DE102013207856B4 - System and apparatus for controlling internal combustion engine overshoot during a transmission shift - Google Patents

Abstract

A vehicle comprising: an internal combustion engine (12); an electric machine (16); a transmission (20); andat least one controller configured to, in response to a transmission (20) shift that causes a speed of the internal combustion engine (12) to exceed a predetermined speed, to drive current to the electric machine (16) such that the speed of the internal combustion engine (12) drops.

Description

TECHNICAL AREA

The present disclosure is directed to controlling engine overshoot during a shift in a transmission.

BACKGROUND

Vehicle manufacturers are developing hybrid vehicles to meet the demand for more fuel-efficient vehicles. A configuration for a hybrid vehicle may be referred to as a modular hybrid transmission (MHT) vehicle configuration. In a so-called MHT vehicle, an electric machine is interposed between a conventional automatic multi-step transmission and an internal combustion engine. The electric machine is attached to the impeller or the input shaft of the gearbox. The internal combustion engine is selectively decoupled from the transmission with the aid of a separating clutch. The separating clutch makes it possible to drive the vehicle solely with electrical energy, in hybrid mode with the electric machine and combustion engine at the same time, or in combustion mode solely with the combustion engine.

Hybrid vehicles, for example, are in DE 10 2008 041 976 A1 and DE 696 12 917 T2 disclosed. Because hybrid vehicles are designed to use both an internal combustion engine and an electric motor to drive a vehicle transmission, most hybrid systems interact with the transmission through clutches between the power sources and the transmission. The controls of the various clutches between the sources and within the transmission have complicated the control mechanism and can reduce efficiency and ride comfort when the clutches are engaged and disengaged during powertrain adjustment.
The invention is therefore based on the object of improving driving comfort during gear changes.

SUMMARY

The object is achieved by a device according to patent claim 1. Further developments of the device are the subject matter of the dependent claims. A vehicle includes an internal combustion engine, an electric machine, a transmission, and at least one controller. The at least one controller commands an increase in current to the electric machine such that the engine speed decreases in response to a transmission shift that causes a speed of the engine to exceed a predetermined speed. The at least one controller may further command a rate of increase in current to the electric machine to regulate a rate of decrease in engine speed. In an upshift of the transmission, the predetermined speed may be greater than the product of a gear ratio of the transmission at a start of the upshift and a speed of an output shaft of the transmission. During a downshift of the transmission, the predetermined speed may be greater than the product of a gear ratio of the transmission at an end of the downshift and a speed of an output shaft of the transmission. The vehicle may further include a clutch configured to mechanically couple the engine and the electric machine.

A method of controlling an internal combustion engine includes, in response to a transmission shift that causes a speed of the internal combustion engine to exceed a predetermined speed that is greater than a target speed, commanding an increase in current to an electric machine such that the speed of the internal combustion engine increases the target speed drops. The method may further include commanding a rate of increase in current to the electric machine to control a rate of decrease in speed of the engine. In an upshift of the transmission, the target speed may be approximately equal to the product of a gear ratio of the transmission at a start of the upshift and a speed of an output shaft of the transmission. During a downshift of the transmission, the target speed may be approximately equal to the product of a gear ratio of the transmission at an end of the downshift and a speed of an output shaft of the transmission.

A vehicle includes an internal combustion engine, an electric machine, a transmission, and at least one controller. The at least one controller, in response to a transmission shift that causes an engine speed to exceed a predetermined speed that is greater than a target speed, commands an increase in current to the electric machine such that the engine speed returns to the target speed. The at least one controller may further control a rate of increase of current to the electric machine to control a rate at which the speed of the engine ramps back to the desired speed. With an upshift of the transmission, the target rotation number should be approximately equal to the product of a gear ratio of the transmission at a start of the upshift and a rotational speed of an output shaft of the transmission. During a downshift of the transmission, the target speed may be approximately equal to the product of a gear ratio of the transmission at an end of the downshift and a speed of an output shaft of the transmission. The vehicle may further include a clutch configured to mechanically couple the engine and the electric machine.

character list

• 1 Figure 12 is a block diagram of a powertrain with a modular hybrid transmission.
• 2 FIG. 12 depicts a block diagram of a control algorithm for the modular hybrid transmission of FIG 1 represent.
• 3 (a) until 3(c) Figure 12 shows a waveform of upshift overshoot control; and
• 4 (a) until 4(c) show a curve of the overshoot control during downshifting.

