JPH0612102B2 - Accumulation type fuel injection device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation fuel injection device used in a diesel engine or the like, and more particularly to an error in injection amount control due to speed change and fuel accumulation in a pressure-accumulation injection nozzle. The present invention relates to a pressure-accumulation type fuel injection nozzle that eliminates an error in injection timing control due to a leak of an inlet valve of a plunger pump that is press-fitted.

<Prior Art> In general, a pressure-accumulation type fuel injection device uses a check valve on the outlet side of a plunger pump after pressure-regulating a fuel by a fuel supply device and pressure-injecting a metered fuel into a fuel injection nozzle by a plunger pump. Is configured to depressurize the upstream side, and the resulting internal pressure difference between the upstream side and the downstream side of the check valve opens the injection valve of the pressure accumulation type injection nozzle to inject fuel. Since the amount of fuel metered in the fuel supply unit corresponds to the load of the engine, the stroke of the plunger changes according to the load of the engine.

When the stroke of the plunger changes in this way, when the engine is partially loaded, a gap is created between the plunger and a cam or a rocker arm that drives the plunger, which causes a problem such as noise such as striking noise.

In order to solve such a problem, there has heretofore been a system in which a spring is interposed in a drive system for driving the plunger so that the plunger and the cam or rocker arm are always in contact with each other.

However, in this case, other problems such as the stroke of the plunger being deviated due to the vibration of the spring or the vibration of the drive system such as the rocker arm occur.

Therefore, the inlet valve of the plunger pump is configured to open at a predetermined pressure, that is, below the discharge pressure of the plunger, and to close above that pressure, and the inlet valve is provided upstream of the pump chamber of the plunger pump. A pressure-accumulation type fuel injection device has been proposed in which a pressure accumulation chamber for adjustment is connected and a check valve is provided further upstream of the pressure accumulation chamber.

That is, as shown in FIG. 10 (1) and FIG. 10 (2), the fuel supply device 1 that regulates and regulates the amount of fuel and supplies the fuel is supplied.
A plunger pump 2 and a pressure-accumulation type injection nozzle 3 are provided,
An adjustment pressure accumulating chamber 5 is branched and connected to a fuel supply passage 4 that connects the fuel supply device 1 and the plunger pump 2.

The fuel supply device 1 includes a fuel tank 6 that is sequentially connected in series, a fuel pump 7 that pumps fuel from the fuel tank 6, a pressure regulator 8 that controls the fuel supply pressure, and a fuel supply amount that corresponds to the engine load. A regulator (governor) 9 for adjusting the pressure, and a press-fitting pump 10 for pressure-adjusting and feeding the metered fuel.
Have. The press-fitting pump 10 includes a pump chamber 11, a plunger 12 that moves in and out of the pump chamber 11, and a pump chamber 1.
Check valve 1 connected to the upstream side and the downstream side of 1
3 and 14 are provided.

The plunger pump 2 includes a pump chamber 15, a plunger 16 that moves in and out of the pump chamber 11, an inlet valve 17 connected to the upstream side of the pump chamber 15, and a pump chamber 15.
The check valve 18 is connected to the downstream side of the. In the inlet valve 17, the internal pressure of the pump chamber 15 is the bias spring 19
Consists of a seat valve that closes when the urging force of
The check valve 18 is opened when the internal pressure of the pump chamber 15 becomes equal to or higher than a predetermined discharge pressure.

Further, the pressure accumulating type injection nozzle 3 includes an injection pressure accumulating chamber 20 and an injection valve 21 that opens and closes the outlet thereof.

According to the conventional pressure-accumulation type fuel injection device configured as described above, the injection pressure accumulation chamber 2 is changed from the pump chamber 15 of the plunger pump.
After the fuel is discharged to 0, in the process of retracting the plunger 16 from the bottom dead center to the top dead center, first, the internal pressure of the pump chamber 15 is reduced to reduce the internal pressure difference between the upstream side and the downstream side of the check valve 18. The injection valve 21 is opened to exceed the predetermined injection valve opening pressure,
Fuel is injected. The position of the plunger 16 at the end of fuel injection is below the top dead center, and thereafter, the plunger 16 presses the fuel from the adjusting pressure accumulating chamber 5 into the pump chamber 15 to compensate for the drop in the internal pressure of the pump chamber 15. It is completely returned to the top dead center while being pressed by the cam or rocker arm. After that, the metered fuel is press-fitted from the fuel supply device 1 on the upstream side into the adjusting pressure accumulating chamber 5, and after this fuel supply is completed, the plunger 16 is lowered from the top dead center by the cam or the rocker arm. This plunger 1
In the descending process of 6, the fuel is first flowed back from the pump chamber 15 to the adjusting pressure accumulating chamber 5 at a discharge pressure or less. When the remaining amount of fuel in the pump chamber 15 becomes equal to the amount of fuel that has been metered into the adjusting pressure accumulator chamber 5 first, the internal pressure of the pump chamber 15 reaches the discharge pressure and the inlet valve 17 is closed. At the same time, the check valve 18 is opened and discharge from the pump chamber 15 starts.

Therefore, according to this conventional pressure-accumulation fuel injection device, the plunger 16 is always returned to the top dead center, and moreover, it is always in contact with the cam or rocker arm that drives it, so that the plunger strikes the cam or rocker arm. The striking sound will not be generated, and the noise will be reduced.

[Problems to be solved by the invention]

By the way, the inlet valve 17 of the plunger pump 2 is
In the conventional pressure-accumulation type fuel injection device having a seat valve, a pressure gradient is generated between the inlet valve 17 on the pump chamber 15 side and the upstream side when the inlet valve 17 is closed. The maximum lift amount of the inlet valve 17 must be set in consideration of the lift amount due to However,
The above pressure gradient becomes larger as the engine speed becomes faster, and the lift amount due to this also changes in accordance with the engine speed. Therefore, it is extremely difficult to properly set the maximum lift amount of the inlet valve 17. However, there is a problem that an error occurs in the injection amount control due to the speed change. That is, in the high speed operation region, the pressure gradient becomes large, and the pump chamber 15
When the inlet valve 17 is closed and the fuel injection amount is increased before the internal pressure of 6 reaches the regular discharge pressure, the pressure gradient becomes small in the low speed operation region, and the internal pressure of the pump chamber 15 reaches the regular discharge pressure. There is a problem that the closing of the inlet valve 17 is delayed and the fuel injection amount is insufficient.

