U.S. patent application number 13/735463 was filed with the patent office on 2013-05-16 for scavenge pump oil level control system and method.
The applicant listed for this patent is Allison Transmission, Inc.. Invention is credited to Charles F. Long, Thomas A. Wright.
Application Number | 20130121849 13/735463 |
Document ID | / |
Family ID | 46639151 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130121849 |
Kind Code |
A1 |
Long; Charles F. ; et
al. |
May 16, 2013 |
SCAVENGE PUMP OIL LEVEL CONTROL SYSTEM AND METHOD
Abstract
A hybrid vehicle includes a hybrid module, a transmission and a
torque converter. The lubrication system associated with the torque
converter includes an oil sump within the torque converter housing
which is intended to be managed as a "dry" sump oil lubrication
system. There is an oil pump in communication with the sump in
order to manage the sump oil level. By monitoring an operational
parameter of the oil pump motor (pressure, torque, or current) oil
aeration can be detected.
Inventors: |
Long; Charles F.;
(Pittsboro, IN) ; Wright; Thomas A.; (Noblesville,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Allison Transmission, Inc.; |
Indianapolis |
IN |
US |
|
|
Family ID: |
46639151 |
Appl. No.: |
13/735463 |
Filed: |
January 7, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/US2012/024119 |
Feb 7, 2012 |
|
|
|
13735463 |
|
|
|
|
61440878 |
Feb 9, 2011 |
|
|
|
Current U.S.
Class: |
417/53 ; 417/279;
417/293 |
Current CPC
Class: |
Y02T 10/62 20130101;
B60W 50/045 20130101; F04B 49/20 20130101; F04B 23/021 20130101;
B60K 6/48 20130101; B60W 10/023 20130101; F04B 51/00 20130101; F04B
23/02 20130101; F16H 41/30 20130101; F04B 23/00 20130101; B60W
20/00 20130101; Y02T 10/6221 20130101; B60W 10/30 20130101; F01M
11/061 20130101; F16H 57/0447 20130101 |
Class at
Publication: |
417/53 ; 417/279;
417/293 |
International
Class: |
F04B 23/00 20060101
F04B023/00 |
Claims
1. An oil level control system for an oil sump of a hybrid electric
vehicle, said oil sump including a supply of oil with an oil level,
said oil level control system comprising: an electric oil pump
constructed and arranged in fluid communication between said oil
sump and an oil reservoir, said electric oil pump being constructed
and arranged to pump oil from said oil sump to said oil reservoir
to lower the oil level of said sump; and a control module
constructed and arranged in electrical communication with said
electric oil pump for controlling the operation of said electric
oil pump, said control module being programmed with an acceptable
oil level range, said acceptable oil level range being based on an
electric oil pump parameter, wherein said electrical oil pump is
operated as required to maintain said oil level of said oil sump
within said acceptable oil level range.
2. The oil level control system of claim 1 wherein said electric
oil pump parameter is a pump torque reading of said electric oil
pump.
3. The oil level control system of claim 2 wherein said electric
oil pump torque reading is sensed by taking a current reading.
4. The oil level control system of claim 1 wherein said electric
oil pump parameter is a torque oscillation of said electric oil
pump.
5. The oil level control system of claim 4 wherein said electric
oil pump torque oscillation is sensed by taking a current
reading.
6. The oil level control system of claim 1 wherein said electric
oil pump parameter is a pump speed oscillation of said electric oil
pump.
7. The oil level control system of claim 1 wherein said oil sump is
part of a torque converter.
8. A method of adjusting an oil level of an oil sump of a hybrid
electric vehicle, said oil sump including a supply of oil, said
method of adjusting comprising the following steps: (a) providing
an electric oil pump; (b) constructing and arranging said electric
oil pump in flow communication between said oil sump and an oil
reservoir; (c) providing a control module; (d) constructing and
arranging said control module in electrical communication with said
electric oil pump; (e) sensing a parameter value of said electric
oil pump; (f) comparing said sensed parameter value to an
acceptable range for said parameter, said acceptable range
corresponding to an acceptable oil level range; and (g) operating
said electric oil pump as necessary to maintain the oil level of
said oil sump within said acceptable oil level range.
