EP0246373B1

Movatterモバイル変換

Info

Publication number: EP0246373B1
Application number: EP86303903A
Authority: EP
Inventors: Osamu Matsumura
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-05-22
Filing date: 1986-05-22
Publication date: 1992-03-04
Also published as: ATE73207T1; DE3684143D1; EP0246373A1

Abstract

Fuel is pumped and supplied to an injector (114, 208, 308, 408) which injects the fuel in the form of mist. The quantity of fuel injected from the nozzle is regulated by quantity control means. The control means is comprised of a control valve (152, 210, 310, 410), which is disposed on the injection hole (153, 238, 342, 426) of the injector for controlling the area of the injection hole. When the control valve has sufficient stroke to close the injection hole, the valve serves not only as a control valve, but also as a timing control valve. The movement or stroke of the control valve is accomplished by an actuator (126, 218, 338, 418) which is controlled by electrical control means, for example a microcomputer (122, 205, 305, 405), to enable a precise injection of fuel and an ideal combustion.

Description

The invention generally relates to fuel injection apparatus for an internal combustion engine and particularly, though not exclusively, to fuel injection apparatus for a compression ignition or Diesel engine.
The conventional Diesel engine has a fuel injection pump to inject fuel into each of the cylinders. The fuel injection pump pumps the fuel and supplies it to a fuel injector which has an injecting nozzle. A timer is provided on a cam shaft of the fuel injection pump to control the timing of the fuel injection. The injection pump also requires a mechanical governor, which is connected to a control rack of the pump to regulate the quantity of fuel injected at one time, and thereby to ensure the supply of a suitable quantity of fuel to the engine in response to the condition thereof.
Thus, the conventional fuel injection apparatus includes a fuel injection pump, a mechanical governor and a timer, which are all complex mechanical structures, thus making the fuel injection apparatus very expensive. Furthermore, these complex apparatus require highly skilled maintenance. Moreover, the conventional fuel injection apparatus is not suitable for electric control for example by a microcomputer. Additionally in using the conventional apparatus, it is very difficult to control the pattern of fuel injection, and more specifically it is very difficult to decrease the quantity of fuel at the initial period of the injection. Therefore the engine generates noises and the exhaust gas of the engine contains large quantities of nitrogen oxide.
My Patent Specification EP-A-147026 discloses fuel injection apparatus for an engine comprising a fuel accumulator to hold fuel under pressure, a timing control valve to control flow of fuel from the accumulator to any injection nozzle, a quantity control valve to control the quantity of fuel injected by the injecting nozzle at any one time and electric control means to control the timing control valve and the quantity control valve in accordance with the speed of and load on the engine.
USA-4 669 429 discloses an injector in which upward fullstroke of a nozzle needle is controlled. Such an injector is to be connected to a conventional injection pump and the injector is periodically supplied with pressurised fuel which displaces the needle upwardly against a spring to separate the needle from a valve seat so that the pressurised fuel can be injected through the injection aperture. US-A-4 462 368 discloses an injector with an injection aperture formed laterally on the periphery of the injector, a cylindrical quantity control valve, an actuator and electric control means.
According to the invention there is provided fuel injection apparatus for an engine, wherein fuel under substantially constant pressure is continuously supplied to an injector to inject a mist of fuel, the injection apparatus comprising:
an injection aperture formed substantially laterally on the periphery of the injector to inject fuel;
a quantity control valve formed as a hollow cylinder to control the quantity of the fuel by regulating the effective area of the injection aperture;
an actuator to displace the quantity control valve axially in the injector; and
electric control means to control the actuator in response to speed of and load on the engine;
characterized in that the actuator moves the quantity control valve in an axial stroke sufficient to close the injection aperture, thereby to operate the opening and closing of the injection aperture so that the quantity control valve serves as a timing control valve, and longitudinally extending slits or slots are provided in the wall of the cylindrical quantity control valve to allow deformation of the wall by the pressure of the fuel so as to give close contact with an edge or a valve seat of the injection aperture.
