Technical field

The present invention relates to a method for initiating calibration of a damper. The invention relates in particular to a method according to the preamble of claim 1. The invention further relates to a system, an engine system and a motor vehicle.

Background to the invention

Figure 1 depicts schematically a gas flow in an engine system which in this example comprises a diesel engine with a turbo and a number of pipes connected to the engine. Air is drawn in from the left in Figure 1 through an inlet pipe, is compressed in a turbocompressor 30 and is cooled in a charge air cooler 31 before passing a throttle damper 1 which regulates the amount of air entering the diesel engine 10. After the throttle damper, the air is mixed with recycled exhaust gases, so-called exhaust gas recirculation (EGR), and the resulting mixture is then drawn into the engine's cylinders to be mixed therein with diesel fuel before combustion takes place in the engine.

The exhaust gases from the combustion process then pass through a turbo turbine 33 which drives the turbocompressor 30. However, some of the exhaust gases enter an EGR pipe and are led back to the inlet pipe via an EGR damper 1 and an EGR cooler 32. The function of the EGR damper is to regulate the amount of exhaust gases recycled to the combustion process. Before they finally leave the engine system, the exhaust gases pass an exhaust damper 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 34 (DPF, diesel particle filter) and a so-called SCR (selective catalytic reduction) catalyst 35.

The SCR catalyst 35 of a motor vehicle with a diesel engine 10 operates only when the temperature of the exhaust gases is high enough, typically over 200°C. If the engine is not under heavy load, the exhaust gases will be at a lower temperature than desired and will therefore cool the catalyst. One way of limiting the amount of cooling exhaust gases is to use a damper situated in an air inlet pipe to the engine 10. The amount of air entering the engine may thus be limited, leading to the exhaust gases from the engine also being limited. This damper 1 is usually called throttle damper, as mentioned above.

As described above and depicted in Figure 1 , there is most commonly a plurality of dampers (throttle damper 1, EGR damper 1 , exhaust damper 1) to control the gas flow in engines 10 of more modern kinds. These dampers 1 are most commonly each provided with a position sensor 3 for determining their position. Figure 2 depicts an example of a system in which a throttle damper 1 is provided in an inlet pipe 2 connected to an engine 10 in order to regulate a gas flow in the inlet pipe. The system further comprises a control device for controlling the position of the throttle damper in the inlet pipe, which involves using an arrangement whereby actuators driven by compressed air 20 via a valve 21 act upon a spring 24 connected to a control means 25 which is itself connected mechanically to the throttle damper 1. This arrangement makes it possible for the throttle damper 1 to be turned to different positions in the inlet pipe 2. It is also usual for actuators to be driven by electric motors in certain types of motor vehicles. The system comprises also a position sensor 3 adapted to communicating with a control unit 1 10 by means of communication signals (respective output and input signals 22, 23).

Throttle dampers 1 and other types of dampers are usually capable of assuming a plurality of positions between a first extreme state and a second extreme state, depending inter alia on current speed ω of the engine, desired engine torque, etc. The first extreme state is a fully open position resulting in a maximum gas flow (or minimum restriction of gas flow) in the pipe 2, and the second extreme state is a fully closed position resulting in a minimum gas flow (or maximum restriction of gas flow) in the pipe 2. Figure 2 shows the throttle damper 1 in an intermediate position between fully open and fully closed.

Most dampers 1 are also capable of reaching different positions in the pipe 2 at varying rates of movement v, since their position in the pipe has for example to correspond to the engine speed ω for the flow of air through the engine to be appropriate to the desired combustion in the cylinders. The actual control of the control means and hence of the damper is most commonly by a control unit 1 10 (not depicted in Figure 2), usually in the form of a so-called ECU (electronic control unit) capable of controlling various functions in a motor vehicle. The system in Figure 2 comprises a position sensor 3 with the function of measuring the position of the throttle damper 1 in the inlet pipe 2 by registering signals when the damper reaches its various positions in the inlet pipe. Owing to variability between individual dampers of the same kind, their extreme states have to be calibrated individually on position sensors, since any given position sensor does not know which sensor values correspond to the extreme states of a given damper. One of the reasons is that the signal for an extreme state usually changes over time, e.g. because of ageing of the sensor's electronics or wear and fouling of the damper. The signals for extreme states may also change with the temperature of the damper.

Calibration is usually effected by the damper being turned to its two extreme states (fully open and fully closed) in succession and by the sensor signal for each of these extreme states being saved. The actuators used for turning the damper to different positions are generally very powerful, resulting in obvious risk that persons in the vicinity when calibration is being done might be liable to injury when the damper moves between its extreme states, e.g. if the persons concerned have some part of their body close to the damper, e.g. a finger in the pipe when the damper moves.

Brief description of the invention

An object of the present invention is to propose a method which wholly or partly solves prior art problems. In particular, the invention relates to reducing the risk of injury to persons during calibration of a damper.

Another object of the invention is to propose an alternative method for initiating calibration of a damper. A further object of the invention is to propose a method for initiating calibration of a damper and for calibrating it.

