WO2012121657A1

WO2012121657A1 - Method and device for control of pumping work of a combustion engine

Info

Publication number: WO2012121657A1
Application number: PCT/SE2012/050260
Authority: WO
Inventors: Peter Juhlin-Dannfelt; Peter Larsson
Original assignee: Scania Cv Ab
Priority date: 2011-03-10
Filing date: 2012-03-08
Publication date: 2012-09-13
Also published as: SE1150210A1

Abstract

The present invention relates to a method for control of pumping work of a combustion engine (10) to lower a speed ω of the engine (10), which engine has an intake pipe (2) and an exhaust pipe (22) connected to it, the engine's pumping work being increased or decreased by regulation of a gas pressure in the intake pipe (2). The invention further relates to a device for control of pumping work of a combustion engine, a computer programme, a computer programme product and a motor vehicle provided with such a device.

Description

METHOD AND DEVICE FOR CONTROL OF PUMPING WORK

OF A COMBUSTION ENGINE

Technical field

The present invention relates to a method for control of pumping work of a combustion engine. The invention relates in particular to a method according to the preamble of claim 1. The invention further relates to a device for control of pumping work of a combustion engine, a computer programme, a computer programme product and a motor vehicle provided with such a device.

Background to the invention

At an upshift from a first gear G, to a higher second gear G₂ in a gearchange system, it is desirable that a prevailing engine speed ω be lowered quickly and in a controlled way when the gearbox is in neutral position between the first gear G, and the second gear G₂ .

Figure 1 depicts a situation where an upshift takes place from the lower first gear G, to the higher second gear G₂ (in this case from gear 10 to gear 12) and in this example it is assumed that the driver keeps the accelerator pedal depressed throughout the upshift. The upshift takes place as follows:

1) The upshift is initiated either manually or automatically depending on the gearchange system, while at the same time the engine's torque is reduced so that there is no engine torque in the gearbox;

2) The first gear G, is then disengaged, putting the gearbox into neutral position (N);

3) When the gearbox is in neutral position, a current engine speed ω is controlled so that it matches (synchronises) the engine speed for the second gear G₂ , whereupon the clutch closes;

4) When the current engine speed ty has been synchronised, the second gear G₂ is engaged; and

5) The engine torque may then be increased to a desired level.

The third step above is the stage at which it is desirable that the engine speed should drop quickly from a first speed ω_λ to a lower second speed co₂ so that an upshift can be effected quickly. One of the advantages of lowering the engine speed ω quickly is that it results in a shorter interruption of driving torque and hence in the vehicle not losing so much speed during the upshift. A lowering of engine speed is usually achieved by the engine system ceasing to inject fuel into the engine, with the result that the engine's internal friction and pumping work retard the engine so that its speed ω is lowered.

A combustion engine's pumping work, also called pumping losses, is work required to pump air into the engine's cylinder/cylinders before combustion and to pump burnt gas out from the cylinder/cylinders after combustion. This means that more pumping work leads to quicker lowering of the engine speed ω , and less pumping work leads to slower lowering of the engine speed ω , in situations where all other circumstances are the same. Controlling the pumping work in heavy vehicles such as trucks and buses involves usually the use of an exhaust damper situated in an exhaust pipe through which exhaust gases are discharged. The exhaust damper closes, leading to build-up of a high exhaust backpressure which results in increased pumping work of the engine. Alternatively to or in combination with an exhaust damper it is also possible to use a variable turbo, also known as VGT (variable geometry turbocharger), to limit the cross-sectional area for flow of exhaust discharges and thereby increase the pumping work. The VGT may for example control the amount of exhaust flow reaching the turbine blades.

In certain situations the pumping work achieved by exhaust damper and/or VGT is not sufficient when a very quick engine speed lowering is desirable. Moreover, not all engine systems/motor vehicles have an exhaust damper or VGT, which means that in such systems/vehicles the engine's pumping work cannot be controlled at all.