9. The method of adjusting of claim 8 wherein said sensing step
includes sensing a pump torque reading of said electrical oil
pump.
10. The method of adjusting of claim 8 wherein said sensing step
includes sensing a torque oscillation of said electric oil
pump.
11. The method of adjusting of claim 8 wherein said sensing step
includes sensing a pump speed oscillation of said electrical oil
pump.
12. The oil level control system of claim 2 wherein said oil sump
is part of a torque converter.
13. The oil level control system of claim 3 wherein said oil sump
is part of a torque converter.
14. The oil level control system of claim 5 wherein said oil sump
is part of a torque converter.
15. The oil level control system of claim 6 wherein said oil sump
is part of a torque converter.
16. A liquid control system for managing a liquid level within a
supply location, said liquid control system comprising: a liquid
pump constructed and arranged in fluid communication between said
liquid supply location and a transfer location, said liquid pump
being constructed and arranged to pump liquid from said liquid
supply location to said transfer location to lower the liquid level
of said liquid supply location; and a control module constructed
and arranged in electrical communication with said liquid pump for
controlling the operation of said liquid pump, said control module
being programmed with an acceptable liquid level range, said
acceptable liquid level range being based on a liquid pump
parameter, wherein said liquid pump is operated as required to
maintain said liquid level of said liquid supply location within
said acceptable liquid level range.
17. The liquid control system of claim 16 wherein said liquid pump
parameter is a pump torque reading of said liquid pump.
18. The liquid control system of claim 17 wherein said liquid pump
torque reading is sensed by taking a current reading.
19. The liquid control system of claim 16 wherein said liquid pump
parameter is a torque oscillation of said liquid pump.
20. The liquid control system of claim 16 wherein said liquid pump
parameter is a pump speed oscillation of said liquid pump.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of PCT Application No.
PCT/US2012/024119, filed Feb. 7, 2012, which claims the benefit
U.S. Patent Application Ser. No. 61/440,878 filed Feb. 9, 2011,
both of which are hereby incorporated by reference.
BACKGROUND
[0002] With the growing concern over global climate change as well
as oil supplies, there has been a recent trend to develop various
hybrid systems for motor vehicles. While numerous hybrid systems
have been proposed, the systems typically require significant
modifications to the drive trains of the vehicles. These
modifications make it difficult to retrofit the systems to existing
vehicles. Moreover, some of these systems have a tendency to cause
significant power loss, which in turn hurts the fuel economy for
the vehicle. Thus, there is a need for improvement in this
field.
[0003] One of the areas for improvement is in the construction and
arrangement of the hydraulic system. Hybrid vehicles, and in
particular the hybrid module associated with such a vehicle, have
various lubrication and cooling needs which depend on engine
conditions and operational modes. In order to address these needs,
oil is delivered by at least one hydraulic pump. The operation of
each hydraulic pump is controlled, based in part on the lubrication
and cooling needs and based in part on the prioritizing when one or
more hydraulic pump is included as part of the hydraulic system of
the hybrid vehicle. The prioritizing between hydraulic pumps is
based in part on the needs and based in part on the operational
state or mode of the hybrid vehicle.
[0004] Another area for improvement within the overall hydraulics
of the hybrid vehicle is in the management of the oil level within
the torque converter housing. An electric oil pump is used as a
scavenge pump for the oil sump of the torque converter housing. The
scavenge pump is part of a "dry" sump oil lubrication system which
requires that the collecting oil sump pan be kept relatively dry
compared to what is generally understood as a wet sump oil
lubrication system.
[0005] One of the concerns relating to dry sump configurations and
systems is oil aeration which occurs when too little oil is present
in the oil sump. This is the result of excessive scavenging.
Another concern is oil flooding which occurs when too much oil is
present in the oil sump. This is the result of insufficient or
inadequate scavenging. Related concerns are the monetary and energy
costs associated with maintaining an oil level sensor in the sump.
The control system described herein addresses the first two
concerns by monitoring the scavenge pump and adjusting the scavenge
pump performance to try and maintain a desired oil level in the
sump.
