JP2002054512A - Exhaust gas recirculating valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To steplessly control a recirculating flow amount of exhaust gas. SOLUTION: This exhaust gas recirculating valve (EGR valve) 10 has a butterfly valve 12 interposed in an exhaust gas recirculating passage 4 to adjust a flow amount of exhaust gas 6, a feed screw mechanism 40 converting rotation of a rotary shaft 33 of a motor 30 into a linear motion, a link mechanism 20 transmitting the linear motion of the feed screw mechanism 40 to the butterfly valve 12, and a rotational angle detector 36 detecting a rotational angle of the motor 30. When the motor 30 is positively rotated, the butterfly valve 12 is turned in an opening direction by the feed screw mechanism 40 and the link mechanism 20. By detecting a turn amount, that is, opening of the butterfly valve 12 as a rotational angle of the rotary shaft 33 by the rotational angle detector 36 to be feedback controlled, the opening of the butterfly valve 12 is steplessly controlled by controlling the rotational angle of the motor 30. Accordingly, an engine can be accurately controlled by steplessly controlling exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation valve (Exhaust Gas Recirculation).
n Valve. Hereinafter, it is called an EGR valve. In particular, the present invention relates to a technology for continuously controlling the flow rate of exhaust gas recirculation.
The present invention relates to a technology effective for use in an R valve.

[0002]

2. Description of the Related Art One of the methods for reducing exhaust gas components, particularly NOx, of an automotive diesel engine is EGR.
There is a law. This means that part of the exhaust gas from the engine is returned to the intake system, mixed with fresh air (intake air) and sent to the combustion chamber, thereby reducing the excess oxygen concentration of the air taken into the combustion chamber, and This is a method in which the combustion temperature is reduced by an amount corresponding to depriving the combustion heat to suppress the generation of NOx.

[0003] The EGR method reduces the pumping loss of the engine (the work of sucking intake air by the piston), so that the mechanical efficiency of the engine can be improved accordingly. On the other hand, the thermal efficiency is reduced by the amount that the unburned gas deprives the combustion heat. Therefore, in order to appropriately reduce NOx without reducing the efficiency of the engine, the EGR valve is configured to be controlled by a computer, and the amount of the EGR gas is automatically adjusted according to the operating conditions (output, rotation speed) of the engine. Control is being done.

Generally, in a conventional EGR valve,
A structure in which a poppet valve is driven by a piston and a cylinder is employed. In this EGR valve, since the opening degree of the poppet valve is controlled stepwise by the stroke of the piston, the flow rate at which the exhaust gas is recirculated cannot be optimally controlled.

Therefore, the poppet valve is connected to an electric motor (hereinafter, referred to as an electric motor).
It is called a motor. EG configured to be driven by
An R valve has been proposed. In this EGR valve, the motor can control the degree of opening of the poppet valve steplessly, so that the flow rate of exhaust gas recirculation can be optimally controlled.

[0006]

However, in the EGR valve which controls the opening of the poppet valve steplessly by using the above-mentioned motor, the opening of the poppet valve is affected by the pressure of the exhaust gas applied to the valve body of the poppet valve. When the valve is opened, a large force is required for the motor. For this reason, in this type of conventional EGR valve, various structures have been proposed to avoid the influence of the pressure of exhaust gas applied to the valve element of the poppet valve when the valve is opened. The increase is inevitable.

A first object of the present invention is to provide an exhaust gas recirculation valve which has a simple structure and can continuously control the flow rate of exhaust gas recirculation. A second object of the present invention is to allow the butterfly valve to close when the electric motor fails. A third object of the present invention is to prevent wear of the butterfly valve.

[0008]

According to a first aspect of the exhaust gas recirculation valve according to the present invention, there is provided a butterfly valve interposed in the exhaust gas recirculation passage for adjusting the flow rate of the exhaust gas. An electric motor for opening and closing the butterfly valve,
A feed screw mechanism for converting the rotation of the rotating shaft of the electric motor into a linear motion, a link mechanism for transmitting the linear motion of the feed screw mechanism to the butterfly valve, and a rotation angle detecting means for detecting a rotation angle of the electric motor It is characterized by having.

In the second means, the feed screw mechanism is biased by a return spring in a direction in which the butterfly valve closes.

