Field of technology

This invention relates to arrangements that handle rotational information of an internal combustion engine. So, the invention relates to, for example, sensors means that measure position of the engine's crank angle, or indicate the engines phase. Further the invention relates processor units that handle the measurement information from sensors. In addition, the invention relates to a network that distributes the rota- tional information.

Prior art

It is known to measure angular position of a crank shaft. This can be arranged, for example, by measuring angular position of the flywheel that is fixed on the crank shaft. An angular position sensor forms a pulse train that can be used for measuring position of the crank shaft, speed and a direction of the rotation. The pulse train is usually called as a position pulse train. There exist different solutions to the measurement and the creation of the position pulse train. It is also known to measure a phase of the engine. The measurement is achieved from the camshaft of the engine. The camshaft is provided with a cam that indicates a phase of the engine. The position pulse train signal and the phase signal are distributed in the engine system to the devices that use the signals. The installation of the distribution system of the signals is rather complex and expensive task.

Short Description of Invention

The objective of the invention is to provide a simple and cost-effective solution to the distribution of the position pulse train signal and the phase signal for the internal combustion engine. The objective is achieved in a way that is described in the independent claim. The idea of the invention is that the position pulse train signal and the phase signal are combined. In this way only one hardwired distribution network is needed for the devices using the signals.

The invention comprises an encoder that combines the signals. The position pulse train signal has a low level and a high level. The combination is made in such a way that voltage values of said levels of the pulse train signal in the common signal depend on the phase signal. Therefore the combined (common) signal carries the position information of the crank shaft and the phase information of the engine.

Drawings

Next the invention is described in more detail with the figures of the attached drawings in which drawings:

Figure 1 illustrates a schematic example of an arrangement of the invention and

Figure 2 illustrates a schematic example of an inventive signal comprising the posi- tion and phase information.

Description

The arrangement of figure 1 comprises an encoder 2 that can be situated in a control module 6 of an internal combustion engine 1. The encoder 2 is capable of receiv- ing pulse train information from a position sensor 4. It is practical that the position sensor 4 is located next to a flywheel 3 of the engine wherein the position sensor 4 detects pulses from the flywheel 3 teeth. The position information obtained from the pulses indicates a position of the engine's crank shaft, and can also be used for detecting speed and a direction of the rotation of the crank shaft. The encoder 2 is also capable of receiving phase information from a phase sensor 5 that can be installed next to the camshaft of the engine. The phase information from the phase sensor 5 depends on a structure of a cam on the camshaft and the phase sensor 5 itself.

The encoder 2 is arranged to combine the phase information of the engine and the position information. The combined, i.e. common, signal comprises the both informa- tion types. The encoder also (and the control module 6 in the example of figure 1 ) comprises an output 9 for sending the common signal. So, the common signal can be distributed to different devices 7, 8 that need and use the position and phase information. In figure 1 , the common signal is distributed to an electronic fuel injection control (EFIC) 8 and speed and load controller 7. The speed and load controller 7 may also be included in the electronic fuel injection control 8. Since the same signal comprises the both position and phase information, only one distribution network is needed. Therefore another hardwiring, as there are in prior art systems, is not needed. It should be noted that the other hardwiring may be required for safety rea- sons. Although, only one signal is used the accuracy of the signals remain. As can be also seen in the example of figure 1 the control device (7,8) may comprise a decoder 10 for decoding the common signal 21. The common signal can also be transmitted out from the engine's immediate surroundings, for example, to a remote monitoring system.

Figure 2 illustrates a schematic example of the common signal 21. A normal pulse train signal has a high signal level and a low signal level. The pulses are performed when the signal's amplitude changes from the low level to the high level and vice versa. The voltage values of the low and high levels can be changed by setting an offset value to the pulse train signal. In the common signal the offset value depends on the phase signal. The offset value, i.e. component, in the common signal is determined by the phase signal period. The phase signal can be illustrated as a periodic signal having two parts inside the period. The offset component is in the common signal according to another half of the phase signal's period. In such a way that the common signal 21 comprises one offset value (OFF1 ), two low levels (LL1 , LL2) and two high levels (HL1 , HL2). It should be noted that in this description offset of the pulse train signal is zero (no offset) when the low level of the pulse train is zero volts.

The phase signal determines moments when the offset is switched on or off in the common signal. The encoder is arranged to make these actions for forming the common signal. For example in figure 2, the first low level LL1 is zero volts and the first high level HL1 is above that value for example 18 volts. When a period P1 has passed, the phase signal has determined the switching-on of the offset OFF1. In this example the switching-on of the offset moves the first low level LL1 to the second low level LL2, for example to 6 volts. The first high level HL1 changes to the second high level HL2. When period P2, having in this example the same duration as period P1 , has passed, the offset value OFF1 is switched off, set by the phase information. The period of the offset change corresponds with the phase of the engine. It should be mentioned that the periods P1 and P2 may have different durations, but this feature do not hinder the detection of the engine's phase. Further the periods may differ a little if the switching on or off the offset occurs during the high level or the low level of the pulse train, i.e. not at moments of raising or falling edges of the single pulse.

The above example of figure 1 illustrates only one way to construct the inventive arrangement. Other solutions are also possible. For example, the encoder 2 can be placed into another location as the control unit 6. The encoder 2 can be realized as a software entity, a printed circuit board, and an ASIC-circuit etc. The position sensor 4 can also be placed to another location, such as a crank wheel.

Further, other devices and wires may have constraints on voltage levels that can be used. For example, 24 volts may be an upper limit. Therefore the encoder may have to convert the voltage level of the pulse train signal to be suitable for the distribution network. For example, the pulse train signal is decreased 6 volts in order to give space to the pulse train with the offset OFF1.

So, it is clear that the invention is not restricted to the embodiments described in this text, but the invention can be utilized in any suitable manner within the scope of the independent claim.