JPS5818528A - Fuel injection device of diesel engine - Google Patents

Abstract

PURPOSE:To obtain a good combustion state, in the captioned device equipped with an oil pressure controller decreasing oil pressure and delaying fuel injection timing when an engine is low loaded, by detecting misfiring of the engine and reducing a function of decreasing said oil pressure when the misfiring is detected. CONSTITUTION:When an engine is low loaded, a governor spring 39, connected with one end 43 to a turning shaft 42 of a control lever 41 interlocking to an accelerator pedal, is provided with small tension, and a governor sleeve 23 is moved upward by fly weights 20, then pressure in a pump chamber 4 is decreased. In accordance with the above, pressure in a pressure oil chamber 52 of a timer 44 is also decreased, and a timer piston 46 is pulled back to a delay side by a spring 49. Here the engine misfires, and a misfire detector 53 detects misfiring to excite a solenoid valve 28, if a relief passage 27 is closed, reduction of pressure in the pump chamber 4 is stopped, and injection timing can be set to an advance side even at a low and medium load.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a diesel engine.

Conventionally, diesel engine fuel injection systems have been designed to delay the fuel injection timing during low and medium loads to reduce NOx and noise, while advancing the fuel injection timing during high loads to ensure sufficient output. It has been proposed to install a so-called road timer, which is a device that adjusts the fuel injection timing according to changes in load.

However, in a diesel engine that uses such a device, even if the engine is cold, the fuel injection timing is delayed at low or medium load, so the combustion state is affected when the engine is cold. It got worse,
There is a problem that a so-called half-misfire phenomenon occurs.

Furthermore, when the diesel engine is operated at high altitudes where the atmospheric pressure has decreased, the amount of air filling the combustion chamber decreases and the ignition delay increases, resulting in incomplete combustion and combustion, especially when the engine is under low load. The fuel injected into the chamber is discharged unburnt into the exhaust gas, causing a half-misfire phenomenon as described above.

Therefore, in order to solve the above problem, in our previous application, we developed a cam device that reciprocates the plunger that pumps fuel, and adjusts the fuel injection timing by operating the cam device with oil pressure that corresponds to the engine rotation speed. A fuel injection device for a diesel engine, which is equipped with an injection timing adjustment device that controls the temperature of the engine, and a hydraulic control device that lowers the pre-pressure hydraulic pressure to delay the fuel injection timing when the engine load is low, includes a temperature detection device that detects the temperature state of the engine; , a restriction device is provided to reduce the oil pressure lowering function of the hydraulic control device, and when the temperature detection device confirms that the engine is cold, the restriction device reduces the oil pressure lowering function of the hydraulic control device. A fuel injection device for a diesel engine that eliminates the above-mentioned conventional drawbacks by
(Specification of No. 1), a pressure detection device for detecting atmospheric pressure is provided in place of the temperature detection device, and when the pressure detection device detects that the atmospheric pressure has decreased, a restriction device is activated,
Similarly to the above, a diesel engine fuel injection device (Utility Application No. 156545/1984) has been proposed which eliminates the conventional drawbacks.

However, in diesel engines, so-called semi-misfire conditions occur when operating at high altitudes or when
It is not a phenomenon that occurs only when the engine is cold, and
It is not a phenomenon that always occurs at high places or in cold weather.

Therefore, the present invention has been made in consideration of the above points, and uses the temperature detecting device or the pressure detecting device in the improved technique as a misfire detecting device, and when a misfire occurs, activates a limiting device to control the hydraulic control system. It is an object of the present invention to provide a fuel injection device for a diesel engine that reliably eliminates the above-mentioned conventional drawbacks by reducing the oil pressure lowering function of the fuel injection device.

Hereinafter, the present invention will be explained in detail based on drawings showing embodiments.

