JPH05296120A - Electromagnetic unit injector - Google Patents

Abstract

PURPOSE:To make the value of rush current at the time of the second injection a level not more than the maximum value of rush current at the first injection by driving rush voltage pulses with different widths first and second time in the case of reciprocating a solenoid valve two times and injecting two times at the time of one stroke. CONSTITUTION:An end of a fuel path 3b to/from a plunger chamber 3a is opened at a specified distance downward from an annular conical seat 3h in a poppet valve guide hole 3f. Flow of fuel between a drain oil reservoir 3c and a path 3b are controlled by a solenoid valve (poppet valve) 2. A solenoid control device 31 is provided to drive first and second rush voltage pulses with different widths in relation to a solenoid coil driving voltage in the case of reciprocating the poppet valve 2 two times and injecting two times at the time of one stroke. Therefore, the maximum value of a rush current at the times of second injection is less than the maximum value of a rush current at the time of the first injection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unit injector which is a fuel injection device for a diesel engine, and more particularly to an electromagnetic unit injector having a solenoid-controlled poppet valve.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIGS.
FIG. 4 is a sectional view of an example of an electromagnetic unit injector as shown in Japanese Patent Application No. 01-054602. Figure 5
7 is a main configuration diagram of the electromagnetic unit injector shown in FIG. 4, and FIGS. 2 to 3 are diagrams showing the operation of the electromagnetic unit injector shown in FIG. The unit injector is provided in each cylinder and operates a plunger driven by a cam driven by an engine to increase fuel pressure and open a needle valve of an injection nozzle to inject fuel into a combustion chamber of the engine. FIG. 5 shows the state in which the plunger 1 is descending, and when the poppet valve 2 is closed, the fuel filled in the plunger chamber 3a is pressurized and passes through the fuel passage 4a of the spacer 4 to cause the needle valve 10 of the injection nozzle 11 to move. The valve is opened and fuel injection begins. As shown in FIG. 6, the poppet valve 2
When is opened, the fuel in the plunger chamber 3a pressurized by the plunger 1 is pushed out to the passage 3b, and the fuel injection is completed. Further, as shown in FIG. 7, when the plunger 1 turns from descending to ascending, the fuel pressurized to the supply pressure (usually 1 to 6 kgf / cm ² ) flows into the plunger chamber 3a through the passage 3b and is filled therewith. One cycle of injection is completed.

Details of these operations will be described with reference to FIGS. 3 and 4, focusing on the solenoid valve. As shown in FIG. 3A, when the solenoid coil 12c is energized at time t ₁ , magnetic flux is generated in the solenoid magnetic circuit, and the solenoid stator 1
An electromagnetic attractive force F _C is generated between the armature 13 and the armature 13, but the combined force of the armature 13 and the poppet valve 2 does not move upward unless the electromagnetic attractive force F _C becomes larger than the set load of the poppet valve spring 15. Poppet valve 2 is increased at time t ₃ the valve opening of the poppet valve 2 is closed so that the time t ₂ when the electromagnetic attraction force F _C is greater than the set load of the spring 15 shown in FIG. 3 (c) ..

After that, the driving voltage of the solenoid coil 12c is lowered to the voltage V ₂ necessary for keeping the poppet valve 2 closed as shown in FIG. 3 (a). The injection pressure is shown in Figure 3.
As shown in (d), the needle valve 10 opens and fuel injection is started into the engine combustion chamber at time t ₅ when the poppet valve 2 starts rising immediately before closing and becomes higher than the opening pressure of the needle valve 10 of the injection nozzle 11. It When the time t ₆ is energized to the solenoid coil 12c is stopped, the solenoid stator 12 flux that occurred in the solenoid magnetic circuit disappears
The electromagnetic attractive force F _C working between the armature 13 and the armature 13 disappears. Therefore, the spring 15 causes the poppet valve 2 to
Is lowered and the valve opening is opened. Poppet valve 2
When begins to open, the rise of injection pressure stops and begins to fall. When the injection pressure further decreases and becomes lower than the closing pressure of the needle valve 10, the needle valve 10 is closed and the fuel injection into the engine combustion chamber ends.