Brief description of the invention

An object of the present invention is to propose a method and device which wholly or partly solve the disadvantages and problems of prior art methods and devices. Another object of the invention is to propose an alternative method and alternative device for control of pumping work of a combustion engine. A further object of the invention is to propose a method and device by which the speed of a combustion engine can be lowered quickly and/or in a controlled way. According to an aspect of the invention, the above objects are achieved with a method for control of pumping work of a combustion engine in order to lower a speed ω of the engine, the engine having an intake pipe and an exhaust pipe connected to it and its pumping work being increased or decreased by regulation of a gas pressure in the intake pipe. Various embodiments of the above method are defined in the claims which are subordinate to claim 1.

The method according to the invention may also be implemented in a computer programme which, when executed in a computer, causes the computer to apply a method as above.

According to another aspect of the invention, the above objects are achieved with a device for control of pumping work of a combustion engine in order to lower a speed ω of the engine, the engine having an intake pipe and an exhaust pipe connected to it and the device comprising at least one first means by which a gas pressure in the intake pipe is arranged to be regulated so that the engine's pumping work increases or decreases.

Various embodiments of the above device are defined in the claims which are subordinate to claim 1 1. The invention further relates to a motor vehicle provided with at least one device as above. The device may however also form part of an engine system intended for example for marine or industrial use.

A method and device according to the present invention result in quicker lowering of the engine speed than prior art methods and devices. They also make it possible for the rate of lowering of the engine speed to be controlled on the basis of how the gas pressure in the intake pipe is controlled. In a gearchange application this leads to quicker and more controlled gear changes and may thus improve a motor vehicle's comfort and performance by achieving quicker upshifts which involve less loss of vehicle speed.

The invention also means that a combustion engine's pumping work can also be controlled in engine systems/motor vehicles which have no exhaust damper or VGT.

Further advantages and applications of the invention will emerge from the detailed description set out below. Brief description of drawings

The present invention is described with reference to the attached drawings, in which:

Figure 1 depicts schematically a gear upshift;

Figure 2 depicts schematically a gas flow in a combustion engine system;

Figure 3 depicts schematically a throttle damper situated in an intake pipe connected to a combustion engine (the engine is not depicted but is represented by the region between the broken lines) via a manifold, and an exhaust damper situated in an exhaust pipe;

Figure 4 depicts schematically a control unit for control of an embodiment of a device according to the invention; and

- Figure 5 is a flowchart of an embodiment of the invention.

Detailed description of the invention

With a view to achieving the above objects, the present invention relates to a method for control of pumping work of a combustion engine 10 in order thereby to lower a speed ω of the engine. An intake pipe 2 and an exhaust pipe 22 are connected to the engine and its pumping work is increased or decreased by regulation of a gas pressure in the intake pipe 2.

As described above, prior art control of a combustion engine's pumping work, particularly in heavy motor vehicles, has previously been by regulating the backpressure in the exhaust pipe ("the exhaust side"), e.g. by using an exhaust damper and/or a VGT. Part of the inventive work has been the inventors' insight that the combustion engine's pumping work can be controlled by regulating the gas pressure in the intake pipe, which is equivalent to the gas pressure on the engine's "inlet side" being regulated to control the pumping work. Inlet side means the "side" of the engine system where air flows into its cylinder/cylinders. Similarly, a combustion engine's exhaust side is the side of the engine system where burnt gas is discharged from the cylinder/cylinders. The inventors have gained the insight that there is a relationship between the gas pressure in the intake pipe P_ln and the gas pressure in the exhaust pipe P_0ul . This insight is that the engine's pumping work is proportional to (or depends on) the pressure difference P_Dlff between the gas pressure in the intake pipe P_ln and the gas pressure in the exhaust pipe P_0ul , i.e. proportional to P_Diff = P_()ul - P_!n . According to the invention, a way of increasing this pressure difference P_Diff and hence the pumping work may therefore be by lowering the gas pressure in the intake pipe (the inlet side). This means that the pumping work can also be controlled in combustion engine systems and/or motor vehicles which have no throttle damper or VGT installed. With the object of more clearly explaining the invention, Figure 2 depicts schematically a gas flow in a combustion engine system for a heavy motor vehicle, which system comprises in this example a diesel engine 10 with turbo, and a number of pipes connected to the engine. Air is drawn in from the left in Figure 2 through an intake pipe and is compressed in a turbocharger 200 in order thereafter to be cooled in a charge air cooler 201 before passing a throttle damper 1 which regulates the amount of air entering the diesel engine.

