EP3867115A1

EP3867115A1 - A hybrid drive module, and a method for improving performance of such hybrid drive module

Info

Publication number: EP3867115A1
Application number: EP19797187.2A
Authority: EP
Inventors: Tim Olsson; Hans AULIN
Original assignee: BorgWarner Sweden AB
Current assignee: BorgWarner Sweden AB
Priority date: 2018-10-18
Filing date: 2019-10-18
Publication date: 2021-08-25
Also published as: WO2020079265A1

Abstract

A method for reducing acceleration variations of an output shaft (102) of a hybrid drive module (100), said hybrid drive module (100) comprising an electrical motor (110) being connected to the output shaft (102), wherein a crankshaft (22) of an associated internal combustion engine (20) is connected to an input shaft (101) of the hybrid drive module, and wherein the input shaft (101) is connected to the output shaft (102) via a dual mass flywheel (140) and a first clutch (130), said method comprising the steps of: - determining (202) the actual acceleration of the output shaft (102), - determining (204) the torque required to at least to some extent reduce said actual acceleration, and - applying (206) said determined torque to said output shaft (102) by activating the electrical motor (110).

Description

A HYBRID DRIVE MODULE, AND A METHOD FOR IMPROVING

PERFORMANCE OF SUCH HYBRID DRIVE MODULE

Technical Field

The present invention relates to a hybrid drive module and aspects of methods for improving operating performance of such hybrid drive module, in particular for reducing angular acceleration of mass. It also relates to a vehicle comprising a hybrid drive module. Background

Vibrations and noise are common problems in combustion engine-based vehicles due to the crankshaft being accelerated during combustion in the cylinder. This may result in large alternating torque pulsations during rotation of the crankshaft. The torque pulsations can be dampened in various ways, e.g. by extending the piston rod, by providing a large flywheel or by increasing the number of cylinders to provide a more continuous torque on the crankshaft. In addition, mass forces arise due to the internal masses being accelerated back and forth causing oscillating forces; these can typically be balanced by means of increasing the cylinder count.

In modern hybrid drive trains, it is common to use combustion engines with fewer cylinders. Hybrid systems are therefore susceptible to issues with vibrations.

One way of dealing with such issues is using more and more complex and expensive vibration dampeners, such as dual mass flywheels and centrifugal pendulum absorbers. These are not only costly, but also space consuming as well as heavy so it is desired to find a way to reduce the need for such components or at least allow use of smaller, less complex mechanical vibration dampeners.

As hybrid powertrains for passenger cars are gaining interest, so does the number of solutions for such applications that are being proposed. One such proposal is to provide the hybrid functionality as a separate module, which is added to the existing powertrain. An example of an existing hybrid drive module includes a first sprocket which is intended to be connected to the crankshaft of the internal combustion engine indirectly via a dual mass flywheel and a disconnect clutch, and an electrical motor being drivingly connected to a second sprocket. The sprockets are connected by means of a belt or chain in order to allow for various driving modes such as pure electrical driving, recuperation, traction mode, and boost. The electric motor may also in other examples be arranged directly on a shaft in the powertrain, with the rotor of the electric motor being fixedly connected and providing power directly to the shaft without having to use any belt or chain.

In the prior art hybrid module there is limited means for reducing the vibrations of the associated internal combustion engine due to the shortage of space in these types of applications. As such, there exists a need for a method of reducing the acceleration variations.

Summary

It is thus an object of the teachings herein to provide an improved hybrid drive module overcoming the disadvantages of prior art solutions.

An idea of the present invention is to provide a hybrid drive module, as well as a method for such hybrid drive module, utilizing an active dampening by means of an electrical motor of the hybrid drive module.

According to a first aspect, a method for reducing acceleration variations of an output shaft of a hybrid drive module is provided. The hybrid drive module comprises an electrical motor being connected to the output shaft, and a crankshaft of an associated internal combustion engine is connected to an input shaft of the hybrid drive module. The input shaft is connected to the output shaft via a dual mass flywheel and a first clutch. The method comprises determining the actual acceleration of the output shaft, determining the torque required to at least to some extent reduce said actual acceleration, and applying the determined torque to the output shaft by activating the electrical motor. The method thus reduces the vibrations produced by the internal combustion engine in an active, adaptive manner, providing an improved driveline.

