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TRANSMISSION SYSTEM UTILIZING CENTRIFUGAL CLUTCH
BACKGROUND OF THE INVENTION
RELATED APPLICATIONS
[0001] This application is a continuation -in - part of provisional application
60/255358 filed December 13, 2000.
[0002] This application is related to U.S. Serial No. 09/(00-rTRN-348) titled:
CONTROL FOR TRANSMISSION SYSTEM UTILIZING CENTRIFUGAL CLUTCH and
U.S. Serial No. 09/(00-rTRN-403) titled: CENTRIFUGAL CLUTCH, both assigned to
EATON CORPORATION, assignee of this invention, and both filed the same day as
this application.
FIELD OF THE INVENTION
[0003] The present invention relates to a centrifugal master clutch and a
vehicular transmission system utilizing same. In particular, the present invention relates
to an automated vehicular transmission system comprising an engine, a multiple ratio
transmission, a centrifugally operated master friction clutch for drivingly coupling the
engine to the transmission and a controller for controlling fueling of the engine during
vehicle launch conditions, as a function of throttle position and other sensed system
operating conditions such as at least one of engine speed, transmission input shaft
speed, transmission output shaft speed, engine torque and engaged gear ratio.
[0004] More particularly, a preferred embodiment of the present invention relates
to a vehicular automated mechanical transmission system utilizing a centrifugal master
friction clutch controlled solely by engine speed and a controller for controlling engine
fueling during vehicle launch (i.e., start from stop) conditions on a closed loop basis to
provide a target engine speed and/or engine torque.
DESCRIPTION OF THE PRIOR ART
[0005] Automated mechanical transmission systems not requiring the vehicle
driver or operator to operate the vehicle master clutch (so called "two-pedal systems"),
and clutch controls and actuators therefore, are known in the prior art as may be seen
by reference to U.S. Patent No."s: 4,081,065; 4,361,060; 4,936,428; 5,439,428;
5,634,867; 5,630,773; 5,960,916 and; 5,947,847, the disclosures of which are
incorporated herein by reference. These systems are not totally satisfactory as
separate clutch actuators, sensors and/or, electrical and/or fluid power (i.e.,
compressed and/or hydraulic) connections thereto are required which adds to the
expense of providing, assembling and maintaining such systems.
[0006] Centrifugally operated friction clutches are well known in the prior art and
typically include a driving input member driven by a prime mover, usually an electric
motor or internal combustion engine, and weights rotatable with the driving member
which, upon rotation of the driving member, will move radially outwardly under the effect
of centrifugal force to cause the driving input member to frictionally engage a driven
output member. Examples of centrifugally operated clutches may be seen by reference
to U.S. Patent No."s: 3,580,372; 3,580,372; 3,696,901; 5,437,356; 3,810,533;
4,819,779; 5,441,137; 5,730,269; and; 4,610,343, the disclosures of which are
incorporated herein by reference.
[0007] Fully or partially automated mechanical transmission systems that, upon
determining that a dynamic shift from a currently engaged ratio into neutral and then
into a target ratio is desirable, will, while maintaining the vehicle master friction clutch
engaged, initiate automatic fuel control to cause reduced torque across the jaw clutches
to be disengaged, are known in the prior art as may be seen by reference to U.S.
Patent No."s: 4,850,236; 5,820,104; 5,582,558; 5,735,771; 5,775,639; 6,015,366; and
6,126,570, the disclosures of which are incorporated herein by reference. These
systems include systems that attempt to fuel the engine to achieve a sustained zero
driveline torque, and systems, which force torque reversals, see U.S. Patent No.:
4,850,236. These systems, upon sensing a neutral condition, will, while maintaining the
master clutch engaged, cause the engine to rotate at a speed determined to cause
synchronous conditions for engaging the target ratio.
[0008] Vehicular driveline systems, especially for heavy-duty vehicles, utilizing
centrifugal clutches have not been satisfactory as the engines were typically controlled
by throttle device position, not on a closed loop basis based upon a target engine
speed and/or engine torque, and thus did not provide acceptable control for smooth
vehicle launch and low speed operation. Prior art vehicular driveline systems utilizing
centrifugal master clutches were not provided with clutches having damage and/or
overheating protection and/or were not configured to lock up and release at engine
speeds selected to permit dynamic shifting with the master clutch engaged.
