JPS6314170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a diesel engine.

Generally, unlike gasoline engines, diesel engines do not have a throttle valve in the intake passage, so the amount of intake air becomes excessive during light loads, especially when idling, which increases engine compression resistance and reduces torque fluctuations. This is likely to occur. Therefore, there is a problem in that the engine vibrates due to the torque fluctuation, and vibration noise is generated.

As a means to solve this problem, an intake shutter (equivalent to a throttle valve in a gasoline engine) is installed in the intake passage so that it can be opened and closed, and the intake shutter is closed only during light loads to throttle the intake passage (intake shutter). An intake shutter device is known in which the amount of vibration and vibration noise of the engine are reduced by reducing the amount of intake air (by reducing the opening degree of the engine) (see, for example, Japanese Patent Laid-Open No. 8217/1983).

Therefore, in order to confirm the above fact, the inventor first conducted an experiment to investigate the relationship between the amount of throttle of the intake shutter device and the amount of vibration of the engine when the engine has been warmed up (warm state). . Here, the throttle amount of the intake shutter device is expressed as the intake negative pressure downstream of the intake shutter when the engine is idling, that is, when the engine is rotating at 600 rpm. ). In addition, if the engine vibrates due to torque fluctuations, the transmission case will also vibrate, and since the amount of vibration of the engine can be considered equal to the amount of vibration of the transmission case, in this experiment, the amount of throttle of the intake shutter device will be The relationship between this and the amount of vibration of the transmission case was investigated (under conditions of idling with the engine warmed up).
The result is shown in Figure 2. It goes without saying that the vibration noise also shows almost the same tendency as the amount of vibration of the transmission case.

Next, considering the above experimental results, we found that from when the intake shutter device is fully open (restriction amount: 3 mmHg), if the amount of restriction is increased, the amount of vibration of the transmission case will gradually decrease. I understand.

Therefore, it is confirmed that the larger the throttle amount of the intake shutter device, the smaller the amount of vibration and vibration noise of the engine.

Considering the amount of restriction of the intake shutter device, when the amount of restriction is set to 100 mmHg compared to the fully open state, the amount of vibration of the transmission case (the amount of vibration of the engine) decreases by approximately 3 dB, that is, the vibration energy is reduced by approximately 1/2. It turns out that it will be about 2. Also,
Experiments have shown that this degree of vibration energy reduction,
In other words, it has been confirmed that it is necessary to suppress the amount of vibration of the transmission case to about 98 dB or less.

On the other hand, if the throttle amount is 400 mmHg or more, the amount of intake air will decrease significantly and the combustion condition will deteriorate, causing problems such as half-misfire and the emission of white smoke and odor (formaldehyde).

According to the above considerations, the throttle amount of the intake shutter device is 100mm when idling after warm-up.
It is preferably Hg or more and 400 mmHg or less, preferably in the range of 150 mmHg to 350 mmHg.

However, when starting the engine (from when the starter motor rotates until cranking is completed and the engine speed rises to idling speed of 600 rpm), the intake air If the throttle amount of the shutter device is set to 100 mmHg or more, there is a problem in that the amount of intake air decreases, resulting in a state of insufficient intake air, which deteriorates the startability of the engine.

Therefore, during the period when the combustion conditions are poor when starting the engine, that is, the time when the starter motor is rotating, and after the energization to the starter motor ends and cranking is completed, the engine wall temperature rises for a certain period (10 It is desirable to supply sufficient intake air without throttling the intake passage for a period of about 2 seconds).

SUMMARY OF THE INVENTION An object of the present invention is to provide an intake system for a diesel engine that improves engine startability when starting the engine without impairing combustibility during cold engine operation. The feature is that the throttle amount is reduced during idling after warming up.
In addition to setting the throttle amount to produce an intake negative pressure of 100 mmHg or more and 400 mmHg or less, reduce the throttle amount of the intake shutter device when the engine is running cold compared to the throttle amount after warm-up is completed, and also reduce the throttle amount for a certain period of time from the completion of cranking when starting the engine. What has happened is that a device has been installed to reduce the amount of throttle of the intake shutter device, which releases the operation of the intake shutter.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, 1 is an engine, and 2 and 3 are an intake passage and an exhaust passage, respectively, which communicate with a combustion chamber of the engine. An intake shutter 4 constituted by a butterfly valve is attached to the intake passage 3, and an exhaust brake valve 5 is attached to the exhaust passage 3 so as to be openable and closable.

