Exhaust pressure control valve

The present invention provides an exhaust gas pressure control valve which allows discharge of exhaust gases from entire cross-sectional area of the exhaust gas pipeline when the exhaust gas pressure control valve completely. An exhaust gas pressure control valve is mounted on a gas pipeline having a first cross-section where exhaust gas from engine communicates and disposed upstream or downstream of a muffler. The exhaust gas pressure control valve comprises: a housing having a first cross-sectional surface and a second cross-sectional surface larger than the first surface and connected to the gas pipelines for communicating the exhaust gas; the valve axis supported along the second cross-section not overlapping with the first cross-section when viewed from the flowing direction, the valve axis supported by the housing in a crossing direction to the flowing direction; and a valve element connected to the valve axis and adjusts flow of the exhaust gas communicating to the gas pipeline.

BACKGROUND

The present invention relates to an exhaust gas pressure control valve disposed in an exhaust system of the engine for reducing the flow of the exhaust gas. Particularly, the present invention relates to an exhaust gas pressure control valve disposed between a muffler and outside or between an engine and muffler which reduces engine noise generated while exhausting gas.

The exhaust gas pressure control valve, which is disposed along the exhaust gas pipeline, is used as an exhaust break system for diesel vehicles such as truck and bus or as a warm-up system while the engine is idling during cold days. Japan unexamined patent publication No. 2011-032955 discloses an exhaust gas control valve which has simple configuration and allows smooth rotation regardless of the size of the exhaust gas pressure. Patent Literature 1: JP Unexamined Patent Publication No. 2011-032955 A1

However, the exhaust gas pressure control valve disclosed in '955 is formed with predetermined thickness, and the valve axis of the exhaust gas pressure control valve is disposed traverse to the center of the exhaust gas pipeline. Therefore, when the exhaust gas pressure system valve opens completely, the valve thickness and valve axis acts as a resistance against the system. In other word, the cross-sectional area of the exhaust gas pipeline becomes smaller by amount of the valve thickness and projection area of the valve axis at an exhaust gas pressure control valve.

SUMMARY

Therefore, the present invention provides an exhaust gas pressure control valve which allows to exhaust gases from entire cross-sectional area of the exhaust gas pipeline when the valve opens completely.

An exhaust gas pressure control valve of a first aspect is that, the exhaust gas pressure control valve is mounted on a gas pipeline having a first cross-section where exhaust gas from engine communicates and is disposed upstream or downstream of a muffler. The exhaust gas pressure control valve comprising; a housing having a first cross-sectional surface and a second cross-sectional surface larger than the first surface and connected to the gas pipelines for communicating the exhaust gas; a valve axis supported along the second cross-section not overlapping with the first cross-section when viewed from the flowing direction and supported by the housing in a crossing direction to the flowing direction; and a valve element connected to the valve axis and adjusts flow of the exhaust gas communicating to the gas pipeline.

An exhaust gas pressure control valve of a second aspect of a present invention further comprises a driving unit for driving the valve element for adjusting flow of the exhaust gas by the valve element. The driving unit can be all types of elastic elements including coil springs for providing elasticity of to a rotation of the valve element. The flow of the exhaust gas is controlled using the elastic elements. An exhaust gas pressure control valve of another aspect is that, the flow of the exhaust gas is closed by tilting the valve element by 45 to 70 degrees relative to the airflow direction.

According to the present invention, when the exhaust gas pressure control valve opens completely, gases are exhausted from entire cross-sectional area of the exhaust gas pipeline.