Further, the biasing means for setting the closing pressure and the opening pressure of the inlet valve 17 is constituted by the bias spring 19, and an error occurs in the closing pressure and the opening pressure due to the manufacturing error of the bias spring 19, or the bias spring 19 is generated. There is also a problem that the vibration of 19 easily causes an error in the fuel injection amount.

In order to solve such a problem, the inventor of the present invention configured the inlet valve with a spool valve and supplied a supply fuel sealed at a predetermined reference pressure as a bias means for setting the valve closing pressure and the valve opening pressure. Inspired to use.

In this case, as will be described later, by configuring the inlet valve with a spool valve, it is possible to eliminate an error in injection control due to a pressure gradient generated between the upstream side and the downstream side of the inlet valve, and a predetermined bias means is provided. By using the supply fuel sealed by the pressure, the error of the valve closing pressure and the valve opening pressure due to the manufacturing error of the bias means is eliminated, and the error of the injection amount control due to the vibration of the bias means does not occur. As described above, during the discharge of the plunger pump, fuel leaks from the pump chamber to the adjusting pressure accumulating chamber through between the spool and the spool chamber accommodating the spool,
It has been found that this leak raises the internal pressure of the adjusting pressure accumulating chamber, which may cause an error in the injection timing control.

The present invention has been made in view of the above circumstances, in which the inlet valve is a spool valve, and the valve closing pressure and the valve opening pressure are set by the supply fuel sealed at a predetermined pressure. It is therefore an object of the present invention to solve the above-mentioned problems of the conventional example and to provide a pressure accumulation type fuel injection device that eliminates an error in injection timing control due to a leak of an inlet valve that may occur in this case.

[Means for solving problems]

In the pressure-accumulation fuel injection device according to the present invention, in order to achieve the above-mentioned object, a pressure-accumulation type injection nozzle, a plunger pump for injecting fuel into the pressure-accumulation injection nozzle, and pressure adjustment and metering for the plunger pump. The plunger pump is provided with a fuel supply device for supplying fuel, and the plunger chamber is connected to an outlet side of the pump chamber, an inlet valve connected to the inlet side of the pump chamber, and an inlet valve connected to the inlet side of the pump chamber. Check valve is provided, a pressure reducing device for reducing the fuel pressure upstream of the inlet valve at a predetermined timing is connected, and the inlet valve includes a spool and a spool chamber that slidably accommodates the spool. The spool is provided with a hollow hole extending from one end of the spool to the vicinity of the other end, a main valve hole extending from one half of the hollow hole to the circumferential surface, and a hollow hole extending from the other end of the hollow hole. With a bias valve hole extending in the plane Middle from the middle portion of the air hole and the inlet hole extending in the circumferential surface is formed, at one end of the spool chamber,
An adjustment pressure accumulating chamber for adjusting the stroke of the plunger of the plunger pump to a full stroke is defined by the spool, and a bias chamber for urging the spool toward one end is defined at the other end of the spool chamber. ,
When the spool is located at the stroke end on the bias chamber side, the main valve hole is cut off in the half portion of the adjustment chamber side on the peripheral surface of the spool chamber, and the spool is located closer to the adjustment pressure chamber side. A main passage that communicates the pump chamber with the main valve is opened, and an inlet passage that connects the inlet hole to the fuel supply device, the pressure reducing device, or the reference pressure setting device is provided in an intermediate portion of the peripheral surface of the spool chamber. Is opened, and the bias valve hole communicates with the bias chamber when the spool is located at the stroke end on the bias chamber side.

[Action]

In the above configuration, the supply of fuel from the fuel supply device is located at the top dead center where the plunger retreats most from the pump chamber, and the spool is located at the stroke end on the adjusting pressure accumulating chamber side, that is, at the bottom dead center, In addition, the internal pressures of the bias chamber, the pump chamber, the pressure accumulating chamber for adjustment, and the hollow hole are started at a predetermined reference pressure. When fuel is supplied from the fuel supply device, the internal pressure of the pump chamber, adjustment pressure accumulating chamber and hollow hole rises, the spool rises from the bottom dead center and the fuel in the bias chamber is compressed, and the internal pressure of the bias chamber rises. Then, the spool moves to a position where the internal pressures of the adjusting pressure accumulating chamber and the hollow hole are equal to the internal pressure of the bias chamber. The position of the spool corresponds to the amount of fuel supplied, and when the amount of fuel supply is large, it is close to the top dead center, and when it is small, it is close to the bottom dead center. After that, in the process of lowering the plunger from the top dead center by the cam or rocker arm, first, the internal pressures of the pump chamber, the pressure accumulating chamber for adjustment, and the hollow hole increase, and the increase of this internal pressure causes the spool to reach the stroke end on the bias chamber side. The fuel is moved toward (top dead center), and the fuel flows backward from the pump chamber to the adjusting pressure accumulating chamber via the inlet valve. Then, when the internal pressures of the pump chamber, the pressure accumulating chamber for adjustment, and the hollow hole reach the valve opening pressure (check valve opening pressure) of the check valve of the plunger pump, the spool reaches the top dead center, and the pump chamber and the pressure accumulating for adjustment are adjusted. The room is shut off. The position of the spool is determined by the balance relationship between the internal pressure of the adjusting pressure accumulating chamber communicating with the pump chamber and the hollow hole and the internal pressure of the bias chamber, and the pressure generated between the upstream side and the downstream side of the inlet valve during reverse flow. It is determined independently of the slope. Therefore, if the volume of the bias chamber is set appropriately, the spool is moved to the top dead center and the inlet valve is closed when the internal pressures of the pump chamber and the pressure accumulating chamber for adjustment are increased to a predetermined check valve opening pressure. You can
In this case, the valve closing timing of the inlet valve will match when the internal pressure of the pump chamber reaches a predetermined check valve opening pressure, regardless of the operating speed of the engine. Fuel is injected into the accumulator type injection nozzle from the pump chamber. Therefore, by thus matching the injection timing of the inlet valve when the pump chamber reaches a predetermined internal pressure, it is possible to eliminate the error in the injection amount control due to the engine speed.

