Technical field

The present invention relates to a method for 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 damper, 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 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 1 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 10 is not under heavy load, the exhaust gases will be at a lower temperature than desired and will therefore cool the catalyst 35. One way of limiting the amount of cooling exhaust gases is to use a damper situated in an air inlet pipe to the engine. The amount of air entering the engine may thus be limited, leading to the exhaust gases from the engine also being limited. This damper 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 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 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 3, 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 1 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. It is not desirable to allow the damper to reach the fully closed extreme state at too fast a rate, since this may lead to increased wear both on the damper and on its housing (which encloses the damper) where they meet. There is also 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 for calibration of a damper 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 calibration of a damper. A further object of the invention is to propose a method for calibration of a damper and for initiating calibration. According to an aspect of the invention, the above objects are achieved with a method for 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 involves the damper being caused to turn to at least one of said extreme states at a rate of movement v which is a function of the position of the damper relative to the first extreme state and/or the second extreme state.

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 damper for regulating a flow in a pipe, which damper 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, such that calibration involves the damper being caused to turn to at least one of said extreme states at a rate of movement v which is a function of its position relative to the first extreme state and/or the second extreme state.

According to a further aspect of the invention, the aforesaid objects are achieved with a system comprising at least one damper as above and at least one control unit which is capable of controlling the damper, which system is capable of effecting calibration of the damper by causing it to turn to at least one of said extreme states at a rate of movement v which is a function of its position relative to the first extreme state and/or the second extreme state.

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

The invention proposes a solution whereby a damper can be closed at controlled rates such that the risk of unnecessary wear on the damper and/or its housing is reduced or eliminated during calibration of the damper.

An embodiment of the present invention also makes it possible to avoid or reduce injuries to persons during calibration of dampers. 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 a device and a system according to 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 risk of unnecessary wear on dampers 1 and/or their housings during their calibration according to prior art. This problem is solved by the present invention in that the rate of movement v of the damper is a function of its position relative to either of its extreme states, which means that calibration can be conducted in a controlled way.

As previously mentioned, there is also obvious risk of injury to persons during prior art calibration of dampers. 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 in prior art during starting of the engine, i.e. once the ignition has been switched on. This means that calibration might 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. To reduce the risk of injury during calibration of such dampers 1, their calibration according to the invention is done in such a way that the damper is caused to turn to at least one of its extreme states at a rate v which is a function of its position relative to the first extreme state and/or the second extreme state. This means that the damper is capable of turning at varying rates of movement v to different positions in a pipe in which it is fitted.

According to an embodiment of the invention, the actual calibration of the damper 1 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 of the invention, the rate of movement v of the damper 1 is slower at the second extreme state (fully closed position) than at the first extreme state (fully open position), 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 EG pipe and is also connected to the engine 10, being the pipe which regulates the gas flow in the engine. 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 through which gas flows.

To further reduce the risk of injury to persons during calibration of such dampers 1, their calibration according to the invention may be initiated on the basis of a speed ω of an engine 10. Initiation preferably takes place when the engine has been started, which means that the speed ω of the engine has to be greater than zero for initiation to be permissible according to this embodiment. Generally speaking, a current engine speed ω may be compared with a limit value cy _r to decide whether calibration is permissible or not. If the engine speed ω is greater than the limit value ω _τ , calibration is allowed (initiated) according to another embodiment of the invention.

To further reduce the risk of accidents in connection with calibration of dampers 1 , 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, 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 co _r 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.

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 for an embodiment of a method according to the invention. Step F 1 checks whether calibration of a damper 1 is inactive and, if such is not the case, 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). If the engine speed ω is greater than a limit value ω _τ , other conditions for initiating calibration are also checked, 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 Fl may also check whether the engine speed ω has been greater than the limit value ω, for a period of time P for initiation to be permissible according to an embodiment of the invention.

If calibration of the damper is permissible because all of the conditions are fulfilled, step F2 applies a control signal so that the damper assumes a fully open position, followed by step F3 checking that the signal from the position 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 such is the case, the sensor signal is saved at step F4 and then used as a reference signal for the open position, otherwise the method goes back to step F2.

Step F5 applies a control signal so that the damper is turned towards a fully closed position, followed by step F6 checking whether the damper has passed a limit with regard to trapping risk. Depending on the size of the damper 1 , there is a limit at which there is deemed to be risk that a person might become trapped in the damper. This limit may be a predetermined limit, e.g. a specific distance or number of degrees denoting the damper's position in the pipe 2, which limit has to be defined such there is deemed to be no trapping risk. If the limit has not been passed at step F6, the method goes back to step F5.

When the damper passes said limit, step F7 turns it towards its fully closed state at a slow rate v such as to make it possible for any parts of a person's body to be removed from the damper and thereby avoid trapping. It should be noted that the invention makes it possible to implement a plurality of different limits so that the damper' s rate of movement v towards its closed state decreases gradually, which means that this rate is a discrete function of its position relative to either of its extreme states.

It is however also possible to have the damper's rate of movement v towards its closed state decrease continuously, in which case this rate is a continuous function of the damper's position relative to either of its extreme states.

Step F8 then checks whether the signal from the position sensor 3 is stable and, if such is the case, step F9 checks whether the sensor value is within a reasonable tolerance, which means that the signal from the sensor has to become stable at a value which is within reasonable limits for closed extreme state with respect to manufacturing and fitting tolerances for the position sensor. If the signal is not stable at step F8, the method goes back to step F7.

If the sensor value is within a reasonable tolerance at step F9, step F 10 saves the sensor signal and uses it as a reference signal for the closed state, but if the value is outside reasonable limits, step Fl l opens the damper 1 at a maximum rate because there is then risk that something/someone may have become trapped in the damper. Otherwise the two reference signals are used to translate/interpret the damper's current position in the pipe 2 as above. 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 effecting calibration of the damper by causing it to turn to at least one of its extreme states during the calibration. The movement of the damper during the calibration takes place at a rate v which is a function of its position relative to the first extreme state and/or the second extreme state. According to a preferred embodiment, the system may further comprise a position sensor 3 capable of registering extreme states of the damper 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 according to the invention is schematically depicted in Figure 4. The control unit 110 comprises a calculation unit 1 11 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 1 1 1 needs for it to be able to perform calculations. The calculation unit 1 1 1 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 113, 1 14, 1 15, 116 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, 1 16 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 11. 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 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

(Controller Area Network) bus, an 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.