SUMMARY OF INVENTION
[0009] In accordance with the present invention, the drawbacks of the prior art
are reduced or minimized by the provision of a centrifugal master friction clutch, and a
vehicular automated transmission system utilizing same, which utilizes closed loop
control to provide acceptable performance for heavy duty vehicle launch operations and
low speed operation and is configured to allow dynamic shifting with the master clutch
engaged. Preferably, the closed loop control will provide protection from damage
and/or overheating.
[0010] The above is accomplished by providing a centrifugal clutch structure
which will initially lockup at an engine speed below the speed at which upshifts are
required and will not release from a lockup condition at engine speeds above (i) the
highest speeds at which down shifts are required and (ii) the lowest allowable expected
engine speed after completion of an upshift and by controlling fueling of the engine
during launch to cause engine speed and/or engine torque to equal or not exceed a
target value determined as a function of sensed input signal values indicative of two or
more of throttle device position, engine speed, engine torque, transmission input shaft
speed, transmission output shaft speed, transmission engaged ratio and clutch slip.
[0011] The centrifugal master clutch requires no external clutch actuator or
sensor, and no connections to mechanical linkages, electrical power and/or fluid power.
[0012] Accordingly, it is an object of the present invention to provide a new and
improved centrifugally operated vehicular master friction clutch and automated
mechanical transmission system utilizing same.
[0013] This and other objects and advantages of the present invention will
become apparent from a reading of the following description of the preferred
embodiment taken in connection with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Fig. 1 is a schematic illustration of a vehicular drivetrain using the
centrifugal clutch and engine fuel control of the present invention.
[0015] Fig. 2 is a schematic illustration, in graphical format, of the clamp force
characteristics of the centrifugal clutch of the present invention at various engine
speeds.
[0016] Fig. 3 is a schematic illustration, in graphical format, of target engine
speeds for various throttle positions at vehicle launch for the system of the present
invention.
[0017] Fig. 4 is a partial top view, in section, of the cover and centrifugal
mechanism of the clutch of the present invention.
[0018] Fig. 5 is a partial sectional view of the roller, ramp, and clamp force
limiting spring mechanism utilized with the centrifugal mechanism of Fig. 4.
[0019] Fig 6A and 6B are partial sectional views illustrating the position of the
flyweights in the fully radially inward clutch disengaged position and the fully radially
outward clutch fully engaged position, respectively.
[0020] Fig. 7 is a schematic partial sectional view of the present invention.
[0021] Fig. 8A and 8B are schematic illustrations, in flowchart format, of the
launch logic of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] An at least partially automated vehicular drivetrain system 10 using the
centrifugally operated friction master clutch and control of the present invention is
schematically illustrated in Fig. 1. System 10 may be fully automated, as seen by way
of example in U.S. Patent No.: 4,361,060, partially automated, as seen by way of
example in U.S. Patent No"s: 4,648,290 and 5,409,432, or manual with controller assist,
as seen by way of example in U.S. Patent No"s: 4,850,236; 5,582,558; 5,735,771; and
6,015,366.
[0023] In system 10, a change-gear transmission 12 comprising a main
transmission section 14 connected in series with a splitter-type auxiliary transmission
section 16 is drivingly connected to an internal combustion engine 18, such as a well-
known gasoline or diesel engine, by the centrifugal master friction clutch 20 of the
present invention. Transmissions 12, by way of example, may be of the type well known
in the prior art and are sold by the assignee of this application, EATON
CORPORATION, under the trademarks "Super-10" and "Lightning", and may be seen
in greater detail by reference to U.S. Pat. No"s: 4,754,665; 6,015,366; 5,370,013;
5,974,906; and 5,974,354, the disclosures of which are incorporated herein by
reference.
[0024] Engine 18 includes a crankshaft 22, which is attached to a driving
member 60 of centrifugal master clutch 20, which frictionally engages with, and
disengages from, a driven member 62, which is attached to the input shaft 28 of the
transmission. A transmission output shaft 30 extends from the auxiliary transmission
section 16 for driving connection to the vehicular drive wheels, as through a drive axle
31 or transfer case.
