Rankine Cycle

TECHNICAL FIELD

This invention relates to a Rankine cycle that recovers engine's waste heat as power.

BACKGROUND ART

A Rankine cycle includes a refrigerant pump that circulates a refrigerant, a waste heat recoverer that causes the refrigerant to recover engine's waste heat, an expander that converts the waste heat recovered in the refrigerant by expanding the refrigerant, and a condenser that condenses the refrigerant expanded by the expander. Power extracted by the expander is transmitted to an engine's output shaft and an electric power generator via a belt or the like.

When operation of the Rankine cycle stops, uneven existence of the refrigerant occurs due to an in-cycle temperature difference (pressure difference caused by evaporation or condensation of the refrigerant). At the time of starting operation of the Rankine cycle, it is important that a sufficient refrigerant in liquid phase be present in an inlet of the refrigerant pump. This is because the refrigerant pump is unable to send the refrigerant to a heat exchanger unless the sufficient refrigerant in liquid phase is present in the inlet of the refrigerant pump, and that lubricant oil is mixed in the refrigerant and if this oil is not present in the inlet of the refrigerant pump, the refrigerant pump cannot sufficiently be lubricated.

Accordingly, in JP 2005-337063 A, the input of the refrigerant pump is disposed below a fluid level in the condenser, whereby a sufficient refrigerant in liquid phase is present in the inlet of the refrigerant pump.

SUMMARY OF INVENTION

However, a Rankine system may be disposed in limited space in an engine room, so that a configuration in which the inlet of the refrigerant pump is below the fluid level in the condenser may not be employed . . . . In addition, even if this configuration is employed, depending on the temperature difference in the cycle and a downtime of the Rankine cycle, due to the uneven existence of the refrigerant, there is a possibility that the sufficient refrigerant in liquid phase may not be present in the inlet of the refrigerant pump.

It is an object of the present invention to eliminate lack of a refrigerant in liquid phase at the inlet of a refrigerant pump in a case where a Rankine cycle is operated.

According to a certain aspect of the present invention, a Rankine cycle includes a refrigerant pump that circulates a refrigerant, a heat exchanger that causes the refrigerant to recover engine's waste heat, an expander that converts the waste heat recovered in the refrigerant by expanding the refrigerant, and a condenser that condenses the refrigerant expanded by the expander. In addition, the Rankine cycle shares the condenser and the refrigerant with a refrigeration cycle of an air-conditioner. A refrigerant passage that connects to the outlet of the condenser branches at a branch point to connect to the refrigerant pump and an evaporator of a refrigeration cycle. In the case of operating the Rankine cycle, a compressor of the refrigeration cycle is driven without a request to operate the air-conditioner.

Embodiments and advantages of the present invention are described below in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of an integrated cycle.

FIG. 2A is a schematic sectional view of an expander pump in which a pump and an expander are incorporated.

FIG. 2B is a schematic sectional view of a refrigerant pump.

FIG. 2C is a schematic sectional view of an expander.

FIG. 3 is a schematic view illustrating a refrigerant valve system.

FIG. 4 is a schematic configuration view of a hybrid vehicle.

FIG. 5 is a schematic perspective view of an engine.

FIG. 6 is a schematic view of an engine configuration as viewed from the bottom of a vehicle.

FIG. 7A is a map illustrating a Rankine cycle operation region.

FIG. 7B is a map illustrating a Rankine cycle operation region.

FIG. 8 is a schematic diagram illustrating a specific disposition of a refrigerant passage connecting to a refrigerant pump.

FIG. 9 is a flowchart illustrating details of start-up control.

FIG. 10 is a table of a correction coefficient for correcting preparation time.

FIG. 11 is an explanatory diagram for illustrating the flow of a refrigerant during start-up control.

FIG. 12 is a flowchart illustrating details of refrigerant lack eliminating control (Second Embodiment).

DESCRIPTION OF EMBODIMENTS
First Embodiment

FIG. 1 illustrates a schematic diagram representing the entire system of a Rankine cycle 31 as a precondition of the present invention. The Rankine cycle 31 in FIG. 1 has a configuration in which it shares a refrigeration cycle 51, a refrigerant, and a condenser 38, and a cycle in which the Rankine cycle 31 and the refrigeration cycle 51 are integrated is hereinafter expressed as an integrated cycle 30. FIG. 4 is a schematic diagram of a hybrid vehicle 1 in which the integrated cycle 30 is installed. Note that the integrated cycle 30 refers to an entire system including circuits (passages) of cooling water and exhaust, or the like, in addition to the Rankine cycle 31, a circuit (passage) through which the refrigerant of the refrigeration cycle 51 circulates, and constituent elements, such as a pump, an expander, and a condenser, provided in therebetween.

In a hybrid vehicle 1, an engine 2, a motor generator 81, and an automatic transmission 82 are connected in series, and an output of the automatic transmission 82 is transmitted to drive wheels 85 via a propeller shaft 83 and a differential gear 84. Between the engine 2 and the motor generator 81 is provided a first drive shaft clutch 86. In addition, one of friction fastening elements of the automatic transmission 82 is configured as a second drive shaft clutch 87. The first drive shaft clutch 86 and the second drive shaft clutch 87 are connected to an engine controller 71, and in accordance with driving conditions of the hybrid vehicle, the connection/disconnection (connection state) is controlled. In the hybrid vehicle 1, as illustrated in FIG. 7B, in a case where a vehicle speed lies in an EV running region in which the engine 2 has bad efficiency, by stopping the engine 2, disconnecting the first drive shaft clutch 86, and connecting the second drive shaft clutch 87, only a driving force by the motor generator 81 causes the hybrid vehicle 1 to run. On the other hand, when the vehicle speed deviates from the EV running region to shift to a Rankine cycle operation region, by operating the engine 2, a Rankine cycle 31 (described below) is operated. The engine 2 is provided with an exhaust passage 3, and the exhaust passage 3 includes an exhaust manifold 4, and an exhaust pipe 5 connected to an assembly unit of the exhaust manifold 4. The exhaust pipe 5 branches to a bypass exhaust pipe 6. The exhaust pipe 5, which is bypassed to the bypass exhaust pipe 6, is provided with a waste heat recoverer 22 for performing heat exchange between exhaust and cooling water. As illustrated in FIG. 6, the waste heat recoverer 22 and the bypass exhaust pipe 6 are disposed, as a waste heat recovery unit 23 in which these are incorporated, between an underfloor catalyst 88 and a sub-muffler 89 downstream thereof.

