JPH01267352A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To lower the coefficient of fuel injection during the initial stage of combustion injection and to reduce the generation of noise, by a method wherein a pressure accumulating chamber is formed above a needle valve body pressed through the force of a spring and forced into contact with a valve seat, and a fuel passage connected to the valve seat is communicated to the pressure accumulating chamber through a throttle. CONSTITUTION:A lower part 4 of a valve body and a pressure accumulating chamber cover 5 are secured by threadely joining a nut body 3 with an upper part 2 of the valve body. The lower part 4 of the valve body is provided at its tip with an injection nozzle 7 and a valve seat 8, a fuel passage 9 a part of which forms a working chamber 11, a slide hole 10 in which a needle valve body 12 is slid. The needle valve body 12 is formed such that a slide part 13, a needle valve 14 freely capable of making contact with the valve seat 8, a small part 15, and a push rod 16 are formed integrally. A pressure accumulating chamber 18 is formed between an upper end 13a of the slide part 13 of the needle valve body 12 and a lower end 15a of the pressure accumulating chamber cover 5, and is communicated to the working chamber 11 through a throttle groove 19. The needle valve body 12 is pressed downward through a seat 20 through the force of a spring 21. The fuel passage 9 is connected to a fuel injection pump through fuel passages 22 and 23.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a fuel injection valve for a diesel engine in which the fuel injection rate is variable.

(Prior Art) A generally well-known fuel injection valve for diesel engines is an automatic valve, as shown in Fig. 5. A tip needle valve 104 is attached to a nozzle 106 in a sliding hole 102 drilled in the lower part of the valve body 101.
A needle valve body 103 is provided in contact with a nearby valve seat 107, and this is pressed downward by a valve spring 108 via a seat 109.

The pressure P of the fuel oil flowing into the passage 110 and applied to the lower end of the pressure receiving part 105 of the needle valve body 103 rises and tries to push up the needle valve body 103, and the force of the area (x-y) x pressure P is applied to the spring 108. When the force exceeds the force pushing down the needle valve body +03, the needle valve body 103 moves upward, the needle valve 104 separates from the valve seat 107 and opens, and fuel oil is injected from the nozzle 106.

As a result, the pressure receiving area of the needle valve body 103 increases from (x-y) to Cx), and the pressure of the fuel oil is also applied to the lower surface of the needle valve body +03, so there is a force pushing the needle valve body 103 upward. increases and rapidly rises until the upper end 103a of the needle valve body 103 collides with the upper end 10Ja of the sliding hole.

To explain this with reference to FIG. 6, the horizontal axis in FIGS. 6A to 6D is time, and the vertical axis in FIG. Figure B shows the force pushing up the needle valve element 103 due to the pressure inside the fuel passage and the force pushing down the needle valve element 103 by the spring 108, Figure C shows the lift of the needle valve element 103, and the same figure shows the change in fuel injection rate. Each is shown.

As described above, the pressure inside the fuel passage increases from Po toward P and J due to oil feeding from the fuel injection pump, and this pressure is applied to the pressure receiving portion 103a of the needle valve body 103 as described above.

Since the pressure receiving area at this time is (x-y), the needle valve body 1
The force F1 that pushes up 03 is P+X(x y).

On the other hand, the force of the spring 108 pushing down the needle valve body 103 is F,
Therefore, if the pressure inside the passage becomes higher than P, the needle valve body 103 will be pushed down by the force F of the spring 108.
, rises against. At this time, P is also applied to the lower surface of the needle valve 104.
When a pressure of l is applied, the force pushing up the needle valve body 103 is F
The needle valve body 103 increases rapidly as t=P+xx, rapidly accelerating the needle valve body 103 until its upper end collides with the upper end 10JFa of the sliding hole 102. The lifting up to Karari is carried out rapidly. Here, the time difference T. and T are due to acceleration delays due to the mass of the needle valve body.

The downward force of the spring 108 increases from Fl to F3 due to the lifting height of the needle valve body 03, but at this time the needle valve body 1
As shown by the solid line in FIG.
maintains the total head.

When approaching the fuel injection path, the pressure inside the passage 110 becomes P.
, and at this time, the force F3 pushing up the needle valve body 103 is F3=P! XX and the force F with which the spring 108 pushes down the needle valve body 103 become equal.

As the pressure inside the fuel passage decreases, the needle valve body 103 releases the spring 1.
It is pushed down by the force of 08, and at time T, the pressure force P,
Then, the force pushing up the needle valve body 103 is F+=PsX
x is equal to or less than the above F, and the lift height of the needle valve body 103 is Lo
The needle valve closes.

