JPH09166062A - Pressure accumulation type fuel injector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve delayed response to a boosting failure or a pressure change at the time of starting and to control the deterioration of exhaust emission. SOLUTION: When fuel is sent by pressure from an intermittent pressure feeding pump 5, first and second check valves 25 and 26 are opened so as to supply the fuel to a back pressure room 20 and an incorporated type pressure accumulation room 23 and a fuel injection hole 21 is sealed by a needle valve 15. When current is carried to a solenoid 38, since a valve 35 is opened the back pressure room 20 is communicated with a drain port 33, the needle valve 15 is raised and injection is started. When the carrying of current to the solenoid 38 is stopped, since the valve 35 shuts off the back pressure room 20 and the drain port 33, high pressure fuel is supplied from the pressure accumulation room 23 through an orifice 27 to the back pressure room 20, the needle valve 15 is lowered and the injection is stopped. Since it is only necessary to supply fuel to the pressure accumulation room incorporated in each of the fuel injection valves, delayed response to a boosting failure at the time of starting or a pressure change is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure accumulation type fuel injection device applied to an internal combustion engine.

[0002]

2. Description of the Related Art Among conventional pressure-accumulation type fuel injection devices, there is a fuel injection device using a balance rod, as disclosed in, for example, Japanese Patent Laid-Open No. 5-332220. The configuration and operation of the fuel injection device will be described with reference to FIG.

The high-pressure fuel pumped from the fuel pump 150 is accumulated in the common rail 151 and further supplied to the hydraulic control valve 100 mounted on the cylinder head of the engine for each cylinder.

A well-known nozzle 102 is screwed under a holder 101 of the hydraulic control valve 100 by a retainer 103, and a needle 105 is slidable by the force of a pressure spring 107 via a spring holder 106. Larger than 105 diameter with 2-3 clearance
The fuel pressure acting on the upper end of the command piston 108 of μm urges it in the seating direction. The outer valve 111 is inserted leaving a clearance of 2 to 3 μm so that it can slide in the guide hole 110 formed in the holder 101 in the left-right direction, and is pushed to the right by the spring 112. Outer valve seat 11
Seated in 3. An inner valve 117 having an inner valve seat 116 and having a clearance of 2 to 3 μm is inserted into a left central hole 115 in the outer valve 111, and is pushed leftward by fuel pressure. A balance rod 11 having the same diameter as the inner valve seat 116 and a clearance of 2 to 3 μm is slidably mounted in the right center hole.
8 is accommodated and pushed rightward by the fuel pressure.

The high pressure port 120 has an annular high pressure groove 12.
1. The fuel port 122 in the holder 101, the fuel port 123 in the nozzle 102, and the oil sump 125 are communicated in this order up to the vicinity of the injection hole 126. The high pressure groove 121
Is the radial fuel port 1 in the outer valve 111.
27, and also communicates with the axial fuel port 128. Therefore, as shown in FIG. 4, when the outer valve 111 moves to the right and the inner valve seat 116 is separated,
It also communicates with the back pressure chamber 130 at the upper end of the command piston 108.

The spring chamber 131, which accommodates the pressure spring 107, communicates with a spring chamber 133, which accommodates the spring 112, through a port 132, and the spring chamber 133 communicates with a drain port 136, through a port 135. There is. The annular low pressure groove 137 in the outer valve 111 also communicates with the drain port 136 in the order of the radial port 138 and the annular low pressure groove 140 in the holder 101.

Next, the operation of the conventional hydraulic control valve 100 will be briefly described. The state of FIG. 4 shows a state in which the fuel injection is stopped, and when the fuel injection starts, the solenoid 141
When the power is turned on, the outer valve 111 is sucked to the left and separated from the outer valve seat 113, and at the same time, seated on the inner valve seat 116. By this, the back pressure chamber 1
Since 30 communicates with the drain port 136 and the hydraulic pressure decreases, the needle 105 is pushed upward by the pressure of the oil sump 125 communicating with the high pressure port 120 to open the injection hole 126, and the fuel is injected. Be started.