After the throttle damper 1 the air is mixed with returned exhaust gases, so-called EGR (exhaust gas recirculation), and the resulting mixture is then drawn into the engine's cylinders in order to be mixed there with suitable fuel, e.g. diesel fuel, before combustion takes place in the cylinders. The exhaust gases from the combustion process then pass through a turbo turbine 203 which drives the turbocharger 200. Part of the exhaust gases enters an EGR pipe and is led back to the intake pipe via an EGR damper and an EGR cooler. The function of the EGR damper is to regulate the amount of exhaust gases returned to the combustion process, and it closes when the pumping work is to be increased. Before the exhaust gases completely leave the engine system through an exhaust pipe 22, they pass an exhaust damper 1 1 which controls the pressure in an exhaust manifold (not depicted in the diagram). The exhaust gases then pass through a post-treatment system which may comprise a particle filter 204 (DPF, diesel particle filter), a so-called SCR (selective catalyst reduction) catalyst 205, a so-called DOC (diesel oxidation catalyst) or some other form of post-treatment component if the engine system has a post-treatment system.

According to an embodiment of the invention, the pumping work of the engine 10 is increased by lowering the gas pressure in the intake pipe 2, and conversely is decreased by increasing the gas pressure in the intake pipe.

According to another embodiment of the invention, the engine 10 is connected to a gearbox 20 and the engine's pumping work is increased at an upshift from a first gear G, to a higher second gear G₂ . As illustrated in Figure 1 , the upshift may take place over a period of time T during which the engine speed ω drops from a first speed ω _\ associated with the first gear [ to a second speed ω ₂ associated with the higher second gear G₂ . The first speed ω is higher than the second speed ω ₂, since what is depicted in Figure 1 is an upshift.

To further speed up the lowering of the engine speed ω , no fuel is supplied to the engine when the gas pressure in the intake pipe is being regulated to increase the engine's pumping work, according to a further embodiment of the invention.

According to a preferred embodiment of the invention, the gas pressure in the intake pipe is regulated by means of a damper 1 adapted to assuming various different positions in the intake pipe. The damper is preferably adapted to assuming various positions between a first extreme position and a second extreme position, the first extreme being a fully open position resulting in a maximum gas pressure in the intake pipe, and the second extreme a fully closed position resulting in a minimum gas pressure in the intake pipe. The concept of this embodiment is that the damper 1 is caused to assume a first position adjacent to the second extreme position for the period T of the upshift. The reason for the damper not closing completely is that too low a gas pressure in the intake pipe might lead to motor oil being drawn into the intake pipe, e.g. through the valve seals, which would result in unacceptable emissions and other disadvantages. This means that it is desirable that the damper assume a position such that the gas pressure in the intake pipe is as low as possible but not so low as to risk motor oil leakage through the valve seals.

According to an embodiment, when the damper 1 assumes the first position the gas pressure in the intake pipe is between 10 and 80% of that when the damper assumes the first extreme position. According to this embodiment, the damper is therefore directed to a first position (the damper is caused to assume a first position) resulting in the gas pressure in the intake pipe being between 10 and 80% of that when the damper assumes the first extreme position. The control of the damper is based on a representation of the gas pressure in the intake pipe. Said representation may take the form of a value for the gas pressure in the intake pipe as measured by a suitable pressure sensor. Said representation may take the form of an estimated value for the gas pressure in the intake pipe as determined on the basis of a suitable model. Said representation may take the form of a tabulated value read for the gas pressure in the intake pipe under prevailing requirements/circumstances. Said representation of the gas pressure in the intake pipe may be determined in any suitable way.

According to an embodiment, the damper 1 is directed on the basis of a representation of the gas pressure in the intake pipe to a position resulting in the gas pressure there being between 10 and 80% of that when the damper assumes the first extreme position. The gas pressure when the damper assumes the first extreme position may be determined in any suitable way, e.g. by measurement by a pressure sensor, estimation by means of a model or by tabulated values read for the gas pressure when the damper assumes the first extreme position under prevailing requirements/circumstances.

