GB2389922A

GB2389922A - Vehicle engine control by determining torque-converter speed ratio

Info

Publication number: GB2389922A
Application number: GB0321550A
Authority: GB
Inventors: Allan Joseph Kotwicki; John David Russell
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 1999-10-12
Filing date: 2000-09-28
Publication date: 2003-12-24
Anticipated expiration: 2020-09-28
Also published as: GB0321550D0; GB2389922B

Abstract

A vehicle-control method for a vehicle having an internal-combustion engine coupled to a torque converter which is coupled to a transmission. A speed ratio for the torque convener is determined, i.e. the ratio of torque-converter-output speed to torque-convener-output speed. If it is determined that the speed ratio is within a predetermined range, then an operating parameter of the engine (e.g. throttle position, fuel-injection amount) is adjusted to control a change in an engine output (e.g. engine output or engine torque) to be less than a preselected value. Alternatively, an engine-operating parameter may be controlled at a preselected rate. By controlling an operating parameter of the engine in these ways it is possible to pass gently through the transmission lash zone, thereby improving driver comfort.

Description

GB 2389922 A continuation (72) Inventor(s): Allan Joseph Kotwickl John

David Russell (74) Agent and/or Address for Service: A Messulam & Co. Ltd 43-45 High Road, Bushey Heath, BUSHEY, Herts, WD23 1 EE, United Kingdom

VEHICLE AND ENGINE CONTROL SYSTEM AND METROD

The present invention relates to a system and method to control an eternal combustion engine coupled to a torque 5 converte- and in particular to adjusting eng ne output to Improve drive feel.

Internal combustion engines must be controlled in many different ways to provide acceptable driving comfort during all operating conditions. Some methods use engine output, JO or torque, control where the actual engine torque is controlled to a desired engine torque through an output adjusting device, such as with an electronic throttle, ignition timing, or various other devices. In some cases, such as during normal driving conditions, the desired engine 5 torque is calculated from the amount of depression of an accelerator pedal. In other conditions, such as idle speed control, the desired engine torque is calculated based on a speed error between actual engine speed and a desired engine speed. Some attempts have been made to use this torque 20 control architecture to improve driveability during deceleration conditions, such as when a driver releases their foot to the minimum accelerator pedal position, known to those skilled in the art as a tip-out. During a tip-out, the driver is indicating a desire for reduced engine output.

2s One system that attempts to use speed control during deceleration conditions operates the engine in such a way as to maintain constant engine speed during slow moving or stopped conditions. In this system, the engine is controlled to a constant speed taking into account the 30 loading from the torque converter. The loading from the torque converter is calculated based on the engine speed and turbine speed. Engine speed can be controlled to a constant level during deceleration to adsorb energy from the vehicle and assists in vehicle braking. Further, as turbine speed as increases, the desired engine speed is reduced to provide even more engine braking. Such a system is described in DE 4321413A1.

- - The inventors herein have recogr.ised a d sad-v-anage with the above approach. In part cular, when tr.e accelerator pedal is released and subsequently engaged, the prior art system exh bits poor dr veanilit' due trar.smlssicn

s gears lash. Fo, example, when the eng ne bans Lions from exerting a positive torque to exerting a negative tcrg'e (or being driven), the gears in the transmission separate at the zero torque transition point. Then, after passing through the zero torque point, the gears again make contact to transfer torque. This series of events produces an impact, or clunk, resulting in poor driveability and customer dissatisfaction. In other words, the engine firs. exerts a positive torque through the torque converter onto the transmission input gears to drive the vehicle. Then, when using the prior art approach during deceleration, the engine

is driven by the torque from the transmission through the torque converter. The transition between. these to modes is the point where the engine is producing exactly zero engine brake torque. Then, at this transition point, the gears in 20 the transmission separate because of inevitable transmission gear lash. When the gears again make contact, they do so dynamically resulting in an. undesirable impact.