The intake shutter 4 and the exhaust brake valve 5 are connected to first and second power chambers 8 and 9 via link mechanisms 6 and 7, respectively.

Negative pressure chambers 8a and 9a of each power chamber 8 and 9
are the first and second three-way solenoid valves 1, respectively.
It is connected to a vacuum tank 13 through a negative pressure passage 12 in which pipes 0 and 11 are interposed. A vacuum pump 15 driven by the engine 1 is connected to the vacuum tank 13 via a check valve 14 . Both three-way solenoid valves 10, 1
1 closes the negative pressure passage 12 and closes the negative pressure chamber 8 of the power chambers 8 and 9 when not in operation and is not excited.
a, 9a are opened to the atmosphere through the atmospheric holes 10a, 11a, and during the excited operation, the atmospheric holes 10a, 1
1a is closed, the negative pressure passage 12 is opened, and the negative pressure chambers 8a and 9a are communicated with the vacuum tank 13.

Thus, the intake shutter 4 and the exhaust brake valve 5 are connected to the negative pressure chambers 8a and 8a of each power chamber 8 and 9, respectively.
When 9a is in the atmospheric pressure state, it is held in the open position by the elastic force of the springs 8c and 9c in the negative pressure chambers 8a and 9a, while when the negative pressure chambers 8a and 9a are in the negative pressure state, the springs The diaphragms 8b and 9b are deflected against the elastic force of the diaphragms 8c and 9c, and are in the closed position.

Reference numeral 16 denotes a first bypass passage connecting the upstream side and the downstream side of the intake shutter 4, which is equipped with a solenoid valve 17 that opens only when the exhaust brake is activated and a muffler 18 (enlarged chamber) that further dampens intake noise when the exhaust brake is applied. has been done. The minimum area of the first bypass passage 16 is that when the solenoid valve 17 is opened, the intake shutter 4 is closed and the intake negative pressure downstream thereof is 15 to
It is set to be 70mmHg.

A second bypass passage 20 connects the upstream side and the downstream side of the intake shutter 4, and an on-off valve 19 is interposed in the middle thereof. This on-off valve 19 opens when the engine 1 is cold and the combustion state is unstable (for example, when the temperature of the engine cooling water is 80° C. or lower), communicates with the second bypass passage 20, and connects the intake shutter 4.
When the valve is closed, the amount of throttling by the intake shutter device during idling is reduced.

21 is a battery with one end grounded, and a key switch 22 that closes when operating the engine 1 and a key switch 22 that opens when the engine 1 is started, more precisely, between cranking and a few seconds after cranking. A starting relay switch 23 that opens when an accelerator pedal (not shown) is depressed and closes when the accelerator pedal (not shown) is released are connected in series. Furthermore, the accelerator switch 2
In contrast to 4, there is an exhaust brake switch 25 that opens and closes manually at the driver's selection, a clutch switch 26 that opens when a clutch pedal (not shown) is depressed and closes when it is released, and a clutch switch 26 that opens when the change lever is in the neutral position and changes the gear position. A neutral switch 27, which is closed by the switch 27, is connected in series.

One terminal of the first three-way solenoid valve 10 is connected between the accelerator switch 24 and the exhaust brake switch 25, and the other terminal is grounded. Further, one terminal of the second three-way solenoid valve 11 is connected to the neutral switch 27, and the other terminal is grounded.

A starter switch 28 is connected to the base of a transistor 30 via a resistor 29.
The collector of the transistor 30 is connected to an exciting coil 23a (starting relay switch 23) in parallel with the starter switch 28, and the emitter is grounded. A capacitor 31 and a resistor 32 are connected in series between the starter switch 28 and the resistor 29, and the resistor 32 is grounded. During cranking, when the starter switch 28 is closed and the starter motor is rotating, and after completion of cranking when the starter switch 28 is open, the starter switch relay 23 is opened for a certain period of time, and the intake shutter 4 is closed at the time of starting. This is to ensure that it does not interfere with

Note that 33 is an air cleaner.

