JP3296012B2 - Fuel injection control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device used for, for example, an automobile diesel engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection pump for supplying fuel to an automobile diesel engine, for example, a distribution type fuel of a type in which one plunger is reciprocated while rotating to distribute and pressure the fuel to a fuel injection valve. Injection pumps are known. In this fuel injection pump, a cam having a characteristic that a cam speed changes at a constant rate with respect to a cam rotation angle is used as a cam for reciprocating a plunger. However, in the above-described fuel injection pump, when priority is given to the high rotation speed of the diesel engine and the setting is made so that the region where the cam speed is always high is used, the injection rate becomes high, and the knock noise at the low rotation speed becomes large. Would. For this reason, it is required to reduce the knock sound at the time of low rotation while ensuring a high injection rate at the time of high rotation.

In order to meet the above demand, for example, in the technology disclosed in Japanese Patent Application Laid-Open No. 62-288364, FIG.
A non-constant velocity cam having a cam characteristic of No. 3 is used. In this case, a region where the cam speed has a constant low value (low speed region) is provided before the cam characteristic, and a mountain-shaped region where the cam speed increases / decreases (high speed region) is provided after the cam characteristic.

Further, in the above publication, an Angleich mechanism is provided in a delivery valve in a fuel injection pump in order to change a use area of a non-constant speed cam according to a rotation speed of a diesel engine. The Angleich mechanism is a notch provided on the periphery of the suction return collar of the delivery valve, and the notch adjusts the residual pressure in the injection pipe. More specifically, when the engine is running at a low speed, the fuel sucked back by the delivery valve escapes from the notch to the injection pipe side, and the amount of sucked-in fuel decreases, and the residual pressure increases accordingly. On the other hand, when the engine is running at high speed, the fuel sucked back by the delivery valve is less likely to escape from the notch to the injection pipe side, and the residual pressure is as low as the case without the notch.

Accordingly, when the engine is running at a low speed, the fuel pressure in the injection pipe becomes equal to or higher than the valve opening pressure of the fuel injection valve since the stroke of the plunger is small. For this reason, the low-speed region in front of the unequal velocity cam is used, and the injection rate decreases.
In addition, when the engine rotates at high speed, the pressure in the injection pipe does not exceed the valve opening pressure unless the stroke of the plunger increases. For this reason, the high-speed area behind the unequal velocity cam is used, and the injection rate is increased.

The Angleich mechanism is considered to function as follows. Generally, the amount of fuel leakage from the plunger of the fuel injection pump is large when the engine speed is low, and decreases as the engine speed increases.
For this reason, when there is no mechanism for adjusting the fuel pressure, the injection is not started unless the cam characteristic of the unequal velocity cam is at the low rotation speed, and the injection is started at the front of the cam characteristic at the high rotation speed. I will. On the other hand, by providing the Angleich mechanism, at high revolutions, the fuel in the injection pipe is sucked back excessively to lower the residual pressure, thereby compensating for the displacement of the unequal speed cam due to the change in the amount of fuel leak. it can.

Further, in the above-mentioned publication technology, a fuel injection valve having two valve opening pressures is used. This type of fuel injection valve opens a predetermined amount when the pressure of the fuel from the fuel injection pump exceeds the first valve opening pressure, and further opens the predetermined amount when the second valve opening pressure becomes higher than the first valve opening pressure. I do. The fuel pressure from the fuel injection pump when the variable speed cam is in the low speed range is set to be between the first valve opening pressure and the second valve opening pressure. For this reason, when the unequal velocity cam is used in the low speed region, although the fuel pressure from the fuel injection pump is low, the nozzle needle is held at a position corresponding to the first valve opening pressure to perform injection.

By the way, in recent years, exhaust gas regulations in diesel engines have been tightened, and in particular, nitrogen oxides (NOx)
In order to cope with such a reduction, so-called EGR, which is a means for extracting a part of the exhaust gas from the exhaust system and recirculating the exhaust gas to the intake system, is regarded as an effective means. However, when a large amount of EGR is performed, the oxygen concentration in the combustion chamber decreases, and the combustion speed of the air-fuel mixture decreases. To compensate for this, it is necessary to atomize the fuel by injecting the fuel at a relatively high pressure.

However, simply injecting the fuel at a high pressure to promote the atomization of the fuel, the fuel is ejected at a stretch at a high pressure, and the mixing with the air by the swirl in the combustion chamber and the combustion speed are determined by the injection rate. (Rate of change in fuel supply over time). As a result, the injection rate becomes too high, resulting in an increase in smoke due to incomplete combustion. Conversely, if the valve opening pressure is set low to lower the injection rate, or if the oil supply rate of the fuel injection pump is set low,
It becomes difficult to atomize the fuel, which causes an increase in hydrocarbons (HC) in the exhaust gas. Therefore, when performing EGR, it is important to achieve both atomization of fuel by high-pressure injection and suppression of the injection rate.

[0010]

However, in the above-mentioned prior art, an unequal speed cam having a low speed region at the front stage is used.
Although the fuel injection valve having two valve opening pressures is used, as described above, only the low-speed region and the high-speed region of the unequal velocity cam are selectively used according to the engine speed, and the flow rate of the fuel injection valve is determined. No consideration is given to the characteristics. Therefore, simply applying this technology to a diesel engine makes it difficult to perform EGR by reducing the above requirement, that is, the injection rate at the initial stage of injection. In order to meet the above requirements, comprehensive measures including the flow characteristics of the fuel injection valve are required. Thus, the prior art was not sufficient as a measure for reducing nitrogen oxides in exhaust gas.

Further, in the above-mentioned prior art, although the range of use of the unequal-speed cam is adjusted according to the engine speed, no consideration is given to the engine load, and the engine load is not affected even when the load is low or when the load is high. It is set so that the low speed region of the constant velocity cam is used. That is, the use area of the unequal velocity cam is set with priority given to the low load state. For this reason, at the time of high load where the required injection amount is larger than at the time of low load, the injection period becomes longer by the amount of fuel injection in the low speed region, and the amount of smoke generated increases. Also, engine power,
There is also a problem that various performances such as fuel efficiency are reduced.

Further, in the prior art, since the Angleich mechanism is provided in the delivery valve, there is a problem that the mechanism of the delivery valve becomes complicated accordingly. The present invention has been made in view of the above-described circumstances, and its purpose is to
With a simple configuration, without a separate mechanism for adjusting the residual pressure, such as the Angleich mechanism, the low injection rate is achieved by effectively utilizing the low-speed region of the unequal speed cam at low load regardless of changes in the engine speed. , And high pressure injection can be performed by increasing the first valve opening pressure of the nozzle needle in the fuel injection valve. In addition, at high load, the injection period is shortened to suppress the generation of smoke. Another object of the present invention is to provide a fuel injection control device capable of improving various performances such as engine output, fuel efficiency, and the like.

[0013]

According to a first aspect of the present invention, there is provided a fuel injection control device, wherein a plunger is moved at a first moving speed higher than the first moving speed. A fuel pump that has an unequal-speed cam that can be changed to a second moving speed, and that can adjust a fuel pumping speed in accordance with a change in the moving speed of the plunger by the unequal-speed cam; A fuel injection valve for injecting fuel pumped from the fuel injection pump, wherein the fuel injection valve is opened when the pressure of the fuel pumped from the fuel pump is equal to or higher than a first pressure, and the fuel is pumped at the same pressure. The predetermined valve opening position is maintained until the fuel pressure becomes equal to or higher than the first pressure and reaches a second pressure higher than the first pressure, and the pressure of the fuel fed at the same pressure is equal to the second pressure. further large beyond the predetermined open position when the above The fuel pump and the fuel injection valve have a period in which the plunger moving speed is selected to be the first moving speed, and the needle valve is in the predetermined valve opening position. The gist is that the period maintained at least is set to be at least partially overlapped.

[0014] The invention described in claim 2 is the first invention.
In the fuel injection control device according to the above, the needle valve, while the pressure of the fuel pumped from the fuel pump changes from the first pressure to the second pressure ,
Even if the plunger is at the first moving speed, atomization of fuel
Configured to be capable of maintaining a substantially constant flow area of the injection pressure can be secured as possible to its gist that it is.

