JP2000337173A - Exhaust shutter valve of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the step difference feeling of a torque responding to the open motion of an exhaust shutter valve. SOLUTION: An exhaust shutter valve 1 is driven by a negative pressure actuator 23 and closed in order to improve a heating performance at the cold time. The negative pressure is introduced from a negative pressure pump 31 through a three-way solenoid valve 32, but an orifice 36 is interposed in the atmosphere introduction passage 35 communicating at OFF time in order to introduce the atmosphere slowly. In response to the change of an operation condition, when the exhaust shutter valve 1 on the close position is opened, as the opening motion becomes slow, the change of the back pressure becomes also slow and the sudden change of a torque is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an exhaust shutter valve for restricting an exhaust passage in a diesel engine to increase a back pressure of an exhaust system under specific conditions.

[0002]

2. Description of the Related Art For example, a diesel engine for an automobile is known which is provided with an exhaust shutter valve in an exhaust passage in order to promote warm-up in a cold state or to improve the performance of a vehicle compartment heater. The exhaust shutter valve is opened and closed automatically, for example, according to operating conditions or by a driver's switch operation. When the exhaust shutter valve is closed, the back pressure of the exhaust system of the engine increases. Therefore, the required fuel injection amount increases, and the cooling water temperature rises quickly.

As an exhaust shutter valve, a butterfly valve type configuration having a circular valve element is generally used as disclosed in Japanese Patent Application Laid-Open No. 5-71367. Although it opens and closes, it is necessary to allow a certain amount of exhaust flow even when it is fully closed.Therefore, in the fully closed state, there is a small gap between the swing end of the valve body and the exhaust passage inner wall surface. A gap is ensured. Further, in order to avoid an excessive rise in back pressure when the gap is narrowed by the accumulation of carbon, a communication hole having an appropriate opening area is provided in the center of the valve body in addition to securing the gap. Many have been made.

[0004]

As described above, the exhaust shutter valve can be simply switched between the open position and the closed position. For example, when the engine is cold, the exhaust shutter valve is closed. Then, when the exhaust shutter valve opens, the back pressure acting on the exhaust system decreases, and the engine torque suddenly increases, causing the occupant to feel a torque step. Sometimes. In particular, in the case where the switching from the closed state to the open state is automatically performed according to the engine operating conditions such as the number of revolutions, the load, and the cooling water temperature, a torque step occurs at a timing not intended by the driver. is there.

[0005]

The invention according to claim 1 is
In a diesel engine exhaust shutter valve in which a valve body for reducing a passage area is provided in an exhaust passage of a diesel engine, and the opening and closing of the valve body is controlled to be switched according to operating conditions, the valve body is opened from a closed position to an open position. The present invention is characterized in that an opening speed reducing means for slowing down the operation is provided.

That is, the exhaust shutter valve is in the closed position when, for example, the engine is in a cold state and is in a predetermined low speed / low load region. As a premise of the opening / closing control of the exhaust shutter valve, a changeover switch operated by a driver may be provided, and the exhaust shutter valve may be operated only when the switch is ON. When the operating condition of the engine deviates from the predetermined condition, the exhaust shutter valve is switched to the open position. For example, the exhaust shutter valve changes from closed to open due to an increase in load, an increase in the number of revolutions, an increase in the temperature of the cooling water, and the like. In the present invention, when the switching from the closed position to the open position is performed, the opening operation of the valve body is slowed down by the opening speed reducing means. Therefore, no rapid torque fluctuation occurs. The opening speed can be reduced by various means such as mechanical means or electric means.

[0007] Claim 2 which embodies the invention of claim 1
In the invention, the exhaust shutter valve is provided with a negative pressure actuator for driving the opening and closing of the valve body, and is provided with an orifice as the opening speed reducing means for slowing down the pressure change of the negative pressure actuator. And

The invention according to claim 3 is dependent on claim 2, wherein the negative pressure actuator closes the valve body when negative pressure is introduced, and the negative pressure actuator is provided between the negative pressure source and the negative pressure actuator. A three-way solenoid valve is interposed, and the orifice is interposed in an air introduction passage connected to the three-way solenoid valve.