SUMMARY
[0006] The hydraulic system (and method) described herein is part
of a hybrid module used within a hybrid system adapted for use in
vehicles and suitable for use in transportation system and into
other environments. The cooperating hybrid system is generally a
self-contained and self-sufficient system which is able to function
without the need to drain resources from other systems in the
corresponding vehicle or transportation system. The hybrid module
includes an electric machine (eMachine).
[0007] This self-sufficient design in turn reduces the amount of
modifications needed for other systems, such as the transmission
and lubrication systems, because the capacities of the other
systems do not need to be increased in order to compensate for the
increased workload created by the hybrid system. For instance, the
hybrid system incorporates its own lubrication and cooling systems
that are able to operate independently of the transmission and the
engine. The fluid circulation system, which can act as a lubricant,
hydraulic fluid, and/or coolant, includes a mechanical pump for
circulating a fluid, along with an electric pump that supplements
workload for the mechanical pump when needed. As will be explained
in further detail below, this dual mechanical/electric pump system
helps to reduce the size and weight of the required mechanical
pump, and if desired, also allows the system to run in a complete
electric mode in which the electric pump solely circulates the
fluid.
[0008] More specifically, the described hydraulic system (for
purposes of the exemplary embodiment) is used in conjunction with a
hybrid electric vehicle (HEV). Included as part of the described
hydraulic system is a parallel arrangement of a mechanical oil pump
and an electric oil pump. The control of each pump and the sequence
of operation of each pump depends in part on the operational state
or the mode of the hybrid vehicle. Various system modes are
described herein relating to the hybrid vehicle. As for the
hydraulic system disclosed herein, there are three modes which are
specifically described and these three modes include an electric
mode (E-mode), a transition mode, and a cruise mode.
[0009] As will be appreciated from the description which follows,
the described hydraulic system (and method) is constructed and
arranged for addressing the need for component lubrication and for
cooling those portions of the hybrid module which experience an
elevated temperature during operation of the vehicle. The specific
construction and operational characteristics provide an improved
hydraulic system for a hydraulic module.
[0010] The compact design of the hybrid module has placed demands
and constraints on a number of its subcomponents, such as its
hydraulics and the clutch. To provide an axially compact
arrangement, the piston for the clutch has a recess in order to
receive a piston spring that returns the piston to a normally
disengaged position. The recess for the spring in the piston
creates an imbalance in the opposing surface areas of the piston.
This imbalance is exacerbated by the high centrifugal forces that
cause pooling of the fluid, which acts as the hydraulic fluid for
the piston. As a result, a nonlinear relationship for piston
pressure is formed that makes accurate piston control extremely
difficult. To address this issue, the piston has an offset section
so that both sides of the piston have the same area and diameter.
With the areas being the same, the operation of the clutch can be
tightly and reliably controlled. The hydraulics for the clutch also
incorporate a spill over feature that reduces the risk of
hydrostatic lock, while at the same time ensures proper filling and
lubrication.
[0011] In addition to acting as the hydraulic fluid for the clutch,
the hydraulic fluid also acts as a coolant for the eMachine as well
as other components. The hybrid module includes a sleeve that
defines a fluid channel that encircles the eMachine for cooling
purposes. The sleeve has a number of spray channels that spray the
fluid from the fluid channel onto the windings of the stator,
thereby cooling the windings, which tend to generally generate the
majority of the heat for the eMachine. The fluid has a tendency to
leak from the hybrid module and around the torque converter. To
prevent power loss of the torque converter, the area around the
torque converter should be relatively dry, that is, free from the
fluid. To keep the fluid from escaping and invading the torque
converter, the hybrid module includes a dam and slinger
arrangement. Specifically, the hybrid module has a impeller blade
that propels the fluid back into the eMachine through a window or
opening in a dam member. Subsequently, the fluid is then drained
into the sump so that it can be scavenged and recirculated.
