin with its flattened actuating surface 32 not or only very slightly. The internal spring forces of the friction clutch 30th keep the friction elements away from each other (see arrows and open lock right in 1 ). So that is the friction clutch 30th open and does not transmit torque. The clutch actuation mechanism here is a simple electrical one, which generates a reciprocating motion electromechanically, for example by rotating a spindle, and thus the clutch 30th opens or closes. The engine torque flows when the friction clutch is open 30th about the first gears 20th and 22 . The gear 22 directs the rotary motion over the blocking first freewheel 28 on the clutch housing 40 and there over the internal toothing of the clutch housing profile 42 on the output shaft 18th as the dotted line shows. That the inside of the clutch 30th rotates at a different speed than the clutch housing 40 , doesn't matter because the clutch 30th yes is open, so does not transmit a moment. The second freewheel 36 on the output shaft 18th inside the friction clutch 30th is overrun here when the motor drives and only serves as a bearing for the output shaft 18th . Through the second freewheel 36 In this way, a controlled regeneration of kinetic energy to the electric motor working as a generator is possible if the direction of force flow reverses, torque is initiated by the drive wheel and the second freewheel 36 locks.

2nd shows the power flow of the transmission according to the invention 10th the 1 in second (faster) gear (Super Boost). The motor drives the input shaft 12 with the two fixed wheels 20th and 24th (Force flow line top left). The clutch operating mechanism 34 has now moved down to its closed position and presses the release pin with its flattened actuating surface 32 against the internal spring forces. As a result, the clutch discs and the friction elements lie on top of each other (see arrows and closed lock on the right in 2nd ). The friction clutch 30th is now closed and transmits the torque. The engine torque now flows through the friction clutch 30th from the second gears 24th and 26 the second gear 16 into the clutch housing 40 and from there via the internal toothing of the clutch housing profile 42 on the output shaft 18th and from there to the drive roller 44 , as the dotted line with the two arrows shows. The first freewheel 28 will now be overhauled because the speed over the second gear 16 of the gears 24th and 26 is faster than the speed of the first gear 14 of the gears 20th and 22 . The first freewheel 28 is driven from the outside - rolling over or overtaking - in contrast to the position in 1 , where the force or the torque come from inside, so use the locking effect. The inventive integration of the first freewheel 28 and clutch 30th on a wave 18th therefore leads to a very compact design. The slow engagement and the slow rolling over of the first freewheel 28 lead to a smooth gear change without jerk. Here too is through the second freewheel 36 A controlled regeneration of kinetic energy to the motor working as a generator is possible if the direction of power flow reverses, torque is initiated by the drive wheel and the second freewheel 36 locks.

3rd shows the power flow (dotted line) of the transmission according to the invention 10th in regeneration mode. Now the motor does not drive over the input shaft 12 , but the torque is from the drive wheel via the drive roller 44 into the output shaft 18th initiated (push operation when driving downhill or slow down), like the two arrows below and in the output shaft 18th demonstrate. The clutch operating mechanism 34 has moved up to its starting position and touches the release pin with its flattened actuating surface 32 not or only slightly. The internal spring forces of the friction clutch 30th keep the clutch discs and friction elements apart. So that is the friction clutch 30th open and does not transmit torque. The torque of the drive roller 44 flows over the second freewheel which locks in this direction of rotation 36 about the gears 26 and 24th the second gear 16 , continue over the input shaft 12 to the engine, as the dotted line shows. In this operating state, the electric motor works as a generator and converts the torque into electrical voltage or current and can thus charge the battery. A regeneration mode is thus achieved without any special additional effort. The second freewheel facilitates regeneration in first gear, the friction clutch facilitates regeneration in second gear.

4th shows a perspective view of a motor-transmission unit, consisting of the electric motor 56 and the flanged two-speed transmission according to the invention 10th . The drive roller is on the left 44 to recognize, which is designed here for operation with a toothed belt, not shown. With the help of this toothed belt, the performance of the electric motor 56 to a drive wheel of an electric two-wheeler, also not shown - or via a differential to two drive wheels, for example a rickshaw.