Preferably, the method also comprises providing a real-time model of at least parts of the hybrid drive module, and/or the associated internal combustion engine. Having the real-time model at hand, it can run in parallel with operation of the hybrid drive module. The model may preferably be associated with a state observer which is capable of determining an estimate of one or more model states, in particular the torque acting on the output shaft, from measured values of rpm on the input shaft and on the output shaft. From an estimated value of the torque acting on the output shaft, it is possible to more accurately determine the torque required to at least to some extent reduce said actual acceleration.

In one embodiment, one or more of the steps are performed continuously whereby the actual acceleration of the output shaft is reduced. In one embodiment, determining the actual acceleration of the output shaft is performed by determining the actual acceleration of an output shaft of a gearbox arranged downstream the hybrid drive module, and estimating the actual acceleration of the output shaft of the hybrid drive module.

Determining the actual acceleration of the output shaft may be performed by determining the actual acceleration of a rotating shaft of the hybrid drive module. The rotating shaft being selected from the group comprising: an input shaft, a primary mass of the dual mass flywheel, a first secondary mass component of the dual mass flywheel, and a second secondary mass component of the dual mass flywheel.

In one embodiment, the electrical motor is coupled to a gearbox via a second clutch and the step of determining the actual acceleration of the output shaft further comprises continuously determining a torque over said second clutch.

The step of determining the torque over the second clutch may further be performed by estimating the torque by means of an observer.

In a second aspect, a hybrid drive module is provided. The hybrid drive module comprises a housing enclosing an electrical motor, the electrical motor being connected with an output shaft. A crankshaft of an associated internal combustion engine is connected to an input shaft of the hybrid drive module, and the input shaft is connected to the output shaft via a dual mass flywheel and a first clutch. The hybrid drive module further comprises a control unit configured to determine the actual acceleration of the output shaft, to determine the torque required to at least to some extent reduce the actual acceleration, and to apply the determined torque to the output shaft by activating the electrical motor.

The control unit may be further configured to store and run a real-time model of at least parts of the hybrid drive module, and/or the associated internal combustion engine, as described above.

In one embodiment, the electrical motor is arranged in a coaxial manner on the output shaft downstream of the clutch.

In a further embodiment, the electrical motor is arranged in an off-axis manner in relation to the output shaft of the hybrid drive module, the electrical motor being connected via a continuous member drive to a second sprocket on the output shaft of the hybrid drive module.

In a third aspect is a vehicle provided comprising a hybrid drive module of the second aspect. Further advantages and embodiments are disclosed below and in the appended claims.

Brief Description of the Drawings

Embodiments of the teachings herein will be described in further detail in the following with reference to the accompanying drawings which illustrate non-limiting examples on how the embodiments can be reduced into practice and in which:

Fig. la shows a schematic outline of a hybrid drive module according to an embodiment;

Fig. lb shows a schematic outline of a hybrid drive module according to an embodiment;

Fig. 2a is a cross-sectional view of an exemplary dual mass flywheel according to an embodiment of the hybrid drive module shown in Fig. la;

Fig. 2b is a cross-sectional view of an exemplary dual mass flywheel according to an embodiment of the hybrid drive module shown in Fig. lb;

Fig. 3 shows three diagrams representing operation of the hybrid drive module shown in Fig. 2a; and

Fig. 4 is a schematic view of a method according to an embodiment.

Detailed description

With reference to Fig. la, a schematic outline of an engine assembly 10 of a vehicle is shown, comprising a hybrid drive module 100 according to an embodiment. The associated vehicle is typically a passenger car, and the engine assembly 10 used for propulsion of the vehicle comprises an internal combustion engine 20 and the hybrid drive module 100. As will be explained in the following the hybrid drive module 100 is mechanically connected to a crankshaft 22 of the internal combustion engine 20 in order to provide additional drive torque to a transmission 160 arranged in series with the hybrid drive module 100. Hence, the transmission 160 is also connected to the crankshaft 22 as is evident from Fig. l a.

The hybrid drive module 100 thus comprises an input shaft 101 that is connected to the crankshaft 22 of the internal combustion engine 20, and an output shaft 102 that is connected to downstream driveline components such as the transmission 160.

