JP3021182B2 - Electromagnetic unit injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIGS.
FIG. 4 is a cross-sectional view of an example of an electromagnetic unit injector as shown in Japanese Utility Model Application No. 01-054602. Figure 5
7 is a main configuration diagram of the electromagnetic unit injector shown in FIG. 4, and FIGS. 2 and 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 by a cam driven by the engine to increase fuel pressure to open a needle valve of an injection nozzle to inject fuel into a combustion chamber of the engine. FIG. 5 shows a state in which the plunger 1 is lowered, 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 so that the needle valve 10 of the injection nozzle 11 is moved. The valve is opened and fuel injection starts. As shown in FIG.
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 ends. Further, as shown in FIG. 7, when the plunger 1 changes from descending to ascending, the fuel pressurized to the supply pressure (normally 1 to 6 kgf / cm ² ) flows into the plunger chamber 3a via the passage 3b and is filled. One cycle of the injection is completed.

The details of these operations will be described with reference to FIGS. Figure 3 when the solenoid coil 12c is energized at time t ₁ as shown in (a) magnetic flux is generated in the solenoid magnetic circuit solenoid stator 1
An electromagnetic attraction force F _C is generated between the armature 2 and the armature 13, but unless the electromagnetic attraction force F _C becomes larger than the set load of the poppet valve spring 15, the combined body of the armature 13 and the poppet valve 2 does not move upward. 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) .

[0004] The drive voltage of the subsequent solenoid coil 12c is lowered to a voltage V ₂ necessary to close hold poppet valve 2 as shown in FIG. 3 (a). Fig. 3
The time t ₅ becomes larger than the valve opening pressure of the needle valve 10 of the injection nozzle 11 started to rise from just before the poppet valve 2 closes, as shown in (d) of the fuel injection is started into the engine combustion chamber opens the needle valve 10 You. 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 attraction F _C that has been acting between the armature 13 and the armature 13 disappears. For this reason, the poppet valve 2 is
Is lowered and the valve opening is opened. Poppet valve 2
When starts to open, the increase of the injection pressure stops and starts to decrease. When the injection pressure further decreases and becomes smaller than the valve 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 solenoid valve twice during one stroke by the electromagnetic unit injector and injecting twice (so-called pilot injection) will be described with reference to FIG. As is well known, there is a delay in ignition in normal single injection, and the fuel is not immediately ignited even if the fuel is injected. Therefore, when the fuel is ignited in the combustion chamber, the injected fuel starts burning at once. For this reason, there has been a problem that the in-cylinder pressure suddenly rises, causing noise and vibration, or the combustion gas becomes high in temperature and a large amount of nitrogen oxides are generated. In the case of double injection, a small amount of fuel, which is the ignition source (fire type), is injected first, and if a large amount of fuel is injected in order to start burning, a large amount of fuel starts burning immediately after the injection, so the in-cylinder pressure rises sharply There is a merit that no large amount of nitrogen oxide is generated. Figure 2 time t ₁ as shown in (a)
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. At time t ₂ , the electromagnetic attraction force F
_{When C} becomes larger than the set load of the spring 15, FIG.
Poppet valve 2 as shown in (c) is raised, the opening of the poppet valve 2 at time t ₃ is closed. Applied voltage then the solenoid coil 12c is reduced to a voltage V ₂ necessary to close hold poppet valve 2 as shown in FIG. 2 (a).