[0012] The hybrid module has a number of different operational
modes. During the start mode, the battery supplies power to the
eMachine as well as to the electric pump. Once the electric pump
achieves the desired oil pressure, the clutch piston is stroked to
apply the clutch. With the clutch engaged, the eMachine applies
power to start the engine. During the electro-propulsion only mode
the clutch is disengaged, and only the eMachine is used to power
the torque converter. In the propulsion assist mode, the engine's
clutch is engaged, and the eMachine acts as a motor in which both
the engine and eMachine drive the torque converter. While in a
propulsion-charge mode, the clutch is engaged, and the internal
combustion engine solely drives the vehicle. The eMachine is
operated in a generator mode to generate electricity that is stored
in the energy storage system. The hybrid module can also be used to
utilize regenerative braking (i.e., regenerative charging). During
regenerative braking, the engine's clutch is disengaged, and the
eMachine operates as a generator to supply electricity to the
energy storage system. The system is also designed for engine
compression braking, in which case the engine's clutch is engaged,
and the eMachine operates as a generator as well.
[0013] Focusing now on the torque converter portion of the HEV, the
oil sump of the torque converter housing is constructed and
arranged to be scavenged by an electric oil pump. The goal is to
keep the sump of the torque converter housing "dry" without having
excessive aeration and without flooding. Excessive aeration is
typically the result of excessive scavenging. Flooding is typically
the result of insufficient or inadequate scavenging. Instead of
incurring the monetary cost and the energy cost associated with
adding an oil level sensor to the torque converter sump, the
described control system focuses on the status and performance
characteristics of the electric oil pump.
[0014] One oil pump monitoring and adjusting option is to evaluate
the pump torque (sensed by current) and then vary the pump speed,
as needed, to try and maintain the sump oil level within the
desired range. Another oil pump monitoring and adjusting option is
to vary the pump speed based on pump torque oscillations (sensed by
current readings). A still further oil pump monitoring and
adjusting option is to vary the pump speed based on the presence of
pump speed oscillations.
[0015] By utilization of one of the monitoring and adjusting
options, one or more of the following benefits is expected: [0016]
1. Reduced oil aeration. [0017] 2. Reduced main oil sump level
variation. [0018] 3. Sandwich sump oil level closed loop control.
[0019] 4. Reduced spin losses. [0020] 5. Improved fuel economy.
[0021] 6. Avoid excessive pressurization of downstream components.
[0022] 7. Reduced cost (eliminates need for oil level sensor).
[0023] Further forms, objects, features, aspects, benefits,
advantages, and embodiments of the present invention will become
apparent from a detailed description and drawings provided
herewith.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 illustrates a diagrammatic view of one example of a
hybrid system
[0025] FIG. 2 is a schematic illustration of the oil flow and
control logic associated with a torque converter which is a part of
the FIG. 1 hybrid system.
[0026] FIG. 3 is a graph of pump pressure versus time as a way to
assess air ingestion.
[0027] FIG. 4 is a graph of peak-to-peak pressure versus time as a
way to present air ingestion information.
[0028] FIG. 5 is a graph of the integration of the FIG. 4
information versus time using the slope of the line to denote air
ingestion information.
DETAILED DESCRIPTION
[0029] For the purposes of promoting an understanding of the
disclosure, reference will now be made to the embodiments
illustrated in the drawings and specific language will be used to
describe the same. It will nevertheless be understood that no
limitation of the scope of the disclosure is thereby intended, such
alterations and further modifications in the illustrated device and
its use, and such further applications of the principles of the
disclosure as illustrated therein being contemplated as would
normally occur to one skilled in the art to which the disclosure
relates.
[0030] FIG. 1 shows a diagrammatic view of a hybrid system 100
according to one embodiment. The hybrid system 100 illustrated in
FIG. 1 is adapted for use in commercial-grade trucks as well as
other types of vehicles or transportation systems, but it is
envisioned that various aspects of the hybrid system 100 can be
incorporated into other environments. As shown, the hybrid system
100 includes an engine 102, a hybrid module 104, an automatic
transmission 106, and a drive train 108 for transferring power from
the transmission 106 to wheels 110. The hybrid module 104
incorporates an electrical machine, commonly referred to as an
eMachine 112, and a clutch 114 that operatively connects and
disconnects the engine 102 with the eMachine 112 and the
transmission 106.
