WO2020068048A1

WO2020068048A1 - Electric motor chain drive system for hybrid electric vehicles and plug-in hybrid electric vehicles

Info

Publication number: WO2020068048A1
Application number: PCT/US2018/052599
Authority: WO
Inventors: Song Jun; Meng ZAIQIANG; Lu XIAOJIAN
Original assignee: Borgwarner Inc
Priority date: 2018-09-25
Filing date: 2018-09-25
Publication date: 2020-04-02

Abstract

A chain drive system is used in the hybrid propulsion system of a Hybrid Electric Vehicle (HEV), which could be a plug-in HEV, to couple an electric motor to the driving wheels of the vehicle. In an alternate embodiment, the chain drive system can be installed to transfer torque from the engine or vehicle wheels to the electric motor to generate power for the vehicle battery.

Description

ELECTRIC MOTOR CHAIN DRIVE SYSTEM FOR HYBRID ELECTRIC VEHICLES AND PLUG-IN HYBRID ELECTRIC VEHICLES

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention pertains to the field of chain drive systems. More particularly, the invention pertains to a chain drive system for use with hybrid electric vehicles (HEV), including plug-in hybrid electric vehicles (PHEV).

DESCRIPTION OF RELATED ART

A Hybrid Electric Vehicle (HEV) is a vehicle which is propelled by one or more electric motors and also by an internal combustion engine (ICE). All hybrid vehicles include a battery to provide electrical energy to the electric motor. The vehicle can use the energy to drive the electric motor to supplement the power of the ICE during periods of acceleration or higher power demand, and many hybrids can also use the electric motor to replace the ICE for short periods of time in start-stop operation. Many hybrids will also be able to recover energy which would normally be wasted during braking by using the electric motor as a generator to store energy back in the battery, a process called “regenerative braking”. Thus, a hybrid vehicle can improve both the performance and the economy of a vehicle compared to a vehicle powered only by an internal combustion engine.

A Plug-In Hybrid Electric Vehicle (PHEV) goes one step further, by having enough battery capacity to operate the vehicle for extended periods using electrical power alone, and the ability to charge the battery from external sources when the vehicle is not being driven. For a PHEV, the internal combustion engine will be started to power the vehicle only when the battery power is exhausted. It should be noted that some vehicles which are termed“plug-in hybrids” are really fully electrically powered vehicles, normally operated on batteries which are charged from an external source, which have an on-board ICE which powers a generator to recharge the battery. In the context of this application, however, the term“PHEV” is used to mean a vehicle which has enough battery capacity to operate without the ICE for a significant period, but also can couple the output of the ICE to the wheels to propel the car.

It will be understood that in order for an HEV or PHEV to function, it is necessary to couple the output of both the electric motor and the ICE to the driven wheels of the vehicle. For HEVs which just use the electric motor for supplemental power (and regenerative braking, if so equipped), the electric motor and internal combustion engine can be connected together at all times. If the HEV or PHEV is to be able to operate for any period of time on purely electrical propulsion, it is also necessary to disconnect the ICE from the drive line to remove the drag from the engine when it is not operating. These differing needs have led to a variety of arrangements for accommodating the two types of motors.

An internal combustion engine has an output, which is usually formed by one end of a crankshaft. The opposite end of the crankshaft usually has a gear, pulley, or sprocket for driving auxiliary equipment such as an alternator, power steering pump, fuel pump, water pump, air conditioning compressor, and other such loads. It will be understood by one skilled in the art that some internal combustion engines such as Wankel rotary engines or turbines do not have crankshafts, as such, in which case the output of the internal combustion engine would be a rotor shaft or turbine shaft.

A transmission has an input coupled to the output of the internal combustion engine and an output which is coupled to the driving wheels by one or more differentials. The transmission provides a plurality of speed ratios between the input and output, so that the ICE can operate as much as possible within an efficient range of rotational speeds. Because internal combustion engines must continue to operate while they are running, a clutch or torque convertor or fluid coupler is needed between the output of the engine and the input of the transmission to disconnect the engine from the transmission while it is idling or its output is not needed. In contrast, electric motors are capable of starting from rest or coasting without using energy, so no clutch or other coupling is necessarily required between the electric motor and the drivetrain.

