JP6281296B2 - Fuel injection valve - Google Patents

Description

  The present invention relates to a fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine.

  Conventionally, as this type of fuel injection valve, for example, there is one described in Patent Document 1. The fuel injection valve described in Patent Document 1 includes a nozzle needle that opens and closes an injection hole, and the nozzle needle is biased toward the valve closing direction by the fuel pressure in the control chamber. In addition, a high-pressure supply passage for supplying high-pressure fuel to the control chamber and a discharge passage for discharging the fuel in the control chamber to the low-pressure part are formed. A valve is arranged. The control valve includes a valve body that opens and closes between the intermediate chamber and the discharge passage, and a spring that biases the valve body in a valve closing direction.

  Then, by opening the control valve and discharging the fuel in the control chamber to the low pressure part, the nozzle needle is operated in the valve opening direction to start fuel injection, and the control valve is closed to enter the control chamber. By injecting high-pressure fuel, the nozzle needle is operated in the valve closing direction to terminate fuel injection.

Japanese Patent No. 3827003

  However, in the conventional fuel injection valve, since the valve body and the spring are both disposed in the intermediate chamber, the volume of the intermediate chamber increases. As a result, when fuel injection is started, the drop in the intermediate chamber pressure after the control valve is opened is delayed, and consequently the drop in the control chamber pressure is delayed, and the responsiveness of the fuel injection valve at the start of fuel injection is reduced. To do. Further, when the fuel injection is terminated, the increase in the intermediate chamber pressure after the control valve is closed is delayed, and consequently the increase in the control chamber pressure is delayed, and the responsiveness of the fuel injection valve at the end of the fuel injection is lowered. .

  In view of the above points, the present invention is to improve the responsiveness of a fuel injection valve at the start of fuel injection or at the end of fuel injection in a fuel injection valve of a type that operates a nozzle needle by controlling the pressure in a control chamber. Objective.

In order to achieve the above object, according to the first aspect of the present invention, a nozzle body (21) having an injection hole (211) for injecting high-pressure fuel into a combustion chamber of an internal combustion engine, and a reciprocating motion in the nozzle body A nozzle needle (22) for opening and closing the hole, a control chamber (26) for applying fuel pressure to the nozzle needle in a valve closing direction, an intermediate chamber (323) communicating with the control chamber, and fuel in the intermediate chamber to the low pressure portion Discharge passages (313, 315) for discharging, a high pressure supply passage (322) for supplying high pressure fuel to the control chamber, a spring chamber (325) communicating with the intermediate chamber, an intermediate chamber, and an exhaust passage And a valve body (33) having a shaft portion (332) that is slidably inserted into a portion of the spring chamber on the intermediate chamber side and separates the intermediate chamber and the spring chamber. ) Disposed grayed chamber, and a spring (34) which biases the contact with the valve body to the shaft portion, the spring chamber, and wherein the high pressure fuel is communicated with the high pressure section (25) that circulates To do.

  According to this, since the spring is not disposed in the intermediate chamber, the volume of the intermediate chamber can be reduced. Therefore, the fall of the intermediate chamber pressure after opening the valve element becomes faster, and the increase of the intermediate chamber pressure after closing the valve element becomes faster, so that the fuel injection valve at the start of fuel injection or at the end of fuel injection Responsiveness can be improved.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing which shows the structure of the fuel injection valve which concerns on one Embodiment of this invention. It is an expanded sectional view of the important section of the fuel injection valve concerning one embodiment. It is a time chart for comparing the operating characteristic of the fuel injection valve which concerns on one Embodiment, and the conventional fuel injection valve. It is sectional drawing of the principal part which shows the 1st modification of the fuel injection valve which concerns on one Embodiment. It is sectional drawing of the principal part which shows the 2nd modification of the fuel injection valve which concerns on one Embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The fuel injection valve of the present embodiment shown in FIGS. 1 and 2 supplies high-pressure fuel supplied from a common rail (not shown) to a combustion chamber of a compression ignition type internal combustion engine (hereinafter referred to as an internal combustion engine, not shown). It is to be jetted.

  The fuel injection valve includes an injector body 1, a nozzle 2, a control valve mechanism 3, an actuator 4, a displacement transmission mechanism 5, and a retaining nut 6 as main components.

  The substantially cylindrical injector body 1 is formed with a high-pressure fuel passage 11 through which high-pressure fuel supplied from a common rail flows, and a storage chamber 12 in which the actuator 4 and the displacement transmission mechanism 5 are stored. The storage chamber 12 is connected to a fuel tank (not shown) and is always at a low pressure. The storage chamber 12 corresponds to the low pressure part of the present invention.