DETAILED DESCRIPTION

First Embodiment

FIG. 1is a schematic diagram illustrating the exhaust system of a diesel engine (“engine”)1. The exhaust system of engine1comprises a DPF (diesel particulate filter) apparatus2, a first exhaust gas pressure control valve3, a muffler4and a second exhaust gas pressure control valve9. Additionally, the exhaust system of the engine1further comprises an ECU (engine control unit)16for controlling a fuel pump14and a first exhaust gas pressure control valve3of the engine1. An exhaust gas manifold8of the engine1is connected to an exhaust gas pipeline7having a circular cross-section. The DPF apparatus2disposed downstream of the exhaust gas pipeline7comprises a ceramic filter and oxidation catalyst inside the DPF apparatus which collects particulates and graphite in the exhaust gas. The downstream of the DPF apparatus2is connected to the first exhaust gas pressure control valve3via exhaust gas pipeline7. The first exhaust gas pressure control valve3is disposed to control gas pressure exhausted from the engine1. The muffler4is connected downstream of the first exhaust gas pressure control valve3via the exhaust gas pipeline7. The muffler4reduces exhaust noise generated during discharge of the exhaust gas. The downstream of the muffler4is connected to the second exhaust gas pressure control valve9via the exhaust gas pipeline7. The second exhaust gas pressure control valve9is disposed to improve fuel efficiency of engine1. The second exhaust gas pressure control valve9also reduces exhaust noise and collects particulates and graphite in the DPF apparatus2.

On the DPF apparatus2, the pressure sensor12for detecting pressure of the exhaust gas is disposed upstream of the exhaust gas pipeline7and the pressure sensor13for detecting pressure of the exhaust gas is disposed downstream of the exhaust gas pipeline7. The DPF apparatus2purifies the exhaust gas by collecting particulates and graphite in the exhaust gas. The exhaust gas purified in the DPF apparatus2is transferred to the first exhaust gas pressure control valve3and the muffler4. The exhaust gas is discharged through the second exhaust gas pressure control valve9disposed downstream of the muffler4.

In the first embodiment, the second exhaust gas pressure control valve9is mounted downstream of the muffler4of a conventional vehicle. The first exhaust gas pressure control valve3is a general pressure control valve mounted to the conventional vehicle. Thus, the pressure control valve is disposed in traverse to a center of a pressure gas pipeline with circular valve axis. On the other hand, a valve axis of the second exhaust gas pressure control valve9is situated at a position outside of the circular cross-sectional area of the exhaust gas pipeline. The second exhaust gas pressure control valve9will be explained in detail.

FIGS. 2A-2Dare the schematic diagrams of the second exhaust gas pressure control valve9A of the second exhaust gas pressure control valve9.FIG. 2Ais a cross-sectional diagram of the second exhaust gas pressure control valve9A with a valve element92being opened.FIG. 2Bis a cross-sectional diagram of the second exhaust gas pressure control valve9A with a valve element92being closed.FIG. 2Cis a cross-sectional diagram ofFIG. 2Btaken along C-C line and viewed from bore91to the upstream direction.FIG. 2Dis a cross-sectional diagram ofFIG. 2Btaken along D-D line and viewed from bore91to the downstream direction. The arrows indicate airflow direction of the exhaust gas.

Configuration of Second Exhaust Gas Pressure Control Valve9A

As shown inFIGS. 2A and 2B, a housing95A of the second exhaust gas pressure control valve9A comprises an opening97. The downstream exhaust gas pipeline7of muffler4is attached to the opening97. An opening99is disposed downstream of the housing95A in which the exhaust gas pipeline7is mounted thereon. The exhaust gas pipeline7of the housing95A may be eliminated and the gas may be exhausted directly from the opening99.

The cross-sectional area CS1of the bore71of the exhaust gas pipeline7is smaller than the cross-sectional area CS2of the bore91of the second exhaust gas pressure control valve9A. As illustrated inFIGS. 2C and 2D, the cross-section of the bore91of the housing95A has four sides with one side formed in circular arch. The diameter of the arch is slightly larger than the outer surface of the circular exhaust gas pipeline7. The valve axis96is disposed on the housing95A so that the axis is parallel to one straight side of the opposing arch. In other word, the valve axis96is supported by the housing95on the direction crossing the flowing direction of the exhaust gas.