This disadvantage of the prior art is e.<acerbated when

the operator returns the accelerator pedal.o a depressed 2; position, indicating a desire for increased engine torque.

In this situation, the zero torque transition point must again be traversed. However, in this situation, the engine is producing a larger amount of torque than during deceleration because the driver is requesting acceleration.

30 Thus, another, more severe, impact is experienced due to the transmission lash during the zero torque transition.

According to our co-pending Patent Application No. GB 0023762.8 there is provided a method for estimating when a vehicle is near a transmission lash zone, the vehicle having 35 an internal combustion engine coupled to a transmission via a torque converter having a speed ratio from torque converter output speed to torque converter input speed, the

- 3 - method compris ng the steps of: ind cat r.g wren the speed ratio is w_tn_n a predetermined range; and d-terr..lr.i rig that the vehicle is near the trans. ssion lash zar.e in response to said indicat on.

5 A m etnod embodying the' ir.ver.ticn determines when tre vehicle is operating n or r.ea the trans.m,issicn lash zone.

An advantage of that ir.ven.lon is that it is possible to make other engine control features aware that the vehicle is operating in a region where transmission gear separation lo may occur. Thus, other engine control fee ures can take action to minimise effects of transmission gear separation.

Further the invention provides an engine output control system for easing transitions through the transmission lash zone. 5 According to the present invention there is provided a vehicle control method for a vehicle having an ir.te-nal combustion engine coupled to a torque converter, the torque converter having a speed ratio from torque converter output speed to torque converter input speed, the torque converter 20 coupled to a transmission, the method comprising the steps of: indicating when the speed ratio is within a predetermined range; and in response to said indication, adjusting an operating parameter to control a change in an engine output to be less than a preselected value.

25 By using signals e' reedy available it is possible to provide a realtime estimate of the transmission lash zone, or zero torque point. With this information, it is then possible to transition through the transmission lash zone gently by controlling engine output so that "clunk" is 3c minimised and fuel economy and emissions are optimised. In other words, the present invention utilises the torque converter characteristics in the following way. Because these measurements are readily available, adjusting engine output according to the present invention near the 3, transmission lash zone allows much improved drive feel since the effects of gear separation are minimized. Further, by using turbine speed and engine speed, effects from road

- 4 - grade, vehicle mass, temperature, and other factors are nhe.ent2y considered without complexity o_ addition computation. An advantage c' the above aspect of t..e invention is 5 improved diveai'ity.

Another advantage of the above aspect of the nventicr.

is l.T.proved customer satisfaction.

Yet another advantage of the above aspect of the invention is improved fuel economy.

lo In yet another aspect of the present invention there is provided a control method for a vehicle having an internal combustion engine coupled to a trans.mlsslon via a torque converter having an input speed and an output speed, the method comprising the steps of: determining a speed ratio across the torque converter based on said input speed and said output speed; and controlling an engine operating parameter at a preselected rate when said speed ratio is within a predetermined range.

By controlling an operating parameter in this way, it 20 is possible to gently pass through the transmission lash zone, thereby improving driver comfort.

An advantage of the above aspect of the prese..t invention is improved drive comfort as a result of less severe transmission gear separation.

25 The present invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a vehicle illustrating various components related to the present invention; 30 Figure 2 is a block diagram of an engine in which the invention is used to advantage; Figures 3-6 are high level flowcharts of various routines for controlling the engine according to the present invention; and 35 Figures 7A, 7B are a graphs of an example of operation according to the present invention.

( - 5 - Referring to Figure 1, internal comu-stcn engine 10, further described r.erein with particular reference to Figure 2, is s:.owr. coupled to torque converter 1 via crankshaft 13. Torque converter 1' is also coup' ed to trar.sm.issor 15 5 via turbine shaft 17. Torque conve ter 11 has a bypass clutch (not sr.cwn, Milch can be engaged, disengaged, Or partial' y engaged. When the clutch is eithe- disengaged or partially engaged, the torque converter is said to be in an unlocked state. Turbine shaft 17 is also known as lo transmission input shaft. Transmission 15 comprises an electronically controlled transmission with a plurality of selectable discrete gear ratios. Transmission 15 also comprises various other gears, such as, for example, a final drive ratio (not shown). Transmission 15 is also coupled to tire 19 via axle 21. Tire 19 interfaces the vehicle (not shown) to the read 23.

