JP3156470B2 - Internal combustion engine with exhaust brake - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having an exhaust brake, and more particularly, to an internal combustion engine having an exhaust brake device and an EGR device (exhaust gas recirculation device). The present invention relates to an internal combustion engine with an exhaust brake that does not return to the intake side.

[0002]

2. Description of the Related Art Conventionally, there has been known an EGR device in which exhaust gas is recirculated into an intake passage through an exhaust gas recirculation (hereinafter referred to as EGR) passage in order to reduce NOx in the exhaust gas. In such an EGR device, a normal EGR
An EGR control valve is provided in the passage, and the amount of EGR gas to be supplied into the intake passage is controlled by the EGR control valve.

On the other hand, in a large vehicle or the like, the exhaust gas is confined in the exhaust pipe by closing a shut-off valve arranged in the middle of the exhaust pipe, the back pressure is increased, and the pumping friction is increased to brake the vehicle. An exhaust brake device is applied. In such an exhaust brake device, when the back pressure exceeds a predetermined pressure during the operation of the exhaust brake, the exhaust valve of the cylinder during the intake stroke is forcibly pushed down by the back pressure, and the exhaust gas is released by opening the valve, The pressure is adjusted.

In an internal combustion engine provided with an exhaust brake device, which is provided with an EGR device as a measure for exhaust emission (Nox), the back pressure when the exhaust brake device operates is reduced. The rise causes the EGR control valve to be pushed open, and the exhaust gas escapes to the intake system through the EGR device. Therefore, there has been a problem that the back pressure decreases and the effectiveness of the exhaust brake deteriorates.

Therefore, a device proposed in Japanese Utility Model Laid-Open Publication No. 63-79463 has an EGR diaphragm valve provided on one side of an EGR passage provided in an EGR passage connecting an exhaust passage and an intake passage upstream of an exhaust brake valve. An EGR control valve is closed by providing an opening pressure chamber containing a spring for setting the valve pressure, and providing a closing pressure chamber on the other side, and introducing a negative pressure into the closing pressure chamber when the exhaust brake is operated. It has been proposed to increase the force.

In the device proposed in Japanese Utility Model Laid-Open Publication No. 63-79463, the closing pressure chamber of the EGR control valve is opened to the atmosphere when the exhaust brake valve is not operated, and the spring contained in the opening pressure chamber is opened. The EGR control valve is opened by introducing a negative pressure exceeding the valve opening pressure to the opening pressure chamber. Further, when the exhaust brake is activated, a negative pressure is introduced into the closing pressure chamber of the EGR control valve, so that the valve opening pressure of the EGR control valve is reduced to the atmospheric pressure by the valve opening pressure of the spring provided in the opening pressure chamber. And a pressure difference from the negative pressure is applied, which is larger than usual. Therefore, even when a back pressure from the exhaust gas passage is applied to the valve body of the EGR control valve during operation of the exhaust brake, the EGR control valve does not open.

[0007]

However, in the device proposed in Japanese Utility Model Laid-Open Publication No. 63-79463, a strong negative pressure source for guiding the closing pressure chamber of the EGR control valve is required, and this negative pressure is required. A negative pressure switching valve (VSV) that guides the negative pressure from the source to the opening pressure chamber when the EGR device is operating when the exhaust brake is not operating and to the closing pressure chamber when the exhaust brake is operating requires a device. Cost was up.

Accordingly, the present invention operates an exhaust brake in an internal combustion engine having an exhaust brake device and an EGR device for returning a part of exhaust gas from an exhaust pipe upstream of the exhaust brake device to an intake pipe side. Sometimes, the EG of the EGR device
An object of the present invention is to provide an internal combustion engine with an exhaust brake having a simple structure capable of securing an exhaust braking force without an R control valve being opened before an exhaust valve.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an exhaust brake device for temporarily blocking the flow of exhaust gas flowing in an exhaust pipe, and an exhaust gas from an exhaust pipe upstream of the exhaust brake device. EGR that returns part of the air to the intake pipe side
The internal combustion engine provided with the device, the opening set force of the exhaust valve for scavenging the combustion gas in the combustion chamber of the internal combustion engine, the exhaust gas
When the control valve is closed, the valve opening force of the EGR control valve of the EGR device is set lower than the opening force .

[0010]

According to the internal combustion engine with an exhaust brake of the present invention, the set pressure for opening the exhaust valve is a value at which the exhaust braking force can be ensured and is lower than the set pressure for opening the EGR control valve of the EGR device. When the back pressure on the upstream side of the exhaust brake valve increases during the operation of the exhaust brake, EG
The exhaust valve of the cylinder in the intake stroke opens before the R control valve. As a result, during the operation of the exhaust brake, the EGR control valve does not open and the exhaust gas does not leak to the intake pipe side.
The operating force of the exhaust brake can be secured.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1A is an overall configuration diagram showing a configuration of an internal combustion engine with an exhaust brake according to the present invention. In FIG. 1 (a),
1 is a four-cylinder internal combustion engine, 2 is an intake manifold, 3 is an exhaust manifold, 4 is an exhaust pipe, 5 is an exhaust brake device provided with an exhaust control valve 51 provided in the middle of the exhaust pipe 4, 6 is a muffler, 7 is An exhaust gas recirculation pipe (EGR pipe) for guiding exhaust gas from the exhaust manifold 3 to the intake manifold 2; 8, an EGR control valve; 9, a vacuum pump; 10, a control circuit;
Reference numeral 2 denotes a control valve provided in the middle of the negative pressure introducing pipe 13 and controlled to be opened and closed by the control circuit 10.