In the third means, a link mechanism for transmitting the linear motion of the feed screw mechanism to the butterfly valve includes a lever and a link bar connected to the lever, and the link mechanism is It is characterized in that a stopper is provided for the lever to abut on at a position where the butterfly valve that opens and closes by the rotation of the lever is closed.

In the above-mentioned first means, when the electric motor is rotated forward, the butterfly valve is rotated in the opening direction by the feed screw mechanism and the link mechanism. The amount of rotation, that is, the opening of the butterfly valve is controlled by being detected by the rotation angle detecting means as the rotation angle of the electric motor. Therefore, the opening degree of the butterfly valve, that is, the flow rate of exhaust gas recirculation, can be controlled steplessly by controlling the rotation angle of the electric motor.

According to the second means, even when the electric motor stops operating due to a failure, the butterfly valve can be closed by the biasing force of the spring.

According to the third means, since the lever comes into contact with the stopper at the position where the butterfly valve is closed, it is possible to prevent an excessive force from acting on the butterfly valve and to prevent wear of the butterfly valve. can do.

[0014]

FIG. 1 is a partially omitted front sectional view showing a closed state of an EGR valve according to an embodiment of the present invention. FIG. 2 is a partially cutaway front view in which the EGR valve is open and partly omitted. FIG. 3 is a schematic diagram showing a system for arranging and controlling the EGR valve in the intake and exhaust system of the engine.

In the present embodiment, the EG according to the present invention is used.
The R valve is configured to recirculate exhaust gas of a diesel engine mounted on a heavy-duty truck, and as shown in FIG.
The GR valve 10 is interposed in the exhaust gas recirculation passage 4 that connects the intake passage 2 and the exhaust passage 3 of the diesel engine 1 used for a heavy truck. That is,
The EGR valve 10 includes a butterfly valve 12. The butterfly valve 12 is disposed in the exhaust gas recirculation passage 4. A bracket 11 is attached to a valve box 14 of the butterfly valve 12. An electric motor 30, which will be described later, is attached thereto.

As shown in FIGS. 1 and 2, the butterfly valve 12 has a cylindrical valve box 14 having flange portions at both ends where a valve passage 13 is formed. It is interposed in the gas recirculation passage 4.
A valve shaft 15 is rotatably supported on the valve box 14 so as to be orthogonal to the center line of the valve passage 13, and the valve body 16 of the butterfly valve 12 is fixed to the valve shaft 15. The valve body 16 is formed in an elliptical flat plate shape corresponding to the cross-sectional shape of the valve passage 13, and is set so as to completely close the valve passage 13 at a predetermined angle.

An intermediate portion of a lever 21 of a link mechanism 20 is fixed to an outer end of the valve box 14 of the valve shaft 15, and the valve body 16 fixed to the valve shaft 15 is turned by the lever 21. The valve passage 13 is opened and closed by being operated. One end of a link bar 22 is rotatably connected to one free end of the lever 21 by a pin 23, and a rod 43 of a feed screw mechanism described later is rotated by the pin 24 to the other end of the link bar 22. They are freely connected. The bracket 11 is provided with a stopper 25 for regulating the rotation angle of the lever 21. In the present embodiment, the position of the stopper 25 can be adjusted by the bolt 25a and the nuts 25b, 25b. The stopper 25 regulates the rotation angle of the lever 21 in a state where the valve body 16 fully closes the valve passage 13, so that an excessive force is not applied to the tip portion of the valve body 16, To prevent wear.

The bracket 11 is provided with a motor 30 for driving the butterfly valve 12 and a feed screw mechanism 40. The motor 30 is configured to be rotationally driven by the motor drive circuit 31 shown in FIG.
The front cover 32 of the motor 30 is mounted on the end of the bracket 11 opposite to the butterfly valve 12.
A rotation shaft 33 of the motor 30 protrudes from the front cover 32, and a feed screw shaft 48 of a feed screw mechanism 40 is connected to the rotation shaft 33 via a coupling 34 and a detent pin 35 so as to rotate integrally. .