[0025] The terms "engaged" and "disengaged" as used in connection with a
master friction clutch refer to the capacity, or lack of capacity, respectively, of the clutch
to transfer a significant amount of torque. Mere random contact of the friction surfaces,
in the absence of at least a minimal clamping force, is not considered engagement.
[0026] As may be seen from Fig. 1, centrifugal clutch 20 requires no external
clutch actuator and is operated as function of the rotational speed (ES) of the engine.
Centrifugal clutch 20 also requires no connections to operating linkages, command
signal inputs, power electronics and/or compressed air and/or hydraulic conduits. The
most economical application of the present invention is with a dry clutch, however, the
present invention is also applicable to wet clutch technology.
[0027] Transmission system 10 further includes rotational speed sensors 32 for
sensing engine rotational speed (ES), 34 for sensing input shaft rotational speed (IS),
and 36 for sensing output shaft rotational speed (OS), and providing signals indicative
thereof. A sensor 37 provides a signal THL indicative of throttle pedal position or of
torque demand. The signal is usually a percentage (0% to 100%) of fuel throttle
position. Engine 18 may be electronically controlled, including an electronic
controller 38 communicating over an electronic data link (DL) operating under an
industry standard protocol such as SAE J-1922, SAE J-1939, ISO 11898 or the like.
[0028] An X-Y shift actuator, which by way of example may be of the types
illustrated in U.S. Pat. No"s: 5,481,170; 5,281,902; 4,899,609; and 4,821,590, may be
provided for automated or shift-by-wire shifting of the transmission main section and/or
auxiliary section. Alternately, a manually operated shift lever 42 having a shift knob 44
thereon may be provided. Shift knob 44 may be of the type described in
aforementioned U.S. Pat. No: 5,957,001. As is well known, shift lever 42 is manually
manipulated in a known shift pattern for selective engagement and disengagement of
various shift ratios. Shift knob 44 may include an intent to shift switch 44A by which the
vehicle operator will request automatic engine fueling control to relieve torque lock and
allow a shift to transmission neutral. A shift selector 46 allows the vehicle driver to
select a mode of operation and provides a signal GRT indicative thereof.
[0029] System 10 includes a control unit 50, preferably a microprocessor-based
control unit of the type illustrated in U.S. Pat. No"s: 4,595,986; 4,361,065; and
5,335,566, the disclosures of which are incorporated herein by reference, for receiving
input signals 54 and processing same according to predetermined logic rules to issue
command output signals 56 to system actuators, such as engine controller 38, shift
actuator 40, and the like.
[0030] As is known, to disengage a jaw clutch in a vehicular mechanical
transmission, especially in a heavy-duty vehicle, it is necessary to relieve torque lock at
the engaged jaw clutch. If opening the master friction clutch 20 is not desirable, torque
lock can be relieved by fueling the engine to cause assumed zero driveline torque
and/or by forcing torque reversals, which will positively cause crossings of zero driveline
torque.
[0031] Fully or partially automated mechanical transmission systems that, upon
determining that a shift from a currently engaged ratio into neutral and then into a target
ratio is desirable, will, while maintaining the vehicle master friction clutch engaged,
initiate automatic fuel control to cause reduced torque across the jaw clutches to be
disengaged, are also known in the prior art as may be seen by reference to above-
mentioned U.S. Patent No."s: 4,850,236; 5,582,558; 5,735,771; 5,775,639; 6,015,366;
and 6,126,570. Shifting with the master clutch remaining engaged is preferred in many
situations, as such shifts tend to be of a higher shift quality and/or cause less wear on
the driveline. These systems include systems that attempt to fuel the engine to achieve
and maintain a zero driveline torque, see U.S. Patent No.: 4,593,580, the disclosure of
which is incorporated herein by reference, and systems that fuel the engine to force one
or more torque reversals, see U.S. Patent No.: 4,850,236. Upon sensing a
transmission neutral condition, the clutch is maintained engaged and the engine speed
commanded to a substantially synchronous speed for engaging a target gear ratio
(ES=OSxGRT).