The differential or differentials couple the driving power from the transmission to the wheels. Differentials are needed to permit each wheel to operate at a different rotational speed from the wheel on the opposite side of the vehicle, so that the vehicle can drive around comers where the outside wheel describes a longer path than the inside wheel. In the case of vehicles which have more than one pair of driven wheels, the inputs of the differentials on each pair of wheels must be coupled to the output of the transmission by some form of differential (AWD) 167 or transfer case (4WD).

Figure 2 is a diagram of a vehicle, with the alternative configurations for the electric motor denoted by (P0)-(P3). Each configuration provides different advantages and disadvantages and associated hybrid functionality depending on the location (P0)-(P3) where the electric motor is coupled into the drive system for the vehicle.

In the P0 configuration, the output of the electric motor is coupled to the opposite end of the crankshaft from the transmission input shaft, which usually drives a pulley 181 or gear. This would most often mean that the electric motor would be incorporated into the auxiliary drive system by a pulley running on the serpentine belt 178 driving the other loads 179, or by a gear meshing with a crankshaft gear. In some HEVs this is done by using a motor/generator in place of the alternator which would be used in a pure ICE application.

A Pl configuration places an electric motor on the output of the internal combustion engine, such as rear end of the crankshaft. This arrangement can be implemented by coupling an integrated starter/generator to the flywheel through a belt or gear drive.

In either P0 or Pl configuration, no purely electric driving is possible because the electric motor is directly connected to the internal combustion engine’s crankshaft. Start- stop functionality is possible, however, which stops the ICE when the car stops, and then restarts the ICE when the electric motor begins to move the vehicle.

A P2 configuration places an electric motor on the transmission input shaft between the transmission and the clutch, torque convertor or coupling which connects the internal combustion engine to the transmission. In this configuration, the electric motor can be mechanically disconnected from the internal combustion engine by the clutch, torque convertor or coupling, so that the electric motor can provide power to the transmission while the internal combustion engine is not turning. Thus, the vehicle can be powered purely by the electric motor, as well as permitting a start-stop functionality.

In a P3 configuration, an electric motor is placed on the transmission output, between the transmission output and the input to the differential(s). For a rear- wheel drive car, for example, this can be done by coupling the electric motor to the drive shaft by a belt or gears. This configuration allows the electric motor to be disconnected from the internal combustion engine either using the clutch or torque converter or coupling, as in the P2 configuration, and also by putting the transmission in neutral, disconnecting the transmission input from the transmission output. As with the P2 configuration, in this arrangement pure electric driving can be enabled.

SUMMARY OF THE INVENTION

In one embodiment, a hybrid electric vehicle is disclosed. The hybrid electric vehicle comprises an internal combustion engine, a transmission, at least one differential for transferring power from an input to a pair of wheels, an electric motor and a chain drive system.

The transmission has an input coupled to the output of the internal combustion engine through a clutch or a coupling such as a torque convertor or fluid coupling, and an output. The input of the at least one differential is coupled to the output of the transmission, and the differential transfers the power from the input to each of the wheels in the pair of wheels, while allowing the wheels to rotate at different speeds. The vehicle could optionally have additional differentials powering additional pairs of wheels, in which case the input of each of the additional differentials would be coupled to the input of the at least one differential in a conventional form, for example by a transfer case or fluid coupling or other means known to the art.

The electric motor has an electrical input and a mechanical output. When the electric motor is operated in motor mode, electrical energy at the electrical input creates mechanical power at the mechanical output. It will be understood by those skilled in the art that when the electric motor is used in a generator mode, rotational energy applied to the mechanical output generates electrical energy at the electrical input, but for simplicity of explanation the terms“input” and“output” will be used herein.

The chain drive system allows mechanical power from the output of the electric motor to be coupled to the wheels of the vehicle either in addition to the power output of the internal combustion engine, or in place of the power output of the internal combustion engine. In addition, when the electric motor is in generator mode, the chain drive system transfers power from the rotation of the wheels to the output of the electric motor, which can then generate electric energy for storage in a battery or to be dissipated for regenerative braking.

The chain drive comprises a first sprocket coupled to the output of the electric motor, a second sprocket, an endless loop toothed chain wrapped around the first and second sprockets. At least one snubber, guide or tensioner can be provided for guiding and tensioning the chain span between the first sprocket and the second sprocket. The second sprocket couples the chain drive to the vehicle drive components in one of a number of optional configurations.

BRIEF DESCRIPTION OF THE DRAWING Fig. 1 shows a chain drive system.