With the above configuration, when the starter switch 28 is closed after the key switch 22 is closed in order to start the engine 1, the starter motor (not shown) rotates and current flows from the battery 21 to the base of the transistor 30. current, making the transistor 30 conductive. Due to this conduction, a current flows through the excitation coil 23a of the starting relay switch 23, and the starting relay switch 23 is excited and opened.
Therefore, at this time, even if the accelerator pedal is released and the accelerator switch 24 is closed, the first three-way solenoid valve 10 is not energized, the negative pressure from the vacuum tank 13 is cut off, and the power chamber The negative pressure chamber 8a of No. 8 is opened to the atmosphere through the atmospheric hole 10a, and the first power chamber 8
Since the diaphragm 8b does not deviate, the intake shutter 4 is kept fully open. On the other hand, when starter switch 28 is closed, capacitor 31 is charged.

Subsequently, after the starter motor rotates, when the starter switch 28 is opened, the power supply from the battery 21 is cut off, but the capacitor 3 that was being charged is
1 flows into the base of transistor 30, transistor 30 remains conductive and starting relay switch 23 remains open, thus deactivating intake shutter 4 and remaining fully open. . During this time, it takes about 10 seconds, that is, until the wall temperature of the combustion chamber rises due to the heat of combustion, combustion becomes stable, and half-misfire does not occur even when the intake shutter 4 is closed. 31 capacity).
Next, when the discharge from capacitor 31 is completed, transistor 30 becomes non-conductive, current no longer flows through excitation coil 23a of starting relay switch 23, and starting relay switch 23 is closed. Then, since the key switch 22 is closed, if the accelerator pedal is not depressed, the accelerator switch 24 is closed, the first three-way solenoid valve 10 is energized, and the negative pressure chamber 8a of the first power chamber 8 is connected to the vacuum tank. 13, and negative pressure is introduced into the negative pressure chamber 8a. As a result, the diaphragm 9b is deflected, and this deflection closes the intake shutter 4, thereby narrowing the intake passage 3. This throttle amount is 100 mmHg or more and 400 mmHg or less when the first and second bypass passages 16 and 20 are closed, in other words, when the engine 1 is idling after warming up.

Therefore, the starting relay switch 23 operates during cranking, when the starter switch 28 is closed and the starter motor is rotating, and after cranking is complete, when the starter motor is no longer energized, until the wall temperature of the combustion chamber rises. The intake shutter 4 is gradually opened for a certain period of time, the intake shutter 4 is deactivated, and is kept fully open to supply sufficient intake air to the combustion chamber, resulting in good engine startability. Combustion occurs stably.

The reason why the operation of the intake shutter 4 is canceled until a certain period of time has passed after cranking is completed is because even after cranking is completed, heat generated by compression is taken away when the wall temperature is low. This is because combustion becomes unstable.

In addition, during cold engine operation, if the intake passage 2 is not throttled by the intake shutter device, even if the combustion condition is stable, the intake passage 2 will be closed by the intake passage 2 during idling, as in the case of warm-up operation. If the engine is throttled down, even if the wall temperature is higher than when starting, the temperature increase due to compression will not be sufficient, resulting in a half-misfire and emitting harmful unburned gas.
By opening the on-off valve 19 and communicating the second bypass passage 20, the amount of throttle of the intake shutter device during idling is reduced compared to the amount of throttle after warm-up is completed, thereby stabilizing the combustion state. In addition, since there is combustion heat, the amount of throttle of the intake shutter device can be made larger than at the time of starting.

Furthermore, during exhaust braking, by similarly opening the solenoid valve 17 and communicating with the first bypass passage 16, the amount of throttling of the intake shutter device is reduced, and the intake negative pressure during idling operation is converted to 15
I try to keep it at ~70mmHg. This is because if the intake passage 2 is throttled too much during exhaust braking to the same extent as when idling, the exhaust passage 3 is constricted, so the intake air is restricted, the exhaust braking performance decreases, and the intake passage 2 is kept constant. This is because unless the throttle is narrowed more than that, pressure waves will blow back into the intake passage and intake noise cannot be reduced.

In the above embodiment, the intake shutter 4 is kept fully open by opening the start relay switch 23 when the engine is started. Since it is sufficient to reduce the throttle amount to less than the amount of throttle of the intake shutter device during idling, instead of providing the starting relay switch 23, the excitation coil 2 of the starting relay switch 23 is used.
When the solenoid valve 17 is configured to open in step 3a and the transistor 30 is turned on, the solenoid valve 17 is energized to open the first bypass passage 16 during cranking and until a certain period of time has elapsed since the completion of cranking. It can also be configured as

Further, the transistor 30 is made conductive at the time of starting by the starter switch 28 which is directly electrically connected to the base of the transistor 30, but the engine speed during cranking is
It is small at 200r.pm to 300r.pm, but when it stabilizes (when idling) the engine speed is 600r.pm
You can take advantage of this fact.
Specifically, for example, when the engine speed increases, the regulator voltage that increases accordingly is utilized.