After the inlet valve is closed, the plunger is further lowered to press the fuel into the pressure accumulating injection nozzle.

For fuel injection, after the injection of fuel is completed, the internal pressure of the pump chamber of the plunger pump is reduced, and the difference between the internal pressure of the injection pressure accumulation chamber and the internal pressure of the pump chamber is set to a predetermined value or more and the injection valve is opened. It is done by letting the valve.

It is possible to reduce the pressure in the pump chamber by raising the plunger.However, in order to increase the valve opening speed, the pressure reducing device reduces the internal pressure in the pressure accumulating chamber for adjusting the inlet valve and in the hollow hole so that the spool moves from the top dead center. It is advantageous to lower the pressure to open the inlet valve, and further reduce the internal pressures of the pump chamber, the adjusting pressure accumulating chamber and the hollow hole by the pressure reducing device. When decompressing the pump chamber with this decompression device, decompression is stopped after the end of fuel injection, the spool is moved to the bottom dead center side by the internal pressure of the bias chamber, and the fuel in the adjustment pressure accumulating chamber is pressed into the pump chamber. By doing so, the plunger is pressed against the cam or rocker arm to return to the top dead center. By returning the top dead center while pressing the plunger against the cam or rocker arm in this way, a gap is prevented from being generated between the plunger and the cam or rocker arm, and the cam or rocker arm strikes the plunger. It is possible to prevent the generation of a hitting sound. When the internal pressure of the pump chamber is reduced by raising the plunger, the internal pressure of the adjusting pressure storage chamber and the hollow hole is reduced by the pressure reducing device after the end of fuel injection, and the spool is lowered from the top dead center. The inlet valve is opened, the decompression is stopped at the same time when this valve is opened, and the spool is moved to the bottom dead center side by the pressure difference between the internal pressures of the bias chamber and the adjusting pressure accumulating chamber to move the fuel in the adjusting pressure accumulating chamber to the pump chamber. By pressing into the cam, the plunger is pressed against the cam or rocker arm and returned to the top dead center. In this way, by returning the plunger to the top dead center while pressing the plunger against the cam or rocker arm,
It is possible to prevent a gap from being generated between the plunger and the cam or the rocker arm, and it is possible to prevent an impact that is generated when the cam or the rocker arm strikes the plunger.

Further, since the closing pressure and the opening pressure of the inlet valve are set by the supply fuel sealed at a predetermined pressure in the bias chamber,
It is possible to prevent the error of the valve closing pressure and the valve opening pressure due to the manufacturing error of the bias spring of the prior art and the error of the injection amount control and the injection timing control due to the vibration of the bias means.

By the way, if fuel in the pump chamber, which becomes higher than the check valve opening pressure, leaks into the adjusting pressure accumulating chamber through the gap between the spool and the peripheral wall of the spool chamber while the plunger pump discharges, the adjusting pressure accumulating pressure increases. The internal pressure of the chamber and the hollow hole may be higher than the check valve opening pressure. When the spool is configured to be able to move to the regular stroke end on the bias chamber side, that is, above the top dead center when the internal pressure of the accumulator chamber and the hollow hole becomes higher than the check valve opening pressure. When the spool is moved above the regular hollow hole and the rise of the spool is mechanically limited to the regular top dead center, the internal pressure of the accumulator for adjustment and the internal pressure of the hollow hole are higher than the internal pressure of the bias chamber. Becomes higher. In this way, if there is an error in the top dead center of the spool, or if the internal pressure of the accumulator for adjustment and the internal pressure of the hollow hole become higher than the internal pressure of the bias chamber, the hollow hole and the adjustment hole are adjusted after the plunger reaches bottom dead center. There is a problem that the timing of reducing the internal pressure of the pressure accumulating chamber to connect the main valve hole and the main passage is delayed, the injection timing is delayed, or the main valve hole and the main passage cannot be connected to each other and the injection becomes impossible.

However, in the present invention, when the spool is located at the top dead center (stroke end on the bias chamber side), the bias valve hole communicates with the bias chamber, so the spool reaches the top dead center. The internal pressure of the hollow hole and the accumulator chamber for adjustment is adjusted to the check valve opening pressure equal to the internal pressure of the bias chamber until the spool is lowered due to the reduction of the internal pressure of the rear hollow hole and the accumulator chamber for adjustment. Since the balance between the internal pressure of the hollow hole and the internal pressure of the adjusting pressure accumulating chamber is maintained, the timing at which the main valve hole communicates with the main passage is always constant from the start of pressure reduction of the internal pressure of the hollow hole and the adjusting accumulating chamber. Become.

Before the next fuel supply from the fuel supply device is started, the spool is returned to the bottom dead center.

Further, the internal pressures of the pump chamber, the adjusting pressure accumulating chamber, and the hollow hole are adjusted to the reference pressure before the spool returns to the bottom dead center.

Here, when decompressing the pump chamber by ascending the plunger at the time of fuel injection, by appropriately setting the decompression ability of the decompression device, when the spool returns to the bottom dead center, the pump chamber and the pressure accumulating chamber for adjustment. Also, the internal pressure of the hollow hole can be returned to the reference pressure. However, when the pressure reducing device reduces the pressure of the pump chamber during fuel injection, the pressure reducing capability of the pressure reducing device must be set corresponding to the maximum injection amount. So
During normal operation, the internal pressures of the pump chamber, the hollow hole, and the accumulator chamber for adjustment fall below a predetermined reference pressure before the spool returns to the bottom dead center. As a result, the plunger cannot be pushed up to a predetermined top dead center, and a problem occurs that a gap is generated between the plunger and a cam or rocker arm that drives the plunger, and a hitting sound is generated. However, this problem is to connect a reference pressure setting device to the plunger pump and return the fuel pressure upstream of the inlet valve to a predetermined reference pressure at a different timing after the pressure is reduced and before reaching the bottom dead center of the spool. Can be solved by

<Effects of the Invention> As described above, according to the present invention, by configuring the inlet valve with the spool valve, the plunger pump is irrespective of the pressure gradient generated between the upstream side and the downstream side of the inlet valve. Since the valve is closed in accordance with the internal pressure of the pump chamber, it is possible to completely prevent an error in the fuel injection amount due to a change in operating speed.

