Waste Heat Utilization Device for Internal Combustion Engine

Abstract

A waste heat utilization device ( 2 ) for an internal combustion engine ( 6 ) includes a heat medium circuit ( 8 ) through which a heat medium applied with waste heat from at least one of the engine and a heat source of the engine is circulated as the engine is operated, and a Rankine cycle circuit ( 4 ) through which a working fluid is circulated. The Rankine cycle circuit includes a heating unit ( 10, 12 ) for heating the working fluid by causing heat to transfer to the working fluid from at least one of the heat medium and the heat source, an expander ( 14 ) for expanding the working fluid introduced therein from the heating unit to produce driving force, and a condenser ( 16 ) for condensing the working fluid introduced therein from the expander. The working fluid is delivered from the condenser to the heating unit. The flow rate of at least one of the heat medium and the heat source that transfer heat to the working fluid in the heating unit is controlled in accordance with an operating condition of the engine.

1 . A waste heat utilization device for an internal combustion engine, comprising:
 a heat medium circuit through which a heat medium applied with waste heat from at least one of the engine and a heat source of the engine is circulated as the engine is operated; and   a Rankine cycle circuit through which a working fluid is circulated, the Rankine cycle circuit including a heating unit for heating the working fluid by causing heat to transfer to the working fluid from at least one of the heat medium and the heat source, an expander for expanding the working fluid introduced therein from the heating unit to produce driving force, and a condenser for condensing the working fluid introduced therein from the expander, the working fluid being delivered from the condenser to the heating unit,   wherein a flow rate of at least one of the heat medium and the heat source that transfer heat to the working fluid in the heating unit is restricted in accordance with an operating condition of the engine.   
     
     
         2 . The waste heat utilization device according to  claim 1 , wherein:
 the heat medium is cooling water for cooling the engine, the heat medium circuit is a cooling water circuit which includes a radiator for cooling the cooling water and in which the cooling water is circulated successively through the engine, the heating unit and the radiator at a flow rate corresponding to the operating condition of the engine, and   the cooling water circuit further includes a bypass passage bypassing the heating unit, and flow rate proportioning control means for controlling distribution of the cooling water to the bypass passage and the heating unit, to restrict an amount of the cooling water flowing into the heating unit while maintaining circulation of the cooling water through the cooling water circuit.   
     
     
         3 . The waste heat utilization device according to  claim 2 , wherein the flow rate proportioning control means includes a differential pressure sensor for detecting a differential pressure across the heating unit, and a manipulating unit which is driven so as to restrict the flow rate of the cooling water flowing into the heating unit in accordance with the differential pressure detected by the differential pressure sensor. 
     
     
         4 . The waste heat utilization device according to  claim 3 , wherein:
 the heating unit includes an evaporator connected in series with the radiator as viewed in a flowing direction of the cooling water, for heating the working fluid by causing heat to transfer to the working fluid from the cooling water introduced therein via the engine, and   the flow rate proportioning control means further includes a cooling water temperature sensor for detecting temperature of the cooling water circulated through the cooling water circuit, and drives the manipulating unit so as to cause the cooling water delivered from the engine to flow only into the bypass passage when the temperature of the cooling water detected by the cooling water temperature sensor is lower than or equal to a preset temperature.   
     
     
         5 . The waste heat utilization device according to  claim 4 , wherein:
 the heat source is an exhaust gas discharged from the engine through an exhaust pipe,   the heating unit includes an exhaust gas heat exchanger arranged in the exhaust pipe, and   the Rankine cycle circuit further includes a working fluid pump which is driven to circulate the working fluid.   
     
     
         6 . The waste heat utilization device according to  claim 5 , wherein the flow rate proportioning control means further includes a cooling water temperature sensor for detecting temperature of the cooling water circulated through the cooling water circuit, and wherein, when the temperature of the cooling water detected by the cooling water temperature sensor is lower than or equal to a preset temperature, the flow rate proportioning control means stops operation of the working fluid pump and drives the manipulating unit so as to cause the cooling water delivered from the engine to flow into the exhaust gas heat exchanger. 
     