According to a third aspect of the present invention, there is provided an unequal-speed cam driven to rotate based on the rotation of a diesel engine, and fuel is sucked into the high-pressure chamber by reciprocating motion in accordance with the rotation of the unequal-speed cam. A plunger that pressurizes and pressurizes the pressurized fuel to the outside for a predetermined period of time. As a cam characteristic of the cam speed with respect to the rotation angle of the unequal speed cam, a low speed region where the cam speed is low is provided in the preceding stage. A fuel injection pump capable of adjusting the pumping speed of the fuel by setting, setting a high-speed region where the cam speed is high in the subsequent stage, and changing the moving speed of the plunger according to the usage region of the cam characteristics . by adjusting the area of the lifting to the injection port at a pressure of fuel pumped from the previous SL fuel injection pump, for fuel quantity and pressure corresponding to the area to diesel engine from the injection port Injectable nozzle needle, when the pressure of the fuel from the fuel injection pump is less than a preset first valve opening pressure, holds the nozzle needle in the valve closing position, the pressure is not less than the first valve opening pressure, And when it is less than the second valve opening pressure higher than the first valve opening pressure, the nozzle needle is allowed to move in the valve opening direction, and after the movement reaches the predetermined valve opening position, the nozzle needle is moved to the same position. holding, when the pressure is on the second valve opening pressure or higher, and a fuel injection valve having a valve opening pressure adjusting mechanism for the nozzle needle further allowed to move in the valve opening direction, lower the cam speed slow In the area
Substantially constant injection fuel injection flow rate Previous <br/> Symbol diesel engine with fuel atomization to ensure the injection pressure available Te
In order to set the constant flow rate region that becomes the emissivity as a part of the flow rate characteristics of the fuel injection valve, the fuel injection valve has a function to keep the area of the injection port almost constant even when the movement amount of the nozzle needle changes. Provide a constant flow rate portion, so that the nozzle needle is held at the predetermined valve opening position within a constant flow rate region by the constant flow rate portion,
A period in which the low-speed region of the unequal velocity cam is used for the movement of the plunger and a period in which the nozzle needle is held at the predetermined valve opening position in the constant flow rate region are set to at least partially overlap. a fuel injection control device, is arranged a high-pressure fuel before Symbol pressure chamber to spill passage for spilling to the low pressure side, by opening and closing the spill passage,
A spill valve capable of adjusting the pressure of the fuel in the high-pressure chamber, a rotational speed detecting means for detecting a rotational speed of the diesel engine, a load detecting means for detecting a load applied to the diesel engine, and an engine based on the rotational speed detecting means. As the rotational speed increases, the operating range of the unequal speed cam in the low speed region is shifted to the subsequent stage, and the operating region of the unequal speed cam is shifted from the low speed region to the high speed A spill valve drive control means for adjusting the opening / closing timing of the spill valve is provided to shift the spill valve.

[0016]

According to the first aspect of the present invention, in the fuel pressure pump, the fuel pressurized based on the movement of the plunger by the unequal speed cam is sent to the fuel injection valve. The pressure of the fuel pumped from the fuel pumping pump, with the movement of the plunger, pressurized gradually. The pressure of the pumped fuel is the first
Until the pressure becomes equal to or higher than the pressure, the needle valve is not opened, and fuel injection from the fuel injection valve is not performed. Thereafter, when the fuel pressure rises to the first pressure, the needle valve opens and fuel injection starts.

After the start of fuel injection, the plunger is moved to the first position.
The moving speed of the plunger during the period of moving at the moving speed
And the fuel pumping speed is low. However, with this
The opening of the needle valve is maintained at a predetermined
The fuel actually injected from the fuel injection valve is limited to a low flow rate
ing. Therefore, the fuel pumping speed is low and the fuel injection rate is low.
Even if the pressure is small, the injection pressure itself can be high
Become so. In this way, the plunger is relatively slow
The period of movement at the first movement speed and the opening of the needle valve
At least partially overlaps with the period in which
This fuel injection control device
Injection pressure is high while maintaining low fuel injection rate
A pressure region is formed.

Thereafter, the plunge is moved by the unequal speed cam.
The fuel is moved at the second moving speed,
Pumping speed is increased and pumped from the fuel pump
The fuel pressure will also increase gradually. The pressure of this fuel
When the pressure exceeds the pressure, the needle valve exceeds the predetermined opening.
To further increase the valve opening Te, and child increases the fuel injection rate
Can be.

As described above, in this fuel injection control device,
A region where high-pressure injection is performed while maintaining the low fuel injection rate, a region injected at a high fuel injection rate is performed is formed. Therefore, during low-load operation where the fuel injection amount is small, high-pressure injection can be performed while suppressing the fuel injection rate by performing fuel injection using the former region. As a result, the burning speed can be increased. On the other hand, at the time of high-load operation with a large amount of fuel injection, by performing fuel injection using the latter region having a high fuel injection rate, a large amount of fuel can be injected in a short time, thereby suppressing the generation of smoke. At the same time, various performances such as engine output and fuel efficiency can be improved.

As described above, according to the above configuration, a simple
Injection rate reduction and high pressure injection during low load operation
Of fuel injection and shortening of the fuel injection period during high-load operation
To improve emissions and engine performance
Will be able to do it.

According to the second aspect of the present invention, while the pressure of the fuel pumped from the fuel pump changes from the first pressure to the second pressure, the plunger is driven by the first plunger.
Even at the moving speed, confirm the injection pressure that can atomize the fuel.
It is possible to maintain a substantially constant flow area that can be coercive, it is possible to suppress the fluctuation of the injection rate (injection rate) at which the opening degree of the needle valve varies by a predetermined opening degree near.
Therefore, the injection amount can be stabilized, and the emission and engine performance can be further improved.

According to the third aspect of the present invention, in the fuel injection pump, in a state where the spill passage is closed by the spill valve, the low speed region of the front part in the cam characteristics of the unequal velocity cam is used. When the plunger moves in the fuel pressurizing direction, the fuel in the high-pressure chamber is gradually pressurized. This pressurization increases the pressure of the fuel applied to the nozzle needle of the fuel injection valve. When the fuel pressure is lower than the first valve opening pressure,
By the action of the valve opening pressure adjusting mechanism, the nozzle needle is kept in the valve closed state, and fuel is not injected from the injection port.

When the pressure of the fuel applied to the nozzle needle reaches the first valve opening pressure due to the movement of the plunger in accordance with the rotation of the unequal speed cam, the nozzle opening of the fuel injection valve is controlled by the valve opening pressure adjusting mechanism. The needle is allowed to move in the valve opening direction, and fuel injection is started. With the start of fuel injection, both the lift amount and injection rate of the nozzle needle begin to increase.

After the start of the fuel injection, the moving speed of the plunger and the pumping speed of the fuel are low during a period in which the unequal speed cam is used in a low speed region. However, at this time, the area of the injection port of the fuel injection valve is reduced by the nozzle needle. Therefore, although a low flow rate of fuel is being pumped from the fuel injection pump to the fuel injection valve, only a smaller amount of fuel is injected than the pumped amount. Therefore, the pressure of the fuel applied to the nozzle needle gradually increases.

The pressure of the fuel applied to the nozzle needle is equal to or higher than the first valve opening pressure and is higher than the first valve opening pressure.
When the pressure is lower than the valve opening pressure, the nozzle needle is allowed to move in the valve opening direction immediately after the pressure exceeds the first valve opening pressure. However, when the nozzle needle reaches the predetermined valve opening position, thereafter, the nozzle needle is held at the same position. Predetermined open position of the nozzle needle at this time, Ri by the constant flow section provided in the fuel injection valve, the use range of the non-uniform speed cam is a low speed region
In addition to ensuring injection pressure that allows atomization of fuel,
The fuel injection flow rate into the diesel engine is almost constant.
It is in a constant flow rate range. Therefore, the period until the fuel pressure becomes the second valve opening pressure exceeds the first valve opening pressure, fuel is injected from the injection port of the fuel injection valve, <br/> while being atomized It is kept at a constant injection rate .

As described above, the period in which the nozzle needle is kept at the predetermined valve opening position in the constant flow rate region partially overlaps the period of use of the variable speed cam in the low speed region. During this overlap period, the cam speed is suppressed to a low value, and the fuel pumping speed of the fuel injection pump is suppressed. For this reason, the amount of fuel injected during the above-mentioned overlap period is small, and the injection rate is low. On the other hand, the pressure applied to the nozzle needle is equal to or higher than the first valve opening pressure. Therefore, if the first valve opening pressure is set to a high value, it is possible to perform high-pressure injection while securing a low injection rate period.

Since the nozzle needle is held at a predetermined position within the constant flow rate region by the constant flow rate portion of the fuel injection valve, even if the nozzle needle fluctuates near the predetermined valve opening position, the variation in the injection flow rate is slight. It is.

When the use area of the cam characteristics of the unequal velocity cam shifts from the low speed area to the high speed area, and the pressure of the fuel applied to the nozzle needle further increases to reach the second valve opening pressure, the nozzle needle is opened again. Start moving in the direction. Due to this movement, the injection flow rate from the injection port increases, and the injection rate sharply increases.

When the spill passage is opened by the spill valve,
High-pressure fuel in the high-pressure chamber overflows to the low-pressure side. Due to this overflow, the pressure of the fuel in the high-pressure chamber decreases, and the pressure of the fuel applied to the nozzle needle of the fuel injection valve decreases. When the fuel pressure becomes lower than the first valve opening pressure, the nozzle needle is kept closed by the action of the valve opening pressure adjusting mechanism, and the injection of fuel from the injection port is stopped. In this way, fuel is injected by rotation of the unequal speed cam of the fuel injection pump.

When the opening and closing timings of the spill valve are always the same regardless of the engine speed during the above-described series of fuel injections, the amount of fuel leakage decreases with an increase in the engine speed, resulting in an unsatisfactory fuel injection. The use area of the constant velocity cam in the low speed area is shifted to the front stage side. Also, if the opening and closing timing of the spill valve is always the same irrespective of the engine load and the setting is made such that the low speed region of the unequal speed cam is used with priority given to low load,
Since the fuel injection amount also increases as the engine load increases, the injection period becomes longer by the amount of fuel injection in the low-speed region.