On the basis of FIG. 1, at first, an engine cooling water circuit is described. Cooling water of approximately 80 to 90° C. exits the engine 2 flows separately on a cooling water passage 13 passing through a radiator 11 and on a bypass cooling water passage 14 bypassing the radiator 11. After that, the two flows join again at a thermostat valve 15 that determines allocations of the flow amounts of cooling water flowing in both passages 13 and 14, pass through a cooling water pump 16, and returns to the engine 2. The cooling water pump 16 is driven by the engine 2, and its rotational speed is in synchronization with the engine rotational speed. In a case where a cooling water temperature is high, the thermostat valve 15 enlarges a valve opening degree for the cooling water passage 13 to relatively increase the amount of cooling water passing through the radiator 11, and in a case where the cooling water temperature is low, the thermostat valve 15 reduces the valve opening degree for the cooling water passage 13 to relatively decrease the amount of cooling water passing through the radiator 11. Particularly, in a case where the cooling water temperature is low, such as in the case of location in the front of a warm-up unit of the engine 2, by completely bypassing the radiator 11, the total amount of cooling water is caused to flow on the side of the bypass cooling water passage 14. In addition, the valve opening degree for the bypass cooling water passage 14 is not totally opened. When the amount of cooling water flowing in the radiator 11 increases, the flow amount of cooling water flowing in the bypass cooling water passage 14 is lower than a case where the total amount of cooling water flows on the side of the bypass cooling water passage 14. However, the thermostat valve 15 is configured such that the flow is prevented from completely stopping. The bypass cooling water passage 14, which bypasses the radiator 11, includes a first bypass cooling water passage 24 that branches from the cooling water passage 13 to directly connect to a heat exchanger 36, which is described below, and a second bypass cooling water passage 25 that branches from the cooling water passage 13 to connect to the heat exchanger 36 via the waste heat recoverer 22.

The bypass cooling water passage 14 includes the heat exchanger 36, which performs heat exchange with the refrigerant of the Rankine cycle 31. The heat exchanger 36 is such that an evaporator and a superheater are integrated. In other words, in the heat exchanger 36, two cooling water passages 36a and 36b are provided substantially in a line, and a refrigerant passage 36c in which the refrigerant of the Rankine cycle 31 flows so as to enable heat exchange between the refrigerant and the cooling water is provided adjacently to the cooling water passages 36a and 36b. Further, the passages 36a, 36b, and 36c are configured such that the refrigerant of the Rankine cycle 31 and the cooling water are opposite in flow direction when the entire heat exchanger 36 is overviewed.

Specifically, one cooling water passage 36a, which is positioned upstream (left in FIG. 1) of the refrigerant of the Rankine cycle 31, is inserted in the first bypass cooling water passage 24. A heat exchanger left part that consists of the cooling water passage 36a and a refrigerant passage portion adjacent to the cooling water passage 36a is an evaporator for heating the refrigerant of the Rankine cycle 31 which flows in the refrigerant passage 36c by directly introducing the cooling water exits the engine 2 into the cooling water passage 36a.

Cooling water that passes through the waste heat recoverer 22 via the second bypass cooling water passage 25 is introduced into the other cooling water passage 36b, which is positioned downstream (right in FIG. 1) of the refrigerant of the Rankine cycle 31. A heat exchanger right part (the downstream side for the refrigerant of the Rankine cycle 31) that consists of the cooling water passage 36b and a refrigerant passage portion adjacent to the cooling water passage 36b is a superheater that superheats the refrigerant flowing in the refrigerant passage 36c by introducing, into the refrigerant passage 36b, cooling water obtained by further heating cooling water at the outlet of the engine 2 by using exhaust.

A cooling water passage 22a of the waste heat recoverer 22 is provided adjacently to the exhaust pipe 5. By introducing the cooling water at the outlet of the engine 2 into the cooling water passage 22a of the waste heat recoverer 22, the cooling water can be heated with high temperature exhaust to, for example, approximately 110 to 115° C. The cooling water passage 22a is configured such that the exhaust and the cooling water are opposite in flow direction when the entire waste heat recoverer 22 is overviewed.

A control valve 26 is inserted in the second bypass cooling water passage 25 provided with the waste heat recoverer 22. The control valve 26 is configured such that, when a detection temperature of a cooling water temperature sensor 74 at the outlet of the engine 2 is a predetermined value or higher, the opening degree of the control valve 26 is reduced so that an engine water temperature representing the temperature of cooling water inside the engine 2 is prevented from exceeding an allowable temperature (for example, 100° C.) for preventing efficiency deterioration of the engine 2 and knocking from occurring. Since the amount of cooling water flowing through the waste heat recoverer 22 is decreased when the engine water temperature approaches the allowable temperature, the engine water temperature can reliably be prevented from exceeding the allowable temperature.

In addition, in a case where a decrease in flow amount of the second bypass cooling water passage 25 excessively increases a cooling water temperature which is increased by the waste heat recoverer 22 to cause the cooling water to evaporate (boil), the flow of the cooling water in the cooling water passage gets worse to cause excessive increase in component temperature. In order to avoid this, the bypass exhaust pipe 6, which bypasses the waste heat recoverer 22, and a thermostat valve 7 that controls an exhaust passing amount of the waste heat recoverer 22 and an exhaust passing amount of the bypass exhaust pipe 6 are provided in a branch part of the bypass exhaust pipe 6. In other words, regarding the thermostat valve 7, its valve opening degree is adjusted on the basis of the temperature of cooling water exits the waste heat recoverer 22 so that the temperature of the cooling water exits the waste heat recoverer 22 is prevented from exceeding a predetermined temperature (for example, a boiling temperature of 120° C.).

