WO2020108696A1

WO2020108696A1 - Two-gear transmission for an electrically drivable motor vehicle

Info

Publication number: WO2020108696A1
Application number: PCT/DE2019/101002
Authority: WO
Inventors: Ps Satyanarayana; Prajod Ayyappath
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2018-11-28
Filing date: 2019-11-22
Publication date: 2020-06-04
Also published as: DE102018130089A1

Abstract

The invention relates to a two-gear transmission for an electrically drivable motor vehicle, comprising an input shaft (12) which can be connected to an electric machine for the introduction of a torque, an output shaft (18) which can be connected to a drive gear for the output of the torque, a first gear stage (14) for the transmission of a rotational speed of the input shaft (12) to the output shaft (18) with a first transmission ratio, with a first driving gearwheel (20) and a first driven gearwheel (22), a second gear stage (16) for the transmission of a rotational speed of the input shaft (12) to the output shaft (18) with a second transmission ratio which is different from the first transmission ratio, with a second driving gearwheel (24) and a second driven gearwheel (26), a first freewheel (28) which is assigned to the first driving gearwheel (20) or the first driven gearwheel (22), and a friction clutch (30) which can connect the second driven gearwheel (24) to the output shaft (18). In order to be able to design the transmission in an even more compact manner and to enable it for recuperation operation, it is proposed that this friction clutch (30) is 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

Two-Ganq transmission for an electrically drivable motor vehicle

The invention relates to a two-speed gearbox for an electrically drivable 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, 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 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, the is associated with the first driving gear or the first driven gear, 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, i.e. for two-wheelers, such as bicycles, mopeds, scooters or motorcycles, for tricycles, such as rickshaws, or for "normal" vehicles with four wheels, from light vehicles to City bus.

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 in a high speed range a low gear ratio Tongue ratio can be provided in order to realize 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 EP 2 305 501 A1 a two-speed transmission 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 transmitting the torque, a first gear stage for translating a speed of the input shaft to the Output shaft with a first gear ratio, with a first driving gear and a first driven gear, a second gear stage for translating a 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 one-way clutch associated with the first driving gear or the first driven gear and a friction clutch that can connect the second driven gear to the output shaft. This Ge gear forms the preamble of claim 1. However, the transmission of the prior art contains two friction clutches to be operated and a separate circlip Si, so that it builds relatively large and the gear change is relatively complicated.

It is an object of the invention to show measures which lead to a compact and, thanks to recuperation, economical two-speed transmission 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 the is assigned to the first driving gear or the first driven gear, and a friction clutch that can connect the second driven gear to the output shaft, this friction clutch being the only one Ge friction clutch is provided, wherein the first freewheel and the friction clutch are both arranged on the same shaft, namely the input shaft or the output shaft, and wherein 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, the shifting is smooth and seamless, whether it is 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 has many advantages with regard to the reduced energy energy consumption, increased driving comfort, incline and top speed.

Avoiding a shift gap (uninterrupted power flow when changing gears) increases performance and offers a superior driving experience. The integration according to the invention 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, which 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 specific 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-plate 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 gear is switched 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 tigt, grips 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 seen before and that this single friction clutch and the freewheel according to the invention are arranged on a single common shaft minimizes the space required by the transmission.

According to the invention, a second freewheel is now provided, which is preferably effective in the two-th gear. 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 it locks in push mode (drive from the drive wheel to the electric motor), i.e. transmits the torque and thus torque from Drive wheel returns 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 a multi-stage transmission. 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. 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 blockage 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.

Within the scope 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 particularly simple 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 coupling housing profile, that is to say a spline, and is arranged in a rotationally fixed manner on the output shaft 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). Flebel 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 that are released when released - i.e. no torque transmission - and grip with a pressed pin - i.e. torque transmission are common. The friction clutch can be operated mechanically by hand or foot. However, an electrical actuation is particularly preferred which converts the rotary motion of an electric (servo) motor into a reciprocating motion of a clutch actuation via an electromechanically acting actuator (actuator) and thus opens and closes the coupling in cooperation with prestressed springs.