[0032] Control of engine torque to achieve a desired output or flywheel torque is
known as and may be seen by reference U.S. Pat No. 5,620,392, the disclosure of
which is incorporated herein by reference. Engine torque as used herein refers to a
value indicative of an engine torque, usually gross engine torque, from which an output
or flywheel torque may be calculated or estimated. The relationship of gross engine
torque to flywheel torque is discussed in U.S. Pat. No"s: 5,509,867 and 5,490,063, the
disclosures of which are incorporated herein by reference.
[0033] One or more engine torque"s or torque limit values may be commanded
on, or read from, an industry standard data link, DL, such as an SAE J-1922, SAE J-
1939 or ISO11898 compliant datalink.
[0034] By way of example, datalinks complying to the SAE J1939 or similar
protocol, allow the system controller 50 to issue commands over the datalink for the
engine to be fueled in one of several modes, such as (i) in accordance with the
operator"s setting of the throttle, (ii) to achieve a commanded or target engine speed
(ES=EST), (iii) to achieve a commanded or target engine torque (ET=ETT) and (iv) to
maintain engine speed and engine torque below limits (ES
Many input/informational signals, such as engine speed (ES), engine torque (ET), and
the like may also be carried by the datalink.
[0035] The structure of the centrifugal clutch 20 will be described in greater detail
below. Clutch 20 includes an input or driving portion 60 fixed for rotation with engine
crankshaft 22 (usually at the engine flywheel), and an output or driven portion 62 fixed
for rotation on transmission input shaft 28. As is known, rotation of the input member
60 will cause clutch 20 to engage and drivingly connect the engine output, usually an
engine flywheel, or the like, to the transmission input shaft 28. The clamping force, and
thus the torque transfer capacity of the clutch 20 is a function of rotational speed (ES)
of engine 18 and clutch input member 60. The clutch 20 should reach incipient
engagement at an engine speed slightly greater than engine idle, and should fully
engage at an engine speed lower than the engine speed at which a first upshift is
required. Unlike typical spring applied master friction clutches, which are normally
engaged, clutch 20 is disengaged at lower engine speeds.
[0036] To allow proper vehicle launch and dynamic shifting with the master clutch
engaged, clutch 20, once fully engaged, should remain fully engaged at engine speeds
greater than (i) the highest expected speed at which downshifts are initiated and (ii) the
minimum expected engine speed after an upshift. Incipient engagement is the initial
torque transfer contact of clutch friction surfaces as may be seen by reference to U.S.
Patent No"s: 4,646,891 and 6,022,295, the disclosures of which are incorporated herein
by reference. Logic for only initiating single or skip upshifts only if the expected engine
speed at completion of the shift exceeds a minimum reference value may be seen by
reference to U.S. Patent No"s: 6,113,516 and 6,149,545, the disclosures of which are
incorporated herein by reference.
[0037] Figure 2 is a graphical representation of the clamping force, of a preferred
embodiment the clutch 20, and thus the torque transfer capacity, at various engine
speeds.
[0038] In the illustrated example, system 10 is a heavy duty truck driveline,
engine 18 is an electronically controlled diesel engine having an idle speed of about
600RPM to 700RPM, point 64, and a governed top speed of about 1800RPM to
2000RPM. In the preferred embodiment, the clutch 20 will move to incipient
engagement at about 800 RPM, point 66 (ESIE), which is slightly above idle, and will
have an increasing clamp load, line 70, as engine speed increases. The clutch will be
most fully engaged at or below the capped maximum clamp force, 4000 pounds, at
about 1400 RPM, point 72. Once at maximum clamp load, which is selected to lock up
the clutch under extreme conditions (i.e., substantially zero slip at considerably greater
than expected torque loads), the clutch 20 will remain locked up, lines 74 and 76, until
engine speed becomes less than about 850 RPM, point 78. At the release point, the
clutch 20 will very rapidly disengage with decreasing engine speed, line 80, to prevent
engine stalling.
[0039] 850 RPM is below (i) the minimum engine speed at which downshifts will
be commanded and (ii) the minimum expected engine speed at completion of an upshift
at which an upshift, single or skip, will be initiated, see U.S. Patent No. 6,149,545, the
disclosure of which is incorporated herein by reference. Accordingly, a centrifugal
clutch 20 having the performance characteristics indicated on Fig. 2, which will allow a
smooth modulated vehicle launch, and will assure that the clutch remains engaged for
dynamic upshifting and downshifting.
