JPS58165551A - Vibration reducer for diesel engine - Google Patents

Abstract

PURPOSE:To promote the ignition of fuel through a device which closes an intake air throttle valve and supplies electricity to a heater to reduce the vibration of an engine in its low speed and load operation, by causing spark discharge at the time of decrease of intake air to aid the ignition of the fuel injected. CONSTITUTION:In the low speed and load operation of an engine, an intake air throttle valve 2 is closed and a heater 10 is supplied with electricity to diminish the compression work of the engine to suppress its vibration. When the output of a sensor 24 which corresponds to the vibration of the engine body 23 and is applied to a controller 22 has exceeded a prescribed level, ignition pulses are supplied to a switching circuit 21 to cause a high-voltage ignition current to flow through the secondary winding of an ignition coil 17 and be applied to an igniter 16 through a distributor 18. Spark discharge is thus caused between the central and peripheral electrodes of the igniter 16 to aid the ignition of fuel injected from a fuel injection valve 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for reducing engine vibration in a low speed, low load range of a diesel engine.

Diesel engines are compression ignited, so the compression ratio is 2 to 3 times higher than spark ignition engines such as gasoline engines, and the work in the compression stroke is extremely large, causing torque fluctuations and rotational speed fluctuations. This impact was particularly noticeable during idling, causing an increase in engine vibration.

(Yamamando (Publishing) Automotive Engineering Complete Book No. 5 Diesel Engine) In addition, when the engine is idling, the ambient noise level is low, so the intake noise may cause tinnitus. For this reason, the present applicant has proposed a system that reduces vibration and improves ignition performance by throttling the intake air and heating the intake air at low speeds and low loads. (Utility Model Application No. 56-76158) Furthermore, the present applicant has proposed a device in which the operation of the intake throttle valve 2 and the intake air heating means 10 are improved as shown in FIGS. 1 and 2.

In this vibration reduction device, low-speed, low-speed When the load range is reached, a control circuit (not shown) excites the solenoid 6 that drives the intake throttle valve 2 to fully close the throttle valve 2.

At this time, the intake air is introduced into the intake manifold 8 through the small-diameter auxiliary passage 7 that bypasses the throttle valve 2, and a predetermined small flow rate of intake air is supplied to the engine.

That is, by throttling the intake air, the compression pressure in the combustion chamber is relatively lowered, and the work in the compression stroke is reduced by the reduction in peak pressure. This suppresses rotational speed fluctuations and torque fluctuations, and reduces engine vibration in low-speed, low-load ranges.

Furthermore, since the throttle valve 2 is fully closed, intake noise is attenuated, and noise during idling and the like is reduced. In addition, in the low speed and low load range, the amount of fuel injected from the fuel injection valve 9 is small, and the air-fuel mixture has too much air, so even if the intake air is throttled in this way, the air necessary for combustion is still secured. be done.

By the way, when the air is narrowed down and the compression pressure is lowered in this way, the air temperature also decreases, and the ignition of the injected fuel becomes unstable, which tends to cause a misnore or irregular combustion.

Therefore, in the above device, a sheath heater 1 is provided as a heating means 10 on the downstream side of the throttle valve 2 and the auxiliary passage 7 so as to throttle the intake air and heat the intake air at the same time.

The sheath heater 1 is assembled into a unit, for example, in a throttle chamber 12 in which a throttle valve 2 is interposed, and is energized by a control circuit to heat intake air only when the throttle valve 2 is, in principle, fully closed.

In this case, a combustion chamber glow plug (not shown) may also be used.

As a result, the intake air temperature is relatively increased to compensate for the decrease in compression pressure, that is, the temperature necessary for ignition at the time of maximum compression is ensured, and deterioration of the combustion state is prevented. Therefore, combustion stability is maintained at a high level even though the compression pressure has decreased, and irregular vibrations and torque fluctuations due to irregular combustion are avoided.・、：：、□ １・ 、1m(F)J″″−box・ 7-1't-') '1
The aim is to reduce vibration in the m'b range and improve driving comfort.

By the way, when the engine is started from an extremely low temperature, stable ignition may not be obtained even though the intake air is heated as described above, and problems such as irregular combustion may occur. It is also assumed that engine vibration will increase.

The purpose of the present invention is to ensure reliable and stable ignition performance even under such conditions, and by installing an auxiliary ignition device in the combustion chamber (overflow chamber), engine vibration is suppressed when the intake air is throttled. To provide a vibration reduction device for a diesel engine, which performs spark discharge when the amount of fuel increases and promotes ignition of fuel.

Embodiments of the present invention will be described below with reference to FIGS. 3 and 4.

In FIG. 3, an ignition device 16 is installed in a combustion chamber (overflow chamber) 15 near a fuel injection valve 9. As shown in FIG.

The ignition device 16 discharges a spark during fuel injection to promote ignition of the air-fuel mixture, and is supplied with high-voltage ignition current from an ignition coil 17 via a distributor 18.

