JPH0359265B2 - - Google Patents

Description

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

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 phenomenon is particularly noticeable during idling, causing increased engine vibration. (Sankaido (Publishing) Automotive Engineering Complete Book No. 5 Diesel Engine) Also, when the vehicle is idling, the ambient noise level is low, and the intake noise may cause tinnitus. For this reason, the applicant has proposed that by restricting the intake air and heating the intake air at low speeds and low loads,
There have been proposals that aim to reduce vibration and improve ignitability. (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.

This vibration reduction device uses, for example, signals from a load detection switch 5 that responds to the opening degree of the control lever 4 of the fuel injection pump 3, and a rotation sensor that detects the engine rotation speed from the pump rotation shaft, etc.
In the low speed and low load range, the control circuit (not shown)
energizes 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, 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 this intake air is throttled, sufficient air is secured for combustion. .

By the way, when the intake air is throttled and the compression pressure is lowered in this way, the air temperature also decreases, making the ignition of the injected fuel unstable, which tends to cause misfires and irregular combustion.

Therefore, in the above device, a sheath heater 11 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 11 is assembled into a unit, for example, in a throttle chamber 12 in which the throttle valve 2 is interposed, and is energized by a control circuit in principle only when the throttle valve 2 is fully closed to heat the intake air. In this case, a combustion chamber glow plug (not shown) may also be used.

This relatively increases the intake air temperature to compensate for the drop in compression pressure, that is, to ensure the temperature necessary for ignition at the time of maximum compression, thereby preventing deterioration of the combustion state. 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.

In this way, vibration and noise are reduced at low speeds and low loads, such as during idling, and driving comfort is improved.

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 engine vibration may occur due to irregular combustion. It is also expected that this will increase.

The present invention aims to ensure reliable and stable ignition performance even under such conditions. To this end, the present invention includes a means for detecting the engine operating state, a means for determining when the engine is running at low speed and with low load based on a signal from the detecting means, and a means for determining when the engine is running at low speed and under low load based on the signal from the determining means. A heating means for heating the intake air in the same way as a throttle valve that throttles the intake passage, a means for detecting engine vibration, a spark plug provided in the engine combustion chamber, and a control system for the engine at low speeds and low loads based on signals from each of the above detection means. A high-voltage application device that supplies a high-voltage ignition pulse to the ignition plug when the engine vibration exceeds the predetermined level based on a signal from the determination means. Ta.

Based on this configuration, when combustion conditions are poor, such as when engine vibration exceeds a predetermined level and the throttle valve is closed at low speed and low load, the ignition of the injected fuel is promoted via the ignition plug, ensuring reliable operation. This results in stable combustion performance and reduced vibration and noise.

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 sparks during combustion injection to promote ignition of the air-fuel mixture, and the ignition coil 1
The high voltage ignition current from 7 is transmitted to the distributor 18.
Supplied via.

The distributor 18 connects each cylinder (#1 to #
It distributes high-voltage current in accordance with the fuel injection timing in step 4), and 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.

Switching circuit (power transistor) 21
is turned on and off based on the ignition signal from the control unit 22, and a high voltage current is generated in the ignition coil 17 when it is turned on. These constitute the high voltage application device.

The control unit 22 constitutes each of the above-mentioned determination means, and receives a signal from a vibration acceleration sensor 24 that detects vibrations of the engine body 23, and also receives an engine rotational angular velocity signal (crank angle signal) and a load state detection signal. Based on this input, an ignition signal is output to the switching circuit 21 when engine vibration exceeds a predetermined level in a low speed, low load operating range with the intake throttle valve 2 closed.

This ignition signal is a pulse signal that is synchronized with engine rotation and causes ignition to occur during combustion injection in each cylinder.

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

That is, around the center electrode 26 connected to the side electrodes 24 by the insulators 25, there are insulators 25.
The heating coil 27 is embedded inside the
will be placed.

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

In the above configuration, when the engine is in a low speed and low load range state, the intake throttle valve 2 is closed and the heating means 10 is energized to reduce the compression work of the engine and suppress engine vibrations, as described above. .

In this operating state, when the engine vibration input to the control unit 22 is below a predetermined vibration level, no ignition pulse is supplied to the switching circuit 21, and therefore the ignition coil 17 generates a high voltage. Therefore, the ignition device 16 is kept in an inoperative state.

When the engine transitions to a low-load state after warming up, the cooling water temperature and other conditions are sufficiently high, so stable combustion can be achieved even if the intake air is throttled.

On the other hand, after starting the engine from an extremely cold state, 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.
Ignition may become unstable and engine vibration may increase.

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

As a result, a high-voltage ignition current is induced in the secondary coil of the ignition coil 17 in synchronization with the ignition pulse, and this ignition current is distributed to the ignition device 16 via the distributor 18.

By applying the high voltage current, spark discharge occurs between the center electrode 26 and the side electrodes 24, 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 heated in advance by energizing the heating coil 27 for a predetermined period of time prior to starting. can.

Note that this heating coil 27 may be synchronized with the heating means 10 for heating intake air to perform a heating action when the intake throttle valve 2 is closed.

By using it as a glow plug in this way,
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 occurrence of irregular combustion during intake throttling, and even under all conditions when the engine is running at low speed or
This makes it possible to suppress the occurrence of vibration in the low load range as much as possible, and also reliably prevents an increase in smoke and HC in the exhaust.

Furthermore, the present invention detects the vibration level of the engine and drives the spark plug only under conditions where deterioration of combustion cannot be avoided by only intake throttling and intake air heating, thereby preventing unnecessary energy loss. You also have the advantage of being able to do so.

[Brief explanation of drawings]

Fig. 1 is a plan view of a diesel engine which is the premise of the present invention, Fig. 2 is a front view, Fig. 3 is a block diagram showing the main parts of an embodiment of the present invention, and Fig. 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.

Claims (1)

[Claims] 1 means for detecting the engine operating state; means for determining whether the engine is operating at low speed and low load based on a signal from the detection means; and a throttle valve that throttles the intake passage when the engine is at low speed and low load based on the signal from the determination means. heating means for heating the intake air in the same way,
means for detecting engine vibration; a spark plug provided in the engine combustion chamber; means for determining whether engine vibration exceeds a predetermined level at low speed and low load based on signals from each of the detection means; and this determination. A vibration reduction device for a diesel engine, comprising: a high voltage application device that supplies a high voltage ignition pulse to the spark plug when engine vibration exceeds a predetermined level based on a signal from the means.