JPH0521659Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an engine fuel injection device, and in particular, to an engine fuel injection device that has a simple configuration and can improve the control accuracy of fuel injection amount control. It is related to the device.

<Prerequisite configuration> The fuel injection device for an engine to which the present invention is applied is, for example, a fuel supply device that meters and supplies fuel at a predetermined pressure in accordance with the load condition of the engine, as shown in FIG. 1, and a filter 2 that removes foreign substances from the fuel supplied from the fuel supply device 1.
A fuel injection device for an engine comprising: a fuel injection pump 3 that presses fuel supplied from a fuel supply device 1 and from which foreign matter has been removed by a filter 2 into a fuel injector 4; and a fuel injector 4; As shown in FIGS. 1 and 3, the fuel injection pump 3 has a pump chamber 5, an inlet passage 6 for introducing fuel from the filter 2 into the pump chamber 5, and an inlet valve 7 for opening and closing this inlet passage 6. This is a fuel injection device for an engine that has a prerequisite configuration.

<Prior Art> Conventionally, a fuel injection device for an engine is designed to change the fuel injection amount in response to the engine load in order to change the engine output in response to the engine load. As a method for changing the fuel injection amount, a method is usually adopted in which fuel is supplied at a predetermined pressure and the fuel supply time is adjusted in accordance with the load state of the engine. That is, by supplying pressure-regulated fuel to a fuel injection nozzle and adjusting the opening time of a solenoid valve that also serves as an injection nozzle valve. There is a method of adjusting the fuel supply time.

In the latter case, although there is an advantage that fuel injection timing and fuel injection amount can be accurately controlled,
In addition to the complicated structure of the fuel injection nozzle, it also requires a load detection means that detects the engine load state based on engine speed, engine gas temperature, engine coolant temperature, etc., and a control target value based on the detection result of this means. This method requires complicated electric circuits such as a calculation means for calculating a control value based on the calculation result of the calculation means and a drive means for driving the electromagnetic valve based on the calculation result of the calculation means, which has the disadvantage of being expensive. Furthermore, when the fuel injection pressure becomes high, a very large electromagnetic valve is required, so that it is extremely impractical as a fuel injection device for engines that require high-pressure injection, such as diesel engines.

As a result, especially in fuel injection devices such as diesel engines, the pressure is regulated in the fuel injection nozzle.
The mainstream method is to supply a metered amount of fuel.

Among the methods of supplying pressure-regulated and metered fuel to a fuel injection nozzle, there is a method of supplying pressure-regulated fuel to a fuel injection pump connected to a fuel injection nozzle, A method for adjusting the amount of fuel injection, and a method for adjusting the pressure in a fuel injection pump, and
One idea is to supply a metered amount of fuel, but the latter is advantageous in that the structure of the fuel injection pump can be simplified and it can be made smaller.

In an engine fuel injection system that employs a method in which a pressure-regulated and metered amount of fuel is supplied to the fuel injection pump, the fuel injection pump has a pump chamber and an inlet passage that introduces fuel from a filter into the pump chamber. and an inlet valve that opens and closes this inlet passage. In addition, the inlet valve only needs to prevent backflow from the fuel injection pump, so
It is usually composed of a check valve.

However, when the inlet valve is configured with a check valve in this way, the stroke of the plunger rising from the bottom dead center (rising stroke) varies depending on the amount of fuel supplied to the fuel injection pump. In a partially loaded state, there is a gap between the plunger and the drive mechanism that drives it, or between parts within the drive mechanism, resulting in the sound of the drive mechanism hitting the plunger or the sounds of parts hitting each other in the drive mechanism. There is a problem that occurs.

In order to prevent such operational noise, a technique is already known in which a spring is interposed between the plunger and the drive mechanism or each component within the drive mechanism.
In this case, there is a drawback that the control accuracy of the fuel injection timing is impaired due to the vibration of the spring.

<Preliminary Design 1> Therefore, in order to prevent the occurrence of such operational noise without impairing the control accuracy of the fuel injection timing, the present inventor proposed, for example, FIGS. 7A to 7D.
As shown in FIG. 2, the inlet valve 7 of the fuel injection pump 3 is configured with a check valve set to a predetermined valve closing pressure, for example, the lowest discharge pressure of the fuel injection pump 3.
Prior to the present invention, an engine fuel injection device (hereinafter referred to as the first prior invention) was developed, in which an injection amount adjustment pressure accumulation chamber 9 whose volume change amount is equal to the maximum injection amount is connected to the inlet passage 6 on the upstream side of the engine. It was devised.

