Abstract:
This invention relates to an electrically operated fuel injection apparatus comprising a fuel inletting device( 110 ), a fuel pumping device ( 112 ) and a fuel injecting device ( 113 ). Fuel from the said fuel inletting device ( 110 ) is pumped by the said fuel pumping device ( 112 ) and then is injected out by the said fuel injecting device, wherein the said fuel pumping device ( 112 ) includes an operating coil ( 13 ), a returning coil ( 12 ) and a driven device ( 114 ) driven by the magnetic fields of these two coils; the magnetic loop induced by the said operating coil ( 13 ) excites the said driven device  9114 ) so as to inject the fuel by the said fuel injecting device ( 113 ), and the magnetic loop induced by the said returning coil ( 12 ) excites the said driven device to return back to its original position.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to electrically operated fuel injection apparatus, especially fuel injection apparatus driven by electromagnetic coils.  
         BACKGROUND ART  
         [0002]    Two types of electrically operated fuel injection apparatus have been known. In one of the two types, the electronic system is just for controlling the opening and closing of the fuel injector, and the injection pressure is totally supplied by another system, which could be a mechanical system or an electrical fuel pump. The other type is a system in which a plunger pump is driven periodically by electromagnetic force, controlled by an electronic system, to generate an injection pressure so as to realize pulse injection. As examples of the first type, one may cite the electronic fuel injection (EFI) system adopted in four-stroke gasoline engine and the electrically controlled high-pressure common trail fuel injection system used in high-speed diesel engine (cf. Chapter VI,  Internal Combustion Engine,  compiled by Zhou Baolong, published by the Press of Engineering Industry in 1998, Beijing). As an example of the second type, one may cite the fuel injection system, developed by the Ficht Inc. of Germany, which is operating with the principle of solid energy storage (cf. U.S. Pat. No. 5,469,828 published in 1995 and CN patent application Ser. No.  9 , 619 , 481 , 5 . 9  published in 1998). The main drawbacks of the first type include its complexity and high cost. Consequently, it is difficult to apply on engines where the cost is limited, such as for motorcycle. The second type is simple in construction and low in cost, however, conventionally, single electromagnetic coil is used to drive the follower in forward direction, and the return of the follower relies on spring force. Consequently, a part of the forward electromagnetic driving force has to overcome the resistance of the spring, and the motion characteristics of the follower depends greatly on the stiffness and pretightening force of the spring. Therefore, the maximum operating frequency of the fuel injection system is limited and injection pressure is relatively low. Thus, it is difficult to use such injection system on high-speed engine such as the engine of motorcycles etc.  
         SUMMARY OF THE INVENTION  
         [0003]    The object of the invention is to provide electrically operated fuel injection apparatus with higher operating frequency and sufficiently high injection pressure to meet the requirements of high-speed engine.  
           [0004]    Above object is achieved by an electrically operated fuel injection apparatus comprising: a fuel intake means, a fuel pumping means and a fuel injecting means, wherein the fuel introduced via the fuel intake means is pressed by the fuel pumping means and is injected out from the fuel injecting means. The fuel pumping means includes a working coil, a return coil and a follower driven by the two coils. The follower is driven by the magnetic loop formed by the working coil to press the fuel to be injected out from the fuel injecting means, and is returned backward by the magnetic loop formed by the return coil. The electromagnetic fields of the coils are generated from so-called PWM voltage-current wave, that is, pulse width modulated voltage-current wave, input via respective wire connections.  
           [0005]    Preferably, the working coil and the return coil are arranged coaxially, and the directions of currents are controlled so that the magnetic fields passing through the follower are kept steadily consistent with each other or alternating with each other.  
