JP2526795Y2 - Fuel injection timing control system for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fuel injection timing control device for a diesel engine.

[Conventional technology]

2. Description of the Related Art Conventionally, as a fuel injection timing control device for a diesel engine, a fuel injection timing control device that advances a fuel injection timing by a fixed amount at a cold start is known. (Actual opening 62-200136
Reference). That is, this device is equipped with a temperature-sensitive actuator filled with thermo wax as a mechanism for advancing during cold, and by connecting this temperature-sensitive actuator to an advancing lever provided in the fuel injection pump, In the cold start, the advance lever is rotated in the advance direction. According to this device, during a cold start, the advance is advanced by a predetermined amount in a low speed region as shown by a two-dot chain line in FIG. The fuel injection timing advance characteristic β is obtained as follows. Therefore, when the engine is cold and the fuel is poorly vaporized, the fuel is injected earlier by an amount corresponding to the advanced angle, and the fuel is sufficiently vaporized by the ignition timing. Is promoted, and stable combustion can be achieved after the start.

[Problems to be solved by the invention]

Generally, in a diesel engine, the fuel injection timing during normal operation is set such that fuel is injected at a time when a large explosive force for pushing down a piston is obtained.

However, in the conventional fuel injection timing control device for a diesel engine, since the fuel injection timing is advanced at the time of cold start, the fuel is ignited before the time at which a large explosive power is obtained at the time of cold start. As a result, it takes a long time for a sufficient inertial force to be applied to the piston, and it takes a long time to start the engine (particularly 0 ° C. or less) (starting from engine cranking until the engine blows up). was there.

In particular, in an automatic car equipped with a torque converter, the load from the torque converter is applied to the piston,
Further, when the load applied to the piston is cold, it increases due to an increase in the viscosity of fluid in the torque converter. If the load is applied to the piston by the fluid resistance of the torque converter,
As described above, when the fuel injection timing is advanced at the time of the cold start, the tendency that it takes time until a sufficient inertia force is applied to the piston becomes more remarkable.

In view of the above circumstances, the present invention intends to provide a fuel injection timing control device for a diesel engine that can achieve stable combustion after the start during a cold start and can shorten the start time. .

[Means for solving the problem]

The configuration of the fuel injection timing control device for a diesel engine according to the present invention will be described with reference to FIG. 1 and FIG.

This device, while starting the advance control of the fuel injection timing from a specific basic advance angle start rotational speed N ₀ is higher than the idling speed in a warm state, fuel injection in the low speed range below a predetermined rotational speed in the cold In a diesel engine provided with an advancing means 31 for advancing the timing by a predetermined amount, when the rotation speed rises from engine cranking in a cold state, the rotation speed is lower than the basic advance start rotation speed N ₀ and the idling rotation speed. until high set number number N ₁ and the lead angle control means 32A for stopping the advance of the fuel injection timing to stop the operation of the advance means 31,
In which and a advance start means 32B for starting the operation of the advance means 31 from the set rotation speed N _1.

In the present invention, it is preferable that the operation of the advancing means 31 be performed even in a region equal to or lower than the idle speed during the operation after the operation of the advancing means 31 is started.

[Action]

According to the above configuration, at the time of the cold start, the operation of the advancing means 31 by the advancing suppression means 32A until the inertia force of the piston at the time of the increase in the number of revolutions from the engine cranking exceeds the idling number of revolutions which is sufficiently provided. Stops so that the fuel injection timing is not advanced. Therefore, at this time, the fuel is injected at a time when a large explosive force for pushing down the piston is obtained, and the inertia force is quickly applied to the piston. In other words, as described above, a large explosive force for pushing down the piston is obtained, so that the rotation speed at the start is increased, and the rotation speed is rapidly increased. Further, after the engine speed exceeds the idling speed and the inertia force of the piston is sufficiently provided, the fuel injection timing is advanced by a predetermined amount in the low rotation range below the predetermined speed by the advancing means 31. For this reason, at the time of cold start, after the inertia force of the piston is sufficiently provided, the fuel is sufficiently vaporized by the ignition timing, and the warm-up is promoted, and stable combustion after the engine is started is performed. As a result, misfire is prevented.

