JPH0233871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for injecting and supplying fuel into a combustion chamber of an internal combustion engine.

Conventionally, in fuel injection valves, the lift amount of the needle valve is determined by taking into account the performance characteristics of the engine speed and load over the entire range, and the maximum lift amount is constant, and the lift amount is fixed within the maximum lift amount from high speed to low speed range It is used in the entire range from high injection amount to low injection amount.

Therefore, trapvuorium (dead)
With conventional fuel injection devices for diesel engines having a large volume, it is difficult to ensure accurate metering of the amount of fuel to be injected when used in small engines that require a small amount of injection. In other words, in the low speed range and low injection amount range, the needle valve of the injection valve does not lift completely, so when the lift amount changes due to disturbance, the residual pressure changes, affecting the next lift amount, and this lift amount is determined by the nozzle spring. It becomes difficult to balance the fuel in an appropriate state, making it impossible to control the fuel injection amount accurately, making the injection characteristics (Q characteristics) unstable, and causing abnormal injections such as asymmetric injection to occur, causing exhaust gas There was a problem that had an adverse effect on characteristics, noise, etc. Therefore, in order to achieve stable idle rotation, the actual injection quantity must be set to a relatively large amount compared to the theoretically small injection quantity, and the idle rotation speed must be maintained at a high state. However, it had the disadvantage of high fuel consumption.

The present invention has been made to solve the problems of the above-mentioned conventional fuel injection valve, and embodiments thereof will be described below with reference to the drawings.

In the figure, reference numeral 1 indicates a main body of a fuel injection device according to an embodiment of the present invention, and a nozzle holder 2 has an injection nozzle 4 having an injection hole 3 formed at its tip.
is disposed via a fuel supply path guide piece 5, and a needle valve 6 slidably passes through the injection nozzle 4. This injection nozzle 4 is attached to the nozzle holder 2 by a nozzle nut 7. The upper end of the needle valve 6 is a spring storage hole 8 formed in the middle part of the nozzle holder 2.
It is connected to the lower end of a movable spring seat 9 that is slidably housed inside. The middle part of the movable spring seat 9 is enlarged and formed as an integral spring seat part 10.
A nozzle spring 12 is interposed between the spacer 11 and the spacer 11 . The lower part of the spacer 11 is inserted into the spring storage hole 8 and is screwed into the nozzle holder 2 via a threaded part 13 formed in the upper part. By rotating this spacer 11 and moving it up and down, the set load of the nozzle spring 12 is adjusted to obtain a predetermined fuel injection pressure. A driver groove 14 is formed at the upper end of the spacer 11 . A lift amount adjusting device 15 is screwed onto the upper part of the nozzle holder 2 via a threaded portion 16 .

A piston 18 is fitted into a cylinder 17 in the lift amount adjusting device 15 so as to be slidable along a direction intersecting the operating direction of the movable spring seat 9.
The cross-sectional shape of the cylinder 17 is formed into a substantially elliptical shape with the upper and lower sides flattened as shown in FIG. 1
8 is housed so that it does not rotate. A contact surface 20 is formed on the movable spring seat 9 side of the piston 18, with which the upper end 19 of the connecting rod 9a of the movable spring seat 9 can abut. As shown in detail in FIG. 3, the contact surface 20 is divided into three steps 20a, 20b, and 20c, and is formed in a stepwise manner. A small lift amount can be obtained by the spacing l ₁ , l ₂ between the upper end 19 of the spring seat 9 and the steps 20a, 20b of the contact surface 20, and the maximum lift amount is determined by the step portion 6a of the needle valve 6, as will be described later.
and the lower end surface 5a of the fuel supply path guide piece 5
As obtained by l ₃ .

On the side of the piston 18 opposite to the movable spring seat 9, a locking portion 22 with a stopper 21 is formed in the shape of a groove along the axial direction. Locking part 22 and stopper 21
As will be described later, the fixed position of the piston 18, that is, the abutment surface 20 is selected by the latched state. The stopper 21 is actuated so as to be able to protrude and retract by an actuator 23 consisting of a solenoid. The actuator 23 is controlled by an electronic control device 24, which will be described later. The piston 18 is pressed leftward by a pressing spring 26 housed in the right chamber 25 of the cylinder 17. piston 1
A stopper 18a is formed protrudingly in a cylindrical shape at the right end of the spring 8, surrounding the pressure spring 26. This stopper 1
8a defines the rightmost position of the piston 18. The left end 18b of the piston 18 is the piston 18
When the piston 18 is deflected to the leftmost side, the piston 18 comes into contact with the left end wall of the cylinder 17 to define the leftmost deflection position of the piston 18 . A hydraulic circuit 28 is provided in the left chamber 27 of the cylinder 17.
has been contacted. The hydraulic circuit 28 includes a fuel tank 29, a fuel feed pump 30 connected to the tank 29, and an electromagnetic switching valve 31 interposed between the feed pump 30 and the left chamber 27. The switching valve 31 is connected to the pipe line 3 on the feed pump 30 side.
2 and the return side pipe line 33, and functions as a control valve to supply constant fuel pressure sent by the feed pump 30 when necessary. This closes the pipe 32 on the feed pump 30 side and opens the return pipe 33, and the solenoid is energized by a control signal supplied from the electronic control device 24 to close the pipe 32 on the feed pump 30 side. The switching operation is performed so as to open the line 32 and cut off the return side pipe line 33.