According to the first prior invention, as shown in FIG. 7A, the plunger 10 of the fuel injection pump 3 is raised (retracted) the most within the pump chamber 5, and the pressure accumulation chamber 9 for adjusting the injection amount is contracted the most. In this state, fuel is supplied from the fuel supply device 1. As shown in FIG. 7B, the supplied fuel is first pressurized into the injection amount adjustment pressure accumulation chamber 9, and then, as the plunger 10 is lowered, the fuel in the pump chamber 5 increases the injection amount adjustment pressure accumulation chamber 9. Room 9
be pushed into. As shown in FIG. 7C, when an amount of fuel Vcom equal to the difference between the maximum injection amount Vmax and the fuel supply amount Vsup is pushed from the pump chamber 5 into the injection amount adjustment pressure storage chamber 9, the injection amount adjustment pressure storage chamber 9
is expanded to the maximum volume Vmax. After this, when the plunger 10 is lowered, the internal pressure of the pump chamber 5 rises above the set pressure of the inlet valve 7, the inlet valve 7 is closed, the pressure rises, and discharge begins. The discharge of the fuel injection pump 3 continues until the plunger 10 descends to the bottom dead center and the volume of the pump chamber 5 becomes minimum, as shown in FIG. 7D. That is, the downward stroke of the plunger 10 from FIG. 7B to FIG. 7C is an invalid stroke without fuel discharge, and the downward stroke of the plunger 10 from FIG. 7C to FIG. 7D is This is an effective stroke accompanied by fuel discharge. Thereafter, when the plunger 10 moves up, fuel is pressurized into the pump chamber 5 from the injection amount adjustment pressure accumulation chamber 9. This pressure causes the plunger 10 to rise to its full stroke while being pressed against a drive mechanism (not shown).
In this way, when an amount of fuel equal to the maximum injection amount Vmax is pressurized from the injection amount adjustment pressure accumulation chamber 9 into the pump chamber 5, the initial state shown in FIG. 7A is returned. Therefore, the amount of rise of the plunger 10 is always a full stroke, and gaps are prevented from forming between the plunger 10 and the drive device or between the parts that make up the drive device, and the above-mentioned operation noise is prevented from occurring. That will happen. Further, since no gap is generated inside the drive mechanism or between it and the plunger 10, the fuel injection timing can be accurately controlled.

However, in the engine fuel injection device according to the prior invention, during high-speed operation, the fuel flowing back from the pump chamber 5 to the filter 2 side during the invalid stroke of the plunger 10 is throttled by the inlet valve 7, and the inlet valve 7 is It was found that a difference in internal pressure occurred between the inlet side (filter side) and the outlet side (pump chamber side), and that this pressure difference caused the valve to close earlier, causing an error in the fuel injection amount that tended to increase. .

<Preliminary Design 2> Therefore, as a result of further intensive research, the present inventors came to devise an engine fuel injection device (hereinafter referred to as the second prior design) configured as follows. .

That is, in this second prior design, as shown in FIG. 1 in the first prior design, the inlet valve 7 of the fuel injection pump 3 is configured with a cutoff valve consisting of a spool valve instead of a check valve. , this inlet valve 7 is provided with a valve opening biasing means 13 at one end of a spool chamber 12 that accommodates the spool 11 to bias the spool 11 to the open position, and the spool 1 is disposed at the other end of the spool chamber 12.
1 is provided, and the injection amount adjustment pressure accumulation chamber 9 and the pump chamber 5 are connected to the spool valve hole 14 of the inlet valve 7, the port 15,
15a and 15b, and the spool valve hole 14 and the port 1 are connected to each other through the pump chamber 5 and the spool valve hole 14 when the accumulated pressure volume of the injection quantity adjustment pressure accumulation chamber 9 becomes equal to the maximum injection quantity.
They devised a fuel injection device for an engine configured such that the inlet valve 7 is closed when communication with the inlet valves 5, 15a, and 15b is cut off.

According to this engine fuel injection device, fuel flows from the pump chamber 5 into the injection amount adjustment pressure accumulation chamber 9 during the invalid stroke of the plunger 10 of the fuel injection pump 3, and the pressure accumulation volume of the injection amount adjustment pressure accumulation chamber 9 increases. The inlet valve 7 is closed at the end of the invalid stroke which is equal to the maximum injection quantity. Therefore, the position of the spool 11 of the inlet valve 7 is determined regardless of the differential pressure generated between the upstream side and the downstream side of the inlet valve 7.
The amount of fuel trapped in the pump chamber 5 when the inlet valve 7 is closed can be controlled to be exactly equal to the fuel injection amount.

<Problems to be solved by the invention> However, in the second prior invention configured as described above, when the inlet valve 7 is closed, the inlet passage 6 is closed.
The flow of fuel flowing through the inlet valve 7 is suddenly blocked by the inlet valve 7, and in the same manner as the intake pulsation, the fuel supply from the inlet valve 7 including the inlet passage 6 leading from the inlet valve 7 to the filter 2 on the upstream side is interrupted. It has been found that pulsations as shown by line a in FIG. 6A occur in the fuel in the fuel passage 23 leading to the device 1. Such pulsation causes the position of the spool 9 to fluctuate as shown by line a in FIG. The spool 11 is pushed up to the top dead center before the injection amount is pressurized into the pressure accumulation chamber 9 for adjusting the injection amount, and the closing timing of the inlet valve 7 is advanced. The closing timing of the inlet valve 7 may be delayed by not pushing the spool 11 up to the top dead center until a larger amount of fuel than the amount Vcom equal to the difference is pressurized into the pressure accumulation chamber 9 for adjusting the injection amount. There is a possibility that the inlet valve 7, which was once closed, may be opened, causing an error in the control of the fuel injection amount.

The present invention has been developed in consideration of the above circumstances, and is designed to reduce the impact noise caused by the drive unit hitting the plunger of the fuel injection pump during partial load in the engine fuel injection system having the above-mentioned prerequisite configuration. An object of the present invention is to provide a fuel injection device for an engine, which can prevent the occurrence of impact noises of parts hitting each other, achieve quieter operation, and improve control accuracy of fuel injection amount. That is.