That is, the set rotational speed N ₁ is the rotational speed of the operation of the advancing means 31 at the time of cold start is initiated is higher than the idling speed but basic advance angle start rotational speed (the advance angle control during the warm Since the rotation speed is lower than the (starting rotation speed) N _0, the start-up promotion operation and the warm-up promotion operation in the cold state are compatible.

In addition, if the operation of the advancing means 31 is performed even in a region below the idling rotational speed during the continuation of the operation after the operation of the advancing means 31 is started, the starting operation in which the piston has a sufficient inertia force is performed. During the later operation, the fuel injection timing is advanced at a low speed in a cold state, so that warm-up is promoted and combustion stability is achieved.

〔Example〕

FIG. 2 shows an embodiment of a fuel injection timing control device for a diesel engine according to the present invention. In this figure, 1 is a drive shaft of a fuel injection pump, 2 is a roller holder, and 21 is a timer control valve (TCV).

The timer control valve 21 includes a timer cylinder 22
And a timer piston reciprocating in the timer cylinder 22
23, a high-pressure chamber 22a and a low-pressure chamber 2 formed between each end of the timer cylinder 22 and each end of the timer piston 23, respectively.
2b, and a solenoid valve 28 that communicates and shuts off the communication path 27. A timer spring 25 that urges the timer piston 23 toward the high-pressure chamber 22a is interposed in the low-pressure chamber 22b, and the discharge pressure of the pump chamber is introduced into the high-pressure chamber 22a from the pump chamber of the fuel pump through the fuel inlet 26a. It has become. The roller holder 2 and the timer piston 23 are connected by a pin 24. When the timer piston 23 reciprocates in the timer cylinder 22, the roller holder 2 rotates relative to the drive shaft 1 accordingly. ing. At this time, when the roller holder 2 rotates in the direction opposite to the rotation direction of the drive shaft 1 (direction of arrow A), the fuel injection timing is advanced.

Communication passage 27 and the solenoid valve 28 for timer control valve 21 can be obtained by allowing the electronic control of fuel injection timing advance, the advance characteristics, such as alpha ₂ in FIG. 4 to be described later in the cold This is provided for the purpose. The basic structure of the timer control valve 21 except for the communication passage 27 and the solenoid valve 28 is conventionally known, and the basic structure and a cold time advance (not shown) attached to the fuel injection pump 1 are illustrated. The angle advance mechanism 31 is constituted by a mechanism for the corner (a well-known mechanism as described in the section of the prior art).

In the above configuration, when the solenoid valve 28 is closed, the communication path 27 is shut off, and the pump chamber discharge pressure is introduced only from the pump chamber of the fuel pump to the high-pressure chamber 22a through the fuel inlet 26a. become. In the warm state in this state, when the engine speed increases and the pump chamber discharge pressure increases, the pressure in the high-pressure chamber 22a increases accordingly, and a specific basic advance angle higher than the idle speed is obtained. When the rotation speed exceeds the start rotation speed N ₀ (see FIG. 4), the high-pressure
Due to the pressure increase inside, the force acting on the timer piston 23 becomes larger than the urging force of the timer spring 25, and the timer piston 23 moves toward the low-pressure chamber 22b. With the movement of the timer piston 23, the roller holder 2 rotates in the direction opposite to the rotation direction of the drive shaft 1, and the fuel injection timing is advanced.

On the other hand, when the solenoid valve 28 is open,
The communication path 27 is communicated, and the pump chamber discharge pressure introduced into the high-pressure chamber 22a is also introduced into the low-pressure chamber 22b through the communication path 27, and the pressure in the high-pressure chamber 22a and the pressure in the low-pressure chamber 22b And the timer piston 23 becomes the timer spring 25
Is pressed toward the high-pressure chamber 22a.
For this reason, if the solenoid valve 28 is continuously opened, even if the urging force in the advancing direction by the above-described mechanism for advancing at the cold time is acting in the cold state, the urging force of the timer piston 23 is larger than this. As a result, the predetermined retarded state is maintained, and the fuel injection timing is not advanced. When duty control of the solenoid valve 28 is performed by repeatedly opening and closing the solenoid valve 28, the advance amount of the fuel injection timing changes accordingly, and the advance amount can be controlled.