Therefore, the fuel passage internal pressure P3 when the needle valve 104 is closed is P
+ / x, and the pressure P1 when the valve opens is P + =
It becomes lower than F +/x −y, lowering the fuel injection rate when the valve is closed.

In reality, the spring 108 accelerates the needle valve body ■03, which has mass, to close the valve, and the valve closes not at time T, but at
An acceleration delay occurs, which takes place at a time T, and during this acceleration delay, the pressure within the fuel passage 110 further decreases to P4. Therefore, the fuel injection rate, which is proportional to the pressure inside the fuel passage, inevitably becomes smaller near the fuel injection path, as shown in Figure 6.

(Problem to be solved by the invention) However, the fuel injected at a high fuel injection rate at the beginning of injection burns rapidly in the combustion chamber of a diesel engine, increasing the rate of pressure rise and causing combustion noise caused by so-called diesel knock. This causes an increase in the maximum combustion pressure and an accompanying increase in the combustion temperature, making it easier to generate harmful NOX.

Also, is there a decrease in the fuel injection rate around the injection path and an increase in the fuel injection time due to this? This coarsening of the fuel spray due to the decrease in injection pressure causes a so-called afterburning phenomenon, which not only causes the generation of harmful black smoke and CO1HC due to incomplete combustion, but also reduces thermal efficiency.

In response to this, attempts have been made to reduce the mass of the needle valve body 103 to shorten the acceleration delay, but this has not resulted in a fundamental performance improvement.

In view of the above, the present invention provides a fuel injection valve that lowers the fuel injection rate at the beginning of fuel injection, increases the fuel injection rate around the injection path, and shortens the fuel injection period, thereby reducing the NOx, G and
It was invented for the purpose of reducing O and HC and improving thermal efficiency.

(Means for Solving the Problems) In order to achieve the above object, the fuel injection valve of the present invention has a sliding hole 10 formed in the lower part 4 of the valve body, in which the needle valve 14 contacts the valve seat 8 near the injection lower part. , a needle valve body 12 whose upper end is pressed downward by a spring 21 is disposed, and a pressure accumulation chamber 1 is disposed above the needle valve body 12.
2, the pressure accumulation chamber! 2, the fuel passage 2'3, 22.9 communicating with the valve seat 8 is communicated via a throttle 19.27.

(Function) With the above configuration, when the valve opens due to an increase in the pressure inside the fuel passage at the beginning of fuel injection, the lift of the needle valve body 12 causes the pressure accumulation chamber 18 to
The fuel inside is compressed to increase the pressure, which causes the needle valve body 1 to
2, the valve opening speed is lowered and the fuel injection rate is lowered. In the combustion chamber of the engine, the rate of heat generation at the initial stage of combustion is lowered, and the rate of increase in combustion pressure is lowered.

When the valve near the fuel injection path is closed, the pressure in the pressure accumulator is restricted to 19.
．． The pressure inside the fuel passage is increased through 27, and this pressure is applied to the upper end of the needle valve body 12, and in cooperation with the spring 2I, the needle valve 4 of the needle valve body 12 contacts the valve seat 8 and closes. The pressure inside the fuel passage at the time of the start of valve closing is 6 higher than that at the end of valve opening, and by increasing the pressure inside the fuel passage at the end of valve closing, the spray particles injected from the injection lower near the fuel injection path are By reducing the diameter, combustion conditions in diesel engines are improved. In addition, high-pressure injection when the valve is closed increases the fuel injection rate to avoid afterburning, reduces black smoke, CO, and HC emissions, and further increases the isovolume of the Savana cycle. , the thermal efficiency of diesel engines is improved.

(Example) Embodiments of the present invention will be described in detail below based on the drawings.

refers to the valve body of the fuel injection valve of the present invention, which includes an upper valve body 2, a nut body 3 screwed to this, a lower valve body 4 inserted into the nut body 3, and a pressure accumulator cover 5; It consists of a stopper 6 that is screwed to the upper part 2 of the valve body.

The lower part 4 of the valve body has an injection lower at its tip and a valve seat 8 formed close to this, and a fuel passage 9 communicating with the valve seat 8 is formed, and a needle valve body I2 described later slides on the axis. Sliding hole l
O is open. Note that the vicinity of the fuel passage 9 in front of the valve seat 8 is expanded in the horizontal direction to form an action chamber 11.
It consists of

The needle valve body 12 integrally forms a needle valve 14 with a cross-sectional area A in contact with the valve seat 8 below a sliding portion 13 with a cross-sectional area A+, and has a small diameter portion with a cross-sectional area A above it. 15 and push rod 16 are also integrally provided.