[0031] The hybrid module 104 is designed to operate as a
self-sufficient unit, that is, it is generally able to operate
independently of the engine 102 and transmission 106. In
particular, its hydraulics, cooling and lubrication do not directly
rely upon the engine 102 and the transmission 106. The hybrid
module 104 includes a sump 116 that stores and supplies fluids,
such as oil, lubricants, or other fluids, to the hybrid module 104
for hydraulics, lubrication, and cooling purposes. While the terms
oil or lubricant or lube will be used interchangeably herein, these
terms are used in a broader sense to include various types of
lubricants, such as natural or synthetic oils, as well as
lubricants having different properties. To circulate the fluid, the
hybrid module 104 includes a mechanical pump 118 and an electric
pump 120 in cooperation with a hydraulic system 200 (see FIG. 2).
With this parallel combination of both the mechanical pump 118 and
electric pump 120, the overall size and, moreover, the overall
expense for the pumps is reduced. The electric pump 120 cooperates
with the mechanical pump 118 to provide extra pumping capacity when
required. The electric pump 120 is also used for hybrid system
needs when there is no drive input to operate the mechanical pump
118. In addition, it is contemplated that the flow through the
electric pump 120 can be used to detect low fluid conditions for
the hybrid module 104. In one example, the electric pump 120 is
manufactured by Magna International Inc. of Aurora, Ontario, Canada
(part number 29550817), but it is contemplated that other types of
pumps can be used.
[0032] The hybrid system 100 further includes a cooling system 122
that is used to cool the fluid supplied to the hybrid module 104 as
well as the water-ethylene-glycol (WEG) to various other components
of the hybrid system 100. In one variation, the WEG can also be
circulated through an outer jacket of the eMachine 112 in order to
cool the eMachine 112. Although the hybrid system 100 has been
described with respect to a WEG coolant, other types of antifreezes
and cooling fluids, such as water, alcohol solutions, etc., can be
used. With continued reference to FIG. 1, the cooling system 122
includes a fluid radiator 124 that cools the fluid for the hybrid
module 104. The cooling system 122 further includes a main radiator
126 that is configured to cool the antifreeze for various other
components in the hybrid system 100. Usually, the main radiator 126
is the engine radiator in most vehicles, but the main radiator 126
does not need to be the engine radiator. A cooling fan 128 flows
air through both fluid radiator 124 and main radiator 126. A
circulating or coolant pump 130 circulates the antifreeze to the
main radiator 126. It should be recognized that other various
components besides the ones illustrated can be cooled using the
cooling system 122. For instance, the transmission 106 and/or the
engine 102 can be cooled as well via the cooling system 122.
[0033] The eMachine 112 in the hybrid module 104, depending on the
operational mode, at times acts as a generator and at other times
as a motor. When acting as a motor, the eMachine 112 draws
alternating current (AC). When acting as a generator, the eMachine
112 creates AC. An inverter 132 converts the AC from the eMachine
112 and supplies it to an energy storage system 134. The eMachine
112 in one example is an HVH410 series electric motor manufactured
by Remy International, Inc. of Pendleton, Ind., but it is
envisioned that other types of eMachines can be used. In the
illustrated example, the energy storage system 134 stores the
energy and resupplies it as direct current (DC). When the eMachine
112 in the hybrid module 104 acts as a motor, the inverter 132
converts the DC power to AC, which in turn is supplied to the
eMachine 112. The energy storage system 134 in the illustrated
example includes three energy storage modules 136 that are
daisy-chained together to supply high voltage power to the inverter
132. The energy storage modules 136 are, in essence,
electrochemical batteries for storing the energy generated by the
eMachine 112 and rapidly supplying the energy back to the eMachine
112. The energy storage modules 136, the inverter 132, and the
eMachine 112 are operatively coupled together through high voltage
wiring as is depicted by the line illustrated in FIG. 1. While the
illustrated example shows the energy storage system 134 including
three energy storage modules 136, it should be recognized that the
energy storage system 134 can include more or less energy storage
modules 136 than is shown. Moreover, it is envisioned that the
energy storage system 134 can include any system for storing
potential energy, such as through chemical means, pneumatic
accumulators, hydraulic accumulators, springs, thermal storage
systems, flywheels, gravitational devices, and capacitors, to name
just a few examples.
