EXHAUST ENGINE RECIRCULATION DEVICE

Abstract

Exhaust gas recirculation device (10) for recirculating a portion of the exhaust gas from an engine (1) to an intake side of the engine (1) through an EGR channel (Ag), wherein the exhaust gas recirculation device (10) comprises: a reed valve (13) provided at a connection position between the EGR channel (Ag) and an intake channel (En) of the engine (1); an EGR valve (12) provided on the EGR channel (Ag); and an EGR pipe (14) forming a channel connecting the EGR valve (12) and an EGR cooler (11), wherein the EGR pipe (14) is part of the EGR channel (Eg), wherein the EGR pipe (14) has natural frequency characteristics of 200 Hz or less and suppresses a resonance of an opening / closing noise generated by the reed valve (13), wherein the resonance is located within the EGR channel (Eg).

Description

Technical field The present disclosure relates to an exhaust gas recirculation device with a tongue valve. Technical background To reduce NOx in the exhaust gas of an engine, an exhaust gas recirculation device (hereinafter also referred to as "EGR") is often used, which returns the exhaust gas to the engine. The EGR device can regulate the mass flow rate of the recirculating EGR gas by controlling an EGR valve located in an EGR channel. In some engine specifications, the differential pressure between the inlet and outlet of the EGR valve is low and can become negative depending on driving conditions. In such an engine, a reed valve (check valve) is provided at a junction between the EGR channel and an engine intake port to prevent the backflow of EGR gas, while simultaneously pumping out the EGR gas by utilizing a periodic differential pressure change caused by pulsing the cylinder's intake / exhaust stroke. A one-way reed valve is most commonly used as such a reed valve (see PTLs 1 and 2). References patent specifications PTL1: Japanese patent application publication JP 2000 249 004 APTL2: Japanese patent application publication JP 2001 132 557 A From DE 10 2010 033 553 A1, an exhaust gas recirculation device for recirculating a portion of the exhaust gas from an engine to an intake side of the engine through an EGR channel is known, wherein the exhaust gas recirculation device comprises: a reed valve provided at a connection position between the EGR channel and an intake channel of the engine; an EGR valve provided on the EGR channel; and an EGR pipe forming a channel connecting the EGR valve and an EGR cooler, wherein the EGR pipe is part of the EGR channel, and wherein the EGR pipe is shaped such that resonance is suppressed, with the resonance being located within the EGR channel. From DE 10 2005 020 482 A1, an exhaust gas recirculation device is known in which tongue valves generate opening / closing noises. From DE 10 2009 034 377 A1, an exhaust gas recirculation device is known in which at least one of the pipes is designed as a cast part. From JP 2009 228 645 A it is known that one of the pipes used has an outer surface with a fastening section for attaching the pipe to an outside. Brief description of the invention Technical problem In an EGR device using the reed valve described above, the opening / closing noise of the reed valve resonates in the EGR channel in such a way that an unusual noise (such as a shuffling sound) can be generated. If this noise is audible from the outside, product quality may deteriorate. It is an objective of the present disclosure to provide an exhaust gas recirculation device capable of suppressing an unusual noise caused by a reed valve. Solution to the problem One aspect of the present disclosure is an exhaust gas recirculation device for recirculating a portion of the exhaust gas from an engine to an intake side of the engine through an EGR channel, and the exhaust gas recirculation device comprises: a reed valve provided at a connection position between the EGR channel and an intake port of the engine; an EGR valve provided on the EGR channel; and an EGR pipe forming a channel connecting the EGR valve and an EGR cooler, wherein the EGR pipe is part of the EGR channel, the EGR pipe being formed such that it suppresses a resonance of an opening / closing noise generated by the reed valve, the resonance being located within the EGR channel. Advantageous effects of the invention The present disclosure can suppress an unusual noise caused by a reed valve, since the EGR pipe is designed in such a