The operation of reciprocating the electromagnetic valve twice during one stroke and injecting twice (so-called pilot injection) by the electromagnetic unit injector will be described with reference to FIG. As is well known, the normal single injection has a delay in ignition, and even if fuel is injected, it does not ignite immediately. Therefore, at the time of ignition in the combustion chamber, the fuel injected until then begins to burn at one time. As a result, the cylinder pressure suddenly rises, causing noise and vibration, and the combustion gas becomes hot, resulting in a large amount of nitrogen oxides. In the case of double injection, a small amount of fuel that becomes the ignition source (fire type) is first pre-injected, and if a large amount of fuel is injected aiming at the time when this begins to burn, a large amount of fuel will begin to burn immediately after injection and the cylinder pressure will rise rapidly. There is an advantage that it does not occur and a large amount of nitrogen oxide is not generated. As shown in FIG. 2A, time t ₁
Magnetic flux is generated in the solenoid magnetic circuit is energized to the solenoid coil 12c, the set load of the solenoid stator 12 and has an electromagnetic attraction force F _C is generated the electromagnetic attraction force F _C is the poppet valve spring 15 between the armature 13 Unless it becomes larger, the combination of the armature 13 and the poppet valve 2 does not move upward. Electromagnetic attraction force F at time t _{2
When C} becomes larger than the set load of spring 15, Fig. 2
As shown in (c), the poppet valve 2 rises, and at time t ₃ , the opening of the poppet valve 2 is closed. After that, the voltage applied to the solenoid coil 12c is lowered to the voltage V ₂ required to keep the poppet valve 2 closed as shown in FIG. 2 (a).

As shown in FIG. 2 (d), the injection pressure starts to rise immediately before the poppet valve 2 is closed and becomes higher than the closing pressure of the needle valve 10 of the injection nozzle 11, and the needle valve 10 is opened at time t ₄ to cause engine combustion. Preliminary injection into the chamber begins. Further, immediately after the de-energization, the solenoid coil 12c is energized again with the voltage V ₁ at time t ₇ . At this time, FIG. 2 (c)
As shown in Fig. 4, the poppet valve 2 is energized while it is moving downward, so that the time T ₂ until the poppet valve 2 rises again and the valve opening is closed again at time t ₈ is T ₁ (between times t ₁ and t ₃ . Time) becomes shorter. After the poppet valve 2 is closed, the injection pressure starts rising again as shown in FIG. 2 (d), the needle valve 10 is opened, and the main fuel injection is started. Increased similarly injection pressure and current supply is stopped the at time t ₁₀ is the needle valve 10 turned to descend stopped fuel main injection to closed engine combustion chamber is terminated.

[0007]

The above-mentioned conventional electromagnetic type unit injector has the following drawbacks in the case of double injection, which will be explained with reference to FIG. Normally, the solenoid drive voltage is program-controlled by the controller, and the first and second inrush voltage pulse widths are the same for the purpose of program simplification. However, as shown in FIG. 2B, the maximum value of the solenoid inrush current is A ₂ at the time of the second injection and A at the time of the first injection.
It is much larger than ₁ . The reason for this will be described. Since the gap between the solenoid stator 12 and the armature 13 is the maximum between the times t ₁ and t ₂ , the rise of the solenoid drive current is gentle, but the times t ₂ and t
_{Between 3} , armature 13 is solenoid stator 1
Since it is attracted by 2, the gap between the two changes and the inductance also changes, causing the solenoid drive current to rise rapidly. Also, the inductance between time t ₇ and time t ₈ is t
The inductance is approximately equal to between ₂ and t ₃ , and the rise of the solenoid drive current is steep.

