JP2008231981A - Waste heat recovery apparatus for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste heat recovery apparatus capable of surely enhancing cycle efficiency by implementing properly circulation flow rate control of Rankine cycle circuit. <P>SOLUTION: A waste heat recovery apparatus includes a Rankine cycle circuit (8) including a closed circuit (9) having an evaporator (10), an expander (12), a condenser (14), a pump (16); a bypass circuit (20) having a recovery valve (32) for recovering liquid working-fluid from a high pressure circuit portion (9d), and a supply valve (36) for supplying liquid working-fluid to a low pressure circuit portion (9b); and a circulation flow volume control means for opening/closing the recovery valve and the supply valve, depending on the supercooling degree of working-fluid by way of the condenser, and controlling the volume of the working-fluid that circulates through a closed circuit. A bypass flow path is disposed with a deceleration mechanism (34, 38) for reducing the flow velocity of working-fluid that outflows from the recovery valve and the supply valve. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine waste heat utilization device, and more particularly to an internal combustion engine waste heat utilization device suitable for a vehicle.

As an internal combustion engine waste heat utilization device, for example, an evaporator that heats a working fluid (hereinafter referred to as a refrigerant) with waste heat from a vehicle engine, an expander that expands the refrigerant to generate a driving force, and condenses the refrigerant There is known a Rankine cycle circuit composed of a closed circuit in which a condenser and a pump for pumping and circulating a refrigerant are sequentially connected.
And in such a Rankine cycle circuit, by providing a bypass path that bypasses the condenser and the pump, by taking the refrigerant into and out of the bypass path according to the degree of supercooling of the refrigerant condensed via the condenser, A technique for improving the cycle efficiency of a Rankine cycle circuit while controlling the amount of refrigerant circulating in the closed circuit and preventing pump cavitation is known (see, for example, Patent Document 1).
JP-A-60-192809

By the way, in the above prior art, solenoid valves are provided at the inlet and outlet of the bypass passage, respectively, and on-off control is performed such that these solenoid valves are fully opened and closed according to the degree of supercooling, whereby the refrigerant is stepped into the bypass passage. Has been put in and out.
However, with only on / off control of the solenoid valve, even if the number of solenoid valves is increased or the on / off timing of the solenoid valves is set finely, as long as the solenoid valve is fully opened and fully controlled, It is difficult to properly control the amount of refrigerant that is taken in and out of the bypass path, and thus the amount of refrigerant that is circulated in the Rankine cycle circuit, according to the degree of supercooling that varies depending on the operating conditions and climatic conditions. There is a problem that cannot be obtained.

In addition, since the on-off control for fully opening and closing each solenoid valve stepwise is performed, the refrigerant in the bypass passage is temporarily in a liquid-sealed state, and when this liquid-sealed refrigerant expands due to a temperature rise, the bypass passage, and thus There is also a problem that the entire Rankine cycle circuit is damaged.
The present invention has been made in view of such problems, and provides a waste heat utilization device for an internal combustion engine that can reliably improve cycle efficiency by appropriately performing circulation flow control of a Rankine cycle circuit. The purpose is to do.

  In order to achieve the above object, the waste heat utilization apparatus for an internal combustion engine according to claim 1 is a waste heat utilization apparatus for recovering heat from the heat medium of the internal combustion engine, and operates by exchanging heat with the heat medium. An evaporator that heats the fluid, an expander that generates a driving force by expanding the working fluid that passes through the evaporator, a condenser that condenses the working fluid that passes through the expander, and a working fluid that passes through the condenser Including a pump for pumping toward the evaporator, forming a high-pressure circuit section in which the working fluid exhibits a high pressure from the outlet side of the pump to the inlet side of the expander, and working fluid from the outlet side of the expander to the inlet side of the condenser Are provided in the vicinity of the high-pressure circuit portion of the bypass path, the closed circuit that forms a low-pressure circuit section that exhibits a low pressure, the high-pressure circuit section and the low-pressure circuit section that communicate with each other and bypass the condenser and the pump. High pressure circuited into the bypass by a valve A recovery valve that recovers the liquid working fluid from the section, a supply valve that is provided near the low-pressure circuit section of the bypass passage, and that supplies the liquid working fluid from the bypass passage to the low-pressure circuit section by opening the valve, and a condenser A Rankine cycle circuit having a circulation flow rate control means for opening and closing the recovery valve and the supply valve and controlling the amount of the working fluid circulating in the closed circuit in accordance with the degree of supercooling of the working fluid that has passed through the vessel. Is characterized in that a speed reduction mechanism for reducing the flow velocity of the working fluid flowing out from the recovery valve and the supply valve is arranged.