[0008]

In the conventional fuel injection device, the pressure inside the fuel injection pipe and the common rail is always high. Moreover, the common rail requires a considerably large capacity of 30 cc to 50 cc in order to keep the pressure for each cylinder constant. Therefore, when starting the engine, it takes a considerable time to boost the pressure of the common rail, so even if the pressure is changed on the pump side when the startability deteriorates or the operating conditions change, it is quite difficult to achieve the target with a large capacity common rail. The pressure cannot be reached, which causes a problem that exhaust emission is deteriorated during transient operation.

The present invention was created in view of the above-mentioned problems of the prior art, and an object of the present invention is to improve the boosting failure at the time of starting, the response delay when the pressure is changed, and the like. Therefore, it is an object of the present invention to provide a pressure-accumulation fuel injection device capable of suppressing deterioration of exhaust emission and the like.

[0010]

In order to solve the above-mentioned problems, the means described in claim 1 can be adopted. According to this means, when the pressure feed of the fuel from the intermittent pressure feed type pump is started, the first check valve is opened, and the first check valve is opened from the inlet.
The high-pressure fuel is supplied to the built-in pressure-accumulation chamber, and the high-pressure fuel is also supplied from the pressure-accumulation chamber to the back-pressure chamber via the passage provided with the orifice. Then, when the fuel pressure in the back pressure chamber and the pressure accumulating chamber becomes constant, the supply of fuel from the intermittent pressure feed pump is stopped, and the first check valve is closed. Then, the needle valve is pressed by the downward pressure of the back pressure chamber or the like, and fuel injection is not performed. Next, when the injection is started, the hydraulic control valve is controlled so as to reduce the pressure in the back pressure chamber, so that the pressure in the back pressure chamber decreases. Then, since the upward force acting on the needle valve becomes large, the needle valve lifts upward and injection is started. The hydraulic control valve is then controlled to increase the pressure in the back pressure chamber to stop the injection. Then, the high pressure fuel is supplied from the pressure accumulating chamber to the back pressure chamber through the orifice, the needle valve descends, and the fuel injection ends. Then, the intermittent pressure feed pump starts to feed the high pressure fuel again to the fuel injection device for the next cycle.

As described above, since the pump for supplying fuel does not need a special pump and a normal intermittent pressure feed pump can be used, a large price reduction can be achieved. Also, since a large capacity common rail can be eliminated, it is easy to mount on an engine.
Furthermore, instead of using a large-capacity common rail, it suffices to send fuel under pressure to the pressure accumulating chamber built in the fuel injection valve provided for each cylinder, so that boosting failure at start-up, response delay when changing pressure, etc. It is possible to improve, and it is possible to suppress deterioration of exhaust emission. Further, the back pressure chamber communicates with the pressure accumulating chamber only through the passage having the orifice, so that the structure is simple.

In order to solve the above-mentioned problems, means according to claim 2 can be adopted. According to this means, when the pressure feed of the fuel from the intermittent pressure feed pump is started, the first and second check valves are opened, and the high pressure fuel is fed from the inlet to the back pressure chamber and the built-in accumulator chamber. Supplied. And
When the fuel pressure in the back pressure chamber and the pressure accumulation chamber becomes constant, the supply of fuel from the intermittent pressure feed pump is stopped, and the first and second check valves are closed. Then, the needle valve is pressed by the downward pressure of the back pressure chamber or the like, and fuel injection is not performed. Next, when the injection is started, the hydraulic control valve is controlled so as to reduce the pressure in the back pressure chamber, so that the pressure in the back pressure chamber decreases. Then, since the upward force acting on the needle valve becomes large, the needle valve lifts upward and injection is started. Then, to stop the injection,
The hydraulic control valve is controlled to increase the pressure in the back pressure chamber. Then, the high pressure fuel is supplied from the pressure accumulating chamber to the back pressure chamber through the orifice, the needle valve descends, and the fuel injection ends. Then, the intermittent pressure feed pump starts to feed the high pressure fuel again to the fuel injection device for the next cycle.

