JPS581264B2 - Exhaust recirculation control device - Google Patents

Description

[Detailed Description of the Invention] This invention recirculates a part of the exhaust gas of an internal combustion engine into the intake air,
The present invention relates to an exhaust gas recirculation control device that reduces the generation of NOx.

Exhaust recirculation control devices are known as a means to reduce NO It is preferable to perform exhaust gas recirculation control with good responsiveness.

As a conventional exhaust gas recirculation control device, negative pressure from a negative pressure source is
Dilution control is performed using the atmosphere through a negative pressure regulator that responds to a pressure signal depending on the engine operating state, and this control negative pressure operates the control valve in the exhaust recirculation passage. Although pressure or VC negative pressure is used,
A fixed throttle such as a fixed orifice is usually interposed in this negative pressure extraction passage.

The main purpose of putting a restriction in the negative pressure take-off passage from this negative pressure source is to prevent a large amount of air from flowing back through this negative pressure take-off passage and being introduced into the intake pipe, without seriously affecting the air-fuel ratio of the air-fuel mixture. In addition, when a sudden negative pressure signal is applied to the control valve control negative pressure chamber (including when sudden changes in suction negative pressure and VC negative pressure), drivability deteriorates due to an instantaneous sudden increase in the exhaust recirculation rate. This is to prevent

However, when the engine suddenly accelerates, the amount of exhaust gas recirculation must also rapidly increase accordingly, or NOx generation cannot be sufficiently suppressed. It is preferable to set it as large as possible so as to satisfy the responsiveness of .

However, if the load source is throttled too much, the exhaust recirculation control valve will move violently, opening too much, returning too much, etc., even when the vehicle speed is slowly accelerating from around 40 km/h, for example, and will not converge. Since it was difficult to obtain a stable valve opening, taking these factors into consideration, conventional throttles had to be slightly narrower than required to maintain engine stability.

In order to solve such conventional problems, the present invention is provided with a valve device that makes the flow resistance of the negative pressure introduction passage variable depending on the operating conditions, that is, under operating conditions where rapid acceleration is frequently performed. improves responsiveness and enables effective NOx reduction. Under driving conditions where most of the time is steady driving and stable drivability is required, it prevents sudden activation of the exhaust recirculation control valve and improves drivability. The purpose of the present invention is to provide an exhaust gas recirculation control device that ensures engine stability.

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

In the embodiment shown in FIG. 1, the recirculation passage pressure Pe upstream of the exhaust recirculation control valve is kept constant, and the exhaust pressure (that is, approximately the amount of intake air) is maintained constant.
This is a so-called back pressure proportional type exhaust recirculation control device that increases the differential pressure between the exhaust pressure and the recirculation passage pressure Pe in response to an increase in the amount of exhaust air and increases the amount of exhaust recirculation in accordance with the amount of intake air.

In the figure, 1 indicates an exhaust recirculation passage that connects the exhaust passage and intake passage of the engine and recirculates a part of the exhaust into the intake air, 2 is an orifice provided in this recirculation passage 1 for controlling the flow rate, and 3 is an orifice. 1 shows an exhaust gas recirculation control valve that controls the downstream passage pressure Pe and, as a result, controls the exhaust gas recirculation rate to a constant value.

Reference numeral 4 denotes a negative pressure regulating device, which adjusts the negative pressure (VC negative pressure) generated in the vicinity of the throttle valve 5a provided in the intake passage 5 as the operation control negative pressure of the control valve 3 according to the orifice downstream pressure Pe. Dilution control is performed using the atmosphere, and thereby the control valve 3 is operated under feed bath control so as to keep the pressure Pe constant.

Therefore, the negative pressure adjustment device 4 has two chambers 7a and 7b separated by a diaphragm 6, and the pressure adjustment chamber 7a communicates with the atmosphere and is connected to a valve near the vaporizer throttle valve 5a.
An atmosphere introduction passage 10 is extended from the negative pressure introduction passage 8 of the C negative pressure through an orifice 9, and a diaphragm 6 opens and closes the open end of the atmosphere introduction passage 10 to control dilution of the VC negative pressure with the atmosphere. .