Further, even after the poppet valve 2 closes the valve opening, the solenoid drive current continues to rise with almost the same gradient. Regarding the time required from the start of energization to the closing of the poppet valve 2, the required time T ₂ at the second injection is shorter than the required time T ₁ at the first injection. For the above reason, the maximum inrush current value A ₂ during the second injection is much larger than the maximum inrush current A ₁ during the first injection. Therefore, in the case of the double injection, there are serious problems such as the heat generation of the solenoid coil 12c and the large capacity of the solenoid driving power transistor, as compared with the single injection. An object of the present invention is to provide an electromagnetic unit injector in which the maximum value of the inrush current at the time of the second injection is made equal to or less than the maximum value of the inrush current at the time of the first injection.

[0009]

In the electromagnetic unit injector for a diesel engine, when the solenoid valve is reciprocated twice to make two injections in one stroke, the first and second inrush voltage pulse widths with respect to the electromagnetic solenoid drive voltage It is characterized in that it is provided with a solenoid control device that drives different widths.

[0010]

Since the present invention is configured as described above, the maximum inrush current value of the second injection is smaller than the maximum inrush current value of the first injection.

[0011]

EXAMPLE An example will be described with reference to FIGS. Figure 4
Is a sectional view of the electromagnetic unit injector, and FIG. 1 is a detailed operation explanatory view of the embodiment of the electromagnetic unit injector shown in FIG. In FIG. 4, the main body housing 3 is provided with a plunger hole having an inner diameter for slidably receiving the plunger 1 and an inner cylindrical hole having a large inner diameter for slidably receiving the tappet 5. By tapping the tappet 5 from one end of the main body housing 3, the tappet 5
The plunger 1 connected thereto can be reciprocated by a drive cam or rocker arm (not shown) and a plunger return spring 6. The plunger chamber 3 is formed by the tip of the plunger 1 and the plunger hole of the main body housing 3.
a is formed. Further, a nut 7 is screwed into an extension of the lower end of the main body housing 3, and the injection nozzle combination product is fixed to the main body housing 3 by the nut 7. Fuel is supplied from a fuel tank (not shown) through a supply pump and a fuel pipe to a fuel reservoir 24 below the main body housing 3 at a relatively low pressure via a fuel supply passage in a cylinder head (not shown).

A side portion of the main body housing 3 is provided with a poppet valve guide hole 3f, a lower circular hole 3g, and an annular conical valve seat 3h. A flat shoulder portion 31 is provided below the lower circular hole 3g, and a lid 18 having a poppet valve downward movement limiting function is fixed to the flat shoulder portion 31 with a screw 20. The upper surface of the lid 18 forms a fuel reservoir 3p together with the lower circular hole 3g. The fuel sump 3p has a lower fuel sump 2 in the main body housing.
4, the fuel is supplied through the in-housing supply passage 3d, and further discharged through the drain passage 3e to a fuel tank (not shown). An oil sump 3 is provided above the annular conical valve seat 3h.
c is formed, and a communication passage 3k is opened between the fuel reservoir 3p and the drain oil reservoir 3c so that the pressure between both reservoirs is equalized. One end of a passage 3b for allowing fuel to flow in and out of the plunger chamber 3a is opened a predetermined distance below the annular conical valve seat 3h of the poppet valve guide hole 3f. Oil sump 3
The fuel flow between c and passage 3b is controlled by a solenoid operated poppet valve 2.

The poppet valve 2 is formed of a sliding portion 2b having a conical valve face 2m and a valve shaft portion 2c extending further upward. Around the sliding portion 2b, an annular groove 2 for communicating the passage 3b with the oil sump 3c when the poppet valve 2 is opened and closed.
1 is provided in the main body housing 3. The poppet valve 2 is hollow for the purpose of weight reduction, and the armature 13
A hexagonal hole 2p used for tightening is also provided. An armature 13 is fastened and fixed to an upper end surface of a valve shaft portion 2c of the poppet valve 2, and a plurality of holes 23 are formed in the armature 13 to allow fuel to pass through when the armature 13 moves. The poppet valve 2 forms a shoulder above the conical valve face 2m and engages a lower spring seat 26. A spring 15 that works in a direction to open the poppet valve 2 and an upper spring receiver 27 that fixes and limits the spring 15 are installed on the lower spring receiver 26. The solenoid stator 12 is fastened and fixed to the main body housing 3 with a bolt 22 via a solenoid spacer 14. The solenoid stator 12 is composed of, for example, a solenoid case 12d made of a synthetic resin material, a coil bobbin 12b holding a solenoid coil 12c, and an E-shaped core 12a forming a magnetic circuit. A rectangular armature 13 is installed between the solenoid coil 12c and the main body housing 3. FIG. 4 shows the closed state of the poppet valve 2,
In this state, the solenoid stator 12 and the armature 1
The minimum clearance (0.05 mm-
0.3 mm) is present.