<Means for Solving the Problems> In order to achieve the above object, the engine fuel injection device according to the present invention has an engine having the above-mentioned prerequisite configuration, as shown in FIGS. In the fuel injection device, the inlet valve 7 is constituted by a spool valve, and the spool 11 is disposed at one end side of a spool chamber 12 that accommodates the spool 11 of the inlet valve 7.
A valve opening biasing means 13 is provided for biasing the valve to the valve opening position, while a spool 11 is provided at the other end of the spool chamber 12.
A spool valve passage 14 is formed in the spool 11, and ports 15, 15 are opened in the peripheral wall of the spool chamber 12.
a, 15b, and the inlet valve 7 communicates with the pump chamber 5 through the fuel injection amount adjustment pressure accumulation chamber 9.
The spool valve passage 14 and the ports 15, 15a, 15b are shut off and closed when the accumulated pressure volume of the fuel becomes equal to the maximum injection amount, and the fuel flowing from the fuel supply device 1 to the inlet valve 7 is Passage 23
A technical measure is taken to interpose a check valve 40 in the middle.

The fuel supply device is not particularly limited as long as it is configured to supply fuel at a predetermined pressure according to the load condition of the engine. For example, there is a fuel tank, a fuel pump that pumps fuel out of it, a pressure regulator that controls the pressure of the fuel discharged from the fuel pump to a predetermined supply pressure, and a pressure regulator that controls the regulated fuel supply amount to the engine load. It is possible to employ a fuel injection system connected in series with a correspondingly regulating metering device. Note that the predetermined supply pressure regulated by the pressure regulating device is not limited to a constant case, but is determined by adjusting the engine's supply pressure to correct the non-linear control characteristic of the metering device to the rotational speed into a linear control characteristic. This also includes a case where it is changed in response to the engine speed, for example, a case where it is set to increase or decrease in response to an increase or decrease in the engine speed.

The filter only needs to have the function of removing foreign substances from the fuel supplied from the fuel supply device, but
It is preferable to use a filter having high pressure resistance, such as an edge filter or a notch wire filter.

The fuel injection pump and the filter can be formed separately from each other and connected through piping, but it is also possible to assemble them into one piece. When these are assembled together, it is advantageous because the whole can be made smaller and more compact.

Fuel injection pumps are comprised of plunger pumps without exception. Here, the fuel injection pump has a pump chamber, an inlet passage that introduces fuel from a filter into the pump chamber, and an inlet valve that opens and closes this inlet passage, and one end of the spool chamber that accommodates the spool of the inlet valve. A valve-opening biasing means for biasing the spool to the valve-opening position is provided, and a fuel injection amount adjustment pressure accumulation chamber is formed at the other end of the spool chamber and partitioned by the spool. The chamber is communicated with the pump chamber through a spool valve passage formed in the spool and a port opened in the peripheral wall of the spool chamber, and the inlet valve is connected to the pump chamber through a spool valve passage formed in the spool and a port opened in the peripheral wall of the spool chamber. The spool valve passage and the port are cut off and the valve is closed when the value becomes equal to .

The inlet valve may be formed separately from the pump chamber and the plunger, but as will be described later, by incorporating the spool chamber, at least a portion of the valve opening biasing means, and the fuel injection amount adjustment pressure accumulation chamber inside the plunger, It is possible to achieve miniaturization and compactness.

The inlet valve of the fuel injection pump can also be provided outside the pump chamber and plunger, and
It is also possible to incorporate it inside the plunger. When built into the plunger, there is an advantage that the fuel injection pump can be made smaller and more compact.

The type of fuel injector is not particularly limited, and may have an open nozzle or a closed nozzle. Fuel injectors with a closing nozzle include mechanical valve type in which the nozzle valve is controlled to open and close by a mechanical device, automatic valve type in which the nozzle valve is controlled to open and close by the pressure of the fuel supplied to the nozzle, and nozzle valve in electromagnetic type. A solenoid valve type, etc., which is controlled to open and close by an actuator, can be adopted. Among the automatic valve types, there are those that open when the pressure of the fuel supplied to the fuel injector exceeds a certain level, so to speak, and those that open under pressure, and those that accumulate pressure in a portion of the fuel supplied to the fuel injector. This also includes a so-called pressure-reduction valve opening type, in which the remaining portion is sucked out to the outside to generate a pressure difference, and the valve opens when this pressure difference exceeds a certain level. However, although the electromagnetic valve type is suitable for injecting fuel into the intake passage, it is not suitable for engines that require high-pressure injection such as diesel engines. Among these fuel injectors, those having a closed nozzle with good injection shut-off are recommended, and in particular, those having an automatic valve with a simple nozzle valve driving device configuration and miniaturization are recommended. Among the automatic valve types, a reduced pressure valve opening type is particularly recommended because it can easily control the degree of opening of the injection valve by changing the amount of fuel sucked out over time.

Although it is possible to form the fuel injector and fuel injection pump separately and connect them with piping, assembling them together allows for a smaller overall size. This is advantageous because the fuel injection pressure can be increased while minimizing the pressure drop between the pump and the pump.

The connection method between the fuel injection pump and the fuel injector is not particularly limited, and known connection methods such as an independent pump type, distribution type, pressure accumulation distribution type, or pressure accumulation type can be adopted. In addition, in a pressure accumulation type fuel injection device in which a pressure accumulation chamber is provided between the fuel injection pump and the injection nozzle of the fuel injector, when the above-mentioned pressure reducing valve opening type injector is adopted, the fuel injection pump and the injection nozzle are A pressure reducing chamber for opening the valve, a check valve, and a pressure accumulating chamber are connected in series in order in the high pressure fuel supply path connecting the The injection valve of the injection nozzle is configured to open the injection valve when the differential pressure between the internal pressure of the pressure accumulation chamber and the internal pressure of the valve-opening pressure reduction chamber overcomes the valve-closing force of the valve-closing means. be done. In this case, it is possible to make the pressure reduction in the valve-opening pressure-reducing chamber depend on the rise of the plunger, but it is also possible to make the pressure reduction in the valve-opening pressure-reducing chamber by sucking out fuel from the outside while holding the plunger at the bottom dead center. It is also possible to configure In this case, it is easier to control the reduced pressure state of the pressure reducing chamber for valve opening than when the rising speed of the plunger is controlled by a cam etc. By applying this method to the invention, the injection amount at the initial stage of opening of the injection valve is limited to a small amount, and a large amount of fuel is injected after ignition, thereby making it possible to reduce the explosion noise at the time of ignition.