In FIG. 2, reference numerals 34 and 35 indicate conduits that are connected to a lift amount adjusting device 15 similar to the above-described device of another fuel injection device (not shown). Code 36,
Reference numerals 37 denote a rotation speed sensor and a load sensor that detect the engine rotation speed and load, respectively. Rotation speed sensor 3
6 is installed, for example, on the crankshaft of an engine to detect its rotational speed. Load sensor 3
Reference numeral 7 is connected to, for example, a control lever of a fuel injection pump of a vehicle, and detects a load corresponding to the amount of displacement of the lever.

In FIG. 1, reference numeral 38 is a through hole drilled in the spacer 11 through which leaked oil passes. The leaked oil rises from the spring storage hole 8 through between the spacer 11 and the nozzle holder 2, enters between the spacer 11 and the connecting rod 9a of the movable spring seat 9 through the through hole 38, and rises along the connecting rod 9a. Then, it passes through the space 39 in the lift amount adjusting device 15 and the communication hole 40, and returns to the fuel tank 29 through the through hole 42 of the bolt 41 that communicates with the communication hole 40. Reference numeral 43 denotes a fuel passage through which fuel supplied from a fuel injection pump (not shown) is introduced into the pressurized space 44 within the injection nozzle 4 via an injection pipe (not shown).

In FIG. 1, reference numeral 45 indicates a fixing screw, and after setting the spacer 11 at a predetermined position with respect to the nozzle holder 2 and setting the fuel injection pressure, the spacer 11 is attached.
1 and nozzle holder 2, and
This ensures that the set load does not deviate.

To explain the operation of the fuel injection device having the above-mentioned configuration, the fuel pumped by the fuel injection pump is supplied to the pressurized space 44 of the injection nozzle 4 via the injection pipe and the fuel passage 43, and the pressure inside the pressurized space 44 increases. When the pressure exceeds the fuel injection valve opening pressure set by the nozzle spring 12, the needle valve 6 moves upward. Lift amount adjustment device 15
As will be described later, one of the three step portions 20a, 20b, and 20c of the abutment surface 20 formed on the piston 18 is selected. This selection is determined depending on the engine speed and load. The lift amount of the needle valve 6 is determined by the three steps 20a, 20 of the contact surface 20.
It is determined as described below depending on the selection of b and 20c. After the lift of the needle valve 6 is completed, when the pressure of the fuel supplied by the fuel injection pump decreases, the movable spring seat 9 is moved down by the force of the nozzle spring 12, and the needle valve 6 is seated to inject fuel. ends.