           [0006]    Preferably, the follower comprises an armature and a plunger, which may be integral with each other, or may be two separated components, which may be made of different materials. The plunger is substantially cylindrical in shape with a central fuel channel running through it, and with a shoulder on the leading end for limiting the initial position of the plunger. Between the separated plunger and armature there is a valve for closing the fuel channel and controlled by the armature. The body of the valve may be a ball and mounted on the leading end of the armature, for example, embedded in the armature. A spacer may be disposed between the ball valve and the armature, and a valve seat having, for example, conical surface, may be disposed on the rear end of the plunger. The shape of the armature is substantially cylindrical with axial through-hole or through groove. A boss is provided on the armature&#39;s front-end face in which the ball valve is embedded. In the central portion of the armature is a cutout of material, that is, a circumferential groove. The movement of the armature is limited in an armature chamber. The front-end face of the armature is constantly located near or within the magnetic gap of the forward driving magnetic loop. The rear end face of the armature is constantly located near or within the magnetic gap of the return driving magnetic loop. The elements constituting the wall of the armature chamber including electromagnetic elements made of, such as, pure iron, low carbon steel and etc., sliding fitted with the armature, and non-magnetizing or poor-electromagnetic elements made of, such as, copper, stainless steel and etc., sliding fitted or clearance fitted with the armature.  
           [0007]    The inventive fuel injection equipment may be further modified by an elastic element for energy storage, which is disposed in the rear-most portion of the armature chamber, and whose deformation is very small. The elastic element may be, for example, a curved sheet metal, or a spiral wire spring.  
           [0008]    The fuel intake means of the inventive fuel injection equipment include a circumferential groove provided on the cavity body, a one-way valve, a fuel inlet disposed on the housing, and a fuel returning mechanism. The outlet of the one-way valve is communicated with a pressure chamber and the inlet thereof is communicated with the circumferential groove. Furthermore, a channel communicating the armature chamber with the circumferential groove may be provided on the cavity body for facilitating massive fuel returning. Between the armature chamber and the fuel returning outlet, a rear end element with a through-hole may be disposed, which is kept communicating with the armature chamber via the through hole or grooves on the armature. The rear end element may also be made of hard magnetic or permanent magnetic material. For replacing the low-pressure fuel supply means, in the fuel returning circuit or the rear end element, a one-way valve for fuel returning may also be provided for forcibly generating a sufficiently large amount of returned fuel by making use of the return action of the follower.  
           [0009]    The fuel injecting means of the inventive fuel injection equipment comprises a fuel delivery valve, a high-pressure fuel passage and an atomizer nozzle. The fuel delivery valve comprises a valve body, a valve seat and spring. The valve body may be spherical and the valve seat may be an axisymmetric curved surface; or, the valve body may be a planar sheet and the valve seat may be an O-ring. The high-pressure fuel passage may be a hole, for mounting the atomizer nozzle, in the cavity body, or may be an inner bore of a high-pressure fuel pipe communicating the fuel delivery valve with the atomizer nozzle. The atomizer nozzle may comprise a nozzle body, a needle stem and spring, wherein the cone portion in the front end portion of the needle stem constitutes a valve body, the conical surface of the nozzle body constitute a valve seat, and the nozzle body is provided with fuel inlet(s) and passage(s). The valve cap and the valve stem are integrated into one, and the axial gap between nozzle body and the valve cap constitutes the maximum lift of the needle valve.  
           [0010]    According to above technical solution, the forward and return movements of the follower are controlled respectively by electropulse signals input from outside for electromagnetic operation. During a period within the forward movement or the return movement, the follower encounters almost zero resistance. Consequently, the acceleration and the velocity of the follower during the forward injection period and/or return period may be very high. In very short time, for example 2 milliseconds, the follower may obtain adequate kinetic energy for impacting the fuel in the pressure chamber. Thus, the fuel injection pressure may be improved and very high operating frequency, of, for example, 150 Hz, may be obtained.  
           [0011]    The following technical features are also in favor of the reliability of the equipment when operating in high frequency. The coaxial arrangement of the working coil and the return coil results in a compact structure of the equipment. The through-hole or through-groove provided in axial direction on the armature reduces flow resistance, derived from the fuel flowing relatively to the armature, to such an extent that the resistance could be ignored. The sliding fit or clearance fit between the armature and the armature chamber ensures the movement of the armature is not influenced by solid friction. The circumferential groove in the central portion of the armature is to adjust the moving mass of the follower. The elastic element for energy storage may prevent the armature from being adsorbed on the rear end face of the armature chamber.  