As described above, since the pump for supplying fuel does not need a special pump and a normal intermittent pressure feed type pump can be used, a large price reduction can be achieved. Also, since a large capacity common rail can be eliminated, it is easy to mount on an engine.
Furthermore, instead of using a large-capacity common rail, it suffices to send fuel under pressure to the pressure accumulating chamber built in the fuel injection valve provided for each cylinder, so that boosting failure at start-up, response delay when changing pressure, etc. It is possible to improve, and it is possible to suppress deterioration of exhaust emission. Also, the back pressure chamber
Since not only the passage having the orifice communicates with the pressure accumulating chamber but also the passage having the second check valve also communicates with the inlet, the high pressure fuel can be more quickly supplied to the back pressure chamber.

[0014]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the structure of a pressure-accumulation fuel injection device of the present invention applied to an internal combustion engine. In the figure, a pressure-accumulation type fuel injection device 1 comprises a fuel injection valve 2 and a hydraulic control valve 3 provided above the fuel injection valve 2, for example, a two-way valve hydraulic control valve. The high-pressure fuel pumped by the intermittent pressure pump 5 is set to a desired injection pressure by the pressure adjusting means 6, and is delivered to the inlet 7 of the holder 8 of the fuel injection valve 2 mounted for each cylinder in the cylinder head of the engine. It is being introduced.

The lower hole 10 in the holder 8 of the fuel injection valve 2 has a nozzle body 12 having a nozzle 11 partially projecting downward from the holder 8 and a center provided at the upper end of the nozzle body 12. Opened distance piece 13
Are installed respectively. A needle valve 15 is vertically slidably fitted in the nozzle body 12, and the nozzle body 12, the distance piece 13, and the needle valve 15 form a nozzle portion. Needle valve 1
5, a pressure spring 17 is arranged via a spring holder 16 and a command piston 18 is slidably fitted above the pressure spring 17 with a holder 8 with a gap of 2 to 3 μm. Are arranged. Then, the needle valve 15 is pressed in the seating direction, that is, downward by the spring force of the pressure spring 17 and the high-pressure fuel pressure acting on the back pressure chamber 20 provided at the upper end of the command piston 18, and normally the nozzle 11 The fuel injection hole 21 provided in the lower part of is closed. An oil sump 22 is formed between the nozzle body 12 and the needle valve 15, and the holder 8, the distance piece 13, the nozzle body is interposed between the pressure accumulation chamber 23 and the oil sump 22 built in the holder 8. An introduction passage 24 formed through 12 is provided. Then, the high-pressure fuel set to a desired injection pressure by the pressure adjusting means 6 is introduced into the pressure accumulating chamber 23 from the inlet 7 provided in the fuel injection valve 2 through the passage in which the first check valve 25 is formed. And in addition,
The high-pressure fuel introduced into the inlet 7 while being supplied to the vicinity of the fuel injection hole 21 through the introduction passage 24 and the oil sump 22 passes through the passage in which the second check valve 26 is formed, and the back pressure chamber 20.
Is also supplied. Further, the pressure accumulating chamber 23 communicates with the back pressure chamber 20 through a passage having a first orifice 27 formed therein, and the back pressure chamber 20 has a hydraulic pressure through a passage having a second orifice 28 formed therein. Control port 30 of control valve 3
In communication with

The housing 31 of the hydraulic control valve 3 is provided with a drain port 33 which communicates with the fuel tank 32. In the housing 31 of the hydraulic control valve 3, the valve 3
5 is inserted so as to be slidably movable in the vertical direction, and is pressed downward by a spring 36 provided at the upper portion, and the valve 35 is seated at a lower seat portion 37, and normally, Control port 30 and drain port 33
And shut off. A solenoid 38 is installed above the housing 31. A balanced rod 40 is fitted in the valve 35 so as to be slidable in the vertical direction. Then, the high-pressure fuel introduced into the control port 30 is introduced into the lower chamber 42 of the rod 40 via the communication passage 41 formed in the valve 35. Therefore, the rod 40 is normally pushed upward by the high fuel pressure. The rod 4
By setting the diameter of 0 to be equal to or slightly larger than the diameter of the seat portion 37, it is possible to almost eliminate the hydraulic force acting on the valve 35 or to slightly apply it in the valve opening direction. The solenoid 38 can be downsized.