The valve element92is a flat panel having a similar shape as a cross-section of the bore91and formed large enough to seal the bore71of the exhaust gas pipeline7. The valve element92may be connected to the valve axis96in a rotatable manner, or the valve axis96and the valve elements may be fixed together with the valve axis96connected to the housing95A in a rotatable manner. The rotation of the valve element92seals or opens the bore71of the exhaust gas pipeline7.

A coil spring94is inserted on both sides of the valve axis96for pushing the valve element92in one direction. A part of the coil spring extends to a center of the valve element92which opposes to the flowing direction of the exhaust gas. In other words, when the exhaust gas is not flowing, the coil spring94forces the valve element92to stand at 90-degrees angle relative to a flowing direction of the exhaust gas and closes the exchange gas pipeline7. When the exchange gas is flowing with little intensity or low pressure, the valve element92tilts by 40 to 80 degrees to the flowing direction and maintains the exchange gas pipeline7open. When the exhaust gas is flowing with large intensity or high pressure, the coil spring94cannot resist against the flow of exhaust gas, the valve element92tilts by 30-degrees to 0-degrees to the flowing direction, thus opens the exchange gas pipeline7. In other word, the valve element92is capable of adjusting the opening of the exchange gas pipeline7depending on the exhaust gas pressure.

As illustrated inFIG. 2A, the valve axis96is disposed along a cross-section of the housing95A which does not overlap with the cross-section of the exhaust gas pipeline7when viewed from the flowing direction. Nothing obstructs the cross-sectional area CS1of the exchange gas pipeline7when the valve element92tilts toward the flowing direction to almost 0-degrees angle. Therefore, when the vehicle is moving at a high velocity, the gas goes out smoothly from the exhaust gas pipeline7. This not only improves the fuel combustion but also enhances the rotation startup and response. On the other hand, the second exhaust gas pressure control valve9A does not lose its power and torque.

The strength of coil spring should be adjusted depending on the displacement of the engine1and type of engines, such as gasoline engine instead of diesel engine, 2-stroke or 4-stroke engine, 4-cylinder or 6-cylinder engines etc. However, the valve element92needs to be tilted to almost 0-degrees relative to the flowing direction by receiving maximum exhaust gas from the engine1. Although the first embodiment is described with a coil spring, this may be replaced with different types of elastic elements, such as board spring or torsion bar, which helps the rotation of valve element92.

The valve element92, housing95A and valve axis96are made out of cast-metal, aluminum coated sheet, titan, Inconel or stainless steel. The stainless steel is most preferred material considering its aesthetics and resistance against temperature of the exhaust gas.

Operation in the First Embodiment

The operation for the first embodiment is described hereinbelow. The ECU16inputs the detection signals of each sensor for detecting operation condition of engine1. ECU16controls the amount of fuel supply and timing for supplying fuels to engine1by controlling the engine pump14based on the detection signals. The exhaust gas from engine1flows into the DPF apparatus2via exhaust gas manifold8and exhaust gas pipeline7.

The DPF apparatus2collects particulates and graphite. As the pressure loss of the DPF apparatus2increases, such loss appears as a pressure difference between the upstream and downstream of the DPF apparatus2. The ECU16calculates a pressure difference detected by an upstream pressure sensor12and a downstream pressure sensor13and when the pressure difference exceeds a predetermined value, closes the first exhaust gas pressure control valve3for regenerating filter for DPF apparatus2.

Thereby, the exhaust gas pressure of engine1increases, which leads to an increase of fuel supplied to the engine1. The exhaust gas containing the unburnt component flows into the DPF apparatus2, which is supplied to the oxidation catalyst on the upstream filter. The unburnt component supplied to the oxidation catalyst increases the gas temperature within the catalyst due to the oxidation, which burns the particulates and graphite collected by the filter. Consequently, the filter for the DPF apparatus2is regenerated. When a regeneration of filter for DPF apparatus2is completed, ECU16opens the first exhaust gas pressure control valve3and restarts the normal operation.