[0040] The structure of a preferred embodiment of centrifugal clutch 20 may be
seen by reference to Fig"s: 5, 6,A, 6B, and 7. Clutch 20 includes a clutch bell housing
assembly 100, friction disc assembly 102, intermediate pressure plate 104, and friction
disc assembly 106. As is well known from conventional clutches, bell housing
assembly 100 and intermediate pressure plate 104 mount to the engine flywheel for
rotation therewith and comprise the driving portion 60 of the clutch, friction disc
assemblies 102 and 106 are typically splined to transmission input shaft 28 and
comprise the driven portion 62 of the clutch.
[0041 ] Portion 20A of clutch 20 may be substantially, structurally, and functionally
identical to existing dual plate clutches. The bell housing assembly includes four
flyweights 110, which are pivoted to the housing assembly at pivot pins 112. Return
springs 114 bias the flyweights 110 radially inwardly to rest on stops 116 (see Fig. 6A).
A stop member 118 limits the radially outward movement of the flyweights (see
Fig.6B). As the engine and the housing 100 rotate, the effect of centrifugal force will
cause the flyweights 110 to move against the bias of springs 114 from the position of
Fig. 6A to the position of Fig. 6B. The flyweights 110 each carry one or more roller 120
or functionally similar wedging member, which will act between a reaction surface and a
ramp to provide an axial clamping force for engaging the master friction clutch 20. Fig.
7 is a schematic illustration of the operational members acted upon by rollers 120. The
members of the clutch 20 are shown in fragments as rotating about the rotational axis
122 of input shaft 28.
[0042] Rollers 120 are received between a substantially flat surface 124 of a
fixed reaction plate 125 and a ramped surface 126 of an axially movable ramp plate
128. Alternatively, surface 124 could be ramped and/or the wedging member could be
of a wedge configuration. Other wedging configurations, may be utilized. The reaction
plate 125 may be manually and/or automatically adjustable by an adjustment
mechanism 125A to take up wear or the like. The ramp plate acts on an axially
movable main pressure plate 130 through a preloaded spring member 132, which will
limit the axial force applied to the main pressure plate 130 by the ramp plate. Main
pressure plate 130 will apply a clamping force CF on the friction pads 134 of the friction
plates which are trapped between surface 130A of the main pressure plate 130 and the
intermediate pressure plate 104 and the intermediate pressure plate 104 and surface
136A of the engine flywheel 136.
The hub portions 140 and 142 of the friction plates 102 and 106, respectively, are
adapted to be splined to input shaft 28 for rotation therewith while plates 125, 128, 130,
and 140 rotate with the engine flywheel 136.
[0043] At rest, one of the rollers 120 will engage the recessed portion 146 of
surface 126 and will not apply a leftward axial clamping force to the friction pads. As
the roller travels sufficiently radially outwardly, and onto the ramped portion 148 of the
ramp surface 126, an increasing axial clamping force is applied (see line 70 on Fig. 2).
As the roller moves further radially outwardly onto the flat extended portion of 150 of
surface 126, the clamp force will remain at a capped value (see lines 74 and 76 of Fig.
2) as limited by preload spring 132. The flyweights 110 will hit stops 118 prior to full
compression of springs 132. Applying force through a spring to limit the maximum force
applied is known in the prior art as may be seen by reference to U.S. Pat No.
5,901,823.
[0044] A greater centrifugal force 152 is required to move rollers 120 up ramp
portion 148 to flat portion 150 than is required to retain the rollers on the flat portion
against the effect of spring force 154 from return springs 114. This accounts for the
difference between the initial maximum clamp force engine RPM value, point 72 on Fig.
2, and the release engine RPM value, point 78 on Fig. 2. Back tapers and/or recesses
may be added to surface 150 and/or the inclination of ramp 148 and/or flat portion 150,
the relative masses and/or the spring rate of spring 114 may be modified to change the
engine speed of disengagement, point 78 on Fig. 2.