[0006] injection pressure engine combustion opens the needle valve 10 to the time t ₄ when larger than the valve closing pressure of the needle valve 10 of the injection nozzle 11 started to rise from just before the poppet valve 2 closes, as shown in FIG. 2 (d) Pre-injection into the chamber begins. Further energized by voltages V ₁ again solenoid coil 12c to the energization cancellation after rapidly time t _7. At this time, FIG.
As shown in the figure, the time T ₂ from when the poppet valve 2 rises again and the valve opening is closed again at the time t ₈ is T ₁ (between the times t ₁ and t ₃ ). Time). After the poppet valve 2 is closed, the injection pressure starts increasing again as shown in FIG. 2D, 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 conventional electromagnetic unit injector has the following drawbacks during the double injection, which will be described with reference to FIG. Normally, the solenoid drive voltage is program-controlled by a 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 ₂ 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 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 _{2
Between 3} , armature 13 is connected to solenoid stator 1
2, the air gap between them changes, so the inductance also changes, and the rise of the solenoid drive current becomes steep. The inductance between the time t ₇ and t ₈ at time t
Inductance and a substantially equal rise of the solenoid drive current between ₂ and t ₃ is steep.

Further, even after the poppet valve 2 closes the valve opening, the solenoid drive current continues to rise at almost the same gradient. Regarding the time required from the start of energization to the closing of the poppet valve 2, the required time T2 for the _second injection is shorter than the required time T1 for the _first injection. Rush current maximum value A ₂ at the time of the second injection greatly becomes larger than the inrush maximum current A ₁ during the first injection for the reasons. Therefore, the double injection has serious problems such as the heat generation of the solenoid coil 12c and the large capacity of the power transistor for driving the solenoid 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 rush current at the time of the second injection is set to be equal to or less than the maximum value of the rush current at the time of the first injection.

[0009]

According to the electromagnetic unit injector of the present invention, by applying a voltage to the solenoid and closing the electromagnetic valve, the pressure of the fuel is increased and the injection is started.
An electromagnetic unit injector for a diesel engine having a function of shutting off a voltage applied to the solenoid and opening an electromagnetic valve to decrease the fuel pressure and terminate the injection, wherein a voltage is applied to the solenoid during one stroke. In the electromagnetic unit injector that performs pilot injection by injecting fuel twice by reciprocating the electromagnetic valve 2 twice by inducing and shutting off the application, the opening and closing operation of the electromagnetic valve that constitutes the injector is induced.
The excitation voltage of the control solenoids, T ₁ 1 st injection and inrush voltages V ₁ and second injection the same level of voltage, and the pulse width of the projecting input voltages, _{respectively,} T ₂
And a solenoid controller 31 for exciting the solenoid so that T ₁ > T ₂ .

Since the present invention is configured as described above, the first inrush voltage V
_1, while the pulse width of the energization is T _1, by a second inrush voltage is smaller than the T ₁ the voltage at and energizing pulse width T ₂ of the same level as the voltage V _1, 2 times th inrush current a ₂ can be the same level as the inrush voltage first becomes smaller than the first inrush current a _1. As a result, it is possible to prevent the solenoid coil from generating heat due to the second excessive rush current as in the related art, and it is possible to reduce the capacity of the power transistor for driving the solenoid.

[0011]

An embodiment will be described with reference to FIGS. FIG.
FIG. 1 is a sectional view of an 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 cylinder hole having a large inner diameter for slidably receiving the tappet 5. The tappet 5 projects from one end of the main body housing 3 so that the tappet 5
The plunger 1 connected thereto can be reciprocated by a drive cam or rocker arm (not shown) and the plunger returning 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 at the lower end of the main body housing 3, and the jet nozzle combination product is fixed to the main body housing 3 by the nut 7. Fuel is supplied at a relatively low pressure from a fuel tank (not shown) through a supply pump and a fuel pipe to a fuel reservoir 24 at a lower portion of the main body housing 3 through a fuel supply passage in a cylinder head (not shown).