Further, since the pressure of the supplied fuel is used for the bias force of the inlet valve, it is possible to prevent the error of the valve closing pressure and the valve opening pressure due to the manufacturing error, and to control the injection amount and the injection timing by the vibration of the bias means. The occurrence of control error can be prevented.

Furthermore, since the bias chamber that applies a bias force to the spool of the inlet valve and the adjusting pressure accumulating chamber communicate with each other when the spool is located at the top dead center (stroke end on the bias chamber side), there is a leak by the time when the plunger descends. The error in the internal pressure of the adjusting pressure accumulating chamber or the error in the spool position is eliminated, and the occurrence of an error in the injection timing control due to the leak of the inlet valve can be prevented.

<Example> An example of the present invention will be described with reference to the drawings.

FIG. 1 is an equivalent circuit diagram of a pressure-accumulation type fuel injection device according to the present invention, FIGS. 2 to 8 are vertical sectional views showing the operation of the unit injector in order, and FIG. Shows the state at the start of fuel supply of the
The figure shows the state at the end of fuel supply, FIG. 4 shows the state when the internal pressure of the pump chamber or the like reaches the discharge pressure, FIG. 5 shows the state during discharge of the plunger pump, and FIG. 6 shows FIG. 7 shows the state at the end of discharge of the plunger pump, FIG. 7 shows the state after the start of injection until ignition, and FIG. 8 shows the state during fuel injection after ignition. Also, FIGS. 9 (1) to 9 (6)
Is a time chart showing the operation of the unit injector, FIG. 9 (1) shows the change of the internal pressure of the accumulator for adjustment, FIG. 9 (2) shows the change of the position of the spool, and FIG.
(3) shows changes in the position of the plunger, FIG. 9 (4) shows changes in the internal pressure of the pump chamber, FIG. 9 (5) shows changes in the opening degree of the injection valve, and FIG. ) Is the change in the internal pressure of the first accumulator and the second
The change of the internal pressure of the accumulator and the change of the fuel injection rate are shown.

This pressure-accumulation type fuel injection device includes a fuel supply device 1 that regulates and regulates the amount of fuel and supplies the fuel, and a plunger pump 2.
And the pressure-accumulation type injection nozzle 3, the plunger pump 2 and the pressure-accumulation type injection nozzle 3 are integrally assembled as a unit injector U.

The fuel supply device 1 includes a fuel tank 6 connected in series in order, a fuel pump 7 for pumping fuel from the fuel tank 6, a pressure regulator 8 for controlling the fuel supply pressure, and a fuel supply amount corresponding to the engine speed. A regulator (governor) 9 for adjusting the pressure, and a press-fitting pump 10 for pressure-adjusting and feeding the metered fuel.
Have. The press-fitting pump 10 includes a pump chamber 11, a plunger 12 that moves in and out of the pump chamber 11, and a check valve 1 that is connected to the upstream side and the downstream side of the pump chamber 11, respectively.
It is composed of 3 and 14.

The unit injector U has an injection pipe 22 and a main body 23, and a vertical axis (indicated by the horizontal axis in FIGS. 2 and 4) that is open to the upper surface of the main body 23 at one side of the main body 23. )
Plunger chamber 24 of
Plunger 16 is inserted in an oily manner and is slidable forward and backward. The pump chamber 15 is defined by the plunger 16 below the plunger chamber 24.

The injection pipe 22 is divided into an upper portion 22a and a lower portion 22b. A downward receiving surface 25 is formed at an intermediate portion of the upper portion 22a of the injection pipe 22, and a lower half portion of the upper portion 22a than the receiving surface 25 is inserted into the main body 23 in a honey-like shape. The lower portion 22b of the injection pipe 22 is screwed to the lower end of the upper portion 22a.
The main body 23 is held between the upper end surface of b and the receiving surface 25.

A check valve chamber 26 for accommodating the check valve 18 of the plunger pump 2 is formed in the lower half of the upper portion 22a of the injection pipe 22,
A pressure accumulation passage 27 communicating with the check valve chamber 26 is formed in the lower portion. The pressure accumulating passage 27 has a nozzle hole 28 at its tip, and is opened / closed by the injection valve 21 in the vicinity of the nozzle hole 28. The injection valve 21 is composed of a needle valve, and its valve shaft 29 penetrates the pressure accumulation passage 27 and the check valve chamber 26,
Furthermore, an upper end wall 30 of the check valve chamber 26 is penetrated in a honey-like manner so as to be able to move forward and backward, and is projected into a valve closing spring chamber 31 formed in the upper half of the upper portion 22a. This valve shaft 29 is used for the check valve chamber 26.
Is enlarged in the radial direction in the vicinity of the upper end of the check valve 18 and the valve seat 32 of the check valve 18 is formed by this enlarged diameter portion. This valve seat 3
2 and the check valve 18 divide the valve opening decompression chamber 33 defined on the upper end side of the check valve chamber 26 by the communication passage 34 into the pump chamber 1
It is connected to 5. Then, the valve seat 32 and the check valve 18
The first injection pressure accumulating chamber 35 is configured by the lower end side portion of the check valve chamber 26 and the pressure accumulating passage 27 which are partitioned by. The injection pressure accumulating chamber 20 of the pressure accumulating type injection nozzle 3 includes the first injection accumulating chamber 35 and the second injection accumulating chamber 38 connected to the first injection pressure accumulating chamber 35 via the check valve 36 and the pressure setting valve 37. The internal pressure of the 2-injection accumulator chamber 38 is maintained at a predetermined high pressure or higher. The second injection pressure accumulating chamber 38 is formed in an annular space formed between the main body 23 and the injection pipe 22 by reducing the middle portion of the lower half of the upper portion 22a of the injection pipe 22 in the radial direction,
The check valve 36 and the pressure setting valve 37 are arranged on the other side of the body 23.

The inlet valve 17 of the plunger pump 2 is the plunger 1
Although it may be provided separately from 6, in order to make the unit injector U small and compact,
It is incorporated in the plunger 16. That is, this inlet valve 1
A spool valve 7 has a spool chamber 38 formed coaxially with the plunger 16 and a spool 39 slidably accommodated in the spool chamber 38.

