Fluid machine, rankine circuit, and system for utilizing waste heat from vehicle

A system for utilizing waste heat from a vehicle has a Rankine circuit, and the Rankine circuit includes a fluid machine. A generating unit of the fluid machine has a third rotating body that is disposed coaxially with a first rotating body of a pump unit and a second rotating body of an expansion unit. The fluid machine has a drive shaft that is integrally connected at least to the first rotating body, among the first, second and third rotating bodies, and a power transmission unit that is connected to the drive shaft and transmits external power to the drive shaft.

RELATED APPLICATIONS

This is a U.S. National Phase Application under 35 USC §371 of International Application PCT/JP2008/057899 filed on Apr. 24, 2008.

This application claims the priority of Japanese Patent Application No. 2007-118627 filed Apr. 27, 2007, the entire content of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a fluid machine, a Rankine circuit, and a system for utilizing waste heat from a vehicle.

BACKGROUND ART

A Rankine circuit constructing a system for utilizing waste heat of an inner combustion engine, such as a vehicle engine, has a circulation path through which a working fluid (heat medium) circulates. A pump, an evaporator (heat exchanger), an expansion machine, and a condenser are interposed in the circulation path in the order named.

The pump is driven, for example, by an electric motor to circulate the working fluid. The working fluid receives waste heat when passing through the evaporator, and is expanded in the expansion machine. In this process, the thermal energy of the working fluid is converted into torque and outputted outside. The thermal energy is thus used, for example, to rotate a fan for air-cooling the condenser.

As a compact and inexpensive fluid machine that is suitable for the Rankine circuit, Unexamined Japanese Patent Publication No. 2005-30386 discloses a fluid machine in which a pump, an expansion machine and a motor have a single drive shaft in common. In the fluid machine, the pump is started by the motor being activated upon receipt of external power. The working fluid circulates in response to the start of the pump, and the working fluid that has received heat energy is expanded in the expansion machine. After the motor is activated, the power supply to the motor is stopped. The pump is operated by the torque outputted from the expansion machine, and the motor is caused to function as a generator.

According to the fluid machine disclosed in Publication No. 2005-30386, since the motor that produces a rotational driving force is equipped with a function of generating electric power, the power generation efficiency of the motor is lower than that of a generator having only the power-generating function.

The fluid machine disclosed in Publication No. 2005-30386 utilizes a DC motor. In general, a DC motor has larger weight than an AC motor, and has lower power generation efficiency when being used as a generator. In addition, the DC motor needs to be maintained by brushing.

Furthermore, according to the fluid machine described in Publication No. 2005-30386, the heat energy recovered by the expansion machine, that is, the torque produced in the expansion machine, is once converted into electric power. The recovered heat energy cannot be outputted to the outside as torque.

DISCLOSURE OF THE INVENTION

It is an object of the invention to provide a compact fluid machine having not only an expansion unit and a pump unit but a generating unit capable of generating power with high efficiency, a Rankine circuit using the fluid machine, and a system for utilizing waste heat from a vehicle.

In order to achieve the object, the invention provides a fluid machine having a pump unit that includes a first rotating body, draws in a working fluid along with rotation of the first rotating body, and pressurizes and then discharges the working fluid that has been drawn in; an expansion unit that includes a second rotating body, receives the working fluid along with rotation of the second rotating body, and expands and then delivers out the working fluid that has been received; a generating unit that includes a third rotating body disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected at least to the first rotating body, among the first, second and third rotating bodies; and a power transmission unit that is connected to the drive shaft and transmits external power to the drive shaft.

In the fluid machine of the invention, the pump unit, the expansion unit, and the first, second and third rotating bodies of the generating unit are coaxially disposed, which makes it possible to downsize the fluid machine.

In this fluid machine, the drive shaft and the first rotating body of the pump unit are at least integrally connected to each other, and the power transmission unit that transmits the external power is connected to the drive shaft. The pump unit can therefore be started by using the external power. Accordingly, the generating unit is not required to function as an electric motor. For that reason, in this fluid machine, the generating unit is constructed to achieve high power generation efficiency, and therefore generates power with high efficiency.

This fluid machine is capable of outputting the torque, which is produced in the expansion unit, to the outside through the power transmission unit.

Preferably, the power transmission unit is an electromagnetic clutch that intermittently transmits the external power to the drive shaft. In the fluid machine according to a preferable aspect, disengagement of the electromagnetic clutch reduces the load of a power source that supplies power to the fluid machine.

Preferably, the generating unit generates an alternating current. In the fluid machine according to a preferable aspect, since the generating unit generates the alternating current, comparing with a DC motor, the generating unit is light in weight, has high power generation efficiency, and is easy to be maintained due to the lack of need for a brush.

Preferably, the drive shaft is integrally connected to the first, second and third rotating bodies. In the fluid machine according to a preferable aspect, since the first, second and third rotating bodies are integrally connected to the drive shaft, it is possible to simultaneously operate the pump unit, the expansion unit and the generating unit with a simple configuration.

Preferably, the expansion unit has a variable capacity. In the fluid machine according to a preferable aspect, since the expansion unit has the variable capacity, the capacity of the expansion unit can be adjusted to optimum according to the situation. For instance, immediately after the fluid machine is activated, the capacity of the expansion unit is reduced to prevent the working fluid from being expanded. This alleviates the load on the drive shaft, and reduces the consumed power of the fluid machine.

Preferably, the drive shaft is integrally connected to the first and third rotating bodies, whereas the drive shaft and the second rotating body are connected to each other through a connector. When rotational frequency of the second rotating body is lower than that of the drive shaft, the connector blocks the power transmission between the second rotating body and the drive shaft. When the rotational frequency of the second rotating body is about to get higher than that of the drive shaft, the connector allows the power transmission from the second rotating body to the drive shaft.

In the fluid machine according to a preferable aspect, when the rotational frequency of the second rotating body of the expansion unit is lower than that of the drive shaft, the connector blocks the power transmission between the second rotating body and the drive shaft, whereby the load on the drive shaft is alleviated, and the consumed power of the fluid machine is reduced.