           [0012]    Depending on the structure of fuel injection equipment and operating environment in its typical application, the bubbles in the fuel is an important factor affecting the operating reliability and the calibrated injection amount per cycle. The space occupied by fuel comprises the pressure chamber, the armature chamber, the high-pressure passage and etc. The bubbles generated in the pressure chamber and the high-pressure passage affect the operation of the system the most seriously. The high-pressure passage refers to the space for fuel flowing between the pressure chamber and the injection nozzle. The armature chamber is the space necessary for the reciprocal movement of the armature. The bubbles mainly derive from: residual air; vaporization of part of fuel in the high pressure passage and/or pressure chamber by the heat transmitted from outside such as the combustion chamber; vaporization of part of fuel in the armature chamber by friction heat and/or electrical resistance heat generated by the coil; and fuel vaporization or libertion of dissolved gas from the fuel, caused by local negative pressure generated from fuel movement in the armature chamber and/or pressure chamber. In the present invention, because of various solutions for reducing bubbles, the reliability and stability are ensured even when the apparatus operates in high frequency  
           [0013]    By dividing the follower into two portions, that is, the armature and the plunger, and by providing a channel in the plunger and valve(s) for closing the channel, the passages for returning fuel and discharging bubbles become shorter, which facilitate the discharge of bubbles in the pressure chamber. The fuel returning system is designed with sufficiently high flux, so that the injecting means could be cooled lest bubbles should be generated due to heat, and bubbles generated could be discharged out.  
           [0014]    In the inventive fuel injection equipment, a fuel delivery valve is disposed in the fuel injecting means, so that a predetermined initial pressure could be maintained in the high pressure passage so as to prevent bubbles in it, thus the fuel injection quantity per pulse is stabilized. The atomizer nozzle may be mounted on the body of the fuel injection equipment, or may be communicated with the body via a high-pressure fuel pipe so that the injection nozzle could be mounted into the engine easier. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a longitudinal section view of electrically operated fuel injection apparatus according to an embodiment of the present invention;  
         [0016]    [0016]FIG. 2 is a longitudinal section view of electrically operated fuel injection apparatus according to a modified embodiment of the present invention;  
         [0017]    [0017]FIG. 3 is a cross section view of an armature according to the present invention;  
         [0018]    [0018]FIG. 4 is a schematic view of a two-stroke engine adopting an electrically operated fuel injection apparatus of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Now the present invention will be described in details with reference to the accompanying drawings.  
         [0020]    In a first embodiment, at an initial time of each cycle, the follower  114  is situated in a rear-most position as shown in FIG. 1. The fuel is introduced from the fuel intake means  110  into the pressure chamber  43  of the actuating means  112 . When pulse current begins flow in the working coil  113  of the actuating means, the electromagnetic force generated by the magnetic field generated from the current will accelerate, in the forward direction, the follower  114 , which, when touching the ball valve body  115  by its leading end, will impact the fuel inside the compression pressure chamber  43  making its pressure up. When the fuel pressure becomes sufficiently high, the self-opening fuel atomizer nozzle  36  of the fuel injection means will open to inject the fuel. The injection ends when a reverse electromagnetic driving force generated from the pulse current in the return coil  12  acts on the follower  114  and makes it return, and then new fuel is introduced into the pressure chamber  43  and a fuel injection cycle is completed.  
         [0021]    The inventive equipment may generate sufficiently high injection pressure within limited time with limited electromagnetic force, because before compressing the fuel, the follower  114  has a free accelerating travel without any load, and thus has accumulated adequate kinetic energy for impacting the fuel in the pressure chamber  43 . That is, at the initial position, the leading end of the follower  114  does not touch the valve body  115 , but has a gap S there between. When moving forward, the follower  114  does not compress the fuel in the pressure chamber  43  since the spaces in the front of and behind the follower are communicated with each other through the through-hole  116 . Consequently, additionally due to the existence of the longitudinal through grooves  57 , the movement of the follower almost suffers no resistance. After a predetermined course S, the valve body  15  closes the passage  116 , and thus the fuel in the pressure chamber  43  begins to be compressed. Due to adequate kinetic energy accumulated in the follower  114  during the no load course, the fuel pressure in the pressure chamber  43  will rise to an extent enough to inject the fuel out of the fuel injection means  112  and atomize the fuel. In fact, after the course S, if the forward electromagnetic force continues to act on the follower  114 , then the power for pressurizing the fuel in the pressure chamber  43  further includes the electromagnetic force besides the impact force of the follower  114 . Apparently, the injection pressure and the injection quantity depend partially on the amplitude of the electromagnetic force and the length of the acting period of the electromagnetic force. When the pulse current in the working coil  13  ends or is about to end, the pulse current in the return coil begins to rise, and thus a reverse force begins to acts on the follower  114 , which eventually begins to return to its initial position. During the return course, fresh fuel is introduce into the pressure chamber  43  via the means  110  and all come back to the initial state.  