In the following, the invention is explained by way of example with reference to the accompanying 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 shows a section through an inventive two-speed transmission in first gear, 2: a section through the two-speed transmission of FIG. 1 in the second gear,

3: a section through the two-speed transmission of FIG. 1 in the recuperation mode,

4: a perspective view of a motor-gear unit,

5: a rotating component of the two-speed transmission of FIG. 1,

6: the rotating component of FIG. 5,

7: another rotating component of the two-speed transmission of FIG. 1,

The two-speed transmission 10 shown in FIG. 1 has an input shaft 12, which can be connected to a motor shaft of an electric machine of a motor vehicle in a rotational test. The input shaft 12 can be coupled via a first gear stage 14 and a second gear stage 16 with different transmission ratios to an output shaft 18 in order to drive a drive wheel of the motor vehicle coupled to the output shaft 18. On the output shaft 18, a drive roller 44 is provided for this purpose, which 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 stage 14 has a first driven gear 20, which is arranged as a fixed gear on the input shaft 12 and meshes with a first driven gear 22 connected to the output shaft 18. The second gear stage 16 has a second driving gear 24, which is arranged as a fixed gear on the input shaft 12 and meshes with a second driven gear 26 connected to the output shaft 18. According to the invention, the first freewheel 28, the only friction clutch 30 and the second freewheel 36 are now located on the output shaft 18. The friction clutch 30 has a clutch housing 40 with the clutch housing profile 42, which is connected in a rotationally fixed manner to the output shaft 18. For actuation, the friction clutch 30 has a central release pin 32 which can be actuated via a clutch actuation mechanism 34.

To explain the function of the transmission 10 according to the invention, FIG. 1 shows the power flow (dotted line) in first gear. The motor drives the input shaft 12 with the two fixed gears 20 and 24. The clutch actuating mechanism 34 has moved upwards into its starting position and does not touch the release pin 32 or only very slightly with its flattened operating surface. The internal Spring forces of the friction clutch 30 keep the friction elements away from one another (see arrows and open lock on the right in FIG. 1). The friction clutch 30 is thus open and does not transmit any torque. The clutch actuation mechanism here is a simple electric one, which generates an outward and lubricating movement electromechanically, for example by rotating a spindle, and thus opens or closes the clutch 30. The torque of the motor flows when the friction clutch 30 is open via the first gearwheels 20 and 22. The gearwheel 22 guides the rotational movement via the locking first freewheel 28 onto the clutch housing 40 and there via the internal toothing of the clutch housing profile 42 onto the output shaft 18, like the dotted one Line shows. That the interior of the clutch 30 rotates at a different speed than the clutch housing 40 is irrelevant, since the clutch 30 is open, so does not transmit any torque. The second freewheel 36 on the output shaft 18 within the friction clutch 30 is overrun here when driven by the motor and serves only as a bearing for the output shaft 18. The second freewheel 36 thus enables a controlled regeneration of kinetic energy to the electric motor working as a generator. when the direction of power flow reverses, torque is initiated by the drive wheel and the second freewheel 36 locks.

FIG. 2 shows the power flow of the transmission 10 according to the invention from FIG. 1 in the second (faster) gear (super boost). The motor drives the input shaft 12 with the fixed wheels 20 and 24 (power flow line top left). The clutch actuation mechanism 34 is now moved down into its closed position and presses the release pin 32 against the internal spring forces with its flattened actuating surface. As a result, the clutch discs and the friction elements lie on top of one another (see arrows and closed lock on the right in FIG. 2). The friction clutch 30 is now closed and transmits the torque. The torque of the motor now flows via the friction clutch 30 from the second gears 24 and 26 of the second gear 16 into the clutch housing 40 and from there via the internal toothing of the clutch housing profile 42 to the output shaft 18 and from there to the drive roller 44, such as the dotted line with the two arrows. The first freewheel 28 is now overhauled, since the speed via the second gear stage 16 of the gears 24 and 26 is faster than the rotational speed of the first gear stage 14 of the gears 20 and 22. The first freewheel 28 is here from the outside - rolling over or overtaking - io

driven, in contrast to the position in Fig. 1, where the force or torque come from within, so use the locking effect. The inventive integration of the first freewheel 28 and clutch 30 on a shaft 18 thus leads to a very compact design. The slow engagement and the slow rollover of the first freewheel 28 lead to a smooth gear change without jerk. Here, too, the second freewheel 36 enables a controlled regeneration of kinetic energy to the motor working as a generator if the direction of power flow reverses, torque is introduced from the drive wheel and the second freewheel 36 locks.