The EGR control valve 8 is opened when the control valve 12 is opened in response to a signal from the control circuit 10 and the negative pressure from the vacuum pump 9 is led through the negative pressure introducing pipe 13, and the EGR control valve 8 is opened from the exhaust manifold 3. The exhaust gas is returned to the intake manifold 2 through 7 to reduce NOx in the exhaust gas. The exhaust brake device 5 is activated when the control circuit 10 detects a deceleration state of the vehicle, and the exhaust control valve 51 is closed to confine exhaust gas in the exhaust pipe 4 and the EGR pipe 7 to increase the back pressure, thereby increasing the piston pressure. Acts as a brake by increasing pumping friction. The control circuit 10 opens the control valve 11 when detecting the deceleration state of the vehicle, and guides the negative pressure from the vacuum pump 9 to the exhaust brake device 5 to close the exhaust control valve 51.

Exhaust brake device 5 operating as described above
When the exhaust control valve 51 closes the exhaust pipe 4 and the back pressure in the exhaust pipe 4 and the EGR pipe 7 continues to increase, the exhaust valve (not shown) of the cylinder in the intake stroke of the internal combustion engine 1 and the EGR The control valve 8 is opened by the back pressure. Fig. 1 (b) is the same as Fig. 1 (a)
FIG. 8 is a characteristic diagram showing a comparison between the magnitude of the opening setting force of the EGR control valve 8 and the magnitude of the opening setting force of the exhaust valve in the embodiment shown in FIG. In this embodiment, the back pressure of the exhaust valve
Opening setting force, exhaust brake force Yes to be larger than the back pressure limit value can be secured open by the back pressure of the EGR control valve 8
The valve setting force is set larger than the valve opening setting force of the exhaust valve.

FIG. 2 shows E of the internal combustion engine with an exhaust brake shown in FIG.
GR control valve 8 and exhaust valve 30 provided in internal combustion engine 1
FIG. 2 is a configuration explanatory diagram including a cross-sectional view showing details of the configuration of FIG. In FIG. 2, 14 is an intake pipe connected to the intake manifold 2, 15 is an intake control valve provided in the intake pipe 14, 16
Is an intake port, 17 is a combustion chamber, 18 is a piston, 19 is an exhaust port, 20 is an intake valve, and 30 is an exhaust valve.

The exhaust valve 30 includes a valve element 31 for opening and closing the exhaust port 19, a spring 32 for urging the valve element 31 to close the exhaust port 19, and opening the valve element 31 against the spring 32. An exhaust cam 33 is provided.
The EGR control valve 8 is divided into a valve section 8A and a valve drive section 8B, and an EGR pipe 7 is provided in a housing 80 of the valve section 8A.
And a valve shaft 82 attached to the valve body 81. The valve driving section 8B has a housing 88 partitioned by a diaphragm 83 into an atmospheric pressure chamber 88A and a negative pressure chamber 88B. A spring 84 is provided in the negative pressure chamber 88B. The end of the valve shaft 82 is connected to the diaphragm 83 on the side of the atmospheric pressure chamber 88A, and the spring 84 urges the diaphragm 83 in the direction in which the valve body 81 closes the EGR pipe 7.

When the control valve 12 shown in FIG. 1 is opened and a negative pressure from the vacuum pump 9 is introduced into the negative pressure chamber 88B through the negative pressure introducing pipe 13, the diaphragm 83 is attached with a spring 84. Negative pressure chamber 88B against power
Side, the valve body 81 opens and the exhaust gas becomes EG.
The air is returned to the intake manifold 2 through the R pipe 7. In addition,
When the exhaust control valve 51 of the exhaust brake device 5 is closed, the back pressure in the exhaust pipe 4 and the EGR pipe 7 rises while pulsating as shown by a solid line B in FIG. This pulsation occurs because the exhaust gas confined in the exhaust pipe 4 flows back into the cylinder when the valve element 31 of the exhaust valve 30 opens in the exhaust stroke, the pressure drops, and the exhaust stroke then proceeds. This is because when the piston 18 rises, it is compressed and the pressure rises.

The reason why the overall pressure rise stops with the passage of time is that the back pressure is reduced by the spring 32 of the exhaust valve 30.
When the set valve opening force is reached , the exhaust valve 3 in the cylinder in the intake stroke
This is because the zero valve element 31 is pushed down by the back pressure, and the exhaust gas escapes to the combustion chamber 17 during the intake stroke. When the spring 32 is strengthened in this state to increase the valve opening setting force of the exhaust valve 30, the pressure at which the back pressure stabilizes increases as shown by the solid line A in FIG. The spring 32 of the exhaust valve 30
Is further increased, the back pressure rises high as shown by the dashed line C.

