JPH0665871B2 - Fuel injection device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel injection device for an internal combustion engine.

[Conventional technology]

Conventionally, a fuel injection valve used in a fuel injection device for an internal combustion engine opens when the pumped fuel pressure exceeds a predetermined value in relation to the pressure receiving area of a nozzle needle valve and a set spring load, and falls below a predetermined value. Then, the valve is closed by the force of the spring.

From recent demands for exhaust gas purification and fuel economy, it has been found that an injection pattern in which the injection rate gradually increases at the initial stage of the injection rate and the injection rate decreases instantaneously at the final stage is desirable.

Therefore, conventionally, for example, as disclosed in Japanese Patent Publication No. 59-48302, a back pressure chamber is provided for a nozzle needle valve to control the movement of the nozzle needle valve in a desired shape by the hydraulic pressure thereof.

[Problems to be solved by the invention]

However, these conventional ones require a hydraulic power source, and the obtained injection rate pattern is only a gradual increase in the injection rate. Also, in other conventional examples, only an instantaneous decrease is obtained at the end of injection. In yet another example, there is one in which the injection pattern is aimed to gradually increase in the initial stage of injection and to decrease instantaneously in the final stage of injection, but the effect is not satisfactory.

Further, during low-speed rotation, there is a problem that abnormal injection may occur due to an increase in the residual pressure in the back pressure chamber or the injection amount may vary.

The present invention is made in view of the above problems,
With a simple configuration, an injection rate pattern that simultaneously achieves a gradual increase in the injection rate at the beginning of injection and an instantaneous decrease in the injection rate at the end of injection is used to effectively utilize the pressurization energy of the residual pressure fuel after injection, resulting in energy loss. It is an object of the present invention to provide a fuel injection device for an internal combustion engine which is realized without the need for abnormal injection and fluctuation of the injection amount due to residual pressure fluctuation.

[Means for solving problems]

The present invention has taken the following technical means in order to achieve the above object.

The present invention provides a fuel injection pump that pressurizes fuel in a fuel pressurizing chamber to a high pressure and pumps pressurized fuel through a discharge valve, and a discharge side of the discharge valve and a fuel pressurizing chamber side of the fuel injection pump. A communication passage communicating with the nozzle body, a nozzle body having an injection hole, and a fuel pressure of a pressurized fuel sent from a fuel injection pump to reciprocate in the nozzle body and open and close the injection hole of the nozzle body to open and close the internal combustion engine. A nozzle needle valve that injects fuel into the combustion chamber, a spring that contacts the end surface of the nozzle needle valve on the opposite side to the combustion chamber, and a nozzle needle valve that is formed on the opposite side of the combustion chamber and closes the nozzle needle valve. The back pressure chamber that holds the pressure in the direction to cause the fuel injection pump to communicate with the end surface of the nozzle needle valve on the combustion chamber side, and the fuel passage that communicates with the back pressure chamber. Provided near the inlet to the room The valve includes a valve closing valve and a bypass throttle provided in the middle of a bypass passage that bypasses the on-off valve. The fuel injection rate at the end of injection is instantaneously reduced, and after the fuel is injected by the nozzle needle valve, a predetermined pressure fuel on the discharge side of the discharge valve of the fuel injection pump is made to flow backward to the fuel pressurizing chamber side through the communication passage. The effective use of the pressurizing energy of the fuel having the predetermined pressure as the pressurizing energy in the next pressurizing stroke of the fuel injection pump and the fluctuation of the residual pressure that deteriorates the injection amount characteristic are prevented.

〔Example〕

Next, a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a sectional view showing the structure of this embodiment.

In FIG. 1, a fuel injection pump 100 is a conventionally known injection pump, and a plunger 101 is slidably disposed in a cylinder 102 while keeping oil tightness.

Fuel is supplied from a fuel chamber (not shown) to a fuel pressurizing chamber 113 in the cylinder 102 through a feed hole (not shown), and the plunger 101 slides upward in the figure to pressurize the fuel. The fuel in chamber 113 is pressurized.

A valve body 104 is connected and fixed to the fuel pressurizing chamber 113, and a discharge valve 103 is slidably arranged in the valve body 104.