     
         7 . The waste heat utilization device according to  claim 5 , wherein the flow rate proportioning control means further includes a second bypass passage bypassing only the evaporator, and a second manipulating unit arranged in the second bypass passage to restrict the flow rate of the cooling water flowing into the evaporator in accordance with the temperature of the cooling water detected by the cooling water temperature sensor, and wherein, when the temperature of the cooling water detected by the cooling water temperature sensor is lower than or equal to the preset temperature, the flow rate proportioning control means drives the first-mentioned manipulating unit and the second manipulating unit such that the cooling water delivered from the engine is introduced only into the exhaust gas heat exchanger. 
     
     
         8 . The waste heat utilization device according to  claim 3 , wherein the manipulating unit is a linear three-way valve whose operating position is continuously variable in accordance with the differential pressure detected by the differential pressure sensor. 
     
     
         9 . The waste heat utilization device according to  claim 3 , wherein the manipulating unit is a linear pump which is driven in a continuously variable manner in accordance with the differential pressure detected by the differential pressure sensor. 
     
     
         10 . The waste heat utilization device according to  claim 1 , wherein:
 the heat medium is cooling water for cooling the engine, the heat source is an exhaust gas discharged from the engine through an exhaust pipe,   the heating unit includes an exhaust gas heat exchanger arranged in the exhaust pipe for heating, by the exhaust gas, the cooling water delivered from the engine, and an evaporator for heating the working fluid by causing heat to transfer to the working fluid from the cooling water delivered from the exhaust gas heat exchanger,   the heat medium circuit is a cooling water circuit in which the cooling water is circulated successively through the engine, the exhaust gas heat exchanger and the evaporator at a flow rate corresponding to the operating condition of the engine, and   the cooling water circuit includes heat absorption control means for restricting an amount of heat absorption that the cooling water absorbs from the exhaust gas in the exhaust gas heat exchanger, in accordance with the operating condition of the engine.   
     
     
         11 . The waste heat utilization device according to  claim 10 , wherein:
 the heat absorption control means includes a sensing unit for detecting the operating condition of the engine, and a manipulating unit for restricting the amount of heat absorption in accordance with a detection signal from the sensing unit,   the Rankine cycle circuit further includes a working fluid pump which is driven to circulate the working fluid, and   when the operating condition of the engine detected by the sensing unit indicates that the engine needs to be warmed up, the heat absorption control means stops operation of the working fluid pump and also drives the manipulating unit so as to increase the amount of heat absorption.   
     
     
         12 . The waste heat utilization device according to  claim 11 , wherein:
 the cooling water circuit further includes an evaporator bypass passage bypassing the evaporator, and a thermostat arranged at a meeting point where the evaporator bypass passage joins a downstream side of the evaporator and causing the cooling water to pass through the evaporator when temperature of the cooling water at the meeting point is higher than or equal to a preset temperature,   the sensing unit is a cooling water temperature sensor for detecting temperature of the cooling water circulated through the cooling water circuit, and   when the temperature of the cooling water detected by the cooling water temperature sensor is higher than a second preset temperature which is higher than or equal to the preset temperature, the heat absorption control means drives the manipulating unit so as to decrease the amount of heat absorption.   
     
     
         13 . The waste heat utilization device according to  claim 11 , wherein:
 the sensing unit is an exhaust gas temperature sensor for detecting temperature of the exhaust gas, and   when the temperature of the exhaust gas detected by the exhaust gas temperature sensor is higher than a third preset temperature, the heat absorption control means drives the manipulating unit so as to decrease the amount of heat absorption.   
     
     
         14 . The waste heat utilization device according to  claim 11 , wherein:
 the cooling water circuit further includes an exhaust gas heat exchanger bypass passage bypassing the exhaust gas heat exchanger, and   the manipulating unit is a linear three-way valve which is driven in a continuously variable manner in accordance with a signal from the sensing unit, the three-way valve controlling distribution of the cooling water introduced therein via the engine to the exhaust gas heat exchanger bypass passage and the exhaust gas heat exchanger, to restrict an amount of the cooling water flowing into the exhaust gas heat exchanger.   
     
     
         15 . The waste heat utilization device according to  claim 11 , wherein the manipulating unit is a linear damper which is driven in a continuously variable manner in accordance with a signal from the sensing unit, the damper controlling distribution of the exhaust gas to an exchanger-side passage in the exhaust pipe in which the exhaust gas heat exchanger is located and an exchanger-bypassing passage in the exhaust pipe which bypasses the exhaust gas heat exchanger, to restrict an amount of the exhaust gas from which heat is transferred to the cooling water in the exhaust gas heat exchanger.