WO1991008388A1

WO1991008388A1 - Arrangement for turbo regulation in an internal combustion engine

Info

Publication number: WO1991008388A1
Application number: PCT/SE1990/000757
Authority: WO
Inventors: Sten Jiewertz; Mats Eriksson
Original assignee: Saab Automobile AB
Current assignee: Saab Automobile AB
Priority date: 1989-11-24
Filing date: 1990-11-22
Publication date: 1991-06-13
Anticipated expiration: 1992-05-24
Also published as: SE463429B; SE8903966D0

Abstract

The invention relates to an arrangement for obtaining increased possibilities of regulating a supercharged internal combustion engine. For the purpose of providing the driver with the possibility of adapting the supercharging level for a number of partial speed ranges in the speed range of the internal combustion engine, use is made of a setting device (6) which can be manually actuated by the driver. The setting device (6) comprises setting controls (7) with which the driver can selectively regulate the supercharging level between a minimum level and a maximum level for a number of partial speed ranges which together form the speed range of the engine. In this way the driver can adapt the torque characteristic of the engine to the prevailing operating conditions and/or the desired engine torque character.

Description

Arrangement for turbo regulation in an internal combustion engine

The invention relates to an arrangement for regulating the charge air pressure in an internal combustion engine in accordance with the preamble of patent claim 1.

Prior Art

For regulating the charge air pressure in the internal combustion engine of a vehicle, it is already known to use manual controls which, upon actuation by the driver, provide different degrees of regulation of the charge air pressure received from the compressor.

In turbo systems with a compressor arranged in the intake system ot .ne engine and driven by a turbine arranged in the exhaust gas system of the engine and driven by exhaust gas, the charge air pressure can be regulated by a valve which is arranged in a bypass line bypassing the turbine and which regulates the exhaust gas flow through the bypass line and thus the turbine. This valve can be controlled directly by the engine intake pressure in such a way that, when the charge air pressure exceeds a certain value, the valve opens, whereupon the increase in the charge air pressure is reduced.

German patent application DE-A-2,362,133 shows such a system in which it is possible manually to increase the charge air pressure level at which the bypass valve opens. This results in an increase in the charge air pressure and thus the torque to a higher level, which is maintained over the entire speed range. This means, however, that the engine must be dimensioned for the highest load occurring in the engine speed range and that the torque characteristic of the engine is increased uniformly over the entire speed range of the engine.

In German patent DE-C-2,928,902, the opening of the bypass channel is controlled, on the one hand, by the charge air pressure following the compressor and, on the other hand, by the pressure behind the throttle valve of the engine. The bypass valve opens here when the charge air pressure following the compressor exceeds an upper pressure level and when the pressure downstream of the throttle valve lies below a lower pressure level. In order to give a quicker response on acceleration from lower speeds when the charge air pressure has not had time to develop to a level exceeding the lower pressure level, the driver can manually cut out the effect of the pressure downstream of the throttle valve.

American patent US-A-4,598,549 shows another system for manual turbo regulation in which the charge air pressure is ventilated off at selectable charge air pressure levels. By means of a change-over switch actuable by the driver, the turbo function can be regulated either in economy state or normal state where the charge air pressure is ventilated off at different levels for the respective turbo function state. This manual regulation too provides a uniform adaptation of the turbo pressure and thereby the engine torque over the entire speed range.

However, these previously known alternatives for manual regulation have had the disadvantage that the driver can only choose between different fixed supercharging levels which, for the turbo unit in question, give a similar appearance to the engine's speed-dependent torque characteristic.

The known regulating systems for supercharged internal combustion engines have only been able to act on the charge air pressure in a defined manner over the entire speed range or have only been active from the regulating point of view at certain speed ranges. The driver has therefore had limited possibilities of acting on the torque character of the engine.

Object of the invention

An object of the present invention is to improve, in a supercharged internal combustion engine, the possibility of adapting the torque characteristic of the internal combustion engine to the desired drive mode and the prevailing operating conditions. To this end, the arrangement according to the invention is characterised by the features stated in the characterising clause

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In an advantageous embodiment of the arrangement according to the invention, the manoeuvring unit for charge air regulation is combined in manoeuvring panel accessible to a driver of a vehicle driven by the supercharged engine. In this way the driver can alter, during travel, the torque characteristic of the engine when the driving conditions so require. By also providing a number of setting controls which each regulate the degree of supercharging within a partial speed range, in sequence in increasing order of partial speed, and by using controls which are pushed transverse to their relative arrangement on the manoeuvring panel, the arrangement is given good overall clarity and controllability so that a safe and functional handling is permitted.