When the rotational frequency of the second rotating body is higher than that of the drive shaft, the connector allows the power transmission from the second rotating body to the drive shaft, whereby the torque produced in the expansion unit is transmitted to the drive shaft. The torque transmitted to the drive shaft is not only converted into electric power by the generating unit but is also used as power for the pump unit. For that reason, if the torque produced in the expansion unit is sufficiently high, the fluid machine can operate independently without receiving external power. Furthermore, the torque produced in the expansion unit can be outputted to the outside through the power transmission unit.

Preferably, the fluid machine further has pump bypass means for reducing the work of the pump unit. In the fluid machine according to a preferable aspect, the pump bypass means reduces the work of the pump unit, whereby the power inputted from the outside can be preferentially used for power generation in the generating unit. Furthermore, the fluid machine can be utilized only as a generator according to the situation, which eliminates the need for an external generator.

Preferably, the drive shaft and the first rotating body are integrally connected to each other, whereas the drive shaft is connected to the second and third rotating bodies through a connector. When rotational frequencies of the second and third rotating bodies are lower than that of the drive shaft, the connector blocks the power transmission between the second and third rotating bodies and the drive shaft. When the rotational frequencies of the second and third rotating bodies are about to get higher than that of the drive shaft, the connector allows the power transmission from the second and third rotating bodies to the drive shaft.

In the fluid machine according to a preferable aspect, when the rotational frequency of the second rotating body of the expansion unit is lower than that of the drive shaft, the connector blocks the power transmission between the second and third rotating bodies and the drive shaft, whereby the load on the drive shaft is alleviated, and the consumed power of the fluid machine is reduced.

The torque produced in the expansion unit is not only converted into electric power by the generating unit but also transmitted through the connector to the drive shaft when the rotational frequencies of the second and third rotating bodies are higher than that of the drive shaft. The torque transmitted to the drive shaft is used as power for the pump unit. If this torque is sufficiently high, the fluid machine can operate independently without receiving external power. Furthermore, the torque produced in the expansion unit can be outputted to the outside through the power transmission unit.

Preferably, the generating unit has a field coil, and an electric generating capacity of the generating unit can be varied by adjusting the amount of current applied to the field coil. In the fluid machine according to a preferable aspect, since the electric generating capacity is variable, the electric generating capacity can be adjusted to optimum according to the situation.

Another invention provides a Rankine circuit having a fluid machine, a heater, and a condenser, which are interposed in a circulation path for circulating a heat medium. The fluid machine is provided with the Rankine circuit including a pump unit that includes a first rotating body, draws in a working fluid along with rotation of the first rotating body, and pressurizes and then discharges the working fluid that has been drawn in; an expansion unit that includes a second rotating body, receives the working fluid, expands and delivers out the received working fluid along with rotation of the second rotating body; a generating unit that includes a third rotating body disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected to the first and third rotating bodies; a power transmission unit that is connected to the drive shaft and transmits external power to the drive shaft; and a connector that connects the drive shaft and the second rotating body to each other, the connector that blocks power transmission between the second rotating body and the drive shaft when rotational frequency of the second rotating body is lower than that of the drive shaft, and allows power transmission from the second rotating body to the drive shaft when the rotational frequency of the second rotating body is about to get higher than that of the drive shaft.

The Rankine circuit according to another invention has a simple configuration because a single fluid machine functions as a pump, a generator, and an expansion unit.

In the Rankine circuit, after the pump unit is started by external power, while the rotational frequency of the second rotating body of the expansion unit is lower than that of the drive shaft, the connector blocks the power transmission between the second rotating body and the drive shaft. During a given duration from a time point when the pump unit is started, the load on the drive shaft is alleviated, and the consumed power of the fluid machine is reduced.

When the rotational frequency of the second rotating body is higher than that of the drive shaft, the connector allows the power transmission from the second rotating body to the drive shaft, whereby the torque produced in the expansion unit is transmitted to the drive shaft. The torque transmitted to the drive shaft is not only converted into electric power by the generating unit but also used as power for the pump unit. For that reason, if the torque produced in the expansion unit is sufficiently high, the fluid machine can operate independently without receiving external power. Furthermore, the torque produced in the expansion unit can be outputted to the outside through the power transmission unit.

Preferably, the Rankine circuit further includes a check valve that is interposed in a section of the circulation path, which extends between the pump unit of the fluid machine and the heater, and a circulation-path on-off valve that is interposed in a section of the circulation path, which extends between the heater and the expansion unit of the fluid machine.

In the Rankine circuit according to a preferable aspect, when the circulation-path on-off valve is closed, the external power is accumulated as pressure energy in a section of the circulation path, which extends from the check valve to the circulation-path on-off valve. When the circulation-path on-off valve is opened, the accumulated pressure energy is converted into torque in the expansion unit, and then converted into electric power in the generating unit. In short, the Rankine circuit accumulates the external power in a form other than electric power according to the situation.

Preferably, the generating unit has a field coil, and an electric generating capacity of the generating unit can be varied by adjusting the amount of current applied to the field coil.

In the Rankine circuit according to a preferable aspect, since the electric generating capacity is variable, the electric generating capacity can be adjusted to optimum according to the situation. For example, in this Rankine circuit, the external power or the torque produced in the expansion unit is convertible into electric power in the generating unit. If the external power or torque is sufficient, the electric generating capacity is increased. If not, the electric generating capacity is reduced, whereby the external power or the torque is effectively used. Alternatively, if the electric generating capacity is reduced when the external power is converted into pressure, the external power is preferentially converted into pressure.

Preferably, the Rankine circuit further includes pump bypass means for reducing the work of the pump unit.

In the Rankine circuit according to a preferable aspect, the pump bypass means reduces the work of the pump unit, whereby the power inputted from the outside can be preferentially used for power generation in the generating unit. To put it differently, the fluid machine can be utilized only as a generator according to the situation, which eliminates the need for an external generator.