The upper distributing valve 18 is a valve for distributing high voltage current in accordance with the fuel injection timing of each cylinder (#1 to #4).
It is connected to the secondary coil of the ignition coil 17. The primary coil of the ignition coil 17 is connected to a battery 20 via an ignition switch 19, and a switching circuit 21 connects and connects the ground side of the primary coil to a battery 20.

The switching circuit (power transistor) 21 is turned on and off based on the ignition signal from the control knee unit 22, and when turned on, a high voltage current is generated in the ignition coil 17.

The control unit 22 receives a signal from a vibration acceleration sensor 24 that detects the vibration of the engine body 23, and also receives an engine rotation angular velocity signal (crank angle signal) and a load state detection signal. When the engine vibration reaches a predetermined level or higher in a low speed, low load operating range with the throttle valve 2 closed, an ignition signal is output to the switching circuit 21, which constitutes a high voltage application device.

This ignition signal is a pulse signal that is synchronized with the engine rotation and causes ignition to occur at the time of combustion injection in each cylinder -6-.

As shown in FIG. 4, the ignition device @16 is configured to also serve as a glow plug.

That is, around the center electrode 26 connected to the side electrodes 24 by the insulator 25, a heating coil 27 is disposed embedded inside the insulator 25.

The high tension cord from the ignition coil 17 described above is connected to the terminal terminal 28 of the center electrode 26, and a predetermined heating current is supplied to the terminals 29A and 29B of the heating coil 27 from a preheating circuit (not shown) prior to starting the engine. be done.

In the above configuration, when the engine is in a low speed and low load range, the intake throttle valve 2 is closed and the heating means 10 is energized to reduce the compression work of the engine.
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In this operating state, when the engine vibration input to the engine roll unit 22 is below a predetermined vibration level, no ignition pulse is supplied to the switching circuit 21, and therefore the ignition coil 1
Since 7 does not generate high voltage, the igniter @16 is kept inactive.

When the engine shifts to a low position after warming up,
Since the cooling water temperature is also sufficiently high, stable combustion can be achieved even if the intake air is restricted.

On the other hand, after starting the engine from an extremely low temperature, during warm-up, or when driving in an extremely cold region, the maximum compression temperature does not rise sufficiently when the intake air is throttled, resulting in unstable ignition and increased engine vibration. Sometimes.

In this state, when the vibration level input to the control unit 22 exceeds a predetermined value, supply of ignition pulses to the switching circuit 21 is started.

As a result, the secondary side of the secondary coil 17 is closed.

A high-voltage ignition current is induced in the coil in synchronization with the ignition pulses l and s, and is transmitted to the ignition device 1 via the distributor 18.
This ignition current is distributed to 6.

-8- Spark discharge is generated between the center electrode 26 and the side electrodes 24 by applying the high voltage current, which assists in igniting the fuel injected from the fuel injection valve 9.

By causing spark discharge in the ignition device 16 in this manner, compression ignition of the injected fuel is performed stably, flame propagation after ignition is also smooth, and irregular combustion can be prevented.

When the combustion is sufficiently stable, the ignition device 16 stops the ignition operation via the control unit 22 to save the energy required for ignition, and the ignition operation is also stopped during normal operation when the intake throttle valve 2 is open. will be stopped.

Note that since the ignition device 16 also functions as a glow plug, when starting the engine at a low temperature, the inside of the overflow chamber 15 can be preheated by energizing the heating coil 27 for a predetermined period of time prior to starting. can.

Note that this heat coil 27 is used as the heating means 1 for heating intake air.
0, the heating action may be performed when the intake throttle valve 2 is closed.

-9- By thus serving as a glow plug, the ignition device 16 can be easily attached to the narrow overflow chamber 15.

As described above, according to the present invention, it is possible to reliably avoid the occurrence of irregular combustion when the intake air is throttled, and it is possible to suppress as much as possible the occurrence of vibration in the low engine speed and low load range under all conditions. At the same time, it is possible to reliably prevent an increase in smoke, HC, etc. in the exhaust gas.

[Brief explanation of the drawing]

Figure 1 is a plan view of a diesel engine that is the premise of the present invention, Figure 2 is a front view, Figure 3 is a block diagram showing the main parts of an embodiment of the present invention, and Figure 4 is a cross-sectional view of the ignition system. be. DESCRIPTION OF SYMBOLS 1... Intake passage, 2... Intake throttle valve, 3... Fuel injection pump, 10... Heating means, 15... Overflow chamber,
16... Ignition device, 17... Ignition coil, 18... Distributor, 21... Switching circuit, 22... Control unit, 24...
・Vibration acceleration sensor. -10-

Claims (1)

[Claims] Same as a throttle valve that throttles the intake passage when the engine is running at low speed and under low load (a heating means for heating the intake air, a means for detecting engine vibration, an ignition device for injected fuel provided in the combustion chamber,
A vibration reduction device for a diesel engine, comprising: a high voltage application device that supplies a high voltage ignition pulse to an ignition device when engine vibration exceeds a predetermined level at the time of low speed and low load.