In one application of the arrangement according to the invention, the driver of a vehicle with a supercharged internal combustion engine can adapt the degree of super-charging in such a way that, holding constant speed in top gear and driving the vehicle at an indicated, fixed speed limit, a reduced maximum charge air pressure is obtained at the given engine speed for the actual driving speed and gear in question. In this way the engine can be regulated more easily for holding constant speed, without powerful torque shocks on accelerator activation. By virtue of the fact that the driver can set a higher charge air pressure level for a slightly higher speed range, a powerful torque increase can be obtained on changing down, which provides higher engine speed. In this way the driver can adapt the charge air pressure in such a way that the internal combustion engine obtains an engine torque character similar to aspirating engine operation on holding constant speed, which provides increased driveability and reduced fuel consumption, but obtains, on changing down to higher engine speed, an engine torque character of the turbo type.

Other more advanced drivers requiring maximum engine torque at all speed ranges can, by setting the controls to the maximum charge air pressure position for all partial speed ranges, quickly obtain the torque character which gives this particular driver the desired driveability and driving satisfaction.

When driving on roads with a poor base, such as roads covered with gravel or ice, a quick downward regulation of the charge air pressure can take place for desired speed ranges so that a safer driving of the vehicle is achieved, without powerful torque shocks at selected speed ranges. Other characteristic features will emerge from the patent claims and the following description of an embodiment of the arrangement according to the invention. The description is given with reference to the attached figures.

Brief description of the figures

Figure 1 shows a basic design of a turbo system according to the invention, Figure 2 shows an alternative embodiment of a manoeuvring panel with manual setting elements,

Figure 3 shows a second alternative of the manoeuvring panel mounted in the instrument panel of a motor vehicle, and

Figure 4 shows a basic torque diagram over an obtainable,adjustable torque range with alternative adjustably obtained torque characteristic curves.

Description of an exemplary embodiment

Figure 1 shows a turbo system according to the invention. In contrast to a conventional aspirating engine, the supercharged internal combustion engine 3 is provided with an improved filling during the aspirating cycle by means of a supercharger 2, which gives more efficient combustion, increased power and higher torque. With the aid of the supercharger 2, a performance is obtained which is comparable to that of a larger engine, but while retaining the advantages of the smaller engine as regards fuel consumption, space requirements and weight.

The supercharging can be achieved with the aid of a supercharger of the turbo compressor type, also called a turbo, which involves the exhaust gases of the engine 3 being used as drive medium. The exhaust gases from the exhaust collector 45 are passed through an exhaust gas turbine 23 and thus cause the turbine blade wheel to rotate. The blade wheel of the turbine 23 is secured on the same shaft as a compressor blade wheel 22 and rotates at the same speed. The compressor wheel is placed in the intake system 21, 27, 28, 29 and generates there a pressure increase which gives rise to improved filling in the cylinders of the internal combustion engine 3. By designing the turbo for early operational engagement, i.e. pronounced charge pressure build-up, even at relatively low speeds a higher torque is obtained in speed ranges which are used under normal driving conditions. An earlier predominant adaptation of the turbo usage has been aimed at giving increased peak output, which means that it is primarily active in the upper speed range of the engine under high loads on the engine.

The charging pressure in the inlet pipe is primarily dependent on the engine speed and load. At higher load, however, the charging pressure is limited by a charging-pressure regulator 24, 25, 40, 44. The charging-pressure regulator is placed on the exhaust side of the engine and regulates, via the flap valve 24, the exhaust gas flow through a bypass channel 46 on the side of the exhaust gas turbine 23.