The side of the main 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 the lid 18 having a poppet valve downward movement restriction 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 reservoir 3p has a fuel reservoir 2 at the lower part of the main housing.
The fuel is supplied from 4 to the housing supply passage 3d and further discharged to a fuel tank (not shown) via the drain passage 3e. An oil sump 3 is provided above the annular conical valve seat 3h.
The communication passage 3k is provided between the fuel reservoir 3p and the oil drain reservoir 3c so that the pressure between the reservoirs is equalized. One end of the passage 3b through which fuel enters and exits 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 includes a sliding portion 2b having a conical valve face 2m and a valve shaft portion 2c extending further upward. An annular groove 2 surrounding the sliding portion 2b communicates the passage 3b and the oil sump 3c when the poppet valve 2 opens and closes.
1 is provided in the main body housing 3. The poppet valve 2 is hollow for the purpose of weight reduction.
A hexagonal hole 2p used for tightening is also provided. An armature 13 is fastened and fixed to the upper end surface of the valve stem 2c of the poppet valve 2, and a plurality of holes 23 are formed in the armature 13 to allow the passage of fuel when the armature 13 moves. The poppet valve 2 forms a shoulder above the conical valve face 2m and engages a lower spring receiver 26. A spring 15 acting in a direction to open the poppet valve 2 and an upper spring receiver 27 for fixing and restricting the spring 15 are provided on the lower spring receiver 26. The solenoid stator 12 is fixedly fastened to the main housing 3 by bolts 22 via a solenoid spacer 14. The solenoid stator 12 includes, 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 provided 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
3 has a minimum clearance (0.05 mm to
0.3 mm).

In the opposite state, that is, when the poppet valve 2 is open, 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 to communicate with the fuel reservoir 3p 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 a power supply via an electric wiring via a solenoid control device 31 (electronic fuel injection control circuit). The energization is controlled as a function of the operating conditions of the engine, which is a known method. A solenoid control device 31 is connected to a detector 32 for detecting the engine speed, oil temperature, supply pressure, etc., as is well known. I have.

The operation of the above embodiment will be described. During operation of the engine, fuel from a fuel tank (not shown) is supplied at a predetermined relatively low pressure from a fuel supply passage in a cylinder head (not shown) to a fuel reservoir 24 below the main body housing 3 through a fuel pump and a fuel pipe (not shown). You. Fuel reservoir 24
The fuel supplied to the fuel tank is supplied to a fuel reservoir 3p through a supply passage 3d in the housing, and further drained to a fuel tank (not shown) through a drain passage 3e. In FIG. 1, time t
Before ₁ , the solenoid coil 12 c is not energized, so that the poppet valve 2 is held open by the force of the spring 15. In this state, when the plunger 1 goes up the stroke, the fuel flows from the oil sump 3c through the annular groove 21 and the passage 3b into the plunger chamber 3a. Electromagnetic attracting force F _C between is energized by voltages V ₁ to the solenoid coil 12c solenoid magnetic flux is generated in the magnetic circuit solenoid stator 12 and the armature 13 is generated at time t ₁ as shown in FIG. 1 (a) There conjugate the electromagnetic attracting force F _C is not greater than the set load of the spring 15 the armature 13 and poppet valve 2 is not Ugokidasa upward. The inrush current is required only during the time when the armature 13 is being attracted and moved from the maximum gap position to the solenoid stator 12 side, and the holding current A is required after the armature 13 stops at the minimum gap position.
₀ is sufficient.

The reason will be described. Since the poppet valve 2 is desired to be closed at a high speed in order to obtain good injection controllability, it is necessary to supply an exciting current so as to use the attraction force of the full power of the electromagnet. Electromagnetic attracting force F _C and the exciting current I is the following relationship. F _C = １ ／ μ (Bg ² S), Bg = μ · (NI) /
δ, μ = 4π × 10 ⁻⁷ N: number of coil turns, Bg: magnetic flux density of air gap (saturation value exists) δ: air gap length, S: air gap cross-sectional area. For this reason, Bg must be increased to a saturation value in order to use the attraction force of the full capacity of the electromagnet. When Bg becomes saturated, I / δ is constant, so if δ is small, I may be small. That may be allowed to flow only time rush current that is moving is sucked from the maximum gap position to the solenoid stator 12 side, will shut down the armature 13 is at a minimum air gap position may be maintained current A _0.