The heat exchanger 36, the thermostat valve 7, and the waste heat recoverer 22 are integrated as the waste heat recovery unit 23, and are arranged in the middle of the exhaust pipe substantially in an underfloor center in a vehicle width direction. The thermostat valve 7 may be a relatively simplified thermostatic valve using a bimetal or the like, and may be a control valve that is controlled by a controller to which a temperature sensor output is input. Adjustment of heat exchange rate from exhaust by the thermostat valve 7 to the cooling water involves a relatively long delay. Thus, it is difficult to prevent the engine temperature from exceeding the allowable temperature when the thermostat valve 7 is independently adjusted. However, since the control valve 26 on the second bypass cooling water passage 25 is configured to be controlled on the basis of the engine temperature (outlet temperature), the engine water temperature can reliably be prevented from exceeding the allowable temperature by quickly decreasing a heat recovery amount. In addition, in a state in which the engine water temperature has a tolerance to the allowable temperature, by performing heat exchange until the temperature of cooling water exits the waste heat recoverer 22 increases to such a high temperature (for example, 110 to 115° C.) as to exceed the allowable temperature, the waste heat recovery amount can be increased. The cooling water exited the cooling water passage 36b jointly flows into the first bypass cooling water passage 24 via the second bypass cooling water passage 25.

When the temperature of cooling water from the cooling water passage 14 to the thermostat valve 15 is sufficiently decreased such that, for example, the heat exchanger 36 performs heat exchange with the refrigerant of the Rankine cycle 31, a valve opening degree of the thermostat valve 15 for the cooling water passage 13 is reduced to relatively decrease the amount of cooling water passing through the radiator 11. Conversely, the temperature of cooling water from the cooling water passage 14 to the thermostat valve 15 is increased by a state in which the Rankine cycle 31 is not being operated, or the like, a valve opening degree of the thermostat valve 15 for the cooling water passage 13 is enlarged to relatively increase the amount of cooling water passing through the radiator 11. A configuration is formed in which, on the above operation of the thermostat valve 15, the cooling water temperature of the engine 2 is properly maintained, so that heat is properly supplied to (recovered in) the Rankine cycle 31.

Next, the Rankine cycle 31 is described. Here, the Rankine cycle 31 is configured not as a simple Rankine cycle but as pan of the integrated cycle 30 integrated with the refrigeration cycle 51. The following firstly describes the Rankine cycle 31, which is a basis, and thereafter mentions the refrigeration cycle 51.

The Rankine cycle 31 is a system that causes the refrigerant to recover the waste heat of the engine 2 via the cooling water of the engine 2, and that regenerates the recovered waste heat as power. The Rankine cycle 31 includes a refrigerant pump 32, the heat exchanger 36 as a superheater, an expander 37, and the condenser 38. The respective constituent elements are connected by refrigerant passages 41 to 44 in which the refrigerant (R134a or the like) circulates.

The shaft of the refrigerant pump 32 is disposed to be coaxially connected to an output shaft of the expander 37. Output (power) generated by the expander 37 drives the refrigerant pump 32, and the generated power is supplied to the output shaft (crank shaft) of the engine 2 (see FIG. 2A). In other words, the shaft of the refrigerant pump 32 and the output shaft of the expander 37 are disposed in parallel to the output shaft of the engine 2. A belt 34 is stretched between a pump pulley 33 provided at a distal end of the refrigerant pump 32 and a crank pulley 2a (see FIG. 1). Note that a geared pump is employed as the refrigerant pump 32, and a scrolling expander is employed as the expander 37 (see FIG. 2B and FIG. 2C).

In addition, by providing an electromagnetic clutch (this clutch is hereinafter referred to as an “expander clutch”) 35 (first clutch) between the pump pulley 33 and the refrigerant pump 32, the refrigerant pump 32 and the expander 37 can be connected to or disconnected from the engine 2 (see FIG. 2A). Accordingly, in a case where output that is generated by the expander 37 exceeds the driving force of the refrigerant pump 32 and friction retained by a rotating body (in a case where predicted expander torque is positive), by connecting the clutch 35, the rotation of the engine output shaft can be assisted with the output that is generated by the expander 37. In this manner, by assisting the rotation of the engine output shaft by using energy obtained by waste heat recovery, fuel efficiency can be improved. Further, the energy to drive the refrigerant pump 32 that circulates the refrigerant can also be covered by waste heat recovered. The expander clutch 35 may be provided at any position if it is in the middle of a power transmission path from the engine 2 to the refrigerant pump 32 and the expander 37.

The refrigerant from the refrigerant pump 32 is supplied to the heat exchanger 36 via the refrigerant passage 41. The heat exchanger 36 is a heat exchanger that causes the cooling water of the engine 2 and the refrigerant to perform heat exchange therebetween, and that vaporizes and superheats the refrigerant.

The refrigerant from the heat exchanger 36 is supplied to the expander 37 via the refrigerant passage 42. The expander 37 is a steam turbine that converts the heat into rotational energy by expanding the vaporized and superheated refrigerant. The power recovered by the expander 37 drives the refrigerant pump 32, and is transmitted to the engine 2 via a belt transmission mechanism to assist the rotation of the engine 2.

The refrigerant from the expander 37 is supplied to the condenser 38 via the refrigerant passage 43. The condenser 38 is a heat exchanger that causes outside air and the refrigerant to perform heat exchange therebetween, and that cools and vaporizes the refrigerant. Accordingly, the condenser 38 and the radiator 11 are arranged in parallel, and are cooled by radiator fans 12.

The refrigerant liquefied by the condenser 38 is returned to the refrigerant pump 32 via the refrigerant passage 44. The refrigerant returned to the refrigerant pump 32 is sent to the heat exchanger 36 again by the refrigerant pump 32, and is circulated in the respective constituent elements of the Rankine cycle 31.

Note that the refrigerant passage 44 upwardly extends from the inlet of the refrigerant pump 32, as illustrated in FIG. 8.