The hybrid drive module 100 comprises an electrical motor 110 and a continuous member drive 120, here in the form of a chain drive, connecting the electrical motor 110 with the crankshaft 22. The electrical motor 110 is for this purpose driving a first sprocket 122 of the chain drive 120, whereby upon activation of the electrical motor 110 rotational movement of the first sprocket 122 is transmitted to a second sprocket 124 of the chain drive 120 via a chain 126.

The second sprocket 124 is drivingly connected to the to the output shaft 102, which is indirectly connected to the crankshaft 22 via one or more couplings. In the embodiment shown in Fig. la, the second sprocket 124 is connected to the output shaft 102 which is connected to a disconnect clutch 130 receiving driving torque from a dual mass flywheel 140. The dual mass flywheel 140 has a primary mass 142 and a secondary mass 144, typically rotationally connected to each other via one or more springs. For serial two-clutch systems, commonly denoted hybrid P2 systems, the disconnect clutch 130 is often referred to as the K0 clutch. The dual mass flywheel 140 (which could be replaced by another torsional damping/absorption device), receives input torque directly from the crankshaft 22 via the input shaft 101.

The dual mass flywheel 140 may also be connected directly or indirectly via for instance the clutch 130 to a centrifugal pendulum absorber (CPA) 148. Also illustrated in Fig. la is a further optional clutch 150, here representing a launch clutch 150. Again referring to P2 systems, the launch clutch 150 is often referred to as the Kl clutch. The launch clutch 150 is arranged downstream, i.e. on the output side of the hybrid drive module 100 upstream a transmission 160. It should be realized that the launch clutch 150 could be replaced by a torque converter or similar.

As is also shown in Fig. la the electrical motor 110, and optionally also the clutch 130, is connected to a control unit 170 being configured to control the operation of the electrical motor 110 and optionally also the clutch 130 as will be further explained below.

The configuration shown in Fig. la is an off-axis configuration, where the electrical motor 110 is arranged in parallel but offset in relation to the longitudinal axis of the input shaft 101 and the output shaft 102 of the hybrid drive module 100, as well as in relation to the crankshaft 22 of the engine 20.

In Fig. lb however, the electrical drive module 100 is arranged in an on- axis configuration. Here, the electrical motor 110 is arranged coaxially on the output shaft 102 of the hybrid drive module 100 and is thus preferably coaxial with the input shaft 101 of the hybrid drive module 100 and the crank shaft 22 of the internal combustion engine 20 as well. With the rotor of the electrical motor 110 arranged directly connected to the output shaft 102 is the need for a continuous member drive 120 removed. Both on-axis and off-axis configurations are commonly used in hybrid drive applications, and the application at hand dictates whether on- or off-axis is the best choice. With the exception of the arrangement of the electrical motor 110, the embodiment shown in Fig. lb is identical to that of Fig. la and therefore is the detailed description of the components and features of Fig. la also applicable to Fig. lb

Fig. 2a is a cross sectional view of an exemplary dual mass flywheel (DMF) 140, to form part of the hybrid drive module 100 of Fig. la. The hybrid drive module 100 being arranged in an off-axis configuration, with the electrical motor 110 connected to the second sprocket 124. The dual mass flywheel 140 comprises the primary mass 142, which is connected to the crankshaft 22 via the input shaft 101, and the secondary mass 144, which transmits torque from the primary mass 142 further downstream. For the purpose of explaining the concepts of vibration damping herein, the secondary mass 144 is considered to also include the masses of the clutch 130, the second sprocket 124 (in

embodiments with off-axis configuration) as well as the CPA 148 (in

embodiments where a CPA is used) and the other thereto connected downstream components of the power train such as the output shaft 102.; However, the secondary mass 144 can also be divided into two separate masses l44a, l44b that are separated by the clutch 130. A first secondary mass component l44a is formed by the output 144 of the dual mass flywheel 140 and the input shaft l30a of the clutch 130 with the thereto-connected discs. A second secondary mass component l44b is formed by the output shaft l30b of the clutch 130, along with the CPA 148 (where applicable), the second sprocket 124 (where applicable) and the other downstream components of the power train.