DETAILED DESCRIPTION

Here, embodiments of the present disclosure are described. However, it is to be understood that the disclosed embodiments are merely examples and that other implementations may take various and alternative forms. The figures are not necessarily to scale; certain features may be exaggerated or exaggerated to show details of particular components. As will be apparent to those skilled in the art, various features illustrated or described herein with reference to one of the figures may be combined with features illustrated in one or more other figures to form embodiments that are not explicitly illustrated or are described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of this disclosure might be desired for particular applications or implementations.

The torque transfer phase of a shift is the phase in which the torque capacity of the off-going holding element (clutch) is reduced while the torque capacity of the on-coming holding element (clutch) is increased. If the incoming clutch torque capacity is lower than expected during the torque transfer phase of a shift, the engine will flare. Such an overshoot occurs when the engine speed when upshifting for the gear at the beginning of the shift exceeds a certain threshold above the speed of the output shaft multiplied by the gear ratio, or when the engine speed when downshifting for the gear at the end of the shift exceeds one exceeds a certain threshold above the speed of the output shaft multiplied by the gear ratio. For the driver, this manifests itself as a disturbing overrevving of the combustion engine and reduces the perceived shift quality.

Two ways of currently treating such overshoots are to increase the on-coming clutch torque capacity or to decrease the engine torque. Modifying the torque capacity of the clutch can affect the output torque, which is noticeable to the driver. Rapid engine torque reduction requires spark control, which can adversely affect fuel economy, emissions, and other limitations. Reducing the engine torque via the throttle requires a long response time. Accordingly, a better method for controlling engine overshoot during shifting is needed.

With the Modular Hybrid Transmission (MHT) hardware, the disconnect clutch is locked during a shift event when the ICE is used to deliver torque to the powertrain. This means that the electric motor can be used to apply a load (negative torque) to the engine to reduce overshoot. The electric motor responds quickly and without the negative effects that occur when other means of reducing engine torque are used, such as spark retard.

The control strategy monitors the engine speed and detects when a threshold value is exceeded above the desired engine speed during the torque transfer phase of a shift. The desired engine speed for an upshift is the speed of the output shaft for the gear at the start of the shift multiplied by the gear ratio. The target speed of the combustion engine at a downshift is the output shaft speed multiplied by the gear ratio for the gear at the end of the shift. An overshoot fault condition of the internal combustion engine is present when the speed of the internal combustion engine during the torque transfer phase of a gear shift exceeds the target speed of the internal combustion engine plus a small threshold value. The control strategy monitors the acceleration of the combustion engine and the difference between the actual and desired speed of the combustion engine (actual/desired speed difference). The control strategy applies a negative electric motor torque to regulate the engine speed and acceleration to a desired profile, thereby matching the actual engine speed to the desired engine speed.

Adjusting the electric motor torque to the appropriate level to reduce engine overshoot can be done via feedback control. For a given electric machine, the relationship between the electric current supplied to the electric machine and the torque of the electric machine is known. Thus, the control strategy can control the current of the electric machine in such a way that a target torque of the electric machine is achieved. The feedback control reduces the difference between the actual speed of the combustion engine (actual speed) and the desired speed of the combustion engine (target speed), calculated from the transmission ratio and the speed of the output shaft. The feedback control controls the current of the electric machine and thus regulates the torque of the electric machine on the basis of the acceleration of the combustion engine and the actual/target speed difference of the combustion engine.

Another solution is to apply feed forward electric machine torque in addition to the electric machine torque applied by the feedback controller to better compensate for the excess engine torque. The relationship between electric current and motor electric torque is well known. The inertia and mass of the components accelerating at the speed of the internal combustion engine are also known. When the engine speed is ramped up, the engine torque accelerating beyond the target speed can be calculated. This excess engine torque can be used for feed-forward control by applying the appropriate electrical current to the electric motor to compensate for this excess engine torque. Any errors in determining the speed from these calculations are taken into account by the feedback control.

An exemplary electric motor control strategy may also use a simple proportional controller based on engine speed and engine acceleration during the torque transfer phase. Motor speed may be a function of engine acceleration and speed. The faster the engine accelerates, the greater the negative electric motor torque must be in order to bring the engine speed back to the desired value. Once negative engine acceleration occurs, the electric motor torque can regulate the rate at which engine speed decreases.

In one example, a vehicle includes an engine, an electric machine, a transmission, a clutch configured to mechanically couple the engine and the electric machine, and at least one controller configured to provide an increase in in response to a transmission shift that causes a speed of the internal combustion engine to exceed a predetermined threshold value, controls current supplied to the electric machine so that the speed of the internal combustion engine decreases so that overshooting of the internal combustion engine is avoided.

