JPH0517420Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a unit injector for diesel engines, and in particular improves a type that can control the fuel injection timing using a conventional electromagnetic valve. The present invention relates to a unit injector that provides a constant supply amount, prevents uneven rotation of the engine, and provides good fuel injection.

Prior Art Conventional unit injectors generally have the disadvantage that the timing of fuel injection cannot be controlled. As an improvement on this, a unit injector has been put into practical use in which the fuel injection timing is electronically controlled by opening and closing a solenoid valve. In this unit injector, a single fuel gear is formed in the injector body, and a spill port communicates from the fuel gear to the lower side of the injection plunger, and fuel is metered to the fuel gear to supply fuel to the fuel gear. A normal fuel feed pump was used, which does not have this function. The injection plunger is constantly pressed downward by a spring from a part of the injector body, and the amount of fuel supplied is determined by the balance between the pressing force of this spring and the fuel pressure acting on the lower side of the injection plunger. As a result, the amount of fuel injected for each fuel injection or for each cylinder is difficult to be constant, which has the disadvantage of causing uneven rotation of the engine. Furthermore, the cutoff of the fuel injection at the end of the fuel injection was not very good.

Furthermore, Japanese Patent Laid-Open No. 59-192841 discloses a fuel injection device, but the conventional example does not have a special mechanism for reducing the injection amount to zero for the reduced cylinder, and effectively controls the injection amount for the reduced cylinder. It is possible to cut off and control the fuel supply, and the second
Fuel gear _G2 , check valve 9, fuel passage 6, third
The structure of Spill Port S ₃ etc. is not disclosed or suggested at all. Therefore, this prior art example is a different device with completely different objectives, configurations, and effects from the device of the present application.

Furthermore, Japanese Patent Application Laid-Open No. 59-153968 discloses a fuel injection device for an internal combustion engine, but this conventional example makes it easier to control the injection amount by making the injection amount more accurately correspond to the opening timing of the metering needle. , the purpose is to achieve high precision, and as in the present application, the needle 24
There is no mention of applying pressure from above to improve the sharpness of the jet, and therefore the invention is completely different in purpose, structure, and operation and effect from the invention of the present application.

Further, Japanese Patent Application Laid-Open No. 58-190563 discloses an electrically controlled unit injector, but the conventional example is controlled by a single solenoid type three-way valve device, and the three-way valve device is configured to control the fuel to be metered. of the second fuel gear G ₂ , as in the present application, and to significantly reduce the sensitivity of the control device to design parameters.
The relationship between the check valve 9 and the fuel passage 6 is not disclosed or suggested at all. Therefore, the conventional example is also a different device having a different purpose, structure, and effect from the present invention.

Purpose The present invention was made in order to eliminate the drawbacks of the prior art described above, and its purpose is to provide a unit injector equipped with a solenoid valve for fuel injection timing control under the fuel plunger. A second fuel gear lary is provided on the side independently of the first fuel gear lary above the injection plunger, and the second fuel gear lary is provided with a check valve and has a function of metering and supplying fuel. By supplying fuel with a distributed fuel feed pump, the amount of fuel injected for each injection or for each cylinder is made constant, and uneven rotation of the engine is thereby prevented. Another object of the invention is that when the injection plunger reaches the bottom dead center, the high-pressure fuel compressed by the pressure-feeding plunger acts on the needle head of the nozzle to forcefully press the needle into the injection hole of the nozzle. By providing a fuel passage with a diameter of 100 mm, it is possible to improve the cutoff of fuel injection at the end of injection.

Configuration In short, the present invention includes an injector body, a first fuel gear formed in the injector body and connected to a fuel feed pump, and a first fuel gear that is biased in one direction by a spring and is slidably accommodated in the injector body. In the injector, the injection plunger is slidably housed in the injector body, and an electromagnetic valve for controlling the fuel injection timing, when the pressure plunger is at the top dead center. a first spill port that is open and communicates with the first fuel gear; a second spill port that opens near the bottom dead center of the pressure-feeding plunger and is controlled to open and close by the solenoid valve; and a second spill port that is opened and closed near the bottom dead center of the injection plunger; a third spill port that is opened in the vicinity and communicates with the first fuel gear; a fuel passage that communicates and connects the third spill port with a needle chamber in which a head of a needle attached to the nozzle is accommodated; a fuel injection passage that opens near the bottom dead center of the plunger and communicates with the nozzle; a second fuel gear gallery that opens near the bottom dead center of the injection plunger and communicates with the nozzle; A check valve having a structure to prevent fuel from flowing out and a distribution type fuel feed pump for metering the fuel and discharging a specified amount of fuel are provided, and the distribution type fuel feed pump is connected to the second fuel gear gallery. This is a characteristic feature.

