Dual-peak exhaust camshaft

Abstract

The invention discloses a camshaft with a dual-peak exhaust cam, which is used for recycling the internal waste gas. The camshaft comprises an intake cam and two exhaust cams; and the two exhaust cams include an exhaust cam and an EGR cam. The exhaust cam and the EGR cam share the same base circle; the maximum lift of the intake and exhaust cams is 5.5 to 9.5 mm; and the maximum lift h of the EGR cam is 0.5 to 2.5 mm. The included angle between the centre lines of the intake cam and the exhaust cams is 90 to 140 degrees; and the included angle alpha between the two centre lines of the exhaust cam and the EGR cam is 90 to 150 degrees. The included angle beta between the two end points of the exhaust cam travel and the EGR cam travel is 0 to 50 degrees. When the suction of a piston approaches the lower stop point of intake, the EGR cam makes an exhaust valve re-opened so that partial waste gas is sucked back to the cylinder by using the vacuum degree in the cylinder and the recycling of the waste gas is realized. The invention can effectively reduce NOx emission and avoid valve abrasion.

Description

technical field [0001] The invention belongs to components of an internal combustion engine, in particular to a camshaft with a double-peak exhaust cam, which is used for internal exhaust gas recirculation and reduces the NOx emission of the internal combustion engine. Background technique [0002] At present, for diesel engines meeting Euro III emission regulations, exhaust gas recirculation is usually used to reduce NOx emissions. Exhaust Gas Recirculation (EGR for short) is one of the effective measures to reduce NOx emissions from internal combustion engines. At present, there are two ways of exhaust gas recirculation: external and internal. External EGR is to introduce part of the exhaust gas from the exhaust pipe into the intake pipe, and achieve the purpose of reducing NOx by changing the composition of the intake gas. External EGR requires external exhaust gas recirculation piping and control valves. Internal EGR uses the change of the timing of the intake and exh...

AI Technical Summary

Problems solved by technology

However, this internal EGR method has a limited effect on reducing NOx emissions, especially for diesel engines with low speed

There is also an internal EGR method. When the intake valve is opened for the second time in the exhaust stroke, the exhaust gas in the cylinder is sucked into the intake pipe and then enters the cylinder with the intake valve. Although this method can significantly reduce NOx emissions, it will reduce the power consumption. The reduction is very large, and it will accelerate the wear of the intake valve and affect the service life of the intake valve

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