Reference numeral 3 denotes a control unit, which includes an advance suppression means 32A and an advance start means 32B as shown in FIG. The control unit 3 receives detection signals from the crank angle detection means 33, the engine coolant temperature detection means 34, and the engine speed detection means 35, respectively. And from this control unit 3,
The fuel injection timing advance amount control signal is output to the solenoid valve 28 of the timer control valve 21.

The advance angle suppression means 32A and the advance angle start means 32B control the operation of the advance angle means 31 according to signals from the engine coolant temperature detection means 34, the engine speed detection means 35, the starter switch 36, and the like. . That is, the engine speed is equal to or lower than the set rotational speed based on the set rotational speed lower than the basic advance start rotational speed N ₀ and higher than the idle rotational speed (first set rotational speed N ₁ ). When the starter signal is input, the advancing means 31 operates (leading during cold)
Control so that the fuel injection timing is not advanced,
If the starter signal is not input even if the engine speed is equal to or lower than the set speed, or if the engine speed exceeds the set speed, control is performed to activate the advance angle means 31. It has become.

FIG. 3 shows a specific example of control by the control unit 3.

In this flowchart, when started, first in step S _1, it is read from the engine speed detecting means 35 and the engine coolant temperature detecting means 34 and a water temperature of the rotational speed and the engine of the engine, respectively. In step S _2, whether the starter step 36 is turned ON, i.e., the starter switch 36
It is determined whether or not a starter signal has been output from.

Or When this starter signal from the starter switch 36 is determined to be output in step S _2, the rotation speed Ne of the engine in step S ₃ is first set rotational speed N ₁ (N _1> idling speed) or more It is determined whether or not. Step S ₃
In when the rotation speed Ne of the engine is determined to be the first set rotational speed N ₁ or more, a crank angle detecting means at step S ₄ 33
From loading the crank angle, the target value of the previously stored fuel injection timing advancing amount to map each and the actual fuel injection timing advance amount matches in accordance with the water temperature of the rotational speed and the engine of the engine in step S ₅ It is determined whether or not there is.

When the actual fuel injection timing advance amount and the target value of the fuel injection timing advance amount is determined to not match at step S _5, the fuel injection timing advance of the actual fuel injection timing advance amount at step S ₆ Feedback control (duty control) of the solenoid valve 28 is performed so as to match the target value of the angular amount, that is, to follow the map. The advance amount by the feedback control performed according to this map is set to change stepwise or linearly according to the engine water temperature, and is set to decrease as the engine water temperature increases. Then, it is set to be 0 when the engine is sufficiently warmed.

Step S after the actual fuel injection timing advance amount and the target value of the fuel injection timing advance angle is determined to match at _5, step S ₇ rotational speed Ne of the engine at the second set rotation speed N ₂ (N ₂ >
N ₁ ) It is determined whether it is equal to or greater than N ₁ ). Note that the second set rotation speed N _2, it and Ford back control advance angle amount and the advance amount by the machine control is set according to the water temperature so that the rotational speed that matches by electric control (Fig. 4 reference).

Step S rotational speed Ne of the engine ₇ is the second set rotation speed N ₂
Returns to the start if a is determined that less than the other, the rotation speed Ne and the second set rotation speed of the engine in step S ₇
If it is determined that the N ₂ or terminates control by the flowchart. The rotation speed Ne of the engine in step S ₇ is determined to be the second set rotation speed N ₂ or more, after the control according to this flowchart ends, the low-pressure chamber
When a predetermined pump chamber discharge pressure is introduced into 22b, the solenoid valve 28 is closed, and the timer spring
The difference between the force obtained by adding the spring force of 25 and the predetermined pump chamber discharge pressure introduced into the low pressure chamber 22b, and the pressure of the high pressure chamber 22a due to the pump chamber discharge pressure that constantly changes according to the engine speed. Thus, the fuel injection timing advance amount is mechanically controlled.

