JP3817381B2 - Otto cycle engine exhaust brake system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust brake device for an Otto cycle engine.
[0002]
[Prior art]
Conventionally, a diesel engine is used in a large vehicle such as a truck, and in this type of diesel engine, the exhaust brake valve disposed in the exhaust pipe is closed during the exhaust stroke of the cylinder to compress the exhaust. Some are equipped with exhaust brakes that are designed to gain power.
[0003]
However, in recent years, a gas engine using gas fuel such as natural gas or LPG (liquefied petroleum gas) has been developed, and it is considered that this gas engine will be installed in large vehicles such as trucks instead of conventional diesel engines. Has been.
[0004]
However, in the case of a diesel engine in which fuel is injected into the cylinder separately from the intake air, output control is performed only by adjusting the fuel injection amount, and air is always supplied from the intake pipe into the cylinder. Therefore, the braking force can be easily obtained by simply closing the exhaust brake valve in the exhaust pipe. However, in the case of a gas engine using gas fuel such as natural gas or LPG (liquefied petroleum gas), As in the case of gasoline engines, the throttle valve provided in the intake pipe is adjusted in conjunction with the accelerator, and fuel and intake air are mixed by a gas mixer or carburetor provided in the middle of the intake pipe. If the accelerator is returned during deceleration, such as a long downhill, which will actually actuate the exhaust brake. Valve becomes substantially fully closed and no longer takes place a sufficient amount of intake air, also does not cause an increase of pressure on the upstream side by closing the exhaust brake valve in the exhaust pipe, resulting in that the braking force is hardly obtained.
[0005]
Therefore, when applying an exhaust brake to such a gas engine (an Otto cycle engine including a gasoline engine), a bypass passage that bypasses a fuel introduction part such as a gas mixer or a carburetor and a throttle valve is provided in the intake pipe to reduce the speed. It has been proposed that even if the throttle valve is substantially fully closed in conjunction with the accelerator, the intake amount necessary for obtaining the braking force is secured by guiding the intake air through the bypass flow path.
[0006]
[Problems to be solved by the invention]
However, in the conventional proposal, since the exhaust brake is operated without performing any special confirmation about the blockage of the fuel supply to the fuel introduction part or the securing of the necessary intake air amount, for example, to the fuel introduction part If the fuel cut-off valve that shuts off the fuel supply is not completely closed, the fuel flows into the gas engine as a lean air-fuel mixture due to intake air via the bypass flow path, and remains in an unburned state. When exhausted to the exhaust pipe and the operation of the exhaust brake is released, afterfire occurs in the exhaust pipe, or burns with a catalyst in the middle of the exhaust pipe (three-way catalyst, oxidation catalyst, NOx reduction catalyst, etc.) There is a risk of placing a heavy burden on the catalyst, and when the bypass valve of the bypass channel is not fully opened, it is sufficient because the necessary intake air amount is not secured. There was also a fear that a sufficient braking force could not be obtained.
[0007]
The present invention has been made in view of the above-described circumstances. The exhaust brake is operated safely after confirming that the fuel supply to the fuel introduction section is shut off and that the necessary intake air amount is ensured. The purpose is to make it function.
[0008]
[Means for Solving the Problems]
In the present invention, a bypass flow path that bypasses the fuel introduction part and the throttle valve is provided in the intake pipe, and a bypass valve that is normally closed and can be opened only during deceleration is provided in the bypass flow path, and the exhaust pipe is always open. In an exhaust brake device of an Otto cycle engine provided with an exhaust brake valve that can be closed only when decelerating at the time of the fuel cut, fuel cutoff confirmation means that can detect that the fuel supply to the fuel introduction part is shut off , and obtain braking force An intake air amount confirming means capable of detecting that a sufficient intake air amount is secured, and confirming that the fuel supply is shut off by the fuel shutoff confirming means, then opening the bypass valve and also characterized in that the exhaust brake valve after confirming the securing of the required intake air amount by the intake air amount confirmation means after the opening operation is configured to be capable of closing operation It is.
[0009]
In this way, when the exhaust brake is operated, the bypass valve is opened after the fuel cutoff check is confirmed by the fuel cutoff check means, so that the fuel is guided downstream in an unburned state. Will not happen.
[0011]
In addition, since the exhaust brake valve is closed after the intake air amount confirmation means confirms that the required intake air amount has been confirmed after the bypass valve is opened, the required intake air amount is reliably ensured.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
1 and 2 show an example of an embodiment of the present invention. In FIG. 1, reference numeral 1 in FIG. 1 denotes a gas engine (Otto cycle engine) using gas fuel such as natural gas or LPG (liquefied petroleum gas), 2 Is an intake pipe for introducing the intake air 4 to each cylinder of the gas engine 1 via the intake manifold 3, and 5 is an exhaust pipe for discharging the exhaust 7 from each cylinder of the gas engine 1 via the exhaust manifold 6. A throttle valve 8 is provided in the intake pipe 2, and an exhaust brake valve 9 is provided in the exhaust pipe 5.