Another invention provides a Rankine circuit having a fluid machine, a heater, and a condenser, which are interposed in a circulation path for circulating a heat medium. The fluid machine has a pump unit that includes a first rotating body, draws in a working fluid along with rotation of the first rotating body, and pressurizes and then discharges the working fluid that has been drawn in; an expansion unit that includes a second rotating body, receives the working fluid along with rotation of the second rotating body, and expands and delivers out the received working fluid; a generating unit that includes a third rotating body disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected to the first rotating body; and a power transmission unit that is connected to the drive shaft and transmits external power to the drive shaft, a connector that connects the drive shaft to the second and third rotating bodies, the connector that blocks power transmission between the second and third rotating bodies and the drive shaft when rotational frequencies of the second and third rotating bodies are lower than that of the drive shaft, and allows power transmission from the second and third rotating bodies to the drive shaft when the rotational frequencies of the second and third rotating bodies are about to get higher than that of the drive shaft.

The Rankine circuit according to another invention has a simple configuration because a single fluid machine functions as a pump, a generator, and an expansion unit.

In the Rankine circuit, after the pump unit is started by external power, while the rotational frequency of the second rotating body of the expansion unit is lower than that of the drive shaft, the connector blocks the power transmission between the second and third rotating bodies and the drive shaft. During a given duration from a time point when the pump unit is started, the load on the drive shaft is alleviated, and the consumed power of the fluid machine is reduced.

The torque produced in the expansion unit is not only converted into electric power by the generating unit but also transmitted through the connector to the drive shaft when the rotational frequencies of the second and third rotating bodies are higher than that of the drive shaft. The torque transmitted to the drive shaft is used as power for the pump unit. If this torque is sufficiently high, the fluid machine can operate independently without receiving external power. Furthermore, the torque produced in the expansion unit can be outputted to the outside through the power transmission unit.

Preferably, the Rankine circuit further includes a check valve that is interposed in the section of the circulation path, which extends between the pump unit of the fluid machine and the heater, and a circulation-path on-off valve that is interposed in a section of the circulation path, which extends between the heater and the expansion unit of the fluid machine.

In the Rankine circuit according to a preferable aspect, when the circulation-path on-off valve is closed, the external power is accumulated as pressure energy in a section of the circulation path, which extends from the check valve to the circulation-path on-off valve. When the circulation-path on-off valve is opened, the accumulated pressure energy is converted into torque in the expansion unit, and then converted into electric power in the generating unit. In short, the Rankine circuit accumulates the external power in a form other than electric power according to the situation.

Another invention provides a Rankine circuit having a fluid machine, a heater, and a condenser, which are interposed in a circulation path for circulating a heat medium. The fluid machine has a pump unit that includes a first rotating body, draws in a working fluid along with rotation of the first rotating body, and pressurizes and then discharges the working fluid that has been drawn in; an expansion unit that includes a second rotating body, receives the working fluid along with rotation of the second rotating body, and expands and then delivers out the received working fluid; a generating unit that includes a third rotating body disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected to the first, second and third rotating bodies; and a power transmission unit that is connected to the drive shaft and transmits external power to the drive shaft.

The Rankine circuit according to another invention has a simple configuration because a single fluid machine functions as a pump, a generator, and an expansion unit.

Preferably, the Rankine circuit further includes a check valve that is interposed in a section of the circulation path, which extends between the pump unit of the fluid machine and the heater; a circulation-path on-off valve that is interposed in a section of the circulation path, which extends between the heater and the expansion unit of the fluid machine; and pressure-reduction preventing means for preventing a pressure drop in a section of the circulation path, which extends between the circulation-path on-off valve and the expansion unit along with the rotation of the second rotating body when the circulation-path on-off valve is closed.

Preferably, in the Rankine circuit according to a preferable aspect, the external power is accumulated as pressure energy in the section of the circulation path, which extends from the check valve to the circulation-path on-off valve. When the circulation-path on-off valve is opened, the accumulated pressure energy is converted into torque in the expansion unit, and then converted into electric power in the generating unit. In short, the Rankine circuit is capable of storing the external power in a form other than electric power according to the situation.

At the same time, when the circulation-path on-off valve is closed, if the pressure-reduction preventing means prevents a pressure drop in the section of the circulation path, which extends between the circulation-path on-off valve and the expansion unit, the expansion unit does not operate in a state like a vacuum pump. For that reason, even if the circulation-path on-off valve is closed, the consumed power of the expansion unit is suppressed from being increased, and the external power is preferentially converted into pressure and then accumulated.

Preferably, the pressure-reduction preventing means has an external return path that is interposed in the circulation path in parallel with the expansion unit, and a return-path on-off valve that opens/closes the external return path.

In the Rankine circuit according to a preferable aspect, the pressure preventing means has a simple configuration.

Preferably, the pressure-reduction preventing means has an internal return path that is disposed in the expansion unit of the fluid machine and sends to an upstream side the heat medium that is being expanded or has been expanded, and a return-path on-off valve that opens/closes the internal return path. In the Rankine circuit according to a preferable aspect, the pressure preventing means has a simple configuration.

Preferably, the return-path on-off path is an electromagnetic valve. In the Rankine circuit according to a preferable aspect, the pressure preventing means has a simple configuration.

Preferably, the return-path on-off path is a non-return valve. In the Rankine circuit according to a preferable aspect, the pressure preventing means has a simpler configuration.

Preferably, the expansion unit has a variable capacity. In the Rankine circuit according to a preferable aspect, since the expansion unit has the variable capacity, the capacity of the expansion unit can be adjustable to optimum according to the situation. For instance, immediately after the fluid machine is activated, the capacity of the expansion unit is reduced to prevent the working fluid from being expanded. This alleviates the load on the drive shaft, and reduces the consumed power of the fluid machine.