Next, the refrigeration cycle 51 is described. Since the refrigeration cycle 51 shares the refrigerant that is circulated in the Rankine cycle 31, the refrigeration cycle 51 is integrated with the Rankine cycle 31, and the configuration of the refrigeration cycle 51, itself, is simplified. In other words, the refrigeration cycle 51 includes a compressor 52, the condenser 38, and an evaporator 55.

The compressor 52 is a fluid machine that compresses the refrigerant of the refrigeration cycle 51 to high temperature and pressure one, and is driven by the engine 2. In other words, as also illustrated in FIG. 4, a compressor pulley 53 is fixed to the drive shaft of the compressor 52, and the belt 34 is stretched between the compressor pulley 53 and the crank pulley 2a. The driving force of the engine 2 is transmitted to the compressor pulley 53 via the belt 34 to drive the compressor 52. In addition, by providing an electromagnetic dutch (this clutch is hereinafter referred to as a “compressor clutch”) 54 (second dutch) between the compressor pulley 53 and the compressor 52, the compressor 52 and the compressor pulley 53 can be connected to or disconnected from each other.

Returning to FIG. 1, after the refrigerant from the compressor 52 jointly flows into the refrigerant passage 43 via the refrigerant passage 56, the refrigerant is supplied to the condenser 38. The condenser 38 is a heat exchanger that condenses and liquefies the refrigerant by performing heat exchange with the outside air. The liquid refrigerant from the condenser 38 is supplied to the evaporator 55 via a refrigerant passage 57 branching from the refrigerant passage 44. The evaporator 55 is disposed in a casing of an air-conditioner unit similarly to a heater core, which is not shown. The evaporator 55 is a heat exchanger that evaporates the liquid refrigerant from the condenser 38, and that cools air-conditioned air from a blower fan by evaporation latent heat at that time.

The refrigerant evaporated by the evaporator 55 is returned to the compressor 52 via the refrigerant passage 58. Note that, regarding the air-conditioned air cooled by the evaporator 55 and the air-conditioned air heated by the heater core, their mixture ratio is changed in accordance with the opening degree of an air mix door so as to be adjusted to a temperature set by a crew.

Note that the evaporator 55, a part of the refrigerant passage 44, which connects the condenser 38 and the evaporator 55, and a refrigerant passage 57 are disposed in a position higher than the inlet of the refrigerant pump 32. In addition, the refrigerant passage 44 branches at a refrigeration branch point 45 to connect to the refrigerant passage 57 (see FIG. 8).

In the integrated cycle 30 consisting of the Rankine cycle 31 and the refrigeration cycle 51, in order to control the refrigerant flowing in the cycle, various valves are provided in the middle of the circuit, if required. For example, in order to control the refrigerant flowing in the Rankine cycle 31, the refrigerant passage 44, which connects the refrigeration branch point 45 and the refrigerant pump 32, is provided with a pump upstream valve 61, and the refrigerant passage 42, which connects the heat exchanger 36 and the expander 37, is provided with an expander upstream valve 62. In addition, the refrigerant passage 41, which connects the refrigerant pump 32 and the heat exchanger 36, is provided with a check valve 63 for preventing a backflow of the refrigerant from the heat exchanger 36 to the refrigerant pump 32. Also the refrigerant passage 43, which connects the expander 37 and a refrigeration cycle junction point 46, is provided with a check valve 64 for preventing a backflow of the refrigerant from the refrigeration cycle junction point 46 to the expander 37. In addition, an expander bypass passage 65 that bypasses the expander 37 from the upstream of an expander upstream valve 62 to join the upstream of the check valve 64 is provided. The expander bypass passage 65 is provided with a bypass valve 66. Further, a pressure adjusting valve 6 is provided on a passage 67 that bypasses a bypass valve 66. Also on the side of the refrigeration cycle 51, an air-conditioner circuit valve 69 is provided on the refrigerant passage 57, which connects the refrigeration branch point 45 and the evaporator 55.

The above four valves 61, 62, 66, and 69 are all electromagnetic on-off valves. An expander upstream pressure signal detected by a pressure sensor 72, a signal of a refrigerant pressure Pd at the outlet of the condenser 38, detected by a pressure sensor 73, a rotational speed signal of the expander 37 or the like, are input to the engine controller 71. The engine controller 71 controls the compressor 52 of the refrigeration cycle 51 and the radiator fans 12 on the basis of these input signals in accordance with predetermined operation conditions, and also controls opening and closing of the above four electromagnetic valves 61, 62, 66, and 69.

For example, on the basis of an expander upstream pressure and expander rotational speed detected by the pressure sensor 72, the expander torque (regenerative power) is predicted. When the predicted expander torque is positive (when the rotation of the engine output shaft can be assisted), the expander clutch 35 is fastened, and when the predicted expander torque is zero or negative, the expander clutch 35 is released. In the case based on the sensor detected pressure and the expander rotational speed, the expander torque can be predicted at high accuracy compared with the case of predicting the expander torque (regenerative power) from an exhaust temperature, and in response to a situation in which the expander torque occurs, fastening and release of the expander clutch 35 can appropriately be performed (for details, see 2010-190185 A).

The above four on-off valves 61, 62, 66, and 69, and the two check valves 63 and 64 are refrigerant system valves. Functions of these refrigerant system valves are illustrated in FIG. 3 again.