way as to suppress a resonance within an EGR channel of an opening / closing sound generated by the reed valve. Brief description of the drawings Fig. 1 schematically shows the overall configuration of an embodiment; Fig. 2 is a perspective view illustrating a state of an EGR pipe, an EGR valve, and an inlet pipe according to the embodiment; Fig. 3 is a perspective view illustrating a state of an EGR pipe, an EGR valve, and a conventional inlet pipe; Fig. 4 shows frequency characteristics observed on the inlet side of the EGR valve (i.e., on the EGR pipe side); and Fig. 5 is a perspective view illustrating a state in which the EGR pipe is mounted according to the embodiment. Description of embodiments In the following, an embodiment of the present disclosure is described with reference to the drawings. Although an inline four-cylinder diesel engine is described as an example of the embodiment, the present invention is not limited to a diesel engine but can also be applied to a gasoline engine. Furthermore, the number of cylinders in the engine and the arrangement of the cylinders are not limited. In the drawings, the dimensions have been adapted to make the configurations easily understandable, and the ratio of the plate thickness, width, length, or the like of each element or part does not necessarily correspond to that of the element or part actually manufactured. As illustrated in Fig. 1, the engine (internal combustion engine) 1 is provided with an engine body 2, an exhaust port Ex, an intake port In and an EGR port (exhaust gas recirculation) Eg. The engine 1 is further equipped with an exhaust manifold 3, an intake manifold 4, a turbocharger 5 with variable turbine 5a and a compressor 5b, an air filter 6, an intercooler 7, an intake throttle 8, an intake pipe 8a and an aftertreatment device 9 with DOC (diesel oxidation catalyst) 9a and DPF (particulate filter) 9b as well as an EGR device 10. The EGR device 10 is equipped with an EGR cooler 11, an EGR valve 12, and a reed valve (check valve) 13. The EGR cooler 11 and the EGR valve 12 are connected by the EGR pipe 14. The engine 1 is a so-called high-pressure EGR system, in which EGR gas is recirculated from the exhaust gas flow upstream of the turbocharger 5. Therefore, the differential pressure between the inlet and outlet of the EGR valve 12 is small and, depending on the driving conditions, can even become negative. In the present embodiment, the reed valve 13 is positioned at a connection point between the EGR channel Eg and the intake channel In of the engine 1 to prevent the backflow of the EGR gas, and simultaneously, the EGR gas is pumped into the intake channel In by using a periodic differential pressure change caused by pulsing the intake / exhaust stroke of the cylinder. Fig. 2 is a perspective view illustrating a state of the EGR pipe 14, the EGR valve 12, and the inlet pipe 8a of the embodiment. Fig. 3 is a perspective view illustrating a state of the EGR pipe 14x, the EGR valve 12, and the inlet pipe 8a of the prior art as a comparative example. As can be seen from a comparison between Fig. 2 and Fig. 3, the EGR pipe 14 of the present embodiment has a larger volume than the conventional EGR pipe 14x. With this configuration, the EGR pipe 14 of the present embodiment functions as a silencer, dampening the slurping noise generated when the reed valve 13 opens and closes. In practice, the EGR pipe 14 is designed to suppress the resonance within the EGR channel Eg, which is generated by the opening / closing noise of the reed valve 13. That is, the resonance is suppressed by making the volume of the hollow part of the EGR pipe 14 larger than that of the conventional EGR pipe 14x in the present embodiment. Fig. 4 shows the frequency characteristics of the opening / closing noise of the reed valve 13, which is observed on the inlet side of the EGR valve 12 (i.e., on the side of the EGR pipe 14). Fig. 4 shows that the resonance frequencies of the opening / closing noise generated by the reed valve 13 are in the range of 208 to 256 Hz. In the present embodiment, the shape of the EGR pipe 14, for example, a volume, is determined such that no resonance occurs in the EGR pipe 14 at these resonance frequencies. In the present embodiment, the EGR pipe 14 has a shape such that it does not resonate at a frequency of 200 to 260 Hz. In particular, the natural frequency (i.e., the resonant frequency of the EGR pipe 14) is