JPS6357828A - Fuel injection controller for diesel engine - Google Patents

Abstract

PURPOSE:To aim at abatement in a Diesel knock at the time of low speed and low load, by detecting specific lift of a plunger for a fuel injection pump, and controlling operation timing of a solenoid valve for adjusting fuel pressure in making it correspond to the detected specific lift. CONSTITUTION:At the time of rotation of a drive shaft 2 to be driven by an engine, of a fuel injection pump, output signals N1 and N2 out of both first and second signal detectors 4 and 5 installed face-to-face with a ring member 3 is inputted into an electronic control unit 9. At this time, the signal N1 is used as a reference signal and the signal N2 as a specific lift position signal of a plunger 17, respectively, and a phase difference between both signals N1 and N2 is adjusted by a solenoid valve 8 in a timer unit by the ECU 9 so as to come to the preset phase difference. And, at the engine driving, the plunger 17 is lifted up to the specific lift whereby pilot injection is carried out, and when it is reached to the specific lift and the signal N2 is outputted, it is controlled so as to energize the solenoid valve 8 with a continuous rating current.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fuel injection control device for a diesel engine, and more particularly to an improvement in a fuel injection control device for a diesel engine suitable for use in an electronically controlled diesel engine.

[Conventional technology]

Conventionally, a fuel injection pump for injecting fuel into a diesel engine has a face cam and a roller for converting the rotational motion of a pump drive shaft into a reciprocating motion of a plunger for pumping fuel, and a roller for holding the roller. a timer piston for changing the starting position of the compression stroke of the plunger by rotating the roller ring and rotating the roller relative to the drive shaft; and a timer piston acting on the timer piston. a solenoid valve for adjusting fuel pressure and controlling fuel injection;
There are some that are equipped with. As a technology related to a fuel injection device that controls the fuel injection pump as described above to perform proper fuel injection to a diesel engine, there is a technology proposed in Japanese Patent Application Laid-Open No. 56-126630 and Japanese Utility Model Application Publication No. 60-26243. be. That is, the technique tfi disclosed in Japanese Patent Application Laid-Open No. 56-126630
detects an idle operating state and performs synchronous control of a pulse drive signal for controlling the valve means such that each fuel injection period is included in the opening period of the valve means for controlling the pressure applied to the timer piston. This is a fuel injection device that can reduce noise during idling operation without causing the engine to run out of power. Furthermore, the technology disclosed in Japanese Utility Model Application Publication No. 60-26243 relates to a device in which the driving reaction force of the plunger is absorbed by the movement of the timer piston (rotation of the roller ring) in the plunger feeding process, thereby lowering the injection rate. It is something.

[Problems to be Solved by the Invention] However, in the technique disclosed in JP-A-56-126630, since the fuel injection period during idling is included in the opening timing of the solenoid valve, it is difficult to keep the injection rate low. However, pilot injection is not possible. Further, there is a problem in that the injection pressure temporarily decreases immediately after the injection valve is opened, and the atomization of the fuel deteriorates at that time. In addition, the technology disclosed in the above-mentioned Utility Model Application Publication No. 60-26243 is
Because of the complicated structure of the outer piston, it not only has poor manufacturing properties but also has disadvantages in terms of cost and furthermore has problems such as poor control accuracy.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and has three objects: to provide a fuel injection control device for a diesel engine that has a relatively simple configuration and is capable of lowering the injection pressure immediately after the start of fuel injection. do.

[Means to solve the problem]

The present invention includes a face cam and a roller for converting the rotational motion of a pump drive shaft into a reciprocating motion of a plunger for pumping fuel, a roller ring for holding the roller, and a roller ring that rotates the roller ring. A timer piston for changing the start phase of the compression stroke of the plunger by rotating the roller with respect to the drive shaft, and controlling fuel injection by adjusting the fuel pressure acting on the timer piston. A diesel engine fuel injection control device for controlling a fuel injection pump comprising: a means for detecting a specific lift of the plunger; and an actuation of the electromagnetic valve in response to the detected specific lift. The above object is achieved by providing a means for controlling the timing.

[Effect]

In the present invention, in a fuel injection control device for a diesel engine for controlling a fuel injection pump, a specific lift of a plunger of the fuel injection pump is detected, and the fuel pressure is adjusted in accordance with the detected specific lift. of $
;, l1ll& controls the operation timing of the valve. Therefore, with a relatively simple configuration, the injection pressure can be lowered immediately after the start of fuel injection, making it possible to perform pilot injection by lowering the fuel injection rate at low speeds and light loads, and increasing the fuel injection rate during other operating periods. It becomes possible to control. Therefore, in general, in diesel engines, when the fuel injection rate is high at low speeds and under light loads, not only does combustion noise, so-called diesel knock, increase, but also NOx in the exhaust increases, and when the fuel injection rate is low at high loads, However, by applying the present invention, the performance of the diesel engine at high loads and high speeds does not deteriorate, and diesel knock at low speeds and low loads is reduced. At the same time, NOx in exhaust gas can be suppressed.

