JP2012159068A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate freeze of working fluid for recovering waste heat, without deteriorating a fuel consumption rate of an internal combustion engine.SOLUTION: When the working fluid may freeze in a steam loop where the working fluid evaporated by waste heat of an exhaust gas exhausted from an engine 10 circulates, an ECU 60 calculates fuel consumption of the engine to be deteriorated while an electric heater 50 disposed on the steam loop is operated and fuel consumption of the engine to be increased by a crank cap 11 being locally warmed-up using the evaporated working fluid. When the fuel consumption to be increased by the local warming up exceeds the fuel consumption to be deteriorated while the electric heater 50 is operated, the ECU operates the electric heater 50.

Description

  The present invention relates to a control device.

  2. Description of the Related Art Conventionally, there is known a waste heat utilization device that collects and uses waste heat energy generated by driving an internal combustion engine via a fluid as a medium. For example, in Patent Document 1, a steam generator is provided on the exhaust passage, steam generated from the steam generator is caused to flow into the heat exchanger, and heat exchange is performed between the engine coolant and the steam in the heat exchanger. Describes a waste heat utilization device that performs early engine warm-up when cold.

  Moreover, there are Patent Documents 2 to 4 as technologies related to engine control when the engine is cold and when the outside air temperature is low.

JP 2010-156315 A JP 2005-108832 A JP 2010-223161 A JP 2006-052718 A

  In the waste heat utilization apparatus described in Patent Document 1, a steam loop is formed in which steam generated in the steam generator flows to the heat exchanger, condenses after heat exchange with the engine cooling water, and circulates to the steam generator. ing. Here, when the outside air temperature is below the freezing point, the condensed water may freeze in the steam loop. In order to prevent the condensed water from freezing, a countermeasure may be considered in which an electric heater for preventing freezing in the steam loop is provided and heat is applied to the steam loop. However, when the electric heater is operated, a load is generated on the engine as much as the electric heater is operated, and the fuel consumption rate (fuel consumption) of the engine is deteriorated.

  Therefore, an object of the control device disclosed in the present specification is to eliminate freezing of the working fluid for waste heat recovery without deteriorating the fuel consumption rate of the internal combustion engine.

  In order to solve such a problem, the control device disclosed in this specification has a possibility that the working fluid freezes in a steam path in which the working fluid vaporized by waste heat of exhaust gas discharged from the internal combustion engine circulates. The freezing determination means for determining, and when the freezing determination means determines that the working fluid is likely to freeze, the fuel consumption worsened when the heating device provided on the steam path is operated, The calculation means for calculating the fuel efficiency improved by locally warming up the components of the internal combustion engine using the vaporized working fluid, and the fuel efficiency improved by the local warm-up operated the heating device. Control means for operating the heating device when the fuel consumption is worsened.

  According to the above configuration, in order to operate the heating device when the fuel consumption improved by local warm-up exceeds the fuel consumption deteriorated when the heating device is operated, without deteriorating the fuel consumption rate of the internal combustion engine, Freezing of working fluid for waste heat recovery is eliminated.

  According to the control device disclosed in the present specification, freezing of the working fluid for waste heat recovery is eliminated without deteriorating the fuel consumption rate of the internal combustion engine.

FIG. 1 is a diagram schematically illustrating a configuration of a waste heat utilization system according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of the exhaust heat recovery device. FIG. 3 is a conceptual diagram for explaining heat exchange between the vaporized working fluid and the crank cap. FIG. 4 is a flowchart illustrating an example of processing executed by the ECU. FIG. 5A is an example of a map for calculating the local warm-up fuel efficiency effect from the water temperature and the outside temperature, and FIG. 5B is an example of a map for calculating the fuel efficiency deterioration from the outside temperature. .

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  An example of the configuration of a waste heat utilization system including a control device according to the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating a configuration of a waste heat utilization system 100 according to the embodiment.