Preferably, the generating unit has a field coil, and an electric generating capacity of the generating unit can be varied by adjusting the amount of current applied to the field coil. In the Rankine circuit according to a preferable aspect, since the electric generating capacity is variable, the electric generating capacity can be adjusted to optimum according to the situation. For example, in this Rankine circuit, the external power or the torque produced in the expansion unit is convertible into electric power in the generating unit. If there is sufficient external power or torque, the electric generating capacity is increased. If not, the electric generating capacity is reduced, whereby the external power or the torque is effectively used. Alternatively, the electric generating capacity is reduced when the external power is converted into pressure, whereby the external power is preferentially converted into pressure.

Preferably, the Rankine circuit further has pump bypass means for reducing the work of the pump unit. In the Rankine circuit according to a preferable aspect, the pump bypass means reduces the work of the pump unit, whereby the power inputted from the outside can be preferentially used for power generation in the generating unit. To put it differently, the fluid machine can be utilized only as a generator according to the situation, which eliminates the need for an external generator.

Another invention provides a system for utilizing waste heat from a vehicle, which has a Rankine circuit installed in a vehicle. The Rankine circuit includes a fluid machine, a heater that transfers waste heat generated in an internal combustion engine of the vehicle to a heat medium, and a condenser, which are interposed in a circulation path for circulating the heat medium. The fluid machine has a pump unit that includes a first rotating body, draws in the heat medium along with rotation of the first rotating body, and pressurizes and then discharges the heat medium that has been drawn in; an expansion unit that includes a second rotating body, receives the heat medium, and expands and then delivers out the received heat medium along with rotation of the second rotating body; a generating unit that includes a third rotating body that is disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected to the first and third rotating bodies; a power transmission unit that is connected to the drive shaft and the internal combustion engine of the vehicle, and transmits power from the internal combustion engine to the drive shaft; and a connector that connects the drive shaft and the second rotating body to each other, the connector that blocks power transmission between the second rotating body and the drive shaft when rotational frequency of the second rotating body is lower than that of the drive shaft, and allows power transmission from the second rotating body to the drive shaft when the rotational frequency of the second rotating body is about to get higher than that of the drive shaft.

Another invention provides a system for utilizing waste heat from a vehicle, which has a Rankine circuit installed in a vehicle. The Rankine circuit includes a fluid machine, a heater that transfers waste heat generated in an internal combustion engine of the vehicle to the heat medium, and a condenser, which are interposed in a circulation path for circulating a heat medium. The fluid machine has a pump unit that includes a first rotating body, draws in the heat medium along with rotation of the first rotating body, and pressurizes and then discharges the heat medium that has been drawn in; an expansion unit that includes a second rotating body, receives the heat medium, and expands and then delivers out the received heat medium along with rotation of the second rotating body; a generating unit that includes a third rotating body that is disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected to the first rotating body; a power transmission unit that is connected to the drive shaft and the internal combustion engine of the vehicle, and transmits power from the internal combustion engine to the drive shaft; and a connector that connects the drive shaft to the second and third rotating bodies, the connector that blocks power transmission between the second and third rotating bodies and the drive shaft when rotational frequencies of the second and third rotating bodies are lower than that of the drive shaft, and allows power transmission from the second and third rotating bodies to the drive shaft when the rotational frequencies of the second and third rotating bodies are about to get higher than that of the drive shaft.

Another invention provides a system for utilizing waste heat from a vehicle, which has a Rankine circuit installed in a vehicle. The Rankine circuit includes a fluid machine, a heater that transfers waste heat generated in an internal combustion engine of the vehicle to the heat medium, and a condenser, which are interposed in a circulation path for circulating a heat medium. The fluid machine has a pump unit that includes a first rotating body, draws in the heat medium along with rotation of the first rotating body, and pressurizes and then discharges the heat medium that has been drawn in; an expansion unit that includes a second rotating body, receives the heat medium, and expands and then delivers out the received heat medium along with rotation of the second rotating body; a generating unit that includes a third rotating body that is disposed coaxially with the first and second rotating bodies, and generates electric power along with rotation of the third rotating body; a drive shaft that is integrally connected to the first, second and third rotating bodies; and a power transmission unit that is connected to the drive shaft and the internal combustion engine of the vehicle, and transmits power from the internal combustion engine to the drive shaft.

The system for utilizing waste heat from a vehicle according to the invention has a simple configuration because a single fluid machine functions as a pump, an expander, and a generator. A configuration for connecting the internal combustion engine and the power transmission device of the fluid machine to each other is also simple. Consequently, the system for utilizing waste heat is easy to install in a vehicle.

According to the system for utilizing waste heat, the waste heat from the internal combustion engine is converted into electric power, so that fuel consumption of the vehicle is improved. Moreover, since the internal combustion engine and the power transmission unit of the fluid machine are connected to each other, it is possible to convert a kinetic energy into electric power when the vehicle is braked or decelerated. According to the system for utilizing waste heat, therefore, the fuel consumption of the vehicle is further improved.

BEST MODE OF CARRYING OUT THE INVENTION

FIG. 1shows a system A for utilizing waste heat from a vehicle according to a first embodiment. The system A for utilizing waste heat, for example, retrieves the heat of exhaust gas discharged from a vehicle engine (internal combustion engine)10. The system A for utilizing waste heat has a Rankine circuit12. The Rankine circuit12includes a circulation path13through which a working fluid (heat medium) circulates. The circulation path13is constructed, for example, of a duct or a pipe.

A pump unit16of a fluid machine14is interposed in the circulation path13in order to flow the working fluid. Furthermore, a heater18, an expansion unit20of the fluid machine14, and the condenser22are also interposed in the circulation path13on the downstream side of the pump unit16as seen in a direction that the working fluid flows. The pump unit16draws in the working fluid on the condenser22side. The pump unit16then pressurizes the working fluid that has been drawn in, and discharges the working fluid toward the heater18. The working fluid discharged from the pump unit16is in the form of liquid having low temperature and high pressure.