However, in the present invention, during the execution of the fuel injection, the engine speed of the diesel engine is detected by the speed detecting means, and the engine load is detected by the load detecting means. The spill valve is driven by the spill valve drive control means in accordance with the engine speed and the engine load, and the opening and closing timing of the spill valve is adjusted.

With this adjustment, the usage range of the unequal-speed cam in the low-speed range is shifted to the rear side as the engine speed increases. The shift of the use area in this way compensates for the shift of the use area due to the change in the amount of fuel leakage. As a result, even if the engine speed changes, the use area of the unequal-speed cam does not change, and the low-speed area is effectively used. Also, by adjusting the opening and closing timing of the spill valve,
As the engine load increases, the area of use of the unequal velocity cam is shifted from the low speed area to the high speed area. When the high speed region of the unequal velocity cam is used in this manner, the fuel injection amount per unit time becomes larger than when the low speed region is used. As a result, the injection period is shortened, the generation of smoke is suppressed,
Various performances such as engine output and fuel efficiency are fully exhibited.

[0033]

1 to 11 show an embodiment in which the present invention is embodied in a fuel injection control device for a vehicle diesel engine.
It will be described according to.

As shown in FIG. 1, the fuel injection control device includes a fuel injection pump 1 and a fuel injection valve 2 attached to each cylinder of the diesel engine 60. The fuel injection pump 1 according to the present embodiment is a distribution type fuel injection pump that reciprocates while rotating one plunger 3 to distribute and pressure-feed fuel to each fuel injection valve 2. The fuel injection valve 2 is operated by two springs arranged in series.
This is a type of fuel injection valve having two types of valve opening pressures. The fuel injection pump 1 and the fuel injection valve 2 have a predetermined length (600 m).
m).

The fuel injection pump 1 has a drive shaft 5
Are rotatably supported, and a drive pulley 6 is attached to one end (the left end in FIG. 1). Drive pulley 6
Is drivingly connected to the crankshaft of the diesel engine 60 via a belt or the like. The drive shaft 5 has a fuel feed pump (9 in FIG. 1) composed of a vane type pump.
7), and a disk-shaped pulsar 8 are attached. On the outer peripheral surface of the pulsar 8, the same number as the number of cylinders of the diesel engine 60 (for a four-cylinder engine, four
) Are formed at equal angular intervals, and a predetermined number (for example, 14) of protrusions are formed at equal angular intervals between adjacent missing teeth. The other end of the drive shaft 5 is connected to the cam plate 9 via a coupling (not shown). Drive shaft 5 of cam plate 9
On the side surface, the same number of variable speed cams 9a as the number of cylinders of the diesel engine 60 are formed. Drive shaft 5
A roller ring 10 is rotatably mounted on the outer periphery of the other end, and a plurality of cam rollers 11 facing the unequal speed cam 9a are mounted inside. The cam plate 9 is urged by a spring 12 and is always engaged with the cam roller 11.

The plunger 3 for pressurizing the fuel is mounted on the cam plate 9 so as to be integrally rotatable. Then, the rotational force of the drive shaft 5 is transmitted to the cam plate 9 via the coupling, so that the cam plate 9 and the plunger 3 are reciprocated in the left-right direction in the drawing while rotating. The plunger 3 is fitted into a cylinder 14 formed in the pump housing 13,
A high-pressure chamber 15 is formed between the front end surface (the right end surface in FIG. 1) and the inner bottom surface of the cylinder 14.

The same number of intake grooves 16 and distribution ports 17 as the number of cylinders of the diesel engine 60 are formed on the outer periphery of the distal end of the plunger 3. The pump housing 13 is provided with the suction ports 18 and the same number of distribution passages 19 as the number of cylinders, corresponding to the suction grooves 16 and the distribution ports 17. During the operation of the plunger 3, fuel leaks (leak) from a gap between the plunger 3 and the cylinder 14 due to its mechanism. The amount of fuel leak at this time is
It is highest when the engine speed is low, and decreases as the engine speed increases.

In the middle of the distribution passage 19, a delivery valve 20 is provided. The delivery valve 20 sucks back the fuel at the end of the pumping of the fuel and sharply lowers the fuel pressure (residual pressure) in the injection pipe 4, thereby terminating the injection quickly, that is, performing a so-called sharp cut, or This is for maintaining the residual pressure and preventing the backflow of the fuel in the injection pipe 4. The delivery valve 20 is not provided with an Angleich mechanism for adjusting the residual pressure of the injection pipe 4. The amount of fuel sucked back by the delivery valve 20 is almost always constant irrespective of the operation state (engine load, engine speed, etc.) of the diesel engine 60.

When the fuel feed pump 7 is driven based on the rotation of the drive shaft 5, fuel from a fuel tank (not shown) is supplied into the fuel chamber 22 through the fuel supply port 21. In the suction stroke in which the plunger 3 moves leftward in the drawing (returns) and the high-pressure chamber 15 is depressurized, one of the suction grooves 16 communicates with the suction port 18 to move the fuel chamber 22 from the high-pressure chamber 15. Fuel is introduced to
On the other hand, in the compression stroke in which the plunger 3 moves rightward in the drawing (forward movement) to pressurize the high-pressure chamber 15, the pressurized fuel flows through the distribution passage 19, the delivery valve 20, and the injection pipe 4. To the fuel injection valve 2.

The pump housing 13 has a spill passage 23 for fuel overflow that connects the high-pressure chamber 15 and the fuel chamber 22.
Is formed, and an electromagnetic spill valve 24 is provided on the way. The electromagnetic spill valve 24 is a normally open type valve, and the coil 2
In a state where 5 is not energized (off), the valve 26 is opened (opened), and the fuel in the high-pressure chamber 15 overflows to the fuel chamber 22. When the coil 25 is energized (turned on), the valve body 26 is closed (closed), and the overflow of fuel from the high-pressure chamber 15 to the fuel chamber 22 is stopped.

Therefore, by controlling the energization time of the electromagnetic spill valve 24, the electromagnetic spill valve 24 is controlled to close and open. Then, by opening the electromagnetic spill valve 24 during the compression stroke of the plunger 3, the fuel in the high-pressure chamber 15 is reduced in pressure, and the fuel injection from the fuel injection valve 2 is stopped. That is, even when the plunger 3 moves forward, the fuel pressure in the high-pressure chamber 15 does not increase while the electromagnetic spill valve 24 is open, and the fuel injection from the fuel injection valve 2 is not performed. That is, during the forward movement of the plunger 3, the amount of fuel injected from the fuel injection valve 2 is controlled by controlling the timing of closing and opening the electromagnetic spill valve 24.

Below the pump housing 13, a timer device (developed by 90 degrees in the figure) 27 for controlling the fuel injection timing is provided. The timer device 27 controls the position of the roller ring 10 with respect to the rotation direction of the drive shaft 5, thereby controlling the timing at which the variable speed cam 9a engages with the cam roller 11, that is, the reciprocating timing of the cam plate 9 and the plunger 3. Is what you do.

The timer device 27 is operated by hydraulic pressure, and includes a timer housing 28, a timer piston 29 fitted in the timer housing 28, and a low-pressure chamber 30 on one side of the timer housing 28. It is composed of a timer spring 32 for urging the timer piston 29 toward the other pressurizing chamber 31 and the like. The timer piston 29 is connected to the roller ring 10 via a slide pin 33.

In the pressurizing chamber 31 of the timer housing 28,
The fuel pressurized by the fuel feed pump 7 is introduced. The position of the timer piston 29 is determined by the balance between the fuel pressure and the urging force of the timer spring 32. Accordingly, the position of the roller ring 10 is determined, and the reciprocating timing of the plunger 3 via the cam plate 9 is determined.

In order to control the fuel pressure of the timer device 27, a timing control valve (TCV) 35 is provided in a communication path 34 connecting the pressurizing chamber 31 and the low-pressure chamber 30. The TCV 35 is an electromagnetic valve whose opening and closing are controlled by a duty-controlled energization signal, and the fuel pressure in the pressurizing chamber 31 is adjusted by controlling the opening and closing of the TCV 35. Then, the lift timing of the plunger 3 is controlled by the fuel pressure adjustment, and the fuel injection timing from each fuel injection valve 2 is adjusted.

Above the roller ring 10, a rotation speed sensor 36 composed of an electromagnetic pickup coil is provided.
Is mounted facing the outer peripheral surface of the. The rotation speed sensor 36 detects the passage of a projection or the like of the pulsar 8 when they cross, and outputs a timing signal (engine rotation pulse) corresponding to the engine rotation speed NE. Further, since the rotation speed sensor 36 is integrated with the roller ring 10, it outputs a reference timing signal to the plunger lift at a constant timing regardless of the control operation of the timer device 27.