In the above control, the starter switch 36 in step S ₂
Determines that the starter signal is output from, then the rotational speed Ne of the engine in step S ₃ is When it is determined that the first set lower than the rotational speed N ₁ is continuously solenoid valve 28 is step S ₈ is executed Will be opened to the public. When the solenoid valve 28 is continuously opened, the timer control valve 21 operates as described above, and the fuel injection timing is not advanced. After this step S ₈ run,
Step skip S ₄ and step S ₅ executes step S _7. In other words, until the rotation speed Ne of the rotational speed increase when the engine from the engine cranking the starter switch 36 is ON reaches a first predetermined rotational speed N ₁ is a map of the solenoid valve 28 in step S ₆ not performed feedback control in accordance with the step S ₈ is executed fuel injection timing is no longer advanced.

In other words, Step S ₈ according to the determination of the ON in step S ₃
The processing function of the advance control means 32A is achieved, also, by moving to step S ₄ and subsequent processing when the determination in Step S ₃ was Tsu switching to YES, advance start means
The function as 32B is achieved.

Further, when the starter signal from the starter switch 36 is determined to have not been output in step S _2, the step
Step S ₄ is executed by skipping S _3. Therefore, in this case, step S ₈ is not performed, the field back control in accordance with the map of the solenoid valve 28 in step S ₆ is carried out. That advance operation the duration after the start, even operation of the advancing means in the following areas idle speed (in step S ₄ to S ₇₎ is to be carried out.

As described above, in the control according to this flowchart,
The rotation speed Ne of the rotational speed increase when the engine from the engine cranking the starter switch 36 is ON until exceeds the first set rotation speed N ₁ is no longer the fuel injection timing is advanced, otherwise, i.e. Starter switch 36 is ON
Even if the engine speed Ne is the first set speed N ₁
And is greater than or equal to the rotation speed Ne of the engine is in the like if the starter switch 36 be a first set lower than the rotational speed N ₁ is in the OFF, the feed bag control in accordance with the map of the solenoid valve 28 The fuel injection timing is advanced by a predetermined amount according to the water temperature or the like.

FIG. 4 shows the relationship between the fuel injection timing and the engine speed when the engine is cold.

Immediately after engine cranking, that is, immediately after turning on the starter switch 36, when the piston 5 does not have sufficient inertial force, the starter signal is output from the starter switch 36 and the engine speed Ne exceeds the idling speed. It is in a state where it has not risen to 1 set rotation speed N ₁ , and the step in the above flowchart is performed.
The discrimination at S ₂ and Step S _3, comprising the step S ₈ is performed as the fuel injection timing is not advanced (in the figure,
α ₁ ). After that, turn on the starter switch 36 for a while
If you leave the rotation speed Ne of the engine by the action of the cell exceeds the first predetermined rotational speed N _1, so that a sufficient inertial force to the piston 5 is provided. At this time, starter switch 36
The starter signal is output from the
There since have become first set rotation speed N ₁ or more states, the discrimination at the step S _3, Step S ₄ and step S ₅ is performed, in accordance with the map of the solenoid valve 28 in step S ₆ Feedback control (duty control) is performed. That is, the force corresponding to the pressure applied to the timer piston 23 against the urging force of the timer spring 25 and the force from the mechanism for advancing the cold state are applied to the roller holder 2 of the fuel injection pump.
, The pressure applied to the timer piston 23 is controlled. And this control, the rotation speed Ne of the engine during cold start advancing the fuel injection timing is started exceeds a first predetermined rotational speed N _1, it will be kept in a state of being given RyoSusumu angle (In the figure, α ₂ ).

Incidentally, after the rotational speed Ne of the engine exceeds a first predetermined rotational speed N _1, further comprising as a second exceeds the set rotational speed N _2,
Instead of the electrical control according to the above flowchart, mechanical control is performed (α _{3 in the} figure). In this case, Returning rotational speed Ne of the engine is the second set lower than the rotational speed N _2, so that the electrical control by the flowchart is performed again.

When the OFF the starter switch 36 after a sufficient inertial force is provided in the piston 5, the starter signal from the starter switch 36 is not output, step S ₃ is no longer performed by the discrimination at step S _2. Therefore, the rotation speed Ne of the engine is also lower than the first set rotation speed N _1, is performed feedback control in accordance with the map of the solenoid valve 28 in step S _6, the fuel injection timing is predetermined RyoSusumu angle (Α _{4 in the} figure).

