Electromagnetic system of a fuel injection apparatus and drive circuit of the electromagnetic system therefor

Abstract: Using a control coil (11) having a high response characteristic suited to the valve opening and a hold coil (12) suited to hold a large force by a small current, during the valve opening time a high voltage is applied to the control coil suited to the valve opening and during a valve opening hold time a low and stabilized voltage is applied to the hold coil suite to the holding, and then a valve body driven. In a fuel injection apparatus, a drive manner during a valve opening time and a hold time is optimized.

Description: Background of the Invention: The present invention relates to an electromagnetic system fuel injection apparatus, and an internal combustion engine having an electromagnetic system fuel injection apparatus. In particular, it relates to an electromagnetic system fuel injector comprising at least two coils for driving a valve body. An electromagnetic system fuel injector (hereinafter, it is called as an injector) has a structure in which to a coil provided in an interior portion an electric voltage is applied, and according to a generated magnetic force a plunger is moved and a valve body is separated from a valve seat and then a fuel passage between the valve body and the valve seat is opened and then a fuel is injected from a fuel injection orifice. In the above stated injector, as a means for forcing the valve body to the valve seat a return spring member is provided, when the electric application to the coil is stopped, a magnetic attraction force against to the plunger is attenuated, and the fuel passage between the valve body and the valve seat is closed, namely the injector is closed. In Japanese-application patent laid-open publication No. Hei 8-326620, an electromagnetic system fuel injector is disclosed, in which two coils are provided and at an initial stage of a valve opening operation where a valve closing condition is shifted to a valve opening condition, in comparison with a time for hold the valve opening condition, to the two coils an electric voltage is applied. In this conventional injector, each of the above stated two coils is formed with the same size and the same configuration. In the above stated conventional injector, by applying the electric voltage to the two coils during the valve opening operation, the magnetic attraction force is made large and a valve opening delay can be shortened, and during the valve opening hold condition the magnetic attraction force is made small and the valve closing delay time can be shortened. In the conventional injector shown in Japanese application patent laid-open publication No. Hei 8-326620, as stated above there is not taken entirely into consideration the differences between the two coils as regards the electric characteristic of the respective two coils. For this reason, there are problems in which when it tries to assure a high speed response performance of the valve opening it is difficult to obtain a magnetomotive force necessary to maintain the valve opening condition, on the other hand when it tries to assure a stability performance during the valve opening condition hold time, it is difficult to obtain the high speed response performance. Accordingly, in the above stated conventional injector, it is not easy to make a design of a structure in which the high speed response performance is compatible with the stability performance during the valve opening condition hold time. US 4 355 619 discloses a fast response two coil solenoid driver used in a fuel injector. It comprises a pull-in coil and series-connected thereto a hold coil which may be energized separately. The pull-in coil may be of low inductance. The hold coil may be of high inductance. US 3 456 164 discloses a solenoid energizing means with data processing being identified as an exemplary field of use. A boost coil and a hold coil are provided and connected to separate power terminals. They may be switched by individual switching means. Summary of the Invention: An object of the present invention is to provide an electromagnetic system fuel injection apparatus wherein a drive force of a desirable characteristic of a valve body of the electromagnetic system fuel injection apparatus can be generated at an operation condition of the electromagnetic system fuel injection apparatus. To attain the above stated object, the electromagnetic system fuel injection apparatus according to claim 1 is provided. The thus provided two coils may have different winding number or may have a different length or may have a different cross-sectional area of wire material or may have a different electric resistance value between terminals. One of the coils which has a large time change rate of the magnetomotive force receives a high voltage, and the other coil receives a low voltage. A drive circuit for the first coil may have a switching means for performing an on and an off of an electric application of a first voltage and for the second coil may have a second switching means for performing an on and an off of an electric application of a second voltage lower than the first voltage. In the control circuit, at a valve opening operation initial stage of the valve body, to the first coil and the second coil to generate a magnet flux having same direction, the first voltage is applied to the first coil and the second voltage is applied to the second voltage, and after that only to the second coil the second voltage is applied. In the above stated electromagnetic system fuel injection apparatus, a circuit means for regulating the second voltage is provided. In the above stated electromagnetic system fuel injection apparatus, the drive circuit may be installed in an interior portion of an engine control unit which controls an operation condition of an internal combustion engine. Further to attain the above stated object, the electromagnetic system fuel injection apparatus may be part of an internal combustion engine that further has a fuel supply means for supplying the fuel to the fuel injection apparatus, a cylinder for burning the fuel injected by the fuel injection apparatus in an interior portion, a fuel injection apparatus, an air intake means for inhaling an air to the cylinder, an ignition means for igniting an air-fuel mixture to the cylinder, an air exhaust means for exhausting an exhaust gas from the cylinder, and an engine control unit for controlling the air intake means, the air exhaust means, an ignition means and the fuel injection apparatus. Further an electromagnetic system fuel injector has a fuel injection orifice, a seat valve provided upstream of the fuel injection orifice, a valve body for performing an opening and closing of a fuel passage between the valve seat, and at least two coils for generating a drive force of the valve body. In the electromagnetic system fuel