The present invention will be explained below based on embodiments shown in the drawings. In FIG. 1, a unit injector 1 according to the present invention includes an injector body 2, a first fuel gear _G1 , a pressure-feeding plunger 3, an injection plunger 4, and a solenoid valve 5.
A first spill port _S1 , a second spill port _S2 ,
A third spill port _S3 , a fuel passage 6, a fuel injection passage 8, a second fuel gear _G2 , a check valve 9,
A distribution type fuel feed pump 10 is provided.

The injector main body 2 is formed to have a cross-sectional shape as shown in _FIG.
is formed in the injector main body 2, is communicatively connected to the fuel feed pump 11 by a first fuel pipe _P1 , and surrounds a plunger chamber 13 in which a pressure-feeding plunger 3 and an injection plunger 4 are housed so as to be slidable in the vertical direction. The partition wall 2a is formed in a part of the partition wall 2a.
The fuel passage 13 is separated by the partition wall 2a, and the fuel passage 13 is configured to be opened and closed by the solenoid valve 5.

The pressure-feeding plunger 3 is biased in one direction by a spring 14, and is slidably accommodated in the injector main body 2, and has a flange portion 3a on its upper part.
is formed, and the flange portion is the upper end 14 of the spring 14.
A is supported, and a cam 16 fixed to a camshaft 15 contacts the flange portion and rotates in the direction of arrow A, so that the pressure-feeding plunger 3 reciprocates in the vertical direction.

The injection plunger 4, like the pressure-feeding plunger 3, is slidably housed within the injector body 2, and a spring (not shown) that presses the injection plunger 4 downward as in the conventional example is not used. Not yet. The lengths of the pressure-feeding plunger 3 and the injection plunger 4 are such that the lower end 3b of the pressure-feeding plunger 3, the upper end 4a and the lower end 4b of the injection plunger 4 are connected to the first spill port _S1 , the second spill port _S2 , and the third spill port, respectively.
It is determined by the timing of encountering spill port _S3 , etc.

The electromagnetic valve 5 includes an electromagnetic solenoid 18, a plunger 19 attracted by the electromagnetic solenoid,
The electromagnetic solenoid 18 is connected to an electronic circuit (not shown) via terminals 18a and 18b, and energization or deenergization of the electromagnetic solenoid 18 is electronically controlled. The opening and closing of the fuel passage 13 and the second spill port _S2 are also electronically controlled. The first fuel gear G ₁ and the fuel passage 13 communicate with each other through the valve body 20 of the solenoid valve 5, and when the valve body 20 is seated on the valve seat 21, this communication is cut off. 20 is configured so that this portion communicates when it moves downward as shown in FIG.

The first spill port S ₁ is opened when the pressure-feeding plunger 3 is at the top dead center, and the first spill port S 1 is opened when the pressure-feeding plunger 3 is at the top dead center.
It is formed in a position that communicates with _G1 . The second spill port S ₂ opens near the bottom dead center of the pressure-feeding plunger 3 and is configured to be opened and closed by the solenoid valve 5 . 3rd spill port
_S3 is opened near the bottom dead center of the injection plunger 4 and is provided at a position communicating with the first fuel gear _G1 .

The fuel passage 6 is connected to the third spill port _S3 and the nozzle 2.
The head 24a of the needle 24 attached to the needle 24 and the needle chamber 25 in which the spring 30 is housed are connected in communication with each other, and the purpose is to improve the sharpness of the fuel injection at the end of the fuel injection. It is.

The fuel injection passage 8 opens near the bottom dead center of the injection plunger 4, and communicates with the nozzle 23, through which high-pressure fuel compressed by the injection plunger 4 flows from the fuel injection port 23a of the nozzle 23 into the combustion engine of the engine. The liquid is injected into a chamber (not shown).

The second fuel gear _G2 communicates with the plunger chamber 13 near the bottom dead center of the injection plunger 4, and is formed independently of the first fuel gear _G1 as shown in FIG.

The check valve 9 has a structure that allows fuel to be supplied to the second fuel gear G ₂ and prevents the fuel from flowing out, and is made up of a valve body 26 and a spring 28 . It is pressed and biased to the left in the figure.

