PARALLEL HYBRID DRIVE FOR A MOTOR VEHICLE, MOTOR VEHICLE, AND METHOD FOR OPERATING A PARALLEL HYBRID DRIVE

Abstract

Disclosed is parallel hybrid drive for a motor vehicle, a motor vehicle, a method for operating a parallel hybrid drive in an all-electric mode, a method for operating a parallel hybrid drive in a direct drive mode, and a method for operating a parallel hybrid drive in a CVT mode. The drive for a motor vehicle includes an electric machine operable as a motor and generator, an internal combustion engine, a drive axle, and an epicyclic gear. The epicyclic gear includes: a first shaft connected to the electric machine; a second shaft connected to the internal combustion engine; and a third shaft connected to the drive axle. A clutch element is configured to firmly connect at least two shafts of the epicyclic gear to each other. A first brake element is configured to prevent rotation of the internal combustion engine in one direction of rotation.

Claims

1. A parallel hybrid drive for a motor vehicle, comprising: an electric machine operable as a motor and a generator; an internal combustion engine; a drive axle; an epicyclic gear comprising: a first shaft which is connected to the electric machine; a second shaft which is connected to the internal combustion engine; and a third shaft, which is connected to the drive axle; a clutch element which is configured to firmly connect at least two shafts of the epicyclic gear to each other; and a first brake element which is designed to prevent rotation of the internal combustion engine in one direction of rotation.

2. The parallel hybrid drive according to claim 1, wherein the first clutch element is configured to switch automatically.

3. The parallel hybrid drive according to claim 1, wherein the first clutch element is configured to switch based on a rotational speed of the third shaft of the epicyclic gear.

4. The parallel hybrid drive according to claim 1, wherein the first clutch element is configured as a centrifugal clutch.

5. The parallel hybrid drive according to claim 1, wherein the first brake element is configured to switch automatically, in particular wherein the first brake element is configured as a freewheel.

6. The parallel hybrid drive according to claim 1, wherein the first shaft is a ring gear shaft, the second shaft is a sun gear shaft, and the third shaft is a carrier shaft.

7. The parallel hybrid drive according to claim 1, wherein the electric machine is configured to control a rotational speed of the internal combustion engine when the clutch element is open.

8. The parallel hybrid drive according to claim 1, further comprising a throttle valve control configured to adjust a torque of the internal combustion engine at a speed specified by the electric machine.

9. The parallel hybrid drive according to claim 8, wherein the throttle valve control is configured as directly mechanical.

10. The parallel hybrid drive according to claim 1, further comprising an energy storage device configured to supply the electric machine with electric energy and to be charged by the electric machine, and a second brake element configured to block the drive axle during a stationary charging operation of the energy storage device.

11. The parallel hybrid drive according to claim 10, wherein the electric machine is configured to start the internal combustion engine from a standstill when the drive axle is blocked.

12. A motor vehicle, configured as a motorcycle, comprising the parallel hybrid drive according to claim 1 and a rear wheel which can be driven by the parallel hybrid drive.

13. A method for operating a parallel hybrid drive having an epicyclic gear in a direct drive mode, comprising the steps of: Driving a first shaft of the epicyclic gear with an electric machine; Driving a second shaft of the epicyclic gear with an internal combustion engine; and Transmission of movements of the first shaft and the second shaft to a third shaft of the epicyclic gear, wherein at least two shafts of the epicyclic gear are fixedly connected to one another by means of a closed clutch element.

14. A method for operating a parallel hybrid drive having an epicyclic gear in an all-electric mode, comprising the steps of: Driving a first shaft of the epicyclic gear with an electric machine; Preventing backwards rotation of an internal combustion engine connected to a second shaft of the epicyclic gear by means of a first brake element; and Transmission of a movement of the first shaft to a third shaft of the epicyclic gear.

15. A method for operating a parallel hybrid drive having an epicyclic gear in a CVT mode, comprising the steps of: Driving a first shaft of the epicyclic gear with an electric machine; Driving a second shaft of the epicyclic gear with an internal combustion engine; and Transmission of movements of the first shaft and the second shaft to a third shaft of the epicyclic gear, wherein all shafts of the epicyclic gear are rotatable relative to each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Preferred embodiments are explained in more detail with reference to the following figures. Here shows

[0056] FIG. 1 is an example of a parallel hybrid drive for a motor vehicle according to the invention;

[0057] FIG. 2 is an example of a method according to the invention for operating the parallel hybrid drive in a direct drive mode;

[0058] FIG. 3 is an example of a method according to the invention for operating the parallel hybrid drive in an all-electric mode; and

[0059] FIG. 4 is an example of a method according to the invention for operating the parallel hybrid drive in a CVT mode.

DETAILED DESCRIPTION OF THE INVENTION

[0060] The parallel hybrid drive 1 shown in FIG. 1 is part of a motor scooter (not shown) and configured to drive a rear wheel of the motor scooter. For this purpose, the hybrid drive 1 comprises an electric machine 2 and an internal combustion engine 3. The electric machine is an electric motor 2, which can also be operated as a generator. The internal combustion engine is a four-stroke reciprocating engine 3.

[0061] Furthermore, the hybrid drive 1 comprises a traction battery 12, which is configured to supply the electric motor 2 with electrical energy and to be charged by the latter.

[0062] The electric motor 2 and the internal combustion engine 3 are connected to each other by an epicyclic gear 5. The epicyclic gear 5 comprises a first shaft 6, which is configured as a ring gear shaft, a second shaft 7, which is configured as a sun gear shaft, and a third shaft 8, which is configured as a carrier shaft. In the exemplary embodiment, the first shaft 6 is connected to the electric motor 2 and the second shaft 7 is connected to the internal combustion engine 3. The third shaft 8 of the epicyclic gear 5 is connected to a drive axle 4 of the motor scooter via a chain 11. In other embodiments, the third shaft 8 can also be connected to the drive axle 4 directly or by means of a spur drive.