injector, a first coil has a large time change rate of a magnetomotive force which is a product of a winding number and a current value, and a second coil has a smaller time change rate of the magnetomotive than that of the first coil. Brief Description of the Drawing: Fig. 1A is a cross-sectional view showing an electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 1B is a view showing a connector portion of the electromagnetic system fuel injection apparatus of one embodiment shown in Fig. 1A according to the present invention; Fig. 2A is an appearance view showing a bobbin to which two coils of the electromagnetic system fuel injection apparatus are wound used in one embodiment according to the present invention; Fig. 2B is a plan view showing the bobbin of the electromagnetic system fuel injection apparatus of one embodiment shown in Fig. 2A according to the present invention; Fig. 3 is a view showing an equivalent circuit of the electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 4A is a graph showing a current characteristic of a control coil and a hold coil of the electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 4B is a graph showing a magnetomotive force response characteristic of the control coil and the hold coil of the electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 5 is a view showing a circuitry wiring construction of the electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 6 is a graph showing an injector drive manner of the electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 7A is a view showing a simple model of the electromagnetic system fuel injection apparatus according to the present invention; Fig. 7B is a view showing a simple model of a high voltage drive electromagnetic system fuel injection apparatus according to the prior art; Fig. 7C is a view showing a comparison in cost and size between the high voltage drive electromagnetic system fuel injection apparatus according to the prior art and the electromagnetic system fuel injection apparatus according to the present invention; Fig. 8 is an outline view showing an internal combustion engine having the electromagnetic system fuel injection apparatus of one embodiment according to the present invention; Fig. 9A is a schematic view of an electromagnetic system fuel injection apparatus of an embodiment that does not form part of the present invention; Fig. 9B is a circuitry view of the electromagnetic system fuel injection apparatus of the embodiment shown in Fig. 9A; Fig. 10A is a graph showing a current characteristic of the electromagnetic system fuel injection apparatus of this embodiment; Fig. 10B is a graph showing a magnetomotive force characteristic of the electromagnetic system fuel injection apparatus of this embodiment; Fig. 10C is a graph showing a drive manner of the magnetomotive force characteristic of the electromagnetic system fuel injection apparatus of this embodiment; Fig. 11A is a circuitry view showing a mutual induction electromotive force and an equivalent circuit of a control coil and a hold coil of the electromagnetic system fuel injection apparatus of an embodiment that does not form part of the present invention; Fig. 11B is a circuitry view showing a reverse current path of the control coil and the hold coil of the electromagnetic system fuel injection apparatus of an embodiment that does not form part of the present invention; Fig. 12A is a view showing a throw-in current in a circuit having no reverse current prevention diode; Fig. 12B is a view showing a throw-in electromagnetic force in a circuit having no reverse current prevention diode; Fig. 13A is a view showing a throw-in current in a circuit having a reverse current prevention diode; and Fig. 13B is a view showing a throw-in electromagnetic force in a circuit having a reverse current prevention diode. Description of the Invention: Hereinafter, an electromagnetic system fuel injection apparatus and an internal combustion engine having an electromagnetic system fuel injection apparatus of one embodiment according to the present invention will be explained referring to drawings. Fig. 1A shows a side cross-sectional view of an electromagnetic system fuel injection apparatus (an injector) 10 of this-embodiment according to the present invention and Fig. 1B is a view taken from a left direction (a connection terminal face side of a connector) of the drawing of a connector portion of the injector 10. Fig. 2A shows an appearance view taken from a side portion of two coils comprised of a control coil and a hold coil which are wound to a bobbin provided in the injector 10 and Fig. 2B is a view taken from an upper portion (an opposite side of a fuel injection orifice of the injector 10 along to in a direction of a shaft center of the valve) of the drawing of the bobbin of Fig. 2A. Fig. 3 is a view showing an equivalent circuit model of the injector 10 of this embodiment according to the present invention. First of all, a structure of the injector 10 of this embodiment according to the present invention will be explained referring to Fig. 1A and Fig. 1B. To the injector 10 of this embodiment according to the present invention, a fuel which is pressurized by a fuel pump is supplied and an opening and a closing of a fuel passage is carried out between a ball valve 16 forming a valve body and a seat face (a valve seat face) 4 formed in a side of a nozzle 3, and an injection amount of the fuel from a fuel injection orifice 5 which is formed at a side of a downstream of the seat face 4 is controlled. The ball valve 16 is installed at the tip end of a plunger 15. Upstream of the seat face 4 a swirler (a fuel swirling element) is provided in which the fuel passage gives a swirling force to the fuel. Using this swirler 17, an atomization of the fuel which is injected from the fuel injection orifice 5 is promoted. To drive this ball valve 16, a control coil 11 and a hold coil 12 are provided to the injector 10. When the control coil 11 and the hold coil 12 are supplied with electric voltage, a magnetic flux is generated. This passes through a core 13, a yoke 14, and the plunger 15 as a magnetic path, and an attraction force is generated between the core 13, the yoke 14, and the plunger 15. Accordingly, the plunger 15 and the ball valve 16 are displaced to an upper side (a direction for separating apart from the seat face 4) in this figure and the fuel passes through the fuel passage which is opened between the seat face 4 and the ball valve 16 and the fuel is injected from the fuel injection orifice 5. Further, when an attraction force to the injector 10 does not existed from the control coil 11 and the hold coil 12, to close the valve by pushing the plunger 15 and the ball valve 16 against to the seat face 4, a forcing means is provided. In this embodiment according to the present invention, as the forcing means a return spring member 18 being a