It will now open 1 Referring now to FIG. 1, a block diagram of an example modular hybrid transmission (MHT) system 10 for a hybrid-electric electric vehicle is presented. The MHT system 10 includes an engine 12, a disconnect clutch 14, an electric machine 16, a torque converter 18 and a transmission 20. Other configurations are of course possible. Internal combustion engine 12 has an output shaft 22 which can be coupled to or decoupled from an input shaft 24 of electric machine 16 via separating clutch 14 . The electric machine 16 has an output shaft 28 connected to the transmission 20 .

Now open 2 Reference is made to where a block diagram of a control algorithm describes the stepping method for detecting and controlling engine overshoot (an asterisk in a block means "multiplied by"). A switching process starts 40 and it is determined whether it is in the torque transmission phase of shift 42. If no, the electric motor is controlled as standard 44. If yes, the controller determines whether an upshift is in progress 46. If yes, the controller calculates the Target engine speed by multiplying gear ratio [old gear] by output shaft speed as target engine speed 48. If No, the controller calculates target engine speed by multiplying gear ratio [new gear] by output shaft speed as target engine speed 50 .

The controller then determines the engine speed in comparison to the desired engine speed plus a threshold value 52. If an engine overshoot is detected during the shifting process 54, the controller calculates the feed-forward electric motor torque using engine acceleration and inertia 56 and calculates the ) feedback electric motor torque using engine speed minus target engine speed as the error to be minimized 58. The controller then determines whether the electric motor can deliver the desired torque by checking the battery state of charge and other operating conditions of the electric motor 60. If yes, the controller uses information via electric current versus motor torque and applies the calculated feedforward and feedback motor torque 62 . If no, the controller applies as much of the feed forward and feedback torque with the electric motor as possible 64 and uses standard anti-overshoot controls to mitigate overshoot not compensated for by the electric motor.

Now reference to the 3(a) until 3(c) and 4(a) until 4(c) taken, where the 3(a) until 3(c) the upshift overshoot control and the 4(a) until 4(c) illustrate overshoot control during downshifting. The 3(a) and 4(a) show actual on-coming clutch pressure (or torque capacity), desired on-coming clutch pressure (or torque capacity), and off-going clutch pressure (or torque capacity). Desired oncoming clutch pressure (or torque capacity) is the clutch pressure (or torque capacity) required to prevent engine overshoot during the torque transfer phase of the shift. Engine torque in excess of the sum of the actual torque capacities of the on-coming and off-going clutches causes an increase in engine speed.

The 3(a) and 4(a) show that the actual engaging clutch pressure (or torque capacity) is less than the desired clutch pressure (or torque capacity). The 3(b) and 4(b) show engine speed, overshoot threshold, gear ratio multiplied by output shaft speed [old gear], and gear ratio multiplied by output shaft speed [new gear]. The 3(b) and 4(b) show that when an actual on-coming clutch pressure (or torque capacity) falls below the desired on-coming clutch pressure (or torque capacity), an increase in engine speed during the torque transfer phase of the shift results. The engine speed increase continues until an overshoot detection threshold is crossed and the engine speed increase is determined to be an overshoot.

In an upshift according to the 3(a) until 3(c) the target engine speed is the output shaft speed for the gear at the start of the shift multiplied by the gear ratio. In a downshift according to the 4(a) until 4(c) is the target speed of the internal combustion engine, the output shaft speed multiplied by the gear ratio for the gear at the end of the shift. The 3(c) and 4(c) show the applied motor torque for eliminating engine overshoot and controlling engine speed and acceleration. The 3(b) and 4(b) show the application of the electric motor torque as a function of the acceleration of the internal combustion engine and also show the actual/desired speed difference of the internal combustion engine. When the combustion engine accelerates quickly, the torque of the electric motor is increased. As the actual speed of the internal combustion engine begins to decrease towards the target speed, the torque of the electric motor is reduced based on the degree of braking of the internal combustion engine and the actual/target speed difference of the internal combustion engine. The feedback control adjusts the electric motor torque to control the engine speed and acceleration to a desired profile and achieve the target engine speed. The 3(b) and 4(b) show the elimination of an overshoot of the Ver internal combustion engine after application of the electric motor torque.

The processes, methods, or algorithms disclosed herein may be delivered to/implemented by a processing device, controller, or computer, which may include any pre-existing or dedicated electronic control unit. Likewise, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms, including but not limited to: as permanently stored information on non-writable storage media such as read-only (ROM) devices; and as alterably stored information on writable storage media such as floppy disks, magnetic tape, CDs, random access (RAM) devices, and other magnetic and optical media. The processes, methods, or algorithms can also be implemented in a software executable object. Alternatively, the processes, methods or algorithms can be implemented in whole or in part using suitable hardware components such as application specific integrated circuits (ASIC), field programmable gate arrays (FPGA), state machines, controllers or other hardware components or devices or a combination of hardware, software, and firmware components.

