JPS6329030A - Intake controller for diesel engine - Google Patents

Abstract

PURPOSE:To reduce the vibration noise due to the intake throttling and the NOX discharge quantity by keeping the intake negative pressure on the downstream side of an exhaust recirculation port constant by a throttle valve and keeping the exhaust recirculation quantity constant by controlling an exhaust recirculation valve by the above-described negative pressure. CONSTITUTION:An intake throttle part 10 divided into the first and second passages 8 and 9 is formed on the upstream side from the connection part between a suction passage 2 and an EGR passage which returns a part of the exhaust gas in an exhaust passage 3 and in which an EGR valve 4 is installed, and a throttle valve 12 which is opened by the stepping-in of an accelerator pedal 11 is installed into the first passage 8, and an intake throttle valve 13 which is opened and closed according to the supplied pressure into a negative pressure passage 15 is installed into the second passage 9. The negative pressure passage 15 is branched midway to apply the supplied pressure also into the EGR valve 4, and the first negative pressure selector valve 16 is installed onto the upstream side from the branched part, and the first input port is connected to the downstream side of the first passage 9, and the second input port is can be connected with a vacuum pump 18 through the second negative pressure selector valve 17.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an air intake control device for a diesel engine, and particularly relates to an air intake control device for a diesel engine.
This invention relates to an intake throttle valve that achieves both noise reduction and exhaust gas recirculation (EGR) control.

[Prior art 1] In general, in diesel engines, throttling the intake air during idling is a bad idea! It is effective in reducing noise, but if the engine is equipped with an E For example, as seen in Japanese Patent Laid-Open No. 61-16238, in addition to the first intake throttle valve that opens when the accelerator pedal is depressed, there is also a sub-intake throttle valve for reducing vibration and noise, and a differential pressure between intake and exhaust. Normally, the system becomes extremely complex both mechanically and in control, as it includes two intake throttle valves, including a second intake throttle valve for increasing EGRI by increasing EGRI. Moreover, it is thought that the characteristics of the second intake throttle valve located upstream of the exhaust gas inlet in the intake passage will always have an influence on the characteristics of the sub-intake throttle valve located downstream, and each is very subtle. This will require significant adjustments.

[Problems to be solved by the invention] As explained in the same publication, the reason why the above-mentioned complicated system and delicate adjustment are required is due to the intake throttling characteristics for noise reduction and EGR control. The intake throttle characteristics are different from each other, and one intake throttle valve has both noise reduction and ER
The problem is that it is difficult to achieve both G control and G control.

However, in particular, it is necessary to provide a second intake throttle valve and throttle the intake air to maintain a large differential pressure between the intake and exhaust air.
Theoretically, it is only in the low rotation range where the differential pressure between intake and exhaust is small,
Practically speaking, it is sufficient only when idling.

If this is the case, the problem should disappear if a single intake throttle valve can achieve intake throttle characteristics that can achieve both noise reduction and EGR control only during idling.

Therefore, an object of the present invention is to use a single intake throttle valve and an EGR valve in common, based on the premise that EGRJi is determined by the intake negative pressure at the exhaust gas inlet and the valve opening degree of the EGR valve provided in the EGR passage. It is an object of the present invention to provide an intake control device for a diesel engine that can solve the above-mentioned problems and perform the two functions of vibration noise reduction and EGR during idling with one intake throttle valve.

In addition, as a prior art, the throttle valve installed in the intake passage and the EGR
There is a system that can perform EGR control that satisfactorily matches the NOx reduction function and operational performance by commonly controlling the EGR control valve installed in the R passage according to the operating state (Japanese Patent Laid-Open No. 56 .-159554).

[Means for Solving the Problems] The intake control device for a diesel engine of the present invention includes a throttle valve that opens when an accelerator pedal is depressed and a passageway located upstream of the EGR port of the intake passage into which recirculating exhaust gas is injected. There is an intake throttle valve which is installed in parallel with the intake throttle valve and is opened by negative pressure when supply pressure is applied, and an E which is installed in the EGR path and which opens in the same way by negative pressure when the same supply pressure is applied as the intake throttle valve.
It is equipped with a GR valve. The common supply pressure applied to these intake throttle valves and EGR valves is controlled by a switching valve.
Depending on the load condition, the pressure can be sequentially switched to intake negative pressure, vacuum negative pressure, and atmospheric pressure on the downstream side of the intake throttle valve.

[Function] When the switching valve operates, the intake throttle valve and E
Intake negative pressure downstream of the intake throttle valve is supplied to the GR valve.