Fig. 2 shows a diagram of a hybrid electric vehicle of the prior art.

Fig. 3 shows a diagram of a hybrid electric vehicle using the chain drive system.

Fig. 4a shows a partial side view of a toothed chain.

Fig. 4b shows a top view of the toothed chain of Fig. 4a.

Fig. 5 shows the chain drive system of Figure 1 without the base.

Fig. 6 shows a sectional view along line 6-6 of Fig. 5.

Fig. 7 shows the first sprocket of the chain drive system.

Fig. 8 shows the second sprocket of the chain drive system. Fig. 9a shows a side view of a first chain snubber of the present invention.

Fig. 9b shows an isometric view of the first chain snubber of the present invention.

Fig. 9c shows a view of the guide surface of the first chain snubber of the present

invention.

Fig 9d shows a sectional view of the bushing along line 9-9 of Figure 9b.

DETAILED DESCRIPTION OF THE INVENTION

In an embodiment of the present invention, a chain drive system is used in the hybrid propulsion system of a Hybrid Electric Vehicle (HEV), which could be a plug-in HEV, to couple an electric motor to the driving wheels of the vehicle. In an alternate embodiment, the chain drive system can be installed to transfer torque from the engine or vehicle wheels to the electric motor to generate power for the vehicle battery.

Referring to Figures 1, 5, 7 and 8, the chain drive system 102 has a first sprocket 106 with a plurality of teeth l06a mounted on a shaft 114 for coupling to the electric motor, and a second sprocket 108 with a plurality of teeth l08a mounted on a shaft 116. The first sprocket 106 can have a different number of teeth than the second sprocket 108 to provide a speed reduction and/or torque conversion function. The first sprocket 106 is connected to the second sprocket 108 via an endless loop toothed chain 118.

The toothed chain 118 transfers output torque of the electric motor via the shaft 114 to the first sprocket 106, to the sprocket teeth l08a of the second sprocket 108, which is mounted on a shaft 116. The transfer of torque from the electric motor to other parts of the vehicle drive train through the second sprocket 108 enables the electric motor to add power to the drive train for supplemental power or to operate the vehicle in electric mode, and also allows the electric motor receive power from the drive train for regenerative braking.

Referring to Figures 9a-9d, a first chain snubber 110 is secured to a base 104 adjacent a first strand H8a of the chain 118, for example using fasteners 120. Optionally, a second chain snubber 112 is secured, to the base 104 adjacent a second strand H8b of the chain 118, for example using fasteners 120. The first and second chain snubbers 110, 112 each include a guide surface l lOa,

1 l2a which contacts the chain span 1 l8a, 1 l8b to control transverse movement of the chain 118 and limit chain oscillation or vibrations. Alternatively, the first and second chain snubbers 110, 112 can be secured to a plate (not shown) which is secured to the base 104. The guide surfaces 1 lOa, 1 l2a can be an elastomer material or can be an elastomer bonded to a reinforcing material such as aluminum, steel, or nylon. In a preferred embodiment, the first and chain snubbers 110, 112 are attached to the base 104 using bolts 120 which are received in bushings l22a, l22b, l22c which can be formed within the body llOb, H2b of the first and second chain snubbers 110, 112. A washer 123 may be present for use between the bolt 120 and the bushing l22a, l22b, l22c. Using the bushings l22a, l22b, l22c formed within the body l lOb, H2b of the snubber 110, 112 increases flexibility for clearance control. In one embodiment, three bushings l22a, l22b, l22c are preferably present.

In another embodiment, the first and second chain snubbers 110, 112 can be replaced with mechanically or hydraulically actuated tensioner arms.

The toothed chain 118 is shown in Figures 4a and 4b. In one embodiment, the toothed chain 118 has two inside links 131, 134 with different outer tooth profiles interleaved into a specific pattern. Adjacent the inside links 131, 134 are outer guide links 130. The links 130, 131, 134 are all arranged on a rocker pins 133 and straight pins 132. The links 131, 134 engage the sprocket teeth l06a, l08a of the first sprocket 106 and the second sprocket 108.

In another embodiment, the pattern of the links can be random to reduce noise, vibration and harshness.

The number of teeth as well as the profile of the teeth of the first and second sprockets 114, 116 are preferably optimized for interaction with the toothed chain 118. Additionally, the tooth profile of the toothed chain 118 can also be optimized for meshing with the sprockets 114, 116 to reduce noise, vibration and harshness (NVH).