According to an aspect of the invention, the above objects are achieved with a method for initiating calibration of a damper which is situated in a pipe and is capable of assuming a plurality of positions between a first extreme state and a second extreme state, thereby regulating a fluid flow through the pipe, the first extreme state being a fully open position resulting in a maximum fluid flow in the pipe, and the second extreme state a fully closed position resulting in a minimum fluid flow in the pipe, which calibration of the damper is initiated if the speed ω of the engine is greater than zero, and involves the damper being caused to turn to at least one of said extreme states.

Various embodiments of the above method are described in the dependent claims pertaining to it.

According to another aspect of the invention, the above objects are achieved with a system comprising at least one damper and at least one control unit which is capable of controlling the damper, which damper is situated in a pipe connected to an engine, and of assuming a plurality of positions between a first extreme state and a second extreme state, thereby regulating a fluid flow through the pipe, the first extreme state being a fully open position resulting in a maximum fluid flow in the pipe, and the second extreme state a fully closed position resulting in a minimum fluid flow in the pipe, which system is capable of initiating calibration of the damper if the speed ω of the engine is greater than zero, which calibration involves the damper being caused to turn to at least one of said extreme states.

The damper or the system above may form part of an engine system which also comprises the engine. Said engine system may for example be suited to marine or industrial use but may also be part of a motor vehicle.

The present invention makes it possible to avoid or reduce injuries to persons during calibration of dampers since calibration is only initiated if the engine speed is greater than zero. This is particularly relevant when mechanics carry out maintenance or repair of the motor vehicles or when fitters work on such engine systems or motor vehicles during their production.

Further advantages and applications of the invention are indicated by the detailed description set out below. Brief description of drawings

The present invention is described below with reference to the attached drawings, in which Figure 1 depicts schematically a gas flow in an engine system, Figure 2 depicts schematically a system comprising a throttle damper situated in an air inlet pipe, a control device for the throttle damper and a position sensor for the throttle damper,

Figure 3 is a flowchart for an embodiment of the invention, and

- Figure 4 depicts schematically a control unit for controlling a damper.

Detailed description of the invention

The foregoing description indicates obvious risk of injury to persons during calibration of dampers 1. This risk is particularly obvious when mechanics are engaged in repair and/or maintenance of, for example, an engine system in which a damper is fitted.

Calibration of dampers 1 routinely arises during starting of the engine 10, i.e. once the ignition has been switched on. This means that calibration may take place before the engine is started. As it is usual for the ignition to be on during repair/maintenance or production of engine systems or motor vehicles, there is obvious risk that persons may for example have their hand close to a damper which is being calibrated.

According to the invention, initiation of calibration of a damper 1 therefore takes place if the engine 10 has been started, which means that its speed ω has to be greater than zero for initiation to be undertaken.

Generally speaking, a current engine speed ω may be compared with a limit value ω, to decide whether calibration is permissible or not. If the engine speed ω is greater than the limit value co, , calibration is allowed (initiated) according to another embodiment of the invention.

It has further been found by the inventors that it is desirable for calibration of dampers 1 to be done when they are fitted in the right installation and in operating conditions, i.e. where they are fitted in a system in which they are to be used, e.g. in an engine system in a truck when the engine 10 is running. If for example calibration is effected when the damper is not fitted in such a system during operating conditions, differences in, for example, vibration levels and temperatures compared with when the damper is fitted in an actual system will unacceptably affect the result of the calibration, since the conditions are different. With the present invention it is only possible to initiate calibration of dampers when the engine is running, thereby ensuring that calibration takes place when the damper is fitted in the right installation during operating conditions.

To further reduce the risk of accidents in connection with calibration of dampers, further conditions may be set for when it is permissible. According to another embodiment of the invention, calibration is therefore initiated if the engine speed ω has been greater than the limit value ω _τ for a period of time P, which means that for initiation to be permissible the engine speed ω must not have dropped below the limit value ω _Ύ during the period P. The period P preferably assumes a value of between 1 and 10 seconds. This embodiment further reduces the risk of accidents during calibration.

According to an embodiment, the actual calibration of the damper is done by its being turned to a first extreme state (fully open position) and a second extreme state (fully closed position) in quick succession, or vice versa. According to another embodiment, the damper is capable of reaching different positions in a pipe 2 in which it is fitted at varying rates of movement v, which means that its movement between the first extreme state and the second extreme state takes place at a rate v which is a function of its current position relative to the first extreme state and/or the second extreme state.

According to a further preferred embodiment of the invention, the rate of movement v of the damper 1 is slower at the second extreme state than at the first extreme state, which means that it closes at a slow rate when about to reach the fully closed position. The slower rate v may preferably be between 1 and 20 degrees per second, whereas a higher rate might be around 500-1000 degrees per second in the case of dampers of disc type, depending on the volume of gas flow in the pipe in which the damper is fitted. This embodiment makes it possible for a person who has a finger or some other part of their body in the damper to remove it before any trapping might occur.