The invention according to claim 2 is characterized in that, in claim 1, the bypass passage has a tank for temporarily storing the working fluid recovered by opening the recovery valve.
Further, the invention according to claim 3 is characterized in that, in claim 2, the tank has a depressurization means for depressurizing the working fluid stored from the tank toward the high pressure circuit section.

Furthermore, in the invention according to claim 4, in any one of claims 1 to 3, the circulating flow rate control means keeps the degree of supercooling at a predetermined minimum value within a range in which pump cavitation can be avoided. Therefore, the recovery valve and the supply valve are opened and closed, and the amount of working fluid circulating in the closed circuit is controlled.
According to a fifth aspect of the present invention, in any one of the second to fourth aspects, the Rankine cycle circuit controls the tank internal pressure so that the internal pressure of the tank is an intermediate pressure that is lower than the high pressure circuit and higher than the low pressure circuit. It is characterized by having a means.

  Further, in the invention described in claim 6, in claim 5, the Rankine cycle circuit includes a high-pressure path that communicates between the tank and the high-pressure circuit section, a low-pressure path that communicates between the tank and the low-pressure circuit section, and valve opening to increase the pressure. The tank internal pressure control means further includes a high pressure valve that allows the gaseous working fluid to flow into the tank from the circuit section, and a low pressure valve that causes the gaseous working fluid to flow out from the tank to the low pressure circuit section when the valve is opened. The internal pressure of the tank is detected by the internal pressure detected by the internal pressure detection means, and the high pressure valve and the low pressure valve are opened and closed to set the internal pressure of the tank to an intermediate pressure. The passage is characterized by a second speed reduction mechanism for reducing the flow velocity of the working fluid flowing out from the high pressure valve and the low pressure valve, respectively.

  Furthermore, in the invention described in claim 7, in any one of claims 1 to 6, the speed reduction mechanism and the second speed reduction mechanism are capillary tubes.

  According to the waste heat utilization apparatus for an internal combustion engine of the first aspect of the present invention, the Rankine cycle circuit includes a closed circuit including a high-pressure circuit unit and a low-pressure circuit unit, and a bypass path, and the liquid operation to the bypass path is performed. Circulating flow rate control means for controlling the amount of working fluid circulating in the closed circuit is implemented by opening and closing a recovery valve for recovering fluid and a supply valve for supplying liquid working fluid from the bypass passage to the low pressure circuit section. A speed reduction mechanism that reduces the flow rate of the working fluid flowing out from the recovery valve and the supply valve is disposed in the bypass path. As a result, the flow rate of the working fluid collected in the bypass passage and supplied from the bypass passage can be reduced as compared with the case where the recovery valve and the supply valve are simply opened and closed. Can be controlled smoothly and smoothly, and the control stability of the circulating flow rate control means, and consequently the cycle efficiency of the Rankine cycle circuit, can be reliably improved.

According to the second aspect of the present invention, since the bypass passage has the tank that temporarily stores the working fluid recovered by the recovery valve, the amount of the working fluid that can be taken in and out of the closed circuit from the bypass passage can be increased. it can. Thereby, the control range of the circulating refrigerant control means can be set as wide as possible in accordance with the fluctuation range of the degree of supercooling, and the controllability of the circulating flow rate control means can be further improved.
Furthermore, according to the invention of claim 3, the tank has a depressurizing means for the stored working fluid, and when the inside of the tank is in a liquid-sealed state, the temperature of the working fluid stored in the tank rises. Even if it expands, the bypass passage and thus the Rankine cycle circuit can be reliably prevented from being destroyed, and the circulation flow rate control means can be more appropriately implemented.

Furthermore, according to the fourth aspect of the present invention, since the degree of supercooling of the Rankine cycle circuit can be kept to a minimum as long as cavitation of the pump does not occur, the cycle efficiency of the Rankine cycle circuit can be greatly improved.
According to the invention described in claim 5, the Rankine cycle circuit has tank internal pressure control means for setting the internal pressure of the tank to an intermediate pressure that is lower than the high pressure circuit and higher than the low pressure circuit. The pressure difference between the high-pressure circuit and the low-pressure circuit is appropriate, and the recovery of the working fluid from the high-pressure circuit and the supply of the working fluid to the low-pressure circuit can be performed more smoothly. Stability can be further improved.