【Example】

EMBODIMENT OF THE INVENTION Hereinafter, embodiments of a fuel injection control device for a diesel engine according to the present invention will be described in detail based on the drawings. Figure 1 shows the main parts of the fuel injection pump according to this embodiment! This is an I cross section. Figure 2 shows ■-■ in Figure 1.
FIG. That is, in the figure, the drive shaft 2 supported by the pump housing 1 is a diesel engine (not shown).
is connected to. The key 11 is on the drive shaft 2.
A known vane-type feed pump 12 is mounted to rotate coaxially with the drive shaft 2. Further, the vane type feed pump 12 pumps fuel flowing in from the supply passage 13 into the pump housing chamber 14 at a predetermined pressure determined by a pressure regulating valve (not shown). Further, a face cam 16 is coupled to the drive shaft 2 via a coupling 15 so as to be integral in the rotational direction and to be movable in the reciprocating direction. A plunger 17 is integrally connected to the face cam 16. Further, a roller ring 10 on which a roller 18 with which the face cam 16 comes into contact is disposed, is engaged with a timer piston 7 by a slide pin 6. This timer piston 7 is urged toward the high pressure chamber 19 by a spring 21 housed in the low pressure chamber 20. The high pressure chamber 19 and the low pressure chamber 20 are communicated through a passage 22, and a two-way solenoid valve 8 is provided in the middle of the passage 22. Furthermore, a ring member 3 is coaxially attached to the drive shaft 2 and has a signal generating section formed of a plurality of protrusions on the outer periphery. Opposing the ring member 3, a first signal detector 4 is attached to the pump housing 1, and a second signal detector 5 is attached to the roller ring 10. The first and second signal detectors 4.5 detect the signal generating portion of the ring member 3 and output the output signals N1 and N2, which are sent to an electronic control unit (hereinafter referred to as EC) along with engine load signals and the like.
(referred to as U) 9. The solenoid valve 8 is driven by the output signal of the EC1J9. The effects of the embodiment will be explained below. The plunger 17 is rotationally driven by the rotation of the drive shaft 2, and reciprocates in the left-right direction in FIG. 1 according to the cam curve of the face cam 16 every time the face cam 16 rides on the roller 18 in contact with it. As a result, the plunger 17 performs a rotational reciprocating motion and sucks in fuel.
The fuel is compressed and distributed to injection nozzles (not shown) in predetermined cylinders of the engine. At this time, the timer piston 7 is positioned based on the balance between the pressure in the high pressure chamber 19 to which the fuel pressure in the pump housing chamber is introduced, the pressure in the low pressure chamber 20, and the biasing force of the spring 21. Further, the pressure between the high pressure chamber 19 and the low pressure chamber 20 is controlled by inputting an output signal of a certain drive frequency from the ECU 9 to the solenoid valve 8, controlling the energization ratio of the solenoid valve 8, and adjusting the effective cross section of the passage 22. controlled by By the way, when the energization ratio is high, the amount of fuel flowing through the passage 22 increases, the pressure in the high pressure chamber 19 decreases, and the timer displacement becomes small as shown in FIG. Move to the right. Conversely, when the energization ratio is low, the amount of flowing fuel fl decreases and the timer displacement increases, so the timer piston 7 moves to the left in the figure. This movement of the timer piston 7 is converted into a movement of the roller ring 3 in the rotational direction via the slide bin 6. Therefore, when the energization ratio is high and the timer piston 7 moves to the right in FIG.
Since the relative position between the roller 18 and the roller 18 changes, the fuel injection timing is retarded. The position of the timer piston 7 that moves as described above is
It is calculated and determined by the ECU 9 according to the engine speed and load. In this case, the ECU 9 performs feedback control on the position of the timer piston 7 so that the phase difference between the signals output from the first signal detector 4 and the second signal detector 5 becomes a predetermined phase difference. are doing. By the way, in this example, in order to apply the present invention,
The second signal detector 5 faces the signal generating portion of the ring member 3 and outputs a signal when the face cam 16 reaches a specific position, that is, the plunger 17 reaches a specific lift. Further, the energization time of the electromagnetic valve 8 is synchronized with the timing of detecting the signal generating section of the second signal detector 5. Therefore, this embodiment has the following effects. When the face cam 16 is driven by the drive shaft 2 and rides on the abutting roller 16, and the plunger 17 is moving rightward in FIG.
However, due to the reaction force of this movement, the receiver is about to be rotated in the counterclockwise direction indicated by the arrow in FIG. This roller ring 10
This movement is transmitted to the timer piston 7 via the slide pin 6, and the timer piston 7 is about to be moved rightward in FIG. When the solenoid valve 8 closes the passage 22, the high pressure chamber 19 is a closed space, and the fuel filled in the high pressure chamber 19 is almost incompressible, so that the above-mentioned drive is not performed. Even if it receives a reaction force, the timer piston 7 hardly moves to the right in the figure. On the other hand, when the electromagnetic valve 8 opens the passage 22, the fuel in the high pressure chamber 19 can flow into the low pressure chamber 20 through the passage 22. Therefore, when receiving the driving reaction force, the timer piston 7 Move to the center right. When the timer piston 7 moves to the right, the roller 18 moves in the direction of rotation of the face cam 16, and as a result, the lift of the plunger 17 is suppressed. As described above, there is a close relationship between the opening and closing of the solenoid valve 8 and the lift of the plunger 17. In the embodiment, since the energization time to the solenoid valve 8 is synchronized with the specific lift of the plunger 17, the plunger 17 is
It is possible to suppress the fuel pumping rate, that is, the fuel injection rate. The above relationship is expressed as the lift L of the plunger 17 with respect to time.
D, output signal N 1 of the first and second signal detector 4.5
+N 2 , the drive signal SV of the electromagnetic valve 8, and the injection rate QV. The time axis in FIG. 0, which will be explained based on FIG. 4, is the cam angle axis. In this case, the signal N1 is detected as a reference signal unrelated to the lift Lp of the plunger 17, and the signal N2 is detected as a specific lift position of the plunger 17. Further, the phase difference τC between the signals N + and N 2 is adjusted by the electromagnetic valve 8 controlled by the ECU 9 so as to have a predetermined phase difference. This solenoid valve 8 is controlled by a drive signal Sv from the ECU 9, and the drive signal Sv is synchronized with the signal N2. First, pilot injection is performed by lifting the plunger 17 to a specific lift. When the specific lift is reached, the second signal detector 5 outputs a signal N2. When the solenoid valve 8 is energized based on this signal N2, the timer piston 7 moves due to the drive reaction force, so the lift of the plunger 17 is suppressed and the fuel injection rate Qv is kept low as shown in FIG. 4. It happens. Furthermore, fuel is additionally injected by lifting the plunger 17. In this case, the degree of suppression of the injection rate Qv is determined by the timer piston 7.
That is, the escape velocity is adjusted to 1 liter by the high pressure side orifice in the timer piston 7 and the fuel passage area of the solenoid valve 8. In addition, in a diesel engine, the angle is generally set to the advance side when the load is high. That is, since the energization ratio to the solenoid valve 8 is set small, the escape amount of the timer piston 7 is small, and the fuel injection rate Qv does not become too low during high load. On the other hand, at high speeds, the timer piston 7 is set to the advance side in order to compensate for the delay in pumping in the high-pressure injection system, so the injection rate is maintained high for the same reason as described above. Moreover, even if the energization ratio to the solenoid valve 8 is the same, at high speed, the amount of fuel fl flowing out from the high pressure chamber 19 to the low pressure chamber 20 via the solenoid valve 8 is small and due to the drive reaction force. Because the suppression effect of plunger lift is small,
The fuel injection rate Qv will be maintained high. In the above embodiment, by synchronizing the start time of energization to the solenoid valve 8 with the signal detection time of the second signal detector 5, the injection rate at low speed and light load can be suppressed, and pilot injection can be performed. It became. At the same time, it was also possible to automatically increase the fuel injection rate during high loads or high speeds. However, under operating conditions where it is not necessary to lower the fuel injection rate, the timing to start energizing the solenoid valve 8 can also be set outside the fuel pumping process by the plunger 17. In the above embodiments, the present invention was applied to a fuel injection pump having the configuration shown in FIGS. 1 and 2. However, the fuel injection pump to which the present invention is applied has the configuration shown in FIGS. It is clear that the present invention is not limited to this, but can be applied to other fuel injection pumps.