Internal combustion engine 10 compr sing a plurality of cylinders, one cylinder of which is shown, in Figure 2, is controlled by electronic engine controller 12. Engine 10 20 includes combustion chamber 30 and cylinder walls 32 with Preston 36 positioned therein and connected to crankshaft 13.

Combustion chamber 30 communicates with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Exhaust gas oxygen sensor 16 is coupled 25 to exhaust manifold 48 of engine 10 upstream of catalytic converter 20.

Intake manifold 44 communicates with throttle body 64 via throttle plate 66. Throttle plate 66 is controlled by electric motor 67, which receives a signal from ETC driver 30 69. ETC driver 69 receives control signal (DC) from controller 12. Intake manifold 44 is also shown having fuel injector 68 coupled thereto for delivering fuel in proportion to the pulse width of signal (fpw) from controller 12. Fuel is delivered to fuel injector 68 by a 35 conventional fuel system (not snowman) including a fuel tank, fuel pump, and fuel rail (not shown).

6 Engine 10 further includes conventional d stributorless ignition system 88 to provide _gni=.cn spark to combustion chamber 30 via spark plug 92 in response to cor..ro'ler 12.

n the embodiment described herein, controller 12 is a conver.tiorl microcomputer including: micrcprocesso urn' ice, input/output ports 'C4, electronic memory- chip ICE, which is an electron ca7ly programmable memory n this particular example, random access memory 108, and a conventional data bus.

lo Controller 12 receives various signals from sensors coupled to engine 10, in addition to those signals previously discussed, including: measurements of inducted mass air flow (MAF) from mass air flow sensor 110 coupled to throttle body 64; engine coolant temperature (ECT) from 15 temperature sensor 112 coupled to cooling jacket 114; a measurement of throttle position (TP) from throttle position sensor 117 coupled to throttle plate 66; a measurement of transmission shaft torque, a- engine shaft torque from torque sensor 121, a measurement of turbine speed (Wt) from 20 turbine speed sensor 219, where turbine speed measures the speed Of shaft 17, and a profile ignition pickup signal (PIP) from Hall effect sensor 118 coupled to crankshaft 13 indicating an engine speed (N). Alternatively, turbine speed may be determined from vehicle speed and gear ratio.

25 Continuing with Figure 2, accelerator pedal 130 is shown communicating with the driver's foot 132. Accelerator pedal position (PP) is measured by pedal position sensor 134 and sent to controller 12.

In an alternative embodiment, where an electronically 30 controlled throttle is not used, an air bypass valve (not shown) can be installed to allow a controlled amount o. air to bypass throttle plate 62. In this alternative embodiment, the air bypass valve (not shown) receives a control signal (not shown) from controller 12.

35 Referring now to Figure 3, a routine for detecting deceleration conditions is described. First, in step 310, driver actuated pedal position (PP) is compared with

- 7 - calibratable item (2_C), which. represents the pedal positlo. at which the pedal is closed. _n an alternate embodiment, calibatable item (PP_CT) -epreser.ts the pedal pos Lion below which a time-out is Indicated.

Alternative' y, driver desired wheel torque, wh-ch -is kr.owr. to those skilled in the art to be a function of pedal position and vehicle speed, can be compared with a mirimum desired wheel torque clip below which deceleration is desired. When the answer to step 310 is YES, then in step 15 312, both engine speed (N) and turbine speed (Wt) a-e read.

In step 314, a determination is made as to whether engine speed is greater than turbine speed. When the answer to step 314 is YES, then deceleration conditions have been detected as shown in step 316.