In this embodiment, in addition to the basic structure of the fuel injection pump 1 described above, the characteristics of the unequal-speed cam 9a (cam speed V with respect to the cam rotation angle θ) are set as follows. This characteristic is an element that determines the oil feed rate of the fuel injection pump 1. As shown in FIG. 5, the cam rotation angle θ is θ0
During the period of .theta.1, the cam speed V increases at a constant rate as the variable speed cam 9a rotates. During the period of .theta.1 to .theta.2, the cam speed V becomes constant (predetermined value V1). Further, the cam speed V increases at a constant rate as the unequal speed cam 9a rotates during the period of the cam rotation angle θ of θ2 to θ3, and the cam speed V becomes the maximum value at the time of θ3. As the constant speed cam 9a rotates, the cam speed V decreases at a constant rate. In this embodiment, a region where the cam rotation angle θ is constant between θ1 and θ2 is a low speed region, and the cam speed V is a predetermined value V1.
Larger area (area where cam rotation angle θ is θ2 to θ3a)
Is the high-speed area.

Next, the fuel injection valve 2 for atomizing the fuel pumped at a high pressure from the fuel injection pump 1 and injecting it into each combustion chamber of the diesel engine 60 will be described. As shown in FIGS. 2 and 3, the fuel injection valve 2 includes a vertically elongated nozzle holder 37. Below the nozzle holder 37, a spacer 38 and a nozzle body 39 are arranged in an overlapping state. Spacer 38 and nozzle body 3
Reference numeral 9 is attached to the nozzle holder 37 by a retaining nut 40 screwed to a lower periphery of the nozzle holder 37.

An oil passage 41 is formed in the nozzle holder 37, the spacer 38 and the nozzle body 39. Oil passage 41
Is open at the upper end surface of the nozzle holder 37. The lower end of the oil passage 41 is open to an oil sump 42 below the nozzle body 39. The oil reservoir 42 communicates with the lower surface of the nozzle body 39 via the injection hole 43. Injection hole 4
3 has a tapered surface 43a whose diameter decreases toward the lower side. The high-pressure fuel from the fuel injection pump 1 is supplied to the fuel injection valve 2.
, The fuel can be ejected outward from the injection hole 43 through the oil passage 41 and the oil reservoir 42 in this order.

The nozzle body 39 and the spacer 38 include:
A nozzle needle 44 for opening and closing the injection hole 43 is incorporated. The nozzle needle 44 includes a main body 45 and upper and lower shafts 46 and 47. The main body 45 has a rod shape and is slidably inserted into the nozzle body 39.
The lower end face of the main body 45 faces the oil sump 42, and the pressure of the fuel in the oil sump 42 acts on the lower end face as a force for pushing the nozzle needle 44 upward.

The shaft 46 projecting upward from the main body 45 is slidably inserted into the spacer 38. In addition, an intermediate portion of the shaft portion 47 protruding downward from the main body portion 45 includes:
A sheet surface 47a that contacts and separates from the tapered surface 43a is formed. In the shaft portion 47, the pin portion 47 b below the seat surface 47 a is connected to the injection hole 4 of the nozzle body 39.
3 is slightly smaller than the diameter of the pin portion 4.
An annular injection port 48 through which fuel can pass is formed between the nozzle body 7b and the nozzle body 39. In this embodiment,
The pin portion 47b of the nozzle needle 44 is formed to be relatively long, and this portion constitutes a constant flow rate portion for keeping the area of the injection port 48 substantially constant even when the movement amount of the nozzle needle 44 changes. ing.

Shaft 46 projecting upward from spacer 38
Is mounted with a pressure pin 49. A first spring 51 is interposed between the pressure pin 49 and a guide sleeve 50 incorporated at a substantially central portion in the nozzle holder 37 in a compressed state. The first spring 51 constantly urges the nozzle needle 44 in the valve closing direction (downward in the figure). By this bias, FIG.
When the seat surface 47a comes into contact with the tapered surface 43a, the communication between the oil passage 41 and the injection port 48 is interrupted, and the fuel injection is stopped. At this time, the pin portion 47b
The lower end slightly projects downward from the injection hole 43, and the main body 45 is separated downward from the spacer 38 by a length Lb.

On the other hand, at the time of fuel injection, the nozzle needle 44 rises, and the seat surface 47a is separated upward from the tapered surface 43a. When the valve body is lifted by the length Lb from the valve-closed state, the main body 45 contacts the spacer 38. At this time, as shown in FIG.
Immerse yourself in.

The guide sleeve 50 has a push rod 52
Are movably inserted in the vertical direction. The push rod 52 is located on the same axis as the nozzle needle 44. A second spring 53 is disposed in a compressed state in the guide sleeve 50, and the push rod 52 is constantly urged downward by the second spring 53.

When the nozzle needle 44 is in the valve closed state, the pressure pin 49 is separated downward from the push rod 52 by a length La (<Lb). Therefore, the urging force of the second spring 53 is not applied to the pressure pin 49 and the nozzle needle 44. When the nozzle needle 44 rises by the length La, the pressure pin 49 comes into contact with the push rod 52. When the movement amount of the nozzle needle 44 exceeds the length La, the urging force by the second spring 53 is applied to the nozzle needle 44. In the present embodiment, the pressure pin 49, the guide sleeve 50,
The first spring 51, the push rod 52 and the second spring 53 constitute a valve opening pressure adjusting mechanism A.

In this embodiment, the fuel pressure required to start raising the nozzle needle 44 in the valve closed state is defined as the first valve opening pressure P 1, and the fuel pressure is applied to the push rod 52 via the pressure pin 49. The pressure of the fuel necessary to start raising the nozzle needle 44 again is set to the second valve opening pressure P2.
And The first valve opening pressure P1 is, for example, 200K
It is preferably set to about g / cm2. The second valve opening pressure P2 is desirably set in accordance with the degree of increase in fuel pressure corresponding to a constant cam speed portion of the unequal-speed cam 9a in order to obtain a required fuel injection period.

In the fuel injection valve 2 configured as described above, the moving amount (lift amount L) of the nozzle needle 44 is determined according to the pressure P of the fuel supplied from the fuel injection pump 1. When the pressure Pn of the fuel acting on the nozzle needle 44 in the oil sump 42 is lower than the first valve opening pressure P1, the seat surface 47
a is pressed against the tapered surface 43a. When the fuel pressure Pn becomes higher than the first valve opening pressure P1, the nozzle needle 44
Starts to rise, and the seat surface 47a is separated from the tapered surface 43a. The ascent continues until the pressure pin 49 contacts the push rod 52. After the contact, while the fuel pressure Pn is lower than the second valve opening pressure P2, the nozzle needle 44
Stops rising. Further, when the fuel pressure Pn rises and becomes higher than the second valve opening pressure P2, the nozzle needle 44
Rises again. This rise continues until the main body 45 of the nozzle needle 44 contacts the spacer 38.

The fuel injection valve 2 has a flow rate characteristic shown in FIG. This flow rate characteristic is almost the same as the general flow rate characteristic of the throttle type among the pin type fuel injection valves. The vertical axis in FIG. 6 is the flow rate Q of the compressed air ejected from the injection port 48 when the compressed air is supplied to the oil passage 41 of the fuel injection valve 2 instead of the fuel.

As is clear from FIG. 6, the lift amount L is zero.
In the period of L1, the flow rate Q increases with the lift amount L.
Increases almost in proportion. During the period when the lift amount L is between L1 and L2, the flow rate Q becomes a substantially constant low flow rate (Q1) regardless of the lift amount L. During the period when the lift amount L is larger than L2, the flow rate Q increases substantially in proportion to the increase in the lift amount L. The period from L1 to L2 is a period during which the relatively long pin portion 47b of the nozzle needle 44 passes through the injection hole 43. At this time, the area of the injection port 48 is kept substantially constant, and the flow rate Q becomes substantially constant. As described above, during the period from L1 to L2, the flow rate Q is suppressed to a low value (Q1) by the action of the throttle (throttle).

Further, in this embodiment, a constant low flow rate (Q
1) Constant flow rate range (the period when the lift amount L is L1 to L2)
, The nozzle needle 44 is held at the predetermined valve opening position (the position where the pressure pin 49 contacts the push rod 52), that is, L1 ≦ La ≦ L.
The length La is set so that 2 holds. This is to prevent the flow rate Q from fluctuating even when the lift amount L of the nozzle needle 44 fluctuates near La.

In addition, in this embodiment, the area of the unequal velocity cam 9a used at the time of fuel injection is set as follows. In this setting, it is considered that the injection rate is mainly determined by the cam speed V of the fuel injection pump 1, the diameter of the plunger 3, the flow characteristics of the fuel injection valve 2, and the like. In order to move the plunger 3, the unequal-speed cam 9 is moved.
a during which the low speed region is used, and the nozzle needle 44
Is set so as to at least partially overlap with the period during which the valve is held at the predetermined valve opening position in the constant flow rate region. More specifically, in FIG. 5, during at least a part of the period (θ1 to θ2) of the cam rotation angle θ in which the cam speed V is constant (predetermined value V1), the push pin 52
And the flow rate Q of the fuel from the injection port 48 is set to be small and to be kept at a constant value (Q1).

Further, in this embodiment, the first valve opening pressure P1 of the fuel injection valve 2 is adapted to satisfy the following condition. This condition is such that the cam roller 1
When the unequal-speed cam 9a engages with the nozzle needle 44 at a point where the cam speed V changes to a constant value (V1) from the increase (a point where the cam rotation angle θ is θ1 in FIG. 5), the nozzle needle 44 The pressure Pn of the applied fuel exceeds the first valve opening pressure P1 and the nozzle needle 44 opens.