According to a fourth aspect of the present invention, the negative pressure actuator closes a valve body when negative pressure is introduced, and a three-way solenoid valve is interposed between the negative pressure source and the negative pressure actuator. And the orifice is interposed in a negative pressure passage between the three-way solenoid valve and the negative pressure actuator.

That is, in the third aspect of the present invention, the valve element of the exhaust shutter valve is opened by switching the negative pressure actuator to the atmosphere introduction passage via the three-way solenoid valve. By providing the orifice, the negative pressure is reduced, in other words, the introduction of the atmosphere is gradually performed, and the opening operation of the valve body becomes slow. In addition,
When closing from the open position, a negative pressure is quickly introduced,
Closes immediately.

On the other hand, in the invention of claim 4, since the orifice is interposed between the three-way solenoid valve and the negative pressure actuator, both the opening operation and the closing operation are slow.

[0012]

According to the exhaust shutter valve of the diesel engine according to the present invention, when the exhaust shutter valve is switched from the closed position to the open position in accordance with the operating conditions, the opening operation of the valve body becomes slow, Exhaust system back pressure changes slowly. Therefore, unintended sudden torque fluctuation can be avoided, and the driver does not feel uncomfortable.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the structure of an exhaust system of an automotive diesel engine 2 having an exhaust shutter valve 1 according to the present invention. As shown in FIG. 1, a front tube 5 is connected to an exhaust manifold 3 of a diesel engine 2 via a catalytic converter 4, and the front tube 5 is provided with a center tube 6 having a main muffler 8 and a rear muffler 9. Tail tubes 7 are sequentially connected. Note that a flexible tube 10 for intercepting vibration is interposed at an intermediate portion of the front tube 5. The exhaust shutter valve 1 is interposed between the front tube 5 and the center tube 6.

FIGS. 2 and 3 show an exhaust shutter valve 1.
FIG. 3 is a partial cross-sectional view showing the entire configuration, in which a valve housing 11 sandwiched between flanges (not shown) of a front tube 5 and a center tube 6 has an exhaust passage 12 having a circular cross section connected to both tubes 5 and 6. A valve shaft 13 is disposed along a direction perpendicular to the exhaust passage 12, and a disc-shaped valve element 14 is attached to the valve shaft 13. At four corners of the valve housing 11, bolt through holes 19 through which bolts (not shown) to be fastened together with the flanges of the tubes 5, 6 are formed.

The valve shaft 13 is connected to the exhaust passage 12
Has a large diameter, and is rotatably supported by two bearing members 15 and 16 arranged on both sides of the large diameter portion. The large-diameter portion of the valve shaft 13 is cut out in a semicircular cross-section, leaving both ends slightly, and the valve body 14 is fixed thereto by a pair of bolts 17.

Further, as shown in FIG. 2, one end of the valve shaft 13 extends to the side of the valve housing 11 through a seal member 18 adjacent to the bearing member 15, and here, FIG. As shown in the figure, a rod 24 of a diaphragm type negative pressure actuator 23 is linked via a lever 21 and a link 22. Reference numeral 25 denotes a bracket fixed to the side surface of the valve housing 11 by a pair of bolts 26 (see FIG. 2) and supporting the actuator 23. The negative pressure actuator 23
Is a return spring 28 provided in the negative pressure chamber 27.
Thus, the valve element 14 is normally held at the fully open position as shown in the figure, and when a negative pressure is introduced, the valve shaft 13 is rotated to set the valve element 14 to the closed position. .

In the negative pressure chamber 27, as shown in FIG.
A negative pressure is introduced from a negative pressure pump 31 serving as a negative pressure source via a three-way solenoid valve 32. Specifically, the first port of the three-way solenoid valve 32 is connected to the negative pressure pump 31 by the first negative pressure passage 33, and the second port of the three-way solenoid valve 32 is connected to the negative pressure chamber by the second negative pressure passage 34. The air introduction passage 35 is connected to the third port of the three-way solenoid valve 32 and is open to the atmosphere. The three-way solenoid valve 32 connects the first negative pressure passage 33 to the second negative pressure passage 33 when ON, and connects the first negative pressure passage 33 to the atmosphere introduction passage 35 when OFF. In this embodiment, an orifice 36 is interposed in the air introduction passage 35.