Such fuel injection apparatus can eliminate a periodical fuel injection pump, a mechanical timer and a mechanical governor, need not require highly skilled maintenance thereof, can be completely electrically controlled and can reduce the quantity of fuel during the initial fuel injection period in order to decrease the engine noise and nitrogen oxide in the exhaust gas when the quantity control valve is controlled by the electric control means through the actuator so that the quantity control valve reduces the size of the injection aperture to accomplish a pilot injection at an initial stage of each injection cycle.
The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:-

Figure 1 is a block diagram of fuel injection apparatus according to a first embodiment of the invention;
Figure 2 is a cross section of an injector according to the first embodiment;
Figure 3 is a perspective view of a quantity control valve of this injector;
Figure 4 is a cross section of the quantity control valve of the injector;
Figure 5 is a front view of a control opening formed on the quantity control valve;
Figure 6 is a flow chart of the operation of this injection apparatus;
Figure 7 is a diagram of the injection pattern of the fuel injection apparatus obtained by the first embodiment;
Figure 8 is a cross section of an injector of a modified embodiment;
Figure 9 is a cross section of an injector according to a second embodiment;
Figure 10 is a fuel injection pattern obtained by the injector of Figure 9;
Figure 11 is a cross section of the injector according to a third embodiment;
Figure 12 is a fuel injection pattern according to the injector of Figure 11;
Figure 13 is a block diagram of a modified fuel injection apparatus;
Figure 14 is a block diagram of a modified pump drive system;
Figure 15 is a gearing diagram of the system of Figure 14;
Figure 16 is a cross section of an injector according to a fourth embodiment of the invention;
Figure 17 is a perspective view of the quantity control valve of the injector of Figure 16;
Figure 18 is a cross section of the quantity control valve;
Figure 19 is a diagram of an injection pattern obtained by the injector of Figure 16;
Figure 20 is another diagram of an injection pattern obtained by this embodiment;
Figure 21 is a cross section of an injector according to a fifth embodiment;
Figure 22 is a perspective view of a quantity control valve of the fifth embodiment;
Figure 23 is an enlarged cross section of the fuel control valve;
Figure 24 is a front view of an oblong opening formed in the quantity control valve;
Figure 25 is a front view of an actuator for the quantity control valve according to a sixth embodiment; and
Figure 26 is a front view of a modified actuator.

Referring to the drawings, and firstly to Figure 1, fuel is sucked from afuel tank 201 by a highpressure feed pump 202. Thepump 202 is driven by a directcurrent motor 203 and themotor 203 is controlled by amicrocomputer 205 through adrive circuit 204. The fuel pumped by the highpressure feed pump 202 is pushed into and stored in anaccumulator 206.
Theaccumulator 206 is connected to aninjector 208 by means of afeed pipe 207. Aninjection nozzle 209 is provided at the top end of theinjector 208 and has aquantity control valve 210. Thequantity control valve 210 is controlled by a control signal from themicrocomputer 205. Theinjector 208 is provided on acylinder head 213 which is fixed at the top of thecylinder 212 which receives slidably apiston 211.
The construction of theinjector 208 is shown in Figure 2. Theinjector 208 comprises anozzle holder 216 which holds aninjection nozzle 209 by means of aretainer 217. Asolenoid coil 218 is provided in thenozzle holder 216. Aplunger 219 is connected to thequantity control valve 210 by a connectingrod 220. Aspring seat 221 is provided at the top of theplunger 219 and receives acoil spring 222. Thespring seat 221 has arod 223 projecting upward therefrom and anabutting plate 224 is connected to the top of therod 223.
A steppingmotor 225 is arranged in thenozzle holder 216. Arotor 226 of thestepping motor 225 has a centre throughhole 227 with a female thread. The female thread of thethrough hole 227 is engaged with a male thread formed on the periphery of thesleeve 228. Astopper rod 229 is situated so that therod 229 goes through thesleeve 228. Therod 229 is connected to aplunger 231 situated at the centre of asolenoid coil 230. Theplunger 231 is pushed downward by acoil spring 232 and hence the bottom end of theplunger 231 engages with astep 233 of thenozzle holder 216.
Theinjection nozzle 209 has thequantity control valve 210 which is formed as a cylinder, as shown in Figure 3 and Figure 4, and thevalve 210 hascontrol openings 236 which extend axially.Slots 237 are formed at the both sides of theoblong openings 236. Thevalve 210 is received inside theinjection nozzle 209 so that each control opening 236 coincides with aninjection aperture 238 of theinjection nozzle 209. On the internal peripheral surface of theinjection nozzle 209,valve seats 239 are located at the edge of theinjection aperture 238 and thequantity control valve 210 slides on thevalve seat 239.