Furthermore, the clutch switch 2 in the above embodiment
6 and the neutral switch 27, either of which opens during idling and disables the operation of the exhaust brake.
6, 27 may be replaced by a rotational speed switch that opens when the engine is idling and closes when the engine speed is slightly higher than idling.

The accelerator switch 24, clutch switch 26, and neutral switch 27 do not necessarily have to be of a type that directly responds to the movement of the accelerator pedal, clutch pedal, and change lever, but may be of a type that indirectly informs the movement. good. For example, the accelerator switch 24 may be an idling switch that detects the idling position of a control lever of a fuel injection pump.

Note that the exhaust brake switch 25 of the above embodiment
is not necessarily required and may be omitted.

In the above embodiment, the intake shutter is closed only when the accelerator pedal is released, and is fully opened at other times; however, the present invention is not limited to this, and the intake shutter is closed even at low rotation speeds and low loads. may be closed (however,
In this case, it is necessary to set the closing amount smaller than when idling).

Moreover, although the above embodiment is an example of an automobile diesel engine, it goes without saying that the present invention can also be applied to diesel engines used in various other industrial machines.

As described above, the present invention reduces the throttle amount of the intake shutter device to 100 mm during idling after completion of warm-up.
In addition to setting the throttle amount to produce an intake negative pressure of Hg or more and 400 mmHg or less, the throttle amount of the intake shutter device is reduced when the engine is running cold compared to the throttle amount after warm-up is completed, and for a certain period of time after cranking is completed when the engine is started. By installing a device that reduces the amount of restriction of the intake shutter device, which would previously deactivate the intake shutter, sufficient intake air is supplied when the engine starts without impairing combustibility during cold engine operation. Engine startability is good.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the intake system of a diesel engine which is an embodiment of the present invention, and Fig. 2 shows the amount of throttle of the intake shutter system and the vibration of the transmission case when warm-up is completed and at idling. It is a graph showing the relationship with quantity. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Exhaust passage, 4... Intake shutter, 5... Exhaust brake valve, 6, 7... Link mechanism, 8... First power chamber, 8a... Negative pressure chamber, 8b...Diaphragm, 8c...Spring, 9...Second power chamber, 9a...Negative pressure chamber, 9b...Diaphragm, 9c...Spring, 10...First three-way solenoid valve, 10a ...Atmospheric hole, 11...Second three-way solenoid valve, 11a...Atmospheric hole, 12...Negative pressure passage, 13...Vacuum tank, 14...Check valve, 15...Vacuum pump, 16... 1st bypass passage, 17... Solenoid valve, 18... Silencer, 19... Open/close valve, 20... Second bypass passage, 21... Battery, 22... Key switch,
23... Start relay switch, 23a... Excitation coil, 24... Accelerator switch, 25... Exhaust brake switch, 26... Clutch switch,
27...neutral switch, 28...starter switch, 29...resistor, 30...transistor, 31...capacitor, 32...resistor, 3
3...Air cleaner.

Claims (1)

[Scope of Claims] 1. In an intake system for a diesel engine, which is provided with an intake shutter in the intake passage and is equipped with an intake shutter device that closes the intake shutter and throttles the amount of intake air when the engine is under light load, The throttle amount is set to a throttle amount that produces an intake negative pressure of 100 mmHg or more and 400 mmHg or less, and the throttle amount of the intake shutter device is reduced when the engine is running cold compared to the throttle amount after warm-up is completed, and cranking is completed when the engine starts. An intake system for an automotive diesel engine, characterized in that it is provided with a device that reduces the amount of throttle of an intake shutter device that releases the operation of the intake shutter until a certain period of time has elapsed. 2. The intake system for a diesel engine according to claim 1, wherein the device for reducing the throttle amount of the intake shutter device prevents the closing operation of the intake shutter device. 3. The device for reducing the throttle amount of the intake shutter device is a bypass passage that connects the intake passages on the upstream side and the downstream side of the intake shutter, and is provided with an opening/closing means that opens when the engine starts. The intake system for a diesel engine according to item 1.