  Further, according to the invention of claim 6, the tank internal pressure control means opens and closes the high pressure valve and the low pressure valve to the intermediate pressure according to the detected internal pressure of the tank. A second reduction mechanism that reduces the flow rate of the gaseous working fluid flowing out from the high pressure valve and the low pressure valve is arranged. As a result, the flow rate of the gaseous working fluid flowing into the high pressure path and flowing out from the low pressure path can be reduced compared to when the high pressure valve and the low pressure valve are simply opened and closed. Control can be performed continuously and smoothly, the control stability of the tank internal pressure control means, and further the control stability of the circulation flow rate control means, can be further improved, and the cycle efficiency of the Rankine cycle circuit can be further improved.

  Furthermore, according to the seventh aspect of the present invention, the above-mentioned special effects can be obtained with a simple configuration in which a capillary tube is simply provided on the secondary side of the valve to be opened and closed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the first embodiment will be described.
FIG. 1 is a schematic diagram showing the configuration of a waste heat utilization device 2 for an internal combustion engine according to the present embodiment. The waste heat utilization device 2 is a cooling system that circulates cooling water and cools, for example, a vehicle engine (internal combustion engine) 4. A water circuit 6 and a Rankine cycle circuit 8 (hereinafter referred to as a cycle 8) that recovers waste heat of the engine 4 through circulation of the refrigerant are configured.

The cooling water circuit 6 constitutes a closed circuit to which the evaporator 10 is connected from the engine 4. For example, the cooling water circulates by driving a water pump (not shown) according to the rotational speed of the engine 4.
The evaporator 10 is a heat exchanger that exchanges heat between the cooling water that circulates in the cooling water circuit 6 and the refrigerant that circulates in the cycle 8. The evaporator 10 uses the cooling water heated by the engine 4, that is, hot water as a heat medium. The waste heat of the engine 4 is collected on the side. On the other hand, the cooling water that has passed through the evaporator 10 and has been absorbed by the refrigerant and has fallen in temperature becomes warm water that has been heated again by cooling the engine 4. Note that a thermostat (not shown) or the like may be installed so as to keep the temperature of the main body of the engine 4 substantially constant.

  On the other hand, the cycle 8 constitutes a closed circuit 9 in which the evaporator 10, the expander 12, the condenser 14, and the refrigerant pump (pump) 16 are connected in order, and the flow path of the closed circuit 9 is in the flow direction of the refrigerant. Thus, a flow path (high pressure circuit section) 9 a extending from the evaporator 10 to the expander 12, a flow path (low pressure circuit section) 9 b extending from the expander 12 to the condenser 14, and the refrigerant pump from the condenser 14 16 includes a flow path 9 c extending to 16 and a flow path (high-pressure circuit section) 9 d returning from the refrigerant pump 16 to the evaporator 10.

The expander 12 is a fluid device that generates a driving force related to rotation or the like by the expansion of the refrigerant heated by the evaporator 10 and in a superheated vapor state. Further, a generator 18 is connected to the expander 12, and the driving force generated by the expander 12 via the generator 18 can be used outside the waste heat utilization device 2.
The condenser 14 is a heat exchanger that condenses and liquefies the refrigerant discharged from the expander 12 by heat exchange with the outside air, and the liquid refrigerant condensed by the condenser 14 is pumped to the evaporator 10 by the refrigerant pump 16. .

The refrigerant pump 16 is an electric pump that drives the movable part in accordance with a signal input to the drive part of the pump 16, and suitably circulates the refrigerant in the entire cycle 8.
And by the said structural apparatus of the closed circuit 9, the high pressure gas refrigerant | coolant heated by the evaporator 10 flows into the flow path 9a, and the low pressure gas refrigerant after driving the expander 12 flows into the flow path 9b. . The low-pressure liquid refrigerant condensed by the condenser 14 flows through the flow path 9c, and the high-pressure liquid refrigerant pressurized by the pump 16 flows through the flow path 9d.

As described above, in the cycle 8, the waste heat of the engine 4 is recovered according to the operating state of the engine 4, and the recovered waste heat is further converted to power and recovered to be usable outside.
By the way, the cycle 8 is provided with a bypass circuit 20 that bypasses the condenser 14 and the pump 16 in addition to the above-described components and the closed circuit 9 including the flow paths 9a to 9d.
Specifically, the bypass path 20 includes a recovery path 22 that branches from the flow path 9d, a supply path 24 that merges with the flow path 9b, a receiver tank (tank) 26 that is positioned between the recovery path 22 and the supply path 24. Yes.