In FIG. 3, the pump upstream valve 61 is provided at the inlet of the refrigerant pump 32 (see FIG. 8). The pump upstream valve 61 is intended to be closed while, for example, the Rankine cycle 31 is stopped in a predetermined condition that, compared with the circuit of the refrigeration cycle 51, the refrigerant is likely to unevenly exist, such as termination of the Rankine cycle 31, whereby uneven existence of the refrigerant (including a lubricant component) to the Rankine cycle 31 is prevented. As described below, the pump upstream valve 61 cooperates with the check valve 64, which is downstream of the expander 37, to close the circuit of the Rankine cycle 31. The expander upstream valve 62 can maintain the refrigerant from the heat exchanger 36 until the refrigerant from the heat exchanger 36 has a high pressure by blocking the refrigerant passage 42 in a case where the refrigerant pressure from the heat exchanger 36 is relatively low. This urges heating the refrigerant even in a case where the expander torque is not sufficiently obtained, thereby making it possible to shorten, for example, a time to restarting (entering a state in which actual regeneration is performed) the Rankine cycle 31. The bypass valve 66 is intended to be opened to let the refrigerant pump 32 to operate after bypassing the expander 37 in a case such as when the amount of the refrigerant present on the side of the Rankine cycle 31 at the time of starting the Rankine cycle 31, whereby the startup time of the Rankine cycle 31 is shortened. When by operating the refrigerant pump 32 after bypassing the expander 37, a state is realized in which the refrigerant temperature at the outlet of the condenser 38 or the inlet of the refrigerant pump 32 is lower by a predetermined temperature difference (degree of subcooling SC) or greater from a boiling pressure at the part, it is said that the Rankine cycle 31 has a state in which sufficient liquid refrigerant is supplied.

The check valve 63, which is upstream of the heat exchanger 36 is intended to maintain the refrigerant supplied to the expander 37 at high pressure by cooperating with the bypass valve 66, the pressure adjusting valve 68, and the expander upstream valve 62. In a condition that the regeneration efficiency of the Rankine cycle is low, the operation of the Rankine cycle is stopped and the circuit is closed over adjacent intervals of the heat exchanger, whereby the Rankine cycle is configured to be quickly restarted using high pressure refrigerant, with the in-stop refrigerant pressure increased. The pressure adjusting valve 68 has a role as a relief valve to be opened to let off the excessively high refrigerant in a case where the pressure of the refrigerant supplied to the expander 37 becomes excessively high.

The check valve 64, which is downstream of the expander 37, is intended to prevent uneven existence of the refrigerant to the Rankine cycle 31 by cooperating with the above-described pump upstream valve 61. In case the engine 2 is not warmed up immediately after the start of driving the hybrid vehicle 1, the Rankine cycle 31 has a lower temperature than that of the refrigeration cycle 51, so that the refrigerant may unevenly exist on the side of the Rankine cycle 31. Although there is not so high possibility that the refrigerant may unevenly exist on the side of the Rankine cycle 31, cooling capability is most demanded because, for example, immediately after the start of driving the vehicle in summer, a situation occurs in which the vehicle inside needs to be quickly cooled. Thus, it is required to secure the refrigerant of the refrigeration cycle 51 by eliminating slight uneven existence of the refrigerant. Accordingly, that's why the check valve 64 for preventing uneven existence of the refrigerant to the Rankine cycle 31 is provided.

The compressor 52 does not have any structure of allowing the refrigerant to freely pass through it at the time of being stopped, and is able to prevent the refrigerant from unevenly existing toward the refrigeration cycle 51 by cooperating with the air-conditioner circuit valve 69. This is described. When the operation of the refrigeration cycle 51 stops, the refrigerant moves from the Rankine cycle 31, which has a relatively high temperature during steady operation, to the refrigeration cycle 51, so that the refrigerant, which circulates in the Rankine cycle 31, may be insufficient. In the refrigeration cycle 51, immediately after cooling stops, the temperature of the evaporator 55 is low, so that the refrigerant is likely to remain in the evaporator 55, which has a relatively large volume and a low temperature. In this case, by stopping driving of the compressor 52, movement of the refrigerant from the condenser 38 to the evaporator 55 is interrupted, and by closing the air-conditioner circuit valve 69, the refrigerant is prevented from unevenly existing toward the refrigeration cycle 51.

Next, FIG. 5 is a schematic perspective view of the engine 2 illustrating the package of the entire engine 2. What is characteristic in FIG. 5 is that the heat exchanger 36 is disposed vertically above the exhaust manifold 4. By disposing the heat exchanger 36 in space vertically above the exhaust manifold 4, installability of the Rankine cycle 31 into engine 2 is improved. In addition, the engine 2 is provided with a tension pulley 8.

Next, a basic operation method of the Rankine cycle 31 is described with reference to FIG. 7A and FIG. 7B.

First, FIG. 7A and FIG. 7B are operation region charts of the Rankine cycle 31. FIG. 7A illustrates an operation region of the Rankine cycle 31, with the horizontal axis as an outside air temperature, and the vertical axis as an engine water temperature (cooling water temperature). FIG. 7B illustrates an operation region of the Rankine cycle 31, with the horizontal axis as an engine rotational speed, and with the vertical axis as engine torque (engine load).

In any of FIG. 7A and FIG. 7B, the Rankine cycle 31 is operated when a predetermined condition is satisfied. In a case where both conditions are satisfied, the Rankine cycle 31 is operated. In FIG. 7A, in a low water temperature region in which the warm-up unit of the engine 2 is prioritized, and in a high outside air temperature region in which the load on the compressor 52 increases, the operation of the Rankine cycle 31 is stopped. In a warm-up unit mode having a low exhaust temperature and a had recovery efficiency, rather by not operating the Rankine cycle 31, the cooling water temperature is promptly increased. In a high outside air temperature time in which high cooling capability is required, by stopping the Rankine cycle 31, sufficient refrigerant and cooling capability of the condenser 38 are provided to the refrigeration cycle 51. In FIG. 78, because of the hybrid vehicle, in an EV wooing region and in a high rotational speed region in which the friction of the expander 37 increases, the operation of the Rankine cycle 31 is stopped. It is difficult for the expander 37 to have a highly efficient structure in which the expander 37 has less friction at all rotational speeds. Thus, in the case of FIG. 78, the expander 37 is configured (dimensional settings or the like, of respective portions of the expander 37 are set) so that it has small friction and a high efficiency in an engine rotational speed range in which the frequency of the operation is high.

