JPH0311401Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an exhaust gas recirculation device for an engine.

EGR (exhaust gas recirculation) is a technology that recirculates a portion of exhaust gas into the combustion chamber of an engine.
Commonly used in gasoline engines for reduction purposes. On the other hand, NOx countermeasures for diesel engines often involve delaying the fuel injection timing and increasing the fuel injection rate.
EGR is also being implemented in some areas.

The main purpose of this invention is to improve combustion conditions by recirculating a portion of the exhaust gas into the combustion chamber by using a normally closed valve for engine braking, which is provided separately from the intake and exhaust valves. .

A normally closed valve for engine braking is described, for example, in Japanese Patent Application Laid-Open No. 126640/1983, and is called the third valve because it is the third valve that is separate from the intake valve and exhaust valve provided in the cylinder head. Sometimes. Also in this specification, this normally closed valve will hereinafter be referred to as the third valve.

FIG. 1 shows an example of valve timing when such a third valve is used for engine braking, together with those of an exhaust valve and an intake valve. In this example, the third valve opens from slightly before compression top dead center to slightly after the exhaust valve opens to absorb a portion of the compression work. At this time, fuel injection into the combustion chamber is stopped.

This idea controls the opening timing of the third valve,
As shown in FIG. 2, the combustion chamber is characterized by changing the timing when the exhaust valve is slightly opened to recirculate a portion of the exhaust gas into the combustion chamber.

An embodiment of this invention will be described below with reference to FIG. In the combustion chamber 2 of the engine 1, the ends of an intake passage 3, an exhaust passage 4, and a third valve passage 5 communicating with the exhaust passage 4 are open, and each of these openings is connected to an intake valve 6. , the exhaust valve 7 and the third valve 8 are normally closed. The opening and closing of the intake valve 6 and the exhaust valve 7 are controlled via a rocker arm, a push rod, a tappet, and a cam on a camshaft (not shown), respectively. The third valve 8 is connected to a camshaft 10 of the fuel injection pump 9.
cam 11 (actually this camshaft 10
The cam 11 is provided facing in the left-right direction in the figure. ) A plunger 14 driven by the cam 11 to force-feed the oil in the oil tank 12 through the pipe 13, and a piston 1 to drive the third valve 8 with the pumped oil.
Opening/closing is controlled by 5 etc.

This third valve 8 is controlled to open and close at the timing shown in FIG. 1 during engine braking, but is controlled to open and close at the timing shown in FIG. 2 during EGR. For this reason, the cam 11 that drives the third valve 8 consists of two cams of the same shape with different phases, and normally a switching mechanism is activated by a signal from the control section 16 to switch the cam for EGR. 11 is selected and the engine brake switch 17 is turned on, the engine brake cam 11 is selected by a signal from the control section 16.

Furthermore, the switching mechanism uses a hydraulic timer similar to the hydraulic timer 18 provided in the fuel injection pump 9 to adjust the advance angle of the camshaft 10 for the third valve 8 as shown in FIGS. The valve timing shown in FIG. 2 may be obtained.

This idea is not limited to EGR for reducing Nox.
It can also be used to promote warming up. That is, when the third valve 8 is opened at the same timing as EGR when starting the engine to recirculate part of the exhaust gas into the combustion chamber, the combustion gas temperature becomes higher and the engine speed rises faster.

As described above, the exhaust gas recirculation device according to this invention has a simple configuration because it uses the third valve for engine braking, and can be used for purposes other than engine braking, such as reducing Nox and promoting warm-up. be able to.

In addition, the camshaft of the fuel injection pump is used to obtain the hydraulic pressure for opening the normally closed valve, and the cam phase is switched. Compared to a device in which a drive mechanism and a phase switching mechanism are provided within the engine body, the entire device is simpler and easier to install. Furthermore, since the normally-closed valve is configured to open from immediately after the exhaust valve opens to immediately after the intake valve opens for the next stroke, the normally-closed valve remains open for most of the period when the exhaust valve is open. , the exhaust opening area is substantially expanded and the exhaust efficiency is improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing an example of the valve timing of the conventional third valve for engine braking, FIG. 2 is a graph showing an example of the valve timing of the third valve in an embodiment of this invention, and FIG. FIG. 1 is a schematic configuration diagram of an exhaust gas recirculation device showing an embodiment of this invention. 1...Engine, 2...Combustion chamber, 3...Intake passage, 4...Exhaust passage, 5...Third valve passage, 6...
Intake valve, 7...Exhaust valve, 8...Third valve, 9...Fuel injection pump, 10...Camshaft, 11...Cam,
12...Oil tank, 13...Pipe, 14...
...Plunger, 15...Piston, 17...Engine brake switch, 18...Hydraulic timer.

Claims (1)

[Scope of utility model registration request] Separately from the intake valve and the exhaust valve, a normally closed valve for engine braking is opened near the top dead center of the compression stroke of the engine to allow compressed air in the combustion chamber to flow out through an exhaust passage opened and closed by the exhaust valve. A cam provided on the camshaft of the fuel injection pump of the engine, a plunger that is driven in contact with the cam and pumps the hydraulic oil, and a plunger provided on the head of the normally closed valve that pumps the hydraulic oil. Therefore, there is a drive piston that opens the normally closed valve, a switching mechanism provided on the camshaft that switches the phase of the cam between the engine brake and exhaust gas recirculation, and one of the cams, depending on the operating conditions. and a control section that selects a phase and outputs a switching signal to the switching mechanism, and when the phase for exhaust gas recirculation is selected by the control section, the normally closed valve is switched to the next phase immediately after the exhaust valve is opened. An exhaust gas recirculation device characterized in that the exhaust gas recirculation device is configured to be open until immediately after the intake valve opens during a stroke so that a part of the exhaust gas is recirculated to the combustion chamber through the normally closed valve.