As shown in FIG. 1, the TCV 35 and the electromagnetic spill valve 24 are electrically connected to the output side of an electronic control unit (hereinafter simply referred to as “ECU”) 54 as spill valve drive control means, respectively. It is connected.
The input side of the ECU 54 is provided with the rotation speed sensor 36.
And an accelerator opening sensor 55 as load detecting means are electrically connected to each other. The accelerator opening sensor 55 detects the opening / closing position of the throttle valve, which changes according to the amount of depression of the accelerator pedal, from the position of the diesel engine 6.
An accelerator opening ACCP corresponding to a load of 0 is detected.

Then, the ECU 54 sets both sensors 36 and 55
The TCV 35 and the electromagnetic spill valve 24 are respectively controlled based on the signal output from the controller. That is, the ECU 54 uses the map, calculates the basic injection amount from the engine speed NE and the accelerator opening ACCP at that time, and corrects the basic injection amount appropriately according to the operating state of the diesel engine 60. The ECU 54 calculates the corrected injection amount (required injection amount).
The spill passage 23 is opened and closed to adjust the fuel pressurization start time and the pressurization end time in the high-pressure chamber 15 based on the spill valve 24. In particular, in this embodiment, the electromagnetic spill valve 24 depends on the operation state of the diesel engine 60.
For pre-stroke control. In this prestroke control, the electromagnetic spill valve 24 is opened before fuel injection, and the electromagnetic spill valve 24 is closed after the plunger 3 starts moving in the fuel pressurizing direction by the unequal speed cam 9a of the cam plate 9. This is a control for starting the fuel pumping by valve opening.

The ECU 54 calculates the basic injection timing from the engine speed NE and the accelerator opening ACCP using a map and calculates the basic injection timing according to the state of the diesel engine 60 (cooling water temperature, intake air amount, etc.). Is corrected. The ECU 54 controls the drive of the TCV 35 of the timer device 27 based on the corrected injection timing, adjusts the opening of the communication passage 34 to adjust the position of the timer piston 29, and thereby sets the roller ring 1 in the rotation direction of the drive shaft 5.
The position of 0 (rotation phase) is advanced or retarded. The control of the injection timing is the same as that generally performed. The advance amount is increased as the engine speed NE increases, and the advance amount is increased as the accelerator opening ACCP increases. .

Next, the operation and effect of the present embodiment having the above-described structure will be described. First, the accelerator opening AC by the accelerator opening sensor 55, such as when idling,
The operation of the fuel injection control device in an operating state where the CP is relatively small and the engine speed NE by the speed sensor 36 is relatively low (hereinafter referred to as a reference operating state) will be described with reference to the timing chart of FIG. I do.

In the characteristic relating to the fuel pressure in FIG.
The broken line indicates the outlet of the fuel injection pump 1 (delivery valve 2).
2 shows the fuel pressure Pp at a point immediately downstream of the pressure 0). The solid line indicates the fuel pressure Pn in the oil reservoir 42 of the fuel injection valve 2. Here, since the injection pipe 4 having a length of about 600 mm is interposed between the fuel injection pump 1 and the fuel injection valve 2, in the actual measurement, the pressure of the fuel pumped from the fuel injection pump 1 is small. , That is, arrives at the oil sump 42 with a phase delay. Therefore, the two pressures Pp and Pn are delayed by a time Δt as shown in FIG.

When the drive shaft 5 of the fuel injection pump 1 rotates by receiving the driving force from the diesel engine 60, the rotation force is transmitted to the cam plate 9 via the coupling.
Is transmitted to By this transmission, the cam plate 9 and the plunger 3 are reciprocally driven in the left-right direction in FIG. 1 while rotating. At this time, the electromagnetic spill valve 24 is in an open state, and the spill passage 23 is open.

During the suction stroke in which the plunger 3 moves to the left in FIG. 1, any one of the suction groove 16 and the suction port 1
8, the fuel is sucked from the fuel chamber 22 into the high-pressure chamber 15 through the suction port 18 and the suction groove 16. afterwards,
The communication between the suction port 18 and the suction groove 16 is cut off, and the distribution port 17 and one of the distribution passages 19 are fitted.

When the plunger 3 further rotates, the ECU
The electromagnetic spill valve 24 is closed by a command signal from 54. The spill passage 23 is closed by this valve closing, and the overflow of fuel from the spill passage 23 is shut off. When the plunger 3 continues to rotate and the unequal-speed cam 9a rides on the cam roller 11, the plunger 3 moves to the right in FIG. 1 and the pressure feeding process starts. (Timing t1 in FIG. 7). Cam roller 11
When the unequal-speed cam 9a is engaged in the range of .theta.0 to .theta.1 in the cam rotation angle .theta., The moving speed of the plunger 3 increases at a constant rate over time. With this increase, the volume of the high pressure chamber 15 gradually decreases,
The fuel inside is pressurized. The high-pressure fuel is pressure-fed from the distribution port 17 to the fuel injection valve 2 via the distribution passage 19, the delivery valve 20, and the injection pipe 4 (timing t1).
~ T2). Therefore, during this period, the fuel pressures Pp, Pp
n rise with time.

At this time, the pressure P of the fuel in the oil sump 42
n is lower than the first valve opening pressure P1, the seat surface 47
a is pressed against the tapered surface 43a, and the nozzle needle 44
Is closed. Therefore, no fuel is injected from the fuel injection valve 2. At this time, both the lift amount L and the injection rate α are “0”.

When the unequal-speed cam 9a engages with the cam roller 11 at a cam rotation angle θ1 (timing t2), and when a time Δt corresponding to a phase delay has elapsed from the timing, the fuel in the oil sump 42 Reaches the first valve opening pressure P1 (timing t3). Then
In the fuel injection valve 2, the nozzle needle 44 is pushed upward against the urging force of the first spring 51, the seat surface 47a is separated from the tapered surface 43a, and fuel injection is started. Accordingly, the lift amount L and the injection rate α
Begins to increase.

After the start of fuel injection, the cam speed V is kept constant (predetermined value V1) until the engagement position of the unequal-speed cam 9a with the cam roller 11 reaches the cam rotation angle θ of θ2. . That is, the moving speed of the plunger 3 becomes constant, and the fuel pumping speed becomes constant. However, at this time, the injection port 48 of the fuel injection valve 2 is throttled by the nozzle needle 44. For this reason, although a fixed amount of fuel is being pumped from the fuel injection pump 1 to the fuel injection valve 2, only a smaller amount of fuel is injected than the pumped amount. Accordingly, the pressure Pn of the fuel in the oil sump 42 gradually increases (timing t3 to t5).

If there is no point in the characteristics of the unequal-speed cam 9a where the cam speed V is kept at a constant value (predetermined value V1) or where the cam speed V changes slowly, the oil sump 42 After the fuel pressure Pn becomes higher than the first valve opening pressure P1, the fuel pressure rapidly rises, and rapidly becomes the second valve opening pressure P2. Therefore, in this case, the fuel can be atomized by the high pressure injection, but the injection rate α is low (t3 to t6).
Is shortened, resulting in an increase in nitrogen oxides and smoke.

Since the fuel injection valve 2 is of a type having two valve opening pressures P1 and P2, the oil sump 42
After the pressure Pn of the fuel inside the first valve exceeds the first valve opening pressure P1, the nozzle needle 4 is held until the pressure pin 49 comes into contact with the push rod 52 (until a predetermined valve opening position is reached).
4 rises. However, when the nozzle needle 44 has the length La
And the pressure pin 49 is
2 (timing t3a), thereafter, the urging force of the second spring 53 is newly applied to the nozzle needle 44. Therefore, while the fuel pressure Pn is lower than the second valve opening pressure P2, the lift amount L of the nozzle needle 44 is kept constant (La).

In this embodiment, as shown in FIG.
Is set within a period (L1 to L2) in which the flow rate Q is constant (Q1). In addition, the flow rate Q1 at this time is a low value. In addition, at this time, the cam speed V becomes a low constant value (predetermined value V1), and the fuel pumping speed from the fuel injection pump 1 to the fuel injection valve 2 is suppressed. Therefore, during the period from the timing t3a to t5, high-pressure injection is performed with the injection rate α suppressed. At this time, even if the lift amount L of the nozzle needle 44 fluctuates near La, the variation in the flow rate Q is small, and a stable flow rate Q can be obtained.

When the unequal-speed cam 9a engages with the cam roller 11 at a cam rotation angle θ of θ2 (timing t4), and when a time Δt corresponding to a phase delay has elapsed from that timing (timing t5). And the cam speed V is higher than the predetermined value V1. Accordingly, the pressure Pn of the fuel in the oil sump 42 continues to increase.
At this time, the lift amount L of the nozzle needle 44 is La
And the injection rate α is kept low.

When the fuel pressure Pn in the oil reservoir 42 further increases and reaches the second valve opening pressure P2 (at timing t6).
), The nozzle needle 44 rises again against the urging force of both springs 51 and 53. When the lift amount L increases and exceeds La, the flow rate Q increases as the lift amount L increases.
Increases almost in proportion. As a result, the injection rate α sharply increases. The rising of the nozzle needle 44 is performed by the main body 45.
Stops when it contacts the spacer 38.