In operation, themicrocomputer 205 reads in the number of revolutions and the angular position of the engine through arevolution detecting sensor 240 and also reads in the load of the engine through aload sensor 241. Furthermore, themicrocomputer 205 detects the pressure of the fuel in theaccumulator 206 through thepressure sensor 242. Themicrocomputer 205 controls themotor 203 through thedrive circuit 204 in order to maintain the pressure of fuel at a suitable value. Themicrocomputer 205 controls the solenoid coils 218, 230 and the steppingmotor 225 in accordance with the flow chart shown in Figure 6 and gives the control valve 210 a stepping displacement, thereby to control the quantity of fuel injected at one time and also to open and close theinjection aperture 238 of theinjection nozzle 209.
Thus, themicrocomputer 205 detects the number of revolutions and load of the engine through therevolution detecting sensor 240 and theload sensor 241, and based on these informations themicrocomputer 205 calculates the quantity of fuel injected at one time. This quantity corresponds to the heightb in the injection pattern shown in Figure 7. To obtain the calculated quantity, themicrocomputer 205 drives the steppingmotor 225 which rotates therotor 226 to a predetermined angular position. Then thesleeve 228 moves axially because the male thread of thesleeve 228 engages with thefemale thread 227 of therotor 226. Therefore the gapb between the bottom end of thesleeve 228 and the top surface of theabutting plate 224 is regulated, and the steppingmotor 225 is controlled.
Then themicrocomputer 205 calculates the timing of the injection, and moves thevalve 210 at the proper moment so that the control opening 236 and theinjection aperture 238 coincide. This operation starts fuel injection. That is, themicrocomputer 205 energises thesolenoid coil 218 at the proper time. Then theplunger 219 moves upward against thecoil spring 222 and theabutting plate 224 provided at the top of therod 223 makes contact with thestopper rod 229.
Accordingly, thecontrol valve 210 moves upwards in a stroke corresponding to the gapa between theabutting plate 224 and thestopper rod 229. Thus, theinjection aperture 238 is slightly opened. Hence it is possible to decrease the quantity of fuel at the initial period of the injection, and a pilot injection is accomplished by this operation. When thestopper rod 229 which is connected to theplunger 231 is made of piezo electric material, the length of therod 229 may be expandable to regulate the gapa to control the quantity of fuel at the initial period of injection.
After the predetermined time duration from the start of the injection, themicrocomputer 205 changes the fuel injection from pilot injection to main injection. That is, themicrocomputer 205 energizes thesolenoid coil 230 to displace upwardly theplunger 231 against thecoil spring 232. Then thestopper rod 229 connected to theplunger 231 moves upward and is drawn inside thesleeve 228. Then theplunger 219 moves upwards until theabutting plate 224 comes in contact with the bottom end of thesleeve 228 because theplunger 219 is urged by thesolenoid coil 218. As a result thequantity control valve 210 moves upwards with stepping displacement.
Accordingly, thequantity control valve 210 moves upwards by the strokeb, thereby making theinjection aperture 238 wide open. Since the effective area of theinjection aperture 238 is proportionate to the stroke of thequantity control valve 210, the quantity of fuel injected is controlled by thequantity control valve 210. After a predetermined time has passed, the solenoid coils 218 and 230 are deenergised and thequantity control valve 210 is pushed downward by thecoil spring 222. Thequantity control valve 210 moves downward to a position where the control opening 236 does not coincide with theinjection aperture 238 to close theinjection aperture 238. In this way, the fuel injection is terminated.
The fuel injection apparatus of this embodiment does not require the use of a periodical fuel injection pump, a mechanical governor or a mechanical timer thereof. Furthermore, according to this embodiment it is possible to control the apparatus by themicrocomputer 205, and ensure that a suitable quantity of fuel is injected at the proper time. Additionally, according to this arrangement, a control of an injection pattern as shown in Figure 7 can be accomplished and it is possible to decrease the quantity of fuel at the initial period of the injection. Therefore, it becomes possible to decrease the noise of the engine and to decrease the quantity of nitrogen oxide in the exhaust gas.