The check valve may be provided anywhere along the fuel passage from the fuel supply device to the inlet valve of the fuel injection pump. However, in order to prevent fuel pulsation on the upstream side of the inlet valve, it is advantageous to provide it as close to the inlet valve as possible; for example, it is advantageous to provide it in a portion of the inlet passage closer to the filter than the inlet valve. . Moreover, in order to achieve compactness, it is advantageous to incorporate it into the filter.

<Operation of the invention> As described above, in the engine fuel injection device according to the invention, the inlet valve of the fuel injection pump is composed of a spool valve, and the spool is disposed at one end side of the spool chamber that accommodates the spool of the inlet valve. A valve opening biasing means for biasing the valve to the open position is provided, and a fuel injection amount adjustment pressure accumulation chamber is formed at the other end of the spool chamber and partitioned by a spool, and this fuel injection amount adjustment pressure accumulation chamber is provided. The spool valve passage formed in the spool communicates with the pump chamber via a port opened in the peripheral wall of the spool chamber, and when the accumulated pressure volume of the pressure accumulation chamber for adjusting the fuel injection amount becomes equal to the maximum injection amount, the spool valve Since the passage and the port are configured to be shut off, when the inlet valve closes, an amount of fuel equal to the maximum injection amount is accumulated in the fuel injection amount adjustment pressure accumulation chamber, and after this, the fuel injection pump When the plunger rises, an amount of fuel equal to the maximum injection amount is forced into the pump chamber from the fuel injection amount adjustment pressure accumulation chamber, and the plunger can be raised to the top dead center while being pressed against the drive mechanism side. This prevents gaps from forming between the plunger and the drive mechanism that drives it, or between parts within the drive mechanism, which may occur due to the parts of the drive mechanism hitting each other or the drive mechanism hitting the plunger. The generation of driving noise can be prevented.

Further, according to the present invention, with the above configuration, by supplying fuel from the fuel supply device with the plunger positioned at the top dead center, the fuel injection amount adjustment pressure accumulation chamber is supplied with fuel. Fuel is pressurized, and while the plunger is moving down the invalid stroke, an amount of fuel equal to the difference between the maximum injection amount and the supplied fuel amount is supplied from the pump chamber to the fuel injection amount adjustment pressure accumulation chamber, and the fuel injection amount adjustment Since the spool valve passage and the port are configured to be shut off when the pressure accumulation volume of the pressure accumulation chamber becomes equal to the maximum injection amount,
The amount of fuel discharged from the pump chamber during the effective stroke of the plunger becomes equal to the fuel supply amount, regardless of the pressure difference between the pump chamber and the fuel injection amount adjustment pressure storage chamber during the ineffective stroke. Furthermore, since a check valve is interposed in the fuel passage from the fuel supply device to the inlet valve, when the inlet valve is closed, the flow of fuel that is bounced back from the inlet valve to the upstream side of the inlet valve is blocked by the check valve. This prevents pulsations occurring upstream of the inlet valve. Therefore, the reduction in the internal pressure of the fuel injection amount adjustment pressure accumulation chamber due to the fuel pulsations on the upstream side of the inlet valve is alleviated or eliminated, and the once-closed inlet valve is erroneously opened due to such fuel pulsations. This prevents and,
As mentioned above, the synergistic effect of the inlet valve being closed depending on the pressure accumulation volume of the pressure accumulation chamber for fuel injection amount adjustment and the prevention of fuel pulsation by the check valve allows for extremely accurate control. This allows the injection amount to be controlled.

<Effects of the invention> As described above, according to the invention, when the plunger descends, the amount of fuel obtained by subtracting the supply amount from the maximum injection amount is caused to flow backward into the fuel injection amount adjustment pressure accumulation chamber, thereby creating the fuel injection amount adjustment pressure accumulation chamber. The pressure accumulation volume in the chamber is increased to a volume equal to the maximum injection amount, and when the plunger rises, a volume of fuel equal to the maximum injection amount is injected into the pump chamber, so that the plunger always reaches top dead center regardless of the load state. Since it is configured to raise
It is possible to prevent gaps from forming between the plunger and the drive mechanism that drives it, or between parts within the drive mechanism, and reduce operational noise caused by parts of the drive mechanism hitting each other or the drive mechanism hitting the plunger. Occurrence can be prevented.

In addition, the inlet valve of the fuel injection pump is configured with a spool valve, and the pressure accumulation for fuel injection amount adjustment biases the spool to close regardless of the pressure difference between the pump chamber and the pressure accumulation chamber for fuel injection amount adjustment during the invalid stroke. the inlet valve is closed depending on the pressure accumulation volume of the chamber so that the amount of fuel discharged from the pump chamber during the effective stroke of the plunger is exactly equal to the fuel supply amount;
Since a check valve is interposed in the middle of the fuel passage from the fuel supply device to the inlet valve, closing the inlet valve suppresses the pulsation of fuel that occurs upstream of the inlet valve, and once the inlet valve is closed, Since the valve is prevented from being erroneously opened due to such fuel pulsations, the accuracy of injection amount control can be extremely high.

