The field of the invention Engine speed control systems are important systems, in term of the fact that a diesel engine itself is an instable system. By improving a speed controller system (SCS) a benefit at the economical side will be noticeable on the basis of the reduced fuel consumption. The state of the art

Ships often have big two stroke diesel engines. The engine control is arranged with external SCS which measures the engine speed by counting the teeth of the fly wheel. After processing the measured data the SCS system sends a fuel command signal to the electronic control system which provides the correct fuel amount per cylinder.

The main drawback in the use of the external control system is that the fuel regulation is performed on the basis of the speed of the fly wheel making the dead band (i.e. not controllable band) fairly big and imprecise. This causes manoeuvring difficulties for the ship especially at very low revolutions. For example some ship engines do not run below 25 revolutions in dead slow position. Short description of the invention

The object of the invention is to accomplish an internal SCS (speed controller system) which is integrated in the already installed engine control system (ECS) to run the engine without an external speed controller to achieve benefit in the flexibility of the engine. This is achieved by a speed control system for improving engine speed control properties, the engine comprising fuel injection means for injecting fuel, at least two cylinders for burning said injected fuel, a piston in each cylinder for achieving a reciprocating linear piston motions as an effect of the burnt fuel, a crankschaft for translating said reciprocating linear piston motions into a rotation movement to obtain revolutions of the engine and an engine control system for controlling the engine. The speed control system is accomplished internally by integrating the speed control system into the engine control system, said internal speed control system comprising means for obtaining a crank angle information during the revolutions of the engine, a crank angle information calculator to calculate said crank angle information to speed and acceleration information, a crank angle information analyser for analysing said speed and acceleration information in order to generate a correction value for control processing by taking into an account at least one limiter function of the engine, means for obtaining a fuel injection time for each said cylinder, a fuel quantity meter for obtaining a fuel quantity value individually for each fired cylinder, and a control processor for utilizing said fuel quantity value and said fuel injection time to provide a history based initial injection quantity value individually for each cylinder, and for controlling revolutions of the engine by adding the correction value to the history based initial injection quantity value. The focus of the invention is also a method for improving engine speed control properties, the method comprising fuel injection to at least two cylinders for burning said injected fuel, achieving reciprocating linear piston motions as an effect of the burnt fuel in each cylinder and translating said reciprocating linear piston motions into a rotation movement to obtain revolutions of the engine. In the method a crank angle information is obtained during the revolutions of the engine, the crank angle information is calculated to speed and acceleration information, the speed and acceleration information is analysed in order to generate a correction value for control processing by taking into an account at least one limiter function of the engine, a fuel injection time is obtained for each cylinder, a fuel quantity value is obtained individually for each fired cylinder, said fuel quantity value and said fuel injection time are utilized to provide a history based initial injection quantity value individually for each cylinder, and revolutions of the engine are controlled by adding the correction value to the history based initial injection quantity value. The invention is based on that a crank angle signal is obtained by a measurement during the revolutions of the engine and this crank angle signal is calculated to speed and acceleration information. By taking into an account at least one limiter function of the engine, said speed and

acceleration information is analysed in order to generate a correction value for control processing. Fuel quantity value and fuel injection time are obtained to provide a history based initial injection quantity value individually for each cylinder, and revolutions of the engine are controlled by adding the correction value to the history based initial injection quantity value. The benefit of the invention is that the engine control works automatically and successfully with different revolutions and even at very low revolutions making the ship manoeuvring more precise and less complicated thus increasing safety and preventing for example oil accident disasters from occurring. Also the invention is economically advantageous to accomplish to different types of engines.

Short description of figures

Figure 1 presents a preferred speed control system according to the present invention.

Detailed description of the invention

The purpose of the invention is to provide an internal SCS (speed control system) for example for two stroke ship engines as an object to make manoeuvring easier and fuel consumption more economical when engines are run with different revolutions, from very low revolutions to very high revolutions, that is to say for example 5 - 200 rpm (revolutions per minute). Ships have often big two stroke diesel engines and especially for big ships these engines are low speed engines and thus a good controllability at low revolutions, and also at very low revolutions, is very important for example when low and stable running speeds are needed to ensure safety

manoeuvring.

In figure 1 is presented a preferred embodiment according to the present invention. An internal SCS for improving engine speed control properties is integrated into the ECS (engine control system) of a two stroke ship engine. This engine comprises at least two cylinders for burning fuel that is injected with fuel injection means 111 to said cylinders. The engine further comprises a piston in each cylinder for achieving a reciprocating linear piston motion as an effect of the burnt fuel and a crankschaft for translating reciprocating linear piston motions into a rotation movement to obtain revolutions of the engine.

The most important information for the SCS is the engine speed that information is provided to the SCS by a crank angle signal measurement. The internal SCS according to the preferred embodiment (fig. 1) comprises a crank angle sensor as means 100 for obtaining a crank angle signal during the revolutions of the engine. This is performed by detecting actual crankshaft positions by said crank angle sensor to obtain a crank angle information during the engine is running. The SCS comprises means for delivering the crank angle information to a crank angle information calculator 102 that calculates the crank angle signal to speed and acceleration information. These means for delivering are wired and/or wireless data transmission means. The calculation of the crank angle information to speed and acceleration information is based on a crank angle sector idea. This calculation is performed in crank angle information calculator 102 or in some other processor part of the SCS. The sector is one revolution divided by the number of cylinders and every sector stands for an individual cylinder. In every sector a mean value of the speed signal is calculated by the SCS and with the difference of the speed signals from two sectors the acceleration value can be calculated. With this calculation method a complex way of speed signal filtering can be avoided.