The heater18is a heat exchanger, and includes a low-temperature flow path18aconstructing a section of the circulation path13, and a high-temperature flow path18bcapable of exchanging heat with the low-temperature flow path18a. The high-temperature flow path18bis interposed in an exhaust pipe24extending, for example, from an engine10. When passing through the heater18, the low-temperature and high-pressure working fluid in the liquid form receives the heat of the exhaust gas produced in the engine10. The heater18transfers the heat of the exhaust gas to the working fluid. In result, the working fluid is heated and brought into a high-temperature and high-pressure superheated steam state.

The expansion unit20of the fluid machine14expands the working fluid that has come into the superheated steam state. The working fluid is thus brought into a high-temperature and low-pressure superheated steam state.

The condenser22is a heat exchanger, and condenses the working fluid that has flown out of the expansion unit20by exchanging heat with outside air, to thereby bring the working fluid into a low-temperature and low-pressure liquid form. To be specific, an electric fan (not shown) is disposed near the condenser22, and the working fluid is refrigerated by wind blowing from before backward in the vehicle and wind from the electric fan. The working fluid refrigerated in the condenser22is drawn in again by the pump unit16and circulates through the circulation path13.

The expansion unit20is capable of not only expanding the working fluid but also outputting the heat energy of the working fluid after converting the heat energy into torque (rotational force). In addition to the pump unit16, a generating unit26is connected to the expansion unit20so that the torque outputted from the expansion unit20may be used. An electric load28, such as a battery, which uses or accumulates the generated electric power, is properly connected to the generating unit26.

The fluid machine14has a power transmission unit30for inputting/outputting the torque. The power transmission unit30is, for example, an electromagnetic clutch. The electromagnetic clutch is actuated by ECU (electrical control unit)31, and is capable of intermittently transmitting the torque.

To be more concrete, as illustrated inFIG. 2, the expansion unit20, the generating unit26and the pump unit16are serially connected together in the order named.

The expansion unit20is, for example, a scroll-type expander. A cup-shaped casing32(expansion-unit casing) of the expansion unit20has an opening that is virtually covered with a partition wall34. A through-hole is formed in the center of the partition wall34.

In the expansion-unit casing32, a fixed scroll36is fixed, and a high-pressure chamber38is partitioned off on a back side of the fixed scroll36. The high-pressure chamber38communicates with the heater18through an inlet port formed in the expansion-unit casing32and a section of the circulation path13, which is connected to the inlet port.

On a front side of the fixed scroll36, a movable scroll40is so set as to be engaged with the fixed scroll36. An expansion chamber42that expands the working fluid is marked off between the fixed scroll36and the movable scroll40. A space surrounding the movable scroll40is marked off as a low-pressure chamber44that takes in the expanded working fluid. An induction hole46is formed through substantially the center of a base plate of the fixed scroll36. The expansion chamber42that is located in a diametrically center of the fixed and movable scrolls36and40communicates with the high-pressure chamber38through the induction hole46.

If the working fluid is expanded in the expansion chamber42located in the diametrically center, the expansion chamber42is increased in capacity and is displaced diametrically outward along the vertical walls of the fixed and movable scrolls36and40. The expansion chamber42eventually communicates with the low-pressure chamber44, and the expanded working fluid flows into the low-pressure chamber44. The low-pressure chamber44communicates with the condenser22through an outlet port, not shown, and a part of the circulation path13, which is connected to the outlet port.

Along with the expansion of the working fluid, the movable scroll40is caused to orbit relative to the fixed scroll36. This orbital motion is converted into rotational motion by orbital mechanism.

In other words, a boss is integrally formed in a back face of a base plate of the movable scroll40. An eccentric bush50is placed within the boss so as to be allowed to make relative rotation through a needle bearing48. A crank pin52is inserted through the eccentric bush50. The crank pin52projects from a disc54in an eccentric position. A shaft (second rotating body)56integrally projects from the opposite side of the disc54to the crank pin52concentrically with the crank pin52. The shaft56is rotatably supported by the partition wall34through a radial bearing58, such as a ball bearing. In short, the orbital motion of the movable scroll40is converted into the rotational motion of the shaft56.

The orbital mechanism has, for example, a ball coupling60for preventing an axial rotation of the movable scroll40in orbital motion and receiving thrust pressure. The ball coupling60is set between an outer circumferential portion of the base plate of the movable scroll40and a portion of the partition wall34, which faces the outer circumferential portion.

The pump unit16is, for example, a trochoid pump, but may be a gear pump. The pump unit16has a cylindrical casing (pump-unit casing62) that is open at both ends. A pair of ring-like covers64are placed in the pump-unit casing62with given distance away from each other. An internal gear (first rotating body)66is rotatably disposed between the covers64, and an external gear68is fixedly arranged around the internal gear66.

A pump chamber70that pressurizes the working fluid along with rotation of the internal gear66is marked off between the internal gear66and the external gear68. The working fluid is drawn from the condenser22into the pump chamber70through an intake port, not shown, and a section of the circulation path13, which is connected to the intake port. The working fluid that has been pressurized within the pump chamber70is discharged toward the heater18through a discharge port, not shown, and a portion of the circulation path13, which is connected to the discharge port.

In order to rotate the internal gear66, the internal gear66is integrally and rotatably fixed to a drive shaft72. The drive shaft72penetrates the cover64and the pump-unit casing62. The drive shaft72also penetrates a lid member74fixed to the open end of the pump-unit casing62. The lid member74is made up of a cylinder76and a flange78. The flange78is fitted to the open end of the pump-unit casing62.

Inside the cylinder76, radial bearings79and80are arranged in their respective ends of the cylinder76. The cylinder76rotatably supports the drive shaft72through the radial bearings79and80. A shaft sealer81such as a lip seal is placed in the cylinder76, and airtightly marks off the inside of the cylinder76.

An electromagnetic clutch functioning as the power transmission unit30is connected to one end of the drive shaft72projecting from the cylinder76.