[0045] As is known, to launch a heavy duty vehicle, which will occur in a start
ratio (i.e., at a relatively high ratio of input shaft speed to output shaft speed), less
torque at the input shaft is required (for example, 600 to 900 lbs. ft., depending on
grade) than to move the vehicle at high speeds. Typical heavy-duty vehicle diesel
engines will have a maximum torque output of about 1400 to 2200 Ibs-ft. at a maximum
torque RPM.
[0046] For one embodiment of master friction clutch 20, 1000 Ibs-ft of clamp
force will provide a torque capacity of about 600 to 700 Ibs-ft., while 4000 lbs. of clamp
force will provide a torque capacity of about 3000 Ibs-ft., which is well in excess of
engine torque capacity and driveline capacity and provides a large margin of safety
when the clutch is in the capped clamp load condition, lines 74 and 76 of Fig. 2.
[0047] At vehicle launch, i.e., when starting the vehicle from stop, the clutch 20
should lock up at between about 750 RPM and 950 RPM, depending if starting up a
steep grade or in other high resistance conditions . In the vehicle launch mode i.e.,
when vehicle is stopped or at very low vehicle speed, clutch not fully engaged and start
ratio engaged (Rev, 1st, 2nd, 3rd or 4th in a 10 forward speed transmission), the control
logic of the present invention will operate in a launch mode.
[0048] In the launch mode, the transition from disengagement to engagement of
the centrifugal master clutch is dependent upon increasing engine speed. Without an
engine speed controlling algorithm, the system is prone to abuse and harsh
engagements by careless drivers since a rapid increase in engine speed is equivalent
to "dumping" or "popping" the clutch in a conventional manual clutch arrangement. In
the preferred embodiment of the present invention, by using the SAE J1939
communication link, the control algorithm uses the "speed and torque limit" mode to
control engine speed and rate of change of engine speed during engagement. Once
engagement is sensed, (by monitoring the decreasing difference between engine speed
and input shaft speed), the algorithm switches to a controlled ramp up of requested
engine torque limit starting from existing engine torque at the point of full engagement.
Once the torque has exceeded driver demand, full throttle control is returned to the
driver. Figs. 8A and 8B are a flow chart illustration of a preferred embodiment of the
launch control of the present invention.
[0049] The centrifugal clutch 20 is designed to fully engage at an approximate
engine RPM, (ex: 900RPM). The algorithm uses a throttle position modulated engine
speed limit, (ex: 750RPM to 950RPM), to control the engine speed during engagement.
As an example, see Fig. 3, at 50% throttle position the engine speed would be limited
to 850RPM until engagement was sensed. At the point of engagement the actual
engine torque value is captured and used as the starting point of the throttle "recovery
phase". The J1939 "speed and torque limit" mode is used to ramp the torque limit up
from the starting torque point to a final value. Torque will be ramped up at a rate, which
may vary with throttle position and/or engaged gear ratio. The ramp up rate will
preferably be selected to minimize driveline oscillations and avoid the natural
frequencies of the driveline.
[0050] Since a centrifugal clutch provides increasing clutching force, (torque) with
increasing rotational speed of the clutch, the algorithm uses the throttle pedal setting to
maintain a desired engine speed limit which translates into a desired torque in the
driveline. Figure 3 illustrates a graph of target engine speeds for throttle pedal
positions. By way of example, if the throttle is moved from a zero percent displacement
to a fifty percent displacement, the engine will be commanded to quickly ramp from idle
(about 600-650RPM) to 750RPM, which is the point of clutch incipient engagement,
and then increase to 850RPM in a slower modulated manner. Testing has shown that
a quick ramp rate of about 500RPM/SEC and a modulated ramp rate of about
200RPM/SEC provide satisfactory results. A performance set of ramps, if the driver
applies full (100%) throttle, may be utilized, such as, for example, 750RPM/SEC to
incipient engagement engine speed and then 250RPM/SEC to target speed.
[0051] As used herein, an engine speed may be commanded directly by
commanding a specific engine speed, indirectly by commanding an engine speed limit,
or by commanding a related parameter such as an engine torque or engine torque limit.