A modification of the first embodiment is described with reference to Figure 8. A feature of this modification is that theinjector 208 includes another steppingmotor 245. Arotor sleeve 246 of the steppingmotor 245 has acentre hole 247 and the centre hole is threaded with a female screw which is engaged with a male screw of thestopper rod 229. Additionally, anothersolenoid coil 248 is provided under thesolenoid coil 218.
In operation, the steppingmotor 225 regulates the gapb to control the quantity of the fuel of main injection. Another steppingmotor 245 regulates the gapa to control the quantity of fuel in the pilot injection. At the proper moment thesolenoid coil 218 is energized to displace theplunger 219 to a position where theabutting plate 224 makes contact with thestopper rod 229 by the force of thecoil 218. Theinjection aperture 238 is then slightly opened by the control opening 236 of thevalve 210 to accomplish the pilot injection.
After a predetermined time has passed thesecond solenoid coil 248 is energized, and the upward force is increased. As a result, thesleeve 246 of the steppingmotor 245 which holds thestopper rod 229 moves upward against thecoil spring 232 and theabutting plate 224 makes contact with the bottom end of thesleeve 228 to displace thequantity control valve 210. In this way theinjection aperture 238 is opened wide to accomplish the main injection of fuel. The quantity of fuel is increased at this moment and the stepping pattern shown in Figure 7 is accomplished as in the above-mentioned first embodiment. Furthermore, by this modification it is possible to control the quantity of fuel of the pilot injection by thesecond stepping motor 245.
A second embodiment of this invention is shown in Figure 9 and Figure 10. A feature of this modification is that a linear stepping motor is used for the axial displacement of thequantity control valve 210. Theslider 252 of themotor 251 is connected to thequantity control valve 210 by the connectingrod 220. A pair ofguide members 253 and 254 are provided to ensure a smooth displacement of theslider 252. Themicrocomputer 205 controls thelinear stepping motor 251 to displace thequantity control valve 210 resulting in the fuel injection pattern shown in Figure 10.
According to this arrangement, a singlelinear stepping motor 251 moves thequantity control valve 210 in steps and hence it is possible to simplify the structure of the injector and minimize the number ofmotors 251. Furthermore, it is possible to eliminate thecoil spring 222 when the return motion of the quantity control valve is also accomplished by thelinear stepping motor 251. By this arrangement structure is more simplified.
A third embodiment is described with reference to Figure 11 and Figure 12. In this embodiment, a movingcoil 256 wound on abobbin 255 is used for moving thequantity control valve 210. That is, the movingcoil 256 constitutes the actuator for thecontrol valve 210. The movingcoil 256 wound on thebobbin 255 is connected to thecontrol valve 210 by the connectingrod 220. The movingcoil 256 is located between acentre pole 258 which is mounted at the top of amagnet 257 and anoutside yoke 259. Upward or downward force is applied to the movingcoil 256 in accordance with the principle of the voice coil of a dynamic speaker when an electric current is supplied to the movingcoil 256. Thequantity control valve 210 is moved by this force. Aposition detecting sensor 260 is provided to hold thequantity control valve 210 at a predetermined position. That is, theposition detecting sensor 260 detects the position of thevalve 210 and supplies a signal to themicrocomputer 205 to control the movingcoil 256. Thus, a feedback control is accomplished by theposition detecting sensor 260. Accordingly, it is possible to simplify the structure of the actuator and also it is possible to control the injection pattern voluntarily and precisely as shown in Figure 12 to accomplish an ideal combustion of fuel.
Figure 13 shows a modification of a pressured feed system. A feature of this modification is that arelief valve 262 is provided so that the accumulator can be eliminated. Therelief value 262 is connected to thefuel feed pipe 207. Aspring 263 of thevalve 262 is controlled by themicrocomputer 205 through anactuator 264 to control the relief pressure of therelief valve 262. Themicrocomputer 205 regulates thespring 263 through theactuator 264 in response to thepressure detecting sensor 242 precisely to control the pressure on which therelief valve 262 operates. Accordingly, it is possible to control the output pressure of thefuel feed pump 202 and to accomplish fuel injection without an accumulator.