spring member is provided. As shown in Fig. 1A, Fig. 1B and Fig. 2A and Fig. 2B, the control coil 11 and the hold coil 12 are wound on a bobbin 7. Both ends of the control coil 11 penetrate the bobbin 7 and are led to an upper side of a connector 6 through long terminals 33 and 34, and these long-terminals 33 and 34 form C+ terminal and C- terminal. Both ends of the hold coil 12 penetrate the bobbin 7 and are led to a lower side of a connector through short terminals 31 and 32, and the short terminals 31 and 32 form H+ terminal and H- terminal. To H+ terminal and C+ terminal, a positive voltage is applied and H terminal and C- terminal are connected to a minus terminal of a battery 2. For the control coil 11 and the hold coil 12, to generate a magnetic flux in an equal direction, a winding manner and a wiring manner of the control coil 11 and the hold coil 12 are determined. As shown in Fig. 3, an injector portion of this embodiment according to the present invention is shown as an equivalent circuit to which the control coil 11 and the hold coil 12 are wound. Hereinafter, the wiring manner and the current direction etc. of the injector 10 are explained by showing the equivalent circuit model shown in Fig. 3. In the injector 10 of this embodiment according to the present invention, as stated above, the injector 10 has two coils which are the control coil 11 and the hold coil 12. In the control coil 11 being a first coil, it is unnecessary to take into consideration the magnetomotive force necessary to maintain the valve opening condition. But the raising characteristic of the magnetomotive force must be considered. On the other hand, the hold coil 12 being a second coil can generate the magnetomotive force necessary to maintain the valve opening condition at a time where the valve opening condition is assured to some degree and it is unnecessary to consider a high speed raising characteristic. In the injector 10 of this embodiment according to the present invention, the control coil 11 and the hold coil 12 are constituted to have different electric characteristics. The control coil 11 has a small winding number (an inductance) and a small electric resistance. On the other hand, the hold coil 12 has a large winding number and a large electric resistance. Further, in detail, the control coil 11 has a shorter length of a wire material and a large cross-sectional area against to those of the hold coil 12, and then the control coil 11 has the small electric resistance. The control coil 11 and the hold coil 12 have different roles in the respective stages of valve opening, valve opening hold, and valve closing. The control coil 11 is, in the injector 10 of this embodiment according to the present invention, a coil which is used exclusively at the valve opening initial condition, and the hold coil 12 is a coil which is used at the valve opening hold condition. Hereinafter, the current characteristic of the control coil 11 and the hold coil 12 will be explained. Fig. 4A is a view showing the current - over - time characteristics of the control coil 11 and the hold coil 12 in a case that the same voltage V is applied. As stated above, since the control coil 11 has the small winding number and the small resistance, in a short time it can reach the large current value. On the other hand, since the hold coil 12 has the large winding number and the large resistance, it takes time for reaching the current value. Further, the convergence value of the hold coil 12 is smaller than that of the control coil 11. On the other hand, Fig. 4B is a view showing the magnetomotive force response which affects to a magnetic circuit of the respective coils 11 and 12. The magnetomotive force is expressed by a product of the coil winding number with the current value and this is considered as a physical value which exerts an influence directly as the magnetic attraction force. As shown in Fig. 4B, the current which flows into the control coil 11, is raised abruptly, but since the winding number is small, the convergence value of the magnetomotive force in the control coil 11 is not larger than the difference in the current value in comparison with those of the hold coil 12. Inversely, the magnetomotive force response of the hold coil 12 is shower than that of the control coil 11. During the valve opening operation time, since a set load according to the above stated return spring member 18 and a fuel pressure according to the pressurized fuel act on the ball valve 16, compared with the valve opening hold time a large electromagnetic attraction force is required. When the electromagnetic attraction force reaches after a time the largeness which overcomes these forces, at first the plunger 15 starts displacement. As a result, since a time necessary to generate the electromagnetic attraction force contributes to the valve opening delay, it is necessary to shorten it as much as possible. To perform the above, it is effective to apply a high voltage as much as possible to the control coil 11. When an automobile has two power supply systems of 42V of a high voltage power supply and 14V of a low and a stabilization power supply, it is desirable to drive the control coil 11 by 42V high voltage power supply. Further, in the coil used for the valve opening operation, it is effective to obtain the magnetomotive force by the current rather than by the winding number. In a case of the control coil 11 having the small winding number, since the inductance and the interior portion resistance are small, the current can flow easily. Namely, it is desirable to have the characteristic of the control coil 11 which is used in a peak hold system. Further, the easy flowability of the current is affected by not only the control coil 11 in the injector 10 but also by an interior portion of a drive circuit, a resistance of a switching device and a drop in voltage. As a result, it is necessary to make as small as possible the interior portion of the drive circuit, the resistance of the switching device and the drop in voltage. On the other hand, at the valve opening hold operation of the injector 10, in comparison with the valve opening, a smaller magnetomotive force can hold the valve body in the open condition. This is because when the valve is open, the fuel is injected and at upstream side and a downstream side of the ball valve 16 the pressure is balanced, so that the force by the fuel pressure is made small. At the same time since an air gap between the core 13, the yoke 14 and the plunger 15 becomes small, the magnetic flux density of the air gap is raised and the magnetomotive force can be used effectively. Further, at the time of the valve closing of the injector 10 after the valve opening hold, the voltage application is stopped. Then the magnetomotive force during the valve opening hold time lowers, and when it becomes lower than the set load of the spring member 18, the valve