  The nozzle 2 includes a substantially bottomed cylindrical nozzle body 21, a substantially columnar nozzle needle 22 slidably inserted into the nozzle body 21, a nozzle spring 23 that biases the nozzle needle 22 in a valve-closing direction, and a cylindrical shape A nozzle cylinder 24 is provided.

  The nozzle body 21 is formed with a nozzle hole 211 through which high-pressure fuel is injected into the combustion chamber of the internal combustion engine, and the nozzle hole 21 is brought into contact with and separated from the nozzle body 21 by the tip (ie, the nozzle hole side end) of the nozzle needle 21. Can be opened and closed.

  A fuel reservoir chamber 25 is formed in the nozzle body 21 as a high-pressure portion to which high-pressure fuel is constantly supplied from the common rail, and the high-pressure fuel from the common rail flows toward the nozzle hole 211 via the fuel reservoir chamber 25. ing.

  The nozzle cylinder 24 is pressed against a second intermediate body 32 to be described later by the nozzle spring 23, and the rear end portion (that is, the end portion on the side opposite to the injection hole) of the nozzle needle 22 is inserted into the nozzle cylinder 24.

  A control chamber 26 in which the internal fuel pressure is switched between a high pressure and a low pressure is formed in the nozzle cylinder 24. The nozzle needle 22 is urged in the valve closing direction by the fuel pressure in the control chamber 26 and is urged in the valve opening direction by the fuel pressure in the fuel reservoir chamber 25. The nozzle cylinder 24 has a stopper surface 241 formed on the inner wall surface that defines the control chamber 26.

  The control valve mechanism 3 that controls the pressure in the control chamber 26 includes a first intermediate body 31, a second intermediate body 32, a valve body 33, a valve body spring 34, a rod 35, a control plate 36, and a plate spring 37. .

  Then, the first intermediate body 31 and the second intermediate body 32 are sandwiched between the injector body 1 and the nozzle 2 and the injector body 1 and the retaining nut 5 are screwed together, so that the components of the fuel injection valve are It is integrated.

  The first intermediate body 31 and the second intermediate body 32 are laminated, the first intermediate body 31 is in contact with the injector body 1, and the second intermediate body 32 is in contact with the nozzle body 21.

  The first intermediate body 31 and the second intermediate body 32 are formed with high-pressure fuel passages 311 and 321 that allow the high-pressure fuel passage 11 of the injector body 1 and the fuel reservoir chamber 25 in the nozzle body 21 to communicate with each other.

  The second intermediate body 32 is formed with a high-pressure supply passage 322 that connects the high-pressure fuel passage 321 and the control chamber 26 to supply high-pressure fuel to the control chamber 26.

  An intermediate chamber 323 is formed on the second intermediate body 32 on the first intermediate body 31 side. The intermediate chamber 323 is always in communication with the control chamber 26 via a first communication passage 324 formed in the second intermediate body 32.

  The second intermediate body 32 is formed with a spring chamber 325 extending from the bottom of the intermediate chamber 323 toward the nozzle body 21 side. The spring chamber 325 is always in communication with the fuel reservoir chamber 25 via a second communication passage 326 formed in the second intermediate body 32.

  In the second intermediate body 32, a flat body high-pressure sheet surface 327 is formed around the opening on the control chamber 26 side in the high-pressure supply passage 322.

  The first intermediate body 31 is formed with a rod insertion hole 312 having one end communicating with the storage chamber 12 and into which the rod 35 is slidably inserted. The first intermediate body 31 is formed with a first discharge passage 313 having one end communicating with the intermediate chamber 323 and the other end communicating with the rod insertion hole 312. The first discharge passage 313 has a diameter larger than that of the rod insertion hole 312 so that the fuel can easily flow on the outer peripheral side of the rod 35.

  In the first intermediate body 31, a flat body low-pressure sheet surface 314 is formed around the opening on the intermediate chamber 323 side in the first discharge passage 313. The first intermediate body 31 is formed with a second discharge passage 315 that allows the storage chamber 12 and the first discharge passage 313 to communicate with each other. The fuel in the intermediate chamber 323 can be discharged to the storage chamber 12 via the first discharge passage 313 and the second discharge passage 315. In addition, the 1st discharge path 313 and the 2nd discharge path 315 comprise the discharge path of this invention.