<Example 1> Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a vertical cross-sectional view of a unit injector of a diesel engine fuel injection device according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view taken along the - line in FIG. 1, and FIG. FIG. 4 is a schematic diagram showing the operation of the fuel injection pump, FIG. 5 is a timing chart showing the operation of the unit injector, and FIG. 6A is a fuel system diagram of the fuel injection device. It is a pressure-time relationship diagram illustrating changes over time in the pressure, the internal pressure of the pressure accumulation chamber for adjusting the fuel injection amount, and the internal pressure of the bias chamber as the valve opening biasing means,
FIG. 6B is a spool position-time relationship diagram showing the position of the spool of the inlet valve in comparison with that of the second prior invention.

This fuel injection device includes a fuel supply device 1, a filter 2, a fuel injection pump 3, a fuel injector 4,
and an injection timing control device 16.

The fuel supply device 1 uses a fuel pump 18 to pump fuel from a fuel tank 17 that stores fuel, and uses a pressure regulator 19 to increase or decrease the pressure of the fuel discharged from the fuel pump 18 in proportion to an increase or decrease in engine speed. Furthermore, the amount of fuel supplied is increased or decreased by the metering device 20 in accordance with the magnitude of the engine load, and the pressure regulated and metered fuel is pressurized by the press pump 21 to provide fuel. It is configured to be supplied to the injection pump 3 side. Here, the reason why the pressure regulating device 19 adjusts the fuel supply pressure to increase or decrease in accordance with the increase or decrease in the engine speed is because the control characteristic of the metering device 20 with respect to the rotation speed is non-linear. This is to correct the control characteristic of the fuel injection amount with respect to the rotational speed to a linear control characteristic. The press-in pump 21 is constituted by a plunger pump, and is driven by a cam 22 that rotates in synchronization with the engine.

The filter 2 is interposed in a fuel passage 23 connecting the fuel supply device 1 and the fuel injection pump 3, and is constituted by an edge filter having high pressure resistance and a simple structure.

The fuel injection pump 3 is constituted by a plunger pump, and includes a pump chamber 5, a plunger 10 that can be moved up and down into the pump chamber 5, an inlet passage 6 that connects the pump chamber 5 and the filter 2, and this inlet passage. 6, and an injection amount adjustment pressure accumulation chamber 9 branched and connected to the inlet passage 6 on the upstream side of the inlet valve 7.

The inlet valve 7 is composed of a spool valve, and includes a spool chamber 12 formed in a cylindrical shape coaxially with the plunger 10, and a spool 11 inserted into the spool chamber 12 so as to be slidable up and down. .
The inlet valve 7 also includes a pressure receiving chamber 13a for valve opening biasing which is partitioned by the spool 11 at the upper end of the spool chamber 12.
A and a valve opening biasing pressure accumulating chamber 13b communicating with the valve opening biasing means 13 are provided. At the lower end of the spool chamber 12, a pressure accumulation chamber 9 for adjusting the injection amount is defined by the spool 11. It can communicate with the pump chamber 5 via 15.
Communication between the spool valve hole 14 and the port 15 is as follows:
It is designed to be shut off when the spool 11 reaches the top dead center and the pressure accumulation volume of the injection amount adjustment pressure accumulation chamber 9 becomes equal to the maximum injection amount. Here, in order to keep the opening amount of the injection valve 25 small at the beginning of injection, the port 15 has a micro port 15 with a micro hole diameter that communicates with the spool valve hole 14 when the inlet valve 7 starts opening.
a, and a large-diameter main port 15 that communicates with the spool valve hole 14 when the spool 11 is positioned further lower.
It is composed of b.

The valve opening biasing means 13 is operated via a bias spool valve hole 48 formed in the spool 11 and a bias port 49 formed in the peripheral wall of the plunger 10 when the spool 11 is located at the top dead center and when the spool 11 is located at the bottom dead center. When the spool 11 is located at a point, the spool 11 is communicated with the inlet passage 6, and the pressure of the fuel sealed therein urges the spool 11 in the valve opening direction.

The fuel injector 4 is composed of an automatic valve type nozzle that opens and opens by pressure reduction, and includes an injection nozzle 24, an injection valve 25 that opens and closes the injection nozzle, a pressure reduction chamber 26 for valve opening, and an injection pressure accumulation chamber 2.
7, a check valve 31, and an injection valve closing spring 37. The injection pressure accumulation chamber 27 includes a first pressure accumulation chamber 28 having a relatively small volume and a second pressure accumulation chamber 29 having a relatively large volume.

The valve-opening pressure reducing chamber 26 and the first pressure accumulating chamber 28 are formed vertically in series around the valve handle 30 of the injection valve 25, and a connecting portion between the valve-opening pressure reducing chamber 26 and the first pressure accumulating chamber 28 is formed. The valve body 32 of the check valve 31 is fitted inside so as to be slidable up and down.

The valve opening pressure reduction chamber 26 is connected to the fuel supply device 1 and the injection timing control device 16 via the fuel injection pump 3 and a filter.

The valve seat 33 of the check valve 31 is formed by enlarging a portion of the valve stem 30 of the injection valve 25, and a valve body 32 is pressed against the lower surface of the valve seat 33 by a valve closing spring 34.

The first pressure accumulation chamber 28 and the second pressure accumulation chamber 29 have a check valve 35 that opens when the internal pressure of the former reaches a high pressure of 700 to 1000 atmospheres and allows fuel to flow from the former to the latter, and a check valve 35 of the latter. High pressure with internal pressure above a certain level, e.g.
It is connected via a pressure setting valve 36 that opens only when the pressure exceeds 700 atmospheres.