Some vehicles are equipped with an idling stop mechanism which prevents exhaust gas from unnecessary release when the vehicle is in stop state, meaning that the engine1is stopped during the normal operation. If the second exhaust gas pressure control valve9A does not exist, the first pressure gas control valve3is opened, which allows the cold air from outside flowing into the proximity of engine1via pressure gas pipeline7. Such back current causes the temperature decrease of the engine1. Since the ECU16mainly reads the water temperature map, the fuel pump14supplies more fuel to the engine1when the vehicle starts moving than when the engine1is in the state of high temperature. Consequently, the idling stop mechanism causes adverse effect as far as the fuel combustion is concerned.

On the other hand, when the second exhaust gas pressure control valve9A exists, the valve element92maintains the pressure gas pipeline7in a closed state, which prevents the cold air from outside flowing into the engine1. This maintains the temperature of engine1regardless of the condition of the engine1and allowing the fuel pump14supplying appropriate amount of engine1when the vehicle starts operating.

Even when the vehicle is moving under the normal operation condition, the exhaust gas is not constantly flowing from the engine1. There are periods that the exhaust gas is not flowing into the exhaust gas pipeline7even if the engine is multi-cylinder 2-stroke or 4-stroke engines. The exhaust gas does not flow into the exhaust gas pipeline7during low-speed traveling or in a state of a temporary stop during the city drive, which allows the cold air from outside flowing into the DPF apparatus2, exhaust gas pipeline7or muffler4. This causes the temperature decrease of engine1and when the vehicle starts moving, the fuel pump14supplies more fuel to engine1than when the engine1is maintained at a high temperature.

On the other hand, if the second exhaust gas pressure control valve9A is mounted, the valve element92opens the exhaust gas pipeline7only slightly at low speed. Additionally, the valve element92closes the exhaust gas pipeline7when the cold air from outside is flowing. Therefore, even if the engine1is in the stopping state, the temperature of the engine1is maintained, thus improves the fuel efficiency. During the high-speed driving, the valve element92tilts toward almost 0-degrees direction in relative to the flowing direction, allowing the gas to exhaust from entire cross-section of the exhaust gas pipeline7and maximizes the engine capability.

Example of Diesel Engines

The fuel improvement was measured by driving Mitsubishi Canter (KK-FE82DG), which has a diesel engine of 4,890 cc displacement. The experiment was performed by driving at a same road under same speed.Driving distance before mounting second exhaust gas pressure control valve9A: 4.3 km per liter.Driving distance after mounting second exhaust gas pressure control valve9A: 5.3 km per liter.The fuel efficiency increased by 23.3% with the second exhaust gas pressure control valve mounted onto the downstream of muffler4.

Example 2 for Gasoline Engine

The first embodiment was based on the exhaust system for diesel engine. However, this may be applied to the gasoline engine in a similar manner.

The fuel improvement was measured by driving Mitsubishi Pajero Mini (E-H56A), which has a gasoline engine of 660 cc displacement. The experiment was performed by driving at a same road under same speed.Driving distance per liter before mounting second exhaust gas pressure control valve9A: 6.4 km per liter.Driving distance per liter after mounting second exhaust gas pressure control valve9A: 9.5 km per liter.The fuel efficiency increased by 46.2% with the second exhaust gas pressure control valve9A mounted onto the downstream of muffler4.

Alternative Embodiment 1: Configuration of Second Exhaust Gas Pressure Control Valve9B

FIGS. 3A-3Care the schematic diagrams of the second exhaust gas pressure control valve9B.FIG. 3Ais a cross-sectional diagram indicating a valve element92with the second exhaust gas pressure control valve9B is opened.FIG. 3Bis a cross-sectional diagram indicating a valve element92with the second exhaust gas pressure control valve9B is closed. The same numerals were assigned for the alternative embodiment 1 as the previously-explained second exhaust gas pressure control valve9A.

As illustrated inFIGS. 3A and 3B, the housing95B of the second exhaust gas pressure control valve9B comprises an opening97with an exhaust gas pipeline7mounted downstream of the muffler4of the opening97. An oblique opening73opened at 70 to 45 degrees from a flowing direction of exhaust gas is formed on an end of the exhaust gas pipeline7. An opening99B is disposed downstream of the housing95B. The exhaust gas pipeline7is not disposed downstream of the housing95B.