To be concrete, the power transmission unit30has a rotor83disposed outside the cylinder76through a radial bearing82. A pulley84is fixed onto an outer circumferential surface of the rotor83. A belt85, shown by a dashed line, is bridged between the pulley84and a pulley of the engine10. When supplied with power from the engine10, for example, the pulley84and the rotor83are able to rotate. A solenoid86is disposed inside the rotor83. The solenoid86is fed with electricity from the ECU31and thus generates a magnetic field.

A ring-like armature88is disposed near an end face of the rotor83. The armature88is connected to a boss92through an elastic member90such as a leaf spring. The boss92is fitted to one end of the drive shaft72through splines, so that the armature88can rotate integrally with the drive shaft72. Because of a magnetic field of the solenoid86, the armature88is able to stick to the rotor83while resisting against a biasing force of the elastic member90. Accordingly, power can be transmitted between the rotor83and the armature88.

A cylindrical casing (generating-unit casing)93of the generating unit26is sandwiched between the partition wall34and the pump-unit casing62. The expansion-unit casing32, the partition wall34, the generating-unit casing93, the pump-unit casing62, and the lid member74are connected together, thereby making up a single housing for the fluid machine14.

In the generating-unit casing93, there is disposed a support member97that is fixed to the pump-unit casing62. A central portion of the drive shaft72is rotatably supported by the pump-unit casing62through a radial bearing99and the support member97.

The other end of the drive shaft72reaches the through-hole of the partition wall34. The other end of the drive shaft72is rotatably supported by the partition wall34through a needle bearing94. A one-way clutch95functioning as a connector is fixed to the inside of the other end of the drive shaft72. The other end of the drive shaft72and the shaft56of the orbital mechanism are connected to each other through the one-way clutch95.

If a rotational frequency of the shaft56is lower than that of the drive shaft72when the shaft56and the drive shaft72rotate in the same direction, the one-way clutch95blocks the power transmission between the shaft56and the drive shaft72. If the rotational frequency of the shaft56is about to get higher than that of the drive shaft72, the one-way clutch95allows the power transmission between the shaft56and the drive shaft72. In result, the shaft56and the drive shaft72rotate integrally with each other.

A rotor (third rotating body)96is fixed to a section of the drive shaft72, which extends through the generating-unit casing93. The rotor96is made up, for example, of permanent magnet. The rotor96is thus positioned coaxially with the shaft56and the internal gear66.

A stator is fixed to the inner circumferential surface of the generating-unit casing93so as to surround the rotor96. The stator has a yoke98and, for example, three coils100wound around the yoke98. The coils100are so wired as to generate three-phase alternating current along with rotation of the rotor96. The alternating current that has been generated is supplied to the external load28through a leading line, not shown.

The generating unit26does not function as a motor, so that the shape of the yoke98, the number of windings of the coils100, and the like, are determined so that power generation efficiency becomes high.

A method of using the system A for utilizing waste heat from a vehicle will be described below with a focus on operations of the fluid machine14and the Rankine circuit12.

When the ECU31turns on the power transmission unit30to activate the Rankine circuit12, the power of the engine10is inputted to the drive shaft72. The internal gear66of the pump unit16rotates along with the rotation of the drive shaft72. The pump unit16draws in the working fluid on the upstream side. The pump unit16then pressurizes the working fluid that has been drawn in, and discharges the working fluid on the downstream side.

The working fluid is thus circulated through the circulation path13. The working fluid is heated by the heater18and expanded by the expansion unit20.

Immediately after the activation of the Rankine circuit12, the working fluid in the circulation path13is low in pressure. The rotational frequency of the movable scroll40, namely, the rotational frequency of the shaft56of the orbital mechanism, is lower than that of the drive shaft72. The one-way clutch95blocks the power transmission between the shaft56and the drive shaft72.

<Automatic Drive and Power Generation>

After the activation of the Rankine circuit12, if the pressure of the working fluid in the circulation path13is sufficiently increased, the rotational frequency of the shaft56of the orbital mechanism is about to get higher than that of the drive shaft72. If the rotational frequency of the shaft56of the orbital mechanism in a free state becomes higher than that of the drive shaft72, the one-way clutch95comes into a locked state, and the shaft56and the drive shaft72rotate integrally with each other.

If the torque transmitted from the shaft56to the drive shaft72becomes high enough to operate the pump unit16, the ECU31turns off the power transmission unit30and blocks the power supply from the engine10. The fluid machine14is switched to automatic drive in which the pump unit16is operated by using the torque generated in the expansion unit20.

At the same time, the rotor96of the generating unit26rotates along with the rotation of the drive shaft72, and the generating unit26generates alternating current. The alternating current is supplied to the load28, and is properly accumulated or consumed by the load28. The load28may include a rectifier that converts alternating current into direct current.

After the fluid machine14is switched to the automatic drive, the load of the engine10is decreased. However, when the vehicle is braked or decelerated, the power transmission unit30may be turned on by the ECU31. That is, the electromagnetic clutch may be engaged. By so doing, the fluid machine14fully functions as a regenerative brake, and an auxiliary load for deceleration is applied to the engine10. Furthermore, the generating unit26generates electricity, and a kinetic energy of the vehicle is converted into electric power.

The torque of the fluid machine14may be supplied to the engine10without switching the fluid machine14to the automatic drive. An extra portion of the torque generated in the expansion unit20, which remains after the torque is consumed in the pump unit16and the generating unit26, may be outputted to the engine10through the power transmission unit30.

As described, the system A for utilizing waste heat from a vehicle according to the first embodiment converts the waste heat, which is generated in the engine10of the vehicle, into electric power by using the fluid machine14. Consequently, the fuel consumption of the vehicle is improved.

The system A for utilizing waste heat from a vehicle has a simple configuration because the single fluid machine14functions as a pump, a generator, and an expansion unit.

Particularly in the fluid machine14, since the internal gear66of the pump unit16, the shaft56of the expansion unit20, and the rotor96of the generating unit26are coaxially arranged, the fluid machine14can be downsized. The fluid machine14is therefore light in weight and low in cost, thereby having high installability in the vehicle.