FIGS. 3A, 3B, and 3C are explanatory diagrams showing the engagement relationship between the piston 18 of the lift amount adjusting device 15, the connecting rod 9a of the movable spring seat 9, and the stopper 21. FIG. 3a shows the position of the piston 18 when the engine is stopped and started. That is, when the engine speed is 1/4 or less of the engine's rated speed and the engine is under no-load operating conditions, the electronic control unit 24 operates based on the input signals from each speed sensor 36 and load sensor 37.
The values of the command signals S ₁ and S ₂ supplied to the actuator 23 of the stopper 21 and the solenoids of the electromagnetic switching valve 31 of the hydraulic circuit 28 are set to zero. Therefore, since the solenoid of the actuator 23 does not operate, the stopper 21 is retracted by a return spring (not shown) to a position where it is not engaged with the engagement portion 22 of the piston 18. On the other hand, since the solenoid of the switching valve 31 of the hydraulic circuit 28 does not operate, the pipe line 32 on the feed pump 30 side is closed, and the pipe line 33 on the return side is opened, so that the pressure inside the left chamber 27 of the cylinder 17 is reduced. It becomes zero. Therefore, the piston 18
is displaced to the leftmost position by the force of the pressing spring 26,
The right step portion 20a of the stepped contact surface 20 of the piston 18 is located facing the upper end portion 19 of the movable spring seat 9 (FIG. 3a). When the movable spring seat 9 is seated, the stepped portion 20a is formed at the upper end 1 of the spring seat 19.
The distance l ₁ between the step portion 9 and the stepped portion 20a is set to a value that provides a predetermined minimum lift amount. Therefore, even when the engine speed is low and the lift amount of the needle valve 6 is small, such as when there is no load, the needle valve 6 does not maintain the piston 1.
The amount of lift until the upper end 19 of the movable spring seat 9 abuts against the step 20a of the contact surface 20 of 8 is the step 20.
Since the needle valve 6 is always fully lifted to perform injection, the lift amount at the minimum lift is determined at the position where the nozzle spring and fuel injection pressure are balanced, as in the conventional example. Unlike the conventional method, there is no asymmetric injection, and the accuracy of adjusting the fuel injection amount is improved. In addition, in the past, the amount of fuel injection was relatively high when the engine speed was low and there was no load to avoid uneven injection, but since this is not necessary, it is It is possible to keep the fuel injection amount low. FIG. 4 is a graph showing the relationship between the engine speed N and the lift amount l of the needle valve 6. The lift amount l ₁ of the needle valve 6 when the engine is at a low speed and under no load is shown in FIG. Indicated by A.

Figure 3b shows that the engine speed is 1/4 to 2/4 of the rated speed.
The position of the piston 18 under engine operating conditions in which the load is less than 1/4 of the maximum load is shown in between. Under this engine operating condition, the electronic control device 24 supplies the ON operation command signal S 1 to the actuator 23 of the stopper 21, and also supplies the solenoid switching valve 31 of the hydraulic circuit 28 with a command signal S ₁ for ON operation.
A command signal _S2 for ON operation is supplied for a predetermined period of time long enough to perform the operation described later. This results in
The switching valve 31 connects the pipe line 32 on the feed pump 30 side to the left side 27 of the cylinder 17 . Left chamber 2
The pressure inside 7 increases and the piston 18 presses against the pressure spring 26.
Once the stopper 18a is stopped by the cylinder 17 against the force of
deflects until it touches the right end wall of the At this time, the command signal S ₁ supplied by the electronic control device 24
actuator 23 is actuated and stopper 2
1 is projected, and the stopper 21 is fitted into the locking portion 22 of the piston 18 (see the dotted line in FIG. 3b). Then, S ₁ from the electronic control unit 24 becomes zero after the above-mentioned predetermined time has elapsed, and the switching valve 31 is operated to cut off the pipe line 32 on the feed pump 30 side, and connect the pipe line 33 on the return side. As a result, the pressure in the left chamber 27 of the cylinder 17 becomes zero, so the piston 18 moves to the left by the force of the pressing spring 26. Right end 22a of locking portion 22 of piston 18
collides with and locks against the protruding stopper 21,
The piston 18 stops at this position. In this position, the central step 20b of the three steps on the abutting surface 20 of the piston 18 faces the upper end 19 of the connecting rod 9a of the movable spring seat 9, and the upper end 19 faces the step 20b.
It will be in a state where it can come into contact with 0b. At this time, the distance l ₂ between the upper end portion 19 and the stepped portion 20b is set to a value that provides a predetermined intermediate lift amount. The lift amount l ₂ of the needle valve 6 at this time is indicated by the symbol B in FIG.

FIG. 3c shows the position of the piston 18 under engine operating conditions where the engine speed is 2/4 or more of the rated speed and the load is 1/4 or more of the maximum load. Under these engine operating conditions, the electronic control unit 24 controls the stopper 21.
The value of the command signal S ₁ for the actuator 23 is set to zero, and the command signal S ₂ for ON operation is supplied to the switching valve 31 of the hydraulic circuit 28 . Since the solenoid of the actuator 23 is no longer energized, the stopper 21 is retracted by the built-in return spring, and the locking portion 22 of the piston 18 is released from the locking state with the stopper 21. On the other hand, the switching valve 31 switches to feed the feed pump 30.
The fuel supplied by the feed pump 30 is communicated with the left side pipe 32 of the cylinder 17.
7 will be introduced. As a result, the pressure inside the left chamber 27 increases, so the piston 18 moves to the right against the force of the pressure spring 26, and the stopper 18a formed at the right end of the piston 18 comes into contact with the right end wall of the cylinder 17. The piston 18 stops at this position. This position is the rightmost position of the piston 18. In this position, the left step 20c of the three steps of the contact surface 20 of the piston 18 faces the upper end 19 of the connecting rod 9a of the movable spring seat 9. The maximum lift amount of the needle valve is determined by the distance _l3 between the upper step 6a and the lower end surface 5a of the fuel supply path guide piece 5, but the upper end of the connecting rod 9a of the movable spring seat 9 Distance l ₄ between part 19 and stepped part 20c of piston 18
is set larger than the interval _l3 that defines the maximum lift amount. Therefore, the upper end portion 19 does not collide with the stepped portion 20c even at the maximum lift. The lift amount _l3 of the needle valve 6 at this time is indicated by the symbol c in FIG.