The cross-section of the housing95B has four sides with one side formed in circular arch. Such configuration is similar to the cross-section of housing95A. The difference between two structures is that, for this embodiment, the height becomes shorter as it reaches toward downstream. The cross-sectional area of the opening99B can be substantially similar as the cross-sectional area for CS1of the exhaust gas pipeline7. On the other hand, the cross-sectional area CS2of the second exhaust gas pressure control valve9B with the valve element92attached is larger than the cross-sectional area CS1of the exhaust gas pipeline7.

When the exhaust gas is not flowing, the valve element92tilts by 70 to 45 degrees relative to the flowing direction and closes communication path of the exhaust gas. When the exhaust gas is flowing with little intensity or low pressure, the valve element92tilts by 40 to 20 degrees relative to the flowing direction and opens the exhaust gas pipeline7. When the exhaust gas is flowing with large intensity or high pressure, the coil spring94cannot resist against the flow of exhaust gas, the valve element92tilts by 20-degrees to 0-degrees relative to the flowing direction, thus opens the exchange gas pipeline7.

In the aforementioned second exhaust gas pressure control valve9A, when the valve element92is slightly opened, the exhaust gas flows from the exhaust gas pipeline to the bore91at 90-degrees angle from the flowing direction of the exhaust gas. This is difficult to exhaust the gas to outside direction. For second exhaust gas pressure control valve9B, when the exhaust gas flows with small intensity or low pressure and the valve element92is opened slightly, the exhaust gas flows at 70 to 45 degrees from the flowing direction of the exhaust gas, thus allowing the gas flow in straight direction. Therefore, the gas is easily exhausted outside direction with ease.

Additionally, since it is unnecessary to tilt the valve element92to 90-degrees angle from the flowing direction, the height (the perpendicular direction inFIGS. 3A and 3B) of the housing95B can be formed lower than the housing95A's. For second exhaust gas pressure control valve9B, the angle of the oblique opening73of the exhaust gas pipeline7is 70 to 45 degrees relative to the flowing direction of the exhaust gas. This may be formed at 45 to 30 degrees from the flowing direction.

Second Alternative: Configuration of Second Exhaust Gas Pressure Control Valve9C

FIG. 3Cis a cross-sectional diagram indicating a valve element92with the second exhaust gas pressure control valve9C being opened. For second exhaust gas pressure control valve9B, the oblique opening73was formed on the exhaust gas pipeline7. For second exhaust gas pressure control valve9C, although the opening of the exhaust gas pipeline7is orthogonal to the flowing direction, the valve element92is slanted by 70 to 45 degrees relative to the flowing direction and closes communication path of exhaust gas.

The housing95of the second exhaust gas pressure control valve9C includes an opening97C with the exhaust gas pipeline7attached downstream of muffler4. The edge of the exhaust gas pipeline7is formed as an opening and orthogonal to the flowing direction of exhaust gas. An opening99C is formed downstream of the housing95C. The exhaust gas pipeline7is not disposed downstream of the housing95C. The housing95C and housing95B has same cross-sections.

The housing95C has a groove93aand a rib93b, which allows the closed valve92to tilt toward 70 to 45 degrees relative to the flowing direction. When the exhaust gas is not flowing, the coil spring94forces the valve element92to tilt by 70 to 45 degrees relative to the flowing direction and allowing the valve element92contacting the groove93and rib93b, thus closing the communication path of the exhaust gas inside the bore91. Thereby, the second exhaust gas pressure control valve9C provides the same effect as the second exhaust gas pressure control valve9B.