The primary mass 142 is connected to the secondary mass 144 via a damper 146, where the damper 146 typically comprises coiled springs or like.

Fig. 2b shows a cross sectional view of the dual mass flywheel 140 in an on-axis configuration. As can be seen, the clutch output shaft l30b is now connected to the CPA 148, which is optional, and to the output shaft 102. The electrical motor 110 (not shown in Fig. 2b) is then connected directly onto the output shaft 102 via for instance a spline connection or by any other suitable connection type. The remaining features are shared with the embodiment shown in Fig. 2a and will thus not be described further in relation to Fig. 2b.

Fig. 3 shows three graphical representations of how the hybrid drive module 100, together with the engine 20, perform during operation. The first upper diagram represents actual speeds/RPMs of the primary mass 142 (i.e. the speed of the input shaft 101 and thus the thereto connected crankshaft 22) of the dual mass flywheel 140 and of the input shaft of the gearbox 160 or the thereto connected output shaft 102 from the hybrid drive module 100, as a respective function of time. The second middle diagram is an acceleration diagram depicting the acceleration of the primary mass 142 and the second secondary mass component l44b as a function of time. The third lower diagram representing torque applied by the electrical motor 110 to the second secondary mass component l44b as a function of time.

All three diagrams of Fig. 3 are aligned in time and thus showing simultaneous measurements of RPM, acceleration and torque of parts of the hybrid module 100. Thus, Fig. 3 illustrates in graphical form, some of the technical effects and advantages of the present invention as described herein.

Referring to the left hand side of the three graphs; ranging from time mark zero and up to time mark two and a half seconds, i.e. on the left side of the dashed line OP, there is no active dampening of the vibrations. This is realized by studying the lower diagram, in which the torque of the electrical motor 110 is zero.

From the upper diagram, actual RPM values of the input shaft of the gearbox 160 and the crankshaft 22 can be determined. It can be derived from the top diagram that the magnitude of speed of the crankshaft 22 shows a

characteristic oscillation throughout the whole time interval, as is expected as the crankshaft 22 is connected to the internal combustion engine. It is further derivable that also the speed of the input shaft of the gearbox 160 oscillates, however with much smaller amplitude than the crankshaft 22 and that the oscillation of the speed of the input shaft of the gearbox 160 correlate with the oscillations of the crankshaft 22.

Thus, the oscillating speed of the crankshaft 22 will at least to some extent translate to acceleration variations of the output shaft of the gearbox 160. These oscillations will transmit to the wheels of the vehicle causing undesired driving behavior of the vehicle.

In the middle graph the actual acceleration of the crankshaft 22 is evidently oscillating with great amplitude, in the range of approximately +/- 1500 rad/sec². The acceleration of the second secondary mass component l44b, which also represent the acceleration of the input shaft of the gearbox 160, also shows an oscillating pattern, in the range of +/- 350 rad/sec². According to the embodiments described herein, a counteracting torque required to least to some extent reduce the actual acceleration variations of the output shaft of the gearbox 160 is determined, and subsequently applied to the drivetrain by means of the electrical motor 110. The counteracting torque may for example be determined from the speed curve and/or the acceleration curve of the output shaft of the gearbox 160 by means of reading, processing, calculating, or any combination thereof. Suitable input for such determination may e.g. comprise measured values from acceleration sensors, speed sensors, position sensors, or the like. In other embodiments, the counteracting torque is determined from the speed curve and/or the acceleration curve of the input shaft of the gearbox 160 by means of reading, processing, calculating, or any combination thereof.

Preferably, determining the torque required to counteract actual acceleration variations of the output shaft of the gearbox is performed using a real-time model being available during operation of the hybrid drive module. The real-time model, which e.g. may be implemented in the control unit, provides estimations of the behavior of at least parts of the hybrid drive module, and/or the associated internal combustion engine. As the real-time model runs in parallel with operation of the hybrid drive module, it is preferably associated with a state observer of at least some parts of the hybrid drive module and the associated internal combustion engine. The state observer is configured to provide feedback to the model, which in turn can determine an estimate of one or more model states, in particular the actual torque acting on the output shaft. The state observer may e.g. receive measured values of rpm on the input shaft and on the output shaft. From an estimated value of the torque acting on the output shaft, which value is received from the real-time model, the control unit can determine the torque required to at least to some extent reduce said actual acceleration.