On the front cover 32 side of the coupling 34, a disk magnet 37 which is a detection element for detecting the rotation angle of the motor 30 is fitted. The disk magnet 37 is formed in a circular ring shape. I have.
On the other hand, a part of the front cover 32 protrudes in a disc shape toward the coupling 34, and a spigot member 32a is attached so as to fit exactly into the disc protruding portion. A printed wiring board 38 is fixed to the spigot member 32a with screws 32b.
A Hall IC 39 for detecting the magnetic pole of the disk magnet 37 is provided on the printed wiring board 38.
And is fixed so as to face. The Hall IC 39 transmits a detection signal to the controller 5 shown in FIG. 3, and the controller 5 performs feedback control of the motor drive circuit 31 based on the transmission from the Hall IC 39.

The feed screw mechanism 40 has a yoke 41 formed in a cylindrical shape. The yoke 41 is arranged concentrically with the axis of the motor 30 and is fixed to the motor cover 30a by bolts (not shown). Motor 30 of yoke 41
A bush 42 is fitted and fixed to the end opposite to the end, and a rod 43 is disposed on the bush 42 on an extension of the rotating shaft 33 of the motor 30 and is supported slidably in the axial direction. . A link bar 22 of a link mechanism 20 is rotatably connected to an end of the rod 43 opposite to the motor 30 by a pin 24. Motor 30 for rod 43
A female screw member holder 47A is protruded from an end on the side toward the outside in the radial direction in a flange shape, and presses and holds the spring seat 45 and the bush 42 formed in a truncated conical cylindrical shape in the axial direction of the rod 43. It is supposed to. A return spring 46 is interposed between the yoke 41 and the spring seat 45 in a compressed state, and the return spring 46 constantly urges the rod 43 toward the motor 30. 2, between the end of the yoke 41 on the butterfly valve 12 side and the end of the rod 43 on the butterfly valve 12 side.
A dust cover 49 is attached. The inside of the yoke 41 is sealed by the O-ring 50 and the seal 51.

The rod 43 is formed to be hollow, and a mounting hole 4 formed in an end of the rod 43 on the motor 30 side.
A female screw member 47 is press-fitted into 3a and held by a female screw member holder 47A so as to move integrally therewith. A feed screw shaft 48 is screwed into the female screw member 47. The end of the feed screw shaft 48 on the motor 30 side is connected to the rotating shaft 33 of the motor 30 via a coupling 34 and a pin 35 so as to rotate integrally. The lead angle β of the female screw member 47 and the feed screw shaft 48 is set so as to satisfy the following expression (1). In the equation, Tc is the cogging torque of the motor 30 (torque required to rotate the motor when the motor is not energized), P is the elastic force of the return spring 46, and F is the elastic force P of the return spring 46. The force μ to rotate the feed screw shaft 48, that is, the rotation shaft 33 of the motor 30, is the friction coefficient of the screw surface between the feed screw shaft 48 and the female screw member 47, Φ
Is the friction angle, p is the pitch of the feed screw shaft 48, and D is the effective diameter of the feed screw shaft 48.

F × D / 2> Tc (1) F = P × tan (β−Φ) β = tan ⁻¹ (p / π × D) Φ = tan ⁻¹ μ

Next, the operation will be described.

In the state shown in FIG. 1, when the rotation shaft 33 of the motor 30 is rotated forward and the feed screw shaft 48 is rotated forward through the coupling 34 and the rotation preventing pin 35, the state shown in FIG. As shown, the rod 43 is connected to the motor 30 via the feed screw shaft 48 and the female screw member 47.
Moved in the opposite direction to the side. The movement of the rod 43 is converted into a rotational movement and transmitted to the valve shaft 15 of the butterfly valve 12 by the link mechanism 20, so that the valve element 16 fixed to the valve shaft 15 opens the valve passage 13. At this time, as shown in FIG.
The pressure of the exhaust gas 6 applied to the valve shaft 15 is equal to the upper and lower pressures with respect to the valve shaft 15, so that the rotational torque of the valve shaft 15 due to the pressure of the exhaust gas 6 is canceled out, and the motor 30 can open the valve body 16 with a small force. it can.

In the exhaust gas recirculation passage 4 in which the EGR valve 10 is provided, the valve passage 1 is rotated by the rotation of the valve body 16.
3, the exhaust gas 6 from the exhaust passage 3 of the diesel engine 1 is supplied to the valve passage 13 of the exhaust gas recirculation passage 4 as shown in FIG. Through the intake passage 2. At this time, since the flow coefficient of the butterfly valve 12 is large, a large amount of exhaust gas 6 can be recirculated even if the pressure difference between the exhaust passage 3 side and the intake passage 2 side of the valve body 16 is small.