  The waste heat utilization system 100 includes an engine 10, an exhaust heat recovery device 20, a steam circulation pipe 30, and a condensate circulation pipe 40.

  The exhaust heat recovery device 20 includes an exhaust gas passage 12 through which exhaust gas discharged from the engine 10 flows, and vaporizes the working fluid by waste heat of the exhaust gas. In this embodiment cooling, the working fluid is described as being water, but the working fluid is not limited to water. Details of the exhaust heat recovery unit 20 will be described later.

  The steam distribution pipe 30 is drawn into the engine 10. The working fluid vaporized by the exhaust heat recovery unit 20 flows through the steam distribution pipe 30 as indicated by solid arrows, and exchanges heat with the crank cap 11 in the engine 10. Thereby, local warming-up is performed. In the present embodiment, the crank cap 11 is selected as the part for performing the local warm-up, but the part for performing the local warm-up is not limited to the crank cap 11 and is another component of the engine 11. Also good.

  The condensate circulation pipe 40 is connected to the exhaust heat recovery device 20. The working fluid condensed by exchanging heat with the crank cap 11 in the engine 10 circulates through the condensate circulation pipe 40 as indicated by the broken arrow and returns to the exhaust heat recovery device 20. In this way, the steam circulation pipe 30, the exhaust heat recovery device 20, and the condensate circulation pipe 40 are connected to form a loop-shaped path through which the working fluid circulates as indicated by a dotted line in the figure. . Hereinafter, a loop path through which the working fluid circulates is referred to as a steam loop (corresponding to a steam path).

  An electric heater 50 is provided on the condensate circulation pipe 40 to prevent the condensed water from freezing. The electric heater 50 is controlled to be turned on and off by an ECU (Electronic Control Unit) 60 described later.

  In addition, the waste heat utilization system 100 includes an ECU 60 that functions as a freezing determination unit, a calculation unit, and a control unit. The ECU 60 includes an outside air temperature meter 71 that measures the outside air temperature, a thermometer 72 that measures the surface temperature of the condensate circulation pipe 40, a water temperature meter 73 that measures the temperature of the working fluid in the exhaust heat recovery device 20, and an electric heater. 50 is electrically connected.

  The ECU 60 obtains the pipe surface temperature of the condensate circulation pipe 40 from the thermometer 72, and determines whether or not there is a possibility that the condensed water in the steam loop is frozen (hereinafter, described as the possibility of freezing). To do. For example, the ECU 60 determines that there is a possibility of freezing when the pipe surface temperature is lower than the freezing point of the working fluid by a predetermined temperature (for example, 5 degrees). Further, the ECU 60 obtains the outside air temperature from the outside air temperature meter 71 and obtains the temperature of the working fluid in the exhaust heat recovery device 20 from the water temperature meter 73. The ECU 60 calculates the fuel efficiency that is improved by local warm-up from the acquired outside air temperature and working fluid temperature. Further, the ECU 69 calculates the fuel efficiency that deteriorates when the electric heater 50 is operated from the outside air temperature. The ECU 60 controls on / off of the electric heater 50 based on the calculated fuel consumption.

  Next, the configuration of the exhaust heat recovery unit 20 will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the configuration of the exhaust heat recovery unit 20.

  After heat exchange with the crank cap 11, the condensed working fluid is recovered from the condensate circulation pipe 40 to the exhaust heat recovery device 20. An exhaust gas passage 12 is disposed in the exhaust heat recovery device 20, and the liquid-phase working fluid recovered in the exhaust heat recovery device 20 exchanges heat with the exhaust gas and boils. The boiled working fluid is circulated from the steam distribution pipe 30 to the engine 10.

  Next, heat exchange between the vaporized working fluid and the crank cap 11 will be described with reference to FIG. FIG. 3 is a conceptual diagram for explaining heat exchange between the vaporized working fluid and the crank cap 11.