The needle valve body 12 has the sliding part 13 in the sliding hole 10 of the lower part 4 of the valve body, and the small diameter part 15 in the pressure accumulator cover 5.
When the needle valve 14 contacts the valve seat 8, the sliding portion 1 of the needle valve body 12
A pressure accumulation chamber 18 is formed between the upper end 13a of the pressure accumulation chamber cover 5 and the lower end 5a of the pressure accumulation chamber cover 5. Note that 19 is a throttle groove formed on the side surface of the sliding portion I3, which
The pressure storage chamber 18 is connected to the pressure storage chamber 18.

The upper end of the push rod 16 of the needle valve body 12 is removed from the valve body upper part 2.
Inside, the needle valve 14 is pressed against the valve seat 8 by a downward pressing force from a spring 21 installed between the spring seat 20 and the stopper 6 via the spring seat 20.

Reference numeral 22 denotes a fuel passage opened in the pressure accumulator cover 5, which connects the fuel passage 9 opened in the upper part 4 of the valve body and the upper part of the valve body KS2.
The fuel passage 23 is connected to a fuel injection pump (not shown). In addition, 2
4 is a leak hole made in the stopper 6.

Next, the operation of the above embodiment will be explained.

When fuel from a fuel injection pump (not shown) flows into the fuel passages 23, 22 and 9, the pressure in the fuel passages begins to rise from P0 in FIG. At this time, the pressure in the pressure accumulation chamber 18 that communicates with the action chamber 11 via the throttle groove 19 is also Po, and the rate of pressure increase in the pressure accumulation chamber 18 is as low as PoPt as shown by the dotted line in Figure 2 due to the above-mentioned throttle WIt19. .

When the pressure inside the fuel passage reaches P, f shown in FIG. 2B
+= P +X (A + A3), the spring force fl-f! and the pressure inside the pressure storage chamber 18 r t-P t
The needle valve 14 attempts to open against a force of (A + - A3), and when the force P exceeds, the needle valve 14 separates from the valve seat 8 and opens, and fuel injection from the injection lower begins.

At the same time as the valve opens, the pressure receiving area of the needle valve body 12 is (A I-8,)
The force that tries to push up the needle valve body 12 increases to fs-P+xA in FIG. 2B,
This force f accelerates the upward movement of the needle valve element I2, increasing its speed. During the period -tl, the head is increased to 1°-1.

As the lift of the needle valve element I2 increases, the fuel in the pressure accumulator chamber I8 is compressed, and the pressure in the pressure accumulator chamber 18 becomes P? in FIG. 2A. P3 P4 increases sequentially, and in the middle of the lift (at the pressure of P3 at time t2J, P + X (A, -A3) + force of the spring 21 f 4 ” f s = P s X A I
Therefore, the increase in the lift of the needle valve body 12 is limited by the increase in the pressure inside the pressure storage chamber 18. The lifting height of the needle valve body 12 at this time is 1.C in FIG. The fuel injection rate until the fuel passage pressure reaches P is low as shown by ro-rl in the second diagram because the fuel passage pressure and the lift of the needle valve body 12 are small.

Furthermore, when the pressure inside the fuel passage increases, the fuel in the pressure accumulation chamber 18 and the spring 21 are further compressed, and at time t, p e
A I = r e = p 4x (A I - A
3) When the force f7 of the spring 21 is reached and the pressure inside the fuel passage exceeds Pa, the upper end 15 of the small diameter portion 15
a is in contact with the upper end 17a of the blind hole 17, and 1 in FIG.
It is not possible to increase the lift further than this.

The fuel injection rate is determined by the time jt as shown in the second diagram.
jt is lower than rl-rt and a conventional fuel injection valve.

After this, the pressure inside the fuel passage increases further as shown in Fig. 2A, so the force that tries to open the needle valve 14 also increases as shown in Fig. 2B, and the needle valve I4 continues to open, but the pressure builds up. room 18
High-pressure fuel in the working chamber 11 of the fuel passage 9 is supplied through the throttle groove 19 to continue increasing the pressure in the pressure accumulating chamber 18.

While the pressure within the pressure accumulation chamber 18 continues to rise, the pressure within the fuel passage begins to decrease as the end of fuel injection approaches. The force f8-P that tries to open the valve in this process? X A l
and the force that tries to close the valve P eX (A + - A,)
At time t3 when the force ft=fa at the full lift of the spring 21 becomes equal, the opening and closing forces of the needle valve 14 are balanced, and from then on, the lift of the needle valve body 12 decreases as the pressure inside the fuel passage decreases. continues to decline. As a result, the spring 21 pushes down the needle valve body 12, so the volume of the pressure accumulation chamber I8 increases, and the pressure accumulation chamber 1
The pressure within 8 decreases and the force trying to open needle valve 14 continues to decrease.