3 shows the power flow (dotted line) of the transmission 10 according to the invention in the regeneration mode. Now the motor does not drive via the input shaft 12, but the torque is introduced from the drive wheel via the drive roller 44 into the output shaft 18 (push operation when driving downhill or slowing down), as the two arrows below and in the output shaft 18 show. The clutch actuation mechanism 34 has moved upwards into its starting position and does not touch the release pin 32 or only slightly with its flattened actuating surface. The internal spring forces of the friction clutch 30 keep the clutch plates and friction elements apart. Thus, the friction clutch 30 is open and carries no torque. The torque of the drive roller 44 flows via the second freewheel 36, which locks in this direction of rotation, via the gears 26 and 24 of the second gear stage 16, further via the input shaft 12 to the motor, 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.

FIG. 4 shows a perspective view of a motor-gear unit, consisting of the electric motor 56 and the flanged-on two-speed gear 10 according to the invention. With the aid of this toothed belt, the power of the electric motor 56 is applied to a drive wheel (also not shown) Electric two-wheeler - or via a differential to two drive wheels, for example a rickshaw.

FIG. 5 shows a rotating component of the two-speed transmission 10 from FIG. 1, namely the assembly integrated according to the invention from the first freewheel 28, friction clutch 30 and the second driven gear 26 as a compact, integrated component. It can be clearly seen that the freewheel 28 is integrated in the clutch housing 40. The springs of the clutch 30 can be seen. The second driven gear 26 is integrated here in the area or on the side of the clutch actuation.

Fig. 6 shows the rotating component of Fig. 5 from another side. The roller elements of the first freewheel 28, the clutch housing 40 with the clutch housing profile 42, the friction clutch 30 and the second driven gearwheel 26 can be seen.

FIG. 7 shows a further rotating component of the two-speed transmission 10 from FIG. 1, namely the rotating component of FIGS. 5 and 6, supplemented by the first driven gear wheel 22. The perspective gear section of FIG. 22 shows the gear wheels of FIG and 26, the first freewheel 28 and the second freewheel 36, all well integrated here in or on the friction clutch 30. The second freewheel 36 and the needle bearing 58 serve to support the output shaft, not shown here.

Reference list two-speed gearbox

Input shaft

first gear

second gear

Output shaft

first driving gear

first driven gear

second driving gear

second driven gear

first freewheel

Friction clutch

Release pin

Clutch actuation mechanism second freewheel

Clutch housing

Clutch housing profile

Drive roller

Electric motor

Needle bearing

Claims

1. Two-speed transmission for an electrically drivable motor vehicle with

an input shaft (12) connectable 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 translating a rotational 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) associated with the first driving gear (20) or the first driven gear (22), and

a friction clutch (30) which can connect the second driven gear (24) to the output shaft (18),

characterized in that this friction clutch (30) is provided as the only friction clutch (30) and in that the first freewheel (28) and the friction clutch (30) are both arranged on the same shaft (input shaft 12 or output shaft 18) and that a second freewheel (36) is provided.

2. Two-speed transmission according to claim 1, characterized in that the first te driving gear (20) and the second driving gear (24) fixed gears on a shaft, preferably the input shaft (12).

3. Two-speed transmission according to claim 1 or 2, characterized in that the first freewheel (28) is integrated in a clutch housing (40).

4. Two-speed transmission according to one of claims 1 to 3, characterized in that the hub of the first driven gear (22) is also the hub of the first freewheel (28).

5. Two-speed transmission according to one of claims 1 to 4, characterized in that the second driven gear (26) is located on the side of the clutch actuation.

6. Two-speed transmission according to one of claims 1 to 5, characterized in that the clutch housing (40) with a clutch housing profile (42) is fixedly arranged on the output shaft (18).

7. Two-speed transmission according to one of 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).

8. Two-speed transmission according to one of claims 1 to 7, characterized in that the second freewheel (36) is located within the friction clutch (30) be.

9. Two-speed transmission according to one of claims 1 to 8, characterized in that the clutch actuation mechanism (34) operates electrically.

10 two-speed transmission according to claim 9, characterized in that the clutch actuating mechanism (34) includes a servomotor and a mechanism which converts the rotary movement of the servomotor into a reciprocating movement of an actuating element.