[0017] The electromagnetic attractive force at the time t ₂ F _C is spring 1
Poppet valve 2 so becomes larger than the set load shown in FIG. 1 (c) of the 5 elevated cone type valve face 2m of the poppet valve 2 at time t ₃ is seated on the annular conical valve seat 3h. Driving voltage solenoid coil 12c Immediately after this is need is caused to decrease from V ₁ since it is sufficient only to hold the closed state of the poppet valve 2 to V _2. During this time, the tappet 5 is pushed and the plunger 1 starts to move, so that the fuel injection pressure starts to rise immediately before the poppet valve 2 closes as shown in FIG.
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 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. For this reason, the poppet valve 2 is lowered and the valve opening is opened. When the poppet valve 2 starts to open, the increase in the injection pressure stops and starts to decrease.
Fuel preinjection of the needle valve 10 in the smaller becomes time from the valve closing pressure of the injection pressure is further lowered needle valve 10 to the engine combustion chamber and the beginning time t ₆ closed (pilot injection) is terminated.

Furthermore the time _t again solenoid coil 12c to the energization cancellation after rapidly time _{t 7} of ₅ is energized by the first voltage _{V 1} of the same level. At this time, FIG.
Because the poppet valve 2 as shown in (c) is energized during the downward movement, the time T ₂ of the up poppet valve 2 is increased valve closing opening again again time t ₁ and t time between ₃ shorter than T _1. Thus also the second voltage is a V ₁ of the first and the same level, second rush current A ₂
It is smaller than the first inrush current _{A 1.} Time t ₈
When the poppet valve opening is closed again, the voltage since the driving voltage solenoid stator 12 is required immediately after may only hold the closed state of the poppet valve 2 is V ₁
It is caused to decrease to _{V 2} from. After the poppet valve 2 is closed, the injection pressure starts increasing again as shown in FIG. 1D, the needle valve 10 is opened, and the main fuel injection is started. 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]

The present invention operates as described above and has the following effects. In the second (between times t ₇ and t ₈₎ energizing time of injection T ₂ are inrush voltage V ₁ and the voltage of the same level for the first time injection as shown in FIG. 1, the energization time of the first injection (time t ₁ and shorter than t between _{3) T 1,} 2 time inrush current maximum value _{a 2} is smaller than the first rush current maximum value _{a 1.} For this reason, serious problems such as the problem of heat generation of the solenoid coil and the need for a large capacity 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 at the time of the second injection is equal to or less than the maximum value of the inrush current at the time of the first injection.

[Brief description of the drawings]

FIG. 1 is a detailed operation explanatory view of an electromagnetic unit injector of an embodiment.

FIG. 2 is a detailed operation explanatory view 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.

FIG. 5 is a main part configuration diagram of an electromagnetic unit injector shown in FIG. 4;

FIG. 6 is a configuration diagram of a main part of the electromagnetic unit injector shown in FIG. 4;

FIG. 7 is a configuration diagram of a main part of the electromagnetic unit injector shown in FIG. 4;

[Explanation of symbols]

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

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 45/04 F02D 41/20 F02D 41/40 F02M 57/02 F02D 41/34

Claims (1)

(57) [Claims] 1. A solenoid valve is closed by applying a voltage to a solenoid.
As a result, the fuel pressure rises and injection starts,
Shuts off the voltage applied to the solenoid and opens the solenoid valve
As a result, the fuel pressure drops and the injection ends.
Electromagnetic unit for diesel engine with functions
A voltage applied to the solenoid during one stroke
The solenoid valve (2) is set to 2
Reciprocates twice and injects fuel twice, pilot injection
Electromagnetic unit injector that performs
Induces the opening and closing operation of the solenoid valve constituting the injector
・ For the excitation voltage of the solenoid to be controlled,
Out second identical level of voltage inrush voltages V ₁ between the injection
And the pulse widths of the rush voltages are T ₁ and T ₁ , respectively.
Said solenoid as _T 1> _{T 2} becomes when the ₂
Electromagnetic having a solenoid control device (31) for exciting
Expression unit injector.