Configuration of Second Embodiment

FIG. 4is a schematic diagram of the exhaust system of the diesel engine1. The exhaust system of engine1comprises a DPF apparatus2, a third exhaust gas pressure control valve19and a muffler4. The exhaust system of the engine1also comprises an ECU16for controlling a fuel pump14of the engine1and a driving motor6for the third exhaust gas pressure control valve19. The exhaust gas manifold8of the engine1is connected to the exhaust gas pipeline7having a circular cross-section. The DPF apparatus2is disposed downstream of the exhaust gas pipeline7. The downstream side of the DPF apparatus2is connected to the third exhaust gas pressure control valve19via the exhaust gas pipeline7. The third exhaust gas pressure control valve19is disposed to control and shield the exhaust gas pressure expelled from engine1. The muffler4is connected downstream of the third exhaust gas pressure control valve19via the exhaust gas pipeline7. The exhaust gas is discharged through the muffler4.

On the upstream and downstream of the exhaust gas pipeline7of the DPF apparatus2, the pressure sensors12and13are disposed for detecting pressure of the exhaust gas. The details regarding the third exhaust gas pressure control valve19which is driven by a driving motor6is explained herein below.

Configuration of Third Exhaust Gas Pressure Control Valve19A

FIGS. 5A-5Care the schematic diagrams of the third exhaust gas pressure control valve19A of the third exhaust gas pressure control valve19.FIG. 5Ais a cross-sectional diagram illustrating a valve element192A with the third exhaust gas pressure control valve19A being opened.FIG. 5Bis a cross-sectional diagram illustrating a valve element192A with the third exhaust gas pressure control valve19A being closed.FIG. 5Cis a cross-sectional diagram ofFIG. 5Aalong the C-C line. The arrows indicate airflow direction of the exhaust gas.

As illustrated inFIGS. 5A and 5B, the housing195A of the third exhaust gas pressure control valve19A comprises an opening197. The exhaust gas pipeline7of the DPF apparatus2is mounted downstream of the opening197. An opening199is formed downstream of housing195A with the exhaust gas pipeline mounted thereon. The valve192A is a flat panel having the same shape as the cross-section of the bore191and is shaped large enough to seal the bore71of the exhaust gas pipeline7.

The cross-sectional area CS1of the bore71of the exhaust gas pipeline7is smaller than the cross-sectional area CS2of the bore191of the third exhaust gas pressure control valve19A. As shown inFIG. 5C, the cross-section of the bore191of the housing195A has four sides with one side formed in circular arch. The valve axis196is disposed on the housing195A so that the axis is parallel to one straight side of the opposing arch. The valve axis196is supported by the housing195A on the direction crossing the flowing direction of the exhaust gas.

The valve element192A and valve axis196are fixed to each other and the valve axis196are supported in rotatable manner by a bearing61inside the housing195A. One edge of the valve axis196protrudes outward of the housing195A. The protruding portion is clamped by seal rings62from both sides, preventing the exhaust gas from leakage. One edge of the valve axis196is connected to the rotating axis64of the driving motor6and the coupling63.

The driving motor6comprises a casing66, a stator coil65disposed on inner wall of the casing66, a pair of bearings61, a rotating axis64situated between the bearings61in a rotatable manner and a rotor67mounted on the rotating axis64.

The driving motor6rotates the valve element192A by 0 degrees (seeFIG. 5A) and 90 degrees (seeFIG. 5B) relative to the flowing direction and closes the exhaust gas pipeline7. During the closing state, the valve element192A is disposed at a position not overlapping with the cross-section of the exhaust gas pipeline7and allows to discharge gases from entire cross-sectional areas CS1of the exhaust gas pipeline7.

Operation of the Second Embodiment

FIG. 6is a flowchart illustrating operation of the second embodiment.

In step S11, the operator pushes the engine start button. The engine1starts operation and the ECU16calculates the pressure difference detected by the upstream pressure sensor12and downstream pressure sensor13. In step S15, the system determines whether the pressure difference exceeds a predetermined value. If the pressure difference exceeds the predetermined value (YES), the ECU16rotates the driving motor6and closes the third exhaust pressure control valve19for a predetermined period of time and regenerates the filter for DPF apparatus2. This allows the flow of exhaust gas including the unburnt fuel into the DPF apparatus2and burns the particulates and graphite collected by the filter. Thereby the filter for DPF apparatus2is regenerated (step S19). When the filter regeneration is completed, the ECU16rotates the driving motor6in opposite direction and opens the third exhaust gas pressure control valve19in a controlled manner (step S21). Then, the step S13is restarts.