On the other hand, the spring 84 of the EGR control valve 8
When the set valve opening force is lower than the set valve opening force of the spring 32 of the exhaust valve 30, when the exhaust control valve 51 closes the exhaust pipe 4 and the back pressure increases, the EGR control is performed more than the exhaust valve 30. The valve 8 opens first, lowering the back pressure and deteriorating the braking performance of the exhaust brake. Therefore, in this embodiment, as described with reference to FIG. 1 (b), the EGR control valve 8 is controlled with the opening setting force of the exhaust valve 30 set to a value that can ensure the braking performance of the exhaust brake device 5. The valve opening setting force of the spring 84 is
By setting the opening force of the spring 32 of the exhaust valve 30 to be equal to or higher than the set force , the exhaust braking performance of the EGR control valve 8 is prevented from deteriorating.

Hereinafter, the opening of the spring 32 of the exhaust valve 30 will be described.
Valve setting force and opening of spring 84 of EGR control valve 8
The calculation example of the constant force is shown. However, Dex is the valve body 3 of the exhaust valve 30.
1 is the diameter at which the back pressure is applied in the direction of opening the valve, Pex is the back pressure required when the exhaust brake is activated (varies depending on the vehicle), and Degr is
Back pressure is applied in the direction to open the valve body 81 of the GR control valve 8
Diameter .

[0020] The valve opening setting force of the spring 32 of the exhaust valve 30 <br/> and Fex, Fex = [π × (Dex) ² × Pex] opening of the spring 84 of the × 1/4 ... EGR control valve 8 Set the power to Fegr
Then, Fegr ≧ [π × (Degr) ² × Pex] × １ ／ From the above expression and the expression, the following expression is established.

(Fegr / Fex) ≧ (Degr / Dex) ² ... The formula is modified so that Fegr ≧ Fer × (Degr / Dex) ² ... EGR so that the force obtained by the formula can be achieved.
The valve opening setting force Fegr of the spring 84 of the control valve 8 may be determined.

As described above, in the internal combustion engine with an exhaust brake according to the present invention, when the exhaust brake device 5 is operated, the exhaust valve 30 opens before the EGR control valve 8, so that the exhaust braking force is secured. Back pressure can be controlled as much as possible. As described above, in the internal combustion engine with the exhaust brake according to the present invention, by devising the opening setting force of the exhaust valve 30 originally present in the internal combustion engine, a strong drive source for increasing the opening force of the EGR control valve 8 is provided. Also, a negative pressure switching device or the like is not required.

[0023]

As described above, according to the present invention,
In an internal combustion engine including an exhaust brake device and an EGR device that returns a part of exhaust gas from an exhaust pipe on an upstream side of the exhaust brake device to an intake pipe side, a fuel in a combustion chamber of the internal combustion engine is provided.
Set the opening force of the exhaust valve to scavenge the combustion gas, and close the exhaust control valve.
When opening the valve, set the valve lower than the opening force of the EGR control valve of the EGR device.
Therefore, when the exhaust brake is activated, the EGR control valve does not open earlier than the exhaust valve, and there is an effect that the exhaust brake force can be secured.

Further, since a strong driving source and a negative pressure switching means for increasing the closing force of the EGR control valve are not required, there is no increase in cost.

[Brief description of the drawings]

FIG. 1A is an overall configuration diagram showing the configuration of an internal combustion engine with an exhaust brake according to the present invention, and FIG. 1B is a diagram comparing the magnitude of the EGR control valve and the exhaust valve opening setting force of FIG. It is a characteristic diagram.

FIG. 2 is a configuration explanatory view including a cross-sectional view showing details of configurations of an EGR control valve and an exhaust valve of the internal combustion engine with an exhaust brake of FIG. 1;

FIG. 3 is a diagram illustrating a change characteristic of a back pressure at the time of operating an exhaust brake according to a magnitude of an opening setting force of an exhaust brake valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake manifold 3 ... Exhaust manifold 4 ... Exhaust pipe 5 ... Exhaust brake device 7 ... Exhaust recirculation pipe (EGR pipe) 8 ... EGR control valve 9 ... Vacuum pump 10 ... Control circuit 11 ... Control valve 12 ... Control Valve 13 ... Negative pressure introducing pipe 30 ... Exhaust valve 31 ... Valve 32 ... Spring 51 ... Exhaust control valve 81 ... Valve 83 ... Diaphragm 84 ... Spring 88A ... Atmospheric pressure chamber 88B ... Negative pressure chamber

Claims (1)

(57) [Claims] An exhaust brake device for temporarily interrupting the flow of exhaust gas flowing in an exhaust pipe, and an EGR device for returning a part of the exhaust gas from an exhaust pipe upstream of the exhaust brake device to an intake pipe side. An internal combustion engine comprising: an exhaust valve that scavenges combustion gas in a combustion chamber of the internal combustion engine.
When the exhaust set valve is closed, the EGR device E
An internal combustion engine with an exhaust brake, wherein the internal combustion engine is set lower than a valve opening force of a GR control valve.