         [0022]    In a second embodiment, the components of the invention are further modified. The working coil  13  and the return coil  12  are respectively wound round non-metal frames  18 ,  14 , and insulating materials  17 ,  15  are filled in the peripheral of the coils. The magnetic loop around the working coil  13  comprises electromagnetic elements  7 ,  6 ,  8 ,  10 ,  9 , working magnetic gap  11  and the front half of the armature  56 . The magnetic loop around the return coil  12  comprises electromagnetic elements  1 ,  2 ,  3 ,  6 ,  4 , return magnetic gap  5  and the rear half of the armature  56 . The working magnetic gap  11  or return magnetic gap  11  may comprises clearance or non-electromagnetic elements made of, such as, plastics, copper or stainless steel and so on. The section of either of the coils  12 ,  13  is substantially rectangular or trapezoid. Said two electromagnetic loops are received in a housing  19 , which is provided with fuel inlet  20  and fuel return port  59 . The housing  19  and the front-end element  32  are coupled with each other by screw connection  84 , and thus all the components are restrained to respective positions.  
         [0023]    In the second embodiment, the follower  114  is formed in two parts, that is, an armature  56  and an plunger  46 .The general geometric form of the armature  56  is a revolution body, on which are machined longitudinal holes and/or grooves  57 , circumferential groove(s)  63  and other holes  62  and cavities and so on. Wherein, the longitudinal grooves  57  are used as fuel passages and contribute to reduce the mass of the armature, which mass will affect the high speed characteristics and impact force. The fuel flowing through the grooves  57  washes and thus cools the armature  56  and nearby components. The grooves  57  also contribute to reduce the resistance to the motion of the armature  56 . The circumferential groove  63  is provided in the central portion between the two end faces of the said armature in a form of material cutout, which is to adjust the mass of the armature, without affecting the linear movement thereof. As part of the fuel returning passage, the holes or grooves  62  ensure the returning fuel flow when the armature  56  is in the rear end position. A cylindrical cavity  53  is provided for housing a spacer  54  and a portion of the ball valve  52 . One end of the spacer  54  is a planar surface  55  for contacting the armature; the other end is a conical surface, upon which the valve body  52  resides. In addition, a boss  83  is provided on the front end of the armature  56 . The spacer  54  and the ball valve  52  are restrained in the cavity  53  through pressed deformation of the boss  83 .  
         [0024]    The armature  56  reciprocates in a space  50 , which is substantially cylindrical. The side face of the cylindrical space  50  is formed by part of the cases forming said two magnetic loops. One end face of the cylindrical space is formed by the end element  60 , and the boundary of the other end is comprised of the end faces respectively of the plunger  46 , the plunger sleeve  82  and the cavity body  33 . For preventing the armature from being adhered on the end face  58  when the armature moved to touch the end face, and thus preventing the high-speed characteristics from being deteriorated, an elastic element  109  for energy storage with very small axial deformation (for example, 0.05-0.3 mm) may be arranged between the end element  60  and the armature  56 . The Glastic element may be curved sheet steel, or may be a spiral wire spring. One end of the reciprocating motion of the armature  56  is defined by said elastic element  109  for energy storage. To keep the armature in the initial position when the coils are not powered, the end element  60  may be made of hard magnetic material, or a spring  48  of minimal stiffness may be disposed in the armature chamber. The length of the armature is designed so that in the initial position, the end face  81  of the armature is positioned just within the length of the working magnetic gap  11 . The other end of the motion of the armature  56  is defined depending on the electrical pulses of the working coil  13  and the return coil  12  and etc.  