If the pressure difference is within the predetermined value during step S15(NO), the operation is performed under a normal condition. During the normal operation, the system detects the stepping-in amount of accelerator pedal signal or the pressure signal from the pressure sensors12or13(step S23). The ECU16drives the driving motor6based on the detected signals and rotates the rotating axis64of the third exhaust gas pressure control valve19(step S25). When the ECU16receives the signal indicating that the stepping-in amount of accelerator pedal signal is high, ECU16opens the valve element192A of the third exhaust gas pressure control valve19almost to 0 degrees in relation to the flowing direction of the exhaust gas. If the ECU receives the signal indicating that the stepping-in amount of accelerator pedal signal is low, the ECU16opens the valve element192A of the third exhaust gas pressure control valve19almost to 85 degrees in relation to the flowing direction of the exhaust gas. Additionally, the system may be constituted so that the valve element192A opens widely when the pressure from the pressure sensor13is large and the valve192A opens slightly when the pressure is small. The ECU16may arrange the rotation amount of the rotation axis64of the driving motor6by combining the signal of the stepping-in amount of accelerator pedal signal and pressure signals from pressure sensors12and13.

For idling stop mechanism which stops the engine during parking and under suspension, the third exhaust gas pressure control valve19is in closed state while the engine1is stopped.

The system shuts down when the operator shuts down the engine start button and continues driving if the start button is not turned off (step S27).

Alternative 1: Configuration of Third Exhaust Gas Pressure Control Valve19B

FIGS. 7A and 7Bare the schematic diagrams illustrating the third exhaust gas pressure control valve19B with different configuration.FIG. 7Ais a cross-sectional diagram illustrating the valve element192B with the third exhaust gas pressure control valve19B being opened.FIG. 7Bis a cross-sectional diagram illustrating the valve element192B with the third exhaust gas pressure control valve19B being closed. The same numerals were assigned for third exhaust gas pressure control valve19B as the previously-explained third exhaust gas pressure control valve19A.

As shown inFIGS. 7A and 7B, a housing195B of the third exhaust gas pressure control valve19B comprises an opening197, and a downstream exhaust gas pipeline7of the DPF apparatus2is attached to the opening197. The edge of the exhaust gas pipeline7is an opening which is orthogonal to the flowing direction of the exhaust gas pipeline7. The opening199B is disposed downstream of the housing195B. The upstream exhaust gas pipeline7is disposed on muffler4of the opening199B.

The cross-section of the housing195B has four sides with one side formed in circular arch. Such configuration is similar to the cross-section of housing195A. The difference between two structures is that the height becomes shorter as it reaches toward the downstream. The opening199B has substantially similar cross-sectional area as the cross-sectional area for CS1of the exhaust gas pipeline7. On the other hand, the cross-sectional area CS2of the third exhaust gas pressure control valve19B with the valve element192attached is larger than the cross-sectional area CS1of the exhaust gas pipeline7.

The housing195B has a groove193aand a rib193b, which allows the closed valve192B slanting toward 45 degrees from the flowing direction. When the exhaust gas is not flowing, the coil spring94forces the valve element92to tilt by 45 degrees from the flowing direction and allowing the valve element192B contacting the groove193aand rib193b, thus shutting the communication path of the exhaust gas inside the bore191. The driving motor6and the valve element192B opens based on the stepping-in amount of the pedal signal or pressure signals from pressure sensors12or13.

The valve element192B has a front side192pand a back side192r. The back side192ris formed in a parabolic path from the tip to the root of the valve axis196. The back side192rformed in a curved shape allows the minor adjustment of the flow amount of the exhaust gas from the valve element192B when the minute exhaust gas is flowing during the closed state of the valve element192B.

DESCRIPTION OF REFERENCE NUMERALS