15 Referrir.g r,ow to Figure 4, a routine for calculating a desired engine speed during dece2eaticn conditions is described. First, in step 406, a determination is made as to whether deceleration conditions have been detected. When the answer to step 406 is YES, a determination is made in 20 step 4Q8 as to whethe, the torque converter is in and unlocked state. When the answer to step 408 is YES, engine speed (N) is read and turbine speed (Wt) iS read from turbine speed sensor il9 in step 410. Then, in step 414 the engine is controlled based on a speed ratio, SR as described 2s later herein with particular reference to Figure 5. Speed ratio is determined as (SR=Wt/N) based on the turbine speed and engine speed. In other words, in this example, torque converter input speed is engine speed and torque converter output speed is turbine speed. These speed may determined 30 in various other ways, such as, for example, turbine speed can be determine from gear ratio and vehicle speed. Also note that the speed ratio may also be determined as (SRalt= N/Wt). Those skilled in the art will recognised that the present inver,tion can be suitably reduced to practice in as view of this disclosure using the speed ratio calculated in

either way.

( - 8 - Referring now to Figure S. a routine for controlling an -

engine output, engine torque in this care, is described.

First, in step 510, speed ratio limit values (SRI, SR2) are determined based on er.gir.e operating conditions. Ir a 5 preferred embodiment, these values are calculated based on vehicle speed and gear ratio using calibraticr. functions.

Mcwever, various other signals may be used. These km t values (SR2, SRI) represent the upper and lower speed ratio values between which engine torque change is limited. In lo other words, accordlog to the presen' invention, limit values (SR2, SRI) represent the upper and lower speed ratio values between which the zero torque transition, or transmission lash zone transition, occurs. -

Continuing with Figure 5, in step Sit, a desired engine -

15 torque (Tdes) is determined using methods known to those -

skilled in the art. For example, desired engine torque may be determined based on a driver command, traction control,; sidle speed control, or various other methods. Also/ desired -

engine torque can be either a desired indicated engine 20 torque, or a desired engine brake torque. Then, in step 512, a determination is made as to whether speed ratio (SR) -

is w thin limit values (SR2, SRI). When the answer to step 512 is YES, then the engine torque change is limited as now described and it is determined that the vehicle is operating 25 near the transmission lash zone, or zero torque point. In step 514, a determination is made as to nether desired engine torque change is greater than charge limit R1. In -

particular, a determination is made as to whether the absolute value of desired engine torque change is greater 30 than change limit R1. Change limit R1 is determined based on engine operating conditions such as, for example, engine speed, turbine speed, vehicle speed, gear ratio, or other variables. In a preferred embodiment, Change limit R1 is determined based on vehicle speed using a calibrated 35 function. Also in a preferred embodiment, a rate of change of desired engine torque is determined based on current

_ 9 _ desired engine torque (odes), pre-.os filtered desired engine torque (T5es) ar,d sample time (Dt) as: ATdes Odes; - Tdesf:, At t,-ti, W. er, the answe' to step 514 s YES, r. ste- 516, cu-rer.t fi tered desired eng r.e torque (Thief! Is set equal 5 to current desired engine torque (Tdesi). Otherwise, in step 518, current filtered desired engine torque (Tdesfi) is calculated based on previous filtered desired engine torque (Tdeaf.) and change limit R1 as: Tdesi = Tdesf, + R1 * At * sgn( A) The function (sgn) is known to those skilled in the art as lo the sign function, which produces a positive unity value when the pa-amete (.rdes) is positive, and a negative unity when the parameter (ATdes) At) is negative. hen, from either step 516 or 518, in step 520, actual engine torque is controlled to filtered desired 5 engine torque (Tdesfi). Those skilled in the art will recogr.ise various methods of controlling actual engine torque to a desired value, such as, for example, by adjusting throttle position, adjusting airflow, adjusting exhaust gas recirculation, adjusting ignition timing, o adjusting cam timing, or adjusting fuel injection amount.