closing operation in the injector 10 starts. But when the magnetomotive force during the valve opening hold time is excessively large, it contributes to the valve closing delay. Accordingly, during the valve opening hold of the injector 10, it is necessary to hold with a low magnetomotive force which is near to the stable hold limit. To obtain this, the application of a stable low voltage to the injector 10 is effective. To generate the stable attraction force of the injector 10, it is desirable to drive it by a stable power supply and to use a coil characteristic in which the current change is slow. To obtain this, it is desirable to use the coil characteristic in a saturated state in which the current control circuit is unnecessary. Further, during the valve opening hold time in which the response performance of the attraction force is not required, it is unnecessary to heighten the applied voltage. In the valve opening hold condition of the injector 10, the consumed power electric is a value in which the square of the applied voltage is divided by the coil resistance. The coil resistance is proportional to the winding number of the coil and is inversely proportional to the wire diameter of the coil. However there are limitations to the increase of the winding number and the thinness of the wire diameter. To saturate actually the wire diameter and the copper wire, during the valve opening hold condition it is desirable to apply a lower voltage than the voltage which is applied during the valve opening time. During the valve opening hold time of the injector 10, when the voltage which is applied to the coil fluctuates, it is necessary that the coil generates the attraction force which holds the valve open at the minimum voltage within the fluctuation range. Then, however, at average values in the fluctuation range or at the maximum voltage, the attraction force becomes excessively large. Further, when heat generation is considered, it is necessary to select the coil to not overheat at the maximum voltage in the fluctuation range. However, at the maximum voltage in the fluctuation range the attraction force is excessive, this excess being unnecessary attraction force, and it is necessary to select the coil to not generate heat excessively. As a result, it is desirable to have a small fluctuation range and to stabilize the voltage applied to the coil during the valve opening hold time. Accordingly, the coil is optimized under the attraction force aspect and the thermal aspect. When an automobile has two power supplies comprised of 42V high voltage power supply and 14V low voltage and stabilized power supply, during the valve opening hold time of the injector 10 it is desirable to use the power supply in which this 14V low voltage being lower than 42V high voltage is stabilized. On the other hand, during the valve opening time of the injector 10, it is necessary to attenuate abruptly the magnetic force, in this case it is desirable to employ the coil characteristic which is used in the peak hold system. Fig. 5 is a view showing a circuitry wiring constitution of the electromagnetic system fuel injection apparatus of this embodiment according to the present invention in which the above stated driving is enabled to operate. As stated in above, in the case where to the automobile the two power supply systems, for example the respective comprised of the power supply of the high voltage of 42V for a battery 22 and the power supply of the low voltage of 14V for the battery 2 are provided, to the control coil 11 it is effective to apply the voltage from a first voltage (for example 42V) having the high voltage. To the hold coil 12 it is effective to apply the voltage from a second voltage (for example 14V) having the low voltage. In view of the functional requirements of the control coil 11, the hold coil 12, the first power supply, and the second power supply, it is possible to optimize the respective parameters such as the coil winding number, the coil resistance, and the coil wire diameter. In this time, it is desirable to stabilize the second power supply voltage having the low voltage. As a result, by the stable attraction force, it is possible to hold the valve body and further it is possible to stabilize the injection amount characteristic of the injector 10. The electromagnetic system fuel injection apparatus of this embodiment according to the present invention is constituted by the injector 10 and a drive circuit 100 for driving the injector 10. According to the circumstances, it can include a control circuit for controlling the injection timing of the injector 10. Further, commonly the control circuit is provided in an interior portion of an engine controller (an engine control unit: ECU) 1. To the injector drive circuit 100, two voltages of voltage VH which is generated by an alternator 30 and voltage VL which is stabilized by the low voltage being lower than the voltage VH by DC/DC converter 40 are supplied. In accordance with an injection command signal from the engine controller (the engine control unit: ECU) 1, the voltage application to the control coil 11 and the hold coil 12 is carried out. The injector drive circuit 100 has a control coil transistor module 110 which carries out the electric application control to the control coil 11 and a hold coil transistor module 120 which carries out the electric application control to the hold coil 12. The respective transistors 110 and 120 of the injector drive circuit 100 are constituted by power transistors 111 and 121, and surge absorbing diodes 112 and 122. When the control coil power transistor 111 is switched to an "on" state, to the control coil 11 the high voltage VH is applied. When the hold coil power transistor 121 is switched to an "on" state, to the hold coil 12 the stabilized low voltage VL is applied. These voltages are applied to the control coil 11 and the hold coil 12. The magnetic flux generates in the same direction to the control coil 11 and the hold coil 12 and the magnetic circuit and then a force for attracting the plunger 15 works on. Fig. 6 shows a diagram of an injector drive manner of the electromagnetic system fuel injection apparatus of this embodiment according to the present invention. During the injection command signal having a length Ti, to the control coil 11 over a length Tc (< Ti), the high voltage VH is applied, and at a short time the large magnetomotive force is built up and the valve opening of the injector 10 is promoted. On the other hand, to the hold coil 12, the low voltage VL which is stabilized at a time of the injection command signal (Ti) is continued to be applied, when the injection command signal is raised, at the same time the application of the stabilized low voltage VL is made to stop. Since the electromagnetic system fuel injection apparatus is held by the stabilized low voltage VL and the low magnetomotive force which is