The discharge valve 103 is urged toward the fuel pressurizing chamber 113 by a valve spring 105 arranged in a discharge chamber 114 formed on the opposite side of the fuel pressurizing chamber 113.

Therefore, the fuel in the fuel pressurizing chamber 113 is pressurized and the discharge valve 103
When the pressure exceeds the valve opening pressure, the fuel opens the discharge valve 103 against the valve spring 105, flows into the discharge chamber 103, and
Pumped through 106.

A communication passage 112 that communicates the fuel pressurizing chamber 113 and the discharge chamber 114 is provided in the discharge valve 103, and the flow of fuel from the discharge chamber 114 to the fuel pressurizing chamber 113 is provided in the communication passage 112. A check valve 110 is provided to allow only this.

The nozzle needle valve 1 is slidably arranged in the nozzle body 2 while keeping oil tightness, and the nozzle body 2 and the nozzle needle valve 1 constitute a normal nozzle valve. The nozzle needle valve 1 receives the fuel pressure of the pressurized fuel pumped from the fuel injection pump 100 and reciprocates in the nozzle body 2. Along with this reciprocating movement, one end 1a of the nozzle needle valve 1 opens and closes the injection hole 2a of the nozzle body 2 to inject fuel into the combustion chamber of an internal combustion engine (not shown).

On the other end 1b side of the nozzle needle valve 1, a back pressure chamber 8 for holding a pressure in the direction of closing the nozzle needle valve 1 is formed. In addition, a spring 3 that is in contact with the end surface of the nozzle needle valve 1 on the side of the other end 1b is arranged in the back pressure chamber 8. The spring 3 urges the nozzle needle valve 1 in a direction to close it. There is.

The fuel passage 6 communicates with the fuel injection pump 100 and the end surface of the nozzle needle valve 1 on the side of the one end 1a via a pipe 106, and also communicates with the back pressure chamber 8 via an opening / closing valve 30 and a throttle 7.
The back pressure chamber 8 is a bypass passage that bypasses the on-off valve 30.
90 to the fuel passage 6 through the bypass passage 90
Is provided with a bypass diaphragm 9 having a larger passage resistance than the diaphragm 7. It should be noted that, instead of providing the bypass throttle 90 in the bypass passage 90, the bypass passage 90 may be a narrow throttle passage.

The on-off valve 30 includes a nozzle needle valve 31, a valve body 32, and a spring 33, and the nozzle needle valve 31 slides in the valve body 32 while keeping oil tightness.
The nozzle needle valve 31 is biased in the seating direction by a spring 33 so as to be seated as shown in FIG.
The opening pressure of the on-off valve 30 is set slightly higher than the opening pressure of the nozzle valve.

Next, the operation of this embodiment will be described.

In FIG. 1, fuel is supplied to the fuel pressurizing chamber 113, and when the plunger 101 slides in the cylinder 102 upward in the drawing, the fuel in the fuel pressurizing chamber 113 is pressurized. When the fuel in the fuel pressurizing chamber 113 is pressurized and becomes equal to or higher than the opening pressure of the discharge valve 103, the fuel flows against the valve spring 105 to open the discharge valve 103 and flow into the discharge chamber 114.

The fuel discharged into the discharge chamber 114 is pressure-fed into the fuel passage 6 through the pipe 106. After that, the fuel is branched into two directions, one of which is pumped to the nozzle valve and the other to the on-off valve 30.

When the pressure of the pumped fuel rises and reaches the valve opening pressure of the nozzle valve (determined by the pressure receiving area of the spring 3 and the nozzle needle valve 1), the nozzle needle valve 1 rises against the urging force of the spring 3. Then, the nozzle valve is opened and fuel injection is started.

Immediately after the nozzle valve is opened, the fuel pressure increases due to the pumped fuel, and the opening pressure of the opening / closing valve 30 (determined by the set load of the spring 33 and the pressure receiving area of the needle valve 31) is reached to open the opening / closing valve 30. To do. As a result, a part of the pumped fuel from the fuel passage 6 flows into the back pressure chamber 8 via the throttle 7.

At this time, the nozzle needle valve 1 receives a force determined by the pressure of the back pressure chamber 8 and the cross-sectional area of the guide portion of the nozzle needle valve 1 in the valve closing direction. Therefore, the nozzle needle valve 1 does not rise rapidly but rises gently, and the initial slow fuel injection rate is achieved.