Meanwhile, in the integrated cycle 30, in order to prevent uneven existence of the refrigerant (including a lubricant component) in the Rankine cycle 31 or the refrigeration cycle 51, the pump upstream valve 61 and the check valve 64, and the air-conditioner circuit valve 69 are provided (see FIG. 3). However, depending on the distribution state of the refrigerant at the time the Rankine cycle 31 stops, or the like, if all these valves are closed, the uneven existence during stop (ignition-off time) cannot be prevented. In addition, in a case where these valves are not dosed, in a process in which the temperature of the entire plant (integrated cycle) may decreases after the operation stops, there is a possibility that the distribution of the refrigerant may variously change. In particular, in order to start the operation of the Rankine cycle 31, it is important that sufficient refrigerant in liquid phase be prepared at the inlet of the refrigerant pump 32.

That sufficient refrigerant in liquid phase is prepared is a state in which refrigerant in predetermined state, necessary for operating the Rankine cycle 31, exists at the inlet of the refrigerant pump 32. Specifically, the inlet (or the outlet of the condenser 38) of the refrigerant pump 32 has a temperature with a decrement (degree of subcooling) from a boiling point, in consideration of a pressure in the field, equal to or more than a predetermined amount.

Accordingly, in the case of starting the operation of the Rankine cycle 31, start-time control, which is described below, is performed before operation start, whereby lack of refrigerant at the inlet of the refrigerant pump 32 is eliminated.

The start-time control is control in which, at the time of turning on the vehicle key, by causing the compressor 52 in the refrigeration cycle 51 to operate for predetermined preparation time without a request to operating the air-conditioner, the refrigerant in liquid phase exits the condenser 38 is preferentially supplied to the inlet of the refrigerant pump 32.

FIG. 9 is a flowchart illustrating details of the start-time control. This control is initiated at the time of turning on the vehicle key, and each process is repeatedly executed at short time intervals by the engine controller 71. In addition, both a termination flag and a timer that are used in this control are reset to 0 at the time of turning off the vehicle key.

First, the engine controller 71 determines the value of the termination flag (S1). In a case where this control is executed for the first time at the time of turning on the vehicle key, the termination flag is 0, and the process proceeds from S1 to S2.

In S2, the engine controller 71 sets a preparation time (driving time of the compressor 52).

The preparation time is a time necessary until sufficient refrigerant is prepared at the inlet of the refrigerant pump 32 after starting the driving of the compressor 52 in the refrigeration cycle 51. Specifically, in a case where the air-conditioner circuit valve 69 is provided and is dosed at the time of stop, in consideration of an (more or less) uneven existence amount of the refrigerant toward the refrigeration cycle 51 that can be generated during the operation of the integrated cycle, the time necessary until sufficient refrigerant is prepared at the inlet of the refrigerant pump 32 shall be a reference time. When the uneven existence amount immediately before stop can be estimated, a reference time at the time of next starting may be set on the basis of an estimated value. In addition, in the case of a system that does not include the air-conditioner circuit valve 69, in a case where the driving of the compressor 52 is started in a state in which sufficiently lone time elapses after turning off of the vehicle key, a time necessary until sufficient refrigerant is prepared at the inlet of the refrigerant pump 32 is used as a reference time. A value obtained by multiplying the reference time by a correction coefficient obtained by referring to the table illustrated in FIG. 10 may also be set as the preparation time.

In the table illustrated in FIG. 10, the correction coefficient is set by a time (hereinafter referred to as a “stop time”) until turning on of the key at this time after previously turning on the vehicle key. The correction coefficient is set to zero when the stop time is zero, is set to a value greater than 1 when the stop time is short, and is set to 1 when the stop time is sufficiently long (for example, equal to or longer than a time until the cooling water of the engine 2 reaches a normal temperature).

This is because, when the stop time is zero, the uneven existence of the refrigerant does not occur and the compressor 52 does not need to be driven in order to eliminate the uneven existence of the refrigerant.

In addition, this is because, since the cooling water temperature of the engine 2 is high in a case where the stop time is short, evaporation of the refrigerant in the heat exchanger 36 moves the refrigerant on the side of the Rankine cycle 31 toward the refrigeration cycle 51, resulting in large uneven existence of the refrigerant.

In addition, this is because, in a case where the stop time is sufficiently long, a decrease in temperature of the cooling water of the engine 2 involves a decrease in temperature of the Rankine cycle 31, and part of the refrigerant on the side of the refrigeration cycle 51 returns to the Rankine cycle 31, thus reaching a certain uneven existence state.

Next, the engine controller 71 determines whether the timer indicates the preparation time or longer (S3). In a case where this process is executed for the first time at the time of turning on the vehicle key, the timer indicates 0, and the process proceeds from S3 to S4.

In S4, the engine controller 71 closes the air-conditioner circuit valve 69 and starts driving of the compressor 52. In addition, the engine controller 71 starts counting up the timer. By driving the compressor 52 in a state with the air-conditioner circuit valve 69 closed, the refrigerant in liquid phase extracted from the evaporator 55 or extruded from the condenser 38 is preferentially supplied to the inlet of the refrigerant pump 32 through the refrigerant passage 44.

Next, the engine controller 71 determines whether it is required to operate the air-conditioner (S5). Whether it is requested to operate the air-conditioner is determined on the basis of a signal from a controller of the air-conditioner.

The engine controller 71 allows the operation of the blower fan in a case where it is requested to operate the air-conditioner (S6), and inhibits the operation of the blower fan in a case where it is not requested to operate the air-conditioner (S7). This is to suppress the crew's uncomfortable or unreasonable feeling caused such that the blower fan is being operated in a situation in which it is not requested to operate the air-conditioner.

The engine controller 71 repeatedly executes processing from S1 through S7 until the timer indicates the preparation time or longer.

After that, when the timer indicates the preparation time or longer, the process proceeds from S3 to S8, and the engine controller 71 sets 1 to the termination flag to allow the operation of the Rankine cycle 31. In this state, sufficient refrigerant in liquid phase is prepared at the inlet of the refrigerant pump 32. After that, if the operation condition (FIG. 7A and FIG. 7B) of the Rankine cycle 31 holds, the operation of the Rankine cycle 31 is started.