The spool 39 is provided on one end side in the spool chamber 38.
The adjusting pressure accumulating chamber 5 for adjusting the stroke of the plunger 16 to a full stroke is defined by the above, and the spool 39 is provided at one end side at the other end side of the spool chamber 38.
That is, the bias chamber 40 that biases the adjusting pressure accumulating chamber 5 side is defined.

The spool 39 has a hollow hole 4 extending from the end surface on the adjusting pressure accumulating chamber 5 side to the vicinity of the end surface on the bias chamber 40 side.
1, a main valve hole 42 extending from the half of the hollow hole 41 on the adjusting pressure accumulating chamber 5 side to the peripheral surface, a bias valve hole 43 extending from the other end of the hollow hole 41 to the peripheral surface, and the hollow hole 24. And an inlet valve 44 extending from the intermediate portion of the inlet to the peripheral surface.

On the other hand, in the half portion of the peripheral wall of the plunger 9 on the adjusting pressure accumulating chamber 5 side, when the spool 18 is located at the stroke end on the bias chamber 40 side, that is, at the top dead center, the spool 18 is blocked from the main valve hole 42, and the spool 18 is closed. There are provided main passages 45, 46 which communicate with the main valve hole 42 when the valve lowers from the top dead center. The main passages 45, 46 may be formed by a single circular hole, but here, in order to limit the fuel injection amount before ignition to a small amount, the main valve hole 42 will be provided soon after the spool 39 descends from the top dead center. Minute passage 45 communicating with the spool 3 and the spool 3
9 is divided into a large diameter passage 46 that communicates with the main valve hole 42 when it descends to a predetermined position closer to the bottom dead center. In addition, the main passages 45 and 46 are always in the pump chamber 15
Is in communication with.

Further, the inlet hole 44 is provided in the middle of the peripheral wall of the plunger 9.
Is connected to the fuel supply device 1, and the spool 39 is provided at the stroke end on the adjusting pressure accumulating chamber 5 side, that is, at the bottom dead center in the half portion of the peripheral wall of the plunger 9 on the bias chamber 40 side. A bias pressure correction passage 48 is formed which connects the bias valve opening 43 to the bias chamber 40 when the bias valve opening 43 is positioned.

The inlet passage 47 is connected to the fuel supply passage 4 connecting the plunger pump 2 and the fuel supply device 1 via a passage 49 formed in the main body 23, and the bias chamber 40 is biased via the bias passage 50. It communicates with the pressure accumulation chamber 51. The bias pressure accumulating chamber 51 is composed of a space 52 formed in the upper end portion of the injection pipe 22 and the valve closing spring chamber 31. When the spool 39 is located at the top dead center, the bias accumulating chamber 51 is biased via the bias chamber 40. It communicates with the valve hole 43.

A switching valve 53 is interposed in the fuel supply passage 4. By switching the switching valve 53 at a predetermined timing, a passage 49, an inlet passage 47 and an inlet hole 44 are provided in the hollow hole 41 and the adjusting pressure accumulating chamber 5. Through the fuel supply device 1,
The decompression device 54 and the reference pressure setting device 55 are switched and connected.

The decompression device 54 includes a drain passage 56 that connects the switching valve 53 to the fuel tank 6, and a suction pump 56 and a check valve 57 that are interposed in series in the drain passage 56.
The reference pressure setting device 55 is a pressure regulator 8 that also serves as the pressure regulator 8 of the fuel supply device 1, and the outlet of the pressure regulator 8 is connected to the switching valve 5
It is composed of a constant pressure supply passage 59 connected to No. 3 and a check valve 60 interposed therebetween.

A valve-closing spring 61 for urging the injection valve 21 to close is inserted in the valve-closing spring chamber 31.

Next, the operation of the pressure accumulating fuel injection device will be described with reference to the fuel supply device 1.
Will be described step by step from the time when the fuel supply from is started.

At the time point a in FIG. 9 when the fuel supply from the fuel supply device 1 is started (hereinafter, simply referred to as time point a, and the same applies to each time point after time point b in FIG. 9), as will be described later.
The plunger 16 is located at the top dead center as shown in FIGS. 4 and 9 (3), and the spool 39 is located at the bottom dead center as shown in FIGS. 4 and 9 (2). Further, the internal pressures of the pump chamber 15, the adjusting pressure accumulating chamber 5, the hollow hole 41, the bias chamber 40, and the bias accumulating chamber 51 are set by the reference pressure setting device 55 as shown in FIGS. 9 (1) and 9 (4). The reference pressure is P ₀ .

When fuel is supplied to the unit injector U by the fuel supply device 1 from the time point a, the internal pressures of the pump chamber 15, the adjustment pressure accumulating chamber 5 and the hollow hole 41 rise, and the spool 39 rises from the bottom dead center. As a result, the bias chamber 40 is shut off from the bias valve hole 43 immediately before the internal pressures of the bias chamber 40 and the bias accumulator chamber 51 change, and the bias chamber 4 is closed.
0 and the bias pressure accumulating chamber 51 are filled with a fixed amount of fuel having a reference pressure P ₀ . As the spool 39 rises, the fuel enclosed in the bias chamber 40 and the bias pressure accumulation chamber 51 is compressed, and the internal pressure of the bias chamber 40 and the bias pressure accumulation chamber 51 rises. The spool 39 is located in the pump chamber 1
5, the internal pressures of the adjusting pressure accumulating chamber 5 and the hollow hole 41 and the internal pressures of the bias chamber 40 and the bias accumulating chamber 51 are moved to a balanced position, and at the time point b when the fuel supply is completed, as shown in FIG. It stops at the height corresponding to the fuel amount, that is, the injection amount. That is, when the injection amount is large, the internal pressures of the pump chamber 15, the adjustment pressure accumulating chamber 5 and the hollow hole 41 increase, so that the fuel in the bias chamber 40 and the bias pressure accumulating chamber 51 is largely compressed and the position of the spool 39 is increased. When the injection amount is high and the injection amount is small, the increase in the internal pressure of the pump chamber 15, the adjustment pressure accumulating chamber 5, and the hollow hole 41 is small, so the compression of the fuel in the bias chamber 40 and the bias accumulating chamber 51 is small, and the spool The position of 39 is lowered.