When the pumped fuel is further pumped, the on-off valve 30 is in the open state, so the nozzle needle valve 1 gradually opens against the force acting in the valve closing direction due to the increase in the fuel pressure, and the fuel injection is performed. Done.

After that, when the fuel is injected by a predetermined amount, the pressure feed is reduced and the pressure in the fuel passage 6 is lowered. At this time, the pressure in the back pressure chamber 8 is lowered by the throttle 7 later than the pressure in the fuel passage 6, so that the pressure in the back pressure chamber is always increased and the level thereof is adjusted by the throttle 7.

Since the valve closing force resulting from the combined force of the force determined by the pressure difference and the cross-sectional area of the guide portion of the nozzle needle valve 1 and the force of the spring 3 becomes extremely large (that is, the valve closing force becomes high), the nozzle needle valve 1 suddenly moves. A valve closing behavior is performed.

When the pressure further decreases, the on-off valve 30 also closes, and the state shown in FIG. 1 is obtained.

At this time, although the residual pressure still exists in the back pressure chamber 8, the fuel flows out into the fuel passage 6 whose pressure has been reduced by the bypass throttle 9. Further, this fuel is introduced into the fuel injection pump 100 side through the pipe 106, and sequentially through the communication passage 112 and the check valve 110 provided in the seated discharge valve 103, the fuel pressurizing chamber on the low pressure side. Backflow into 113. Therefore, by the next injection, the back pressure chamber 8, the fuel passage 6 and the pipe 106 are restored to the low pressure level, and the residual pressure in the fuel pressurizing chamber 113 remains.
Is effectively reused as the pressurizing energy in the pressurizing process of No. 1, and the problem of energy loss does not occur.

Further, by this, it is possible to prevent the occurrence of abnormal injection, non-injection, and variation in the injection amount due to the synergistic effect of the increase in the residual pressure of the back pressure chamber 8 and the fuel passage 6 and the increase in the valve opening pressure of the nozzle valve in the low speed rotation range. You can

Although the bypass passage 90 is always in communication with the back pressure chamber 8, since the passage area of the bypass passage 90 is narrowed by the bypass throttle 9, the initial inflow amount is small, and almost no nozzle valve is opened. It has no effect.

In addition, the low pressure level after the completion of fuel injection is the check valve 110, the throttle 11
2 is set in advance, but depending on the size of the dead delium (determined by the back pressure chamber 8, the pipe 106, etc.), etc. adjust.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. 2 is a sectional view showing the configuration of the second embodiment of the present invention, and FIG. 3 is an operation explanatory view showing the movement of each part with the passage of time.

In FIG. 2, on the other end 1b side of the nozzle needle valve 1, a back pressure chamber 8a for holding a pressure in the direction of closing the nozzle needle valve 1 is provided.
Are formed. In the back pressure chamber 8a, a first spring 3 that comes into contact with the end surface of the nozzle needle valve 1 on the side of the other end 1b is arranged, and the spring 3 urges the nozzle needle valve 1 in a direction to close it. ing.

In addition, a pin 4 is provided on the other end 1b side of the nozzle needle valve 1 with a predetermined gap, and when the nozzle needle valve 1 moves up by a predetermined amount, it is locked by one end 4a of the pin 4. ing.

On the other end 4b side of the pin 4, there is formed a back pressure chamber 8b for holding a pressure in the direction of urging the pin 4 downward in the figure. Also,
A second spring 5 is provided in the back pressure chamber 8b so as to come into contact with the end surface of the pin 4 on the side of the other end 4b.

The on-off valve 30 is composed of a nozzle needle valve 31, a valve body 32, and a spring 33, and a back pressure chamber for holding a pressure in a direction for urging the nozzle needle valve 31 downward in the figure on one end 31a side of the nozzle needle valve 31. 35 are formed. The spring 33 is arranged in the back pressure chamber 35 and biases the nozzle needle valve 31 downward in the figure. Back pressure chamber 35
Communicates with the back pressure chamber 8b through the diaphragm 34.

The other structure is the same as that of the first embodiment.

Next, the operation of this embodiment will be described.