Force that tries to open the needle valve 14 P s x A + ”
The force P + oX (A I
The needle valve 14 tries to close at the time t4 when A3) + the force f when the spring 21 is fully closed + fy=f* is balanced, but the mass of the needle valve 14 causes an acceleration delay between t4 and ts, The valve closes at the point of . During this time, the pressure inside the fuel passage is P
It decreases to II. However, this pressure PII is extremely high compared to conventionally known pressure due to the action of the pressure accumulation chamber 18 and the throttle groove 19, and it not only reduces the particle size of the fuel spray in the period at the end of fuel injection, but also reduces the fuel injection rate. This made it possible to improve

After the end of fuel injection, the fuel in the pressure accumulator 18 continues to overflow as the pressure inside the fuel passage decreases, and as shown in FIG. and prepare for the next fuel injection.

Other embodiments are shown in FIGS. 3 and 4, with the same symbols and symbols as in FIG. 1 representing the same parts. cover 5
The upper part 2 of the valve body is in direct contact with the lower part 4 of the valve body, and is connected by the nut body 3. In addition, the small diameter portion 15 of the needle valve body 12 is eliminated, and the pressure accumulation chamber 18 is located between the upper surface of the sliding portion 13 of the needle valve body 12 and the lower surface 2a of the valve body upper part 2, and the push rod 16
It is formed by a rectangular cross-section spring 21' formed between the insertion hole 25 and the valve body upper part 2, and a storage chamber 26 for the spring seat 20. In addition, the aperture groove 19 in FIG.
Instead, a gap 27 is formed between the fuel passage 23 and the insertion hole 25.

28 is an air vent valve screwed to the leak hole 24 formed in the stopper 6. In addition, a protrusion 6a is formed at the center of the stopper 6, and when the needle valve 14 is closed, the upper surface 13a of the sliding portion 13 of the needle valve body 12 and the upper surface 20 of the valve body are formed between the upper surface of the spring seat 20 smaller than the distance between the lower surfaces 2a,
A gap d is provided that contacts only when the needle valve body 12 is at its full lift.

The example shown in FIG. 4 is basically the same as the example shown in FIG. 3 except that the spring 2I has a round cross section, and a needle valve 30 that moves forward and backward by a screw 29 is inserted into the leak hole 19°. The only difference is that the cross-sectional area can be changed.

In the embodiment shown in FIGS. 3 and 4 having the above configuration, when oil is supplied from the fuel injection pump and the pressure inside the fuel passage increases from PO to P, fuel is supplied from the throttle 27 and the pressure inside the pressure accumulation chamber 18 increases. The pressure also increases from Po to P in FIG.

The force trying to open the valve is f+-P +X shown in Figure 2B.
(A + At), the entire upper surface of the sliding part 13 receives the pressure in the pressure accumulation chamber I8, and the pressure inside the pressure accumulation chamber 18 P tx
The needle valve I resists the force A + and the force f + ft of the spring.
Trying to open 4. When the pressure inside the fuel passage exceeds Pl, the needle valve 14 moves away from the valve seat 8, opens, and starts injecting fuel from the injection lower.

At the same time as the valve opens, the pressure-receiving area of the needle valve body 12 increases from (A, -At) to A, and as a result, the force that tries to push up the needle valve body 12 is f, =P, xA1 in Fig. 2B. This force f3 increases the lifting height while accelerating the upward movement of the needle valve body 12.

-F Note As the lift of the needle valve body 12 increases, the fuel in the pressure accumulator 18 is compressed and the pressure increases as shown in Fig. 2A, and at the pressure of P3 in the middle of the lift (time 11), P 3
The force f4=fs of the ++ spring 21 becomes equal to the force r],×Δ1 that attempts to open the needle valve 14, and the increase in the lift of the needle valve body 12 is limited.

Furthermore, when the pressure inside the fuel passage increases, the fuel in the pressure accumulation chamber 18 and the spring 2I are further compressed, and after a while, P@×AI
= f6 = P4 The head cannot be increased beyond 1.

After this, the pressure inside the fuel passage increases further as shown in Fig. 2A, so the force trying to open the needle valve 14 also increases as shown in Fig. 2B, and the needle valve 14 continues to open, but the pressure builds up. room 18
is supplied with high-pressure fuel in the fuel passages 23, 22 and 9 through the throttle 27, which continues to increase the pressure in the pressure accumulator 18.