  FIG. 3A is a conceptual top view of the engine 10. As shown in FIG. 3A, a steam pipe 31 is provided in the engine 10 so that steam generated in the exhaust heat recovery unit 20 is supplied to the crank cap 11 provided in each cylinder. It has been.

  FIG. 3B is a conceptual cross-sectional view of the engine 10. As shown in FIG. 3B, a steam supply unit 32 that performs heat exchange with the crank cap 11 is disposed at the tip of the steam pipe 31. The steam that has flowed to the steam supply unit 32 exchanges heat with the crank cap 11, thereby locally warming up the engine 10. The working fluid condensed by heat exchange with the crank cap 11 in the steam supply section 32 flows from the condensate return pipe 33 to the condensate circulation pipe 40.

  Next, an example of processing executed by the ECU 60 will be described. FIG. 4 is a flowchart illustrating an example of processing executed by the ECU 60.

  The ECU 60 first determines whether or not the condensed water in the steam loop may be frozen (step S10). For example, the ECU 60 determines that the condensed water may be frozen when the pipe surface temperature of the condensate circulation pipe 40 is lower than the freezing point of the working fluid by a predetermined temperature. The method for determining freezing is not limited to the above. For example, the ECU 60 may determine the possibility of freezing using the outside air temperature and the vehicle speed. Specifically, when the outside air temperature is lower than the freezing point of the working fluid and the heat transfer amount with respect to the vehicle speed determined from the map is larger than the actual heat transfer amount, the ECU 60 may be frozen. You may judge. Further, the ECU 60 may determine the possibility of freezing using the outside air temperature and the parking time. Specifically, when the outside air temperature is lower than the freezing point of the working fluid and the parking time exceeds a predetermined time, the ECU 60 may determine that there is a possibility of freezing. Further, the ECU 60 may determine the possibility of freezing using the pressure in the steam loop. Specifically, the ECU 60 may determine that there is a possibility of freezing when the current pressure in the steam loop is lower than the normal pressure in the loop.

  If it is determined that the condensed water in the steam loop is not likely to freeze (step S10 / NO), the ECU 60 repeats the process of step S10 to monitor the possibility of freezing.

  When it determines with the possibility that the condensed water in a steam loop may freeze (step S10 / YES), ECU60 calculates a local warming-up fuel consumption effect from water temperature and external temperature (step S12). Specifically, the local warm-up fuel efficiency effect is calculated from the water temperature and the outside air temperature using the map shown in FIG. Here, the local warm-up fuel efficiency effect indicates how much the fuel efficiency is improved by performing the local warm-up as compared to the fuel efficiency when the local warm-up is not performed.

  FIG. 5A is an example of a map for calculating the local warm-up fuel efficiency effect from the water temperature and the outside air temperature. In FIG. 5A, each curve represents the local warm-up fuel efficiency effect for each outside air temperature. In FIG. 5A, the ECU 60 determines the value of the local warm-up fuel efficiency effect at the intersection of the straight line vertically extended from the water temperature acquired from the water temperature meter 73 and the curve corresponding to the outside air temperature acquired from the outside air temperature meter 71 ( α) is obtained. FIG. 5A shows that when the water temperature is the same, the local warm-up fuel consumption effect increases as the outside air temperature decreases. Moreover, a local warming-up fuel consumption effect becomes high, so that water temperature is low.

  Returning to FIG. Next, the ECU 60 calculates fuel efficiency (deterioration of fuel efficiency) that deteriorates when the electric heater 50 is operated from the outside air temperature (step S14). Specifically, fuel consumption deterioration is calculated based on the outside air temperature using the map shown in FIG. Here, the deterioration in fuel consumption indicates how much the fuel consumption deteriorates by operating the electric heater 50 as compared to the fuel consumption when the electric heater 50 is not operated.

  FIG. 5B is an example of a map for calculating deterioration in fuel consumption from the outside air temperature. In FIG. 5B, the curve represents the relationship between the outside air temperature and fuel consumption deterioration. In FIG. 5B, the ECU 60 acquires the fuel consumption deterioration (β) at the point where the straight line extending from the outside air temperature obtained from the outside air temperature meter 71 and the curve intersect.