The distributor type fuel feed pump 10 is a pump that adjusts the amount of fuel and discharges a specified amount of fuel. For example, a pump called a VE type is used.
The distributor type fuel feed pump 10 is connected to a second fuel gearbox _G2 by a second fuel pipe _P2 .

Further, the fuel feed pump 11 is connected to the first fuel gear gallery _G1 by a first fuel pipe _P1 , and to the distribution type fuel feed pump ₁₀ by a third fuel pipe P3.

Function The present invention is constructed as described above, and its function will be explained below. First, the fuel suction stroke (metering) will be explained. In this fuel suction stroke, the electromagnetic solenoid 18 of the electromagnetic valve 5 is deenergized, so that the valve body 20 is separated from the valve seat 21 and the fuel passage 13 is removed. The fuel feed pump 11 is in operation and low-pressure fuel is supplied to the first fuel gear _{G 1 and} the distribution type fuel feed pump 10. Then, the cam 16 rotates in the direction of arrow A to move from the maximum lift portion 16a to the minimum lift portion 1.
The contact point gradually changes toward 6b, and the cam 16 sequentially contacts the flange portion 3a of the pressure-feeding plunger 3.
is in a state where the lift is decreasing, and the pressure-feeding plunger 3 is being raised by the pressing force of the spring 14. The first fuel gear G ₁ includes a fuel feed pump 1.
1 through the first fuel pipe _P1 as shown by arrow B, but the first fuel gear
G ₁ and the plunger chamber 13 above the pumping plunger
When it is filled, no more fuel can flow in. Also, in this fuel intake stroke, the distribution type fuel feed pump 10 measures the fuel supplied from the fuel feed pump 11 as shown by arrow C, and transfers only the prescribed fuel necessary for one fuel injection to the second fuel pipe. The valve body ₂ is applied to the second fuel gear G ₂ via P 2 against the spring 28 of the check valve 9.
Open 6 and send it in. The fuel then flows into the plunger chamber 13, pushes up the injection plunger 4, and
The distribution type fuel feed pump 10 stops its operation at the stage when a specified amount of fuel is supplied. Therefore, only a fixed amount of fuel is always supplied to the plunger chamber 13 during the intake stroke. In this case, the upper end 4a of the injection plunger 4 rises beyond the third spill port S3 and the upper end 4a of the injection plunger ₄ rises beyond the third spill port S3.
It is stopped below spill port _S2 . Furthermore, as the operation of the distribution type fuel feed pump 10 is stopped, the pressure inside the second fuel pipe _P2 decreases, so the valve body 26 of the check valve 9 is pressed leftward in the figure by the spring 28, and the plunger The fuel in the chamber 13 is prevented from flowing out.

Next, the fuel injection stroke will be explained. cam 16
rotates in the direction of arrow A and is in the state shown in FIG. As the contact point moves, the flange portion is pushed downward, the spring 14 is compressed, and the pumping plunger 3 begins to descend. See also Figure 2 for cam 16.
The rotation of the engine progresses as the crank angle of the engine increases, and in FIG. , C is a diagram showing the fuel injection pressure with respect to the crank angle, and D is a diagram showing the cam lift of the cam ₁₆ with respect to the crank angle. At this stage, the electromagnetic solenoid 18 of the electromagnetic valve 5 is deenergized, so the valve body 20 is open, and as a result, the second
The spill port S ₂ is in an open state, but since the cross-sectional area of the second spill port S ₂ is narrowed considerably, the pressure inside the plunger chamber 13 gradually increases as the pressure-feeding plunger 3 descends. Go. This state is the journey from point P to point Q in FIG.

Then, at the position of point Q, a current is sent from the electronic circuit to the electromagnetic solenoid 18 of the electromagnetic valve 5, energizing it, and the valve body 20 is attracted and comes into close contact with the valve seat 21, closing the second spill port _S2 . When this occurs, the fuel in the plunger chamber 13 has no escape, so the pressure rises rapidly as the pressure-feeding plunger 3 descends, and as a result, the injection plunger 4 starts descending, causing the lower plunger pressed by the injection plunger 4 to High-pressure fuel in the chamber 13 is injected from the fuel injection passage 8 through the fuel injection port 23a of the nozzle 23 into the combustion chamber of the engine. In this case, needle 2
4 is maintained in a floating state by pressing a spring 30 with high-pressure fuel. This state is the second
This is the stroke from point Q to point R in B and C of the figure, and fuel injection ends at point Q. That is, the upper end 4a of the injection plunger 4 is lowered and the third
It moves below the spill port _S3 , and the third spill port _S3 is opened. As a result, the high-pressure fuel present in the plunger chamber 13 below the pressure-feeding plunger 3 flows into the needle chamber 25 through the fuel passage 6, and at this time the pressure in the fuel injection passage 8 has already dropped rapidly. , combined with the pressing force of the spring 30, the head 24a of the needle 24 is pushed into the fuel passage 6.
The tip 24b of the needle 24 is pushed downward by the high pressure fuel that has flowed in through the fuel injection port 2.
3a is instantly occluded. Therefore, the fuel does not leak out after the injection ends, and the fuel injection is cut off very well.