However, in the case of α ₂ and α _4, the advance amount is controlled to decrease as the engine water temperature increases, and α ₅
As shown in (2), when the engine is sufficiently warmed, for example, when the warm-up is sufficiently advanced, the advance amount is set to zero.

In addition, as a characteristic of the mechanical control by the timer control bag at the time of warm when the mechanism for advancement at cold time does not work,
As described above, the start advance from a specific basic advance angle start rotational speed N _0, it is gradually advanced in response to the rotation speed increase. The first set rotation speed, which is the advance rotation speed at the time of cold operation
By N ₁ is higher than the idle rotational speed lower than the basic advance start rotational speed N _0, the fact that the action of such as the start-promoting action and promotion of warming is obtained.

In the figure, β is ON / OF of the starter switch 36.
F, that is, regardless of whether or not the starter signal is output from the starter switch 36, the solenoid valve 28
2 shows a fuel injection timing advance amount curve obtained by a conventional diesel engine fuel injection timing control device in which the fuel injection timing is advanced by a predetermined amount by performing feedback control according to the map of FIG.

FIG. 5 compares the elapsed time until the engine blows up when the engine is cold in the case of the fuel injection timing control device of the diesel engine and the case of the conventional fuel injection timing control device of the diesel engine. The results show that, in the case of the diesel engine fuel injection timing control device shown by the solid line, the start time at the cold start is lower than that of the conventional diesel engine fuel injection timing control device shown by the broken line. You can see that it has been shortened. That is, in the diesel engine fuel injection timing control device, during the cold start, the engine speed N ₁ exceeding the idling engine speed when the engine speed increases from engine cranking.
Until then, the operation of the advancing means 31 is stopped by the advancing suppression means 32 so that the fuel injection timing is not advanced. Accordingly, when the inertial force of the piston to rotational speed N ₁ exceeding the idling speed when the rotation speed increase from the engine cranking, such as described above is not provided sufficient, large explosive force for pushing down the piston is obtained The fuel is injected at the appropriate timing, and a sufficient inertia force is quickly applied to the piston, so that the start time at the time of the cold start is reduced.

Further, in the fuel injection timing control device for a diesel engine, at the time of cold start, when the inertia force of the piston is sufficiently provided, the advancing means 31 operates to advance the fuel injection timing by a predetermined amount. Has become. For this reason,
When the engine is cold and fuel vaporization is poor, fuel is injected earlier by the amount advanced, and fuel is sufficiently vaporized by the ignition time, promoting warm-up during cold start At the same time, the fuel does not enter the semi-misfire zone (shaded area) shown in FIG. 4 to prevent misfire, thereby enabling stable combustion after the engine is started.

6 to 8 show another embodiment. In the above-described embodiment, the advance suppression means 32A and the advance start means 32B are configured as electrical control means.In this embodiment, the advance means 31, the advance suppression means 32A, and the advance start means 32B are provided.
Is configured as a mechanical means so as to have characteristics similar to the advance angle characteristics shown in FIG. Incidentally, FIG. 6 shows an engine stop state, FIG. 7 shows a state when the rotation speed Ne of the engine reaches the second set rotation speed N ₂ or more, in these figures, same as in Example Are given the same numbers and description thereof is omitted.

In this embodiment, the communication passage of the timer control valve 21 and the solenoid valve are eliminated, so that the pump chamber discharge pressure is introduced only into the high-pressure chamber 22a and the pump chamber discharge pressure is not introduced from the high-pressure chamber 22a into the low-pressure chamber 22b. I have to. Then, a concave portion 23a is formed in the end face of the timer piston 23 on the side of the high pressure chamber 22a, and the timer piston
An O-ring 28 that fits into the recess 23a is attached to the end face of the high-pressure chamber 22a on the side facing the high-pressure chamber 22a, and when the timer piston 23 is shifted toward the high-pressure chamber 22a, the O-ring 28 is It is in contact with the side end face. Thus, when the timer piston 23 is leaning toward the high-pressure chamber 22a, the diameter d of the pressure receiving surface of the timer piston 23 is equal to the diameter of the pressure receiving surface of the timer piston 23 when the timer piston 23 is leaning toward the low-pressure chamber 22b. It is set to be smaller than D.