Thereafter, during the compression stroke of the plunger 3, E
When the electromagnetic spill valve 24 is opened by a command signal from the CU 54, the fuel in the high-pressure chamber 15 is reduced in pressure. Accordingly, the pressure Pn of the fuel in the oil sump 42 becomes the first pressure.
When the pressure becomes lower than the valve opening pressure P1, the seat surface 47a is pressed against the tapered surface 43a, and the nozzle needle 44 is closed. Therefore, no fuel is injected from the fuel injection valve 2. At this time, both the lift amount L and the injection rate α are “0”. Even if the plunger 3 moves forward, the fuel pressure in the high-pressure chamber 15 does not increase while the electromagnetic spill valve 24 is open, and the fuel injection from the fuel injection valve 2 is not performed.

In the above series of fuel injection,
The longer the overlap period between the period in which the plunger 3 moves in the low speed region of the unequal speed cam 9a and the period in which the nozzle needle 44 is held at the predetermined valve opening position and the flow rate Q becomes constant, the longer the injection rate becomes, α can be kept low over a long period of time.

As described above, in this embodiment, the fuel injection valve 2
In addition, even if the movement amount of the nozzle needle 44 changes, the injection port 4
8 for keeping the area of the nozzle 8 substantially constant (the pin portion 47).
b) is provided. Then, the constant flow rate portion (pin portion 47)
b), the nozzle needle 44 is moved to the predetermined valve opening position (pressure pin
Is held at a position where it contacts the push rod 52). Further, the use period of the unequal-speed cam 9a in the low-speed region and the constant flow rate region in the fuel injection valve 2 are at least partially overlapped.

For this reason, the cam speed V is suppressed to a low value (predetermined value V1) during the overlap period, and the fuel pumping speed of the fuel injection pump 1 is suppressed. Further, the movement of the nozzle needle 44 stops, and the fuel injection amount is maintained at a substantially constant low value. Then, the period during which the fuel injection valve 2 continues injection at a low flow rate becomes longer. For this reason, the injection rate α decreases during the above-described overlapping period. On the other hand, the fuel pressure Pn applied to the nozzle needle 44 is equal to or higher than the first valve opening pressure P1 and equal to or lower than the second valve opening pressure P2. Therefore, these first
If both the valve opening pressure P1 and the second valve opening pressure P2 are set to high values, it is possible to suppress rapid rise of the nozzle needle 44 after the start of injection, and to perform high pressure injection while securing a period of low injection rate. It becomes possible.

This high-pressure injection can prevent a decrease in the combustion speed of the air-fuel mixture during the execution of EGR. In addition, by securing the low injection rate period, it is possible to prevent a problem in the case where the fuel is simply injected at a high pressure, that is, an increase in hydrocarbon (HC) and smoke. In other words, under the operating conditions where fuel atomization is originally required, such as during the execution of EGR, while sufficiently reducing the nitrogen oxides (NOx) by EGR,
Generation of smoke and the like can be suppressed.

Further, since the nozzle needle 44 is held at the predetermined valve opening position within the constant flow rate range by the pin portion 47b of the fuel injection valve 2, even if the nozzle needle 44 fluctuates in the vicinity of the predetermined valve opening position, the injection flow rate does not change. The variation of
A stable flow rate Q can be secured.

In addition, in this embodiment, the relatively high valve opening pressure P
Since the fuel injection valve 2 having P1 and P2 is used, the pressure Pn of the fuel applied to the nozzle needle 44 as a whole increases, and the flow velocity at the time of fuel passage through the injection port 48 increases. The increase in the flow velocity can prevent the deposition of deposits, which has been a problem in the past.

When the period of the low injection rate is short and the injection rate rises at the beginning of the injection (when a large amount of fuel is injected at the beginning of the injection), the fuel burns at once and the pressure in the combustion chamber rises sharply. The combustion noise increases. On the other hand, in the present embodiment, since the period of the low injection rate is sufficiently ensured, a small amount of fuel injected at the beginning of the injection is burned. Therefore, even if the injection rate rises after the period in which the injection rate is low, the pressure in the combustion chamber rises only slowly, and the combustion noise is reduced.

Further, this embodiment is superior to the prior art in the following points. In the related art, the pressure of the fuel from the fuel injection pump when the low speed region of the unequal velocity cam is used is set to be between the first valve opening pressure and the second valve opening pressure. . Therefore, the first valve opening pressure and the second
The range in which the valve opening pressure can be set is greatly restricted. This phenomenon will be described with reference to FIG. 13. Assuming that the fuel pressure in the low speed range fluctuates in the range from Pa to Pb, the first valve opening pressure P1 must be set to a value lower than the pressure Pa. However, the second valve opening pressure P2 must be set to a value higher than the pressure Pb.

On the other hand, in this embodiment, it is only required that the use period of the low-speed region in the fuel injection pump 1 and the constant flow region in the fuel injection valve 2 at least partially overlap. That is, the first valve opening pressure P1 in the present embodiment is equal to the fuel pressure P at the end time of the constant cam speed period (Pn (t4) in FIG. 7).
It suffices that n be a value lower than Pn (t5) in consideration of the phase delay. Further, the second valve opening pressure P2 is the fuel pressure Pn at the start timing of the constant cam speed period (Pn (t2) in FIG. 7).
It is sufficient if the value is higher than Pn (t3) in consideration of the phase delay. For this reason, the set range of the first valve opening pressure P1 and the second valve opening pressure P2 is wider than that of the prior art. As a result, the fuel injection pump 1 and the fuel injection valve 2
Of the shape of the unequal velocity cam 9a during the manufacture of
Variations in the valve opening pressures P1 and P2 of the fuel injector 2 and variations in the flow rate Q can be absorbed.

Next, the engine load (accelerator opening ACC)
The operation in the case where the engine speed NE becomes high while P) remains as it is, that is, the case where the load becomes low and the engine speed becomes high will be described.

At this time, as in the case of the reference operation state, at a timing (crank angle CA1) before the timing (crank angle CA0) at which the plunger 3 starts to move in the fuel pressurizing direction by the unequal speed cam 9a. Assuming that the electromagnetic spill valve 24 is closed, fuel injection as shown in FIG. 8 is performed. That is, as described above, as the engine speed NE increases, the cylinder 1 of the fuel injection pump 1
4 and the plunger 3, the amount of leakage of fuel leaking from the space between the cam speed V and the plunger 3 is reduced.
Before 1), the nozzle needle 44 starts to rise and fuel injection is started. For this reason, the injection start timing is advanced and the region where the cam speed is constant cannot be used effectively. It is assumed that the electromagnetic spill valve 24 is opened when the required amount of fuel (required injection amount) has been injected (crank angle CA2). This valve opening timing is a timing at which the cam speed V starts to increase from a predetermined value V1.

Therefore, in order to start fuel injection in a region where the cam speed is constant, the closing timing of the electromagnetic spill valve 24 may be delayed. However, simply delaying the valve closing time is not enough. This is because a certain time is required until the pressure of the fuel pumped from the fuel injection pump 1 reaches the fuel injection valve 2 via the injection pipe 4. This time is almost constant regardless of the engine speed NE. On the other hand, when the engine speed NE increases, the change in the crank angle per unit time increases. Therefore, if the fuel injection is to be started at the same crank angle in both the reference operation state and the low load / high rotation, the position of the roller ring 10 with respect to the rotation of the diesel engine 60 is changed, and It is necessary to advance the rotation phase of the cam 9a.

Therefore, in this embodiment, the ECU 54 outputs a signal for advancing the fuel injection timing to the TCV 35 of the timer device 27. The timing at which the TCV 35 opens and closes in response to the output signal from the ECU 54 and engages with the cam roller 11 of the non-constant speed cam 9a is from the position in the reference operation state indicated by the two-dot chain line to the position indicated by the solid line in FIG. It is advanced.

Further, the ECU 54 controls the pre-stroke of the electromagnetic spill valve 24. In this case, the ECU 54 outputs a signal for keeping the electromagnetic spill valve 24 open even when the plunger 3 starts moving in the fuel pressurizing direction by the unequal speed cam 9a. In response to this signal, the electromagnetic spill valve 24 immediately before the cam speed V reaches the predetermined value V1 (crank angle CA1
Continue to open until a). Therefore, this electromagnetic spill valve 24
During the valve opening period, the fuel in the high-pressure chamber 15 is not pressurized even though the plunger 3 is moving. When the cam plate 9 rotates to the crank angle CA1a, the ECU 54
Outputs a signal for closing the electromagnetic spill valve 24. When the electromagnetic spill valve 24 is closed in response to this signal, the fuel pressure P starts increasing from this point. At this time, the closing timing of the electromagnetic spill valve 24 (crank angle CA1a)
Is the valve closing timing (crank angle CA
Slightly faster than 1).

When the closing timing of the electromagnetic spill valve 24 is adjusted as described above, the electromagnetic spill valve 24 determines the end of the injection period required to obtain the required injection amount at that time. The valve opening timing is also adjusted. In this case, the electromagnetic spill valve 24 is opened when the cam speed V becomes a substantially intermediate value between the predetermined value V1 and the maximum value. The opening timing (crank angle CA2a) of the electromagnetic spill valve 24 at this time is slightly earlier than the opening timing (crank angle CA2) in the reference operation state. When the electromagnetic spill valve 24 is opened, the high pressure chamber 1
The fuel in 5 is decompressed. And the oil pool 42
When the internal pressure Pn of the fuel becomes lower than the first valve opening pressure P1, the nozzle needle 44 is closed, and the fuel injection from the fuel injection valve 2 is stopped.