If the damper 1 is fitted in a pipe 2 for a motor vehicle, the pipe is preferably either an air inlet pipe or an exhaust pipe or an EGR pipe and is also connected to the engine 10. According to a further embodiment, the damper 1 is a throttle damper fitted in an inlet pipe 2 which is connected to a diesel engine or some other type of suitable engine.

The method according to the invention may further comprise the steps of:

- registering, when the damper reaches the first extreme state, a first signal which represents its position in the first extreme state;

registering, when the damper reaches the second extreme state, a second signal which represents its position in the second extreme state; and

using the first signal and the second signal during calibration of the damper.

The aforesaid positions for the extreme states are registered by a position sensor 3 which sends to a control unit 1 10 signals which represent the extreme states reached by the damper 1. Signals which represent the state which a damper 1 assumes in a pipe 2 typically take the form of a voltage signal of between 0 and 5 volts. The first and second signals above are then used by the control unit 1 10 to define the potential range of a signal which represents the damper's current position in the pipe, e.g. between 0.5 and 4.5 volts. If there is a linear relationship between the signal from the position sensor and the damper's position in the pipe, the first and second signals will therefore define extreme points of a linear function whereby the damper's state in the pipe is a function of the signal from the position sensor.

Figure 3 is a flowchart of an embodiment of the invention. Step Fl checks whether calibration of a damper 1 has not been initiated and, if such is not the case, step F2 checks whether the engine 10 has been running, which is done by comparing a current engine speed ω with a limit value ω, (in this case zero).

Step F2 may also check whether the engine speed ω has been greater than the limit value ω _τ during a period of time P, to see whether initiation is permissible according to an embodiment of the invention. If the engine speed ω is greater than the limit value ω _τ at step F2, the system waits at step F3 to see whether other conditions for initiating calibration are fulfilled, e.g. that the engine temperature is within a certain range, since this affects inter alia the friction between damper disc and damper housing, and the friction in any bearings of the damper. Nor may calibration of dampers in engine systems, e.g. throttle dampers and EGR dampers, take place at a time when it would appreciably affect other functions in the engine system, since it may be that in certain states calibration of throttles and EGR dampers might lead to the engine stalling because the amount of air supplied to it during calibration might be less than that required for combustion.

Step F4 checks whether these and any other conditions applicable are fulfilled, and if such is not the case the method goes back to step F3, otherwise step F5 effects calibration of the damper by first causing it to turn to a fully open position, followed by checking at step F6 that the signal from the sensor 3 is stable, i.e. that its value has not changed during a specific period of time, typically one second or a few seconds. If the sensor signal does not assume a stable value at step F6, the method goes back to step F5, but if the signal is stable it is saved at step F7 and is then used as a reference signal for the open position.

Step F8 causes the damper 1 to reach a fully closed position, followed by step F9 checking that the signal from the sensor 3 is stable, in which case it is saved and used as a reference signal for the closed position. The two reference signals are thereafter used for translating/interpreting the damper's current position in the pipe as above. If the signal does not assume a stable value at step F9, the method goes back to step F8.

As specialists will appreciate, a method 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 invention further relates to a system comprising at least one damper 1 according to any embodiment above and at least one control unit 1 10 capable of controlling the damper. The system is itself capable of initiating calibration of the damper on the basis of a speed ω of an engine 10. According to an embodiment, the system may further comprise a position sensor 3 capable of registering the extreme states of the damper 1 during its calibration.

Such a system as above may preferably be provided in a motor vehicle or form part of an engine system which comprises an engine 10. The engine system may be suited to marine or industrial use (e.g. electricity standby units), as specialists in the field will appreciate. It should also be noted that a damper, system and engine system according to the present invention may be modified according to various embodiments of the method according to the invention by suitable adjustments.

Regarding the control unit 1 10, such a unit for controlling a damper is schematically depicted in Figure 4. The control unit 1 10 comprises 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 11 is connected to a memory unit 112 which is situated in the control unit 1 10 and which provides the calculation unit 111 with, for example, the stored programme code and/or the stored data which the calculation unit 1 1 1 needs for it to be able to perform calculations. The calculation unit 111 is also arranged to store partial or final results of calculations in the memory unit 1 12.

The control unit 110 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 1 1 1. The output signal sending devices 1 14, 115 are arranged to convert signals received from the calculation unit 1 1 1 in order, e.g. by modulating them, to create output signals which can be conveyed to other parts of the system for determination of gear downshift and upshift points. Specialists will appreciate that the aforesaid computer may take the form of the calculation unit 111 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

(Controller Area Network) bus, a MOST (Media Orientated Systems Transport) bus or some other bus configuration, or a wireless connection. The connections 70, 80, 90, 100 in Figure 1 may take the form of one or more of these cables, buses or wireless connections.

Finally, it should be noted that the present invention is not restricted to the embodiments described above of the invention but relates to and comprises all embodiments within the protective scope of the attached independent claims.