The receiver tank 26 is a sealed tank that separates and stores the refrigerant flowing into the bypass path 20 in two layers of gas and liquid, and a recovery path 22 and a supply path 24 penetrate through and connect to appropriate positions on the side surface of the tank 26. The recovery path 22 and the supply path 24 are both extended to the liquid layer portion of the refrigerant in the tank 26.
In addition, a decompression path (decompression means) 28 of the tank 26 that extends from the gas layer portion of the refrigerant in the tank 26 and joins the flow path 9d is connected to and penetrated at an appropriate position on the side surface of the tank 26. A check valve 30 for interrupting the flow of the refrigerant from the flow path 9d to the tank 26 is inserted in the pressure release path 28.

More specifically, a recovery side solenoid valve (recovery valve) 32 and a recovery side capillary tube (deceleration mechanism) 34 are inserted in the recovery path 22 in order from the flow path 9d side, while the supply path 24 is connected to the tank 26 side. A supply-side solenoid valve (supply valve) 36 and a supply-side capillary tube (deceleration mechanism) 38 are inserted in order.
The capillary tubes 34 and 38 are capillaries made of copper or the like, and the pipe cross-sectional area is set in advance so that the refrigerant flows in the pipe at a predetermined low speed according to the pressure difference between the pipes before and after the pipe. . In other words, the capillaries 34 and 38 allow the refrigerant to pass at a stable low speed by utilizing the pipe resistance when the refrigerant passes and the pressure difference before and after the pipe, and in the capillaries 34 and 38, the refrigerant condenses. There is no evaporation.

The electromagnetic valves 32 and 36 are on / off valves that are fully opened and closed in response to contact signals input to the drive unit, respectively, and are electronic control units that perform comprehensive control of the vehicle and the waste heat utilization device 2 together with the pump 16. (ECU) 40 is electrically connected.
In addition, the ECU 40 is also electrically connected with a pressure sensor 42 for detecting the pressure of the low-pressure liquid refrigerant condensed via the condenser 14 and a temperature sensor 44 for detecting the temperature of the low-pressure liquid refrigerant. The sensors 42 and 44 are installed in the flow path 9c.

  Here, the ECU 40 calculates the degree of supercooling SD (Supercooling Degree) of the low-pressure liquid refrigerant after passing through the condenser 14 based on the detection results of the sensors 42 and 44. Then, by opening and closing the solenoid valves 32 and 36 according to the calculated degree of supercooling SD, the refrigerant recovery amount recovered in the tank 26 from the closed circuit 9 through the recovery path 22, and the supply path from the tank 26, respectively. So-called circulation flow rate control is performed (circulation flow rate control means) for adjusting the refrigerant supply amount supplied toward the closed circuit 9 via 24 and controlling the refrigerant amount circulating in the closed circuit 9.

  Normally, the amount of waste heat of the engine 4 changes depending on the operating state of the engine 4, and the refrigerant condensing temperature and condensing pressure change depending on the outside air temperature and the condenser air volume, so that the optimum refrigerant circulation amount in the closed circuit 9 also changes each time. . For example, when the amount of waste heat of the engine 4 is large or when the condensation temperature becomes high in the summer, the amount of refrigerant circulating in the closed circuit 9 increases, so that the amount of refrigerant necessary in the closed circuit 9 is inevitably large. Become.

However, if the amount of refrigerant required in the closed circuit 9 is large but the actual amount of refrigerant remains small, the degree of supercooling SD becomes small, causing cavitation of the pump 16, and the pump 16 can boost the refrigerant. Disappear.
On the other hand, if the actual amount of refrigerant is too large compared to the required amount of refrigerant in the closed circuit 9, the degree of supercooling SD increases, and the amount of heat required for heating the refrigerant in the evaporator 10 increases accordingly, and the evaporator The load of 10 increases, and the cycle efficiency of the closed circuit 9 decreases.

Therefore, here, the above-mentioned inconvenience is solved by opening and closing the solenoid valves 32 and 36 according to the degree of supercooling SD.
Hereinafter, the control routine related to the circulation flow rate control will be described in detail with reference to the flowchart shown in FIG.
First, in an initial state in S0 (hereinafter, S represents a step), the solenoid valves 32 and 36 are closed, and when the circulation flow control is started, the process proceeds to S1. This control routine has a reset function for returning to the initial state of S0 when the circulation flow rate control is stopped even during execution of the following steps.