Subsequently, the engine controller 71 determines whether the air-conditioner circuit valve 69 determines whether the air-conditioner circuit valve 69 is open (S9). In a case where the air-conditioner circuit valve 69 is closed, the air-conditioner circuit valve 69 opens the air-conditioner circuit valve 69 at the time it is requested to operate the air-conditioner (S10, S11).

Subsequently, operation and advantages of a first embodiment are described.

In the first embodiment, before starting the operation of the Rankine cycle 31, the start-time control is configured to be performed in which without a request to operate the air-conditioner, the compressor 52 in the refrigeration cycle 51 is driven (S4). By driving the compressor 52, the refrigerant is supplied to the inlet of the refrigerant pump 32, so that sufficient refrigerant in liquid phase can be prepared at the inlet of the refrigerant pump 32. This makes is possible to reliably start the Rankine cycle 31 in a short time, and since the refrigerant contains a lubricant component, it is ensured that the refrigerant pump 32 is also lubricated.

In the start-time control, the air-conditioner circuit valve 69 is configured to be closed while at least the compressor 52 is being driven (S4). This causes the refrigerant exits the condenser 38 to be preferentially predetermined to the inlet of the refrigerant pump 32, as indicated by an arrow in FIG. 11, so that, compared with a case where the air-conditioner circuit valve 69 is not closed, the lack of the refrigerant at the inlet of the refrigerant pump 32 can be eliminated in a shorter time.

Note that although the air-conditioner circuit valve 69 is closed under the start-time control, the opening degree of the air-conditioner circuit valve 69 may only be decreased as or than predetermined (the refrigerant sent to the refrigeration cycle is suppressed). Even in this case, refrigerant exits the condenser 38 is preferentially supplied to the inlet of the refrigerant pump 32, whereby the above advantages are expected.

In addition, the operation of only the Rankine cycle 31 gradually moves the refrigerant toward the refrigeration cycle 51, causing the refrigerant to be insufficient in the Rankine cycle 31, so that the output of the Rankine cycle 31 decreases. However, since the air-conditioner circuit valve 69 is closed (or the opening degree decreased) until the air-conditioner is operated, that is, until the refrigeration cycle 51 is operated (S9 to S11), transfer of the refrigerant toward the refrigeration cycle 51 is suppressed, and a decrease in output of the Rankine cycle 31 can be decreased.

Also, in addition to the above start-time control, the evaporator 55 are disposed at a position above the refrigerant pump 32, and refrigerant passages (part of the refrigerant passage 44 and the refrigerant passage 57) from the condenser 38 to the evaporator 55 are disposed at a position above the inlet of the refrigerant pump 32 (FIG. 8). According to this configuration, when the compressor 52 is driven, the refrigerant can easily be supplied to the inlet of the refrigerant pump 32.

In addition, the refrigerant passage 44 that connects to the inlet of the refrigerant pump 32 extends upward from the inlet of the refrigerant pump 32, and the inlet of the refrigerant pump 32 is provided with the pump upstream valve 61 that is closed during stopping the Rankine cycle 31 (FIG. 8). According to this configuration, even after the compressor 52 stops, the refrigerant remains above the pump upstream valve 61, and the refrigerant remains when the compressor 52 is driven. This refrigerant is supplied to the refrigerant pump 32 at the time of operating the Rankine cycle 31. Thus, lack of the refrigerant and lubricant inferior in the refrigerant pump 32 can be more suppressed.

In addition, in the start-time control, the blower fan of the air-conditioner is configured to be stopped when it is not requested to operate the air-conditioner (S7). This can suppress uncomfortable or unreasonable feeling caused by operating the blower fan despite that it is not requested to operate the air-conditioner.

In addition, the driving time (the preparation time in S2) of the compressor 52 in the start-time control is configured to be set in accordance with a time (vehicle stop time until presently turning on the key after turning off the vehicle key. Since the degree of the uneven existence of the refrigerant in the Rankine cycle 31 differs depending on the vehicle stop time, by setting the driving time of the compressor 52 in accordance with the vehicle stop time, the supply amount of the refrigerant to the inlet of the refrigerant pump 32 can be prevented from becoming excessive or insufficient.

Note that, since there is a possibility that a compressor inhale refrigerant pressure may become negative when the compressor 52 is operated in a state in which the air-conditioner circuit valve 69, which is before the evaporator 55, is closed, it is preferable that the driving time of the compressor 52 be a short time. When there is a possibility that a compressor inhale refrigerant pressure may become negative, the driving of the compressor 52 may be stopped. In addition, when the compressor 52 is driven in a state in which the blower fan is stopped, there is a possibility that a refrigerant which is not evaporated by the evaporator 55 may be inhaled by the compressor 52. Thus, even if there is such a possibility, the driving of the compressor 52 may be stopped. In addition, since the compressor 52 is driven by the engine 2, when the engine rotational speed at the time of temporarily driving the compressor 52 is a relatively high rotational speed, these problems are highly likely to occur. Thus, as the start-time control, in a case where the compressor 52 is driven when it is not requested to operate the air-conditioner, as the rotational speed of the compressor 52 is higher, the driving time of the compressor 52 may be reduced.

Second Embodiment

A second embodiment is identical to the first embodiment in configuration of the Rankine cycle 31, but is different from the first embodiment in control details of the engine controller 71. Specifically, in the second embodiment, by performing refrigerant lack eliminating control, which is described below, instead of the above start-time control, in the case of operating the Rankine cycle 31, lack of the refrigerant in liquid phase at the inlet of the refrigerant pump 32 is configured to be eliminated.

The refrigerant lack eliminating control is control in which, by driving the compressor 52 in the refrigeration cycle 51 for a predetermined preparation time simultaneously with the start of driving the Rankine cycle 31 if it is not requested to operate the air-conditioner, the refrigerant in liquid phase exits the condenser 38 is preferentially supplied to the inlet of the refrigerant pump 32.

FIG. 12 is a flowchart illustrating details of the refrigerant lack eliminating control. This control is started in a case where the operation conditions (FIG. 7A and FIG. 78) of the Rankine cycle 31 hold, and each process is repeatedly executed at predetermined short time intervals by the engine controller 71. In addition, the RC operation-finished flag and time that are used in this control are all reset to 0 at the time of overcoming the lack of the refrigerant in liquid phase at the inlet of the refrigerant pump 32.