During idling, the accelerator pedal is not depressed at all, so the throttle valve is fully open, so when negative intake pressure is supplied to the intake throttle valve, the intake passage upstream of the EGR port becomes throttled, and this throttled state is held constant because the intake throttle valve is under feedback control. Therefore, on the downstream side of the intake throttle valve where the EGR port is located, a constant amount of intake throttle can be stably obtained without becoming excessively throttled.

On the other hand, with the intake negative pressure kept constant by the intake throttle valve, E
Since the GR valve is controlled, its opening amount is also constant,
EGRfi, which is determined by the constant valve opening amount and the constant intake negative pressure downstream of the intake throttle valve, is injected into the intake passage from the EGR port.

Therefore, the intake throttle amount or intake negative pressure of the intake throttle valve held during idling, and the valve opening amount of the EGR valve,
By setting so that vibration noise and NOx are both reduced during idling, optimal control for both can be performed.

When the load is light, vacuum negative pressure is supplied to the intake throttle valve and the EGR valve, and these valves are both fully open, so that the optimum EGR amount can be obtained due to the differential pressure between intake and exhaust.

At high loads, the intake throttle valve and EGR valve are closed in communication with the atmosphere, and therefore no EGR is applied.

[Example] An example of the present invention will be described below based on the accompanying drawings.

The figure shows an example of an intake air control device for a diesel engine according to the present invention.

1 is a diesel engine, and its intake passage 2 and exhaust passage 3 have valve openings adjusted according to the supply pressure midway through the EGRJ engine.
They are connected through an EGR path 5 with an EGR valve 4 interposed therebetween. The intake passage 2 on the upstream side of the EGR port 6, which is the inlet of the EGR passage 5, has a partition wall 7 and a first. An intake throttle section 10 is formed which is divided into second passages 8 and 9. The first passage 8 has a throttle valve 12 that opens when the accelerator pedal 11 is depressed, and the second passage 9 has a throttle valve 12 that opens when the accelerator pedal 11 is depressed. One intake throttle valve 13 whose opening degree is adjusted to control the intake throttle valve is provided. This intake throttle valve 13 and the above-mentioned EGR valve 4 are both configured to open due to negative pressure, and negative pressure passages 15 and 15 that respectively lead supply pressure to these valves merge in the middle. 4.1
Common pressure can be applied to 3.

The merged negative pressure passages 15 of both valves are connected to an output port of a first vacuum switching valve (hereinafter referred to as "first vS") 16. One input port of the first VSVl6 is connected to the downstream side of the intake throttle section 10, more specifically, the downstream side of the intake throttle valve 13, and the other input port is connected to the second vacuum switching valve (hereinafter, the second vacuum switching valve). VS
(2) connected to 17 output ports. One input port of this second VSV17 is also connected to a vacuum pump 18 that generates vacuum negative pressure, and the other input port is open to the atmosphere.

By the way, the first VSVl6 mentioned above is the 0N-
Current control is performed by turning OFF, and only when the control lever 22 of the fuel injection pump 20 that is linked to the accelerator pedal 11 is in the idle state, the first microswitch 21 is turned ON and the first VSV is activated.
Supply current to l6. In the idle state where current is supplied, one input port of the first VSVl6 that guides the intake negative pressure on the downstream side of the intake throttle valve 13 communicates with an output boat connected to the intake throttle valve 13 and the EGR valve 4; On the other hand, when the first microswitch 21 is turned OFF and the current supply is cut off in a state other than the idle state, it communicates with the output port of the second VSV17.

Further, the current of the second VSVl7 is controlled by turning ON/OFF a second microswitch 23 attached to the fuel injection pump 20, and when the diesel engine 1 is in a light load state, the control lever is Only when the rotation angle (opening degree) of 22 is relatively small, the second microswitch 23 is turned on and supplies current to the second VSV17. During light load conditions where current is supplied, the second
■S■17 connects one input boat that leads the vacuum negative pressure of the vacuum pump 18 to the output boat of the first VSVl6. Conversely, when the load on the diesel engine 1 is high and the opening degree of the control lever 22 is large, Sometimes, the second microswitch 23 is turned off and the second VSVl
The current supply to 7 is cut off, and the second VSVl 7 is connected to the other input port, which is open to the atmosphere, to the first VSVl6.
It is designed to communicate with the output boat.

Note that 25 is a battery that is a current supply source for the first and second VSV16.17.

Next, the operation of the above configuration will be explained by dividing it into three states: idle state, light load state, and high load state.

In the idle state, the accelerator pedal 11 is not depressed at all, so the first and second microswitches 21.23
are both ON, so the first and second VS
When V16.17 is energized, they both turn on, but when the first VSV16 turns on, communication with the second VSV17 is cut off, so the state of the second VSV17 is irrelevant.