As described above, when the diesel engine 60 is operated at a low load and a high speed, the rotational phase of the unequal speed cam 9a is advanced, and both the closing timing and the opening timing of the electromagnetic spill valve 24 are changed. It is earlier than both periods in the normal operation state. Further, the fuel injection start timing and the fuel end timing are also earlier than both timings in the normal operation state. As a result, the fuel injection pump 1
In consideration of the fuel pressure propagation up to this point, the constant cam speed period is effectively used, and the injection rate α is kept low during this period.

Next, from the reference operation state of the diesel engine 60, when the engine load (accelerator opening ACCP) increases while the engine speed NE remains unchanged,
That is, the operation in the case of high load and low rotation will be described.

At this time, as shown in FIG. 10, as in the case of the reference operation state, the plunger 3 is moved by the unequal-speed cam 9a in the fuel pressurizing direction (crank angle CA0). It is assumed that the electromagnetic spill valve 24 is closed at the timing (crank angle CA1). Then, since the required injection amount in this case is larger than the required injection amount in the reference operation state, and the low speed region of the cam characteristic is used for fuel injection, the electromagnetic spill valve that determines the end of the fuel injection period is used. The valve opening timing of 24 is later than the valve opening timing (crank angle CA2) in the reference operation state. As a result, the fuel injection period becomes longer, and the amount of generated smoke increases. To prevent this, it is effective to shorten the fuel injection period by using the high speed region of the cam characteristic for fuel injection.

Therefore, in this embodiment, the ECU 54 outputs a signal for advancing the fuel injection timing to the TCV 35 of the timer device 27. The timing at which the TCV 35 opens and closes in response to the output signal from the ECU 54 and engages with the cam roller 11 of the unequal-speed cam 9a advances from the position in the reference operation state shown by the two-dot chain line in FIG. 11 to the position shown by the solid line. Be horned. The amount of advance at this time is substantially the same as the amount of advance when shifting from the above-described reference operation state to the low load / high rotation state.

The ECU 54 performs the pre-stroke control of the electromagnetic spill valve 24. In this case, the ECU 54 outputs a signal for keeping the electromagnetic spill valve 24 open even when the plunger 3 starts moving in the fuel pressurizing direction by the unequal speed cam 9a. In response to this signal, the electromagnetic spill valve 24 continues to be opened until the cam speed V is maintained at the predetermined value V1 (crank angle CA1b). Therefore, during this time, despite the plunger 3 moving, the high-pressure chamber 1
The fuel in 5 is not pressurized. When the cam plate 9 rotates to the crank angle CA1b, the ECU 54 outputs a signal for closing the electromagnetic spill valve 24. When the electromagnetic spill valve 24 is closed in response to this signal, the fuel pressure P starts increasing from this point. At this time, the electromagnetic spill valve 24
The valve closing timing (crank angle CA1b) is slightly later than the valve closing timing (crank angle CA1) in the reference operation state.

When the valve closing timing is delayed as described above, the valve opening timing of the electromagnetic spill valve 24 which determines the end of the injection period necessary to obtain the required injection amount at that time is also delayed. In this case, the opening timing of the electromagnetic spill valve 24 is in the middle of a high speed region where the cam speed V is higher than the predetermined value V1. Timing of opening the electromagnetic spill valve 24 at this time (crank angle CA3a)
Is the valve opening timing (the crank angle CA
3) Faster than. When the electromagnetic spill valve 24 is opened, the fuel in the high-pressure chamber 15 is reduced in pressure. And
When the pressure Pn of the fuel in the oil reservoir 42 becomes lower than the first valve opening pressure P1, the nozzle needle 44 is closed, and the fuel injection from the fuel injection valve 2 is stopped.

As described above, when the diesel engine 60 is operated at a high load and a low speed, the rotational phase of the unequal speed cam 9a is advanced. Further, the closing timing of the electromagnetic spill valve 24 is delayed from the closing timing in the normal operation state, and the opening timing of the electromagnetic spill valve 24 is also earlier than the opening timing in the normal operation state. As described above, in the fuel injection, the low-speed region of the cam characteristic is rarely used, and mainly the high-speed region is used. Therefore, the fuel injection period is significantly reduced, and the generation of smoke is suppressed. Further, since the injection period is shortened, fuel efficiency and engine output are improved.

Next, the operation when the engine speed NE further increases from the state where the diesel engine 60 is operated at the high load and low speed, that is, when the load becomes high and high speed will be described. I do. In this case,
Basically, the same fuel injection is performed as in the case of low load and high rotation described above. That is, the fuel injection pump 1
In order to compensate for the delay of the fuel injection start timing caused by the fuel pressure propagation from the fuel injection valve 2 to the fuel injection valve 2, the rotational phase of the unequal-speed cam 9a is advanced from the rotational phase at the time of high load and low rotation. Further, the valve closing timing and the valve opening timing of the electromagnetic spill valve 24 are both earlier than both timings in the normal operation state. Further, the fuel injection start timing and the fuel end timing are also earlier than both timings in the normal operation state. as a result,
In consideration of the pressure propagation of the fuel from the fuel injection pump 1 to the fuel injection valve 2, the high speed region of the cam characteristic is effectively used, and the short fuel injection period is maintained.

As described above, in this embodiment, during execution of fuel injection, the engine speed NE of the diesel engine 60 is detected by the speed sensor 36, and the accelerator opening ACCP is detected by the accelerator opening sensor 55 as the engine load. Is done. And, these engine speeds NE
The opening and closing timing of the electromagnetic spill valve 24 is adjusted by the ECU 54 according to the accelerator opening ACCP.

By this adjustment, as the engine speed NE increases, the range of use of the unequal-speed cam 9a in the low-speed region is shifted to the subsequent stage. The shift of the use area in this way compensates for the shift of the use area due to the change in the amount of fuel leakage. Therefore, unlike the prior art, the engine speed NE can be reduced with a simple configuration without separately providing an Angleich mechanism for adjusting the residual pressure in the injection pipe.
Is prevented from changing the use area of the unequal-speed cam 9a, and the low-speed area can be effectively used. In addition, because there is no configuration to adjust the residual pressure,
Since the load on the first spring 51 for low-pressure injection can be made smaller than in the related art, the durability of the first spring 51 can be improved.

By adjusting the opening / closing timing of the spill valve 24, the unequal speed cam 9
The use area in a is shifted from the low-speed area to the high-speed area. When the high-speed region is used in this manner, the fuel injection amount per unit time is larger than when the low-speed region is used. Therefore, generation of smoke can be suppressed by shortening the injection period, which is advantageous for exhaust gas regulation. Further, by using the high-speed region, various performances such as engine output and fuel efficiency can be sufficiently exhibited.

The present invention is not limited to the configuration of the above embodiment, and may be arbitrarily changed without departing from the spirit of the present invention, for example, as follows. (1) In the above-described embodiment, when the cam speed V reaches a position where the cam speed V turns to a constant value (a position where the cam rotation angle θ is θ1 in FIG. 5), the fuel pressure Pn applied to the nozzle needle 44 becomes the first pressure.
The valve opening pressure is set to be P1, but it is not always necessary to make them equal. In short, the use period of the low-speed region in the fuel injection pump 1 and the constant flow region in the fuel injection valve 2 should at least partially overlap.

(2) In the above embodiment, a constant cam speed region (θ0 to θ2) is set in the cam characteristics. However, as shown by the solid line in FIG. 12, the cam speed V decreases at a constant rate as shown by the solid line in FIG. As shown in FIG. 12, the cam speed V may be set to increase at a constant rate. The former is suitable for setting the valve opening pressures P1 and P2 to relatively low values, and the latter is for setting the valve opening pressures P1 and P2.
Is set to a relatively high value, and the pressure Pn of the fuel is gradually increased after the pressure pin 49 comes into contact with the push rod 52.

(3) Although the accelerator opening ACCP is used as the engine load in the above embodiment, the injection amount may be used instead.

[0109]

As described above, according to the first aspect of the present invention, the plunger is moved to the first moving speed.
The pressure of the fuel pumped from the fuel pump is changed from the first pressure to the first pressure in response to the change in the moving speed of the plunger by the unequal speed cam that can be changed to the second moving speed higher than the second moving speed. A needle valve that is maintained at a predetermined opening degree until the pressure becomes a second pressure higher than the pressure and limits the actually injected fuel to a low flow rate; by the time it maintained the opening period and the needle valve of choice for the speed to a predetermined opening is set so as to overlap at least a portion, high pressure injection line while maintaining a low fuel injection rate And a region where injection is performed at a high fuel injection rate. By using these areas according to the operating state of the engine, it is possible to reduce the injection rate and secure high-pressure injection during low-load operation and shorten the fuel injection period during high-load operation, despite its simple configuration. With this, emission and engine performance can be improved.