In the state shown in FIG. 2, even when the power supply from the motor drive circuit 31 is stopped, the elastic force of the return spring 46 applies the spring seat 45, the female screw member holder 47A and the rod 43 to the female screw member 47. Join through. At this time, since the lead angle β of the female screw member 47 and the feed screw shaft 48 is set so as to satisfy the above-mentioned expression (1), the feed screw shaft 48 is moved with respect to the female screw member 47 by the elastic force of the return spring 46. Is rotated in reverse. With the reverse rotation of the feed screw shaft 48, the rod 43 fixed to the female screw member 47 is relatively moved in the direction of the motor 30. The movement of the rod 43 is converted into a rotational movement and transmitted to the valve shaft 15 of the butterfly valve 12 by the link mechanism 20, so that the valve body 16 is
Close.

At this time, in the butterfly valve 12, since the pressure of the exhaust gas 6 applied to the valve body 16 is equal to the upper and lower pressure with respect to the valve shaft 15, the rotational torque of the valve shaft 15 due to the pressure of the exhaust gas 6 is canceled. , The return spring 46 is the valve body 1
6 can be closed with small resilience. In the event of an electrical failure related to motor drive, this action allows valve body 16 to automatically return to the closed state. That is, a so-called fail-safe function of the EGR valve 10 is constructed by the action of the return spring 46. Without this fail-safe function, EGR
If an electrical failure occurs while the valve 10 is open, black smoke is emitted depending on operating conditions (acceleration, etc.).
In addition, the rod 43 is normally operated by the drive circuit.
Moves in the direction of the motor 30 because the spring force of the return spring 46 facilitates the movement, for example, the time from full opening to full closing of the valve element 16 of the butterfly valve 12 is extremely short, about 0.1 second. . In the EGR valve 10, when the time from the full opening to the full closing is short, it is possible to prevent the black smoke from being discharged from the exhaust passage 3 of the diesel engine 1.

Here, the opening of the butterfly valve 12, that is, the amount of rotation of the valve body 16 is determined by the amount of advance of the rod 43, that is, the amount of rotation of the motor 30, so that the opening of the EGR valve 10 according to this embodiment is It can be controlled steplessly.

That is, when the controller 5 obtains the opening of the EGR valve 10 according to the operating conditions (output, rotation speed) of the diesel engine 1, the controller 5 calculates the rotation amount of the motor 30 corresponding to the opening and calculates the target value. Motor drive circuit 3
Command 1 The motor drive circuit 31 rotates the rotary shaft 33 of the motor 30 by the target value in response to the command, and moves the rod 43 by the feed screw shaft 48 by an amount corresponding to the target opening. The movement of the rod 43 is transmitted to the valve body 16 via the link mechanism 20, so that the valve body 1
6 opens the valve passage 13 by the target opening degree.

At this time, the rotation amount of the rotating shaft 33 of the motor 30 is detected by the Hall IC 39 and transmitted to the controller 5 every moment, so that the rotation amount (target value) of the motor 30 is feedback-controlled. . Rotary axis 3
When the supply of electric power to the motor drive circuit 31 is stopped when the rotation amount of the motor 3 reaches the target value, the feed screw shaft 48, that is, the rotation shaft 33 is reversely rotated by the elastic force of the return spring 46. The reverse rotation of the rotating shaft 33 is performed by the Hall IC 3
9 and is transmitted to the controller 5 at the same time, the controller 5 energizes the motor drive circuit 31 to cause the rotating shaft 33 to maintain the rotation amount of the target value. Incidentally, the reverse rotation of the rotating shaft 33 can be detected by comparing the output signals of the pair of Hall ICs 39, 39.

As described above, E according to this embodiment is
In the GR valve, the controller 5 obtains an opening in accordance with the operating conditions (output, rotation speed) of the diesel engine 1, calculates the amount of rotation of the motor 30 corresponding to the opening, and sets the motor drive as a target value. By instructing the circuit 31, the opening of the EGR valve 10 can be controlled steplessly.

According to the above embodiment, the following effects can be obtained.