According to an embodiment, the damper 1 is controlled on the basis of a representation of the gas pressure in the intake pipe in such a way that a current/momentary/present representation of it is continuously fed back to an algorithm/control unit for control of the damper (control of the damper's position), making it possible for the damper to be controlled so that a desired gas pressure in the intake pipe is achieved. According to a further embodiment of the invention, the gas pressure when the damper 1 assumes the first position is 20-70% of that when the damper assumes the first extreme position. According to this embodiment, the damper is therefore controlled, in a similar way to that described above, to a first position which results in the gas pressure in the intake pipe being between 20 and 70% of that when the damper assumes the first extreme position.

An example of a suitable damper 1 for regulating the gas pressure in an intake pipe 2 is a throttle damper of disc type. Figure 3 depicts schematically an arrangement whereby a throttle damper 1 is situated in an intake pipe 2 to regulate the gas flow (air flow) through the pipe, and the pipe is connected to a combustion engine 10 via a manifold 21 for inlet air if the engine has more than one cylinder.

The throttle damper 1 is controlled by a control unit 1 10 by means of one or more control means 211 so that the flow through the intake pipe 2 is regulated according to desired amounts of air supply to the engine system. When the amount of air (the flow) entering the engine 10 is limited by a throttle damper 1, the gas pressure in the intake pipe 2 will be lowered, and conversely will increase if the amount of air entering the engine is increased. The engine's pumping work can thus be controlled from the inlet side. It should be noted that the gas pressure in the intake pipe may also be affected by other factors, e.g. a speed ω of the engine, a charge pressure after a turbo if a turbo is fitted, a temperature in the intake pipe, and whether any EGR damper is open. These factors also need to be taken into account in controlling the pumping work. According to a further preferred embodiment, the engine's pumping work is controlled by regulating the gas pressure in the intake pipe 2 and in the exhaust pipe 22 (the exhaust side) (see Figure 3). In this way the pressure difference P_Dlff between the intake pipe (the inlet side) and the exhaust pipe (the exhaust side) can be further controlled. The gas pressure in the exhaust pipe is preferably regulated by an exhaust damper 1 1 (also called exhaust backpressure damper or exhaust brake damper) or a GVT, the pumping work being increased by increasing the gas pressure in the exhaust pipe. This embodiment makes it possible for the engine speed ω to be lowered still more quickly and controlled still more exactly. To achieve as much pumping work as possible, the gas pressure in the intake pipe is decreased at the same time as the gas pressure in the exhaust pipe is increased, leading to the pressure difference P_Dlff increasing. A typical value for the positive pressure in the exhaust pipe at a gear upshift may be up to 5.5 bar (i.e. 6.5 bar abs.) and a conceivable value for the negative pressure in the intake pipe at an upshift might be -0.9 bar, making a pressure difference of 6.4 bar in this specific example.

Throttle dampers and other types of damper are usually controlled by one or more control means 211 (see Figure 3) which are operated pneumatically or hydraulically or possibly by electric motors if they are fitted in heavy vehicles such as trucks, buses and plant vehicles. Moreover, most throttle dampers are adapted to assuming various positions in the intake pipe at varying rates v, since their position has to conform to the engine speed ω for the throughflow of air in the engine to be appropriate to the desired combustion in the cylinders. It is desirable that the throttle damper assume its first position adjacent to the second extreme position as soon as possible to ensure that the engine speed will drop as quickly as possible on the occasion for example of a gear upshift. The throttle damper therefore needs to assume this position at a maximum rate v_Max which is the highest rate at which it can be put into its various positions.