【Effect of the invention】

As explained above, according to the present invention, the injection pressure can be lowered immediately after the start of fuel injection with a relatively simple configuration, so the fuel injection rate can be lowered to enable pilot injection at low speeds and light loads, and other In the operating range, it becomes possible to control the fuel injection rate highly. Therefore, without causing deterioration of diesel engine performance at high loads and high speeds,
Excellent effects such as reducing diesel knock at low speeds and low loads and suppressing NOx in exhaust gas can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of a fuel injection pump in which a fuel injection control device for a diesel engine according to the present invention is implemented, and FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 3 is a diagram showing an example of timer change with respect to the energization ratio to explain the action of the embodiment marked #, and FIG. FIG. 3 is a diagram showing an example of the relationship between injection rates. DESCRIPTION OF SYMBOLS 1... Pump housing, 2... Drive shaft, 3... Ring member, 4... First signal detector, 5... Second signal detector, 6... Slide bin, 7...Timer piston, 8...Solenoid valve, 9
...Electronic control unit (ECU), 10...Roller ring, 16...Face cam, 17...
Plunger, 18...Roller, 19...
High pressure chamber, 20...low pressure chamber, 22... passage.

Claims (1)

[Claims] (1) A face cam and a roller for converting the rotational motion of the pump drive shaft into a reciprocating motion of a plunger for pumping fuel, a roller ring for holding the roller, and a roller ring that rotates the roller ring to rotate the roller. a timer piston for changing the start phase of the compression stroke of the plunger by rotating the piston with respect to the drive shaft; and an electromagnetic piston for controlling fuel injection by adjusting the fuel pressure acting on the timer piston. A fuel injection control device for a diesel engine for controlling a fuel injection pump comprising: a means for detecting a specific lift of the plunger; and means for controlling an actuation timing of the electromagnetic valve in response to the detected specific lift. A fuel injection control device for a diesel engine, comprising: means for controlling;