When the load increases and the charging pressure approaches the desired value indicated for the operating conditions, the flap valve 24 opens and allows some of the exhaust gases to pass through the bypass channe 46 directly to the exhaust gas outlet 20, the exhaust gas turbine 23 being unloaded. The flap valve 24 is acted upon by a control rod 44 from a diaphragm pot 25 placed on the supercharger unit 2. A spring 40 in the diaphragm pot 25 has the task of closing the flap 24. The diaphragm is acted upon by the compressor pressure, which is passed via a line 41 over a solenoid valve 26 and on into a line 42 to the diaphragm pot 25. The solenoid valve 26 is controlled in a conventional manner between a closed and an open position by means of an electrical control unit 10, by electrical pulse- width modulation. In the closed position, an evacuation channel 43 is closed, which means that the diaphragm pot 25 is acted upon by the full pressure following the compressor 22. The charging-pressure regulator then opens the flap valve 24 at a lower charge air pressure level, which is determined by its basic setting, with a return spring 40 designed for this purpose. In the open position, the pressure is evacuated through the evacuation channel 43 to the inlet side of the compressor. The diaphragm pot 25 of the charging- pressure regulator thus becomes pressureless and then closes the flap valve 24, which gives a maximum charge air pressure following the compressor since the entire exhaust gas flow passes the exhaust gas turbine 23, which directly drives the compressor 22. While driving, the solenoid valve pulsates between the open and closed position at a fixed frequency, for example 12 Hz. By means of the pulse- width modulation of the control device 10, the ratio between the time the solenoid valve is open and closed during a pulse cycle is altered. The level of the charge air pressure can therefore be regulated by the control device 10 as a function of detected engine parameters. The control device 10, which consists of a conventional microprocessor with integrated memory units, receives electrical signals from a knock sensor 22 arranged on the engine block, a pressure sensor 33 arranged in the inlet pipe 29, a distributor-based speed sensor 31 and a throttle position potentiometer 34 via lines 39, 37, 38 and 36 respectively.

As the control device 10 has stored desired values for the maximum charge air pressure for different detected engine parameters, the solenoid valve is controlled so that these desired values are not exceeded. These desired values for the charge air pressure are primarily indicated for preventing the internal combustion engine from knocking and to prevent the exhaust gases from reaching excessive temperatures. At increasingly higher engine speeds and higher loads, an even greater part of the exhaust gas flow is conveyed past the exhaust gas turbine 23 by means of the factthatthe desired values for the charge air pressure stored in the control unit are reduced on rising engine speed and/or load.

A regulation of the charge pressure of the supercharging unit, in which only one reduction of the charge pressure takes place to obtain a margin against knocking occurring in the internal combustion engine, often gives rise to an engine which is difficult to handle and which, in the event of small changes of the accelerator, causes great changes in torque.

A method for making the internal combustion engine more easily regulated may, for example, comprise the throttle position also being detected. In the event of small throttle openings, the charge air pressure is reduced more than is justified by a reduction taking into account, for example, the risk of knocking. A throttle-position-dependent reduction of the charge air pressure makes the internal combustion engine more easily regulated on holding constant speed under partial load and at small throttle openings, and therefore increases the driveability for the average driver despite the factthatthe latter still has access to higher charge pressures at greater acceleration. However, a consequence of this is that the feeling of a quick response, which is typical of the turbo engine, on small changes of the accelerator and at partial load ranges is lost.

In order to increase the driveability in this way and to make the engine more easily regulated on holding constant speed under partial load, the control unit 10 can also take account of the detected throttle position by means of a throttle potentiometer 34. For small throttle openings, the control unit therefore contains stored reduction factors for the charge air pressure, which reduce the charge air pressure in inverse proportion to the decreasing throttle opening. This means that small accelerator changes at a small engine load do not result in greatly increasing engine torque.

By virtue of the fact that the control unit also senses knocking by means of the knocking sensor 32, the desired values stored in the control unit can be reduced in order for the knocking state to be eliminated. The reduction can be carried out in steps until the knocking state has been cancelled, which means that these desired values are optimised for the fuel quality and individual engine in question. The reduction factors can of course instead be stored in table format in the control unit 10 with reduced desired values for the charge air pressure. A knock-eliminating system of this type is described in greater detail in patent SE- B-427,861.

According to the invention, the control unit 10 also receives manually adjustable reduction factors for each individual partial speed range by means of a manual setting device 6 connected to the control unit 10 via line 30. The setting device 6 advantageously comprises a number of individual setting controls 7 for each partial speed range.

Figure 2 shows an alternative embodiment of the setting device 6. By means of a multi-positional turbo function selector 12, a driver can choose between a manually adjustable and speed- dependent supercharging degree in a function position M or a number of fixed supercharging functions E,S. The fixed supercharging functions stored in the control unit can differ for each function position and can be optimised for different characteristics from the point of view of response or operating economy. For example, one position can represent an economy position E which regulates the charge air pressure towards desired values which give the lowest fuel consumption. Another fixed function can be obtained in a standard position S where the supercharging degree is guided towards desired values giving optimal torque, but where fixed reduction factors act on the charge air pressure as a function of the throttle position. Othertypes of regulating principles can also be used for other function positions.