Figure 14 and Figure 15 show a modification of a feed pump drive system. A feature of this modification is that adifferential gear apparatus 348 is used to drive the highpressure feed pump 302, instead of a direct current motor. Thedifferential gear apparatus 348 is combined with anengine 347 and the rotary output speed of the apparatus is controlled by a directcurrent motor 303. Amicrocomputer 305 reads in the revolution number and the engine load through therevolution detecting sensor 345 and theload sensor 346. Themotor 303 is controlled by themicrocomputer 305 through adrive circuit 304.
More specifically, agear 349 takes out the torque of theengine 347 as shown in Figure 15 and thegear 349 is connected to asun gear 350 which engages aplanet gear 351. Theplanet gear 351 is supported by anarm 352. Thearm 352 is fixed on the input shaft of thefeed pump 302. Theplanet gear 351 supported by thearm 352 is engaged with aninternal gear 353. The outside gear of theinternal gear 353 is driven by apinion 354 which is fixed on the output shaft of themotor 303.
Accordingly, the torque of theengine 347 transmitted to thegear 349 is transformed to rotation of a pair of planet gears 351 by means of thesun gar 350. Therefore, the planet gears 351 makes theinternal gear 353 revolve. The revolution is transmitted to thefeed pump 302 by means of thearm 352. Themotor 303 drives theinternal gear 353 through thepinion 354. The revolutional speed of thearm 352 is increased when themotor 303 drives theinternal gear 353 in the plus direction, and decreased when rotated in the minus direction. Furthermore, it is possible to stop thepump 302 by themotor 303. Therefore, it is possible to obtain torque from theengine 347 and control the number of revolutions of thefeed pump 302 by themotor 303. Thefeed pump 302 may be a plunger pump, vane pump, or another kind of pump, and the feed pump may be made of a multistage pump to obtain the required output pressure.
A fourth embodiment of this invention is described with reference to Figure 16 to Figure 20. A feature of this embodiment is that thecontrol valve 310 of theinjector 308 constitutes not only the quantity control valve but also the timing valve and that a column ofpiezoelectric element 338 is received in thenozzle holder 324 of theinjector 308, and the bottom end of thecolumn 338 is guided in the axial direction by a pair ofprojections 359 provided inside thenozzle holder 324. Acylindrical valve member 339 is connected to thepiezoelectric element 338 by the connectingmember 360 which has afeed hole 361 to feed fuel into thevalve member 339. The piezo-electric element 338 haselectrodes 362 which are connected to adrive circuit 363. Thevalve member 339 has thecontrol openings 341 as shown in Figure 17 and Figure 18, and thecontrol openings 341 control the effective area of theinjection aperture 342 of thenozzle 326. Furthermore,longitudinal slots 364 are formed in thevalve member 339. Theslots 364 serve to deform thevalve member 339 to contact thevalve seat 365 by the pressure of the fuel.
In operation themicrocomputer 305 supplies a control signal to thedrive circuit 363 to generate a pattern of voltage for thepiezoelectric element 338 as shown in Figure 19 or Figure 20. As the voltage applied to the piezo-electric element 338 is substantially proportional to the stroke of thevalve member 339, theinjection aperture 342 is opened and the effective area of theinjection aperture 342 is controlled by the control opening 341 of thevalve member 339. Specifically, it is possible to obtain an injection pattern of ideal or suitable combustion when the quantity of fuel at the initial period of the injection is decreased as shown in Figure 20.
Furthermore, in this arrangement, thevalve member 339 moves to a position where the control opening 341 does not coincide with theinjection aperture 342 when the voltage is relieved. This operation makes it possible to omit the timing valve, because thevalve member 339 performs not only the quantity control valve function but also the timing valve function. Also, it is not necessary to use a timing control valve formed as a solenoid valve. Additionally thevalve member 339 is pressed on thevalve seat 365 of thenozzle 326 by the pressure of the fuel, and by this arrangement it is possible to close the injection aperture securely. The closing operation is assisted by theslots 364 which serve to deform thevalve member 339.