Also, the roller holder 2, the timer control valve 21
Besides, a cold advance mechanism 4 for forcibly advancing the fuel injection timing when the engine water temperature is low (cold) is provided. The specific structure of this mechanism 4 is as follows. 6 to 8
In each figure. That is, the mechanism 4 for advancing at the time of cold includes a rotating shaft 42 having an eccentric pin 41, a rotating lever 43 that rotates integrally with the rotating shaft 42, and an urging spring.
44 and an operation lever 45 are provided. The eccentric pin 41 is loosely inserted into the notch 2a formed in the roller holder 2, and when the engine is stopped, that is, in the state shown in FIG. It is applied to the end face. The operation lever 45 is pulled in the direction of arrow B in FIG. 8 when it is cold. When the operation lever 45 is pulled, the spring force F of the biasing spring 44 acts on the rotation lever 43. Accordingly, the rotating lever 43 is urged in the direction of arrow C in FIG. 8, and accordingly, the amount of eccentricity of the eccentric pin 41 is further increased in the direction of arrow E in FIG. 42 will be activated.

When the operation lever 45 is pulled from the state shown in FIG. 6, that is, the engine is stopped, the amount of eccentricity of the eccentric pin 41 is reduced by the spring force F of the urging spring 44 as described above.
In the figure, the rotating shaft 42 is urged to be further increased in the direction of arrow E, and the spring force F of the urging spring 44 urges the roller holder 2 in the advance direction (the direction opposite to the direction of arrow A). It acts as a biasing force.

When the rotation speed increase from the engine cranking, while the rotation speed Ne of the engine to exceed a first set rotation speed N _1, since the pump chamber discharge pressure introduced into the high pressure chamber 22a is low, the roller holder 2 advances The force for urging in the angular direction, that is, the urging spring
High pressure chamber 22a pressure P due to spring force F of 44 and pump chamber discharge pressure
And the roller holder 2 is advanced by the resultant force (arrow A).
6), the spring force G of the timer spring 25 prevails, and the roller holder 2 is maintained in the state shown in FIG. Therefore, the function as the advance suppression means is exhibited,
When the rotation speed increase from the engine cranking, while the rotation speed Ne of the engine to exceed a first set rotation speed N ₁ is such fuel injection timing is not advanced. During this time,
Since the roller holder 2 does not move, the rotation of the rotation shaft 42 and the rotation lever 43 is restricted by the roller holder 2 even if the operation lever 45 is pulled.

Thereafter, the rotation speed Ne of the engine exceeds a first predetermined rotational speed N _1, the pump chamber discharge pressure introduced into the high pressure chamber 22a is increased, the pressure P is increased in the high-pressure chamber 22a with the pump chamber discharge pressure, the High-pressure chamber 22a pressure P and spring force F of biasing spring 44
Is greater than the spring force G of the timer spring 25, and the roller holder 2 is moved in the advance direction. Therefore, to exhibit the function as the advance start means, when the rotation speed increase from the engine cranking, the rotational speed Ne of the engine exceeds the first set rotation speed N _1, the fuel injection timing is a predetermined amount the advance Will be done. During this time, since the roller holder 2 is moved in the advance direction, the rotation shaft 42 and the rotation lever 43 also rotate according to the movement of the roller holder 2.

When the rotation lever 43 rotates by a predetermined amount as shown by a two-dot chain line in FIG. 8, the rotation lever 43 comes into contact with the stopper 5 to stop the rotation. When the rotation lever 43 comes into contact with the stopper 5 in this manner, the spring force F of the urging spring 44 is received by the stopper 5 so that the spring force F of the urging spring 44 does not act on the roller holder 2. Become. For this reason, when this state is reached, the high pressure chamber 22a pressure P due to the pump chamber discharge pressure
The roller holder 2 does not move until the pressure G alone exceeds the spring force G of the timer spring 25. Therefore, when this state is reached, the engine speed
Even Ne rises, the fuel injection timing is to be kept constant (Figure 4, the advance amount between the first set rotation speed N ₁ and the second set rotation speed N ₂ is constant It is in a state where it is kept).