Those skilled in the art will recognise various other methods, in view of this disclosure, for limiting an engine

output change. According to the present invention, any method can be used for limiting the engine output change 25 while in or near the transmission lash zone without departing from the spirit and scope of the invention. For example, in an alternate embodiment, engine speed change can be limited while in or near the transmission lash zone.

- 10 Tncse skilled in the art will a'so reconise -aricus other methods, in view of this disclosure, for filtering a

parameter. For example, lot.; pass filters, r.otcr filters, and var cus other Filters can be used to ' _.m_t the amount of change of a parameter. en other words, ceslred engine torque car. be low pass filtered when speed ratio (SR) is within limits (SR1,SR2).

In an alternative embodiment, an engine control parameter, such as a throttle position, may be substituted 0 for e.gine torque as described in Figure 6. Referring now to Figure 6, in step 60, speed ratio limit values (SRI, SR2) are determined based on engine operating conditions. Then, in step 611, a desired throttle position (TPdes) is determined using methods known to those skilled in the art.

IS For example, desired throttle position may be determined based on a driver command, traction control, idle speed control, or various other methods. Then, in step 612, a determination is made as to whether speed ratio (So) Is w thin limit values (SRI, SR2). When the answer to step 612 20 is YES, then the throttle position change is limited as now descr bed. En step 614, a determination is made as to whether desired throttle position change is greater than change limit R2. Change limit R2 is determined based on engine operating conditions such as, for example, engine 2 speed, turbine speed, vehicle speed, gear ratio, o. other variables. In a preferred embodiment, Change limit R2 is determined based on vehicle speed using a calibrated function. Also in a preferred embodiment, a rate of change of desired throttle position is determined based or. current 33 desired throttle position (TPdesi) and previous filtered desired throttle position (TPdesfl) as: ATPdes TPdesi - TPdesf7, At ti - tin When, the answer to step 614 is YES, in step 616, current filtered desired throttle position (TPdesfi) is set equal to current desired throttle position (TPdesi).

35 Otherwise, in step 618, current filtered desired throttle

- 11 -

position (mPdesf) Is ca'cu'ated based cr. previous filtered desired th title position (Tides.) and change limit R2 as: TPdesf, =TPdesf, + R2**sgr( p) The-., from either stem 616 or 618, in step 620, actual 5 throttle position is controlled to filtered desired throttle position (TPdesfi). Those skilled in the art will recognise various methods of controlling actual throttle position to a desired value, such as, for example, by using a controlle based on a throttle position error signal.

JO Referring now to Figures 7A and 7B, these graphs show an example of operation according to the present invention.

In this example, upper and lower limit values are set to (SR2=1.05, SR1=0. 95). Figure 7A shows desired engine torque on the vertical axis and time on the horizontal axis. The dashed line shows desired engine torque and the solid line shows the filtered desired engine torque according to the present invention. At time tl, the speed ratio reaches limit value SRI. From this point r the desired engine torque is km ted to change at a maximum rate of R1. Then, the 20 speed ratio reaches limit value SR2 at time t2 and the filtered desired engine torque again equals the desired engine torque. Figure 7B shows the corresponding transmission input shaft torque (which is equal to torque converter output shaft torque). As transmission input shaft 25 torque passes through zero torque, or the transmission lash zone, torque is changing slower than it would otherwise be, and transmission gear separation effects are minimised.

Figures 7A and 7B have shown an example of operation according to the present invention for tip-out conditions.

30 However, those skilled in the art will recognize that the present invention as described can also be used to advantage during tip-in manoeuvres, tip-out manoeuvres, or both.

In addition to the above control methods, other features can be performed. In particular, when at a speed 35 ratio of substantially one, controller '2 has determined

t t - 12 that th- engine drivetrain is producing substarit-al'y zero torque, as long as the o-'e converter is unioc.=d. Thus, -.f torque sensor 121 has a tendency to drift, it car. be re-

zeroed in response to an indication that The drivetrain is producing subsiantial'y zero torque.