Further, the chamber 7b forms a correction pressure chamber in which the passage pressure Pe between the orifice 2 and the control valve 3 is fed back via the passage 11.

This control negative pressure is then passed through the passage 12 to the control valve 3.
The opening of the control valve 3 is controlled in accordance with this control negative pressure.

Therefore, the diaphragm 6 of the negative pressure regulator 4 responds to the passage pressure Pe, and when this pressure Pe increases, the diaphragm 6 increases the pressure to reduce the dilution rate of the negative pressure source negative pressure by the atmosphere, and the operating leg of the control valve 3 The negative pressure is strengthened, the valve opening is increased, and the pressure Pe is reduced to the original state, while when the pressure Pe decreases, the pressure Pe is increased in the opposite way to the above, and in this way the pressure Pe is always kept constant. At this time, the upstream pressure of orifice 2 is proportional to the exhaust flow rate, so the differential pressure across the orifice is made to be a function of the exhaust flow rate, which is approximately equal to the intake air amount, and as a result, the exhaust gas recirculation amount is proportional to the intake air flow rate. let

Next, a passage 8 that guides the VC negative pressure to the negative pressure working chamber 14 of the control valve 3
is provided with a bypass passage 15 that bypasses the orifice 9 provided in the passage 8, and this bypass passage 15 includes an orifice 16 and an electromagnetic valve that is activated in response to a gear switch, throttle switch, etc. as means for detecting the operating state. A valve 17 is provided to constitute a valve device 18 that variably switches the negative pressure flow path resistance.

Here, if the diameters of the orifices 9 and 16 are S1 and S3, respectively, these are (S1+S3 )>S0>S1.

Alternatively, if the introduction passage 8 and the bypass passage 15 are selectively communicated with each other, the bypass passage 15 is closed when the introduction passage 8 is open, and the introduction passage 8 is closed when the bypass passage 15 is open. The diameter of the oriswiss may be set as S1>S0>S3.

Further, the operating conditions for operating the solenoid valve 17 to open and close the bypass passage 15 are identified as follows, for example.

(1) Conditions in which gears other than tosop gear are used, where the throttle opening changes drastically due to gear changes, etc., and at top gear (
(Detection of gear position), (2) During steady driving with large negative suction pressure (negative pressure source) and during accelerated driving with small negative suction pressure (detection of negative suction pressure), (3) During acceleration with large throttle opening. (4) During small steady running (detection of throttle opening), (4) During large acceleration with negative venturi pressure and during small steady running (detection of venturi negative pressure), etc.

In other words, the flow path resistance of the negative pressure introduction passage 8 is changed by switching the valve device 18 when the operating state fluctuates drastically and when the fluctuation is small, that is, the orifices 9 and 16 are selectively used. The amount of negative pressure introduced from the negative pressure source is switched, and in the former case, responsive exhaust gas recirculation control is performed, and in the latter case, control stability is increased, with the aim of reducing NOx and improving drivability, respectively.

Next, the operation of this invention will be explained.

As mentioned above, in the control device of this embodiment, by keeping the exhaust pressure Pe downstream of the orifice constant, the differential pressure across the orifice is made proportional to the exhaust flow rate, thereby increasing or decreasing the exhaust gas recirculation amount in accordance with the intake air amount. This keeps the exhaust gas recirculation rate constant.

If the passage pressure Pe increases now, the diaphragm 6 of the negative pressure regulator 4 moves upward via the passage 11, thereby reducing the opening degree of the open end of the atmospheric air introduction passage 10 and acting on the negative pressure working chamber 14. As a result of increasing the VC negative pressure, the control valve 3 rises via the diaphragm 13, increasing the valve opening.