While the pressure in the pressure accumulation chamber 18 continues to rise, the pressure in the fuel passage begins to decrease as it approaches the fuel injection path, resulting in a force trying to open the valve f a = P tx A I and a force trying to close the valve P , X A, the force f at the full lift of the spring 2I, and -f become equal at time t3, when the needle valve 14
The opening and closing forces are balanced, and from then on, the lift of the needle valve body 12 continues to decrease as the pressure inside the fuel passage decreases. As a result, the spring 21 pushes down the needle valve body 12, so the pressure accumulation chamber ■
8 increases, the pressure within the pressure accumulator 18 decreases, and the force trying to open the needle valve 14 continues to decrease.

Force trying to open the needle valve 14 p e X A H-f
The needle valve 14 tries to close at the time t4 when e is balanced with the force P , , x A , + the force f + ft - fs when the spring '21 is fully opened, but the needle valve I4
An acceleration delay occurs due to the mass of , and the valve closes at time t.

After the end of fuel injection, the fuel in the pressure accumulator 18 continues to overflow from the throttle 27 as the pressure in the fuel passage decreases.
As shown in Figure A, Pa becomes Pa at time t8.

In the one shown in FIG. 4, the needle valve 30 is connected to the screw 29.
By moving forward and backward within the leak hole 19°, the pressure inside the pressure accumulation chamber 18 can be adjusted and the characteristics of the fuel injection valve can be changed.

(Effects of the Invention) As described above, the present invention includes a needle valve body in which the needle valve touches the valve seat near the nozzle, and whose upper end is pressed downward by the valve spring, in the sliding hole drilled in the lower part of the valve body. In addition, a pressure accumulation chamber is formed above the needle valve body, and a fuel passage leading to the valve seat is communicated with the pressure accumulation chamber via a throttle, thereby reducing the fuel injection rate at the beginning of fuel injection, thereby reducing the diesel fuel injection rate. It is possible to perform combustion in the combustion chamber of the engine by lowering the rate of heat release, lowering the rate of increase in combustion pressure F, lowering combustion noise1, and reducing the amount of NOx produced.

Furthermore, by increasing the fuel injection rate around the injection path and shortening the fuel injection period, it is possible to suppress the occurrence of afterburning during combustion in a diesel engine, thereby reducing black smoke, CO and HC, and improving thermal efficiency. It has the effect of Furthermore, the fuel injection valve of the present invention has a simple structure and can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the fuel injection valve of the present invention, Fig. 2 is a performance curve diagram thereof, Fig. 3 is a longitudinal cross-sectional view of another embodiment of the fuel injection valve of the present invention, and Fig. 4 is a longitudinal cross-sectional view of the fuel injection valve of the present invention. FIG. 5 is a partial longitudinal sectional view of still another embodiment of the valve, and FIG. 6 is a longitudinal sectional view of a conventional fuel injection valve, and FIG. 6 is a performance curve diagram thereof. l; Valve body, 2: Upper valve body, 3; Nut body, 4; Lower valve body, 5; Accumulator chamber cover, 6; Stopper, 7: Nozzle, 8; Valve seat, 9.22, 23. Fuel passage, lO; sliding/work opening, ll: action chamber,! 2. Needle valve body, 13; Sliding part, 14; Needle valve, +5
．． Small diameter section, 16. Push rod, 17; blind hole, +8. Pressure accumulation chamber, 19; Throttle groove, 20: Spring seat, 21. Spring, 24.24°; Leak hole, 26; Spring storage chamber, 27;
Throttle, 28; Air bleed valve, Atsushi X on the drawing (change in content, n-) Ml Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendment (method) % formula % 1. Indication of incident Patent Application No. 96615 2, filed in 1988, title of invention: Fuel injection valve 3, relationship with the case of the person making the amendment Patent applicant address: 8-2 Watada Mukai-cho, Kawasaki-ku, Kawasaki-shi, 1988 0
July 2nd (Delivery port: July 2nd, 1988) 5. Subject of amendment Drawing 6. Contents of amendment

Claims (1)

[Claims] 1) A needle valve element is disposed in the sliding hole drilled in the lower part of the valve element, the needle valve touches the valve seat near the nozzle, and the upper end is pressed downward by a spring, and pressure is accumulated above the needle valve element. A fuel injection valve characterized in that a chamber is formed, and a fuel passage leading to the valve seat is communicated with the pressure accumulation chamber via a throttle.