In the distribution type fuel injection pump l shown in FIGS. 1 and 2, 2 is a housing, 3 is a drive shaft that is driven at 1/2 the rotation speed of the engine crankshaft (not shown), and 4 is installed in the housing 2. formed pump chamber, 5
is a suction passage that connects the pump chamber 4 to a fuel tank (not shown). 6 is a vane type feed pump interposed in the middle of the suction passage 5, and is driven by the drive shaft 3. By driving the feed pump 6, the fuel from the fuel tank flows through the suction passage 5 into the pump chamber 4.
The internal pressure within the pump chamber 4 is increased as the drive shaft 30 rotation speed, that is, the engine rotation speed increases.

A pump/distribution plunger 7 is slidably inserted into a sliding hole 8 formed in the nozzle 2. A cam disk 9 on which a cam surface 9a having a number of peaks corresponding to the number of cylinders of the engine is formed is integrally connected to the end of the plunger 7, and the drive shaft 3 is connected to the driving disk. (not shown).

Reference numeral 10 denotes a roller holder, which is provided rotatably and concentrically with the drive shaft 3 inside the No-Ujifugu 2, and has the same number of rollers 11 as the number of ridges on the cam surface 9a of the cam disk 9' (i.e., the number corresponding to the number of cylinders). is held rotatably.

The cam surface 9a of the cam disc 9 is pressed against the roller 11 by a plunger ring (not shown), and as the cam disc 9 rotates on the roller 11,
The plunger 7 is configured to simultaneously perform reciprocating motion for sucking and pumping fuel and rotational motion for distributing fuel.

Therefore, when the plunger 7 is in the suction process (downward movement in FIG. 1), the fuel in the pump chamber 4 is transferred from the supply passage 12 formed in the housing 2 to the plurality of vertical lines provided on the outer peripheral surface of the head of the plunger 8. It is fed into the plunger chamber 29 via one of the grooves 18 (four in this example). Also, plunger 7
When the pressure transitions to the pumping process (increasing movement in FIG. 1), the communication between the supply passage 12 and the vertical groove 13 is severed, and the plunger chamber 2
9 is compressed and passes from the vertical hole 14 formed in the plunger 7 to the distribution horizontal hole 15, and has reverse upward valves 16 formed in the No-Ujifugu 2 in a number corresponding to the number of cylinders in the circumferential direction. The fuel is supplied to one of the discharge passages 17 and injected into the cylinder from an injection nozzle (not shown).

Reference numeral 18 denotes a cut-off sleeve, which is provided at a portion of the plunger 7 that protrudes toward the pump chamber 4 side, and is provided with a vertical hole 1 of the plunger 7;
The cant-off port 19 communicating with the cant-off port 19 is slidably fitted on the outside so as to open and close. This cut-off sleeve 18
The cant-off boat 19 comes off from the upper edge of the pump chamber 4.
When opened, fuel flows into the pump chamber 4 and the discharge passage 1
Discharge to 7 is stopped and the injection path is established.

A flyweight 20 is provided in a flyweight holder 30 that is integrally fixed to the gear 21. This holder 30 is attached to the governor shaft 22, and is driven by a drive shaft 3 to which a gear (not shown) that meshes with the gear 21 is fixed. Also, fly weight 20
The movement is transmitted to the governor sleeve 23 which is slidably fitted over the small diameter portion of the governor shaft 22. A relief boat 24 is provided in the governor sleeve 23, and when the governor sleeve 23 is in a low/medium load position with a small amount of fuel injection, the boat 24 (communicates with the horizontal hole 25 of the governor shaft 22, thereby , the pump chamber 4 is connected to the suction side (low pressure side) of the feed pump 6 via the relief port 24, the horizontal hole 25, the vertical hole 26 of the governor shaft 22, and the relief passage 27. 28 is the relief passage 27. The solenoid valve is an example of a restriction device that opens and closes the passage 27, and is connected to a power source via a misfire detection device 53.

As the misfire detection device 53, there is a device that detects a misfire by detecting engine vibration, combustion pressure, exhaust gas temperature, or exhaust sound, but in the embodiment, a device that detects a misfire from engine vibration is applied. are doing.

That is, as shown in FIG. 3, the misfire detection device 53 includes a vibration converter 54, a low-pass filter 55, a pulse converter 56, and a
It is composed of a /A converter 57 and a switching circuit 58.