The injection valve closing spring 37 is housed in a valve closing spring chamber above the valve opening pressure reducing chamber 26, and is configured to normally bias the injection valve 25 in the valve closing direction. The valve-closing spring chamber is also used as the valve-opening pressure accumulating chamber 13b.

The injection timing control device 16 controls the fuel sucked out from the valve-opening pressure reducing chamber 26 at a predetermined timing (between time g and time k in FIG. 5) after the injection of fuel into the fuel injector 4 is completed. Fuel breathing chamber 38
(from time k to time n in Fig. 5), and then after the fuel injection is completed, plunger 1
After the start of the rise of 0 (time point m in Figure 5),
In order to return the amount of fuel in the decompression chamber 26 for valve opening of the fuel injection pump 3 and fuel injector 4 to the initial state, from the timing immediately before the spool 11 returns to the bottom dead center (time n in FIG. 5). It is configured to return the fuel confined in the fuel breathing chamber 38 to the pressure reducing chamber 26 for opening the valves of the fuel injection pump 3 and fuel injector 4 via the filter 2 at a pressure slightly higher than the reference pressure Po in the initial state. .

The timing of supplying fuel from the fuel supply device 1 to the fuel injection pump 3, the timing of releasing pressure to the decompression chamber 26 for opening the valve, and the timing of spitting back fuel from the fuel breathing chamber 38 are determined on the upstream side of the filter 2. The engine rotation is controlled in synchronization with the rotation of the engine by a combined control valve device 39.

Furthermore, in this diesel engine fuel injection system, a check valve 40 is interposed in the fuel passage 23 leading from the fuel supply system 1 to the inlet valve 7 of the fuel injection pump 3 to prevent backflow from the latter to the former. Specifically, this check valve 40 is provided inside the filter element 41 of the filter 2. That is, a valve hole 42 with one end (lower end in this case) open to the upstream side is formed inside the filter element 3, and the back half of the valve hole 42 is made larger in diameter than the open half to prevent backlash. A valve chamber 43 is formed, and a valve seat 44 is formed at a portion with a different diameter, and the check valve chamber 43 is communicated with a primary chamber 45 of the filter 2 . Further, the check valve chamber 43 accommodates a ball-shaped check valve body 46 and a valve closing spring 47 that biases the ball-shaped check valve body 46 to close the valve.
In addition, as mentioned above, the pressure reducing chamber 2 for opening the valve of the fuel injector 4
In order to allow pressure relief from 6, filter 2
The primary chamber 44 and the opening side half of the valve hole 41 are communicated through a small hole 50.

In addition, in the above embodiment, the filter 2, the fuel injection pump 3, and the fuel injector 4 are
Although they are assembled together as a unit injector U, it is not essential in the present invention that they be assembled together.

Next, the main operations of this diesel engine fuel injection system will be explained.

The fuel supply device 1 regulates the pressure of the fuel pumped out from the fuel tank 17 with a pressure regulating device 18,
The amount of fuel is measured by the press-in pump 21, and the fuel is discharged at a predetermined timing synchronized with the engine speed. The timing of the fuel discharged from the press-in pump 21 is more precisely controlled by the composite control valve device 39.

The fuel supply to the fuel injection pump 3 is as shown in Fig. 4A.
As shown in FIG. 5, the process starts with the plunger 10 located at the top dead center and the spool 11 located at the bottom dead center (point a in FIG. 5). Fuel is pressurized into the pressure accumulation chamber 9 for adjusting the injection amount, and when the supply of fuel from the fuel supply device 1 is finished (point b in Fig. 5), the spool 11 is positioned at a height corresponding to the magnitude of the load. It will be done. That is, when the maximum injection amount Vmax of fuel corresponding to the maximum load is supplied, the spool 11 is positioned at the top dead center, and when the amount of fuel corresponding to the partial load is supplied, the spool 11 is positioned at the top dead center, and when the fuel amount corresponding to the partial load is supplied, the spool 11 is positioned at the top dead center. The spool 11 is positioned at a lower intermediate height as shown in FIG. The descent of the plunger 10 starts after the end of the fuel supply from the fuel supply device 1 (point c in FIG. 5), and as the plunger 10 descends, the fuel in the pump chamber 5 is transferred to the port 15 and the spool valve. It is pushed through the hole 14 into the pressure accumulation chamber 9 for adjusting the injection amount.
The maximum injection amount Vmax and the fuel supply amount from the fuel supply device 1 are transferred from the pump chamber 5 to the pressure accumulation chamber 9 for adjusting the injection amount.
When an amount of fuel Vcom equal to the difference from Vsup is injected (at point d in Figure 5), the injection amount adjustment pressure accumulator 9
Since the accumulated pressure volume becomes equal to the maximum injection amount Vmax, the spool 11 reaches the top dead center as shown in FIG. be done. The plunger 11 is further pushed down to the bottom dead center as shown in FIG. 4D (from time d to f in FIG. 5),
During this time, an amount of fuel equal to the fuel supply amount Vsup is discharged from the pump chamber 5 to the fuel injector 4.