In the manual function position M, an adjustable supercharging degree is however permitted for each partial speed range by means of slide potentiometers 7. These can be set in steps or steplessly between a maximum desired value at one end position of the potentiometer and a minimum desired value forthe charge air pressure at the other end position. In the exemplary embodiment shown, nine slide potentiometers are used which, in partial speed intervals of 500 rpm, permit manual setting of the supercharging degree for each speed. As the turbo unit becomes operational and contributes essentially to supercharging at a certain given minimum speed, use is made of a first setting control at this given minimum speed for the unit. Desired values for supercharging degrees between the manually adjusted speeds are advantageously obtained by means of an interpolation carried out in the microprocessor of the control unit 10.

By arranging the slide potentiometers in increasing order of partial speed across the manoeuvring panel 8 and by making each slide potentiometer adjustable between an upper end position and a lower end position, preferably representing the maximum and minimum charge pressure respectively, a good overall clarity is achieved in respect of the charge air pressure set over the speed range of the engine.

In orderto give the driver clearer information on where in the engine torque characteristic the set engine torque is situated, the manoeuvring panel can comprise a torque diagram 13 with a maximum and a minimum engine torque curve 50 and 51, respectively. The particular engine torque curve set is advantageously visualised by means of a light-emitting diode being lit in a row 14 of light-emitting diodes stretching between the minimum and maximum engine torque curve 51 and 50, respectively, for each adjustable partial speed range. A further alternative embodiment of the setting device 6 is shown in Figure 3 where the setting device 6 is arranged on a car's instrument panel 60 at the driver's seat. The manoeuvring panel 8 of the setting device 6 is advantageously arranged in a secondary zone 66 to the side of the steering wheel 61 in a prepared recess of DIN type intended for different types of extra equipment such as car radio apparatuses and the like. In the secondary zone 66 there are several manoeuvring controls, such as ventilation controls 63, 65 and other electrical function switches 62, which the driver can reach from the driver's seat. Arranged in a conventional manner in the primary zone 64 of the instrument panel 60 are the instruments essential for monitoring the vehicle.

In this embodiment in Figure 3, instead of a number of slide potentiometers use is made of only one setting control 7 which, via a step control 11 , can selectively regulate the supercharging degree for an advance partial speed range. By actuating the step control 11 to the right or left, the driver can advance to the partial speed range which is to be regulated. The manually set supercharging level is advantageously visualised by allocating to each partial speed range a stack 15 of several light-emitting diodes, lamps or the like arranged in a row and forming the stack. The actual position of the set supercharging level between the minimum and maximum supercharging level is advantageously shown by means of one of the lamps or diodes giving a fixed light. When the driver has advanced to a specific partial speed range which is to be regulated, this advance partial speed is indicated as a flashing of the previously fixed-light indicator lamp in the associated stack 15 for the actual partial speed range. By means of a subsequent actuation of the setting control 7 upwards or downwards, the position of the set supercharging level is affected to a corresponding degree for the advance partial speed range.

A number of other variants of the manoeuvring panel 8 for the setting device 6 can be designed within the scope of the invention. For example, the step control 11 can be omitted and each indicator stack in the embodiment shown in Figure 3 can be allocated its own setting control 7. As in Figure 3, this setting control 7 consists of a toggle switch which isstable in an intermediate position and which, upon actuation upwards or downwards, reaches a non-stable position in which the supercharging level is affected upwards or downwards, respectively. The same type of toggle switch can be used for the step control 11.

The setting device 6 advantageously comprises all the control equipment necessary for its functioning. The step function and the actuation members for the light diodes are obtained advantageously by means of integrated circuits. The supercharging functions set or selected from the setting device are transferred either as serial-transferred information via signal line 30 to the control unit 10 or as parallel-transferred information via a multi- conductor. In the case of slide potentiometers being used as setting controls 7, the setting device comprises an analog-digital converter when the information is transferred serially.

Although the exemplary embodiment relates to a turbo compressor 2, the invention is not limited to this type of supercharging unit. In screw compressors driven by rotating engine shafts, the supercharging level is affected in the same way with a manual setting device for each individual partial speed range, but instead of regulation of a wastegate valve, the inlet slide of the screw compressor is regulated. This manual setting device can in a similar way affect the regulating procedure typical for each supercharging unit.