According to the second aspect of the present invention, while the pressure of the fuel pumped from the fuel pump changes from the first pressure to the second pressure, the plunger operates at the first moving speed.
Injection pressure that can atomize the fuel
By maintaining a substantially constant flow passage area, it is possible to suppress a change in the injection flow rate (injection rate) when the opening of the needle valve fluctuates near the predetermined opening, thereby stabilizing the injection amount. And emission and engine performance can be further improved.

According to the third aspect of the present invention, the fuel injection valve is provided with a constant flow rate section for keeping the area of the injection port substantially constant even when the movement amount of the nozzle needle changes. Ri by the flow unit, used areas of non-uniform speed cam was in the low speed region
As well as ensuring injection pressure that allows fuel atomization
Injection with almost constant fuel injection flow rate to diesel engine
The nozzle needle is held at the predetermined valve opening position within the constant flow rate range where the rate is constant. The period in which the valve is held at the predetermined valve opening position is set so as to at least partially overlap. Therefore, high pressure injection can be performed by setting the first valve opening pressure of the nozzle needle high while securing a period of low injection rate. By securing the low injection rate period, it is possible to prevent an increase in smoke due to a decrease in combustion speed. Also, by high pressure injection,
It is possible to atomize the fuel during the EGR for reducing the exhaust gas, and it is possible to suppress an increase in smoke and hydrocarbons in the exhaust gas.

Further, by adjusting the opening / closing timing of the spill valve, the operating range of the unequal speed cam in the low speed region is shifted to the subsequent stage as the engine speed increases. For this reason, it is possible to compensate for a shift in the range of use of the unequal velocity cam due to a change in the amount of fuel leakage. Therefore,
Even if there is no separate mechanism for adjusting the residual pressure such as the Angleich mechanism, it is possible to prevent the use area of the non-constant velocity cam from changing due to the change in engine speed with a simple configuration, and to effectively use the low speed area It is possible to do.

Further, by adjusting the opening / closing timing of the spill valve, the operating range of the unequal speed cam is shifted from the low speed range to the high speed range as the engine load increases. For this reason, at the time of a high load, it is possible to shorten the injection period by using the high-speed region of the unequal-speed cam, suppress the generation of smoke, and sufficiently exhibit various performances such as engine output and fuel efficiency.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel injection control device according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a fuel injection valve in one embodiment.

FIG. 3 is a partially enlarged cross-sectional view showing a closed state of a nozzle needle in the fuel injection valve of one embodiment.

FIG. 4 is a partially enlarged cross-sectional view showing a valve opening state of a nozzle needle in the fuel injection valve of one embodiment.

FIG. 5 is a characteristic diagram showing a relationship between a cam rotation angle and a cam speed in the fuel injection pump of one embodiment.

FIG. 6 is a characteristic diagram showing a relationship between a lift amount of a nozzle needle and a flow rate of pressurized air in a fuel injection valve of one embodiment.

FIG. 7 is a timing chart showing a correspondence relationship among an injection rate, a lift amount of a nozzle needle, a fuel pressure, and a cam speed in one embodiment.

FIG. 8 shows an injection rate at low load and high rotation according to one embodiment;
6 is a timing chart showing a correspondence relationship among a lift amount of a nozzle needle, a fuel pressure, a cam speed, and an open / close state of an electromagnetic spill valve.

9 is a timing chart showing a correspondence relationship between an injection rate, a lift amount of a nozzle needle, and the like when the opening / closing timing of the electromagnetic spill valve and the timing of engaging the cam roller of the variable speed cam are adjusted from the state of FIG. is there.

FIG. 10 is a timing chart showing a correspondence relationship among an injection rate, a lift amount of a nozzle needle, a fuel pressure, a cam speed, and an open / close state of an electromagnetic spill valve at the time of high load and low rotation of one embodiment.

11 is a timing chart showing a correspondence relationship between an injection rate, a lift amount of a nozzle needle, and the like when the opening and closing timing of the electromagnetic spill valve and the timing of engaging the cam roller of the variable speed cam are adjusted from the state of FIG. is there.

FIG. 12 is a characteristic diagram showing another example of the relationship between the cam rotation angle and the cam speed.

FIG. 13 is a timing chart showing a correspondence relationship between a cam speed and a fuel pressure in the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection pump, 2 ... Fuel injection valve, 3 ... Plunger, 9a ... Non-constant speed cam, 15 ... High pressure chamber, 23 ... Spill passage, 24 ... Electromagnetic spill valve, 36 ... Rotation speed sensor, 44 ...
Nozzle needle, 47b ... Pin part constituting constant flow rate part,
48: injection port, 54: E as spill valve drive control means
CU, 55: accelerator opening sensor as load detecting means, A: valve opening pressure adjusting mechanism, ACCP: accelerator opening as engine load, NE: engine speed, θ: cam rotation angle, V: cam speed, Q … Flow rate, P… Fuel pressure, P1
... first valve opening pressure, P2 ... second valve opening pressure

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 45/00 F02M 45/06 F02M 41/12 330 F02M 41/12 350 F02M 41/12 360 F02M 41/14 330 F02N 41/14 340 F02M 41/14 350 F02M 61/10 F02D 41/38

Claims (3)

(57) [Claims] An unequal-speed cam capable of changing a plunger between a first movement speed and a second movement speed higher than the first movement speed, wherein the plunger is moved by the unequal-speed cam. A fuel pump capable of adjusting a pumping speed of fuel according to a change in speed; and a fuel injection valve for injecting fuel pumped from the fuel pump. The fuel injector is pumped from the fuel pump. The valve is opened when the pressure of the fuel to be supplied becomes equal to or higher than the first pressure, and until the pressure of the fuel supplied at the same pressure becomes the second pressure which is equal to or higher than the first pressure and higher than the first pressure. The pressure of the fuel that is maintained at a predetermined valve opening position and is fed at the same pressure is equal to the second pressure.
It has a needle valve to further increase the valve opening exceeds the predetermined open position when the above, the A fuel pressure pump and the fuel injection valve, the moving speed of the plunger is chosen to said first moving speed And a period during which the needle valve is maintained at the predetermined valve opening position is set so as to at least partially overlap the fuel injection control device. Wherein said needle valve is moved, while the pressure of the fuel pumped from the fuel feed pump is changed from the first pressure to the second pressure, the plunger is first
Even at high speeds, it is possible to secure an injection pressure that can atomize the fuel.
2. The fuel injection control device according to claim 1, wherein the fuel injection control device is configured to maintain a substantially constant flow passage area. 3. A non-constant speed cam which is rotationally driven based on the rotation of a diesel engine, and fuel is sucked into the high pressure chamber by a reciprocating motion according to the rotation of the non-constant speed cam, and pressurized. A plunger for pumping fuel to the outside for a predetermined period of time, wherein a low speed region where the cam speed is low is set in a front portion thereof as a cam characteristic of a cam speed with respect to a rotation angle of the unequal speed cam, and a cam speed is set in a rear portion thereof. A fuel injection pump capable of adjusting a pumping speed of the fuel by setting a high-speed region and changing a moving speed of the plunger according to a usage region of the cam characteristic; and a fuel pumped from the fuel injection pump. By adjusting the area of the injection port by raising and lowering at the pressure of the nozzle, a nozzle needle that can inject fuel of the amount and pressure corresponding to the area from the injection port toward the diesel engine When the pressure of the fuel from the fuel injection pump is lower than a preset first valve opening pressure, the nozzle needle is held at the valve closing position, and the pressure is equal to or higher than the first valve opening pressure and the first valve opening pressure is increased. When the pressure is less than the second valve opening pressure higher than the second valve opening pressure, the nozzle needle is allowed to move in the valve opening direction, and after the movement reaches a predetermined valve opening position, the nozzle needle is held at the same position, and the pressure is reduced to the second pressure. when the 2 opening pressure or, a fuel injection valve having a valve opening pressure adjusting mechanism for the nozzle needle further allowed to move in the valve opening direction, fine fuel at low low speed range of said cam speed
In order to secure the injection pressure capable of granulating and to set a constant flow rate region where the fuel injection flow rate to the diesel engine becomes an almost constant injection rate as a part of the flow rate characteristic of the fuel injection valve, the fuel injection valve is Is provided with a constant flow rate section for keeping the area of the injection port substantially constant even when the movement amount of the nozzle needle changes, and the nozzle needle is held at the predetermined valve opening position within a constant flow rate range by the constant flow rate section. The period during which the low-speed region of the unequal velocity cam is used for the movement of the plunger and the period during which the nozzle needle is held at the predetermined valve opening position in the constant flow region at least partially overlap with each other. A fuel injection control device set as described above, which is disposed in a spill passage for allowing high-pressure fuel in the high-pressure chamber to overflow to a low-pressure side, and adjusts the pressure of the fuel in the high-pressure chamber by opening and closing the spill passage. A spill valve, a rotation speed detection unit for detecting a rotation speed of the diesel engine, a load detection unit for detecting a load applied to the diesel engine, and an increase in the engine rotation speed by the rotation speed detection unit. The spill valve is shifted in order to shift the operating range of the constant velocity cam in the low speed region to the subsequent stage and to shift the operating region of the unequal speed cam from the low speed region to the high speed region with an increase in the engine load by the load detecting means. A fuel injection control device comprising a spill valve drive control means for adjusting opening / closing timing.