5 shows a rotating component of the two-speed transmission 10th out 1 , namely the integrated unit according to the invention from the first freewheel 28 , Friction clutch 30th and second driven gear 26 as a compact, integrated component. It is easy to see that the freewheel 28 into the clutch housing 40 is integrated. You can see the springs of the clutch 30th . The second driven gear 26 is integrated here in the area or on the side of the clutch actuation.

6 shows the rotating component of the 5 from another side. You can see the roller elements of the first freewheel 28 , the clutch housing 40 with the clutch housing profile 42 who have favourited Friction Clutch 30th and the second driven gear 26 .

7 shows another rotating component of the two-speed transmission 10th out 1 , namely the rotating component of the 5 and 6 , supplemented by the first driven gear 22 . The gears can be seen in this perspective partial sectional view 22 and 26 , the first freewheel 28 and the second freewheel 36 , all well integrated here in or on the friction clutch 30th . The second freewheel is used to support the output shaft, not shown here 36 and the needle bearing 58 .

Reference symbol list

10th

Two-speed transmission

12

Input shaft

14

first gear

16

second gear

18th

Output shaft

20th

first driving gear

22

first driven gear

24th

second driving gear

26

second driven gear

28

first freewheel

30th

Friction clutch

32

Release pin

34

Clutch actuation mechanism

36

second freewheel

40

Clutch housing

42

Clutch housing profile

44

Drive roller

56

Electric motor

58

Needle bearing

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2305501 A1 [0003]

Claims (10)

Two-speed gearbox for an electrically drivable motor vehicle with an input shaft (12) which can be connected to an electrical machine for introducing a torque, an output shaft (18) which can be connected to a drive wheel for deriving the torque, a first gear stage (14) for the translation of a speed the input shaft (12) to the output shaft (18) with a first gear ratio, with a first driving gear (20) and a first driven gear (22) of a second gear stage (16) for translating a speed of the input shaft (12) to the output shaft (18) with a second gear ratio different from the first gear ratio, with a second driving gear (24) and a second driven gear (26), a first freewheel (28), which is the first driving gear (20) or the first driven gear (22 ) is assigned, and a friction clutch (30), the second driven gear (24) with the off can connect gear shaft (18), characterized in that this friction clutch (30) is provided as the only friction clutch (30) and that the first freewheel (28) and the friction clutch (30) are both on the same shaft (input shaft 12 or output shaft 18) are arranged and that a second freewheel (36) is provided. Two-speed gearbox after Claim 1 , characterized in that the first driving gear (20) and the second driving gear (24) are fixed gears on a shaft, preferably the input shaft (12). Two-speed gearbox after Claim 1 or 2nd , characterized in that the first freewheel (28) is integrated in a clutch housing (40). Two-speed gearbox according to one of the Claims 1 to 3rd , characterized in that the hub of the first driven gear (22) is also the hub of the first freewheel (28). Two-speed gearbox according to one of the Claims 1 to 4th , characterized in that the second driven gear (26) is on the clutch actuation side. Two-speed gearbox according to one of the Claims 1 to 5 , characterized in that the clutch housing (40) with a clutch housing profile (42) is rotatably arranged on the output shaft (18). Two-speed gearbox according to one of the Claims 1 to 6 , characterized in that the clutch is actuated by pressing a release pin (32) arranged centrally on the output shaft and in the middle of the clutch (30). Two-speed gearbox according to one of the Claims 1 to 7 , characterized in that the second freewheel (36) is also located within the friction clutch (30). Two-speed gearbox according to one of the Claims 1 to 8th , characterized in that the clutch actuation mechanism (34) operates electrically. Two-speed gearbox after Claim 9 , characterized in that the clutch actuating mechanism (34) includes an actuator and a mechanism that converts the rotary motion of the actuator into a reciprocating motion of an actuator.

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