Therefore, the increase in pressure Pe is corrected to reduce it back to the original state, and conversely, when the exhaust pressure Pe decreases, the opening end of the atmosphere introduction path 10 is opened wide to dilute the vC negative pressure with the atmosphere. In this way, the pressure Pe is kept constant and the exhaust gas recirculation rate is controlled to be constant at all times.

In this case, if the orifice diameter of the negative pressure source is too large as in the conventional device, for example, when the exhaust pressure Pe increases due to slow acceleration, the control valve opening degree may be increased to keep the exhaust pressure Pe constant. Even if the control is performed, the movement of the control valve 3 becomes rapid due to the large amount of negative pressure introduced from the negative pressure source, and the exhaust pressure Pe decreases too much (feed bath control goes too far). By the time the corrective action of pulling down the diaphragm 6 again catches up with the amount of recirculation, the amount of recirculation becomes excessive and the drivability deteriorates.

However, this rapid operation is required in order to achieve responsiveness and NOx reduction during rapid acceleration, and in the past it has not been possible to satisfy these contradictory requirements.

Therefore, the present invention provides a bypass passage 15 in parallel with the negative pressure introduction passage 8 as described above, and provides an orifice 16 and a solenoid valve 17 in this passage 15 to detect the operating state of a gear switch, a throttle switch, etc. Based on the method, for example, when the top gear is used, when the throttle opening is small, when the venturi negative pressure is small, when the suction negative pressure is large, etc., the solenoid valve 17 is closed and only the passage 8 is used as the negative pressure source passage. , orifice 9 (a small-diameter orifice) alone prevents excessive response in exhaust gas recirculation control and ensures stable operability.

In addition, when a sudden change in operating conditions is likely to occur, such as during acceleration other than the above, the solenoid valve 17 is opened and both the passage 8 and the bypass passage 15, that is, the orifices 9 and 16 are used as the negative pressure source passage. A large amount of negative pressure is introduced, and this negative pressure increases the control negative pressure with good responsiveness in response to sudden changes in operating conditions, and instantly increases the opening degree of the control valve 3 to prevent the generation of NOx.

Of course, even at this time, the negative pressure regulator 4 operates as usual, but since the basic amount of negative pressure introduced has increased, it immediately acts on the control valve 3 when the atmospheric air introduction passage 10 is closed. The control negative pressure is strengthened.

FIG. 2 shows a second embodiment in which the present invention is applied to an exhaust gas recirculation control device that performs exhaust gas recirculation control based on the venturi negative pressure of the carburetor venturi section 20 and also based on feed bath control. It is something.

This embodiment also has a negative pressure source negative pressure (V
There is no change in the fact that the negative pressure (C negative pressure or suction negative pressure) is diluted with the atmosphere and the negative pressure is used to control the operation of the control valve 3, but the difference from the first embodiment is that the Pressure P♂
is decreased in accordance with the venturi negative pressure, and based on this, the pressure is increased in proportion to the increase in the differential pressure across orifice 2 and the intake air volume, and the exhaust gas recirculation volume is increased or decreased approximately in proportion to the intake air volume. .

The upstream pressure of orifice 2 is proportional to the exhaust flow rate.
Because the absolute pressure is relatively small and the pressure fluctuates with the flow rate, even if the downstream pressure of the orifice is constant,
Fluctuation errors in the correlation between the front and rear pressure differential and the exhaust flow rate (intake air amount) inevitably occur.

Therefore, the orifice downstream pressure Pe' is a function of the intake air amount.

Decrease is controlled according to ventilator negative pressure, and this pressure P
By setting e' to a negative pressure with a relatively large absolute value, it is possible to make the differential pressure across the orifice a negative pressure with a large variation range as a function of the intake air amount, thus reducing the influence of upstream pressure fluctuations. is kept small, and as a result,
The reliability of controlling the amount of exhaust gas recirculation is improved compared to the control device of the first embodiment.