During normal combustion (operation) without misfire, the vibration converter 54 outputs an output voltage (a). When the engine is rotating at a high speed, its vibration frequency becomes high, and the high frequency is cut by the low-pass filter 55, resulting in the output as shown in (b). Therefore, since the input to the pulse converter 56 is below the trigger level, the number of output pulses is zero.
The switching circuit 58 is inactive and closed, and the solenoid valve 28
is energized, opening the relief passage 27, and the movement of the governor sleeve 23 closes the pump chamber 4 at low and medium loads.
The fuel injection timing is adjusted to the delayed side by lowering the fuel pressure (hydraulic pressure) inside and moving a timer piston 46, which will be described later. On the other hand, when the engine misfires, torque fluctuation occurs in the engine due to the misfire, and the engine includes a lower vibration frequency than during normal operation, so the output of the vibration converter 54 has a waveform of (d7). This waveform is a combination of the low-frequency vibration frequency during a misfire and the high-frequency vibration frequency during normal operation.)
. Since the low-pass filter 55 passes only the low frequency components associated with misfire, 1. The output waveform is (e), and as a result,
Pulse converter 56 outputs a pulse (f). In this way, when a misfire occurs, a pulse (f) is generated due to the low frequency input accompanying the torque fluctuation due to the occurrence of the misfire. Then, the number of pulses is converted into an analog quantity by the D/A converter 57, the output voltage changes according to the number of pulses, the switching circuit 58 is opened, and the solenoid valve 28 is demagnetized to open the relief passage 27. close.

Therefore, the relief port 24 of the governor sleeve 23
Even during low/medium load conditions where the fuel pump 4 is in communication with the horizontal hole 25 of the governor shaft 22, the oil pressure in the pump chamber 4 does not decrease and the injection timing is advanced from that during normal operation.

81t, in the governor lever assembly, one end of a tension lever 33 and a start lever 34 are pivotally supported on a collector lever (not shown) by a pin 35, and one end of the start lever 34 is supported by a Bekat off sleeve 18.
A radbin 37 is attached to the ball that is engaged with the engagement groove. 38 is a start spring fixed to the other end of the start lever 34, a finger 39 interposed between the levers 33 and 34 is a governor spring, and one end of the finger is connected to the tension lever 33 through a pin 40. The other end is a control lever 41 that is connected to an accelerator pedal (not shown).
is connected to a rotation shaft 42 via a shackle 43. The position of the cutoff sleeve 18, ie, the amount of fuel injected, is determined by the rotation angle of the control lever 41 and the centrifugal force (engine rotation speed) of the flyweight 20.

44 is a timer for controlling the fuel injection timing, and has a timer piston 46 that slides inside a cylinder 45 formed inside the No-Uji Fugu 2. This timer piston 46 is
It is connected to the roller holder 10 via a lever 48 that is swingable about a fixed shaft 47. Further, a first hydraulic chamber 750 is formed on one side of the cylinder 45 with the timer piston 46 in between, in which a spring 49 is fully compressed, and on which fuel pressure on the suction side of the feed pump 6 acts, and on the other side, a first hydraulic chamber 750 is formed with the timer piston 46. A second hydraulic chamber 52 is formed to which the fuel pressure of the pump chamber 4 acts via a hydraulic passage 51 provided in the piston 46 . The differential pressure between the first hydraulic chamber 50 and the second hydraulic chamber 52, that is, the fuel pressure corresponding to the engine speed, and the elastic force of the springs 4 and 90 control the position of the timer piston 46, that is, the lever 48. Since the circumference of the roller holder lO and the contact position with the cam 9 and 9a change; a relative change occurs between the circumferential phase of the drive shaft 3 and the contact position, that is, the operating position of the plunger 7. As the feed pressure of the feed pump 6 increases, that is, the engine speed increases, the fuel injection timing advances.