It should be noted that the integral of the acceleration curve of the second secondary mass component l44b is not necessarily uniformly distributed over time. This results in the alternating change of speed of the input shaft of the gearbox 160, as can be seen in the first upper graph.

Now referring to the right hand side of the three graphs - ranging from approximately 2.5 seconds and onwards, active dampening of the vibrations is provided by activation of the electrical motor 110. It can be derived from the upper speed diagram that the RPM of the input shaft of the gearbox 160 shows a substantially linear acceleration whilst the primary mass 142 continues to oscillate. Thus, acceleration variations of the input shaft of the gearbox are effectively reduced. The lower diagram of Fig. 3 shows the magnitude and sign/direction of torque applied by the electrical motor 110, which according to embodiments is the determined torque required to least to some extent reduce the actual acceleration variations of the output/input shaft of the gearbox 160.

Prior to activation of the electrical motor 110 (i.e. t < 2.5s) the applied torque is steady at zero. When activated (i.e. t > 2.5s) the electric motor is controlled to apply positive or negative torque alternatively to cancel or at least reduce the acceleration/RPM/ angular velocity variations of the second secondary mass component l44b, and thereby also of the output shaft 102 of the hybrid drive module 100 as well as the output shaft of the gearbox 160.

The effect can be observed in the second diagram of Fig. 3 at t > 2.5s; the variations in acceleration of the second secondary mass component l44b are effectively counteracted by the electrical motor 110, resulting in reduced variations in angular acceleration as observed in the acceleration curve of the second secondary mass component l44b.

For most accurate dampening, it would be advantageous to know the acceleration of the output shaft of the gearbox 160. However, it may also be possible to estimate the acceleration of the output shaft of the gearbox 160 from the actual acceleration of any of the rotating parts upstream the gearbox 160 (i.e. the crankshaft 22, the primary mass 142, the first or second secondary mass components l44a, l44b, the output shaft 102, etc.). Such acceleration may be derived from determined actual speeds, measured or estimated using a variety of methods and sensors. The sensors may be arranged in the hybrid drive module 100 and/or in the drivetrain of the hybrid vehicle and configured to communicate with the control unit 170. Thus, the actual acceleration of the output shaft of the gearbox 160 may be determined, or at least estimated.

The acceleration curve of the primary mass 142 and its integral correlates with the speed curve of the primary mass 142 in the upper diagram. From the second diagram it may be further derived that the acceleration curve of the second secondary mass component l44b, and thus the output shaft of the gearbox 160, is substantially dampened after activation of the electrical motor 110.

With reference to Fig. 4, a method according to one embodiment comprises a first step 202 in which the actual acceleration of the output shaft of the gearbox 160 is determined.

As explained previously, this may be achieved in one of several ways.

For example the actual acceleration of the output shaft of the gearbox 160 is determined by means of a sensor measuring the actual acceleration, or by means of the a sensor arranged and configured to measure the acceleration of another rotating part of the hybrid drive module 100 upstream the gearbox 160; the actual acceleration of the output shaft of the gearbox 160 is subsequently estimated from the measured value.

The actual acceleration of the output shaft of the gearbox 160 may also be determined based on the applied torque of the launch clutch 150. In one embodiment, the torque of launch clutch 150 is estimated. This may be performed by means of an observer running in the control unit 170 and communicating with one or more sensors estimating or measuring the torque of clutch 150, or by means of any suitable method known in the art.

In a further step 204, the determined acceleration of the output shaft of the gearbox 160 may be used to determine the torque required to at least to some extent reduce the actual acceleration. The step 204 may be performed using torque over the launch clutch 150 as feedback for determining the torque required to at least to some extent reduce the actual acceleration. The torque required may be calculated using the control unit 170 capable of communicating with and controlling the electrical motor 110 and comprising a readable medium

containing logic which when executed cause an associated processor to determine the torque required to at least to some extent reduce the actual acceleration.