near to the hold limit, when the voltage VL application is made to stop, the valve body is beginning immediately the valve closing operation of the injector 10. As shown in Fig. 7A, in the electromagnetic system fuel injection apparatus of this embodiment according to the present invention, a characteristic in which the winding number is small, a large current flows in short time and the high speed response is given to the control coil 11, and to this control coil 11 the high voltage VH is applied. Further, as shown in Fig. 7A, in the electromagnetic system fuel injection apparatus of this embodiment according to the present invention, a characteristic in which with a small current the stabilized attraction force is generated is given to the hold coil 12, and to this hold coil 12 the stabilized low voltage VL is applied. In the respective stages of the valve opening operation of the injector 10 and the valve opening hold condition of the injector 10, since with the ideal coil characteristic the ideal voltage is combined, it is possible to carry out the optimum operation of the injector 10. On the other hand, Fig. 7B shows the operation of a high voltage drive electromagnetic system fuel injection apparatus according to the prior art. In the high voltage fuel injector using one coil, since it is necessary to hold the valve opening operation and the valve opening condition, it is difficult to obtain the ideal characteristic in the respective stages. For example, if for obtaining the good response performance during the valve opening operation time, similarly to the control coil 11 of this embodiment according to the present invention, the coil winding number is small and the coil resistance is small, then during the valve opening hold time, since it is necessary to continue to flow the large current, the heat generation becomes to excess. Inversely, if the winding number and the resistance are formed like those of the hold coil 12 of this embodiment according to the present invention, then it is impossible to carry out the valve opening and the valve opening delay becomes very large. For these reasons, the coil should be designed as a compromise. In the high voltage drive fuel injector according to the prior art, the very large voltage VHH (>> VH) is made from a battery using a step-up circuit 202, and this voltage is applied to the coil and the current is raised abruptly and the valve opening is carried out. After the valve opening of the injector, even a battery voltage VL' (<< VHH) is applied directly, since otherwies the current is excessive. According to a current control circuit 203 a switching is operated. To form the current value constant within the hold limitation a current control is added. Circuitry of the step-up circuit 202 and the current control circuit 203 is large, and it is impossible to arrange them in the conventional engine control unit. For these reasons, in the high voltage drive fuel injection apparatus according to the prior art, the injector drive circuit 210 is arranged separately from the engine controller (the engine control unit: ECU) 201. Due to the separate arrangement of the injector drive circuit 210 and the engine controller 201, in the fuel injector drive circuit 210 it is necessary to provide a case. Further, to exchange signals with the engine controller 201, it is necessary to provide a harness 204 and a connector 205. Further, according to the switching noises during the current control circuit drive time, to not give an influence to the engine controller 201 or a radio, etc. it is necessary to use a high cost shield wire. Herein, as shown in Fig. 5, since the drive circuitry of the electromagnetic system fuel injection apparatus of this embodiment according to the present invention is constituted basically by ON/OFF circuitry having two power transistors, it is very low cost and is compact. Further, since the switching operation is unnecessary, noises do not occur. As a result, it is possible to arrange the injector drive circuit 100 in the interior portion of the engine controller (the engine control unit) 1. Fig. 7C shows a view of cost and size of the high voltage fuel injection apparatus according to the prior art and the electromagnetic system fuel injection apparatus of this embodiment according to the present invention are compared. According to the electromagnetic system fuel injection apparatus of this embodiment according to the present invention, the step-up circuit and the current control circuit shown in the prior art can be abolished and the circuitry can be made smaller than that of the prior art. Further, in this embodiment according to the present invention, the case, the harness, and the connector shown in the prior art can be unnecessary. As a result according to this embodiment according to the present invention it is possible to obtain a large cost reduction and a small size structure in the injector 10. In the fuel injector of this embodiment according to the present invention, the voltage VL which is applied to the hold coil 12 is stabilized, whereas the voltage VL is not stabilized, by the drives of the control coil 11 and the hold coil 12 suited to the respective stages of the valve opening operation and the valve opening hold of the injector 10. With the drive voltages suited to the respective stages, it is possible to realize the optimum drive. Further, to attain the cost reduction of the whole electromagnetic system fuel injection apparatus, in this system according to the present invention it does not change or does not stabilize the power supply voltage, however it may use only the power supply which is supplied from the automobile. One embodiment of an internal combustion engine to which the electromagnetic system fuel injection apparatus of this embodiment according to the present invention is adopted will be explained referring to Fig. 8. The internal combustion engine of this embodiment according to the present invention shown in Fig. 8 comprises a fuel injection apparatus (an electromagnetic system fuel injector 110, a drive circuit 1100) for injecting fuel, and a fuel supply apparatus (a fuel pump 1030, a feed pump 1040, a high pressure regulator 1050) for supplying the fuel to the fuel injection apparatus. The internal combustion engine further comprises a cylinder 1060 in which at an interior portion the injected fuel is burned, a piston 1070 for reciprocating in the cylinder 1060, an air intake means 1080 for inhaling air into the cylinder 1060, an ignition apparatus 1090 for igniting an air fuel mixture in the cylinder 1060, an air exhaust means 1110 for exhausting the air from the cylinder 1060, and an engine control unit 1 for controlling the air intake means (an air intake conduit, a valve, etc.) 1080, the air exhaust means (an air exhaust conduit, a valve, etc.) 1100, the ignition apparatus 1090, and the fuel injection apparatus. Further, a generator 