Here, if the check valve 40 is not interposed in the fuel passage 23, the flow of fuel flowing toward the inlet valve 7 on the upstream side of the inlet valve 7 will be rebound by the closing of the inlet valve 7, and furthermore, the The process of the fuel flow returning to the control valve device 39 being bounced back by the composite control valve device 39 is repeated, resulting in fuel pulsation. This pulsation becomes larger as the distance over which the fuel can reciprocate is longer, and it fluctuates the internal pressure of the pressure accumulation chamber 9 for adjusting the injection amount of the inlet valve 7, thereby increasing the spool 1.
The position of 1 will be changed. Therefore, such pulsation is caused by, for example, an amount equal to the difference between the maximum injection amount Vmax and the fuel supply amount Vsup from the pump chamber 5.
Before the fuel of Vcom is pressurized into the pressure accumulation chamber 9 for adjusting the injection amount, the spool 11 is pushed up to the top dead center to advance the closing timing of the inlet valve 7.
The inlet valve 7 is closed without pushing the spool 11 up to the top dead center until a larger amount of fuel than the amount Vcom equal to the difference between the maximum injection amount Vmax and the fuel supply amount Vsup is pressurized into the injection amount adjustment pressure accumulation chamber 9. This may cause an error in the control of the fuel injection amount by delaying the valve timing or, in some cases, opening the inlet valve 7 that was once closed.

In this diesel engine fuel injection system,
A check valve 40 is interposed in the fuel passage 23, and this check valve 40 is connected to the unit injector U.
Since the filter element 41 is installed adjacent to the inlet valve 7 in the filter element 41, the section where such pulsation occurs is a very short section divided by the inlet valve 7 and the check valve 40. As shown by the line b in FIG. 6A, there is almost no pulsation in the internal pressure of the pressure accumulation chamber 9 for adjusting the injection amount, and the position of the spool 11 is accurate as shown by the line b in FIG. 6B. This allows extremely accurate fuel injection amount control.

Note that in the fuel injector 4, the fuel injection pump 3
When fuel is pressurized from the valve opening chamber 2,
6 and the check valve 31, fuel is pressurized into the first pressure accumulation chamber 28 (from time d to time e in FIG. 5),
Furthermore, the injection amount is large and the internal pressure of the first pressure accumulating chamber 28 opens the check valve 35, and fuel is also pressurized into the second pressure accumulating chamber 29 (from time e to f in FIG. 5).
When the check valve 35 is opened, the internal pressure of the second pressure accumulating chamber 29 exceeds the internal pressure of the pressure setting valve 36, and the pressure setting valve 36 is opened, so that the internal pressure of the first pressure accumulating chamber 28 and the second pressure accumulating chamber 29 are The internal pressure will be the same. As a result, the check valve 35 is closed immediately after opening. Further, when the injection timing control device 16 starts depressurizing the valve-opening pressure reducing chamber 26 (time point g in FIG. 5), first, the inlet passage 6 of the fuel injection pump 3 and the injection amount adjustment pressure accumulating chamber are 9 is released to the injection timing control device 16 (from time point g to time h in FIG. 5), and when the spool 11 begins to descend from top dead center (time point h in FIG. 5), the inlet valve 7 is opened, and the fuel in the pump chamber 5 and the valve-opening pressure reduction chamber 26 is released to the injection timing control device 16 (from time h to time k in FIG. 5). In this way, the pressure relief of the valve-opening pressure reducing chamber 26 is started, and when the internal pressure of the valve-opening pressure reducing chamber 26 drops to the predetermined injection valve opening pressure (time point i in FIG. 5), the injection valve 25 opens. Starts to be praised. At the beginning of the opening period of the injection valve 25 (from time point i to time point j in FIG. 5), the opening area of the inlet valve 7 is narrowed to the minute area of the minute port 15a, so that the pressure reduction chamber 26 for opening the valve is closed. The rate of change in internal pressure is kept small, and the opening amount of the injection valve 25 is also kept small. After a predetermined period of time elapses after the valve starts opening, the fuel injected into the combustion chamber is ignited, and the spool valve hole 14 of the inlet valve 7 and the main port 15b are connected to the ignition timing (point j in Fig. 5). is opened, the internal pressure of the valve-opening pressure reducing chamber 26 is rapidly reduced, and the injection valve 25 is fully opened. As a result, a large amount of high-pressure fuel is injected all at once. The internal pressure of the injection pressure accumulation chamber 27 is adjusted to the pressure setting part 36 by fuel injection.
When the pressure decreases to the set pressure (point k in FIG. 5), the pressure setting section 36 is closed and fuel having an internal pressure higher than the set pressure of the pressure setting section 36 is confined in the second pressure accumulating chamber 29. . After this, the fuel in the small volume first pressure accumulation chamber 28 is injected, so
The internal pressure of the first pressure accumulating chamber 28 drops rapidly, and the differential pressure between the internal pressure of the valve opening pressure reducing chamber 26 and the first pressure accumulating chamber 28 decreases in a short time, and the injection closing valve spring 37 causes the injection Valve 25 is closed (point l in FIG. 5).
The plunger 10 starts to rise at a predetermined timing after the injection valve 25 is closed (time point m in FIG. 5), and as the plunger 10 rises, the injection amount adjustment pressure accumulation chamber 9 and the pump chamber 6 The internal pressure of the valve opening pressure reducing chamber 26 further drops, the spool 11 is lowered by the valve opening biasing means 13, and fuel is transferred from the injection amount adjustment pressure accumulation chamber 9 to the pump chamber 6 and the valve opening pressure reducing chamber 26. will flow in. Pressure accumulation chamber 9 for adjusting injection amount;
The amount of fuel stored in the pump chamber 6 and the valve opening pressure reduction chamber 26 is smaller than the initial state by the amount released by the injection timing control device 16, but this amount of fuel is not stored in the spool. The fuel trapped in the fuel breathing chamber 38 is initially pumped for a predetermined period (from time n to time o in FIG. 5) from the timing immediately before the 11 returns to the bottom dead center (time n in FIG. 5). The pressure is restored by returning the pressure to the valve-opening pressure reducing chamber 26 of the fuel injection pump 3 and fuel injector 4 via the filter 2 at a pressure slightly higher than the current reference pressure Po.

