JP2013087693A - Exhaust heat utilization system for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust heat utilization system for an engine in which a rise of pressure in a circulation passage circulating a heat transport medium can be suppressed and which appropriately heats a warmup portion.SOLUTION: An exhaust heat utilization system 1 for an engine includes an exhaust heat collector 11, supply piping 12, return piping 13, a control valve 14 and an ECU 50. The exhaust heat collector 11 performs heat exchange between the exhaust gas of an engine 20 and a heat transport medium to collect heat from the exhaust gas and evaporates the transport medium. The supply piping supplies the evaporated transport medium from the exhaust heat collector 11 to a crank cap. The return piping returns the transport medium supplied to the crank cap to the exhaust heat collector. The control valve is provided in the return piping 13 and controls a flow of the transport medium. The ECU performs control to close the control valve 14 at latest in a state that the warmup of the engine 20 is completed.

Description

  The present invention relates to an exhaust heat utilization device for an engine.

  2. Description of the Related Art A transport medium circulation type engine exhaust heat utilization device that recovers heat from exhaust with a circulating heat transport medium, vaporizes it, and dissipates heat to an object to be heated is known (for example, see Patent Document 1). In addition, as a technique considered to be related to the present invention, techniques for recovering heat using Rankine cycle and using it for power are disclosed in Patent Documents 2 and 3, for example.

JP 2008-169750 A

  In an exhaust heat utilization device for a transport medium circulation type engine, a warm-up part (for example, a crank cap) of the engine can be targeted for heating. However, in this case, when the engine warms up, even if heat is recovered from the exhaust and the transport medium is vaporized, heat is not radiated from the vaporized transport medium to the warm-up site. There is a risk that the pressure will rise and cause damage.

  In view of the above problems, an object of the present invention is to provide an engine exhaust heat utilization device that can suppress an increase in pressure in a circulation path for circulating a heat transport medium and that can suitably warm a warm-up part. And

  The present invention recovers heat from the exhaust by exchanging heat between the exhaust of the engine and the heat transport medium, and heats the engine from the exhaust heat recoverer. A supply pipe for supplying a vaporized transport medium to the machine part, a return pipe for returning the transport medium supplied to the warm-up part to the exhaust heat recovery unit, and a return pipe for controlling the flow of the transport medium An exhaust heat utilization device for an engine, comprising: a control valve; and a control unit that controls the control valve to be closed when the engine has been warmed up at the latest.

  The present invention further includes a calculation unit that calculates an amount of heat that can be received from a transport medium by the warm-up part according to the temperature of the warm-up part after the engine stops, The control valve can be configured to open and close according to the amount of heat calculated by the calculation unit.

  ADVANTAGE OF THE INVENTION According to this invention, the raise of the pressure in the circulation path which circulates the heat | fever transport medium can be suppressed, and also a heating object can be heated suitably.

It is a figure which shows the whole structure of the exhaust-heat utilization apparatus of an engine. It is a figure which shows the control action of ECU with a flowchart.

  Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of an engine exhaust heat utilization device (hereinafter simply referred to as an exhaust heat utilization device) 1. FIG. 1A shows the overall configuration in a top view, and FIG. 1B shows the overall configuration in a side view. The exhaust heat utilization device 1 includes a warm-up device 10 and an ECU 50. The warm-up device 10 includes an exhaust heat recovery device 11, a supply pipe 12, a return pipe 13, a control valve 14, a tank 15, a branch supply pipe 16, and a merging return pipe 17. The warm-up device 10 is sealed with a heat transport medium (for example, H ₂ O).

  The exhaust heat recovery device 11 is a heat exchanger and is provided in the exhaust pipe 25 of the engine 20. The exhaust heat recovery device 11 includes a wick portion 11a that divides the inside into an air chamber R1 and a liquid chamber R2. The air chamber R1 is disposed on the supply pipe 12 side, and the liquid chamber R2 is disposed on the return pipe 13 side. The wick portion 11a is a porous structure, and takes in and holds a transport medium in a liquid phase state from the liquid chamber R2 by capillary action. In this respect, the warming-up device 10 is depressurized to, for example, 10 kPa or less so that the transport medium in the liquid chamber R2 is in a liquid phase state under the usage environment. The transport medium held in the wick portion 11a evaporates due to the heat of the exhaust, and becomes vapor and flows into the air chamber R1. The exhaust heat recovery device 11 recovers heat from the exhaust by exchanging heat between the exhaust and the transport medium in this way, and vaporizes the transport medium.

  The supply pipe 12 supplies steam, which is a vaporized transport medium, from the exhaust heat recovery device 11 to the engine 20. The supplied steam releases heat in the engine 20 and condenses. Then, the condensed transport medium returns to the exhaust heat recovery device 11 via the return pipe 13. In this respect, the exhaust heat recovery unit 11 is provided so as to return the transport medium condensed by the action of gravity from the engine 20 together with the return pipe 13.