In the opposite state, that is, in the open state of the poppet valve 2, the lower end surface 2a of the poppet valve is in contact with the upper surface 18a of the lid. The lid 18 has a passage (hole or groove) 18c that allows the poppet valve cavity 2p and the fuel reservoir 3p to communicate with each other when the poppet valve 2 is in contact. Solenoid coil 12c
Is connected to a pair of terminals (not shown), which can be connected to the power source through the solenoid control device 31 (fuel injection electronic control circuit) by electrical wiring. Is a well-known method in which energization is controlled as a function of engine operating conditions, and as is well known, a solenoid controller 31 is connected with a detector 32 for detecting engine speed, oil temperature, supply pressure, and the like. There is.

The operation of the above embodiment will be described. To operate the engine, fuel from a fuel tank (not shown) is supplied to a fuel reservoir 24 below the main body housing 3 at a predetermined relatively low pressure through a fuel pump (not shown) and a fuel pipe (not shown). It Fuel sump 24
The fuel supplied to is supplied to the fuel reservoir 3p through the in-housing supply passage 3d, and is further drained to a fuel tank (not shown) through the drain passage 3e. In FIG. 1, time t
_{Since the} solenoid coil 12c is not energized before _{1, the} poppet valve 2 is held in the open state by the force of the spring 15. In this state, when the plunger 1 goes up, the fuel flows from the oil sump 3c through the annular groove 21 and the passage 3b into the plunger chamber 3a. As shown in FIG. 1A, when the solenoid coil 12c is energized with voltage V ₁ at time t ₁ , magnetic flux is generated in the solenoid magnetic circuit, and electromagnetic attraction force F _C is generated between the solenoid stator 12 and the armature 13. However, unless the electromagnetic attraction force F _C becomes larger than the set load of the spring 15, the combined body of the armature 13 and the poppet valve 2 does not move upward. The inrush current is required only for the time during which the armature 13 is attracted and moved from the maximum air gap position to the solenoid stator 12 side, and the holding current A is maintained after the armature 13 stops at the minimum air gap position.
₀ is sufficient.

The reason for this will be described. Since it is desired to close the poppet valve 2 at a high speed in order to obtain good injection controllability, it is necessary to flow an exciting current so that the attraction force with the full capacity of the electromagnet is exerted. The electromagnetic attraction force F _C and the exciting current I have the following relationship. F _C = 1 / 2μ (Bg ² S), Bg = μ ・ (NI) /
δ, μ = 4π × 10 ⁻⁷ N: number of coil turns, Bg: magnetic flux density of void (saturation value exists) δ: void length, S: void cross-sectional area. For this reason, Bg must be raised to the saturation value in order to exert the attraction force that is the full capacity of the electromagnet. Since I / δ is constant when Bg becomes saturated, I may be small if δ is small. That is, the inrush current may be flowed for the time during which the armature 13 is attracted and moved from the maximum air gap position toward the solenoid stator 12, and the holding current A ₀ may be applied after the armature 13 stops at the minimum air gap position.