Figure 4 shows a typical torque diagram for an internal combustion engine, on the one hand in aspirating engine mode, full-line curve 51, and with maximum supercharging degree, full- line curve 50. The torque characteristic forthe supercharged engine mode is optimised by suitable adaptation of the turbo unit so that the highest torque is obtained at those speeds prevailing in normal vehicle drive. By means of the arrangement according to the invention, the driver can selectively regulate the torque characteristic which is desired between a level corresponding almost to aspirating engine mode and a level corresponding to maximum supercharging degree for each partial speed range. The broken-line curve 52 shows a possible set torque characteristic in which the engine torque corresponds to an aspirating engine at speeds below 3000 rpm and, at increasing speeds, finally reaches maximum supercharging level and engine torque at 5000 rpm and over. Such regulation may be desirable on poor road surfaces where the wheels spin loose on starting or when the driver wishes to obtain substantial torque increase at speeds over 3000 rpm. Another alternative setting is shown by dotted curve 53, where a high and uniform torque is obtained over the entire operating speed register of the engine. Such a setting may be desirable when maximum driving comfort is desired at a high engine torque withoutthe substantial torque increase at increasing speeds which is typical of the turbo engine.

The above description of an exemplary embodiment of the arrangement according to the invention should not be regarded as limiting the inventive concept as set out in the patent claims. The invention can be modified in a number of embodiments, of which only some have been touched upon in the description. The manual regulation of the charge air pressure can of course also act directly or indirectly on the ignition system and fuel system functioning so that these systems, together with the main charge pressure regulation, obtain optimal functioning.

Claims

Patent Claims

1. Arrangement for regulating the charge air pressure in an internal combustion engine (3) supercharged by means of a charge air unit (2), comprising a regulating member (24, 25, 26) for regulating the supercharging of the charge air unit, a number of sensors (31-34) sensing different engine parameters, and of which sensors one consists of an engine- speed sensor (31), and an electrical control unit (10) designed to emit control signals to the regulating member (24-26) for regulating the charge air pressure as a function of input signals from the sensors (31-34), the control unit (10) comprising a memory unit containing stored desired values for the said regulation, characterised in that the control unit (10) is connected to a manually actuable setting device (6), in that the setting device is designed to change, upon manual actuation, the control signals from the control unit to the regulating member (24-26) in relation to the stored desired values, and in that the setting device (6) is designed to permit different changes of the control signals of the control unit for a number of different partial engine speed ranges by means of a manually actuable setting control (7) for each partial engine speed range.

2. Arrangement according to patent claim 1 , characterised in that the setting device comprises an individual setting control (7) for each settable partial speed range.

3. Arrangement according to patent claim 1, characterised in that the setting device comprises a setting control (7) which, by means of a step function which can be called up by means of a manually actuable step control (11), permits setting possibilities for each partial speed range selected by means of the step function.

4. Arrangement according to patent claim 2 or 3, characterised in that the setting control (7) is designed to permit an alteration of the control signals of the control unit between at least an upper and a lower value for the charge air pressure forthe respective partial speed range.

5. Arrangement according to patent claim 4, characterised in that the setting control (7) is adjustable in a number of positions between the upper value and the lower value.

5 6. Arrangement according to patent claim 4 or 5, characterised in that the upper value consists of desired values stored in the memory unit for maximum super-charging air pressure with regard to at least the risk of knocking in the internal combustion engine, and in that the lower value consists of a minimum supercharging degree forthe charge air unit of the o internal combustion engine.

7. Arrangement according to patent claim 2, characterised in that all the setting controls (7) are grouped on a manoeuvring panel (8) accessible for manual regulation by a driver of a vehicle driven by means of the internal 5 combustion engine (3).

8. Arrangement according to patent claim 2, characterised in that the manoeuvring controls (7) consist of a manually actuable indicator (7, 15) which is movable in a first direction, and in that all the indicators (7, 15) for 0 the individual partial speed ranges are arranged one after the other perpendicular to the said first direction in increasing partial speed ranges for the indicators (7, 15).

9. Arrangement according to patent claims 2-8, characterised in that the 5 partial speed ranges which can be aded upon by the setting controls (7) together form the entire speed range of the engine, by which means the degree of supercharging of the internal combustion engine can be regulated individually for each partial speed range over the entire speed range of the engine. 0

10. Arrangement according to any one of the preceding patent claims, characterised in that the manual regulating of the setting device with respect to the partial speed ranges can be activated selectively by means of a multi-position selector which can be set to at least one additional regulating 5 function for the supercharging air pressure given by desired values stored in the memory unit of the control unit, which are not manually adjustable for different partial speed ranges.