30 which generates power by receiving motive force from the internal combustion engine and DC/DC convertor 40 are provided. The voltage of 42V from the generator 30 and the voltage of 14V which is converted and stabilized by DC/DC convertor 40 are supplied to the drive circuit 1100. In this internal combustion engine having the fuel injection apparatus, fuel is led to the fuel pump 1030 through the feed pump 1040 and the fuel passes through a check valve 1120 and supplied to the injector 1010 under pressurized condition. The engine controller 1 determines the injection timing and the injection amount from the information of various kinds of sensors, and the injection signal is outputted to the injector drive circuit 1100, and then the injector 1010 is driven by the drive circuit 1100, and the fuel is injected. In this embodiment according to the present invention using a direct injection system internal combustion engine is explained. However, other kinds of internal combustion engines may be used naturally. According to the internal combustion engine of this embodiment according to the present invention, a fuel injection apparatus which realizes stably a wide dynamic range can be provided at a low cost. The fuel injector and the drive circuit system of the fuel injector will be explained. As the fuel injector and the drive circuit system of the injector, it will well known the saturated system (the voltage drive) and the peak hold system (the current drive). In commonly in the saturated system, the coil winding number is large, the drive current is continued to increase after the lift of the valve body is finished, and it becomes closely to the saturated current value which is limited by the coil interior portion resistance and the resistance of the drive circuit. A circuit impedance is high compared with that of the peak hold system, and by the influence of the inductance the raising of the current which flows in the coil is moderately. According to the adjustment of the coil interior portion resistance and the resistance of the drive circuit, when the saturated current value is established suitably, the current control circuit is unnecessary and it can contribute to cost reduction. On the other hand, in the peak hold system, the coil winding number is small, the circuit inductance and the circuit impedance are low, the rising of the current during the valve opening time is rapid compared with that of the saturated system. However, with this condition, since the over-current flows and the coil is burned and damaged, the current control mechanism is provided in the drive circuit and after the full lift the current is limited to the value necessary for the valve opening hold. To attain the high injection rate which becomes as a performance standard of the injector and the wide dynamic range, there are many cases in which the peak hold system having the high current response performance is employed. Further, by the step-up circuit the high voltage is formed and applied to the injector, and the current flows in short time, so that it is possible to improve the valve opening raising characteristic. Further, during the valve opening time, this high voltage is applied and then it is possible to improve the valve closing characteristic of the injector. According to the above stated embodiment according to the present invention, since at least two coils having different electric characteristics are provided and to the control coil and the hold coil suitable power supply voltages are applied, the desirable characteristic drive force of the valve body against to the operation condition of the injector can be generated, and accordingly a good fuel injection can be realized. Next, a drive circuit of an electromagnetic fuel injector of an embodiment which does not form part of the present invention will be explained referring to the drawings. Fig. 9A is a schematic view showing a structure of an injector 10a and Fig. 9B is a view showing a wiring structure of an injector drive circuit 100a of a further embodiment. Using Fig. 9A, the structure of the injector 10a of will be explained. A fuel which is pressurized by a fuel pump is supplied and an opening and a closing of fuel passage is carried out between a ball valve 16a forming a valve body and a seat face (a valve seat face) 19a which is formed in a side of a nozzle. An injection amount of the fuel from a fuel injection orifice which is formed at a side of a downstream of the seat face 19a is controlled. The ball valve 16a is installed to a tip end of a plunger 15a. In the vicinity of the valve seat face 16a a swirler 17a for atomizing the fuel is provided. To drive this ball valve 16a, a control coil 11a and a hold coil 12a are provided to the injector 10a. When the control coil 11a and the hold coil 12a are supplied with electric voltage, a magnetic flux is generated. It passes through a core 13a, a yoke 14a, and the plunger 15a as a magnetic path. An electromagnetic attraction force is generated between the core 13a, the yoke 14a, and the plunger 15a. Accordingly, the plunger 15a and the ball valve 16a are displaced towards the right side in Fig. 9A and the fuel is injected. Further, to the injector 10a, when no attraction force comes from the control coil 11a and the hold coil 12a, to close the valve by pushing the plunger 15a and the ball valve 16a against the valve seat face 19a, a return spring member 18a being a spring member is provided. One end of the control coil 11a forms B1 terminal and another end of the control coil 11a forms C terminal and one end of the hold coil 12a forms B2 terminal and another end of the hold coil 12a forms H terminal. To B1 terminal and B2 terminal, a positive terminal of a battery 2a is connected, and C terminal and H terminal are connected to a minus terminal of the battery 2a. For the control coil 11a and the hold coil 12a, to generate a magnetic flux in an equal direction, a coil winding manner and a coil wiring manner of the control coil 11a and the hold coil 12a are determined. Next, using Fig. 9B, the wiring structure of the injector drive circuit 110a will be explained. As to the injectors 10a, this injector 10a comprise the control coil 11a and the hold coil 12a, and the control coil 11a and the hold coil 12a have a different electric characteristic. The control coil 11a has a small winding number (inductance) and a small electric resistance. On the other hand, the hold coil 12a has a large winding number and a large electric resistance. To the injector drive circuit 100a, from the battery 2a a battery voltage is supplied, and in accordance with an injection command signal from an engine controller 1a, the electric voltage is applied to the control coil 11a and the hold coil 12a. The injector drive circuit 100a has a control coil transistor module 110a which carries out the electric voltage control to the control coil 11a and a hold coil