TECHNICAL FIELD

The present disclosure relates to a housing for an electric drive unit. Aspects of the invention relate to an electric drive unit and to a vehicle.

BACKGROUND

It is known to provide an Electric Drive Unit (EDU) to provide motive power to move an Electric Vehicle (EV) forwards and backwards. The EDU also provides regenerative braking when required. The EDU comprises a housing and one or more electric machines which may be used as motors or generators. The change of use for the electric machines between motor and generator is controlled by an Electric Power Inverter Converter (EPIC). The EPIC is controlled by an Electronic Control Unit (ECU).

A known EDU has an electric motor, an open differential and a planetary gear set which provides the reduction ratio from the electric motor to the outputs. The EDU outputs are connected through side shafts to the wheels. This enables the EDU to both provide motive power and regenerative braking to the wheels. An alternative EDU may have two motors to allow it to provide different torque to each wheel. Conventionally the EDU output axes are concentric and parallel and the side shafts have inboard and outboard Constant Velocity (CV) joints to allow for misalignment between the wheel hub axes and the EDU output axes. The CV joints also allow for movement of the vehicle suspension.

The EDU is supplied High Voltage (HV) 3-phase Alternating Current (AC) electrical power from the EPIC which draws Direct Current (DC) from a traction battery in the vehicle. Sensors in the EDU allow the EPIC to phase the AC supply to provide motive torque from the motor. When regenerative braking, the EDU generates HV 3-phase AC which the rear EPIC rectifies to Direct Current (DC) to charge the EV battery.

Figure 1 shows an example of a known EDU with a housing containing two motors and concentric output axes. There are shown a left motor housing 2 and a right motor housing 12 with respective rotational axes 22 and 32. The left motor (housed within the housing 2) drives a reduction gearbox within housing 4 which is concentric with the motor. The right motor (housed within the housing 12) drives a second reduction gearbox within housing 14. Output from the left and right gearboxes pass through inboard CV joints 6 and 16 respectively into side shafts, the left 8 and right 18 side shafts are symmetric. Drive is passed from the side shafts to the outboard CV joints, again the left 9 and right 19 outboard CV joints are symmetric and the stub shafts attached to the CV joints provide drive to the wheels in a conventional manner (not shown). The motor and gearbox housings (2, 4, 12, 14) are housed within a housing which may consist of several parts. Left and right motors have axes 22 and 32 respectively which are coaxial. The left side shaft 8 has a rotational axis 28 and the left outboard CV joint has a rotational axis 29. The left inboard CV joint angle is the angle between the left motor axis 22 and the left side shaft axis 28. The left outboard CV joint angle is the angle between the left side shaft axis 28 and the left outboard CV joint axis 29. The right joint angles are symmetric with the left.

Enlarging the diameter of the electric motor can improve drive and regeneration efficiency by reducing the ratio of or need for reduction gearing. Installing a larger motor while maintaining ground clearance conventionally increases the angle of the CV joints and reduces their efficiency and durability.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a housing for an electric drive unit, an electric drive unit and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a housing for an electric drive unit in a vehicle comprising a first cylindrical portion having a first axis for housing a first electric motor and a second cylindrical portion having a second axis for housing a second electric motor. The first axis is configured such that it is not parallel to the second axis.

When this housing is used in an electric drive unit in a vehicle the angle of the axes slope downward toward the wheels. This reduces the running angle of the inboard CV joint (i.e. the angle between the EDU output and the corresponding side shaft) compared with the prior art and so improves the efficiency of this joint, both when the EDU is driving the wheels and when the EDU is providing an overrun torque, for example to charge the battery. Advantageously there is also a reduction in the running angle of the outboard joint (i.e. the angle between the side shaft and the corresponding stub shaft) as the location of the inboard joint may be lower than the prior art allows, while this is a small improvement it also improves the efficiency of the outboard joint. Optionally an angle between the first axis and the second axis is obtuse. The angle between the first axis and the second axis may be between 175 degrees and 120 degrees. The first axis may be offset from the second axis.

According to another aspect of the present invention there is provided an electric drive unit comprising the housing of any preceding aspect at least partially enclosing a first electric motor and a second electric motor. A rotational axis of the first motor is parallel with the first axis of the housing and a rotational axis of the second motor is parallel with the second axis of the housing.

Optionally the electric drive unit has a first output with an axis parallel to the first axis of the housing. The electric drive unit also has a second output with an axis parallel to the second axis of the housing. The first output axis may be coaxial with the first axis of the housing and the second output axis may be coaxial with the second axis of the housing.