A fifth embodiment of the invention is described with reference to Figure 21 to Figure 24. Figure 21 shows aninjector 408 which includes anozzle holder 416 and afuel feed pipe 407. Anozzle 409 is connected to the bottom of thenozzle holder 416 by aretainer 417. A pair of bimorph plates are arranged parallel and longitudinally in thenozzle holder 416. Arod 419 is secured with an adjustingscrew 420 and therod 419 has abracket 421 which supports the top ends of the pair ofbimorph plates 418 rotatably. The lower ends of the pair ofbimorph plates 418 are connected rotatably to thequantity control valve 410 by a connectingrod 423.
Thequantity control valve 410 is cylindrical as shown in Figure 22 and Figure 23 and hascontrol openings 424 or oblong openings andlongitudinal slots 425 at both sides of thecontrol openings 424. Thequantity control valve 410 is arranged inside thenozzle 409 so that thecontrol openings 424 coincide with aninjection aperture 426 of thenozzle 409. Thevalve member 410 slides axially on avalve seat 427 formed on the internal peripheral surface of thenozzle 409 with theinjection aperture 426.
In operation themicrocomputer 405 reads in the rotary speed and the angular position of the engine through a revolution detecting sensor, and the engine load through a load sensor. Themicrocomputer 405 also reads in the pressure of the fuel held in the accumulator (not shown) by a pressure sensor. Themicrocomputer 405 then controls the pump, through the motor to maintain the pressure of the fuel at a suitable value. Themicrocomputer 405 also controls the pair ofbimorph plates 418 to displace thequantity control valve 410 thereby to control the quantity of fuel injected at one time. Thecontrol valve 410 opens and closes theinjection hole 426 of thenozzle 409.
Thus, themicrocomputer 405 reads in the speed and the load of the engine, and then calculates the timing of the injection, the quantity of fuel, and the injection pattern based on the abovementioned information. Resulting from these calculations, themicrocomputer 405 controls thedrive circuit 433 which controls the voltage applied to thebimorph plates 418.
Thebimorph plates 418 deform as shown by the chain line in Figure 21 when electric voltage is applied. The pair ofbimorph plates 418 deform in such a manner that intermediate portions of theseplates 418 are separated from each other. As a result of this deformation thelower bracket 422 moves upward. This movement is transmitted to thequantity control valve 410 by therod 423. Accordingly, as shown in Figure 24 the control opening 424 controls the effective area of theinjection aperture 426, thus performing the quantity control operation.
In the apparatus thequantity control valve 410 has sufficient stroke to close theinjection aperture 426. Therefore, thequantity control valve 410 not only controls the quantity of fuel but also controls the opening and closing of theinjection aperture 426. Furthermore, the injection pattern is controlled when the voltage applied to thebimorph plates 418 is controlled. More specifically, when the quantity of fuel at the initial stage of the fuel injection is decreased, it is possible to decrease the engine noise and amount of nitrogen oxide in the exhaust gas.
As mentioned above, according to this embodiment, the control of fuel quantity, the injection timing, and the injection pattern are all accomplished by thequantity control valve 410 associated with the pair ofbimorph plates 418. Furthermore, thecontrol valve 410 is pressed against thevalve seat 427 by the pressure of the fuel through thelongitudinal slots 425 to accomplish perfect sealing operation when thequantity control valve 410 displaces to the position where theinjection aperture 426 is closed.
A sixth embodiment of this invention is described with reference to Figure 25 which shows asingle bimorph plate 418 for displacing thequantity control valve 410. Thebimorph plate 418 is disposed horizontally. One end of theplate 418 has a bracket 421' and the other end has a bracket 422' which is connected to anoblong opening 437 of a supportingbracket 436 by means of apin 438 to permit the deformation of thebimorph plate 418 to the shape of arch. By this arrangement it is possible to displace thequantity control valve 410 by a relatively slight deformation of the intermediate portion of thebimorph plate 418. In this way the mechanism for opening and closing thequantity control valve 410 is simplified and is compact.
A modification is shown in Figure 26, in which asingle bimorph plate 418 is used and one end of theplate 418 is fixed. The free end of theplate 418 is connected to thequantity control valve 410 by a connectingrod 423. According to this arrangement, the mechanism for supporting thebimorph plate 418 is more simplified and hence the structure of the injector can be simple.