transistor module 120a which carries out the electric voltage control to the hold coil 12a. The respective transistors 110a and 120a are constituted by power transistors 111a and 121a, and surge absorbing diodes 112a and 122a. When the hold coil power transistor 111a and the control coil power transistor 121a are switched to an "on" state, to the hold coil 12a and the control coil 11a, the voltages from the battery 2a are applied. Further, at the hold coil 12a a reverse flow prevention diode 130a is provided. This reverse flow prevention diode 130a is wired to have a polarity in which the current of the hold coil 12a is prevented to flow reversely from H terminal to B2 terminal. The control coil 11a and the hold coil 12a have different roles in the respective stages of valve opening, valve opening hold, and valve closing of the injector 10a. The control coil 11a is, in this embodiment used exclusively at the valve opening initial condition, and the hold coil 12a is a coil which is used at the valve opening hold condition. Hereinafter, the current characteristic of the control coil 11a and the hold coil 12a will be explained. Fig. 12A is a view showing the current over time characteristics-flowing in the control coil 11a and the hold coil 12a in a case that the same voltage is applied. As stated above, since the control coil 11a has a small winding number and a small resistance, it can reach in a short time a large current value. On the other hand, since the hold coil 12a has a large winding number and a large resistance, it takes time for reading the current value. Further the convergence value is smaller than that of the control coil 11a. On the other hand, Fig. 12B is a view showing the magnetomotive force response which affects a magnetic circuit of the control coil 11a and the hold coil 12a. The magnetomotive force is expressed by a product of the coil winding number with the current value and this is considered as a physical value which exerts an influence directly upon to the magnetic attraction force. As shown in Fig. 12B, the current which flows in the control coil 11a is raised abruptly, but since the winding number is small, the convergence value of the magnetomotive force is not larger than the difference in the current value in comparison with those of the hold coil 12a. Inversely, the magnetomotive force response of the hold coil 12a is slower than that of the control coil 11a. During the valve opening operation time of the injector 10a, since a set load of the return spring member 18a and a fuel pressure of the pressurized fuel act on the ball valve, compared with the valve opening hold time a large electromagnetic attraction force is required. When the electromagnetic attraction force reaches after a time the largeness which overcomes these forces, at first the plunger 15a starts displacement. As a result, since the time necessary to generate the electromagnetic attraction force contributes to the valve opening delay, it is necessary to shorten it as much as possible. On the other hand, at the valve opening hold operation, in comparison with the valve opening, a smaller magnetomotive force can hold the valve body in the open condition. This is because when the valve is open, the fuel is injected, and before and after the ball valve the pressure is balanced so that the force by the fuel pressure is made small. At the same time since an air gap between the core 13a, the yoke 14a and the plunger 15a becomes small, the magnetic flux density of a space gap is raised and the magnetomotive force can be used effectively. Further, at the time of the valve closing after the valve opening hold, the voltage application is stopped. Then the magnetomotive force during the valve opening hold time lowers, and when it becomes lower than the set load of the spring member 18a the valve closing operation starts to operate. But when the magnetomotive force during the valve opening hold time is excessively large, it contributes to the valve closing delay. Accordingly, during the valve opening hold, it is necessary to hold with a low magnetomotive force which is near to the hold limit. As stated above, at the valve opening initial stage and the valve opening hold condition, different magnetomotive force characteristic are required. In the injection drive circuit of this embodiment, as shown in Fig. 10C, during the injection command signal having a length Ti, to the control coil at a length Tc (< Ti), the high voltage is applied and at a short time the large magnetomotive force is applied and the valve opening of the injector 10a is promoted. On the other hand, to the hold coil 12a, the voltage is continued to be applied at a time of the injection command signal (Ti). When the injection command signal is turned off, at the same time the application of the voltage is made to stop. Accordingly, at the valve opening time, the characteristic required for the coil is provided by the control coil 11a, and at the valve opening hold time, the characteristic required for the coil is provided by the hold coil 12a, and by changing over simply at the respective stages of the valve opening operation and the valve opening hold condition, it is possible to carry out the ideal operation. Herein, Fig. 10C shows a current response in a case where the control coil 11a and the hold coil 12a are applied singly. In actually, since the control coil 11a and the hold coil 12a are arranged to close the same magnetic circuit (the yoke, and core), between the control coil 11a and the hold coil 12a, a mutual inductance works on. This mutual inductance works toward a direction from which the respective magnetomotive force change is prevented. For example, when to the control coil 11a the battery voltage is applied, when the control coil current is raised abruptly, to the hold coil 12a as a transfer effect according to the mutual inductance an induction magnetomotive force which is proportional to a time change of the control coil current is generated to the both ends of the control coil 11a and the hold coil 12a (between B2 terminal and H terminal). When this is shown in a circuitry view it becomes to Fig. 11A. On the other hand, the respective transistor modules of the control coil 11a and the hold coil 12a is constituted by the power transistors and the surge absorbing diodes. Accordingly, regardless of the on and the off of the power transistors, a circuit of reverse flow of the hold coil 12a is constituted. Both coil power transistors at the valve opening initial time are switched to the "on" condition, so that in both directions the circuit is closed, and as a result a short circuit condition shown in Fig. 11A appears. Herein, as a comparison to make clearly the effects according to the present invention, as shown in Fig. 11B, it is supposed that the reverse flow prevention diode 130a does not exist. When the minus magnetomotive force according to the above stated