Figure 3 shows different configurations of coupling the electric motor to the vehicle drivetrain using the chain drive 102. While all of the electric motor configurations P0-P3 are shown in the Figure, it should be noted that in any given vehicle, it is likely that only one electric motor would be present. Furthermore, while not shown, it will be understood that the electric motor will be connected to one or more batteries and a controller, which do not form part of the invention.

Referring to Figure 3, in one embodiment, the chain drive system 102 can be present in a P0 configuration in which the chain drive system 102 is coupled to the crankshaft pulley 180 at the front end of the internal combustion engine 176. In this case, the shaft 114 of the first sprocket 106 would be an output shaft 181 of the electric motor P0 and the shaft 116 of the second sprocket 108 would be the crankshaft 180 of the internal combustion engine 176.

In an alternate embodiment, the chain drive system 102 is present in a Pl configuration in which the chain drive system 102 is placed between an electric motor Pl on the crankshaft 182 or output of the internal combustion engine 176, and an input of the clutch 174. In this case, the shaft 114 of the first sprocket 106 would be an output shaft of the electric motor Pl and the shaft 116 of the second sprocket 108 would be the output shaft 182 of the engine, ahead of the clutch 174.

In another embodiment, the chain drive system 102 is present in a P2 configuration in which the chain drive system 102 is placed between an electric motor P2 on the input shaft 183 of the transmission 172, on the other side of clutch 174 from the Pl

configuration. In this case, the shaft 114 of the first sprocket 106 would be an output shaft of the electric motor P2 and the shaft 116 of the second sprocket 108 would be the input shaft 183 of the transmission 172.

In another embodiment, the chain drive system 102 is present in a P3 configuration in which the chain drive system 102 is placed between an electric motor P3 on the output shaft 184 of the transmission 172 and input to the differential 166. In figure 3 this differential 166 is shown as being between the front wheels 152 and 154. The differential 166 is connected to the first front wheel 152 through a first axle 168 and the second front wheel 154 is connected to the differential 166 through a second axle 170. The shaft 114 of the first sprocket 106 would be an output shaft of the electric motor P3 and the shaft 116 of the second sprocket 108 would be the input shaft 184 to the differential 166. If there is another differential in the vehicle, as for example rear differential 160 driving rear wheels 156 and 158 by axles 162 and 164, it would be connected to the output of the transmission 172 by transfer case or center differential 167 as is known to the art.

By using a chain drive system 102 including a toothed chain 118 and chain snubbers 110, 112, the chain drive system 102 increases the efficiency of the HEVs and PHEVs, decreases NVH, has lighter mass, and better drivability by speed reduction, compared with a traditional gear drive.

Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.

Claims

What is claimed is:

1. A drive system for hybrid electric vehicles, comprising: a drivetrain comprising: an internal combustion engine having an output; a transmission having an input coupled to the output of the internal combustion engine and an output; and at least one differential having an input coupled to the output of the transmission, and a pair of outputs for coupling to a pair of wheels; an electric motor having an electrical input and a mechanical output; and a chain drive system coupling the electric motor to the drivetrain, comprising: a first shaft coupled to the mechanical output of the electric motor; a first sprocket mounted to the first shaft; a second sprocket for mounting to a second shaft coupled to the drivetrain; an endless loop toothed chain connecting the first sprocket to the second

sprocket; and at least one guide guiding the first chain span or the second chain span between the first sprocket and the second sprocket.

2. The drive system of claim 1, in which the second shaft is a crankshaft of the internal combustion engine.

3. The drive system of claim 1, in which the second shaft is the output of the internal combustion engine.

4. The drive system of claim 1, in which the second shaft is the input of the transmission.

5. The drive system of claim 1, in which the second shaft is the output of the transmission.

6. The drive system of claim 1 , wherein the first sprocket has a different number of teeth than the second sprocket.

7. The drive system of claim 1, wherein the chain drive system further comprises a second guide guiding the other of the first chain span of the second chain span between the first sprocket and the second sprocket, opposite the first guide.

8. The drive system of claim 7, wherein the guide is a snubber.

9. The drive system of claim 7, wherein the guide is a tensioner.

10. The drive system of claim 1, wherein the guide is a snubber.

11. The drive system of claim 1, wherein the guide is a tensioner.