         [0025]    The plunger  46  and the armature  56  are arranged coaxially and the plunger  46  passes through the inner bore of the plunger sleeve  82 . One end of the plunger  46  extends into the armature chamber  50  and the other end extends into the pressure chamber  43 . On one end of the plunger  46 , that is the end in the armature chamber  50 , is provided a conical valve seat  47 . On the other end of the plunger  46 , that is the end in the pressure chamber  43 , is provided a disc shoulder  68  and a length of spring guide  67  in cylindrical form. The diameter of the disc shoulder  68  is greater than the diameter of the inner bore of the plunger sleeve  82 , so that when the disc shoulder  68  contacts the end face of the plunger sleeve  82 , the further movement of the plunger  46  toward the armature chamber  46  is restrained. Along the central axes of the plunger  46 , one or more passages  45  communicating the pressure chamber  43  and the armature chamber  50  are provided for discharging the bubbles in the pressure chamber and for returning fuel. The passages  45  will be closed if the valve body  52  contacts with the valve seat  47 . The fit between the plunger  46  and the plunger sleeve  82  meets the requirement as in common plunger fuel pump. The plunger sleeve  82  may a portion of the cavity body  33 , or may be formed as a separate component to be engaged into the cavity body  33  in a manner of stationary fit.  
         [0026]    The pressure chamber  43  is provided in the cavity body  33 . One end boundary of the pressure chamber  43  is the end face  44  of the plunger sleeve and the other end boundary is the end face  69  of the fuel delivery valve  30 . On the side wall of the pressure chamber  43  is disposed a fuel inlet hole  28 , the other end of which is communicated with a one-way valve  27 . In the pressure chamber  43 , a spring  42  is used to return the plunger  46 . One end of the spring  42  is pressed on the shoulder  68  of the plunger, the other on the end face  69  of the fuel delivery valve.  
         [0027]    The fuel delivery valve  30  is arranged between the finishing end of the pressure chamber  43  and the beginning end of the high-pressure passage  41 . The fuel delivery valve  30  comprises a valve body  29 , a spring  31 , a valve seat  85  and a back cover  71 , wherein the valve body  29  is spherical and the valve seat  72  is an axisymmetric curved surface; or the valve body  29  is a planar sheet while the valve seat  72  is an O-ring. One end of the spring  31  presses the valve body  29  against the tight surface  72  of the valve seat, and the other end presses against the back cover  71 . The stiffness of the spring  31  will influence the amplitude of the residual pressure in the high-pressure passage  41 . A predetermined residual pressure is maintained in the high-pressure passage  41  for preventing bubbles from being generated due to the vaporization of the fuel therein.  
         [0028]    The high-pressure passage  41  refers to the space, which the fuel can reach, from the outlet end face  70  of the fuel delivery valve  31  to the sealing area  35  of the injection nozzle. The high-pressure passage  41  is substantially a cylindrical space, the length of which depends on the distance between the fuel delivery valve  30  and the injection nozzle  36 . If said distance is very large, then a high-pressure fuel pipe, as the high-pressure passage  41 , may be provided between the fuel delivery valve  30  and the injection nozzle  36 .  
         [0029]    The injection nozzle  36  is a conical valve pretightened by spring and located in the downstream of the high-pressure passage  41 . The injection nozzle  36  comprises a nozzle body  86 , a conical valve stem  40 , a valve cap  73 , a pretightening spring and etc. The cone  74  of one end of the conical valve stem  40  constitutes a valve body; the conical surface of the discharge port of the fuel passage  37  in the injection nozzle  36  constitutes a valve seat. By the pre-tightened force of the spring  39 , the valve body is pressed against the valve seat  75  so that the injection nozzle is closed. The fuel enters into the passage  37  via an inlet  38 . When the force pushing the valve stem  40 , which is generated by the fuel pressure, becomes greater than the pre-tightened force of the spring, the injection nozzle opens and the fuel is injected out.  