With the above configuration, when the engine is operating normally, the switching circuit 58 of the misfire detection device 53 is closed and the solenoid valve 28 opens the relief passage 27. Therefore, when the engine load is small, the tension of the governor gel cylinder 89 is weak, so the flyweight 20 moves the governor sleeve 23 upward (in FIG. 1), and the horizontal hole 25 of the governor shaft 22 and the governor sleeve 23 The relief ports 24 of the pump chamber 4 coincide with each other, and the pump chamber 4 is communicated with the feed pump upstream (low pressure side) via the relief passage 27, so that the pressure inside the pump chamber 4 is reduced. Along with this, the pressure in the second hydraulic chamber 52 of the timer 44 also decreases, so the timer piston 46 is pulled back to the delay side by the elastic force of the spring 49.

When the engine load exceeds the set value and the fuel injection amount increases, the governor sleeve 23 moves downward (in FIG. 1), and the relief boat 24 and the horizontal hole 2 of the governor shaft 22 move.
5 is separated, communication between the pump chamber 4 and the feed pump upstream (low pressure side) is cut off, and the pressure inside the pump chamber 4 increases. Along with this, the pressure in the second hydraulic chamber 52 of the timer 44 also increases, so that the timer piston 46
It moves toward the advancing side against the elastic force of 9.

On the other hand, if the engine misfires, the solenoid valve 2
8 is not excited and closes the relief passage 27. As a result, the pressure inside the pump chamber 4 does not decrease, and the fuel injection timing is maintained at the advance side without delay even during low and medium loads, as in the case of high loads. Therefore, even if the ignition delay time increases, a good combustion state can be maintained and half-misfires can be prevented.

Figures 4 and 5 show the above operation in terms of the relationship between engine load or engine speed and fuel injection timing.
It is a diagram. First, FIG. 4 shows the relationship between the load and the injection timing when the engine speed is constant, where the solid line A shows the change during normal operation, and the broken line B shows the change during misfire operation.

Further, in FIG. 5, the solid line C shows changes during normal operation at high load and during misfire operation, and the solid line C shows changes at low and medium loads during normal operation.

In the embodiment described above, the solenoid valve 28 is used as a restriction device to completely close the relief passage 27 during operation in a misfire condition, but the passage area of the relief passage 27 is reduced to a set amount. It can be anything. Alternatively, the passage area of the relief passage 27 is made variable depending on the degree of misfire,
The passage area of the relief passage may be reduced as misfires are reduced. In this case, relief passage 2
The degree of reduction in the area of the 70 passages may be set within the range of injection timing that allows for good combustion at low loads during misfires.

As described above, the present invention is configured such that the oil pressure reduction function of the oil pressure control device that delays the fuel injection timing by reducing the oil pressure acting on the injection timing adjustment device when the engine load is small is reduced when the engine misfires. Therefore, even if the ignition delay time increases in the event of a misfire, the fuel injection timing can be easily corrected to the advanced side, resulting in good combustion and preventing half-misfires, which has excellent practical effects. It is.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention, in which FIG. 1 is a longitudinal sectional view of a fuel injection device for a diesel engine, and FIG. 2 is a view taken at n-1 of FIG. 1! 3 is a diagram illustrating the misfire detection device and its operation, FIG. 4 is a diagram showing engine load and fuel injection timing, and FIG. 5 is a diagram showing the relationship between engine rotation speed and fuel injection timing. 1... Distribution type fuel injection pump, 7... Plunger,
9...Cam disc, lO...Roller holder, 23
... Governor sleep, 24 ... Relief port, 2
7... Relief passage, 28... Solenoid valve (limiting device)
, 44... timer, 53... misfire detection device.

Claims (1)

[Claims] (1) Equipped with an injection timing adjustment device that adjusts the timing of fuel injection by acting on oil pressure corresponding to the engine rotation speed, and a hydraulic control device that reduces the oil pressure and delays the fuel injection timing when the engine load is small. A fuel for a diesel engine, characterized in that a misfire detection device for detecting a misfire in the engine is provided, and the misfire detection device is linked to a restriction device that reduces a hydraulic pressure lowering function of the hydraulic control device when the engine misfires. Injection device.