The actual control of the control means is most commonly by a control unit 1 10, usually a so- called ECU (electronic control unit) adapted to controlling various functions in a motor vehicle. Figure 4 depicts schematically such a control unit 110 comprising a calculation unit 1 1 1 which may take the form of substantially any suitable type of processor or

microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP), or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The calculation unit 1 1 1 is connected to a memory unit 1 12 which is situated in the control unit 1 10 and which provides the calculation unit 1 1 1 with, for example, the stored programme code and/or the stored data which the calculation unit needs for it to be able to perform calculations. The calculation unit 1 11 is also arranged to store partial or final results of calculations in the memory unit 1 12. The control unit 1 10 is further provided with respective devices 1 13, 1 14, 1 15, 1 16 for receiving and sending input and output signals. These input and output signals may comprise waveforms, pulses or other attributes which the input signal receiving devices 1 13, 116 can detect as information and which can be converted to signals which the calculation unit 1 1 1 can process. These signals are then conveyed to the calculation unit. The output signal sending devices 1 14, 115 are arranged to convert signals received from the calculation unit 11 1 in order, e.g. by modulating them, to create output signals. One skilled in the art will appreciate that the aforesaid computer may take the form of the calculation unit 1 1 1 and that the aforesaid memory may take the form of the memory unit 1 12. Each of the connections to the respective devices for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN bus, an MOST (Media Orientated Systems Transport) bus or some other bus

configuration, or a wireless connection.

Figure 5 is a flowchart of an embodiment of the method according to the invention:

• At step Fl an upshift from a lower first gear G, to a higher second gear G₂ is initiated;

• At step F2 the gearbox is put into a torque-free state which means that there is no torque in the gearbox (compare with Figure 1);

• At step F3 the first gear G, is then disengaged, which take place at a first engine speed

• At step F4 the damper closes in the intake pipe, leading to negative pressure in the pipe, whereupon the engine's pumping work increases, causing the engine speed ω to drop more quickly;

• At step F5 the system waits for a current engine speed ω to drop to a desired second speed ω ₂ for the second gear G₂ ;

• At step F6 the damper opens in the intake pipe so that the pumping work decreases and the second gear G₂ is engaged; and

• At step F7 the engine torque is increased to a desired level, i.e. a torque which a driver demands, e.g. by using an accelerator pedal or cruise control.

The control of an exhaust damper and/or a VGT in the intake pipe may also be coordinated with the control of the throttle damper 1 so that the pressure difference P_Dlff will be as large as possible at the upshift, as described above. This preferably takes place at step F4 in the flowchart.

As one skilled in the art will appreciate, a method for control of a damper according to the present invention may also be implemented in a computer programme which, when executed in a computer, causes the computer to apply the method. The computer programme is contained in a computer programme product's computer-readable medium which takes the form of a suitable memory, e.g. ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable PROM), flash memory, EEPROM (electrically erasable PROM), a hard disc unit etc.

The present invention further relates to a device for control of pumping work of a combustion engine 10 in order to lower a speed ω of the engine. An intake pipe 2 and an exhaust pipe 22 are connected to the engine. The device according to the invention comprises at least one first means by which a gas pressure in the intake pipe is arranged to be regulated so that the pumping work of the engine increases or decreases.

Such a device as above may preferably be situated in a motor vehicle, e.g. a car, truck or bus, or be part of an engine system comprising a combustion engine. The engine system may be intended for marine or industrial use (e.g. standby power generation), as one skilled in the art will surely appreciate.

According to an embodiment, the engine 10 is connected to a gearbox, preferably an automatically controlled gearbox, e.g. of the automatic manual gearbox type (AMT, automatic manual transmission). The gearbox may also be of an automatic type ("automatic gearbox"). The engine may also be a piston engine, e.g. a diesel engine, gas engine, ethanol engine or petrol engine.

Further embodiments of the device according to the invention are described in the attached claims. It should also be noted that the device may be modified according to various embodiments of the method according to the invention (and vice versa) and that the present invention is in no way restricted to the embodiments described above of the method or the device according to the invention but relates to and comprises all embodiments within the protective scope of the attached independent claims.

Claims

1. A method for control of pumping work of a combustion engine (10) to lower a speed ω of the engine (10), which engine has an intake pipe (2) and an exhaust pipe (22) connected to it, characterised in that the engine's pumping work is increased or decreased by regulation of a gas pressure in the intake pipe (2).

2. A method according to claim 1 , in which the pumping work

- is increased by lowering the gas pressure in the intake pipe (2), and

- is decreased by increasing the gas pressure in the intake pipe (2).