  The valve body 33 includes a valve portion 331 and a shaft portion 332. The valve portion 331 has a disk shape, is disposed in the intermediate chamber 323, and a flat valve portion low pressure seat surface 331 a is formed at a portion facing the body low pressure seat surface 314. The valve portion 331 opens and closes between the intermediate chamber 323 and the first discharge passage 313 when the valve portion low-pressure seat surface 331a contacts and separates from the body low-pressure seat surface 314.

  The shaft portion 332 has a cylindrical shape and is slidably inserted into a portion of the spring chamber 325 on the intermediate chamber 323 side, and separates the space on the anti-intermediate chamber side of the spring chamber 325 from the intermediate chamber 323.

  The valve body spring 34 is disposed in the spring chamber 325 and abuts against the shaft portion 332 to urge the valve body 33 toward the body low pressure seat surface 314.

  The control plate 36 has a disc shape, is disposed in the control chamber 26, and a flat plate sheet surface 361 is formed at a portion facing the body high-pressure sheet surface 327. Then, the control plate 36 is reciprocated between the body high-pressure sheet surface 327 and the stopper surface 241, and the plate sheet surface 361 comes into contact with and separates from the body high-pressure sheet surface 327 so that the control chamber 26 and the high-pressure supply passage 322 are separated. It opens and closes.

  When the control plate 36 is in contact with the stopper surface 241, the control chamber 26 is separated into two spaces by the control plate 36. Specifically, a control chamber formed between the control plate 36 and the second intermediate body 32 (hereinafter, this space is referred to as an intermediate body side control chamber if necessary), the control plate 36 and the nozzle needle 2 (Hereinafter, this space is referred to as a needle-side control chamber if necessary).

  The plate spring 37 is disposed in the control chamber 26 and biases the control plate 36 toward the body high-pressure seat surface 327.

  A communication hole 362 penetrating in the axial direction of the control plate 36 is formed in the central portion of the control plate 36 in the radial direction.

  The control plate 36 abuts on the body high-pressure sheet surface 327, whereby the high-pressure supply passage 322 is closed and the space between the control chamber 26 and the high-pressure supply passage 322 is closed. Further, when the control plate 36 is in contact with the body high-pressure seat surface 327, the communication hole 362 and the first communication passage 324 are in communication.

  The actuator 4 as a driving means is configured by a cylindrical piezo element stack that is stacked with a large number of piezo elements and expands and contracts by charge and discharge.

  The displacement transmission mechanism 5 includes a piston cylinder 51 and two pistons 52 and 53 slidably inserted into the piston cylinder 51. A liquid chamber 54 filled with fuel is formed between the two pistons 52 and 53.

  The first piston 52 is directly driven by the actuator 4. When the actuator 4 is extended, the pressure of the liquid chamber 54 is increased by the first piston 52.

  The second piston 53 has a smaller diameter than the first piston 52 and operates under the pressure of the liquid chamber 54, and the displacement of the second piston 53 is transmitted to the valve body 33 via the rod 35. Yes.

  When the actuator 4 is extended, the valve body 33 is driven by the actuator 4 in a direction away from the body low-pressure seat surface 314. At that time, the change in the length of the actuator 4 is expanded by the pressure receiving area ratio between the first piston 52 and the second piston 53 and transmitted to the valve body 33.

  Next, the operation of the fuel injection valve will be described. First, when the actuator 4 is charged when the needle is closed (that is, the nozzle hole 211 is closed), the actuator 4 is extended and the first piston 52 is driven, and the first piston 52 drives the liquid. The pressure in the chamber 54 is increased. The second piston 53 is driven toward the valve body 33 by the pressure of the liquid chamber 54 that has been increased in pressure.

  Further, the displacement of the second piston 53 is transmitted to the valve body 33 via the rod 35, so that the valve body 33 is driven in a direction away from the body low pressure seat surface 314 against the urging force of the valve body spring 34. Is done.

  When the valve body 33 moves away from the body low pressure seat surface 314 and the intermediate chamber 323 communicates with the first discharge passage 313 by the movement of the valve body 33, the fuel in the intermediate chamber 323 and the first communication passage 324 is discharged. It flows out into the storage chamber 12 and the pressure in the intermediate body side control chamber of the control chamber 26 is lowered.

  Thereby, the control plate 36 is moved to the second intermediate body 32 side by the pressure of the needle side control chamber rather than the force that the control plate 36 is urged toward the nozzle needle 2 side by the pressure of the intermediate body side control chamber. Since the force urged toward the head increases, the control plate 36 moves toward the second intermediate body 32 side.