[0034] High voltage wiring connects the energy storage system 134
to a high voltage tap 138. The high voltage tap 138 supplies high
voltage to various components attached to the vehicle. A DC-DC
converter system 140, which includes one or more DC-DC converter
modules 142, converts the high voltage power supplied by the energy
storage system 134 to a lower voltage, which in turn is supplied to
various systems and accessories 144 that require lower voltages. As
illustrated in FIG. 1, low voltage wiring connects the DC-DC
converter modules 142 to the low voltage systems and accessories
144.
[0035] The hybrid system 100 incorporates a number of control
systems for controlling the operations of the various components.
For example, the engine 102 has an engine control module (ECM) 146
that controls various operational characteristics of the engine 102
such as fuel injection and the like. A transmission/hybrid control
module (TCM/HCM) 148 substitutes for a traditional transmission
control module and is designed to control both the operation of the
transmission 106 as well as the hybrid module 104. The
transmission/hybrid control module 148 and the engine control
module 146 along with the inverter 132, energy storage system 134,
and DC-DC converter system 140 communicate along a communication
link as is depicted in FIG. 1.
[0036] To control and monitor the operation of the hybrid system
100, the hybrid system 100 includes an interface 150. The interface
150 includes a shift selector 152 for selecting whether the vehicle
is in drive, neutral, reverse, etc., and an instrument panel 154
that includes various indicators 156 of the operational status of
the hybrid system 100, such as check transmission, brake pressure,
and air pressure indicators, to name just a few.
[0037] As noted before, the hybrid system 100 is configured to be
readily retrofitted to existing vehicle designs with minimal impact
to the overall design. All of the systems including, but not
limited to, mechanical, electrical, cooling, controls, and
hydraulic systems, of the hybrid system 100 have been configured to
be a generally self-contained unit such that the remaining
components of the vehicle do not need significant modifications.
The more components that need to be modified, the more vehicle
design effort and testing is required, which in turn reduces the
chance of vehicle manufacturers adopting newer hybrid designs over
less efficient, preexisting vehicle designs. In other words,
significant modifications to the layout of a preexisting vehicle
design for a hybrid retrofit require, then, vehicle and product
line modifications and expensive testing to ensure the proper
operation and safety of the vehicle, and this expense tends to
lessen or slow the adoption of hybrid systems. As will be
recognized, the hybrid system 100 not only incorporates a
mechanical architecture that minimally impacts the mechanical
systems of pre-existing vehicle designs, but the hybrid system 100
also incorporates a control/electrical architecture that minimally
impacts the control and electrical systems of pre-existing vehicle
designs.
[0038] Further details regarding the hybrid system 100 and its
various subsystems, controls, components and modes of operation are
described in Provisional Patent Application No. 61/381,615, filed
Sep. 10, 2010, which is hereby incorporated by reference in its
entirety.
[0039] The hybrid module 104 is generally designed to be a
self-contained unit and accordingly it has its own lubrication
system. When the hybrid module 104 is coupled to the transmission
106, some leakage of the fluid into the transmission 106 may occur.
The fluid (e.g., oil) may flow into parts of the transmission that
are normally dry or absent fluid. For instance, fluid may flow into
the area surrounding the torque converter 172. As a result, the
viscous nature of the fluid can slow down the torque converter 172
and/or create other issues, such as parasitic loss and over heating
of the oil. Moreover, if enough fluid exits the hybrid module 104,
an insufficient amount of fluid may exist in the hybrid module 104,
which can cause damage to its internal components.
[0040] At the interface between the hybrid module 104 and the
transmission 106, the hybrid module 104 has a dam and slinger (or
impeller) arrangement that is used to retain the fluid within the
hybrid module. An adapter ring has a slinger blade that is designed
to sling the fluid back into the hybrid module 104. A sleeve has a
dam structure that is used to retain the fluid and direct it to the
sump 116. The dam structure has a dam passageway positioned such
that the slinger blade is able to direct the fluid through the dam
passageway and subsequently into the sump 116.