  Next, the ECU 60 determines whether or not the local warm-up fuel efficiency effect (α) is greater than the fuel efficiency deterioration (β) caused by operating the electric heater 50 (step S16). That is, the fuel consumption improved by the local warm-up and the fuel consumption deteriorated by operating the electric heater 50 are compared. When the local warm-up fuel efficiency effect (α) is larger than the fuel efficiency deterioration (β) (step S16 / YES), the ECU 60 turns on the electric heater 50 (step S18). For example, when the fuel efficiency is improved by 5% due to local warm-up and the fuel efficiency is deteriorated by 3% by operating the electric heater 50, the ECU 60 turns on the electric heater 50. Thereby, the electric heater 50 operates and the freezing in the steam loop is eliminated. Moreover, since the fuel consumption deteriorated by the operation of the electric heater 50 can be covered by the fuel efficiency improved by the local warm-up, the deterioration of the fuel consumption of the engine 10 is suppressed.

  On the other hand, when the local warm-up fuel efficiency effect (α) is smaller than the fuel efficiency deterioration (β) (step S16 / NO), the ECU 60 turns off the electric heater 50 (step S20). For example, when the fuel efficiency is improved by 3% due to local warm-up and the fuel efficiency is deteriorated by 5% by operating the electric heater 50, the ECU 60 turns off the electric heater 50. As a result, since the fuel consumption is not deteriorated by operating the electric heater 50 by turning off the electric heater 50, the deterioration of the fuel consumption of the engine 10 is suppressed. The freezing in the steam loop is eliminated by heat generated by heat transfer from the exhaust heat recovery device 20 to the steam loop.

  The ECU 60 repeats the processing from step S10 after step S18 or step S20. When the electric heater 50 is turned on in step S18, the water temperature of the working fluid in the exhaust heat recovery device 20 increases with the passage of time, so the local warm-up fuel consumption effect decreases with the passage of time, and the electric When the fuel consumption is deteriorated due to the operation of the heater 50, that is, when β> α, the electric heater 50 is turned off.

  As described above, the ECU 60 according to the above-described embodiment deteriorates when the electric heater 50 provided on the steam loop is operated when the condensed water may be frozen in the steam loop. The fuel efficiency and the fuel efficiency that is improved by locally warming up the crank cap 11 that is a component part of the engine 10 by using steam obtained by vaporizing the exhaust gas are calculated. The electric heater 50 is actuated when the fuel consumption that deteriorates when the actuator 50 is activated is exceeded. Thereby, when freezing occurs in the steam loop, it is possible to eliminate the freezing in the steam loop without causing deterioration in fuel consumption and to perform early warm-up.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

DESCRIPTION OF SYMBOLS 10 ... Engine 11 ... Crank cap 12 ... Exhaust gas passage 20 ... Exhaust heat recovery device 30 ... Steam distribution pipe 31 ... Steam pipe 32 ... Steam supply part 33 ... Condensate return pipe 40 ... Condensate distribution pipe 50 ... Electric heater 60 ... ECU
71 ... Outside temperature meter 72 ... Thermometer 73 ... Water temperature meter 100 ... Waste heat utilization system

Claims (1)

Freezing determination means for determining the possibility of the working fluid freezing in the steam path in which the working fluid vaporized by the waste heat of the exhaust gas discharged from the internal combustion engine circulates;
When the freezing determination means determines that the working fluid is likely to freeze, the fuel consumption that deteriorates when the heating device provided on the steam path is activated, and the components of the internal combustion engine Calculating means for calculating fuel efficiency that is improved by locally warming up using the vaporized working fluid;
Control means for operating the heating device when the fuel efficiency improved by the local warming exceeds the fuel consumption that deteriorates when the heating device is operated,
A control device comprising:

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