This concludes the description of the Prefe_-ed

odimer.t. The reading of it by those ski" ed -a. t:^.e art would bring to mind many other alterations and modifications without departing from the spirit and scope of the is invent on. For example, if turbine speed is not measured, vehicle speed and gear ratio can be substituted without loss of function.

Claims

1, - 13 CAMS 1. A vehicle control method For z vehicle having an internal

combustion entire co pled to a torque converter, the torque ccr.verter having a speed ratio from torah= converter output speed to torque converter input speed, the torque converter coupled to a transmission, the mlethcd comprising the steps of: indicating when the speed ratio is within a 10 predetermined range; and in response to said indication, adjusting an ope ating parameter to control a change in an engine output to be less than a preselected value.

2. A method as claimed in Claim 1, wherein speed ratio

is determined by dividing the torque converter output speed by the torque converter input speed.

3. A method as claimed in Claim 1, wherein speed ratio 20 is determined by dividing the torque converts- output speed by engine speed.

4. A method as claimed in Claim 2, wherein said predetermined range is between a lower limit value and an 25 upper limit value.

5. A method as claimed in Claim 1, wherein speed ratio is determined by dividing the torque converter input speed by the torque converter output speed.

6. A method as claimed in Claim S. wherein said predetermined range is between a lower limit value and an upper limit value.

7. A method as claimed in any one of the preceding claims, wherein said preselected value is based on an engine operating condition.

8. A method as claimed in any One of the preceding claims, wherein said pedeterm_r.ed range is based on an eng ne operating cor.ditior.

9. method as claimed in Claim 8, wherein said engine operating condition is a vehicle speed.

10. A method as claimed in any one of the preceding lo claims, wherein said engine outpu' is an engine torque.

11. A method as claimed in any one of Claims 1 to 9, wherein said engine output is an engine speed.

5

12. A method as claimed in any one of the preceding claims, wherein said operating parameter is a throttle position.

13. A method as claimed in any one of Claims 1 to 11, 20 wherein said operating parameter is a fuel injection amount.

14. A control method for a vehicle having an internal combustion engine coupled to a transmission via a torque converter having an input speed and an output speed, the 5 method comprising the steps of: determining a speed ratio across the torque converter based on said input speed and said output speed; and controlling an engine operating parameter at a preselected rate when sa d speed ratio is within a 30 predetermined range.

15. A method as claimed in Claim 14, wherein said operating parameter is a throttle position.

So

16. A method as claimed in Claim 14, wherein said operating parameter is an engine lorque.

- i5

17. A method as claimed in Claim.. 15, w:nerair. sand predetermined range is between a 'owed li..-t -.-alue and an.

upper limit value, 5

18. A method as c2ai.ed n Claim it, wherein said preselected rate is cased on an operating cord Lion.

19. A method as claimed in Claim 18, wherein said controlling step further comprises controlling said lo operating parameter at said preselected rate when said speed ratio is within said predetermined range and when a driver actuated element position is less than a predetermined position. 15 20, An article of mar.uacture comprising: a computer storage medium having a computer program en coded therein for controlling a vehicle having an internal combustion engine coupled to a torque converge- , the torque converter having an input speed and an output speed, the

20 torque converter coupled to a transmission, said computer storage medium comprising: code for determining a speed ratio across the torque converter based on said input speed and said output speed; and 25 code for controlling an engine torque at a preselected rate when said speed ratio is between a lower lim-t value and an upper limit value and when the torque converter is in an unlocked state, wherein said lower limit value and said upper limit value are based on an operating parameter.

21. An article as claimed in Claim 20 further comprising code for controlling an engine torque at a preselected rate when a driver actuated element position is less than a predetermined position.

- 16 -

22. A vein-. cle control metinod sbstan' all; as hereof nbeore described with refero.nc" to the accopa?.yir.g drawings.