Next, in the process from the time point c to the time point f when the cam or rocker arm (not shown) pushes down the plunger 16 from the top dead center to the bottom dead center, first, the volume of the pump chamber 15 decreases, and an amount commensurate with this decrease. Fuel for main passage 4
The spool 39 is raised to the top dead center before the plunger 16 reaches the bottom dead center as shown in FIG. 4 by flowing into the adjusting pressure accumulating chamber 5 through 5, 46 and the main valve hole 42. While the spool 39 is rising, the rise in the internal pressure of the pump chamber 15 is slowly suppressed by the backflow of fuel to the adjusting pressure accumulating chamber 5, and the internal pressure of the pump chamber 15 is increased by the valve opening pressure (check valve) of the check valve 18. The valve opening pressure) P _d is kept lower than P _d . When the spool 39 reaches the top dead center, the pump chamber 15 is shut off from the adjusting pressure accumulating chamber 5, and the plunger 16 is further lowered, so that the internal pressure of the pump chamber 15 becomes higher than the check valve opening pressure P _d . As shown in FIG. 5, the check valve 18 is opened, and the fuel is discharged to the pressure accumulation type injection nozzle 3.

The internal pressures of the pump chamber 15, the adjustment pressure accumulating chamber 5 and the hollow hole 41 when the spool 39 reaches the top dead center are set by appropriately setting the volumes of the bias chamber 40 and the bias pressure accumulating chamber 51. It can be matched with P _d . In this way, when the spool 39 reaches the top dead center and the inlet of the pump chamber 15 is blocked when the internal pressure of the pump chamber 15 reaches the check valve opening pressure P _d of the check valve 18, The descending stroke of the plunger 16 up to the time of shutting off the inlet is an ineffective stroke in which the plunger pump 2 does not discharge, and the descending stroke of the plunger 16 after this time is an effective stroke. In this case, the position of the spool 39 is irrelevant to the pressure gradient between the pump chamber 15 side of the main valve hole 42 and the adjustment pressure accumulation chamber 5 side, and the balance between the internal pressure of the adjustment pressure accumulation chamber 5 and the internal pressure of the bias chamber. Determined by the relationship. Therefore, the fuel pressure in the pump chamber 15 when the pump chamber 15 is shut off from the adjusting pressure accumulating chamber 5 and the position of the spool 39, that is, Inlet valve 17 and check valve 1
It is possible to accurately control the volume of the fuel enclosed between the fuel injection valve 8 and the fuel injection device 8 according to the fuel supply amount, and it is possible to perform the accurate injection amount control without an error due to a change in the engine speed.

The fuel discharged from the plunger pump 2 is first injected into the first injection pressure accumulation chamber 35 by the time d from when the discharge of the plunger pump 2 starts until the plunger 16 reaches the bottom dead center, and the fuel is rapidly injected into the first injection pressure accumulation chamber 35. The internal pressure of 35 is increased.
Then, after the time point e when this internal pressure becomes equal to or higher than the set pressure of the pressure setting valve 37, the check valve 36 is opened and the second injection pressure accumulating chamber 3 is opened.
The internal pressure of 8 rises above the set pressure, whereby the pressure setting valve 37 is opened, and the internal pressures of the first injection pressure accumulation chamber 35 and the second injection pressure accumulation chamber 38 are equally increased. The check valve 36 is closed by opening the pressure setting valve 37 when the internal pressures of the first injection pressure accumulating chamber 35 and the second injection pressure accumulating chamber 38 become equal, and the plunger 1
After time f when 6 reaches the bottom dead center, the check valve 18 is closed as shown in FIG.

In FIG. 9 (4), the change in the internal pressure of the pump chamber 15 of this embodiment is shown by a solid line, and the change in the internal pressure of the pump chamber 15 when the injection pressure accumulating chamber 20 is composed of a single chamber is shown by a broken line. Indicated by. Further, in FIG. 9 (6), the change in the internal pressure of the first injection pressure accumulating chamber 35 and the second injection pressure accumulating chamber 38 of this embodiment is shown by a solid line, and the injection pressure accumulating chamber 20 is constituted by a single chamber. A change in the internal pressure of the injection pressure accumulating chamber 20 in the case is shown by a broken line.

Next, by reducing the internal pressure of the pump chamber 15, the differential pressure between the internal pressure of the valve opening decompression chamber 33 and the internal pressure of the first injection pressure accumulating chamber 35 is set to a certain level or more, and the injection valve 21 is opened to release the fuel. It is ejected from the nozzle hole 28.

As a method of reducing the internal pressure of the pump chamber 15, there is also a method of raising the plunger 16 from the bottom dead center, but in this case, the rising speed of the plunger 16 is limited by the profile of the cam that drives the plunger 16, 15
There is a problem in that the pressure reduction rate of the internal pressure cannot be increased above a certain level.

In this pressure-accumulation fuel injection device, with the plunger 16 positioned at the bottom dead center, the switching valve 53 is switched at a predetermined time point g to connect the pressure reducing device 54 to the inlet valve 17, and the hollow hole 41 and the pressure accumulating chamber for adjustment. By reducing the internal pressure of 5 to lower the spool 39 from the top dead center, the main valve hole 42 is moved to the main passage 4
The internal pressure of the pump chamber 15 is reduced by communicating with the pump chamber 15 via 5, 46 so that the pump chamber 15 is switched on and off.

As described above, in this pressure accumulation type fuel injection device, the pressure reducing device 5
4, the internal pressure of the pump chamber 15 is reduced by opening and closing the inlet valve 17, so that the rate of pressure reduction of the internal pressure of the pump chamber 15 can be increased and the valve opening speed of the injection valve 21 can be increased.