3. A method according to claim 2, in which the engine (10) is also connected to a gearbox (20), and the pumping work

- is increased at the time of a gear upshift.

4. A method according to claim 2 or 3, in which no fuel is supplied to the engine (10) at an increase in the pumping work.

5. A method according to any one of claims 2-4, in which the gas pressure in the intake pipe (2) is regulated by a damper (1) which is adapted to assuming various different positions in the intake pipe (2).

6. A method according to claim 5, in which the damper (1) is adapted to assuming various positions between a first extreme position and a second extreme position, the first extreme being a fully open position resulting in a maximum gas pressure in the intake pipe (2), and the second extreme a fully closed position resulting in a minimum gas pressure in the intake pipe (2); and

- the damper (1) is caused to assume a first position adjacent to the second extreme position during the upshift.

7. A method according to claim 6, in which the gas pressure in the intake pipe (2) when the damper (1) assumes the first position is between 10 and 80% of the gas pressure when the damper (1) assumes the first extreme position.

8. A method according to claim 7, in which the gas pressure in the intake pipe (2) when the damper (1) assumes the first position is between 20 and 70% of the gas pressure when the damper (1) assumes the first extreme position.

9. A method according to any one of the foregoing claims, in which the pumping work is further

- increased or decreased by regulation of a gas pressure in the exhaust pipe (22) by means of a damper (1 1), e.g. an exhaust damper, or a VGT.

10. A method according to claim 9, in which the pumping work

- is increased by an increase in the gas pressure in the exhaust pipe (22).

11. A computer programme which comprises programme code and which when said programme code is executed in a computer causes said computer to apply the method according to any one of claims 1-10.

12. A computer programme product comprising a computer-readable medium which contains a computer programme according to claim 1 1.

13. A device for control of pumping work of a combustion engine (10) to lower a speed ω of the engine (10), which engine has an intake pipe (2) and an exhaust pipe (22) connected to it, characterised in that the device comprises at least one first means by which a gas pressure in the intake pipe (2) is arranged to be regulated so that the pumping work of the engine (10) increases or decreases.

14. A device according to claim 13, in which the first means is adapted to increasing the pumping work by lowering the gas pressure in the intake pipe (2).

15. A device according to claim 13 or 14, in which the first means is a throttle damper (1) adapted to assuming various different positions in the intake pipe (2) and thereby regulating the gas pressure in the intake pipe (2).

16. A device according to claim 15, in which the engine (10) is also connected to a gearbox (20), and

- the device is adapted to lowering the gas pressure in the intake pipe (2) at the time of a gear upshift.

17. A device according to claim 16, in which the damper (1) is adapted to assuming various positions between a first extreme position and a second extreme position, the first extreme being a fully open position resulting in a maximum gas pressure in the intake pipe (2), and the second extreme a fully closed position resulting in a minimum gas pressure in the intake pipe (2); and

- the damper (1) is adapted to assuming a first position adjacent to the second extreme position during the gear upshift.

18. A device according to claim 17, in which the gas pressure in the intake pipe (2) when the damper (1) assumes the first position is between 10 and 80% of the gas pressure when the damper (1) assumes the first extreme position.

19. A device according to claim 18, in which the gas pressure in the intake pipe (2) when the damper (1 ) assumes the first position is between 20 and 70% of the gas pressure when the damper (1) assumes the first extreme position.

20. A device according to claim 16, in which the gearbox (20) is an automatically controlled gearbox.

21. A device according to any one of claims 13-20, in which the engine (10) is a piston engine, e.g. a diesel engine, gas engine, ethanol engine or petrol engine.

22. A device according to any one of claims 13-21, further comprising at least one second means by which a gas pressure in the exhaust pipe (22) is arranged to be regulated so that the pumping work increases or decreases.

23. A device according to claim 22, in which the pumping work is increased by an increase in the gas pressure in the exhaust pipe (22) by means of an exhaust damper (1 1), e.g. an exhaust damper, or a VGT.

24. A motor vehicle, e.g. car, truck or bus, provided with at least one device according to any one of claims 13-23.