1. A. Fahrzeug, umfassend:
   • einen Verbrennungsmotor;
   • eine elektrische Maschine;
   • ein Getriebe; und
   mindestens einen Controller, der so konfiguriert ist, dass er als Reaktion auf einen Schaltvorgang des Getriebes, durch den eine Drehzahl des Verbrennungsmotors eine vorherbestimmte Drehzahl übersteigt, eine Erhöhung des Stroms zur elektrischen Maschine so ansteuert, dass die Drehzahl des Verbrennungsmotors absinkt.
2. B. Fahrzeug nach A, wobei der mindestens eine Controller ferner so konfiguriert ist, dass er eine Anstiegsrate des Stroms zur elektrischen Maschine ansteuert, um eine Abnahmerate der Drehzahl des Verbrennungsmotors anzusteuern.
3. C. Fahrzeug nach A, wobei das Getriebe eine Abtriebswelle beinhaltet und wobei, für eine Aufwärtsschaltung des Getriebes, die vorherbestimmte Drehzahl größer ist als das Produkt aus einem Übersetzungsverhältnis des Getriebes an einem Anfang des Aufwärtsschaltvorgangs und einer Drehzahl der Abtriebswelle.
4. D. Fahrzeug nach A, wobei das Getriebe eine Abtriebswelle beinhaltet und wobei, für eine Abwärtsschaltung des Getriebes, die vorherbestimmte Drehzahl größer ist als das Produkt aus einem Übersetzungsverhältnis des Getriebes an einem Ende des Abwärtsschaltvorgangs und einer Drehzahl der Abtriebswelle.
5. E. Fahrzeug nach A, ferner umfassend eine Kupplung, die so konfiguriert ist, dass sie den Verbrennungsmotor und die elektrische Maschine mechanisch kuppelt.
6. F. Verfahren zur Steuerung eines Verbrennungsmotors eines Fahrzeugs, umfassend: als Reaktion auf einen Schaltvorgang eines Getriebes, durch den eine Drehzahl des Verbrennungsmotors eine vorherbestimmte Drehzahl übersteigt, die größer als die Solldrehzahl ist, das Ansteuern einer Erhöhung des Stroms zu einer elektrischen Maschine, so dass die Drehzahl des Verbrennungsmotors auf die Solldrehzahl absinkt.
7. G. Verfahren nach F, ferner umfassend das Ansteuern einer Anstiegsrate des Stroms zur elektrischen Maschine, um eine Abnahmerate der Drehzahl des Verbrennungsmotors anzusteuern.
8. H. Verfahren nach F, wobei, für eine Aufwärtsschaltung des Getriebes, die Solldrehzahl etwa gleich dem Produkt aus einem Übersetzungsverhältnis des Getriebes an einem Anfang des Aufwärtsschaltvorgangs und einer Drehzahl einer Abtriebswelle des Getriebes ist.
9. I. Verfahren F, wobei, für eine Abwärtsschaltung des Getriebes, die Solldrehzahl etwa gleich dem Produkt aus einem Übersetzungsverhältnis des Getriebes an einem Ende des Abwärtsschaltvorgangs und einer Drehzahl einer Abtriebswelle des Getriebes ist.
10. J. Fahrzeug, umfassend:
    • einen Verbrennungsmotor;
    • eine elektrische Maschine;
    • ein Getriebe; und
    mindestens einen Controller, der so konfiguriert ist, dass er als Reaktion auf einen Getriebeschaltvorgang, durch den eine Drehzahl des Verbrennungsmotors eine vorherbestimmte Drehzahl übersteigt, die größer als die Solldrehzahl ist, eine Erhöhung des Stroms zur elektrischen Maschine ansteuert, so dass die Drehzahl des Verbrennungsmotors auf die Solldrehzahl zurückgeht.
11. K. Fahrzeug nach J, wobei der mindestens eine Controller ferner so konfiguriert ist, dass er eine Anstiegsrate des Stroms zur elektrischen Maschine ansteuert, um eine Rate anzusteuern, mit der die Drehzahl des Verbrennungsmotors auf die Solldrehzahl zurückgeht.
12. L. Fahrzeug nach J, wobei das Getriebe eine Abtriebswelle beinhaltet und wobei, für eine Aufwärtsschaltung des Getriebes, die Solldrehzahl etwa gleich dem Produkt aus einem Übersetzungsverhältnis des Getriebes an einem Anfang des Aufwärtsschaltvorgangs und einer Drehzahl der Abtriebswelle ist.
13. M. Fahrzeug nach J, wobei das Getriebe eine Abtriebswelle beinhaltet und wobei, für eine Abwärtsschaltung des Getriebes, die Solldrehzahl etwa gleich dem Produkt aus einem Übersetzungsverhältnis des Getriebes an einem Ende des Abwärtsschaltvorgangs und einer Drehzahl der Abtriebswelle ist.
14. N. Fahrzeug nach J, ferner umfassend eine Kupplung, die so konfiguriert ist, dass sie den Verbrennungsmotor und die elektrische Maschine mechanisch kuppelt.