[0041] Referring now to FIG. 2, a schematic diagram is provided for
the described monitoring and adjusting of electric oil pump 170
which is operably connected to (i.e., in flow communication with)
torque converter 172. The torque converter 172 receives a supply of
oil for lubrication and cooling of the torque converter components
and portions within the torque converter housing. The used and
excess oil drains off and accumulates in the lower pan or sump 174
of the torque converter. The electric oil pump 170 is constructed
and arranged as a scavenging pump in order to pump oil out of the
sump 174 and return that oil to a larger oil reservoir 186 via
conduit 176.
[0042] The level of oil in sump 174 is a factor of delivery, flow
rate, and the speed of electric oil pump 170. There are two
conditions which are seen as performance issues and which should be
corrected or resolved by changing the speed of the electric oil
pump. One condition or concern is described as oil aeration which
is the result of excessive scavenging. If the oil level is too low
as scavenging continues, the electric oil pump draws in a mixture
of air and oil. The other condition or concern is described as
"flooding" which is the result of inadequate scavenging. Flooding
is also seen as a high oil level in the torque converter housing,
i.e., in sump 174.
[0043] When oil level is relatively low, the hybrid system has the
potential for drawing air into the intake of the pump. At
moderately reduced oil levels, this can manifest itself as a
localized whirlpool effect which introduces air gradually into the
system through the intake of the oil suction filter. The whirlpool
effect is dependent on oil velocity and temperature. Higher
velocities in combination with higher viscosities present the
biggest issue. This would most likely occur on cold start at higher
engine speeds. As a result of this air induction, the entrained air
level in the oil increases. This can lead to regulator valve
instability (noisy pressure), elevated oil temperatures, longer
clutch fill times, and minor shift quality issues.
[0044] At severely low oil levels the bottom of the oil suction
filter is uncovered to air in a more general sense. This results in
sever ingestion of air to the suction side of the pump. The
aforementioned issues become more pronounced and there is the
potential for pump priming issues as well. Regulator valve
instability can increase to the point of audible noise which can be
heard by the operator. Elevated temperatures are more pronounced
and can lead to transmission overheating.
[0045] Generally high oil levels result in oil contact with moving
parts within the gearbox itself. With moderate overfills it results
in foaming and aeration with mild increases in spin losses. This
can also lead to minor increases in oil temperature. With
significantly high oil levels, the foaming and aeration results in
much higher spin losses (reduced fuel economy) and transmission
overheating. The problem tends to self propagate at this point. The
foaming expands the oil volume and level resulting in further
foaming which leads to still higher oil levels. Eventually the
foaming and aeration can result in spewing out the breather and
severe overheating.
[0046] Each condition is able to be rectified by changing the speed
of the electric oil pump 170. In the event of oil aeration, slow
down the pump speed. In the event of flooding, increase the pump
speed. The question then becomes how best to monitor and determine
the oil level in the sump of the torque converter. One option is to
add an oil level sensor. However, this option introduces an added
monetary cost and an added energy cost. Instead, the disclosed
exemplary embodiment introduces improvement options, each of which
involve monitoring operating parameters or conditions of the
electric oil pump 170.
[0047] A first improvement option is to vary the speed of oil pump
170 based on the torque of the oil pump which is sensed by a
current reading from the pump motor. In FIG. 2, control module 178
communicates with the oil pump 170 via data line 180 in order to
sense the current and derive a reading. This current reading is
then used to determine if the speed of oil pump 170 needs to be
varied and, if so, how. The speed of oil pump 170 is increased by
control module 178 via data line 182 if the current reading
indicates flooding of the torque converter 172. If the current
reading indicates oil aeration, then the speed of oil pump 170 is
decreased by a signal from control module 178 via data line
182.
[0048] When the oil level is low, there is the potential for
drawing air into the intake of the scavenge pump. This air
ingestion into the scavenge pump may also be described as aeration.