However, since this device itself has already been proposed many times by the present applicant, and since it is not the gist of the present invention, a detailed explanation thereof will be omitted. ' is venturi part 20
It has an input negative pressure chamber 7C and an atmospheric chamber 7d to which the negative pressure of is introduced,
The structural difference is that diaphragms 6a, 5b, and 5c are integrally connected to each other to partition these chambers.

However, as a negative pressure source flow path, which is the main point of the present invention, a plurality of parallel paths are used to introduce suction negative pressure or VC negative pressure to the negative pressure regulator 4', and each path is connected to the negative pressure source through an orifice, depending on the engine operating state. A configuration in which an orifice is selectively opened and closed via a valve device 18a, that is, an orifice 9a (S1) is provided in the negative pressure introduction passage 8a, and this orifice 9a
An orifice 16a is provided in the bypass passage 15a that bypasses the
(S3) and installing the solenoid valve 17a are the same,
This increases responsiveness when driving conditions suddenly change,
When there are few fluctuations, the stability of exhaust gas recirculation control is increased.

Note that the orifice diameter is (S1+S3)>S0>S1 (or S1>S0>S3) and that the solenoid valve 17a
Since the operating conditions and the like under which it operates are completely the same as those in the first embodiment, a detailed explanation will be omitted.

FIG. 3 shows valve devices 18, 18a that change the flow path resistance of the negative pressure introduction passages 8, 8a in the first embodiment (see FIG. 1) and the second embodiment (see FIG. 2). This valve device 18b uses a diaphragm 22 to increase the restriction of the flow path and at the same time detect the operating state.

As shown in FIG. 3, the valve device 18b is connected to a chamber A which communicates with the passage 8 to introduce negative pressure from a negative pressure source such as VC negative pressure or suction negative pressure through a diaphragm 22, and a chamber A that communicates with the passage 8 to introduce negative pressure from a negative pressure source such as VC negative pressure or suction negative pressure. The atmospheric air introduction passage 10 (or passage 1
2), and at this time, the pressure in the B chamber is extremely close to the control negative pressure of the control valve 3 (that is, the difference from the control negative pressure is the negative pressure up to the atmospheric dilution section). pressure loss due to pressure path resistance).

For example, when the negative pressure in chamber A is high (that is, during steady running with a high suction negative pressure), the diaphragm 22 is pulled in the direction of the arrow and comes into close contact with the casing 23, and the fixed negative pressure passage 24 serves as the negative pressure source passage. (orifice 25), the negative pressure supply capability is reduced, and stable exhaust gas recirculation control characteristics and stable drivability based thereon are ensured.

Next, when the negative pressure in chamber A decreases, the diaphragm 22 moves away from the casing 23 due to the elastic force of the spring 26, the bypass passage 27 (orifice 28) opens, and the negative pressure supply capacity increases.

Therefore, response to sudden changes in operating conditions is improved and NOx generation is effectively suppressed.

The effective diameter of the fixed negative pressure passage 24 (orifice 25) is S1,
Assuming that the effective diameter of the bypass passage 27 (orifice 28) is S2, (S1+S3)>So>S1 is the same as in the other embodiments described above.

In this embodiment, as described above, engine suction negative pressure is used as a signal for identifying the operating condition, and at the same time, the valve device 18b is actuated by this suction negative pressure.

In each of the above embodiments, the valve devices 1 8 , 18 a are composed of the negative pressure introduction passages 8 , 8 a and one bypass passage 15 , 15 a that bypasses the negative pressure introduction passages 8 , 8 a , but the bypass passage 1 5 . Needless to say, the number of 15a is not limited to one, and two or more may be provided and operated by switching between them.

That is, for example, if a first bypass passage and a second bypass passage are provided and a solenoid valve is interposed in each of them, the negative pressure passage, the negative pressure passage and the first bypass passage, the negative pressure passage and the second bypass passage, and the negative pressure Four to five switching operations are possible between the passage, the first bypass passage, and the second bypass passage.