By the way, while the plunger 16 descends from the time point d to the time point f, a leak occurs from the pump chamber 15 which becomes higher than the check opening valve pressure P _d to the adjusting pressure accumulating chamber 5, and the stroke of the spool 39 becomes normal. In this embodiment, which is mechanically limited at the top dead center, the internal pressures of the hollow hole 41 and the adjusting pressure accumulating chamber 5 when the spool 39 reaches the top dead center are the check valve closing pressure P.
There is a possibility that the pressure may rise to a pressure higher than _d . When such a situation occurs, the communication between the main valve hole 42 and the main passages 45, 46 is started after the pressure reduction on the upstream side of the inlet valve 17 described later is started after the plunger 16 reaches the bottom dead center. The injection timing is delayed, the injection start timing is delayed, or in some cases, the main valve hole 42 and the main passages 45, 46 are not able to be interlocked with each other, so that the injection becomes impossible.

However, in this embodiment, the hollow hole 41 and the adjusting pressure accumulating chamber 5 are connected to the bias chamber 40 and the bias accumulating chamber 51 via the bias valve hole 43 between the time d and the time g when the spool 39 is located at the top dead center. Since they are communicated with each other, the internal pressures of the hollow hole 41 and the adjustment pressure accumulating chamber 5 are adjusted to the check valve opening pressure P _d which is the same as the internal pressures of the bias chamber 40 and the bias accumulating chamber 51.
It is possible to prevent the injection timing from being delayed and the injection to be impossible due to the leak from the pump chamber 15 to the adjusting pressure accumulating chamber 5.

When the main passage is composed of a single circular hole, the injection valve 21 changes in its opening rate as fully opened almost at the same time as the valve opening as shown by the broken line in FIG. 9 (5). When the passage is composed of a single circular hole and the injection pressure accumulating chamber 20 is composed of a single chamber, the change in the fuel injection rate is as shown by the broken line in FIG. 9 (6). Immediately after the start, the injection rate rapidly increased,
After that, the injection rate gradually decreases.

In this embodiment, at a time point h immediately after the spool 39 starts to descend from the bottom dead center, the minute passage 45 is communicated with the main valve hole 42 as shown in FIG. 7, and the internal pressure of the adjusting pressure accumulating chamber 5 is reduced by a minute amount. By increasing the pressure and suppressing the pressure reduction rate of the internal pressure of the pump chamber 15 to be small, the valve opening amount of the injection valve 21, the fuel injection rate and the internal pressure drop of the injection pressure accumulating chamber 20 are limited to a small level, and at the time i of ignition after the start of injection, FIG. In addition to the minute passage 45, the large-diameter passage 46 is communicated with the main valve hole 42 so that the pump chamber 15 suddenly moves.
The internal pressure of is reduced and the injection valve 21 is suddenly fully opened to inject a large amount of fuel at once in high pressure. When the internal pressure of the injection pressure accumulating chamber 20 drops to the setting pressure of the pressure setting valve 37 due to the fuel injection, the pressure setting valve 37 is closed, and thereafter, the internal pressure of the first injection pressure accumulating chamber 35 rapidly decreases. And
The injection valve 21 is closed at the time point k when the internal pressure of the first injection pressure accumulating chamber 35 drops to a predetermined valve closing pressure, and the injection is terminated.

In this way, by limiting the fuel injection rate during the period from the start of injection to the ignition, the explosion noise at the time of ignition can be reduced and the operating noise can be reduced. Further, the internal pressure drop of the injection pressure accumulating chamber 20 during the period from the start of injection to the ignition is limited to a small value, the injection valve is rapidly opened at the time of ignition to eject the fuel at a high pressure, and the internal pressure of the injection accumulating chamber 20 is set to a predetermined set pressure. The injection time can be shortened by closing the second injection pressure accumulating chamber 38 and switching the volume of the injection pressure accumulating chamber 20 to a small volume when the temperature drops to 0. Therefore, it is advantageous in increasing the speed of the engine. .

After the fuel injection is completed, the internal pressures of the pump chamber 15, the hollow hole 41, and the accumulator chamber 5 for adjustment are stabilized to a predetermined pressure lower than the check valve closing pressure P _d , and thereafter, from a predetermined time point l, the plunger is pressed. 16 is raised. In the process of raising the plunger 16, the internal pressures of the pump chamber 15, the hollow hole 41 and the adjusting pressure accumulating chamber 5 are gradually reduced to a predetermined reference pressure P ₀ , and the spool 39 is moved to the bottom dead center by the internal pressure of the bias chamber 40. Be lowered.

Here, when the pump chamber 15, the hollow hole 41, and the adjusting pressure accumulating chamber 5 are decompressed by the decompression device 54 in order to open the injection valve 21, as described above, the decompression capability of the decompression device 54 is the maximum injection amount. Since it is set correspondingly, the internal pressures of the pump chamber 15, the hollow hole 41 and the adjusting pressure accumulating chamber 5 become lower than the predetermined reference pressure P ₀ at the time m when the spool 39 reaches the bottom dead center during normal operation. When the fuel is supplied next time, the internal pressures of the pump chamber 15, the hollow hole 41, and the accumulator chamber 5 for adjustment do not sufficiently increase with respect to the supply amount, and when the plunger 16 is subsequently lowered, the inlet valve 17 is shut off. Is delayed and the fuel injection amount is decreased, or in some cases, when the plunger 16 is lowered, the internal pressure of the pump chamber 15 falls below the check valve closing pressure P _d , and fuel injection becomes impossible.

In order to solve such a problem, in this pressure-accumulation fuel injection device, the reference pressure setting device is maintained for an appropriate period between time point l when the plunger 16 starts to rise and time point m when the spool 39 reaches the bottom dead center. 55 is connected to the inlet valve 17, and the internal pressures of the pump chamber 15, the hollow hole 41, and the adjusting pressure accumulating chamber 5 are adjusted to a predetermined reference pressure P ₀ at time m.

Further, the internal pressure of the bias chamber 40 is returned from the check valve closing pressure P _d to a predetermined reference pressure P ₀ when the spool 39 moves from the top dead center to the bottom dead center.

Since the inlet valve 17 is a spool valve, the internal pressure of the bias chamber 49 is higher than the check valve closing pressure P _d due to leakage from the pump chamber 15 while the plunger 16 descends the effective stroke. Or the fuel leaks from the bias chamber 40 to the hollow hole 41 and the adjustment pressure accumulating chamber 5 during depressurization, and the internal pressure of the bias chamber 40 may be reduced. May cause an error in the injection amount control.