When this occurs, the pump mass flow rate drops and tends to be
inconsistent (noisy). One way this effect can be "seen" is by
measuring the pressure over time. The FIG. 3 graph or chart depicts
one option for displaying this pressure. The Y-axis depicts
"pressure" in kpa units. The X-axis is "time" in seconds. The
magnitude or extent of the pressure fluctuations gives an
indication of whether or not there is any significant air ingestion
by the scavenge pump. While the FIG. 3 graph shows pressure versus
time, torque or current measurements of the scavenge pump will
provide a similar display of whether or not there is any
significant air ingestion by the scavenge pump.
[0049] The vehicle includes a transmission control module (TCM)
which is constructed and arranged to monitor the range of
(pressure) oscillations and calculate the peak-to-peak noise versus
time. This is displayed by the FIG. 4 graph. This graph displays
the peak-to-peak pressure in kpa units along the Y-axis and time,
in seconds, along the X-axis. The TCM is capable of monitoring the
peak-to-peak noise and flag aeration when the noise threshold
exceeds a calibrated level.
[0050] The analysis can be taken a further step by integrating the
FIG. 4 graph data with respect to time. This integration result is
shown by the FIG. 5 graph. The slope of the line depicts the
condition, noting that a steeper slope corresponds to some level of
air ingestion while a flatter line of less slope corresponds to a
condition of little or no air ingestion by the scavenge pump.
[0051] The FIG. 5 graph provides a clear distinction, based on the
slope of the line, of when air is ingested (the steeper slope) and
when no noticeable amount or volume of air is ingested (the flatter
slope). By calibrating the slope and establishing a reference table
(or using one already created), a measurement of the slope of the
FIG. 5 graph line will yield the level (i.e., the amount or volume)
of air ingested by the scavenge pump. Relative measures are given
in Table I which corresponds to FIG. 5.
TABLE-US-00001 TABLE I Integration Air Slope Entrainment 0.2 <2%
0.3 3% 0.4 4% 0.5 5% 0.6 6% 0.7 >7%
[0052] As noted above, the data displayed in the graphs of FIGS.
3-5 is based on pressure readings and the peak-to-peak pressure
readings. However, in lieu of using pressure, scavenge pump torque
measurements will provide a similar response and way to assess air
ingestion (i.e., aeration). The same is true for scavenge pump
current measurements. Depending on the existence or level of any
oil aeration (i.e., air ingestion), the speed of the oil pump 170
can be varied. Ideally for a "dry" sump, the oil level will be
managed such that it is controlled at the point where aeration
might just start. If that is not indicated, then increase the pump
speed. Once aeration is detected, then slow the speed of the pump.
This somewhat continual adjusting of the pump speed is one way to
keep the oil level at the threshold of aeration which is a suitable
way to manage a "dry" sump. Referring to FIG. 2, the control module
178 communicates with the oil pump 170 via data line 182. Readings
from the oil pump motor are received by the control module via data
line 180. These connections are important in order to obtain the
data and control scavenge pump operation.
[0053] By controlling the scavenge pump speed through the
monitoring of the pump motor and/or the monitoring of pump pressure
fluctuations or oscillations or torque oscillations and/or speed
oscillations, one or more of the following benefits is to be
expected: [0054] 1. Reduced oil aeration. This results in better
cooling, improved valve stability, and improved shift quality.
[0055] 2. Reduced main oil sump level variation. This results in
less oil volume required, thereby reducing cost and weight. [0056]
3. Sandwich sump oil level closed loop control. This eliminates the
need for a separate oil sump in the hybrid motor housing, thereby
reducing cost and complexity. [0057] 4. Reduced spin losses. This
results in lower cool temperatures (improved reliability) and
improved fuel economy. [0058] 5. Improved fuel economy. This
results in lower operator costs and improved sales. [0059] 6. Avoid
excessive pressurization of downstream components. This is achieved
by reducing the noise associated with excessive aeration. The
hydraulic components will see less fatigue stress and thereby
provide longer operational life. [0060] 7. Reduced cost (eliminates
the need for an oil level sensor). Also there is the option of
eliminating a separate sump, oil pump, regulator valve, etc.
[0061] While the preferred embodiment of the invention has been
illustrated and described in the drawings and foregoing
description, the same is to be considered as illustrative and not
restrictive in character, it being understood that all changes and
modifications that come within the spirit of the invention are
desired to be protected.
* * * * *