  Specifically, a portion of the engine 20 to which steam is supplied is a crank cap. The crank cap is a warm-up part of the engine 20. The warm-up part is a part where the temperature rises as the engine 20 warms up. For example, a part where the effect of reducing friction loss can be obtained as the engine 20 warms up can be set as the warm-up part.

  The control valve 14 is provided in the return pipe 13. The control valve 14 controls the flow of the transport medium that flows through the return pipe 13. The tank 15 is provided in a portion upstream of the control valve 14 in the return pipe 13. The tank 15 stores the condensed transport medium. In the return pipe 13, a section from the control valve 14 to the tank 15 is provided adjacent to the crank cap. In this section, the transport medium stays when the control valve 14 is closed. The branch supply pipe 16 is branched from the supply pipe 12 to the heat exchanger 30. The junction return pipe 17 is joined and connected from the heat exchanger 30 to the return pipe 13. The heat exchanger 30 is a heat exchanger for immediate effect heating that heats the air by exchanging heat between the air and the transport medium.

  The branch supply pipe 16 supplies a part of the steam from the supply pipe 12 to the heat exchanger 30. The junction return pipe 17 releases heat by the heat exchanger 30, and supplies the condensed transport medium to the return pipe 13 to return to the exhaust heat recovery unit 11. The condensed transport medium is supplied from the junction return pipe 17 to the return pipe 13 by the action of gravity. Specifically, the merging return pipe 17 is connected to a portion of the return pipe 13 upstream of the control valve 14. More specifically, this portion is a portion on the downstream side of the tank 15. The warming device 10 is filled with a transport medium as much as necessary for warming up the crank cap and immediate heating (here, 150 cc).

  The ECU 50 is an electronic control device, and the control valve 14 is electrically connected to the ECU 50 as a control target. Further, the ECU 50 is electrically connected with a water temperature sensor 41 and an ignition SW (IGSW) 42 for detecting the cooling water temperature THW of the engine 20. In the ECU 50, for example, the following control unit and calculation unit are functionally realized by the CPU executing a process based on a program stored in the ROM while using a temporary storage area of the RAM as necessary.

  The control unit performs control so that the control valve 14 is closed at the latest when the engine 20 has been warmed up. In closing the control valve 14 in a state where the warm-up of the engine 20 is completed at the latest, the control unit controls to close the control valve 14 after the engine 20 is stopped until the warm-up is completed. can do. Specifically, the control unit closes the control valve 14 by opening and closing (opening and closing) the control valve 14 after the engine 20 is stopped.

The calculation unit calculates the amount of heat Q that the crank cap can receive from the transport medium according to the temperature of the crank cap after the engine 20 is stopped. The amount of heat Q can be calculated by the following equation (1), for example.
Q = Cp * M * (Tcap-THW) (1)
Here, Cp is the specific heat of the crank cap, M is the mass of the crank cap, and Tcap is the temperature after the crank cap is warmed up, and these are known in advance. In the equation (1), the coolant temperature THW is used instead of the temperature of the crank cap as representatively indicating the temperature of the entire engine 20 including the clamp cap.

  While the calculation unit calculates the heat quantity Q, more specifically, the control unit opens and closes the control valve 14 according to the heat quantity Q after the engine 20 is stopped. Then, the control unit opens and closes the control valve 14 according to the heat quantity Q, and supplies the transport medium to the exhaust heat recovery device 11 by an amount necessary for transporting heat for the heat quantity Q to the crank cap. In this way, in supplying the transport medium, the calculation unit and the control unit are specifically realized as described below.

  That is, the calculation unit calculates a transport medium amount W necessary to transport heat for the heat amount Q to the crank cap based on the heat amount Q and the vaporization latent heat of the transport medium, and calculates the transport medium amount W and the control valve. The valve opening time T required to supply the calculated transport medium amount W to the exhaust heat recovery device 11 is calculated based on the flow rate of the transport medium when the valve 14 is opened. The control unit opens and closes the control valve 14 by opening the control valve 14 for the valve opening time T calculated by the calculation unit.

  In calculating the heat quantity Q after the engine 20 is stopped, the calculation unit specifically calculates the heat quantity Q at all times. Then, the heat quantity Q is continuously calculated until there is no transport medium retained by the control valve 14 or the engine 20 is restarted. In this case, the calculation unit updates the previously calculated transport medium amount W and valve opening time T each time the heat amount Q is newly calculated. The calculation unit may calculate the heat quantity Q at an appropriate timing such as every predetermined time interval or when the engine 20 is restarted.