1st (7) VSVl 6 (7) ON, the negative pressure passage 15 of the EGR valve 4 and the intake throttle valve 13 has an intake throttle part 1
The intake negative pressure taken out from the downstream of 0 is led.

Therefore, the intake throttle valve 13 provided in the second passage 9
opens in response to the intake negative pressure, but since the throttle valve 12 is closed at this time, the negative pressure in the intake passage 2 increases, resulting in an intake throttled state. However, since the intake negative pressure on the downstream side is fed back to the intake throttle valve 13, an excessive throttle fog does not occur, and a constant amount of intake throttle can be stably obtained. As a result, vibration noise can be reduced in accordance with the intake throttle amount.

On the other hand, the EGR valve 4 is also opened in response to the intake negative pressure stably maintained by the feedback control of the intake throttle valve 13. Therefore, both the intake negative pressure held constant and this E
Optimal EGRff determined by the opening amount of GR valve 4
i is injected into the intake path 2 from the EGR port 6, and this injection amount is also stably maintained by the feedback function. As a result, NOx can be reduced by EGR.

In this way, the EGR valve is also commonly controlled by the intake negative pressure obtained from the intake throttle valve 13 that is feedback-controlled, so even if EGR is performed in addition to the intake throttle, the optimum vibration and noise reduction can be achieved in advance. If the characteristics of the intake throttle valve 13 and EGR valve 4 are set so as to obtain a reduction in NO.
The optimal intake throttle amount and EGR valve opening amount can be obtained with just one intake throttle valve, and therefore the system using two intake throttle valves is extremely complex both mechanically and in terms of control. There is no need for very delicate adjustments.

In a light load state, the accelerator pedal 11 is depressed, so the first microswitch 21 is turned OFF and the second microswitch 21 is turned OFF.
The microswitch 23 remains ON. Therefore, in the negative pressure passage 15 of the EGR valve 4 and the intake throttle valve 13,
The large negative pressure generated in the vacuum pump 18 is guided through the first VSV 16 that is OFF and the second VSV 17 that is ON, so that the EGR valve 4 and the intake throttle valve 13 are both fully open. . As a result, the optimum EGRffi is injected into the intake passage 2 according to the differential pressure between the intake and exhaust air, which is determined by the valve opening degree caused by depression of the accelerator pedal 11 and the operating state.

Under high load conditions, the first. Since both the second microswitches 21 and 23 are turned off, the intake throttle valve 13 and the E
The GR valve 4 is closed and communicated with the atmosphere. As a result, EGR is prevented from being applied under high load conditions.

Note that even if the intake throttle valve 13 closes at this time, the throttle valve 1 will close due to large depression of the accelerator pedal 11.
2 has a sufficient amount of valve, so there is no problem with intake.

As described above, according to this embodiment, during idling, the intake throttle valve maintains the negative pressure downstream from this constant, and by guiding this negative pressure to the EGR valve, the EGR is maintained at the most constant level, and the idle link When this is not the case, a microswitch detects this and connects the EGR valve with the vacuum pump or the atmosphere, so that an appropriate EGRI or EGR stop can be obtained. , MOX reduction during idling and reduction of vibration noise can be achieved with one intake throttle valve without causing any hindrance to the reduction.

[Effects of the Invention] To summarize, according to the present invention, during idling, the intake throttle valve maintains a constant intake negative pressure on the downstream side of the exhaust recirculation port, and the exhaust recirculation valve is controlled by this intake negative pressure to reduce the exhaust gas. Since the recirculation amount is also kept constant, a simple configuration with just one intake throttle valve reduces the noise during idling due to the intake throttle and reduces NOx due to exhaust gas recirculation.
It is possible to achieve both the reduction of NOx and, moreover, to appropriately reduce NOx without any trouble by operating the switching valve at times other than when the engine is idling.

[Brief explanation of the drawing]

The figure is a configuration diagram of a diesel engine according to an embodiment of the present invention. In the figure, 1 is a diesel engine, 2 is an intake path, 4 is an exhaust recirculation valve, 6 is an exhaust recirculation port, 12 is a throttle valve, 13 is an intake throttle valve, and 16.17 is a first switching valve. 21.23 is a second vacuum switching valve; 18 is a vacuum pump that generates vacuum negative pressure; and 21.23 is a first vacuum switching valve that detects the load state. This is the second microswitch.

Claims (1)

[Claims] An intake throttle valve is installed upstream of the exhaust gas recirculation port in the intake passage and is opened by negative pressure, and an exhaust gas recirculation valve is applied with the same supply pressure and opened by negative pressure, depending on the load condition. An intake control device for a diesel engine, which is equipped with a switching valve that sequentially switches the supply pressure of the intake throttle valve to intake negative pressure, vacuum negative pressure, and atmospheric pressure downstream of the intake throttle valve.