[0014]
As is well known in conventional gasoline engines, the throttle valve 8 is connected to the accelerator pedal via a wire and a link mechanism (not shown) so as to be basically opened and closed in conjunction with the depression and depression of the accelerator pedal. As the accelerator pedal is depressed deeper, the throttle valve 8 opens, the intake air amount increases, and the amount of gas fuel flowing into the gas mixer 10 (fuel introduction portion) also increases, resulting in an increase in engine output.
[0015]
On the other hand, the intake pipe 2 is provided with a bypass passage 11 that bypasses the gas mixer 10 and the throttle valve 8, and an electromagnetic open / close bypass valve 12 is provided in the bypass passage 11. The opening / closing operation of the bypass valve 12 is controlled by the control device 13 with a command 12a so that the valve 12 is normally closed and can be opened only during deceleration.
[0016]
An electromagnetic open / close fuel cut valve 24 is provided in the middle of the fuel supply pipe 23 that guides fuel from the fuel tank 21 to the gas mixer 10 via the pressure reducing valve 22 and the like. Is controlled by the control device 13 in accordance with a command 24a.
[0017]
On the other hand, the exhaust brake valve 9 is opened and closed by an exhaust brake actuator 25, and the operation of the exhaust brake actuator 25 is controlled by a command 25a from the control device 13. .
[0018]
The control device 13 includes an accelerator switch 14, an exhaust brake switch 15, a clutch switch 16, an engine speed detector 17, a vehicle speed detector 18, a neutral switch 19, and signals 14a, 15a from a throttle valve opening detector 20, Reference numerals 16a, 17a, 18a, 19a, and 20a are input to determine the current driving state of the vehicle.
[0019]
Here, the accelerator switch 14 is a switch that is turned on when the accelerator pedal is returned (when the throttle valve 8 is fully closed), and the exhaust brake switch 15 is turned on when the driver wants to operate the exhaust brake. The clutch switch 16 is a switch that is turned on when the clutch pedal is returned (when the gas engine 1 is not idling), and the neutral switch 19 is set to a position other than the neutral position. It is a switch that turns on at a certain time.
[0020]
The most characteristic component in the present embodiment is that an O ₂ sensor 26 (fuel cutoff confirmation means) is provided at the outlet of the exhaust manifold 6 and a pressure sensor 27 (intake air) at the inlet of the intake manifold 3. A quantity confirmation means) is provided, and the oxygen concentration in the exhaust 7 at the outlet of the exhaust manifold 6 is measured by the O ₂ sensor 26 to detect that the fuel supply to the gas mixer 10 is shut off. By measuring the pressure of the intake air 4 at the inlet portion of the intake manifold 3 by the pressure sensor 27, it is possible to detect that an intake air amount sufficient to obtain a braking force is secured. It is.
[0021]
The oxygen concentration detected by the O ₂ sensor 26 is input to the control device 13 as a signal 26a, and the intake pressure detected by the pressure sensor 27 is input to the control device 13 as a signal 27a. In the device 13, based on these signals 26a and 27a, the control relating to the operation of the exhaust brake is executed after confirming that the fuel supply is cut off and the necessary intake air amount is secured.
[0022]
In the figure, reference numeral 28 denotes a catalyst provided on the downstream side of the exhaust brake valve 9 in the exhaust pipe 5.
[0023]
Thus, when the driver returns the accelerator pedal to decelerate the vehicle while the exhaust brake switch 15 is on, the accelerator switch 14 is turned on and detected by the throttle valve opening detector 20. The opening degree of the throttle valve 8 is also a predetermined angle (for example, about 5 °) or less, and usually, at the time of such deceleration, the vehicle speed detected by the vehicle speed detector 18 is a predetermined speed (for example, about 10 km / h) or more. The transmission is in a position other than the neutral position, the neutral switch 19 is turned off, and the clutch switch 16 is also turned on when the clutch pedal is not depressed (the non-idling state of the gas engine 1). The engine speed detected by the number detector 17 is also a predetermined speed (for example, 1 Since supposed to be 00rpm about) above, it is determined that the controller 13 is a decelerating condition to operate the exhaust brake.
[0024]
Whether or not all these conditions are satisfied is performed in steps S1 to S7 in FIG. 2 showing the control flow of the control device 13, and only when the determinations in steps S1 to S7 are all YES. In step S8, the fuel cut valve 24 is closed.