In S1, it is determined whether or not the supercooling degree SD is equal to or higher than a predetermined supercooling degree upper limit set value SDH. If the determination result is true (Yes) and the degree of supercooling SD is determined to be greater than or equal to the upper limit set value SDH, the process proceeds to S2, and if the determination result is false (No) and the degree of supercooling SD is less than the upper limit set value SDH. If it is determined, the process proceeds to S3.
When the process proceeds to S2, the electromagnetic valve 32 is opened, and the liquid refrigerant flowing through the flow path 9d is collected in the tank 26. Then, the process proceeds to S4 with the solenoid valve 32 opened.

On the other hand, when it transfers to S3, the solenoid valve 32 is closed and it transfers to S4.
In S4, it is determined whether or not the supercooling degree SD is equal to or lower than a predetermined supercooling degree lower limit set value SDL. If the determination result is true (Yes) and the degree of supercooling SD is determined to be equal to or lower than the lower limit set value SDL, the process proceeds to S5, and if the determination result is false (No) and the degree of supercooling SD is greater than the lower limit set value SDL. If it is determined, the process proceeds to S6.

When the process proceeds to S5, the electromagnetic valve 36 is opened, and the liquid refrigerant stored in the tank 26 is supplied to the flow path 9b. And it transfers to S1 with the solenoid valve 36 opened.
On the other hand, when it transfers to S6, the solenoid valve 36 is closed and it transfers to S1.
Thus, when the control routine related to the circulation flow rate control is started in S0, the above series of steps is repeatedly executed.

  Here, the upper limit set value SDH and the lower limit set value SDL are appropriately calculated and set in the ECU 40 by a signal from a sensor (not shown) that detects the operating state of the engine 4 and the outside air temperature. Then, by setting the difference between the upper limit set value SDH and the lower limit set value SDL as small as possible, for example, it is possible to maintain the supercooling degree SD that is minimum within a range in which cavitation of the pump 26 does not occur, substantially constant.

  The flow rate of the refrigerant passing through the capillaries 34 and 38 is determined almost uniquely from the inherent conditions such as the pipe cross-sectional areas of the capillaries 34 and 38, the pipe resistance, and the pressure difference before and after the capillaries 34 and 38, respectively. . Therefore, the valve opening times of the solenoid valves 32 and 36 in S2 and S5, respectively, to fill the difference between the supercooling degree SD and the upper limit set value SDH in S1 and the difference between the supercooling degree SD and the lower limit set value SDL in S4. , And after the calculated valve opening time has elapsed, the flow from S2 to S4 and from S5 to S1 may be respectively performed, and the circulation flow rate control may be performed so that a desired refrigerant recovery amount and refrigerant supply amount can be obtained. .

As described above, in the present embodiment, the amount of refrigerant circulating in the closed circuit 9 is appropriately controlled according to the degree of supercooling SD.
Further, in the present invention, paying attention to the speed of the refrigerant to be taken in and out between the closed circuit 9 and the bypass passage 20, capillaries 34 and 38 are provided in the recovery passage 22 and the supply passage 24 of the bypass passage 20, respectively, and the electromagnetic valves 32, The flow rate of the refrigerant flowing out from 36 is reduced, and the refrigerant circulating through the closed circuit 9 through these capillaries 34 and 38 is taken in and out. As a result, the flow rate of the working fluid collected in the bypass passage 20 and supplied from the bypass passage 20 can be reduced, so that the existing solenoid valves 32 and 36 are used and the capillaries 34 and 38 are inserted into the bypass passage 20. With this simple configuration, the refrigerant flowing into and out of the bypass passage 20 can be controlled continuously and smoothly, the circulation flow control is appropriately performed, and the circulation flow control is performed while solving the problems caused by excessive and insufficient refrigerant amounts. Thus, the control stability and thus the cycle efficiency of the cycle 8 can be reliably improved.