set to be lower than 200 Hz by increasing the volume of the EGR pipe 14 compared to the conventional pipe. Such a configuration can prevent the opening / closing noise of the reed valve 13 from resonating in the EGR pipe 14. Furthermore, in the present embodiment, the EGR pipe 14 is formed from a single casting. The cast EGR pipe 14 can further suppress the external emission of an unusual noise generated by the opening / closing of the reed valve 13. That is, the external emission of an unusual noise can be suppressed by reducing the volume of the unusual noise itself within the EGR channel Eg, which has a shape that suppresses the resonance of the opening / closing noise generated by the reed valve 13 within the EGR pipe 14, and by forming the EGR pipe 14 from a single casting. The unusual noise audible from the outside can thus be further suppressed. Forming the EGR pipe 14 from a single casting increases its weight, and therefore the mounting section 14a is formed for attaching the EGR pipe 14 to the outside of the EGR pipe 14, as illustrated in Figures 2 and 5 in the present embodiment. The EGR pipe 14 is then attached, for example, to an engine block, which is indicated by a dashed line over the mounting section 14a, as illustrated in Figure 5. As described above, the present embodiment can implement an exhaust gas recirculation device 10 which is capable of suppressing an unusual noise caused by the reed valve 13 by using the shape of the EGR pipe 14 which suppresses the resonance of the opening / closing noise generated by the reed valve 13 within the EGR channel Eg. The embodiment disclosed herein is merely an example of the implementation of the present invention and should not be interpreted as limiting the technical scope of the present invention in any way. In particular, various modifications are possible without deviating from the meaning or main features of the present invention. In the embodiment disclosed here, resonant frequencies generated by the opening / closing of the reed valve 13 exist in the range of 208 to 256 Hz, as shown in Fig. 4. The natural frequency of the EGR pipe 14 (i.e., the resonant frequency of the EGR pipe 14) is set such that it is lower than 200 Hz; however, the natural frequency of the EGR pipe 14 (i.e., the resonant frequency of the EGR pipe 14) can be set in accordance with the resonant frequencies generated by the opening / closing of the reed valve 13. That is, the EGR pipe 14 can be shaped such that it does not resonate (sympathize) with the resonant frequencies generated by the opening / closing of the reed valve 13. This application is entitled to and claims priority from Japanese patent application No. 2017-122360, filed on June 22, 2017, the disclosure of which, including the description, drawings and abstract, is incorporated herein by reference in its entirety. Commercial usability The exhaust gas recirculation device of the present disclosure is suitable as an exhaust gas recirculation device which includes a reed valve. List of reference symbols 1 Engine 2 Engine body 10 EGR device (exhaust gas recirculation) 11 EGR cooler 12 EGR valve 13 Reed valve 14, 14x EGR pipe 14a Mounting section Eg EGR channel (exhaust gas recirculation) Ex exhaust channel In intake channel

Claims

Exhaust gas recirculation device (10) for recirculating a portion of the exhaust gas from an engine (1) to an intake side of the engine (1) through an EGR channel (Ag), wherein the exhaust gas recirculation device (10) comprises: a reed valve (13) provided at a connection position between the EGR channel (Ag) and an intake channel (En) of the engine (1); an EGR valve (12) provided on the EGR channel (Ag); and an EGR pipe (14) forming a channel connecting the EGR valve (12) and an EGR cooler (11), wherein the EGR pipe (14) is part of the EGR channel (Eg), wherein the EGR pipe (14) has natural frequency characteristics of 200 Hz or less and suppresses a resonance of an opening / closing noise generated by the reed valve (13), wherein the resonance is located within the EGR channel (Eg). Exhaust gas recirculation device (10) according to claim 1, wherein the EGR pipe (14) is formed from a single casting. Exhaust gas recirculation device (10) according to claim 2, wherein an outer surface of the EGR pipe (14) is provided with a fastening section (14a) for fastening the EGR pipe (14) to an outer surface.

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