The three-way solenoid valve 32 is switched by a control signal of a control unit 37, and basically has an engine speed, a fuel injection amount Q,
It is controlled based on the cooling water temperature. That is, when the engine speed and the fuel injection amount Q are in a predetermined low-speed low-load side closed region as shown in FIG. 4 and the cooling water temperature is equal to or lower than a predetermined temperature (for example, 70 ° C.), 1 is closed, otherwise it is open. A warm-up switch (not shown) that is manually operated is provided in the driver's seat, and the exhaust shutter valve 1 is operated only when the warm-up switch is ON.

Therefore, when the engine is operating in the closed region shown in FIG. 4 in a cold state, the exhaust shutter valve 1 is in the closed position. When entering the open area or when the cooling water temperature becomes equal to or higher than the predetermined temperature, the three-way solenoid valve 32 is switched by the control signal of the control unit 37, the atmosphere is introduced into the negative pressure chamber 27, and the valve element 14 is opened. open.
At this time, the introduction of the atmosphere is slowed down by the orifice 36, so that the valve element 14 is gradually opened.

FIG. 5 collectively shows the state of each part at the time of this opening operation.
And the exhaust shutter valve 1 changes from closed to open as shown in FIG. Then, since the back pressure changes, a torque change occurs as shown in FIG. Here, when the orifice 36 is not provided, the opening changes suddenly as shown by a solid line and a sudden change in torque occurs. However, by providing the orifice 36, the opening changes slowly as shown by a broken line and the acceleration increases. The inclination of the torque change that causes the feeling is small.

Instead of interposing the orifice 36 in the atmosphere introducing passage 35 as described above, the orifice 36 can be interposed in the second negative pressure passage 34 between the three-way solenoid valve 32 and the negative pressure actuator 23. . In this case, the closing operation from the open position to the closed position is also slow.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of an exhaust system of a diesel engine including an exhaust shutter valve according to the present invention.

FIG. 2 is a partial sectional view of an exhaust shutter valve.

FIG. 3 is a partial cross-sectional view of the exhaust shutter valve viewed from different directions.

FIG. 4 is a characteristic diagram showing control regions for opening and closing an exhaust shutter valve.

FIG. 5 is a time chart showing a state change of each part when the exhaust shutter valve is opened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exhaust shutter valve 14 ... Valve 23 ... Negative pressure actuator 31 ... Negative pressure pump 32 ... Three-way solenoid valve 36 ... Orifice

Claims (4)

[Claims] 1. An exhaust shutter valve for a diesel engine, wherein the exhaust passage of the diesel engine is provided with a valve body for reducing the passage area, and the opening and closing of the valve body is controlled to be switched according to operating conditions. An exhaust shutter valve for a diesel engine, comprising an opening speed reducing means for slowing an opening operation to an open position. 2. The exhaust shutter valve according to claim 1, further comprising a negative pressure actuator for opening and closing the valve body, and an orifice for slowing down the pressure change of the negative pressure actuator as the opening speed reducing means. The exhaust shutter valve for a diesel engine according to claim 1, wherein 3. The negative pressure actuator is for closing a valve body when negative pressure is introduced, and a three-way solenoid valve is interposed between a negative pressure source and the negative pressure actuator. The orifice is interposed in an air introduction passage connected to a three-way solenoid valve.
An exhaust shutter valve for a diesel engine as described. 4. The negative pressure actuator is for closing a valve body when a negative pressure is introduced, and a three-way solenoid valve is interposed between a negative pressure source and the negative pressure actuator. The exhaust shutter valve for a diesel engine according to claim 2, wherein the orifice is interposed in a negative pressure passage between the three-way solenoid valve and the negative pressure actuator.