It is generally described:

1. A. Vehicle comprising:
   • an internal combustion engine;
   • an electric machine;
   • a gearbox; and
   at least one controller configured to command an increase in current to the electric machine to decrease the speed of the engine in response to a transmission shift that causes a speed of the engine to exceed a predetermined speed.
2. B. The vehicle of A, wherein the at least one controller is further configured to command a rate of increase in current to the electric machine to command a rate of decrease in speed of the engine.
3. C. The vehicle of A, wherein the transmission includes an output shaft and wherein, for an upshift of the transmission, the predetermined speed is greater than the product of a gear ratio of the transmission at a start of the upshift and a speed of the output shaft.
4. D. The vehicle of A, wherein the transmission includes an output shaft and wherein, for a transmission downshift, the predetermined speed is greater than the product of a gear ratio of the transmission at an end of the downshift and a speed of the output shaft.
5. E. The vehicle of A, further comprising a clutch configured to mechanically couple the engine and the electric machine.
6. F. A method of controlling an internal combustion engine of a vehicle, comprising: in response to a transmission shift that causes a speed of the internal combustion engine to exceed a predetermined speed that is greater than the target speed, commanding an increase in current to an electric machine, so that the speed of the internal combustion engine drops to the target speed.
7. G. The method of F, further comprising commanding a rate of increase in current to the electric machine to command a rate of decrease in speed of the engine.
8. H. The method of F wherein, for an upshift of the transmission, the target speed is approximately equal to the product of a gear ratio of the transmission at a start of the upshift and a speed of an output shaft of the transmission.
9. I. Method F wherein, for a transmission downshift, the target speed is approximately equal to the product of a gear ratio of the transmission at an end of the downshift and a speed of an output shaft of the transmission.
10. J. Vehicle comprising:
    • an internal combustion engine;
    • an electric machine;
    • a gearbox; and
    at least one controller configured to command an increase in current to the electric machine such that the speed of the engine increases in response to a transmission shift that causes a speed of the engine to exceed a predetermined speed that is greater than the target speed returns to the target speed.
11. K. The vehicle of J, wherein the at least one controller is further configured to command a rate of increase in current to the electric machine to command a rate at which the engine speed ramps back to the desired speed.
12. L. The vehicle of J wherein the transmission includes an output shaft and wherein, for an upshift of the transmission, the target speed is approximately equal to the product of a gear ratio of the transmission at a start of the upshift and a speed of the output shaft.
13. M. The vehicle of J wherein the transmission includes an output shaft and wherein, for a transmission downshift, the target speed is approximately equal to the product of a gear ratio of the transmission at an end of the downshift and a speed of the output shaft.
14. N. The vehicle of J, further comprising a clutch configured to mechanically couple the engine and the electric machine.

Claims (5)

Vehicle comprising: an internal combustion engine (12); an electrical machine (16); a gearbox (20); and at least one controller configured to, in response to a shift of the transmission (20) causing a speed of the internal combustion engine (12) to exceed a predetermined speed, control the current of the electric machine (16) such that the speed of the internal combustion engine (12) drops. vehicle after claim 1 wherein the at least one controller is further configured to command a rate of increase in current of the electric machine (16) to regulate a rate of decrease in speed of the internal combustion engine (12). vehicle after claim 1 wherein the transmission (20) includes an output shaft and wherein, for an upshift of the transmission (20), the predetermined speed is greater than the product of a gear ratio of the transmission (20) at a start of the upshift and a speed of the output shaft. vehicle after claim 1 wherein the transmission (20) includes an output shaft and wherein, for a downshift of the transmission (20), the predetermined speed is greater than the product of a gear ratio of the transmission (20) at an end of the downshift and a speed of the output shaft. vehicle after claim 1 , further comprising a clutch (14) configured to mechanically couple the internal combustion engine (12) and the electric machine (16).

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