First, the engine controller 71 determines the value of the RC operation-finished flag (S21). The RC operation-finished flag is a flag that is set to 1 in a case where the Rankine cycle 31 is operated even once after turning on the vehicle key. In a case where the Rankine cycle 31 is operated for the first time after turning on the vehicle key, the RC operation-finished flag is 0, and the process proceeds from S21 to S22.

In S22, the engine controller 71 sets the preparation time (the driving time of the compressor 52). The preparation time is a time necessary until the lack of the refrigerant at the inlet of the refrigerant pump 32 is eliminated after starting the driving of the compressor 52 in the refrigeration cycle 51. The preparation time is set on the basis of the stop time of the vehicle performed before starting the driving of the Rankine cycle similarly to the processing in S2 of FIG. 9, or of the like. However, since in the second embodiment, the compressor 52 is driven while the Rankine cycle 31 is being operated, the preparation time and the correction coefficient for use in setting the preparation time have values different from those in the first embodiment.

In S23, the engine controller 71 determines whether the timer indicates the preparation time or longer. In a case where the Rankine cycle 31 is operated for the first time after turning on the vehicle key, the timer indicates 0, and the process proceeds from S23 to S24.

In S24, the engine controller 71 starts the driving of the Rankine cycle 31, closes the sir-conditioner circuit valve 69, and starts the driving of the compressor 52. In other words, the operation of the Rankine cycle 31 and the driving of the refrigerant pump 32 are simultaneously started. In addition; the engine controller 71 starts counting-up of the timer.

By driving the compressor 52 in a state with the air-conditioner circuit valve 69 closed, the refrigerant in liquid phase extracted from the evaporator 55 or extruded from the condenser 38 is preferentially supplied to the inlet of the refrigerant pump 32 through the refrigerant passage 44. Due to this, the lack of the refrigerant at the inlet of the refrigerant pump 32 rapidly proceeds to solution.

Although in S24, the air-conditioner circuit valve 69 is closed, the opening degree may only be decreased as or than predetermined. Even in such a case, the refrigerant exits the condenser 38 can preferentially be supplied to the inlet of the refrigerant pump 32.

In S25, the engine controller 71 determines whether it is requested to operate the air-conditioner. Whether it is requested to operate the air-conditioner is determined on the basis of for example, a signal from the controller of the air-conditioner.

The engine controller 71 allows the driving of the blower fan in a case where it is requested to operate the air-conditioner (S26), and inhibits the driving of the blower fan so as not to give uncomfortable or unreasonable feeling to the crew in a case where it is not requested (S27).

The engine controller 71 repeatedly executes processing from S21 to S27 until the timer indicates the preparation time or longer.

After that, when the timer indicates the preparation time or longer, the process proceeds from S23 to S28, the engine controller 71 sets 1 to the RC operation-finished flag, and resets the timer.

When 1 is set to the RC operation-finished flag, after that, the process can flow from S21 to RETRUN, so that the driving of the compressor 52 by the refrigerant lack eliminating control is not performed. This is because when the Rankine cycle 31 is operated even once, the lack of the refrigerant in liquid phase at the inlet of the refrigerant pump 32 is eliminated.

After that, the air-conditioner is separately controlled by the controller of the air-conditioner, and if it is requested to operate the air-conditioner, the air-conditioner circuit valve 69 is opened to drive the compressor 52.

Subsequently, operation and advantages of the second embodiment are described.

The second embodiment is configured such that in a case where the Rankine cycle 31 is operated, the refrigerant lack eliminating control is performed in which without a request to operate the air-conditioner, the compressor 52 in the refrigeration cycle 51 is driven (S24). Since the driving of the compressor 52 is started simultaneously with the start of operating the Rankine cycle 31, the lack of the refrigerant in liquid phase at the inlet of the refrigerant pump 32 can rapidly be eliminated.

Since the time in which the refrigerant in liquid phase lacks at the inlet of the refrigerant pump 32 is a short time, a decrease in output of the Rankine cycle 31, caused by the lack of the refrigerant in liquid phase, and the lubricant lack of the refrigerant pump 32 do not become problems.

Description of the other operation and advantages is omitted since they are identical to the operation and advantages of the first embodiment.

Note that also in the second embodiment, similarly to the first embodiment, when there is a possibility that the compressor inhale refrigerant pressure may become negative by driving the compressor 52, or when there is a possibility that a refrigerant which is not evaporated by the evaporator 55 during stop of the blower fan may be inhaled by the compressor 52, the driving of the compressor 52 may be stopped. In addition, as the rotational speed of the compressor 52 is higher, the driving time the preparation time in S22) of the compressor 52 may be reduced.

Although the foregoing has described embodiments of the present invention, the above embodiments represent examples of application of the present invention, and it is not intended that the technical scope of the present invention is limited to specific configurations of the above embodiments.

For example, in each embodiment above, the driving of the compressor 52 is started before starting the driving of the Rankine cycle 31 at the time of turning on the vehicle key (first embodiment), or the driving of the compressor 52 is started simultaneously with the start of operating the Rankine cycle 31 (second embodiment). However, a driving start time of the compressor 52 is not limited thereto.

For example, it is determined whether the refrigerant in liquid phase is insufficient at the inlet of the refrigerant pump 32, and in a case where it is insufficient, the compressor 52 may be driven without a request to operate the air-conditioner. Whether the refrigerant in liquid phase is insufficient at the inlet of the refrigerant pump 32 is determined on the basis of, for example, an elapse time from the previous operation stop of the Rankine cycle 31. In this ease, while the Rankine cycle 31 is being stopped, the compressor 52 is periodically driven. This modification is included in the technical scope of the present invention.

The present invention claims priority based on Japanese Patent Application No. 2011-216747 filed in the Japan Patent Office on Sep. 30, 2011, and all the contents of this application are incorporated in this specification by reference.

Rankine Cycle

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