As described above, according to the fuel injection device of this engine, when the plunger 10 descends, the fuel injection amount adjustment pressure accumulation chamber 9 is supplied with a supply amount from the maximum injection amount Vmax.
The fuel of the amount Vcom obtained by subtracting Vsup is caused to flow backward to increase the pressure accumulation volume of the fuel injection amount adjustment pressure accumulation chamber 9 to a volume equal to the maximum injection amount Vmax, and when the plunger 10 rises, the fuel injection amount adjustment pressure accumulation chamber 9 Since the configuration is such that a volume of fuel equal to the maximum injection amount Vmax is injected into the pump chamber 5 from 1 to 5, and the plunger 10 is always raised to the top dead center regardless of the load condition, the plunger 10 and this are driven. It is possible to prevent gaps from being generated between the drive mechanisms or between parts within the drive mechanism, and to prevent operation noise caused by the parts of the drive mechanism hitting each other or the drive mechanism hitting the plunger 10.

In addition, the inlet valve 7 of the fuel injection pump 3 is configured with a spool valve, and the pump chamber 5 during the invalid stroke
The inlet valve 7 is closed depending on the pressure accumulation volume of the fuel injection amount adjustment pressure accumulation chamber 9 which biases the spool 11 to close, regardless of the pressure difference between the fuel injection amount adjustment pressure storage chamber 9 and the fuel injection amount adjustment pressure accumulation chamber 9. While the amount of fuel discharged from the pump chamber 5 during the effective stroke of 10 is made exactly equal to the fuel supply amount Vsup, a check valve 40 is interposed in the middle of the fuel passage from the fuel supply device 1 to the inlet valve 7. Therefore, by closing the inlet valve 7, the pulsation of fuel generated upstream of the inlet valve 7 is suppressed, and the inlet valve 7, which is once closed, is prevented from being closed at the wrong timing due to such pulsation of the fuel. This prevents the inlet valve 7, which has been once closed, from opening at the wrong timing, making it possible to extremely increase the control accuracy of injection amount control.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a unit injector of a diesel engine fuel injection device according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view taken along the line -- in FIG.
Figure 3 is a fuel system diagram of the fuel injection device, Figure 4 is a schematic diagram showing the operation of the fuel injection pump, and Figure 5 is a schematic diagram showing the operation of the fuel injection pump.
The figure is a timing diagram showing the operation of the unit injector, and Figure 6A is a pressure diagram illustrating changes over time in the fuel supply pressure, the internal pressure of the pressure accumulation chamber for adjusting the fuel injection amount, and the internal pressure of the bias chamber as the valve opening biasing means. A time relationship diagram, FIG. 6B is a spool position-time relationship diagram showing the position of the inlet valve spool in comparison with that of the second prior design, and FIG. 7 is a diagram showing the operation of the fuel injection pump of the first prior design. FIG. 1...Fuel supply device, 2...Filter, 3...
Fuel injection pump, 4...Fuel injector, 5...Pump chamber, 6...Inlet passage, 7...Inlet valve, 9...Injection amount adjustment pressure accumulation chamber, 10...Plunger, 11...
...Spool, 12...Spool chamber, 13...Valve opening biasing means, 14...Spool valve hole, 15...Port, 15a...Minute port, 15b...Main port, 23...Fuel passage, 40... …non-return valve.

Claims (1)

[Claims for Utility Model Registration] 1. A fuel supply device 1 that supplies a metered amount of fuel at a predetermined pressure in accordance with the load condition of the engine, and a filter 2 that removes foreign substances from the fuel supplied from the fuel supply device 1. , a fuel injection pump 3 that presses fuel supplied from a fuel supply device 1 and from which foreign matter has been removed by a filter 2 into a fuel injector 4; and a fuel injector 4, the fuel injection pump 3 having a pump chamber 5; In an engine fuel injection device having an inlet passage 6 that introduces fuel from the filter 2 into the pump chamber 5 and an inlet valve 7 that opens and closes this inlet passage 6, the inlet valve 7 is constituted by a spool valve, and the inlet valve 7 A valve-opening biasing means 13 for biasing the spool 11 to the valve-opening position is provided at one end of the spool chamber 12 that accommodates the spool 11, while a fuel partitioned by the spool 11 is provided at the other end of the spool chamber 12. Forming a pressure accumulation chamber 9 for adjusting the injection amount,
A spool valve passage 14 in which this fuel injection amount adjustment pressure accumulation chamber 9 is formed in the spool 11, and ports 15, 15 opened in the peripheral wall of the spool chamber 12.
a, 15b, and the inlet valve 7 communicates with the spool valve passage 14 and ports 15, 15a when the accumulated pressure volume of the fuel injection amount adjustment pressure accumulation chamber 9 becomes equal to the maximum injection amount. ,1
5b is shut off to close the valve, and a check valve 40 is interposed in the middle of the fuel passage 23 from the fuel supply device 1 to the inlet valve 7. Device. 2 The check valve 40 is located closer to the filter 2 than the inlet valve 7.
The fuel injection device for an engine according to claim 1, which is interposed in the side inlet passage 23. 3. The engine fuel injection device according to claim 1, wherein the check valve 40 is provided in the filter 2.