[0025]
After the fuel cut valve 24 is closed, it is determined in step S9 whether or not the output of the O ₂ sensor 26 (the voltage of the detection signal inversely proportional to the oxygen concentration) is equal to or less than a predetermined value (about 100 mV). Is YES, it is determined that the oxygen concentration in the exhaust pipe 5 is not lowered in the gas engine 1, and it can be determined that the fuel supply to the gas mixer 10 is reliably shut off, so that the process proceeds to step S10. Then, the bypass valve 12 is opened.
[0026]
Next, in step S11, it is determined whether or not the pressure in the intake manifold 3 detected by the pressure sensor 27 is greater than or equal to a predetermined value (about 60 kpa). If the determination is YES, the bypass valve 12 is reliably Since it can be determined that the intake amount sufficient to open and obtain the braking force is secured, the routine proceeds to step S12, where the exhaust brake valve 9 is closed, whereby the exhaust brake is operated.
[0027]
On the other hand, if any of the determinations in steps S1 to S7, step S9, and step S11 is NO, the process proceeds to step S13 and whether or not the exhaust brake is currently operating (in the case of NO, each condition is met). In other words, the exhaust brake valve 9 is opened in step S14, and the bypass valve 12 is closed in step S15. In step S16, the fuel cut valve 24 is opened, and the exhaust brake is released.
[0028]
If necessary, a time delay until the influence of closing the fuel cut valve 24 is reflected on the outlet of the exhaust manifold 6 on the downstream side is taken into consideration before proceeding from step S8 to step S9. It is possible to take the delay means, and until the process proceeds from step S10 to step S11, the effect of opening the bypass valve 12 is reflected on the inlet of the intake manifold 3. It is possible to take a delay means considering the time delay.
[0029]
Therefore, according to the above embodiment, the exhaust brake is operated after confirming that the fuel supply to the gas mixer 10 is shut off and that the necessary intake air amount is secured, so that the fuel is introduced to the downstream side in an unburned state. Therefore, it is possible to avoid problems such as afterfire and combustion by the catalyst 28 and problems such as insufficient braking force due to insufficient intake air amount, which makes exhaust brakes safe and reliable. Can function.
[0030]
The exhaust brake device for the Otto cycle engine of the present invention is not limited to the above-described embodiment. In the previous embodiment, the gas engine is described as an example. It can be applied to the apparatus in the same manner, and the fuel introduction part is not limited to a gas mixer, and various systems such as a fuel injection valve (injector) and a carburetor can be adopted. Various sensors other than the O ₂ sensor may be employed, and may be, for example, a λ sensor that detects an air-fuel ratio. When the λ sensor is employed, λ (air at the outlet portion of the exhaust manifold 6 may be used. It is only necessary to confirm that the fuel supply is cut off with the excess ratio being about 2 or more as a guideline. It is possible to employ various sensors, other can of course be modified in various ways without departing from the gist of the present invention.
[0031]
【The invention's effect】
According to the exhaust brake device for an Otto cycle engine of the present invention described above, various excellent effects as described below can be obtained.
[0032]
(I) According to the invention described in claim 1 of the present invention, the bypass valve is opened after confirming the shutoff of the fuel supply to the fuel introduction portion, so that the fuel is in an unburned state. It is possible to avoid problems such as being led downstream and causing combustion with afterfire or catalyst.
[0033]
(II) According to the invention described in claim 1 of the present invention, since the exhaust brake valve after confirming the securing of the required intake air amount is to be closing operation, to obtain a sufficient braking force by the intake air amount shortage It is possible to avoid problems such as being impossible.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment for carrying out the present invention.
FIG. 2 is a flowchart showing a control flow of the control device of FIG. 1;
[Explanation of symbols]
1 Gas engine (Otto cycle engine)
2 Intake pipe 5 Exhaust pipe 8 Throttle valve 9 Exhaust brake valve 10 Gas mixer (fuel introduction part)
11 Bypass passage 12 Bypass valve 26 O ₂ sensor (Fuel cutoff confirmation means)
27 Pressure sensor (intake air amount confirmation means)

Claims (1)

A bypass flow path that bypasses the fuel introduction part and the throttle valve is provided in the intake pipe, and a bypass valve that is normally closed and can be opened only during deceleration is provided in the bypass flow path. In an exhaust brake device of an Otto cycle engine provided with an exhaust brake valve that can be closed, a fuel shut-off confirmation means that can detect that the fuel supply to the fuel introduction part is shut off, and a sufficient force to obtain a braking force An intake air amount confirming means capable of detecting that the intake air amount is secured, and confirming that the fuel shutoff is confirmed by the fuel shutoff confirming means, and then opening the bypass valve and after opening the bypass valve Otto Sai, characterized in that the exhaust brake valve after confirming the securing of the required intake air amount by the intake air amount confirmation means is configured so as to close the operation Exhaust brake system of Le engine.

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