That is, when the internal pressure of the bias chamber 40 is increased by the leak, the spool 39 is returned to the bottom dead center and the hollow hole 4
1 and the internal pressure of the accumulator 5 for adjustment is reduced to a predetermined reference pressure P ₀ , the internal pressure of the bias chamber 40 becomes higher than the predetermined reference pressure, and then the pressure-adjusted and adjusted fuel is When supplied, the spool stops at the bottom dead center side of the position where it should originally be located, and when the plunger 16 is subsequently lowered, the internal pressures of the pump chamber 15, the hollow hole 41 and the adjusting pressure accumulating chamber 5 are the check closing valve pressure. The inlet valve 17 is closed at a pressure lower than P _d , and the fuel injection amount is reduced. On the contrary, when the internal pressure of the bias chamber 40 is reduced by the leak, the hollow hole 41
Also, when the internal pressure of the adjusting pressure accumulating chamber 5 is reduced to a predetermined reference pressure P ₀ , the spool stops above the bottom dead center, and then the pressure is adjusted and the adjusted fuel is supplied to the spool. Is stopped at the top dead center side of the position where it should be originally located, and when the plunger 16 is subsequently lowered, the pump chamber 1
5. If the internal pressures of the hollow hole 41 and the accumulator chamber 5 for adjustment do not become higher than the check valve closing pressure P _d , the inlet valve 17 will not be closed, the closing timing will be delayed, and the fuel injection amount will decrease. become.

However, in this pressure accumulation type fuel injection device, the bias chamber 40 and the bias pressure accumulation chamber 51 are connected to the bias passage 48 while the spool 39 is located at the bottom dead center, that is, between the time point m and the time point a at which the fuel supply is started next time. And bias valve hole 43
Via the pump chamber 15, the hollow hole 41 and the accumulator chamber 5 for adjustment
Therefore, the internal pressures of the bias chamber 40 and the bias pressure accumulation chamber 51 are adjusted to the same predetermined reference pressure P ₀ as the internal pressures of the hollow hole 41 and the adjustment pressure accumulation chamber 5 during this period. As a result, the internal pressure of the bias chamber 40 and the bias accumulator chamber 51 and the hollow hole 41 and the adjustment accumulator chamber 5 when the spool is accurately located at the normal bottom dead center before the fuel supply from the fuel supply device 1 is started next time. Balance with the internal pressure of the inlet valve 17 is restored, and the injection amount is controlled by the fluctuation of the spool position before the fuel supply is started based on the leakage of the inlet valve 17 or the internal pressure of the bias chamber 40 and the internal pressure of the hollow hole 41 and the accumulator chamber 5 for adjustment. It is possible to prevent the error from occurring.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of a pressure-accumulation type fuel injection device according to an embodiment of the present invention, FIGS. 2 to 8 are vertical sectional views showing the operation of the unit injector in order, and FIG. 2 is a unit injector. Shows the state at the start of fuel supply to the
The figure shows the state at the end of the fuel supply, FIG. 4 shows the state when the internal pressure of the pump chamber or the like reaches the discharge pressure, FIG. 5 shows the state during discharge of the plunger pump, and FIG. 6 shows FIG. 7 shows a state at the end of discharge of the plunger pump, FIG. 7 shows a state after the start of injection until ignition, and FIG. 8 shows a state during fuel injection after ignition. FIG. 9 is a time chart showing the operation of the unit injector, FIG. 10 (1) is an equivalent circuit diagram of a conventional pressure-accumulation type fuel injection device, and FIG. 10 (2) is a vertical sectional view of the unit injector. . 1 ... Fuel supply device, 2 ... Plunger pump, 3 ...
Accumulation type injection nozzle, 5 ... adjusting pressure accumulation chamber, 15 ... pump chamber, 16 ... plunger, 17 ... inlet valve, 18 ...
Check valve, 38 ... spool chamber, 39 ... spool, 40
...... Bias chamber, 41 ...... Hollow hole, 42 ...... Main valve hole, 4
3 ... Bias valve hole, 44 ... Inlet hole, 45, 46 ...
Main passage, 47 ... Inlet passage, 54 ... Pressure reducing device.

Claims (1)

[Claims] 1. A pressure-accumulation injection nozzle (3), a plunger pump (2) for injecting fuel into the injection nozzle, and this plunger pump.
(2) is equipped with a fuel supply device (1) for supplying a regulated and metered amount of fuel, and the plunger pump (2) is provided with a pump chamber (15) and withdrawn from and withdrawn from this chamber. A plunger (16), an inlet valve (17) connected to the inlet side of the pump chamber (15), and a check valve (18) connected to the outlet side of the pump chamber (15) are provided while Valve (17)
A pressure reducing device (54) for reducing the fuel pressure on the upstream side of the spool is connected at a predetermined timing, and the inlet valve (17) includes a spool (39) and a spool chamber (38) slidably accommodating the spool (39). The spool (39) is provided with a hollow hole (41) extending from one end of the spool (39) to the vicinity of the other end, and a main valve hole (42) extending from one end half of the hollow hole (41) to the circumferential surface. A bias valve hole (43) extending from the other end of the hollow hole (41) to the peripheral surface and an inlet hole (44) extending from the intermediate portion of the hollow hole (41) to the peripheral surface are formed. An adjusting pressure accumulating chamber (5) for adjusting the stroke of the plunger (16) to a full stroke is defined by the spool (39) at one end side of the chamber (38), and the other of the spool chamber (38) A bias chamber (40) for urging the spool (39) to one end side is defined on the end side, and the spool chamber (38) has a peripheral surface on which the adjusting pressure accumulating chamber (5) side half portion is provided with the spool. (39) Is isolated from the main valve hole (42) when positioned at the stroke end of the bias chamber (40) side,
Open the main passages (45) and (46) that connect the pump chamber (15) to the main valve hole (42) when the spool (39) is located on the adjusting pressure accumulating chamber (5) side. In the middle of the peripheral surface of the spool chamber (38), the inlet hole (4
4) The inlet passage (47) connecting the fuel supply device (1) / pressure reducing device (54) or the reference pressure setting device (55) is opened, and the spool (39) is stroked on the bias chamber (40) side. When located at the end, the bias valve hole (43)
A pressure-accumulation fuel injection device, which is configured to communicate with the (40).