Of course, it is not necessary to use all of them.

Note that if it is better to divide the operating region into three or more ranges and change the restriction of the negative pressure passage depending on the recirculation control pattern, good results can be obtained by applying the above-mentioned means.

In this invention, as described above, the negative pressure introduction passage is provided with a valve device that makes its flow path resistance variable, so that responsive exhaust recirculation control characteristics and stable exhaust recirculation control and operability can be achieved depending on the operating conditions. Therefore, it is possible to effectively reduce NOx, and since the structure is extremely simple, it is economical.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the present invention, FIG. 2 is a schematic diagram showing a second embodiment, and FIG. 3 is an enlarged longitudinal sectional view showing another embodiment of the valve device. DESCRIPTION OF SYMBOLS 1... Exhaust recirculation passage, 2... Orifice, 3... Exhaust recirculation control valve, 4... Negative pressure adjustment device, 5a... Throttle valve, 6...
...Diaphragm, 7a, 7b...Chamber, 8, 8a...Negative pressure introduction passage, 9, 9a...Orifice, 10...Atmospheric introduction passage, 11...Passage, 12...Passage, 13...Diaphragm, 14 ...Negative pressure working chamber, 15, 15a... Bypass passage, 16, 16a... Orifice, 17, 17a... Solenoid valve, 18, 18a, 18b... Valve device.

Claims (1)

[Claims] 1. A recirculation control valve that changes the passage area of the exhaust gas recirculation passage is installed, and the negative pressure introduced from the negative pressure source through the negative pressure introduction passage is controlled according to the operating state of the engine. In an exhaust gas recirculation control device, the exhaust gas recirculation control device performs dilution control with the atmosphere through a negative pressure adjustment device that operates in accordance with changing signal pressure, and introduces the exhaust gas into the operating negative chamber of the recirculation control valve via a negative pressure passage. At least one bypass passage is provided that communicates the negative pressure introduction passage upstream of the negative pressure adjustment device with the operating negative pressure passage downstream of the negative pressure adjustment device, and a valve is provided in the bypass passage that opens and closes the passage in response to the operating state. An exhaust gas recirculation control device characterized by being provided with a device. 2. The exhaust gas recirculation strut device according to claim 1, wherein the effective diameter of the bypass passage is reduced by a valve device when the transmission gear position is at the top as an operating state of the engine. 3. The exhaust gas recirculation control device according to claim 1, wherein the effective diameter of the bypass passage is set to zero by a valve device when the throttle opening reaches a predetermined value or more as the operating state of the engine. 4. Claim 1, characterized in that the effective diameter of the bypass passage is reduced by a valve device when the suction negative pressure or the negative pressure generated in the vicinity of the throttle valve exceeds a predetermined value as the operating state of the engine. Exhaust recirculation control device as described in Section 1. 5. Claim 1, characterized in that when the negative pressure generated in the venturi portion of the intake passage exceeds a predetermined value in the operating state of the engine, the effective diameter of the bypass passage is set to zero by a valve device. Exhaust recirculation control device. 6 The negative pressure source is negative pressure generated near the throttle valve, and
The signal pressure is the recirculation passage pressure Pe upstream of the recirculation control valve, and the exhaust recirculation control valve is feedback-controlled so as to keep this pressure Pe constant. The exhaust gas recirculation control device according to any one of the above. 7 The negative pressure source is the negative pressure or suction pressure generated near the throttle valve, and the signal pressure is the negative pressure generated in the venturi part of the intake passage and the pressure Pe' upstream of the reflux control valve in the reflux passage.
According to the increase in the negative pressure generated in the venturi section, the pressure P
The exhaust gas recirculation control device according to any one of claims 1 to 5, characterized in that the exhaust gas recirculation control valve is subjected to feed bath control so as to reduce e'.