In the fluid machine14, the drive shaft72and the internal gear66of the pump unit16are at least integrally connected to each other, and the power transmission unit30for transmitting external power is connected to the drive shaft72. The pump unit16can therefore be started by external power. Accordingly, the generating unit26is not required to serve as an electric motor. In the fluid machine14, therefore, the generating unit26is so constructed that the power generation efficiency is high, and the power transmitted through the drive shaft72is converted into electric power with high efficiency.

With the fluid machine14, the torque generated in the expansion unit20can be outputted to the outside and used, and the power of the engine10can be compensated.

In the system A for utilizing waste heat from a vehicle, after the pump unit16of the fluid machine14is started by external power, during a period in which the rotational frequency of the shaft56of the expansion unit20is lower than that of the drive shaft72, the one-way clutch95functioning as a connector blocks the power transmission between the shaft56and the drive shaft72. During a given period after the pump unit16is started, the load applied to the drive shaft72is alleviated, and the consumed power of the fluid machine14is reduced.

The invention is not limited to the first embodiment, and may be modified in various ways.

For example, the system A for utilizing waste heat converts the heat of exhaust gas into electric power, but may convert the heat of cooling water of the engine10into electric power. The system A for utilizing waste heat does not necessarily have to be applied to a vehicle. Nevertheless, the system A is suitable for a vehicle since the engine10and the power transmission unit30can be easily connected to each other.

The generating unit26of the fluid machine14generates alternating current, but may generate direct current. However, as compared to a DC generator (DC motor), the generating unit26that generates alternating current is light in weight and high in power generation efficiency. The generating unit26also does not require a brush, thereby facilitating the maintenance.

Although the drive shaft72of the fluid machine14is made up of one member, it is also possible to construct the drive shaft by integrally connecting a plurality of members together by means of couplings or the like.

In the fluid machine14, the power transmission unit30is an electromagnetic clutch capable of maintaining power. However, the power transmission unit30may be a simple pulley that constantly transmits power. On the other hand, the electromagnetic clutch can properly continue the input/output of torque between the fluid machine14and the outside.

FIG. 3shows a schematic configuration of a system B for utilizing waste heat from a vehicle according to a second embodiment. Components identical to those of the system A for utilizing waste heat according to the first embodiment will be provided with the same reference marks, and the explanation thereof will be omitted.

The system B for utilizing waste heat further includes a check valve102and a circulation-path on-off valve104. The check valve102is interposed in a section of the circulation path13, which extends between the pump unit16of the fluid machine14and the heater18. The check valve102allows the working fluid to pass only in a direction from the pump unit16toward the heater18. The circulation-path on-off valve104is interposed in a section of the circulation path13, which extends between the heater18and the expansion unit20of the fluid machine14, and is capable of opening/closing the circulation path13in response to signals from the ECU31.

The system B for utilizing waste heat has pump bypass means. The pump bypass means is made up of an external bypass106that is disposed in the circulation path13in parallel with the pump unit16, and a bypass on-off valve108that is interposed in the external bypass106. The bypass on-off valve108is an electromagnetic valve and capable of opening/closing the external bypass106in response to signals from the ECU31.

In the system B for utilizing waste heat, by closing the circulation path13with the circulation-path on-off valve104before the expansion unit20, external power is accumulated as pressure energy in a section of the circulation path13, which extends from the check valve102to the circulation-path on-off valve104. When the circulation-path on-off valve104is opened, the accumulated pressure energy is converted into torque in the expansion unit20, and then converted into electric power in the generating unit26(regeneration of accumulation pressure). In short, the system B for utilizing waste heat accumulates the external power in a form other than electric power according to the situation.

In the system B for utilizing waste heat, if the work of the pump unit16is reduced by bypassing the pump unit16with the pump bypass means. This makes it possible to preferentially use the power inputted from the outside for power generation in the generating unit16. To put it differently, the fluid machine14can be utilized only as a generator according to the situation, which eliminates the need for an external generator (alternator) and enables the downsizing of the vehicle.

FIG. 4shows a schematic configuration of a system C for utilizing waste heat from a vehicle according to a third embodiment. Components identical to those of the system A for utilizing waste heat according to the first embodiment and those of the system B for utilizing waste heat according to the second embodiment will be provided with the same reference marks, and the explanation thereof will be omitted.

In a fluid machine110applied to the system C for utilizing waste heat, the power transmission unit30and the internal gear66of the pump unit16are integrally connected to a first drive shaft112. The rotor96of the generating unit30and the shaft56of the expansion unit20are integrally connected to a second drive shaft114. The first drive shaft112and the second drive shaft114are connected to each other through a one-way clutch116functioning as a connector.

When rotational frequency of the second drive shaft114, or that of the shaft56and of the rotor96, is lower than rotational frequency of the first drive shaft112, the one-way clutch116blocks power transmission between the first drive shaft112, the second drive shaft114and the first drive shaft112. If the rotational frequency of the second drive shaft114is about to get higher than that of the drive shaft72, the one-way clutch116allows the power transmission between the first drive shaft112and the second drive shaft114. In result, the first drive shaft112and the second drive shaft114rotate integrally with each other.

In the system C for utilizing waste heat, too, during a given period after the fluid machine110is activated, the power transmission from the first drive shaft112to the second drive shaft114is blocked by the one-way clutch116, and the consumed power of the fluid machine110is reduced.

The torque generated in the expansion unit30is not only converted into electric power by the generating unit26but also transmitted through the one-way clutch116to the first drive shaft112when the rotational frequency of the second shaft114is higher than that of the first drive shaft112. The torque transmitted to the first drive shaft112is used as power for the pump unit16. If this torque is sufficiently high, the fluid machine110is able to operate independently without receiving external power. Furthermore, the torque produced in the expansion unit20can be outputted to the outside through the power transmission unit30.

The system C for utilizing waste heat is also capable of accumulating pressure energy by closing the circulation-path on-off valve104and of converting the accumulated pressure energy into electric power. As in the system A for utilizing waste heat, the check valve102and the circulation-path on-off valve104may be eliminated from the system C for utilizing waste heat.