  Then, the control plate 36 comes into contact with the body high pressure seat surface 327, the high pressure supply passage 322 is closed by the control plate 36, and the supply of high pressure fuel to the intermediate body side control chamber is stopped. Further, the fuel in the needle side control chamber flows out into the storage chamber 12 through the communication hole 362, the first communication passage 324, etc., and the pressure in the needle side control chamber is reduced. As a result, the force for urging the nozzle needle 22 in the valve closing direction is reduced, so that the nozzle needle 22 moves in the valve opening direction, and fuel is injected from the injection hole 211 into the combustion chamber of the internal combustion engine.

  Thereafter, when the electric charge of the actuator 4 is discharged, the actuator 4 contracts and the pressure in the liquid chamber 54 decreases, so that the valve body 33, the rod 35, and the second piston 53 are pushed back by the valve body spring 34.

  When the valve body 33 is brought into contact with the body low pressure seat surface 314 and the space between the intermediate chamber 323 and the first discharge passage 313 is closed by the movement of the valve body 33, the fuel in the intermediate chamber 323 and the first communication passage 324 is removed. The outflow stops and the first communication passage 324 and the intermediate body side control chamber have the same pressure.

  Thereby, the control plate 36 is controlled by the pressure of the first communication passage 324 and the high pressure supply passage 322 rather than the force of the control plate 36 being biased toward the second intermediate body 32 by the pressure of the needle side control chamber. Since the force urged toward the nozzle needle 2 side becomes larger, the control plate 36 moves toward the nozzle needle 2 side.

  Then, the high pressure fuel that has flowed into the intermediate body side control chamber from the high pressure supply passage 322 flows into the needle side control chamber through the communication hole 362, with the control plate 36 coming into contact with the stopper surface 241. Thus, when high pressure fuel flows into the needle side control chamber, the nozzle needle 2 moves in the valve closing direction, the nozzle hole 211 is closed, and fuel injection is completed.

  Next, a difference in operating characteristics between the fuel injection valve of the present embodiment and the conventional fuel injection valve will be described with reference to FIG.

  In FIG. 3, the solid line is the characteristic line of the fuel injection valve according to this embodiment, and the alternate long and short dash line is the characteristic line of the conventional fuel injection valve. In FIG. 3, Pl is the fuel pressure in the control chamber 26 (more specifically, the intermediate body side control chamber) when the control plate 36 starts moving toward the nozzle needle 2 side.

  In the fuel injection valve according to this embodiment, since the valve spring 34 is not disposed in the intermediate chamber 323, the volume of the intermediate chamber 323 can be reduced. Therefore, in the fuel injection valve according to this embodiment, at the start of fuel injection, the pressure drop in the intermediate chamber 323 after the valve element 33 is opened becomes faster than the conventional fuel injection valve (see (c) Intermediate chamber pressure). ) As a result, the pressure drop in the control chamber 26 is accelerated (see (e) control chamber pressure).

  As a result, in the fuel injection valve of the present embodiment, the lift start timing of the nozzle needle 2 is earlier than that of the conventional fuel injection valve (see (f) Needle lift), and thus the injection start is earlier by the time a. (See (g) Injection rate).

  Further, in the fuel injection valve according to the present embodiment, at the end of fuel injection, the pressure increase in the intermediate chamber 323 after the valve element 33 is closed becomes faster than the conventional fuel injection valve (see (c) Intermediate chamber pressure). ) As a result, the pressure increase in the control chamber 26 is accelerated (see (e) control chamber pressure).

  As a result, in the fuel injection valve of the present embodiment, the lowering end timing of the nozzle needle 2 is earlier than that of the conventional fuel injection valve (see (f) Needle lift), and thus the injection end is earlier by time b. (See (g) Injection rate).

  Therefore, according to this embodiment, since the volume of the intermediate chamber 323 can be reduced, the pressure drop and pressure increase of the intermediate chamber 323 are accelerated, and the response of the fuel injection valve at the start of fuel injection or at the end of fuel injection Can be improved.

  Further, when the fuel injection is terminated, the high pressure supply passage 322 is closed by the control plate 36 and the supply of the high pressure fuel to the control chamber 26 is stopped, so that the pressure drop in the control chamber 26 is further accelerated and the fuel injection starts. The responsiveness of the fuel injection valve at the time can be further improved.