Next, the operation of the first embodiment will be described with reference to FIG. FIG. 2 is a time chart for explaining the operation of the first embodiment. In the figure, time t ₁ indicates the start of one cycle in fuel injection, and the fuel pressure from the intermittent pressure feed pump 5 (fuel pressure at the inlet 7) starts increasing as shown in FIG. When the fuel pressure increases to the opening pressure of the first and _second check valves 25 and 26 (time t ₂ ), the first and second check valves 25 and 26 open,
The supply of fuel to the back pressure chamber 20 and the pressure accumulation chamber 23 is allowed, and the fuel pressure in the back pressure chamber 20 and the pressure accumulation chamber 23 starts to increase as shown in (d) and (f) of FIG. Intermittent pressure pump 5
The fuel pumping from is stopped at time t ₃ . The back pressure chamber 20 and the pressure accumulating chamber 23 by the introduction of the fuel in the period T ₁ of the from time t ₁ to t ₃ Fuel 1000 kgf / cm ² is accumulated (see Fig. 2 (d) and (f)). This pressure is variable by the pressure adjusting means 6. Here, the diameter dg of the guide portion 43 of the needle valve 15 is 4 m.
m, the diameter ds of the seat portion 45 of the needle valve 15 is 2.25 m
m, the spring force F _P of the pressure spring 17 is 10.3k
If gf and the diameter dk of the command piston 18 are 4 mm,
The downward force F _D and the upward force F _U acting on the needle valve 15 are: F _D = π / 4 × 0.4 ² +1000 (pressure in the back pressure chamber) +
10.3 = 136.0 kg F _U = π / 4 × (0.4 ² −0.225 ² ) × 1000
(Pressure in the pressure accumulating chamber) = 85.9 kg, and the needle valve 15 is subtracted (F _D −F _U ) = 5.
It sits down with a force of 0.1 kg. Then, when the fuel pressure feeding of the intermittent pressure feeding type pump 5 is completed (time t in FIG. 2).
₃ ) Since the fuel pressure in the inlet 7 is reduced to about atmospheric pressure by the suction return valve (not shown) provided in the intermittent pressure feed pump 5, the first and second check valves 25 and 26 are closed. The state shown in FIG.

When the injection of electricity is started (time t _{4 in} FIG. 2), when the solenoid 38 is energized, the valve 35 is attracted by the solenoid 38 and lifted upward, and the seat portion 37 of the valve is separated. As a result, the control port 30 and the drain port 33 communicate with each other, and the fuel is discharged from the back pressure chamber 20, so that the pressure in the back pressure chamber 20 decreases. Here, when the pressure in the back pressure chamber 20 drops to 602 kg / cm ² (time t ₅ ), the downward force F _D ′ acting on the needle valve 15 is F _D ′ = π / 4 × 0.4 ² × 602 + 10.3 = 85.
It becomes 9 kg, the vertical force acting on the needle valve 15 is balanced, and when the pressure further decreases, the upward force increases, the needle valve 15 rises against the pressure spring 17, and the fuel injection hole 21 is opened. Then, the injection is started (Fig. 2 (e)). Then, the injection causes the pressure in the pressure accumulating chamber 23 to gradually decrease (see FIG. 2F). The pressure drop ΔP in the pressure accumulating chamber 23 here is However, β: compression rate (1 × 10 ^-4 cm ² / kg) V: volume of the accumulator ΔV: volume change (corresponding to injection amount), each of which corresponds to the maximum injection amount required by the engine used The volume of the pressure accumulating chamber 23 may be determined together. For example, if ΔP is desired to be 100 kg / cm ² or less, 10 is required for an engine with a maximum injection amount of 60 mm ^3.
0 = 0.06 ÷ 10 ⁴ × V, that is, V = 6 cc.