The fuel pressurized by the fuel injection pump 100 is pumped into the fuel passage 6 through the pipe 106. After that, the fuel is branched into two directions, one of which is pumped to the nozzle valve and the other to the on-off valve 30.

When the pressure of the pumped fuel rises and reaches the valve opening pressure of the nozzle valve (determined by the pressure receiving area of the first spring 3 and the nozzle needle valve 1) (A in FIG. 3), the nozzle needle valve 1 Rises against the biasing force of the first spring 3 and the nozzle valve opens.

The nozzle needle valve 1 of the nozzle valve comes into contact with the pin 4 and stops when it rises by a set predetermined gap (A 'in FIG. 3).
In this state, the nozzle valve is open, so fuel is injected.

However, the nozzle needle valve 1 does not rise up to the full stroke, but only rises by a predetermined small gap.
Therefore, the fuel flow passage area is small, and the pumping pressure is still small, so the injection rate is small.

Next, when the pumped fuel is further pumped, the fuel pressure rises, and the opening pressure of the opening / closing valve 30 (the set load of the spring 33 and the needle valve
(Determined by the pressure receiving area of 31)) and the opening / closing valve 30 opens. As a result, the pumped fuel from the fuel passage 6 flows into the back pressure chamber 35 via the throttle 34 and into the back pressure chamber 8b via the throttle 7. Further, since the back pressure chamber 8b communicates with the back pressure chamber 8a, the pumped fuel further flows into the back pressure chamber 8a. Therefore, the back pressure chamber 35, the back pressure chamber 8a, and the back pressure chamber 8b have equal pressures.

At this time, the nozzle needle valve 1 has the pressure of the back pressure chamber 8a and the nozzle needle valve 1
Receives a force that is determined by the cross-sectional area of the guide section in the valve closing direction. As a result, the nozzle needle valve 1 descends and closes (B 'in FIG. 3), and the injection is once stopped.

By closing the valve, the pressure in the fuel passage 6 further rises, and the valve opening pressure determined by the combined force of the urging force of the first spring 3 and the force of the pressure of the back pressure chamber 8a and the pressure receiving area of the nozzle needle valve 1. (Higher than it was initially) (C in Fig. 3)
Then, the nozzle needle valve 1 again rises and the injection is restarted.

When the pumped fuel is further pumped, the on-off valve 30 is in the open state, so that the nozzle needle valve 1 bends the first spring 3 and then the spring 5 as well because the on-off valve 30 is open. Injection is performed.

After that, when injection is performed by a predetermined amount, pumping decreases,
The pressure in the fuel passage 6 becomes low. At this time, since the pressure in the back pressure chambers 8a, 8b is lowered by the throttle 7 later than the pressure in the fuel passage 6, the pressure in the back pressure chambers 8a, 8b is always higher than the pressure in the fuel passage 6. And the level is adjusted by the diaphragm 7.

Due to the resultant force of the pressure difference and the cross-sectional area of the guide portion of the nozzle needle valve 1 and the urging force of the springs 3 and 5, the valve closing force for the nozzle valve becomes extremely large (that is, the valve closing pressure becomes high), so that it suddenly increases. The closing behavior of the nozzle needle valve 1 is performed (D in FIG. 3).

Further, at this time, the pressure in the back pressure chamber 35 also decreases later than the pressure in the fuel passage 6, so that the nozzle needle valve 31 receives a force in the valve closing direction due to the resultant force of the fuel pressure and the urging force of the spring 33. The on-off valve 30 also closes (E to E'in FIG. 3) as the pressure in the fuel passage 6 decreases, and the state shown in FIG. 2 is obtained.

The following operation is the same as that of the first embodiment.

As described above, according to the configuration of this embodiment, pilot injection can be achieved in the entire rotation speed range or the specific rotation speed range.

It is also possible to keep the initial injection rate low without performing pilot injection with the same configuration as this embodiment.

In this case, for example, the valve opening pressure of the opening / closing valve 30 is set higher than the second valve opening pressure determined by the second spring 5, and the nozzle needle valve 1 of the nozzle valve is opened after rising to the maximum lift. Can be achieved.

