Patent ID: 8714238

Claim:
A heat exchanger comprising: a case provided with an exhaust inlet at one side and an exhaust outlet at another side, an exhaust gas flowing in through the exhaust inlet and flowing out through the exhaust outlet; a coolant pathway formed in the case and fluidly communicating with a coolant inlet and a coolant outlet so as to pass coolant therethrough; an exhaust pathway having a tubular shape, disposed close to the coolant pathway within the case, and provided with one end connected to the exhaust inlet and the other end connected to the exhaust outlet so as to pass the exhaust gas, wherein the exhaust gas passing through the exhaust pathway exchanges heat with the coolant passing through the coolant pathway; a bypass pathway having a tubular shape, disposed at a middle portion of the exhaust pathway along a length direction thereof, provided with one end selectively connected to the exhaust inlet and the other end always connected to the exhaust outlet, wherein the exhaust gas passing through the bypass pathway exchanges heat with the coolant passing through the coolant pathway; and a connecting pipe radially extending from an exterior circumference of the bypass pathway to the exhaust pathway so as to send a portion of the exhaust gas passing through the bypass pathway to the exhaust pathway; and a valve mounted at a front end portion of the bypass pathway and selectively connecting the exhaust inlet to the bypass pathway through the connecting pipe; wherein the exhaust gas enters the bypass pathway and flows into the exhaust pathway through the connecting pipe so as to reduce noise of the exhaust gas when the valve is open, and the exhaust gas enters the exhaust pathway directly when the valve is closed; and wherein the valve is closed so as for the exhaust gas to pass through the exhaust pathway when speed of the exhaust gas is lower than a predetermined speed, and the valve is open such that the exhaust gas passes through the bypass pathway and a portion of the exhaust gas is flowed into the exhaust pathway through the connecting pipe when the speed of the exhaust gas is higher than the predetermined speed.