In a yet further step 206, the electrical motor 110 is controlled to apply the determined torque such that variations in angular acceleration of the output shaft of the gearbox 160 are reduced, or even eliminated. This step may correspond to the electrical motor 110 applying the determined torque to provide a more uniform distribution of the integral of the acceleration curve of the output shaft of the gearbox 160 over a given period of time and thus, a substantially constant rate of change of speed or acceleration.

According to aspects, this involves torque being applied by the electrical motor 110 to the second secondary mass component l44b which connects to the output shaft of the gearbox 160.

For all embodiments described herein, a measured value of velocity,

RPM, acceleration etc. may be the exact current value, a value where a low-pass filter has been applied and/or an average value (such as a moving average, for instance over 720° of rotation of the combustion engine 20).

The method according to aspects of the disclosure thus accomplishes that the input shaft of the gearbox 160 is further isolated from acceleration variations caused by the internal combustion engine 20, resulting in steady operation of a hybrid vehicle featuring the disclosed method 200.

Claims

1. A method for reducing acceleration variations of an output shaft (102) of a hybrid drive module (100), said hybrid drive module (100) comprising an electrical motor (110) being connected to the output shaft (102), wherein a crankshaft (22) of an associated internal combustion engine (20) is connected to an input shaft (101) of the hybrid drive module, and wherein the input shaft (101) is connected to the output shaft (102) via a dual mass flywheel (140) and a first clutch (130), said method comprising:

determining (202) the actual acceleration of the output shaft (102), determining (204) the torque required to at least to some extent reduce said actual acceleration, and

applying (206) said determined torque to said output shaft (102) by activating the electrical motor (110).

2. The method according to claim 1, further comprising providing a real-time model of at least parts of the hybrid drive module and/or the associated internal combustion engine, and estimating the actual torque acting on the output shaft (102) using said model.

3. The method according to claim 2, wherein the real-time model is associated with a state observer which is capable of determining an estimate of one or more model states, such as the torque acting on the output shaft.

4. The method according to any of the preceding claims, wherein one or more of the steps are performed continuously whereby the actual acceleration of the output shaft (102) is reduced.

5. The method according to any one of the preceding claims, wherein determining the actual acceleration of the output shaft (102) is performed by determining the actual acceleration of an output shaft of a gearbox (160) arranged downstream the hybrid drive module (100), and estimating the actual acceleration of the output shaft (102) of the hybrid drive module.

6. The method according to any one of claims 1 to 4, wherein determining the actual acceleration of the output shaft (102) is performed by determining the actual acceleration of a rotating shaft of the hybrid drive module (100), said rotating shaft being selected from the group comprising: an input shaft (101), a primary mass (142) of the dual mass flywheel (140), a first secondary mass component (l44a) of the dual mass flywheel (140), and a second secondary mass component (l44b) of the dual mass flywheel (140).

7. The method according to any one of claims 1 - 6, wherein said electrical motor (110) is coupled to a gearbox (160) via a second clutch (150) and wherein the step of determining the actual acceleration of the output shaft (102) further comprises continuously determining a torque over said second clutch (150).

8. The method according to claim 7, wherein the step of determining the torque over the second clutch (150) is performed by estimating the torque by means of an observer.

9. A hybrid drive module (100), comprising a housing (100) enclosing an electrical motor (110), said electrical motor (110) being connected with to an output shaft (102), wherein a crankshaft (22) of an associated internal combustion engine (20) is connected to an input shaft (101) of the hybrid drive module, and wherein the input shaft (101) is connected to the output shaft (102) via a dual mass flywheel (140) and a first clutch (130), said hybrid drive module (110) further comprising a control unit (170) configured to determine the actual acceleration of the output shaft (102), to determine the torque required to at least to some extent reduce the actual acceleration, and to apply the determined torque to the output shaft (102) by activating the electrical motor (110).

10. A hybrid drive module (100) according to claim 9, wherein the electrical motor (110) is arranged in a coaxial manner on the output shaft (102) downstream of the clutch (130).

11. A hybrid drive module (100) according to claim 9, wherein the electrical motor (110) is arranged in an off-axis manner in relation to the output shaft (102) of the hybrid drive module (100), said electrical motor (110) being connected via a continuous member drive (120) to a second sprocket (124) on the output shaft (102) of the hybrid drive module (100).

12. A vehicle, comprising a hybrid drive module (100) according to claim 9.