According to a further aspect of the present invention there is provided a vehicle comprising the electric drive unit of the above aspect and the first electric motor provides drive to a first road wheel and the second electric motor provides drive to a second road wheel.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic diagram of an EDU illustrating an example of prior art;

Figure 2 shows a schematic diagram of an EDU illustrating an embodiment of the invention; Figure 3 shows a diagram of an EDU illustrating an embodiment of the invention;

Figure 4 shows a torque efficiency vs. joint angle graph for a Rzeppa CV joint;

Figure 5 shows a vehicle in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

An electric drive unit housing, for use in a vehicle in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures.

With reference to Figure 2, there is shown a representation of an EDU with two motors and concentric output axes. There are shown a left motor housing 42 and a right motor housing 52 containing left and right motors with respective rotational axes 62 and 72. The axis of the left motor housing 42 is coaxial with the axis of the left motor and the axis of the right motor housing 57 is coaxial with the right motor. The left motor drives a reduction gearbox which is concentric with the motor. The left reduction gearbox is housed within a housing 44 which may be integrated with the left motor housing. The right motor drives a second reduction gearbox within housing 54 and is arranged symmetrically with the left motor and left reduction gearbox. Output from the left and right gearboxes pass through inboard CV joints 46 and 56 respectively into left 48 and right 58 side shafts. Drive is passed from the side shafts to the left 49 and right 59 outboard CV joints which have stub shafts to pass drive to the wheels (not shown) in a conventional manner. The left motor housing and the left reduction gearbox housing 44 are located next to each other and together form a left housing. Similarly the right motor housing and the right reduction gearbox housing together form a right housing.

Left and right motors have axes 62 and 72 respectively which are angled relative to one another. The angle between the motor axes is obtuse and may be between 175 degrees and 120 degrees although other angles are possible within the scope of the invention. In the illustrated example the left and right motors are angled in a downward direction towards the stub shafts such that the base of the left and right motors and their respective housings 42, 52 are closer together than the top of the left and right motors and their respective housings 42, 52. The left side shaft 48 has a rotational axis concentric with the motor axis 62 and the left outboard CV joint has a rotational axis 69. The left inboard CV joint angle is the angle between the left motor axis 62 and the left side shaft axis and is shown as zero (concentric) in this embodiment. It is envisaged that a small inboard CV joint angle may be provided as it may benefit CV joint durability. This small inboard CV joint angle may be in a range up to 5 degrees. The left outboard CV joint angle is the angle between the left side shaft axis and the left outboard CV joint axis 69. The right joint angles are symmetric with the left in this embodiment although the invention is not restricted to a symmetric embodiment. An example of a non- symmetric housing may have the EDU mounted away from the centreline of the vehicle with different length side shafts. In this alternative embodiment the inboard joint angles would be small and the housing angled to approach the side shaft angles. The embodiment shown has a reduction gearbox which is concentric with the motor but a spur reduction gearbox with parallel but offset input and output axes also falls within the scope of the invention.

Figure 3 shows a CAD image of housings 42, 52 with side shafts 48, 58 and CV joints 46, 49, 56, 59 in accordance with an embodiment of the invention. Numbering of figure 3 follows the numbering of figure 2. Figure 3 shows a view of the EDU viewed from the rear of the vehicle and it may be seen that the housing is angled both in the vertical direction and also slightly in a rearward direction. This combined angle is within the scope of the invention and may be used to provide packaging benefits and additionally to avoid the inboard joints running at a zero angle. Not shown in Figure 3 is an offset where one motor axis is forward of the other motor axis in addition to the axes being angled relative to one another. This may provide further packaging benefits in the vehicle. Allowing the motor axes to approach concentricity with the side shaft axes may allow this offset configuration without exceeding durable joint angle limits.

Figure 4 shows an example of the efficiency of a Rzeppa CV joint at different running angles. The torque loss rate describes the torque loss as a percentage of the torque transmitted by the joint, a lower torque loss rate equating with improved efficiency. For example, reducing the running angle of the joint from 10 degrees to 4 degrees reduces the torque loss rate from 1% to 0.4%.

Figure 5 shows a vehicle 100 in which the EDU of the invention may be mounted, driving the front or the rear wheels. It is also envisaged that a first EDU may drive the front wheels and a second EDU may drive the rear wheels, the first and/or the second EDU may be configured with a housing of the invention. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.