1) Even for a diesel engine having a large pressure fluctuation such as a diesel engine equipped with a supercharger (turbocharger), the exhaust gas having a recirculation flow rate corresponding to the operating conditions is supplied with no EGR valve opening. By controlling in stages, it is possible to control with high accuracy.

2) Since the EGR valve closes in an extremely short time, it is possible to prevent the black smoke from being discharged from the exhaust passage of the diesel engine when the EGR valve closes.

3) If the drive current stops flowing to the motor due to an electrical failure, the valve automatically closes, thereby preventing black smoke from being discharged.

4) According to the above 1), 2) and 3), it is possible to realize a clean exhaust gas emission in a diesel engine, which can contribute to environmental conservation.

5) Since the stopper for restricting the rotation of the lever is provided, wear of the butterfly valve can be prevented.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

For example, in the above embodiment, the case where the present invention is applied to a diesel engine has been described.
The present invention can be applied to a gasoline engine. Also, not only the feed screw shaft of the feed screw mechanism is arranged on the motor side and the female screw member is arranged on the link mechanism side,
The feed screw shaft may be arranged on the link mechanism side, and the female screw member may be arranged on the motor side.

It is desirable that the link mechanism is not limited to the structure according to the above-described embodiment, but is appropriately configured corresponding to the mounting position of the EGR valve with respect to the exhaust gas recirculation passage.

The means for detecting the rotation angle is not limited to a combination of the disc magnet and the Hall IC, but may be a Hall element or an optical sensor.

[0042]

As described above, according to the present invention,
By combining the motor and the butterfly valve, the recirculation flow rate of the exhaust gas can be controlled steplessly.

[Brief description of the drawings]

FIG. 1 is a partially omitted front sectional view showing a state in which an EGR valve according to an embodiment of the present invention is closed.

FIG. 2 is a partially cutaway front view showing a state where an EGR valve is opened.

FIG. 3 is a schematic diagram showing a system for arranging and controlling an EGR valve in an intake and exhaust system of an engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Intake passage, 3 ... Exhaust passage, 4 ... Exhaust gas recirculation passage, 5 ... Controller, 6 ...
Exhaust gas, 10: EGR valve, 11: Bracket, 1
2 ... butterfly valve, 13 ... valve passage, 14 ... valve box, 15 ...
Valve shaft, 16: valve element, 20: link mechanism, 21: lever,
22 link bar, 23, 24 pin, 25 stopper, 25a bolt, 25b nut, 30 motor
30a: motor cover, 31: motor drive circuit, 32:
Front cover, 32a: Inlay member, 32b: Screw, 33: Rotating shaft, 34: Coupling, 35: Detent pin, 37: Disk magnet, 38: Printed wiring board, 39: Hall IC, 40: Feed screw mechanism, 41
... Yoke, 42 ... Bushing, 43 ... Rod, 43a ... Mounting hole, 45 ... Spring seat, 46 ... Return spring, 47 ... Female screw member, 47A ... Female screw member holder,
48: feed screw shaft, 49: dustproof cover, 50: O-ring, 51: seal.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuya Yamada 3-20-30 Shinnakazato, Yono-shi, Saitama Miwa Seiki Co., Ltd. F-term (reference) 3G062 EA11 GA21 3H063 AA02 BB24 BB32 BB37 BB43 DA14 DB04 DB06 DB46 DC01 EE08 FF01 GG03 GG19

Claims (3)

[Claims] 1. A butterfly valve interposed in an exhaust gas recirculation passage for adjusting a flow rate of exhaust gas, an electric motor for driving the butterfly valve to open and close, and a rotation of a rotary shaft of the electric motor in a linear motion. An exhaust gas recirculation valve comprising: a feed screw mechanism for converting the feed screw mechanism; a link mechanism for transmitting a linear motion of the feed screw mechanism to the butterfly valve; and a rotation angle detecting means for detecting a rotation angle of the electric motor. 2. The exhaust gas recirculation valve according to claim 1, wherein the feed screw mechanism is urged by a return spring in a direction in which the butterfly bubble closes. 3. A link mechanism for transmitting the linear movement of the feed screw mechanism to the butterfly valve includes a lever and a link bar connected to the lever, and the link mechanism is configured to rotate the lever. The exhaust gas recirculation valve according to claim 1 or 2, further comprising a stopper with which the lever abuts at a position where the butterfly valve that opens and closes due to movement is closed.