[0052] For decreasing throttle position, engine speed is commanded to
immediately equal the lower target value. As engine is fueled to the launch target value
engine speed (such as 850RPM at 50% throttle), and maintained at that value, while
engine speed (ES) is compared to transmission input shaft speed (IS), to sense clutch
slip (ES-IS). When clutch engagement without slip is sensed (ES-IS
to about+50RPM), the engine will be commanded to ramp up to torque value
corresponding to throttle pedal position and then control of fueling is returned to the
operator. The ramp rates may be modified as a function of the start ratio being utilized,
with quicker rates at higher start ratios (3rd or 4th) than at lower start ratios (1st or 2nd).
Throttle recovery logic, the logic by which fuel control is returned to the operator may be
seen by reference to U.S. Patent No"s: 4,493,228 and 4,792,901, the disclosures of
which are incorporated herein by reference.
[0053] The engine speed target (EST) need not be a linear function of throttle
position and may vary with sensed system parameters such as, for example, start ratio;
see line 82 in Fig. 3. The relationship may also be varied in response to sensed clutch
wear, performance degradation or the like.
[0054] The engine controls of the present invention may also be subject to
engine and/or driveline torque limitations of the types seen in U.S. Patent No"s:
5,797,110; 6,052,638 and; 6,080,082, the disclosures of which are incorporated herein
by reference.
[0055] The control will, preferably, include overheating protection, which can
occur from constant slipping of the clutch under torque (i.e., driver trying to maintain a
stopped position on a grade by slipping the clutch). This can be sensed in several
ways, such as, for example, sensing if vehicle acceleration is less than a reference
value ((dos/dt)
are incorporated herein by reference.
[0056] Upon sensing a potential clutch over-heating problem, the control logic
can react by increasing or decreasing engine RPM. If engine RPM is increased, the
clutch will engage causing the operator to use a different method of maintaining vehicle
position. If the engine speed is decreased, the driver will increase throttle position,
which should cause increased engine speed and clutch lockup. To reduce the
likelihood of using a slipping clutch to maintain a stopped position on a grade, the
system could incorporate a hill hold device 160. The hill hold device would be
controlled by ECU 50 and applied when the clutch was disengaged and the indicated
vehicle speed was zero. The hill hold would be released when the throttle was applied
and generated torque reached a predetermined level. Such hill holding devices may,
by way of example, be a separate brake or retarding device or may utilize the vehicle
foundation brakes.
[0057] In an alternate embodiment, a quick release 200 mechanism may be
provided. This mechanism may be desirable in situations where upshifting on a severe
grade (greater than 15% or 20%) may be required. Other severe operating conditions,
such as heavy loading or the like may necessitate the use of the disconnect device 200.
The quick release 200 mechanism is operated by commands from ECU 50 and may
include a positive or a friction clutch device.
[0058] Accordingly, it may be seen that a new and improved transmission system
and centrifugal master friction clutch therefor, is provided.
[0059] Although the present invention has been described with a certain degree
of particularity, it is understood that the description of the preferred embodiment is by
way of example only and that numerous changes to form and detail are possible
without departing from the spirit and scope of the invention as hereinafter claimed.