In particular, in the circulation flow rate control, by setting the upper limit set value SDH and the lower limit set value SDL so as to keep the supercooling degree SD substantially constant at the required minimum value within a range where cavitation of the pump 16 does not occur, cycle efficiency is greatly increased. Can be improved.
Further, by having the tank 26 that temporarily stores the refrigerant flowing into the bypass passage 20, the tank 26 functions as a buffer tank for surplus refrigerant, and a large amount of refrigerant that can be taken in and out of the closed circuit 9 can be obtained. . Thereby, the control range of the circulation flow rate control can be set as wide as possible according to the fluctuation range of the degree of supercooling SD, and the controllability of the circulation flow rate control can be further improved.

In addition, since the tank 26 has the decompression path 28, even if the refrigerant stored in the tank 26 is heated and expanded when the inside of the tank 26 is in a liquid-sealed state, the decompression path 28 is removed from the tank 26. Therefore, the tank 26, the bypass 20, and thus the entire cycle 8 can be reliably prevented from being damaged, and the circulation flow rate can be appropriately controlled.
Next, a second embodiment will be described.

As shown in FIG. 3, the waste heat utilization apparatus 46 of the second embodiment performs tank internal pressure control of the tank 26 on the waste heat utilization apparatus 2 of the first embodiment, and the others are the above. Since the configuration is the same as that of the first embodiment, this difference will be mainly described.
The waste heat utilization device 46 has a high-pressure path 48 branched from the flow path 9 a and a low-pressure path 50 joined to the flow path 9 b, and the high-pressure path 48 and the low-pressure path 50 penetrate at appropriate positions on the side surface of the tank 26. Are connected to each other, and extend to the refrigerant layer in the tank 26.

  A high pressure side solenoid valve (high pressure valve) 52 and a high pressure side capillary tube (second deceleration mechanism) 54 are inserted into the high pressure path 48 in order from the flow path 9a side, while the low pressure path 50 is sequentially inserted from the tank 26 side. A low-pressure side solenoid valve (low-pressure valve) 56 and a low-pressure side capillary tube (second reduction mechanism) 58 are inserted. The capillaries 54 and 58 and the electromagnetic valves 52 and 56 are configured in the same manner as the capillaries 34 and 38 and the electromagnetic valves 32 and 36, respectively, and the electromagnetic valves 52 and 56 are also electrically connected to the ECU 40.

In addition, a pressure sensor (internal pressure detecting means) 60 for detecting a gas layer pressure of the refrigerant stored in the tank 26 is installed at an appropriate position of the upper lid portion of the tank 26. The sensor 60 is also electrically connected to the ECU 40. It is connected.
Then, the ECU 40 opens and closes the electromagnetic valves 52 and 56 according to the detection result of the sensor 60, whereby the internal pressure of the tank 26 is lower than the high-pressure gas refrigerant flowing through the flow path 9a and the low-pressure gas flowing through the flow path 9b. Tank internal pressure control is performed so that the intermediate pressure is higher than that of the refrigerant (tank internal pressure control means).

Hereinafter, the control routine relating to the tank internal pressure control will be described in detail with reference to the flowchart shown in FIG.
First, in the initial state in S00, the solenoid valves 52 and 56 are closed, and when tank internal pressure control is started, the process proceeds to S10. This control routine has a reset function to return to the initial state of S00 when the tank internal pressure control is stopped even during the following steps.

In S10, it is determined whether or not the tank internal pressure P detected by the sensor 60 is greater than or equal to a predetermined tank internal pressure upper limit set value PH. If the determination result is true (Yes) and the tank internal pressure P is determined to be equal to or higher than the upper limit set value PH, the process proceeds to S20, and the determination result is false (No) and the tank internal pressure P is determined to be smaller than the upper limit set value PH. If yes, the process proceeds to S30.
When the process proceeds to S20, the solenoid valve 56 is opened, the gas layer portion of the refrigerant stored in the tank 26 is communicated with the flow path 9b, and the pressure in the tank 26 is released. Then, the process proceeds to S40 with the solenoid valve 56 open.

On the other hand, when it transfers to S30, the solenoid valve 56 is closed and it transfers to S40.
In S40, it is determined whether or not the tank internal pressure P is equal to or lower than a predetermined tank internal pressure lower limit set value PL. If the determination result is true (Yes) and the tank internal pressure P is determined to be equal to or lower than the lower limit set value PL, the process proceeds to S50, and the determination result is false (No) and the tank internal pressure P is determined to be greater than the lower limit set value PL. If yes, the process proceeds to S60.