         [0030]    The fuel inlet  20  is communicated directly with a circumferential groove  22  arranged around the pressure chamber  22 . A portion of the fuel in the circumferential groove  22  flows via a passage  49  into the armature chamber  50  and the rest of the fuel flows via a one-way valve  23  into the pressure chamber  43 . On the cavity body are arranged two O-rings  78  and  23 , which substantially excludes the possibility of leakage of the fuel via other paths. The one-way valve  23  comprises a valve body  25 , a valve seat  76  and a spring  26 .  
         [0031]    The fuel return port  59  arranged in the housing  19  is substantially along the axes of the armature  56  and located on the end of the armature opposite to the plunger  46 . The position of the fuel return port is defined like this mainly for forming a longitudinal pressure gradient in the armature chamber  50 . It is well known that in a liquid having a pressure gradient, the bubbles will move in a negative direction of the gradient. Thus, the bubbles in the armature chamber  50 , especially near the valve seat  47 , will be discharged out along the liquid flowing direction. The bubbles near the valve seat  47  mainly come from the pressure chamber  43 . When the armature  56  is in its initial position, due to the separating of the valve body  52  from the valve seat  47 , the pressure chamber  43  will be communicated with the armature chamber  50 , and thus the bubbles in the pressure chamber  43  will arrive at the valve seat  47  via the passage  45 .  
         [0032]    The inventive fuel injection equipment is applicable to internal combustion engine, such as four-stroke spark ignition engine with intake port fuel injection system or with in-cylinder fuel direct injection system, and especially applicable to two-stroke spark ignition engine with in-cylinder fuel direct injection system. FIG. 4 shows a two-stroke spark ignition engine with in-cylinder fuel direct injection system incorporating the inventive apparatus.  
         [0033]    The inventive fuel injection equipment  88  is mounted on the cylinder head  96 . It functions to pressurize the fuel from a low pressure fuel pump  93  and inject the pressurized fuel into the combustion chamber  99  of the cylinder. The injection is controlled by an electronic controlling unit  104  so as to occur after the exhaust port has been closed and before the spark plug sparks. The fuel injection quantity and the injection timing is determined mainly according to signals coming from a throttle position sensor  101  and/or a crankcase pressure sensor  109 , an inlet air temperature sensor  102  and a sensor  103  for sensing the crank angle and revolution speed of the crankshaft. A portion of the fuel supplied from the low pressure fuel pump  93  is injected by the fuel injection means  88  into the cylinder and combusts therein, while most of the fuel cycles in a loop comprised of a low pressure fuel pipe  95 , a cooler  92 , a fuel pump  93 , and a fuel filter  94  and so on. The principle function of the loop is to take away the heat in the fuel injection means  88 . A fuel quantity corresponding to that consumed by the combustion in the engine is replenished from a fuel tank  91  into the cooler  92 . When the engine operates, above system substantially excludes the possibility of part of the fuel being discharged directly without combustion into the atmosphere via the exhaust port  108 . This is because, on one hand, the scavenging is completed totally by fresh air instead of combustible gas mixture; on the other hand, stratified mixture combustion and/or multi-cycles of scavenging are adopted so that misfire at low-load operating condition is prevented at a maximum extent. Compared to two-stroke engine with a carburetor fuel system, the inventive system will make the engine&#39;s fuel consumption rate remarkably lowered, and compared to four-stroke engine, it will have a higher performance per liter and a higher average effective pressure.  
         [0034]    A two-stroke engine with in-cylinder fuel injection system requires the operating frequency of the fuel injection apparatus as two times high as that of a four-stroke engine, because in a two-stroke engine, there is one combustion per 360° of the crankshaft revolution; while in a four-stroke engine, there is one combustion per 720° of the crankshaft revolution. For example, in a two-stroke engine has a maximal revolution of 9000 rpm, the operating frequency of the injection means shall be higher than 150 Hz. The inventive electrically operated fuel injection apparatus may overcome the drawbacks of the known fuel injection equipment having only single magnetic loop, which equipment is hard to operate reliably in high speed. The inventive equipment is especially applicable to the four-stroke or two-stroke engines adopted in motorcycle and having usually very high speed of revolution.  
         [0035]    The above-described embodiments are merely examples for explaining the invention, not for defining the invention. Any modification or variation made with the concept of the invention and being obvious to a person skilled in the art will fall into the scope of protection of the appended claims.