In order to assemble the fuel injection device having the above configuration and set the required lift amounts l ₁ and l ₂ in advance, the length of the connecting rod 9a of the movable spring seat 9 and/or the dimension of the stepped portion 15a of the lift amount adjusting device 15 must be set in advance. Alternatively, the dimensions of the upper end surface 2a of the nozzle holder 2 may be set relatively, and those with different dimensions may be selectively assembled, or additional processing may be performed to match the required dimensions, and an appropriate thickness may be set as necessary. Adjust using shims, etc.

As described above, according to the present invention, a lift amount adjusting device is provided in a fuel injection device for an internal combustion engine, and the lift amount of a needle valve is selected to a required value according to engine operating conditions. As a result, the accuracy of fuel metering is improved, and asymmetric injection can be avoided. Therefore, stable rotation can be achieved with a low fuel injection amount, especially when the engine is at low rotational speed and under no load, making it possible to lower the idle rotational speed and improve fuel efficiency. Also,
Since asymmetric injection can be prevented, exhaust gas characteristics are improved, car knocking, etc. can be prevented, and engine noise can also be reduced.
In addition, since the piston, which is a stopper that regulates the lift amount of the needle valve, is provided so as to be slidable along the direction that intersects the operating direction of the movable spring seat, when the movable spring seat comes into contact with the piston, The piston does not move in the operating direction of the movable spring seat due to impact force, and the lift amount of the needle valve can be physically fixed at a certain value easily and reliably.

Furthermore, since the abutment surface of the piston that the movable spring seat upper end comes into contact with is composed of a plurality of steps formed in steps in the axial direction of the piston, the movable spring seat is always movable at only one abutment surface. Compared to the case where the spring seat contacts, the frequency of wear of the contact surface is extremely low, and the lift amount of the needle valve relative to the engine rotation speed can be controlled with high accuracy over a long period of time.

[Brief explanation of drawings]

The drawings show a fuel injection device according to an embodiment of the present invention, in which FIG. 1 is a sectional view of the fuel injection device, FIG. 2 is a partial sectional view taken along the line of FIG. 1, and FIG.
c is an explanatory diagram showing the relationship between the operating position of the piston of the lift amount adjusting device and the movable spring seat, and FIG. 4 is a graph showing the relationship between the engine rotational speed N and the needle valve lift amount l. DESCRIPTION OF SYMBOLS 1... Fuel injection device, 2... Nozzle holder, 4... Injection nozzle, 6... Needle valve, 9... Movable spring seat, 12... Nozzle spring, 15... Lift amount adjustment device, 18... Piston, 19... Upper end part, 20... Contact surface, 21...stopper, 22...engaging portion, 23...actuator, 2
4...Electronic control device, 28...Hydraulic circuit.

Claims (1)

[Claims] 1 Consisting of an injection nozzle and a nozzle holder, a nozzle spring and a movable spring seat connected to a needle valve held in a seated position by the nozzle spring are provided in the nozzle holder, and the lift amount of the needle valve is controlled. In a fuel injection device for an internal combustion engine that controls the amount of fuel to a required amount according to engine operating conditions, the movable spring seat has a contact surface on which the upper end of the movable spring seat that moves upward during injection can come into contact. A hydraulic circuit having a piston that is slidably provided along a direction intersecting an operating direction, a control valve that operates the piston, a stopper that fixes the piston at a predetermined position, and an actuator that operates the stopper to protrude and retract. an electronic control device that controls the control valve of the hydraulic circuit and the actuator according to engine operating conditions; and a sensor that detects the engine operating conditions; The electronic control device controls the control valve of the hydraulic circuit and the actuator according to the output of the sensor to displace the piston and move the movable spring seat. An internal combustion engine characterized by comprising a lift adjustment device that displaces a contact surface of the piston facing the upper end and selects a lift amount of the needle valve to a required amount corresponding to engine operating conditions. fuel injector.