The preferred embodiment of the present invention in figure 1 comprises a crank angle information analyser 108 for further analyse of the speed and acceleration information to generate a correction value for control

processing. First, the crank angle signal analyser 108 processes said speed and acceleration information to form logic information comprising information about acceleration and/or speed characteristics. A speed set point

information is calculated in an engine driving control 110, that comprises information on target revolutions of the engine, is sent to the crank angle signal analyser 108 from the engine driving control 110. The calculated set point information is balanced with corresponding set point information from other cylinders to avoid a discrepancy which could cause an uneven running of the engine. Said logic information is then utilized with received speed set point information in crank angle signal analyser 108 to generate a correction value for control processing by taking into an account at least one limiter function of the engine. This corrected value has to be in set limits in order to prevent the engine of damages. These limits, set by the limiters, are part of the SCS and they are depending on the engine speed and a charge air pressure, that is measured by the charge air pressure measurement means 103.

The preferred embodiment of the present invention in figure 1 further comprises a fuel quantity meter 112 for metering a fuel quantity fl information of the last fired cylinder. The injected fuel quantity is measured for every fuel injection and cylinder. Other arrows f2, f3, f4... , in figure 1 present measured fuel quantities for previously fired cylinders. The fuel quantity meter 112, as presented in figure 1, is an independent

measurement unit. Also the fuel quantity meter 112 can be arranged for example so that it is integrated with the fuel injection means 111 to measure the fuel quantity injected to the next cylinder to be fired. The measured values fl, f2, f3, f4, are sent to the control processor 114 that uses this information to build up a history of the injected fuel quantities. The at least one measured fuel quantity value fl, f2, f3, f4 is utilized in a control processor 114 for calculating a fuel quantity used in the latest sector of the crank angle, i.e. preceding rotational sector of the crank angle, by utilizing a mathematical equation applicable for this calculation. An important factor calculated in the control processor 114 for controlling revolutions of the engine is the calculation of a fuel quantity needed in the next cylinder for obtaining target revolutions of the engine. This is performed so that with a weighting of the past injections the control processor 114 calculates a history based initial injection quantity value for the next crank angle sector.

The correction value, depending on the speed and acceleration of the engine, is added to the history based initial injection quantity value in the control processor 114 to determine an injection quantity set point. These calculations are preferably performed while the crank angle is not in the sector of the specific cylinder, whereas in the sector of said cylinder, the injection quantity set point is sent to the fuel injection means 111 and the fuel injection takes place. Also in the preferred embodiment of the invention, the calculated injection quantity set point is balanced with the ones calculated for the other cylinders to avoid a discrepancy which could cause an uneven running of the engine.

In said calculation in the control processor 114 can also be determined an effect factor of the latest firing effect on the engine revolutions and said effect factor can also be utilized in said controlling revolutions of the engine. The preferred embodiment (fig. 1) according to the invention also comprises a fuel quantity balancer 116 for performing a fuel quantity balancing function to even out working load between cylinders. The fuel quantity balancer 116 receives from the control processor 114 as information the calculated fuel quantity needed in the next cylinder for obtaining target revolutions of the engine and/or the calculated effect factor of the latest firing effect on the engine revolutions. The fuel quantity balancer 116 also receives from the control processor 114 calculated fuel quantity values (cl, c2, c3 in fig. 1), i.e. injection quantity set points of other cylinders. On the basis of said

calculated fuel quantity values from other cylinders and the calculated fuel quantity needed in the next cylinder for obtaining target revolutions of the engine and/or said calculated effect factor, the fuel quantity balancer 116 calculates a fuel quantity balancing information and then sends it to the fuel injection means 111 for performing a fuel quantity balancing function to even out working load between cylinders. Said fuel injection time for each cylinder is measured by means 101 for obtaining a fuel injection time for each said cylinder. These means 101 can be integrated to the control processor 114 or to the fuel injection means 111 or they 101 can be arranged also as a separate injection time measurement arrangement. From the injection means or from the separate injection time measurement arrangement the measured fuel injection time is then sent to the control processor 114. By combining and utilizing all or at least part of above mentioned different types of information, even a very precise engine revolution control can be achieved that makes possible to run the engine even at much lower revolutions than with the prior art external control systems.

In the crank angle information calculator 102, crank angle information analyser 108, control processor 114 and fuel quantity balancer 116 the invention can be implemented as a programmable software implementation. Also physically the crank angle information calculator 102, crank angle information analyser 108, control processor 114 and/or fuel quantity balancer 116 can be located in the same processor or in separate processors. There can be arranged a separate processor for every cylinder and the SCS is part of the software in each processor. Thus the engine utilizing the present invention is not dependent on one cylinder or not even two cylinders and the engine can be running even with up to two cylinders turned off, because there is no dominating central processor which can fail and cause a shut down. All functions according to the invention can be distributed between the separate processors in such a way that if one processor fails, or even more processors fail, the engine remains successfully in operation. Although the invention has been presented in reference to the attached figures and specification, the invention is by no means limited to those, as the invention is subject to variations within the scope allowed for by the claims.