At time t ₂ , the electromagnetic attractive force F _C is applied to the spring 1
When the load becomes larger than the set load of 5, the poppet valve 2 rises and the conical valve face 2m of the poppet valve 2 is seated on the annular conical valve seat 3h at time t ₃ , as shown in FIG. 1 (c). Immediately after this, the drive voltage required by the solenoid coil 12c is sufficient to maintain the closed state of the poppet valve 2, so that it can be reduced from V ₁ to V ₂ . During this time, since the tappet 5 is pushed and the plunger 1 starts to move, the injection pressure of the fuel begins to rise immediately before the poppet valve 2 is closed as shown in FIG. 1D, and the injection nozzle needle valve 10
From time t ₄ when larger than the valve opening pressure needle valve 10 as shown in FIG. 1 (e) fuel injection starts to open the engine combustion chamber. When the energization of the solenoid coil 12c is stopped at time t ₅ , the electromagnetic attraction force F _C between the solenoid stator 12 and the armature 13 disappears. Therefore, the poppet valve 2 is lowered and the valve opening is opened. When the poppet valve 2 starts to open, the increase of the injection pressure stops and starts to fall.
The needle valve 10 begins to close at a time when the injection pressure further decreases and becomes smaller than the closing pressure of the needle valve 10, and at time t ₆ , the fuel preliminary injection (pilot injection) into the engine combustion chamber ends.

Further, immediately after the de-energization at time t _5, the solenoid coil 12c is energized again at time t ₇ . At this time, as shown in FIG. 1C, the poppet valve 2 is energized during the downward movement, so that the time T ₂ until the poppet valve 2 rises again and the valve opening portion is closed again is times t ₁ and t _3. Is less than the time T ₁ between. Therefore, the second inrush current A
₂ is smaller than the first inrush current A ₁ . When the poppet valve opening time t ₈ is closed again, V ₂ from the voltage V ₁ because the driving voltage solenoid stator 12 is required immediately after may only hold the closed state of the poppet valve 2
Be reduced to. After closing the poppet valve 2 Fig. 1 (d)
As shown in FIG. 5, the injection pressure starts to rise again and the needle valve 10 opens to start the main fuel injection. Increase in the same manner as described above injection pressure and energization of the solenoid coil 12c is released at time t ₁₀ the fuel main injection into the engine combustion chamber is closed, the needle valve 10 turns to a blind descent ends.

[0019]

Since the present invention operates as described above, it has the following effects. As shown in FIG. 1, the energization time of the second injection (between times t ₇ and t ₈ ) T ₂ is shorter than the energization time of the first injection (between times t ₁ and t ₅ ) T ₁ , so the second inrush current is maximum. The value A ₂ becomes smaller than the maximum value A _{1 of the} first inrush current. For this reason, serious problems such as heat generation of the solenoid coil and a large power transistor for driving the solenoid coil are avoided. Therefore, the present invention can provide an electromagnetic unit injector in which the maximum inrush current value during the second injection is set to be equal to or less than the maximum inrush current value during the first injection.

[Brief description of drawings]

FIG. 1 is a detailed operation explanatory diagram of an electromagnetic unit injector according to an embodiment.

FIG. 2 is a detailed operation explanatory diagram of a conventional electromagnetic unit injector.

FIG. 3 is a detailed operation explanatory view of a conventional electromagnetic unit injector.

FIG. 4 is a sectional view of an electromagnetic unit injector.

5 is a configuration diagram of main parts of the electromagnetic unit injector shown in FIG.

6 is a configuration diagram of main parts of the electromagnetic unit injector shown in FIG.

7 is a configuration diagram of main parts of the electromagnetic unit injector shown in FIG.

[Explanation of symbols]

2 ... Poppet valve, 12 ... Solenoid stator, 12c ...
Solenoid coil, 13 ... Armature, 31 ... Solenoid control device.

Claims (1)

[Claims] 1. An electromagnetic unit injector for a diesel engine, wherein when the solenoid valve (2) reciprocates twice during one stroke to inject twice, with respect to the electromagnetic solenoid coil drive voltage, the first and second inrush Solenoid control device that drives voltage pulse widths with different widths (3
An electromagnetic type unit injector characterized by comprising 1).