An actuator of monomorph plate may be used instead of the bimorph plate in the last embodiment, and further magnetostrictive elements may be used for the actuator to control the displacement of the quantity control valve instead of the piezo-electric element. Furthermore, various materials may be used for the nozzle or the injector, and the nozzle may be made of ceramic materials to protect the quantity control valve or the piezo-electric element from heat. Furthermore, the invention is applicable not only to fuel injection apparatus of a Diesel engine but also to that of a gasoline engine when the pressure of the fuel is reduced.

Claims

Fuel injection apparatus for an engine, wherein fuel under substantially constant pressure is continuously supplied to an injector (208, 308, 408) to inject a mist of fuel, the injection apparatus comprising:
an injection aperture (238, 342, 426) formed substantially laterally on the periphery of the injector to inject fuel;
a quantity control valve (210, 310, 410) formed as a hollow cylinder to control the quantity of the fuel by regulating the effective area of the injection aperture;
an actuator (218, 251, 256, 338, 418) to displace the quantity control valve axially in the injector; and
electric control means (205, 305, 405) to control the actuator in response to speed of and load on the engine;
characterized in that the actuator moves the quantity control valve in an axial stroke sufficient to close the injection aperture, thereby to operate the opening and closing of the injection aperture so that the quantity control valve serves as a timing control valve, and longitudinally extending slits or slots (237, 364, 425) are provided in the wall of the cylindrical quantity control valve to allow deformation of the wall by the pressure of the fuel so as to give close contact with an edge or a valve seat (239, 365, 427) of the injection aperture.
Fuel injection apparatus according to claim 1, including a feed pump (202, 302) to pressurise the fuel, and an accumulator (206) to store the fuel under pressure, the fuel pressurised by the feed pump being pushed into the accumulator.
Fuel injection apparatus according to claim 2, wherein the pressure of the fuel in the accumulator is detected by a pressure detecting sensor (242) and the feed pump is controlled in response to the detecting signal of the pressure detection sensor to maintain the pressure of the fuel in the accumulator substantially constant.
Fuel injection apparatus according to claim 1, including a feed pump (202, 302) to pressurise the fuel, and a relief valve (262) connected to the feed pump, the relief pressure of the relief valve being controlled to maintain the output pressure of the feed pump substantially constant.
Fuel injection apparatus according to claim 1, wherein the quantity control valve has a constant opening (236, 341, 424) to control the effective area of the injection aperture in response to the displacement thereof.
Fuel injection apparatus according to claim 1, wherein the actuator operates as a stopper (228) of the quantity control valve, and the axial stroke of the quantity control valve is controlled by the stopper.
Fuel injection apparatus according to claim 1, wherein the actuator is a magnetic coil (218).
Fuel injection apparatus according to claim 1, wherein the actuator is a stepping motor (225, 251).
Fuel injection apparatus according to claim 1, wherein the actuator is a linear motor (251).
Fuel injection apparatus according to claim 1, wherein the actuator is a moving coil (256) and the position of the moving coil is detected by a position sensor (260), the moving coil driving the quantity control valve according to the principle of a dynamic speaker.
Fuel injection apparatus according to claim 1, wherein the actuator is a piezo-electric element (338, 418).
Fuel injection apparatus according to claim 11, wherein the piezo-electric element is made of the bimorph plate (418).
A fuel injection apparatus according to claim 12, wherein the actuator is made of a pair of bimorph plates (418) which are longitudinally and parallely disposed and both ends of which are rotatably connected.
Fuel injection apparatus according to claim 12, wherein one end of the bimorph plate (418) is fixed and the other free end of the bimorph plate is connected to the quantity control valve.
Fuel injection apparatus according to claim 7, including a stopper (229) to restrict the stroke of the quantity control valve at the initial period of the fuel injection to accomplish a pilot injection, the pilot injection being released by another magnetic coil (230, 248) to step the quantity control valve and change the fuel injection from the pilot injection to main injection.
Fuel injection apparatus according to claim 15, wherein the quantity of fuel of the pilot injection is constant.
Fuel injection apparatus according to claim 15, including another actuator (245) to control the quantity of fuel of the pilot injection.
Fuel injection apparatus according to claim 11, wherein electric voltage applied on the piezo-electric element (338, 418) is changed during the time duration of the injection thereby to displace the quantity control valve during the injection operation.