Further, in the case of setting in this way, the nozzle needle valve 1 does not close during continuous injection, and therefore pilot injection does not occur, but the nozzle needle valve 1 has a two-stage lift behavior and the first stage Since the flow path is narrow at the time of lift, the initial injection rate can be lowered to gradually increase the fuel injection rate, and when the valve is closed, the opening / closing valve 30 is opened to increase the pressure in the back pressure chambers 8a, 8b. The valve closing force is increased, enabling rapid valve closing.

Also, in one engine, the opening pressure of the on-off valve 30 and the throttle 7
By adjusting and, the pilot injection is performed at low speed rotations where the oil feed rate per hour of the pumped fuel is small, and at high speed rotations where the oil feed rate is large, the fuel is pumped so that temporary valve closing during injection is not performed. It is also possible not to perform pilot injection so as to overcome the back pressure, but simply perform injection with a low initial injection rate.

Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 4 shows the fuel injection pump 10 shown in the two embodiments.
FIG. 7 is a cross-sectional view of a main part showing a modified example of the discharge valve 103 of 0.

In FIG. 4, the discharge valve 103 is provided with a communication passage 112, and the communication passage 112 on the discharge chamber 114 side is a throttle 115. That is, the reverse flow of fuel for recovering the residual pressure after injection to the low pressure level is performed through the throttle 115, and the same effect as the first embodiment can be achieved with a simple configuration.

〔The invention's effect〕

As described above, according to the present invention, the injection rate pattern that simultaneously achieves the gradual increase in the injection rate at the initial injection and the instantaneous decrease in the injection rate at the final injection is used to pressurize the residual pressure fuel after injection. It is possible to effectively use energy without energy loss and to realize abnormal injection due to residual pressure fluctuation and variation in injection amount, and prevent abnormal injection due to residual pressure variation and variation in injection amount.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of the first embodiment of the present invention. 2 and 3 relate to the second embodiment, FIG. 2 is a sectional view showing the configuration of the second embodiment, and FIG. 3 is an operation explanatory view showing the movement of each part with the passage of time. . FIG. 4 is a cross-sectional view of essential parts showing a third embodiment of the present invention. 1 …… Nozzle needle valve, 2 …… Nozzle body, 2a …… Injection hole, 3 ……
Spring, 6 ... Fuel passage, 8 ... Back pressure chamber, 9 ... Bypass throttle, 30 ... Open / close valve, 90 ... Bypass passage, 100 ... Fuel injection pump, 103 ... Discharge valve, 112 ... Communication Passage, 113 …… Fuel pressurization chamber, 114 …… Discharge chamber.

Claims (1)

[Claims] 1. A fuel injection pump for pressurizing fuel in a fuel pressurizing chamber to a high pressure and pumping pressurized fuel through a discharge valve; a discharge side of the discharge valve of the fuel injection pump and a fuel pressurizing chamber side. And a nozzle body having a nozzle hole, and a reciprocating motion in the nozzle body upon receipt of the fuel pressure of the pressurized fuel pumped from the fuel injection pump, and one end of the nozzle body having the nozzle hole. A nozzle needle valve that opens and closes the nozzle to inject fuel into the combustion chamber of the internal combustion engine; a spring that abuts the other end side end surface of the nozzle needle valve; and the nozzle needle that is formed on the other end side of the nozzle needle valve. A back pressure chamber for holding the pressure in the direction of closing the valve, a fuel passage communicating with the fuel injection pump and the one end surface of the nozzle needle valve, and a fuel passage communicating with the back pressure chamber, and in the middle of this fuel passage And An opening / closing valve provided near the inflow portion to the back pressure chamber and a bypass throttle provided in the middle of a bypass passage bypassing the opening / closing valve are provided, and the pressure in the back pressure chamber is adjusted by opening / closing the opening / closing valve. The fuel injection rate is gradually increased at the beginning of fuel injection and the fuel injection is instantaneously decreased at the end of fuel injection, and a predetermined pressure fuel on the discharge side of the discharge valve of the fuel injection pump is pressurized with fuel after completion of fuel injection by the nozzle needle valve. Residual pressure that causes reverse flow to the chamber side through the communication passage to effectively use the pressurizing energy of the predetermined pressure fuel as pressurizing energy in the next pressurizing stroke of the fuel injection pump and to deteriorate the injection amount characteristic. A fuel injection device for an internal combustion engine, which prevents fluctuations.