mutual induction is larger than the battery voltage, the reverse flow phenomenon shown in an arrow mark shown in Fig. 11B is generated. At the valve opening initial condition in which the voltage is applied to both the control coil 11a and the hold coil 12a together, the hold coil current flows reversely from H terminal to B2 terminal, and further via B1 terminal the current flows into the control coil 11a. Since the battery voltage is applied to the control coil 11a, in the control coil 11a a compound current of the current from the battery and the reverse current from the hold coil 12a flows, so that an apparent current increases. However, the reverse current at the hold coil 12a negates the magnetomotive force which is applied to the magnetic circuit, and further since the coil winding number of the hold coil 12a is larger than the coil winding number of the control coil 11a, the minus part of the magnetomotive force becomes remarkably. Fig. 12A shows the control coil current and the hold coil current in the case where the drive circuit without the reverse flow diode is driven, and Fig. 12B shows the build-up of the electromagnetic force at the control coil 11a, at the hold coil 12a and a compound value thereof. At the control coil electric application time Tc, since the control coil current raises abruptly, at the hold coil 12a the minus induction magnetomotive force generates. According to the reverse current prevention diode 130a the current and the magnetomotive force do not become minus, but become zero. To the control coil, the current from the hold coil 12a does not flow. Compared with the non-existence of the reverse flow prevention diode, the maximum value thereof is made small. Further, the raising of the electromagnetic force of the hold coil side after the finish of the control coil electric application can be improved. As stated above, by the insertion of the reverse flow prevention diode 130a in the injector 10a, it is possible to improve the build-up effect of the electromagnetic force, and the valve opening delay shortening and a safe hold can be realized. In this embodiment, in the drive circuit of the injector having the control coil 11a and the hold coil 12a, only at the hold coil the reverse flow prevention diode is exemplified. However, also at the control coil the reverse flow prevention diode can be inserted. In the drive circuit of an injector having more than three coils, by the insertion of the reverse flow prevention diode to the drive circuit line of the coil in which the reverse flow generates, it is possible to improve the build-up of the electromagnetic force. In this embodiment, to the control coil 11a and the hold coil 12a from the battery the voltage is applied directly. However, also stepping-up voltage or the stepping-down voltage may be used. In the electromagnetic system fuel injection apparatus having plural coils, a drive circuit is provided in which a reverse currents do not flow in a direction in which the magnetic fluxes weaken each other according to the mutual induction of the control coil and the hold coil, and since the build-up efficiency of the electromagnetic force is improved, valve opening delay shortening and a safe hold can be realized.

Claims: An electromagnetic system fuel injection apparatus comprising an electromagnetic system fuel injector (10) and a drive circuit (100) for driving said electromagnetic system fuel injector, wherein said electromagnetic system fuel injector has at least two coils (11, 12), and said two coils (11, 12) have different time change rates of a magnetomotive force, characterized in that to one of said coils a high voltage from a first power supply (22) is applied, and to the other of said coils a low voltage from a second power supply (2) is applied. The apparatus of claim 1, wherein said two coils (11, 12) have a different winding number. The apparatus of claim 1, wherein said two coils (11, 12) have a different length. The apparatus of claim 1, wherein said two coils (11, 12) have a different cross-sectional area of wire material. The apparatus of claim 1, wherein said two coils (11, 12) have a different electric resistance value between terminals. The apparatus according to any one from claim 1 to claim 5, wherein to one of said at least two coils which has a large time change rate of said magnetomotive force a high voltage is applied, and to another of said at least two coils which has a small time change rage of said magnetomotive force a low voltage is applied. The apparatus according to claim 1, wherein said injector has a fuel injection orifice (5), a valve seat (4) provided upstream of said fuel injection orifice, a valve body (3, 16) for performing an opening and closing of a fuel passage between said valve seat, wherein said two coils (11, 12) generate a drive force of said valve body, a first coil (11) of said coils having a large time change rate of a magnetomotive force which is a product of a winding number and a current value, and a second coil (12) of said coils having a smaller time change rate of said electromotive than said first coil, and said drive circuit has for said first coil (11) a switching means (110) for performing an on and an off of an electric application of a first voltage (22), and for said second coil a second switching means (120) for performing an on and an off of an electric application of a second voltage (2) lower than said first voltage. The apparatus according to claim 7, comprising a control circuit (1) for sending a control signal, wherein said control circuit applies at a valve opening operation initial stage of said valve body said first voltage to said first coil and said second voltage to said second coil for said first coil and said second coil to generate a magnet flux having same direction, and after that initial stage only to said second coil said second voltage is applied. The apparatus according to claim 7 or claim 8, wherein a circuit means for stabilizing said second voltage is provided. The apparatus according to claim 1 or claim 8, wherein said drive circuit is installed in an interior portion of an engine control unit which controls an operation condition of an internal cmbustion engine. The apparatus of one of the claims 1 to 10, wherein the high voltage is applied to one of said coils used for opening the valve of the injector, and the low voltage is applied to another of said coils used for holding the valve of the injector open.

Inventors: HAMADA YASUNAGA, KADOMUKAI YZO, KUBO HIROMASA, OKAMOTO YOSHIO, TABUCHI KENJI, TAKAHATA TOSHIO, TANABE YOSHIYUKI, YAMAKADO MAKOTO, HAMADA, YASUNAGA, KADOMUKAI, YZO, KUBO, HIROMASA, OKAMOTO, YOSHIO, TABUCHI, KENJI, TAKAHATA, TOSHIO, TANABE, YOSHIYUKI, YAMAKADO, MAKOTO
Applicants: HITACHI CAR ENG CO LTD, HITACHI LTD, HITACHI CAR ENGINEERING CO., LTD., HITACHI, LTD.
Application year: 1999
Main classification: F02M51
IPC codes: F16K31, F02M51, F02D41