  In the above-described embodiment, the spring chamber 325 is always in communication with the fuel reservoir 25. However, as in the first modification shown in FIG. 4, the spring chamber 325 is accommodated via the second communication passage 326. 12 may be in constant communication.

  In the case of the first modification, when the valve element 33 is in a state where the intermediate chamber 323 and the first discharge passage 313 are closed, the high-pressure fuel in the intermediate chamber 323 passes through the spring chamber 325 and the second communication passage 326. Thus, a so-called static leak that leaks to the storage chamber 12 side occurs.

  However, in the case of the first modified example, since the pressure of the spring chamber 325 is low, the driving force when driving the valve element 33 in the direction in which the volume of the spring chamber 325 decreases can be reduced, and the driving energy of the actuator 4 can be reduced. There is an advantage that can be reduced.

  On the other hand, in the case of the above-described embodiment, the static leak as in the first modification does not occur, so that the high-pressure fuel supply amount of the supply pump that supplies high-pressure fuel to the common rail can be reduced, and the drive pump drive energy is reduced. can do.

  In the above embodiment, the body low pressure seat surface 314 and the valve portion low pressure seat surface 331a are both flat surfaces. However, as in the second modification shown in FIG. Both the sheet surfaces 331a may be tapered surfaces.

  Incidentally, since the allowable amount of the coaxiality between the rod insertion hole 312 and the spring chamber 325 is larger in the above embodiment than in the second modification, the above embodiment is easier to manufacture.

(Other embodiments)
In the above embodiment, the valve portion 331 and the shaft portion 332 are integrated, but the valve portion 331 and the shaft portion 332 may be separated.

  In addition, this invention is not limited to above-described embodiment, In the range described in the claim, it can change suitably.

  Further, in the above-described embodiment, it is needless to say that elements constituting the embodiment are not necessarily indispensable except for the case where it is clearly indicated that the element is essential and the case where the element is clearly considered to be essential in principle. .

  Further, in the above embodiment, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, it is particularly limited to a specific number when clearly indicated as essential and in principle. The number is not limited to a specific number except for cases.

  In the above embodiment, when referring to the shape, positional relationship, etc. of components, the shape, position, etc., unless otherwise specified and in principle limited to a specific shape, positional relationship, etc. It is not limited to relationships.

12 Storage room (low pressure part)
21 Nozzle body 22 Nozzle needle 26 Control chamber 33 Valve element 34 Spring 211 Injection hole 313 First discharge passage (discharge passage)
315 Second discharge passage (discharge passage)
322 High pressure supply passage 323 Intermediate chamber 325 Spring chamber 331 Valve portion 332 Shaft portion

Claims (3)

A nozzle body (21) having an injection hole (211) for injecting high pressure fuel into the combustion chamber of the internal combustion engine;
A nozzle needle (22) that reciprocates in the nozzle body to open and close the nozzle hole;
A control chamber (26) for applying a fuel pressure toward the valve closing to the nozzle needle;
An intermediate chamber (323) communicating with the control room;
Discharge passages (313, 315) for discharging the fuel in the intermediate chamber to the low pressure section (12);
A high pressure supply passage (322) for supplying high pressure fuel to the control chamber;
A spring chamber (325) communicating with the intermediate chamber;
A valve portion (331) disposed in the intermediate chamber and opening and closing between the intermediate chamber and the discharge passage; and a slidably inserted into a portion of the spring chamber on the intermediate chamber side; A valve body (33) having a shaft portion (332) separating the spring chamber;
A spring (34) disposed in the spring chamber and urging the valve body in contact with the shaft portion ;
The fuel injection valve according to claim 1, wherein the spring chamber communicates with a high pressure portion (25) through which the high pressure fuel flows . A first intermediate body (31) in which the discharge passage is formed;
A flat body low pressure sheet surface (314) formed in the first intermediate body and surrounding an opening on the intermediate chamber side in the discharge passage;
Claim 1, characterized in that it comprises are formed in the valve unit, the flat valve portion pressure seat surface for opening and closing between said discharge passage and said intermediate chamber apart contact with the body pressure seat surface and (331a) fuel injection valve according to. A second intermediate body (32) in which the high-pressure supply passage is formed;
A body high-pressure seat surface (327) formed in the second intermediate body and surrounding an opening on the control chamber side in the high-pressure supply passage;
A control plate (36) disposed in the control chamber and closing the space between the control chamber and the high-pressure supply passage in contact with the body high-pressure sheet surface when the intermediate chamber and the discharge passage communicate with each other; The fuel injection valve according to claim 1 or 2 , wherein

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