Next, in order to stop the injection (time t ₆ ), when the energization of the solenoid 38 is stopped, the valve 35 is pushed downward by the spring 36, seated at the seat portion 37, and connected to the control port 30. The drain port 33 is shut off. Then, the high-pressure fuel is supplied from the pressure accumulating chamber 23 to the back pressure chamber 20 through the first orifice 27, and when the upward force acting on the needle valve 15 is F _U ′ and the downward force is F _D ″, _{F U '= π / 4 ×} (0.4 2 -0.225 2) × ( the pressure in the _{accumulator) F D "= π / 4} × 0.4 2 × ( pressure in the back pressure chamber) +10.
3, and when the downward force F _D ″ exceeds the upward force F _U ′, the needle valve 15 begins to descend, the seat portion 45 is seated, and the fuel injection from the fuel injection hole 21 ends (time). t _7). next, at time t _8, the intermittent pumping pump 5 begins to re-pump the high-pressure fuel to the fuel injection device 1 for the next cycle.

A second embodiment of the present invention will be described with reference to FIG. Further, the same reference numerals are given to the structural parts common to the above-described first embodiment, and the duplicated description will be omitted. The present embodiment is different from the first embodiment in that a passage that directly communicates from the inlet 7 to the back pressure chamber 20 is not provided.

If high-pressure fuel is not rapidly supplied to the back pressure chamber 20 at the time of starting, the force for pushing up the needle valve 15 becomes strong, and the needle valve 15 rises even if the solenoid 38 is not energized. Since the portion 45 is separated, the fuel injection hole 21 is arbitrarily opened, and fuel may be ejected from the fuel injection hole 21. Therefore, in the first embodiment, the second check valve 26 is provided between the inlet 7 and the back pressure chamber 20.

However, when the orifice 27 is sufficiently large, the orifice 2 can be provided without the second check valve 26.
Due to 7, the high pressure fuel can be sufficiently supplied from the pressure accumulating chamber 23.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the structure of a first embodiment of a pressure accumulation type fuel injection device of the present invention applied to an internal combustion engine.

FIG. 2 is a time chart for explaining the operation of the first embodiment.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional pressure-accumulation type fuel injection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Accumulation type fuel injection device 2 ... Fuel injection valve 3 ... Hydraulic pressure control valve 5 ... Intermittent pressure feed type pump 6 ... Pressure adjusting means 7 ... Inlet 8 ... Holder 15 ... Needle valve 20 ... Back pressure chamber 21 ... Fuel injection hole 22 ... Oil sump 23 ... Accumulation chamber 24 ... Introduction passage 25 ... First check valve 26 ... Second check valve 27 ... First orifice 28 ... Second orifice 33 ... Drain port 35 ... Valve 37 ... Seat portion 38 … Solenoid 40… Rod 45… Seat

Claims (3)

[Claims] 1. A pressure-accumulation fuel injection device in which high-pressure fuel is pressure-fed from an intermittent pressure feed pump having a pressure adjusting means to a fuel injection valve provided for each cylinder, and the high-pressure fuel is injected by the fuel injection valve. The fuel injection valve includes an inlet, which is a high-pressure fuel supply port formed in a holder of the fuel injection valve, a pressure accumulating chamber built in the holder, and a passage provided to connect the inlet and the pressure accumulating chamber. No. 1 check valve, an oil reservoir formed around the needle valve housed in the holder, an introduction passage communicating the oil reservoir with the pressure accumulating chamber, and a back pressure provided above the needle valve. Chamber, and an orifice provided in a passage that communicates the back pressure chamber with the pressure accumulator chamber, and controls the fuel injection timing and injection amount by a hydraulic control valve that increases or decreases the pressure in the back pressure chamber. Accumulation type fuel characterized by Injection device. 2. The fuel injection section further includes a second check valve provided in a passage that connects the inlet and the back pressure chamber. Accumulation type fuel injection device. 3. The pressure-accumulation fuel injection according to claim 1, wherein the hydraulic control valve increases or decreases the pressure in the back pressure chamber by connecting and disconnecting the back pressure chamber and the drain. apparatus.