  Next, the control operation of the ECU 50 will be described using the flowchart shown in FIG. This flowchart is started after the engine 20 is stopped. The ECU 50 calculates the heat quantity Q (step S1). Further, the transport medium amount W is calculated (step S2), and the valve opening time T is calculated (step S3). Specifically, the transport medium amount W can be calculated by dividing the amount of heat Q by the latent heat of vaporization of the transport medium. The valve opening time T can be calculated by dividing the transport medium amount W by the transport medium flow rate when the control valve 14 is opened.

  Subsequently, the ECU 50 opens the control valve 14 (step S4). Then, after the valve opening time T has elapsed, the control valve 14 is closed (step S5). Thereby, the control valve 14 is opened and closed according to the heat quantity Q after the engine 20 is stopped. Subsequent to step S5, the ECU 50 determines whether or not the transport medium retained by the control valve 14 is exhausted (step S6). Whether or not there is no transport medium remaining in the control valve 14 is determined, for example, based on whether or not the calculated transport medium amount W is equal to (or is equal to) the transport medium enclosed amount of the warm-up device 10. it can.

  If a negative determination is made in step S6, the ECU 50 determines whether or not the engine 20 has been restarted (step S7). If a negative determination is made, the process returns to step S1. As a result, the amount of heat Q is constantly calculated until there is no transport medium retained by the control valve 14 after the engine 20 is stopped or until the engine 20 is restarted. On the other hand, if the determination in step S6 or S7 is affirmative, this flowchart is terminated.

  Next, the effect of the exhaust heat utilization apparatus 1 will be described. The exhaust heat utilization device 1 performs control so that the control valve 14 is closed at the latest when the engine 20 has been warmed up. As a result, by stopping the supply of the transport medium to the exhaust heat recovery device 11, steam is continuously generated when heat is not actually transmitted from the vaporized transport medium to the crank cap or when it is not performed. To suppress that. For this reason, the exhaust heat utilization apparatus 1 can suppress an increase in pressure in the circulation path of the transport medium.

  The exhaust heat utilization device 1 calculates the heat quantity Q according to the temperature of the crank cap after the engine 20 is stopped, and opens and closes the control valve 14 according to the heat quantity Q. For this reason, the exhaust heat utilization apparatus 1 supplies the transport medium to the exhaust heat recovery device 11 as much as necessary for warming up the crank cap in preparation for restart of the engine 20, so that the crank is removed from the vaporized transport medium. When the heat radiation to the cap is not performed, the generation of steam itself can be prevented.

  As a result, it is possible to favorably promote the warm-up of the crank cap in that the warm-up of the crank cap can be promoted to the maximum while suppressing an increase in the pressure in the circulation path of the transport medium. In addition, for example, when the engine 20 in a warm-up state is restarted immediately after being stopped, steam can be prevented from being generated.

  The exhaust heat utilization device 1 is provided with a section of the return pipe 13 from the control valve 14 to the tank 15 adjacent to the crank cap. For this reason, the exhaust heat utilization apparatus 1 can delay freezing of the transport medium retained by the control valve 14 even when the transport medium may freeze when the engine 20 is stopped. Thus, for example, even when the control valve 14 is opened and closed when the engine 20 is restarted, it is easy to avoid a situation in which the crank cap cannot be warmed up as a result of the transport medium not being supplied to the exhaust heat recovery device 11 due to freezing. can do. In this regard, the exhaust heat utilization apparatus 1 freezes the transport medium retained by the control valve 14 by providing a heat insulating material in a section of the return pipe 13 from the control valve 14 to the tank 15 to enhance the heat insulation. Can be delayed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

Exhaust heat utilization device 1
Warming-up device 10
Exhaust heat recovery unit 11
Supply piping 12
Return piping 13
Control valve 14
Engine 20
ECU 50

Claims (2)

An exhaust heat recovery unit that recovers heat from the exhaust by exchanging heat between the engine exhaust and the heat transport medium, and vaporizes the transport medium;
A supply pipe for supplying a vaporized transport medium from the exhaust heat recovery device to a warm-up part of the engine;
A return pipe for returning the transport medium supplied to the warm-up site to the exhaust heat recovery unit;
A control valve provided in the return pipe for controlling the flow of the transport medium;
An engine exhaust heat utilization device comprising: a control unit configured to control the control valve to close when the engine has been warmed up at the latest. An exhaust heat utilization device for an engine according to claim 1,
The engine further includes a calculation unit that calculates the amount of heat that the warm-up part can receive from the transport medium according to the temperature of the warm-up part after the engine is stopped.
An exhaust heat utilization device for an engine that opens and closes the control valve according to the amount of heat calculated by the calculation unit after the control unit has stopped the engine.

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