[0063] Furthermore, the hybrid drive 1 comprises a clutch element 9. In the exemplary embodiment, the clutch element is configured as a centrifugal clutch 9, which is opened at speeds of the motor scooter below 30 km/h. When the centrifugal clutch 9 is open, a rotational speed of the internal combustion engine 3 can be controlled by the electric motor 2 by means of the connection between the two motors 2, 3 via the epicyclic gear 5. The rotational speed of the combustion engine 3 can thus be varied continuously in a lower speed range of the motor scooter.

[0064] Furthermore, the hybrid drive 1 comprises a throttle valve control (not shown), which is configured to set a torque of the internal combustion engine 3 at a speed specified by the electric motor 2. The throttle valve control used in the exemplary embodiment enables purely mechanical load control of the internal combustion engine 3 without electronic components.

[0065] At scooter speeds above 30 km/h, the centrifugal clutch 9 is closed and firmly connects the first shaft 6 and the third shaft 8. When the centrifugal clutch 9 is closed, all shafts 6, 7, 8 of the epicyclic gear 5 rotate at the same speed. This enables motor support of the internal combustion engine 3 by the electric motor 2. The fixed connection between the shafts enables direct drive without conversion losses in the epicyclic gear.

[0066] Furthermore, the hybrid drive 1 comprises a first brake element 10. In the exemplary embodiment, the first brake element is a roller freewheel 10, which is arranged between the internal combustion engine 3 and the second shaft 7. The freewheel 10 is configured to prevent backwards rotation of the internal combustion engine 3. As a result, a torque for driving the scooter can be controlled by the electric motor 2 and, when the centrifugal clutch 9 is open, can be transmitted to the drive axle 4 independently of the internal combustion engine 3. This enables purely electric operation of the scooter.

[0067] Furthermore, the hybrid drive 1 comprises a second brake element 13, which is configured to brake the drive axle 4. In the exemplary embodiment, the second brake element is a wheel brake 13. By operating the internal combustion engine 3 and simultaneously blocking the drive axle 4 by means of the wheel brake 13, a mechanical energy is transmitted from the internal combustion engine 3 to the electric motor 2 via the epicyclic gear 5. The electric motor 2 converts the mechanical energy into an electric energy in a working machine operation. This allows the traction battery 12 to be charged in a stationary manner independent of external power sources. Furthermore, this arrangement enables the internal combustion engine 3 to be started from a standstill by means of the electric motor 2. To start the internal combustion engine 3 from a standstill, the torque required for starting is provided by the electric motor 2 and supported at the wheel brake 13.

[0068] Different operating modes of the parallel hybrid drive are explained below.

[0069] An embodiment of a method according to the invention for operating the parallel hybrid drive 1 in a direct drive mode is shown in FIG. 2. In this mode, the centrifugal clutch 9 is closed. All shafts of the epicyclic gear are fixed to each other. In a first step of the method A1, the first shaft 6 of the epicyclic gearbox 5 is driven by the electric motor 2. In a second step A2, the second shaft 7 of the epicyclic gear 5 is driven by the internal combustion engine 3. In a third step A3, the movements of the first shaft 6 and the second shaft 7 are transmitted to the third shaft 8 of the epicyclic gear 5. This causes the torques of the motors 2, 3 to be added, resulting in high wheel torques. Since all wheels of the epicyclic gear 5 are firmly connected to each other by the closed centrifugal clutch 9, no significant conversion losses occur in the epicyclic gear 5. Compared to conventional drives with friction-loss gears, the parallel hybrid drive 1 in direct-drive mode exhibits higher overall efficiency. As a result, fuel can be saved during vehicle operation. Steps A1 to A3 are carried out simultaneously in the method described.

[0070] Furthermore, the parallel hybrid drive 1 can be operated in an all-electric mode using a method according to the invention. An embodiment of the method is shown in FIG. 3. In this mode, the centrifugal clutch 9 is open. In a first step of the method B1, the first shaft 6 of the epicyclic gear 5 is driven by the electric motor 2. In a second step B2, a backwards rotation of the internal combustion engine 3 is prevented by means of the freewheel 10. In a third step of the method B3, a movement of the first shaft 6 is transmitted to a third shaft 8 of the epicyclic gear 5. In the exemplary embodiment, this results in a purely electric drive of the rear wheel of the motor scooter. Steps B1 to B3 are carried out simultaneously in the method described.

[0071] Furthermore, the parallel hybrid drive 1 can be operated in a CVT mode using a method according to the invention. An exemplary embodiment of the method is shown in FIG. 4. In this mode, the centrifugal clutch 9 is open. All wheels of the epicyclic gear 5 are rotatable against each other. In a first step of the method C1, the first shaft 6 of the epicyclic gear 5 is driven by the electric motor 2. In a second step C2, a second shaft 7 of the epicyclic gear 5 is driven by an internal combustion engine 3. In a third step C3, movements of the first shaft 6 and the second shaft 7 are transmitted to a third shaft 8 of the epicyclic gear 5. Steps C1 to C3 are carried out simultaneously in the method described. The rotational speed of the internal combustion engine 3 can be adjusted in the method by controlling the rotational speed of the electric motor 2. This enables stepless operation in which the power drawn from or supplied to the battery 12 can be adapted to its state of charge. The use of starting elements, such as friction clutches or converters, can be dispensed with. This reduces losses during start-up processes compared with conventional drives with start-up elements.