When the process proceeds to S50, the electromagnetic valve 52 is opened, the gas layer portion of the refrigerant stored in the tank 26 is communicated with the flow path 9a, and the pressure in the tank 26 is increased. Then, the process proceeds to S10 with the solenoid valve 52 open.
On the other hand, when it transfers to S60, the solenoid valve 52 is closed and it transfers to S10.
Thus, when the control routine related to the tank internal pressure control is started in S00, the above series of steps are repeatedly executed.

  Here, the upper limit set value PH is set to the average pressure of the high-pressure gas refrigerant in the flow path 9a, and the lower limit set value PL is set to the average pressure of the low-pressure gas refrigerant in the flow path 9b, whereby the tank internal pressure P is closed. The intermediate pressure between the high-pressure side refrigerant and the low-pressure side refrigerant can be set to a predetermined intermediate pressure by setting the difference between the upper limit set value PH and the lower limit set value PL as small as possible. The pressure can also be kept substantially constant.

  In the tank internal pressure control as well as the circulation flow rate control, the electromagnetic valves 56 and 52 in S20 and S50 are respectively determined from the difference between the tank internal pressure P and the upper limit set value PH and the difference between the tank internal pressure P and the lower limit set value PL. The valve opening time may be calculated, and after the calculated valve opening time has elapsed, the process proceeds from S20 to S40, and from S50 to S10, and the tank internal pressure may be controlled to be an intermediate pressure.

As described above, in the waste heat utilization apparatus 46 according to the second embodiment, the control stability of the circulation flow rate control can be simplified and improved, and the degree of supercooling SD is kept at the necessary minimum value, as in the first embodiment. Thus, the cycle efficiency can be improved reliably and significantly.
In particular, in the case of the second embodiment, by performing tank internal pressure control, the tank internal pressure P becomes an intermediate pressure between the high-pressure refrigerant and the low-pressure refrigerant, and the recovery valve 32 side in which the high-pressure refrigerant flows in the tank 26. And the pressure difference between the tank 26 and the supply valve 36 side through which the low-pressure refrigerant flows can be made appropriate, so that the refrigerant recovery and the refrigerant supply in the circulation flow control can be performed more smoothly. The property can be further improved.

  Moreover, by performing the tank internal pressure control via the capillaries 54 and 58, as in the case of the circulation flow rate control performed via the capillaries 34 and 38, compared with the case where the electromagnetic valves 52 and 56 are simply opened and closed, Since the flow rate of the working fluid flowing in from the high-pressure path 48 and flowing out from the low-pressure path 50 can be reduced, the refrigerant flowing into and out of the tank 26 can be controlled continuously and smoothly, and the control stability of the tank internal pressure control, and hence the circulation The control stability of the flow rate control is further improved, and the cycle efficiency can be further improved.

Although the description of one embodiment of the present invention has been completed above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in each of the above embodiments, a capillary tube is used to restrict the flow rate of the refrigerant. However, it is sufficient that the flow rate of the refrigerant collected and supplied from the closed circuit 9 is reduced. Even if is used, the control stability of the circulation flow rate control is improved, and the cycle efficiency can be reliably improved.

In each of the above embodiments, the flow of the refrigerant into and out of the tank 26 is controlled by the solenoid valve. However, if the flow rate of the refrigerant flowing in and out can be reduced and the amount of the refrigerant can be controlled linearly, the flow passage is interrupted. Even if a linear control valve or the like having a reduced area is used, at least the effects of improving the control stability of the circulation flow rate control and improving the cycle efficiency can be obtained.
Furthermore, in the second embodiment, the circulation flow rate control and the tank internal pressure control are performed as independent control routines. However, these controls may be performed in conjunction with each other. For example, the solenoid valve 32 may be opened. Even if the solenoid valve 56 is opened in conjunction with the solenoid valve 36 and the solenoid valve 52 is opened in conjunction with the opening of the solenoid valve 36, the refrigerant can be smoothly taken in and out of the tank 26. Since the pressure sensor 60 is not required, the control stability and cycle efficiency of the circulation flow rate control can be improved with a simpler configuration.

It is the schematic diagram which showed the waste-heat utilization apparatus of the internal combustion engine which concerns on 1st Embodiment of this invention. 3 is a flowchart showing a control routine of circulation flow rate control executed by the ECU of FIG. 1. It is the schematic diagram which showed the waste-heat utilization apparatus of the internal combustion engine which concerns on 2nd Embodiment of this invention. It is the flowchart which showed the control routine of the tank internal pressure control performed with ECU of FIG.