WE CLAIM:
1. A vehicular automated transmission system (10)
comprising an internal combustion engine (18) having an
engine output member (136), an engine controller (38)
having at least one mode of operation for controlling
engine fueling to control at least one of engine speed (ES)
and engine torque (ET), a multiple speed change gear
transmission (14) having an input shaft (28), a master
friction clutch (20) for drivingly connecting said engine
output member to said input shaft, a manually operated
throttle (37) for manually requesting a degree of engine
fueling, a system controller (50) for receiving input
signals (54) having tvo or more of signals indicative of
(i) engine speed (ES), (ii) throttle position (thl), (iii)
engaged transmission ratio (GR), (iv) input shaft
speed(IS), (v) vehicle speed (OS) and (vi) engine torque
(ET), and processing said signals according to logic rules
to issue command output signals (56) to system actuators
including at least said engine controller, said system
characterized by :
said master friction clutch (20) being a cantrifugally
operated clutch;
said system controller, in at least one mode of operation,
issuing command, signals to said engine controller to
control at least one of (i) engine speed and (ii) engine
torque as a function of determined values of two or more of
(i) throttle position, (ii) engine speed, (iii) engine
torque and (iv) input shaft speed;
said engine controller and said system controller
communicating over an electronic data link (dl);
said system controller with logic rules for sensing vehicle
launch conditions and said mode of operation is a vehicle
launch mode of operation; and
said system controller issuing command signals to a shift
actuator to cause shifting of said transmission, said
controller causing upshifts only if an estimated engine
speed at completion of an upshift into a target ratio
(ES=OS*GRT) exceeds a minimum reference value (ES>ESMin) ,
said clutch has a driving member (60) rotatable with said
engine output member and a driven member (62) rotatable
with "said input shaft, said clutch having a degree of
engagement dependent upon the rotational speed of said
driving member, said clutch being disengaged at engine idle
speed, said clutch becoming incipiently engaged at an
incipient engagement engine speed (ESIE) greater than said
engine idle speed (ESIE>ESIDLE), said clutch achieving a
maximum engagement (74/76) at least a lockup engine speed
(ESLOckup), said lockup engine speed greater than said
incipient engagement engine speed (ESLOCKUP>ESiE), said clutch
remaining at said maximum engagement at a disengagement
engine speed (ESdiSENGACE) less than said lockup engine speed
and less than said minimum expected engine speed (ESMIM)
expected after an upshift (ESLOCKUP>ESdiSENGACE ) and
ESMIM>ESdiSENGACE).
2.The transmission system as claimed in claim 1, wherein
said system controller issues commands for transmission
down shifts at an engine speed no less than a minimum
downshift value (ESDEMIM), said lockup engine speed greater
than said minimum downshift value (ESMDI»>ESDEMIM) .
3.A vehicular automated transmission system comprising an
electronically controlled internal combustion engine having
an engine output member, an engine controller having at
least one mode of operation for controlling engine fueling
to control at least one of engine speed and engine torque,
a multiple speed mechanical change gear transmission having
an input shaft, a master friction clutch for drivingly
connecting said engine output member to said input shaft, a
manually operated throttle for manually requesting a degree
of engine fueling, a system controller for receiving input
signals having two or more of signals indicative of (i)
engine speed, (ii) throttle position, (iii)engaged
transmission ratio, (iv) input shaft speed, (v) vehicle
speed and (vi) engine torque, and processing said signals
according to logic rules to issue command output signals to
system actuators including at least said engine controller,
said system characterized by :
said master friction clutch being a centrifugally operated
clutch;
said system controller having at least one mode of
operation wherein command signals are issued to said engine
controller to control engine speed as a function of sensed
engine speed; and
said system controller issuing command signals to a shift
actuator to cause shifting of said transmission, said
controller causing upshifts only if an estimated engine
speed at completion of an upshift into a target ratio
(ES=OS*GRf) exceeds a minimum reference value (ES>ESmiN) ,
said clutch has a driving member rotatable with said engine
output member and a driven member rotatable with said input
shaft, said clutch having a degree of engagement dependent
upon the rotational speed of said driving member, said
clutch being disengaged at engine idle speed, said clutch
becoming incipiently engaged at an incipient engagement
engine speed (ESIE) greater than said engine idle speed
(ESIE>ESIDLE), said clutch achieving a maximum engagement
(74/76) at least a lockup engine speed (ESLOCRUP) , said
lockup engine speed greater than said incipient engagement
angina speed (ESLOCRUP>ESIE), said clutch ramaining at said
maximum angagamant at a disangagamant angina spaad
(ESDISENGAGE) less than said lockup angina spaad and less than
said minimum expected engine speed (ESMIN)expected after an
upshift (ESlockup>ESDISENGAGE and ESMIN>ESDISENGAGE).
4.The transmission system as claimad in claim 3, wherein
said system controller issues commands for transmission
downshifts at an engine speed no less than a minimum
downshift value (ESDEMIN), said lockup engine speed greater
than said minimum downshift value (ESmIN>ESDEMIN) .
A vehicular transmission system (10) including a centrifugally operated
master friction clutch (20) for drivingly coupling an engine (18) to an input shaft (28)
of a mechanical transmission (12). Closed loop engine speed (ES) control is utilized
to control engagement of the clutch during vehicle launch conditions. |