In this way, the injection rate decreases as shown in point T in Figure 2, and the injection pressure decreases as shown in point U in Figure 2. When the injection is completed, the energization to the solenoid valve 5 is stopped after a while, and the valve The body 20 is opened as shown at point V in A to again communicate the fuel passage 13 with the first fuel gear _G1 ,
The cam 16 rotates from its maximum lift portion 16a to its minimum lift portion 16b, and the pressure-feeding plunger 3
begins to rise. Then, the fuel suction stroke is performed again in the same manner as described above, and a specified amount of fuel is supplied from the distribution type fuel feed pump 10 into the plunger chamber 13. Thereafter, the suction stroke and fuel injection stroke are repeated in the same manner.

Effects Since the present invention is configured and operates as described above, in a unit injector equipped with a solenoid valve for fuel injection timing control, the second fuel gear is connected to the lower side of the injection plunger. provided independently from the first fuel gear on the upper side of the
A check valve is installed in the second fuel gear, and fuel is supplied by a distribution type fuel feed pump that has the function of metering and supplying fuel, so that the amount of fuel injected for each injection or for each cylinder is reduced. This has the effect of making it constant, and as a result, it also has the effect of preventing uneven rotation of the engine. Additionally, a fuel passage is provided so that when the injection plunger reaches the bottom dead center, the high-pressure fuel compressed by the pressure-feeding plunger acts on the needle head of the nozzle, strongly pressing the needle against the injection port of the nozzle. Therefore, there is an effect that the fuel runs out well at the end of injection.

[Brief explanation of the drawing]

The drawings relate to an embodiment of the present invention, and Fig. 1 is a longitudinal cross-sectional view of a unit injector, and Fig. 2 shows changes in the opening/closing state of the solenoid valve, fuel injection rate, fuel injection pressure, and cam lift with respect to the engine crank angle. 3 is a diagram showing the states of FIG. 1 is a unit injector, 2 is an injector body, 3 is a pressure feeding plunger, 4 is an injection plunger, 5 is a solenoid valve, 6 is a fuel passage, 8 is a fuel injection passage, 9 is a check valve, 10 is a distribution type fuel feed pump, 11 is a fuel feed pump, 14 is a spring, 2
4 is the needle, 24a is the head, 25 is the needle chamber, G ₁ is the first fuel gear, G ₂ is the second fuel gear, S ₁ is the first spill port, S ₂ is the second spill port, S ₃ is the second spill port. 3 spill ports.

Claims (1)

[Scope of utility model registration request] an injector body; a first body formed in the injector body and connected to the fuel feed pump;
a fuel gear; a pressure-feeding plunger that is biased in one direction by a spring and is slidably housed within the injector body; an injection plunger that is also slidably housed within the injector body; a first spill port that is opened when the pressure-feeding plunger is at the top dead center and communicates with the first fuel gear; and a first spill port that is opened near the bottom dead center of the pressure-feeding plunger. a second spill port whose opening and closing are controlled by the solenoid valve; a third spill port that is opened near the bottom dead center of the injection plunger and communicates with the first fuel gear; and a third spill port that is connected to the nozzle. a fuel passage that communicates with a needle chamber in which the head of the attached needle is accommodated; a fuel injection passage that opens near the bottom dead center of the injection plunger and communicates with the nozzle; and a fuel injection passage that opens near the bottom dead center of the injection plunger and communicates with the nozzle a second fuel gear gallery communicating with the vicinity; a check valve having a structure that allows fuel to be supplied to the second fuel gear gallery and prevents the fuel from flowing out;
A unit injector comprising: a distribution type fuel feed pump for metering fuel and discharging a specified amount of fuel; and the distribution type fuel feed pump is connected to the second fuel gear gallery.