When the rotation speed Ne of the engine is exceeding the second set rotation speed N _2, now outweigh the spring force G of the timer spring 25 high-pressure chamber 22a pressure P by the pump chamber discharge pressure alone, shown in FIG. 7 Thus, the roller holder 2 is further moved in the advance direction. Thereafter, as the pressure P of the high-pressure chamber 22a increases due to the increase in the engine speed Ne, the advance amount of the fuel injection timing also increases.

Further, in this embodiment, when the timer piston 23 is close to the high pressure chamber 22a as described above, the diameter d of the pressure receiving surface of the timer piston 23 is
The diameter D of the pressure receiving surface of the timer piston 23 when approaching the side 22b is smaller than the diameter D. For this reason, even if the pump chamber discharge pressure is the same, the pressure P of the high-pressure chamber 22a is higher when the timer piston 23 is closer to the low-pressure chamber 22b than when the timer piston 23 is closer to the high-pressure chamber 22a. . Therefore, the rotation speed Ne of the engine is the rotation speed Ne of the engine after the timer piston 23 beyond once the first set rotation speed N ₁ is shifted to the low-pressure chamber 22b side is lowered to the first predetermined rotational speed N ₁ or less , high-pressure chamber 22a pressure at this time, until the rotational speed Ne of the engine rotation speed increase when the engine exceeds a first predetermined rotational speed N ₁ (timer piston 23 at this time is a high pressure chamber 22
The pressure is maintained higher than the pressure of the high-pressure chamber 22a (which is closer to the a side), so that the timer piston 23 does not move toward the high-pressure chamber 22a, and the fuel injection timing is maintained in a state advanced by a predetermined amount. Become.

As described above, the mechanism of this embodiment also
Characteristics similar to the advance angle characteristics shown in FIG. 4 can be obtained, and effects similar to those of the above embodiment can be obtained.

[Effect of the invention]

The fuel injection timing control device for a diesel engine according to the present invention allows fuel injection to be started from a specific basic advance start rotation speed during a warm state, while the fuel injection timing control device performs the above-described basic advance start rotation speed during a cold start. The fuel injection timing is not advanced until the set rotational speed is reached, and the advance is started from the set rotational speed, based on a set rotational speed that is lower than the idle rotational speed. For this reason, until the above-mentioned set number of revolutions is reached during cold start, fuel is injected at a time when a large explosive force for pushing down the piston is obtained, so that a sufficient inertia force is quickly applied to the piston. As a result, the starting time during the cold start is reduced. In addition, after the inertia force of the piston is sufficiently provided, when the engine is cold, the advancing means operates to advance the fuel injection timing by a predetermined amount. Therefore, even when the engine is cold, the fuel is sufficiently vaporized by the time of ignition, and when the engine temperature is low at low engine speeds such as idling after the start, the warm-up is promoted and the misfire occurs. Is prevented, and stable combustion can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a fuel injection timing control apparatus for a diesel engine according to the present invention, FIG. 2 is a cross-sectional view showing a specific configuration thereof, and FIG. 3 is a specific example of control of a control unit. FIG. 4 is a graph showing the relationship between the engine speed and the amount of advance of the fuel injection timing; FIG. 5 is a graph showing the relationship between the elapsed time after engine start and the engine speed; 6 and 7 are sectional views showing another embodiment, and FIG. 8 is a side view showing the operation lever and the rotation lever. 31 ... Advancing means, 32A ... Advancing suppression means, 32B ... Advancing start means.

Claims (2)

(57) [Scope of request for utility model registration] 1. The fuel injection timing advance control is started from a specific basic advance start rotation speed higher than the idling rotation speed in a warm state, while the fuel injection timing is controlled in a low rotation range below a predetermined rotation speed in a cold state. In the diesel engine provided with an advancing means for advancing a predetermined amount, the set rotation speed is lower than the basic advance start rotation speed and higher than the idling rotation speed when the rotation speed increases from engine cranking in a cold state. Up to this point, there is provided an advance suppression means for stopping the operation of the advance means to stop the advance of the fuel injection timing, and an advance start means for starting the operation of the advance means from the set number of revolutions. A fuel injection timing control device for a diesel engine. 2. The diesel engine according to claim 1, wherein the operation of the advancing means is performed even in an area of an idling speed or less while the operation is continued after the operation of the advancing means is started. Fuel injection timing control device.