FIG. 5is a view showing a schematic configuration of a system D for utilizing waste heat from a vehicle according to a fourth embodiment. Components identical to those of the systems A to C for utilizing waste heat will be provided with the same reference marks, and the explanation thereof will be omitted.

In a fluid machine120applied to the system D for utilizing waste heat, the power transmission unit30, the internal gear66of the pump unit16, the rotor96of the generating unit30, and the shaft56of the expansion unit20are integrally connected to a single drive shaft122.

The system D for utilizing waste heat further includes an external return path124disposed in the circulation path13in parallel with the expansion unit20, and an electromagnetic valve126functioning as a return-path on-off valve, which is interposed in the external return path124. The electromagnetic valve126is capable of opening/closing the external return path124in response to signals from the ECU31.

In the fluid machine120of the system D for utilizing waste heat, too, during a period in which the circulation path13is closed by the circulation-path on-off valve104, power is accumulated as pressure energy, and at the same time, the movable scroll40of the pump unit20makes orbital motion. In the system D for utilizing waste heat, therefore, the external return path124is opened by opening the electromagnetic valve126when the circulation path13is closed by the circulation-path on-off valve104, to thereby suppress a pressure drop in a section of the circulation path13, which extends between the circulation-path on-off valve104and the expansion unit20. The expansion unit20is thus prevented from operating like a vacuum pump, thereby suppressing the increase of load that is applied from the expansion unit20to the drive shaft122.

After the activation of the fluid machine120, even if the circulation path13is opened by opening the circulation-path on-off valve104, the expansion unit20is bypassed by opening the electromagnetic valve126to open the external return path124until the pressure of the working fluid within the circulation path13is adequately increased. In result, the load that is applied from the expansion unit20to the drive shaft122is alleviated during a given period after the activation.

If the external return path124is closed by closing the electromagnetic valve126when the pressure of the working fluid is adequately increased after the activation of the fluid machine120, the fluid machine120is switched to the automatic drive.

The external return path124and the electromagnetic valve126, or alternatively the check valve102and the circulation-path on-off valve104, may be eliminated from the system D for utilizing waste heat.

FIG. 6shows a schematic configuration of a system E for utilizing waste heat from a vehicle according to a fifth embodiment. Components identical to those of the systems A to D for utilizing waste heat will be provided with the same reference marks, and the explanation thereof will be omitted.

The system E for utilizing waste heat has a non-return valve128functioning as a return-path on-off valve. When pressure on the immediate downstream side of the expansion unit20becomes lower than pressure on the immediate upstream of the expansion unit20, the non-return valve128allows the working fluid to flow from downstream to upstream. The non-return valve128automatically suppresses a pressure drop in the section of the circulation path13, which extends between the circulation-path on-off valve104and the expansion unit20. Similarly to the electromagnetic valve126, the non-return valve128reduces the load applied from the expansion unit20to the drive shaft122, when accumulating the pressure energy or during a given period after the activation.

In the systems D and E for utilizing waste heat, the external return path124and the return-path on-off valve function as means for preventing a pressure drop in the section of the circulation path13, which extends between the circulation-path on-off valve104and the expansion unit20. However, the pressure-drop preventing means is not limited to them.

For example, the pressure-drop preventing means may be capacity variable means of the expansion unit20. The capacity variable means has a bypass hole130that is formed in a base plate of the fixed scroll36, for example, as shown inFIG. 7. The bypass hole130leads to an introduction hole46or a high-pressure chamber38through an interior channel132. A capacity control valve134is interposed in the interior channel132. The ECU31is capable of controlling the opening/closing of the capacity control valve134, whereby the capacity of the expansion unit20is variable. In this case, if the interior channel132is opened by opening the capacity control valve134, this provides the same advantage as in the case where the return path124is opened by opening the return on-off valve. When the capacity variable means is used as the pressure-drop preventing means, the capacity control valve134corresponding to a return-path on-off valve may be utilized as a non-return valve.

In the systems B, D and E utilizing waste heat, the external bypass106and a bypass on-off valve form the pump bypass means. However, the pump bypass means does not necessarily have to be formed this way.

For example, as shown inFIG. 8, it is also possible to provide an internal bypass140connecting an upstream pump chamber70to a downstream pump chamber70, and interpose a bypass on-off valve142in the internal bypass140. The opening/closing operation of the bypass on-off valve142is controlled by the ECU31.

In this case, if the ECU31opens the bypass on-off valve142and thus opens the internal bypass140, the working fluid being pressurized is discharged. The work of the pump unit16is reduced in this manner, and the torque inputted from outside can be used only for power generation in the generating unit26.

Although the first to fifth embodiments use a permanent magnet as the rotor96of the generating unit26, electromagnet may be utilized. In this case, as shown inFIG. 9, if the amount of current to be supplied to a field coil (motor coil)150that is disposed in the rotor is adjusted by the ECU31, the electric generating capacity can be controlled, and the torque that is consumed in the generating unit26becomes adjustable. This makes it possible to properly distribute the external power to the pump unit16, the generating unit26and the expansion unit20according to the situation or to properly distribute the torque generated in the expansion unit20to the pump unit16and the generating unit26.

Concretely, the electric generating capacity is reduced to suppress a drive torque of the generating unit26at the time of activation of the fluid machine14or120, and the electric generating capacity can be increased after the fluid machine14or120is switched to the automatic drive. When the pressure energy is accumulated, the drive torque of the generating unit26can be suppressed by reducing the electric generating capacity. Furthermore, when the vehicle is braked or decelerated, the drive torque of the generating unit26may be increased by enlarging the electric generating capacity, to thereby greaten the braking force that is provided to the engine10.

In the first to fifth embodiments, the pump unit16is of a trochoid type, but the pump unit is not particularly limited in type. Although the expansion unit20is of a scroll type, the type of the expansion unit is not particularly limited, either. For example, the expansion unit20may be of a reciprocating type. In this case, the arrangement of the pump unit16, the generating unit26and the expansion unit20is not particularly limited.