Explanation of symbols

2 Waste heat utilization device 4 Engine (internal combustion engine)
8 Rankine cycle circuit 9 Closed circuit 9a, 9d Flow path (High voltage circuit)
9b Flow path (low pressure circuit)
10 Evaporator 12 Expander 14 Condenser 16 Refrigerant Pump (Pump)
20 Bypass 26 Receiver tank (tank)
28 Pressure release path (pressure release means)
32 Recovery side solenoid valve (recovery valve)
34 Collection-side capillary tube (deceleration mechanism, capillary tube)
36 Supply side solenoid valve (supply valve)
38 Supply side capillary tube (deceleration mechanism, capillary tube)
48 High pressure path 50 Low pressure path 52 High pressure side solenoid valve (high pressure valve)
54 High-pressure side capillary tube (second reduction mechanism, capillary tube)
56 Low pressure side solenoid valve (low pressure valve)
58 Low pressure side capillary tube (second reduction mechanism, capillary tube)
60 Pressure sensor (internal pressure detection means)

Claims (7)

A waste heat utilization device for recovering heat from a heat medium of waste heat of an internal combustion engine,
An evaporator that heats the working fluid by exchanging heat with the heat medium, an expander that expands the working fluid via the evaporator to generate a driving force, a condenser that condenses the working fluid via the expander, A pump that pumps the working fluid that has passed through the condenser toward the evaporator, and forms a high-pressure circuit section in which the working fluid exhibits a high pressure from an outlet side of the pump to an inlet side of the expander; A closed circuit that forms a low-pressure circuit part in which the working fluid exhibits a low pressure from the outlet side of the condenser to the inlet side of the condenser;
A bypass path communicating the high pressure circuit section and the low pressure circuit section, bypassing the condenser and the pump;
A recovery valve that is provided in the vicinity of the high-pressure circuit portion of the bypass passage, and that recovers the liquid working fluid from the high-pressure circuit portion into the bypass passage by opening the valve;
A supply valve that is provided in the vicinity of the low-pressure circuit portion of the bypass passage, and supplies a liquid working fluid from the bypass passage to the low-pressure circuit portion by opening the valve;
A Rankine cycle circuit having a circulation flow rate control means for opening and closing the recovery valve and the supply valve according to the degree of supercooling of the working fluid passing through the condenser and controlling the amount of the working fluid circulating in the closed circuit. Prepared,
A waste heat utilization apparatus for an internal combustion engine, wherein a speed reduction mechanism for reducing a flow rate of the working fluid flowing out from the recovery valve and the supply valve is disposed in the bypass passage.   2. The waste heat utilization apparatus for an internal combustion engine according to claim 1, wherein the bypass passage includes a tank that temporarily stores the working fluid recovered by opening the recovery valve.   The waste heat utilization apparatus for an internal combustion engine according to claim 2, wherein the tank includes a depressurization unit that depressurizes the stored working fluid from the tank toward the high-pressure circuit unit.   The circulating flow rate control means opens and closes the recovery valve and the supply valve in order to keep the degree of supercooling at a predetermined minimum value within a range where cavitation of the pump can be avoided, and opens the closed circuit. The waste heat utilization apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the amount of circulating working fluid is controlled.   5. The Rankine cycle circuit comprises tank internal pressure control means for setting the internal pressure of the tank to an intermediate pressure that is lower than the high pressure circuit and higher than the low pressure circuit. A waste heat utilization apparatus for an internal combustion engine according to claim 1. The Rankine cycle circuit includes a high-pressure path that communicates the tank and the high-pressure circuit section, a low-pressure path that communicates the tank and the low-pressure circuit section, and a valve that opens the gaseous state from the high-pressure circuit section to the tank. A high-pressure valve for flowing the working fluid; and a low-pressure valve for opening the gaseous working fluid from the tank to the low-pressure circuit by opening the valve;
The tank internal pressure control means includes internal pressure detection means for detecting the internal pressure of the tank, and opens and closes the high pressure valve and the low pressure valve according to the internal pressure of the tank detected by the internal pressure detection means, The internal pressure is the intermediate pressure,
6. The internal combustion engine according to claim 5, wherein a second speed reduction mechanism for reducing a flow rate of the working fluid flowing out from the high pressure valve and the low pressure valve is disposed in the high pressure path and the low pressure path, respectively. Waste heat utilization equipment.   The waste heat utilization apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the speed reduction mechanism and the second speed reduction mechanism are capillary tubes.

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