JP2010190185A - Vehicle loaded with rankine cycle system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle loaded with a rankine cycle system having a clutch on a path transmitting regenerated power to an engine, in which prediction accuracy of the regenerated power is improved, and engagement and release of the clutch can be properly performed. <P>SOLUTION: The clutch 60 is arranged on the power transmission path between an expander 23 and the engine 10. An ECU 40 predicts the regenerated power based on rotating speed of the expander 23 and refrigerant pressure in an upstream side. When a predicted value of the regenerated power is positive, the clutch 60 is engaged, and when the value is zero or negative, the clutch 60 is released. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle equipped with a Rankine cycle system that recovers waste heat of an engine.

  A technology has been proposed to improve the fuel efficiency of the engine by providing a waste heat recovery device that regenerates the heat energy that has been thrown out of the vehicle from the exhaust and cooling water of the engine as power, and assists the engine with the regenerated power. ing.

  Patent Document 1 proposes that in such a waste heat recovery apparatus, a clutch is disposed on a path for transmitting the regenerated power to the engine. According to this configuration, when the waste heat recovery device becomes a load on the engine, such as during rapid acceleration, the waste heat recovery device can be disconnected from the engine by releasing the clutch, which is originally intended to improve fuel efficiency. It can be avoided that the waste heat recovery device causes the deterioration of the fuel consumption of the engine.

JP 2007-231857 A

  In Patent Document 1, the power regenerated by the waste heat recovery device is predicted based on the exhaust temperature, and based on this, the engagement and disengagement of the clutch are controlled.

  However, since there is a delay before the change in the exhaust temperature appears in the regenerative power, such a prediction method releases the clutch even when it does not actually become a load, or when it becomes a load. Even so, there was a possibility of engaging the clutch.

  The present invention has been made in view of such technical problems, and in a vehicle equipped with a Rankine cycle system in which a clutch is disposed on a path for transmitting regenerated power to the engine, the accuracy of regenerating power is improved. An object of the present invention is to appropriately engage and disengage the clutch.

  According to an aspect of the present invention, an engine and a Rankine cycle in which waste heat of the engine is recovered in a refrigerant and the recovered waste heat is regenerated as power by an expander (hereinafter, this power is referred to as “regenerative power”). A Rankine cycle system-equipped vehicle comprising: a power transmission mechanism that transmits the regenerative power to the engine; and a power transmission path between the expander and the engine formed by the power transmission mechanism. A rotation speed acquisition means for acquiring a rotation speed of the expander, an upstream refrigerant pressure acquisition means for acquiring an upstream refrigerant pressure that is a pressure of a refrigerant flowing into the expander, and the expansion Regenerative power prediction means for predicting the regenerative power based on the rotational speed of the machine and the upstream refrigerant pressure, and the clutch is engaged when the predicted value of the regenerative power is positive, Rankine cycle system-equipped vehicle that is characterized in that and a clutch control means for releasing the clutch when the negative is provided.

  According to another aspect of the present invention, the engine and the waste heat of the engine are recovered in a refrigerant, and the recovered waste heat is regenerated as power by an expander (hereinafter, this power is referred to as “regenerative power”). A Rankine cycle system-equipped vehicle, the power transmission mechanism transmitting the regenerative power to the engine, and the power between the expander and the engine formed by the power transmission mechanism A clutch disposed on a transmission path; a rotational speed acquisition unit that acquires a rotational speed of the expander; a refrigerant pressure difference acquisition unit that acquires a refrigerant pressure difference between an upstream side and a downstream side of the expander; and the expansion Regenerative power predicting means for predicting the regenerative power based on the rotational speed of the machine and the refrigerant pressure difference, and the clutch is engaged when the predicted value of the regenerative power is positive, and when zero or negative Rankine cycle system equipped vehicle, characterized by comprising: a clutch control means for releasing the serial clutch is provided.

  According to these aspects, the regenerative power can be predicted with higher accuracy than when the regenerative power is predicted from the exhaust temperature, and the clutch can be appropriately engaged and disengaged according to the generation state of the regenerative power. it can.

1 is a schematic configuration diagram of a vehicle equipped with a Rankine cycle system according to an embodiment of the present invention. It is the figure which showed an example of the power transmission mechanism. It is the figure which showed another example of the power transmission mechanism. It is the flowchart which showed the content of the engagement / release control of a clutch. It is an expander torque map. It is a figure for demonstrating the effect of embodiment of this invention. It is another example of an expander torque map. It is another example of an expander torque map.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a vehicle equipped with a Rankine cycle system according to an embodiment of the present invention. The vehicle includes an engine 10 and a Rankine cycle system 20.

  The engine 10 is a water-cooled internal combustion engine, and is temperature-controlled by cooling water flowing through the inside. The cooling water after cooling the engine 10 is sent to an evaporator 22 (to be described later) and a radiator (not shown) through the flow path 11 and cooled.

  The Rankine cycle system 20 is a system that recovers waste heat of the engine 10 from a coolant of the engine 10 into a refrigerant and regenerates the recovered waste heat as power. The Rankine cycle system 20 includes a pump 21, an evaporator 22, an expander 23, and a condenser 24, and each component is connected by flow paths 25a to 25d through which a refrigerant such as R134a flows.

  The pump 21 is an electric pump. The evaporator 22 is a heat exchanger that causes heat exchange between the coolant of the engine 10 and the refrigerant to heat and vaporize the refrigerant. The expander 23 is a steam turbine that converts heat into rotational energy by expanding a vaporized refrigerant. The condenser 24 is a heat exchanger that performs heat exchange between the outside air and the refrigerant, and cools and liquefies the refrigerant. The refrigerant liquefied by the condenser 24 is sent again to the evaporator 22 by the pump 21 and circulates through each component of the Rankine cycle system 20.

  In the flow path 25 a connecting the evaporator 22 and the expander 23, the upstream refrigerant temperature sensor 31 that detects the upstream refrigerant temperature Tc that is the temperature of the refrigerant flowing into the expander 23, and the refrigerant flowing into the expander 23 An upstream refrigerant pressure sensor 32 that detects the upstream refrigerant pressure Pd, which is a pressure, is attached. A downstream refrigerant pressure sensor 33 that detects a downstream refrigerant pressure Ps that is the pressure of the refrigerant flowing out of the expander 23 is attached to the flow path 25b that connects the expander 23 and the condenser 24. These sensors 31 to 33 are electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 40, and detection signals of these sensors 31 to 33 are input to the ECU 40.

  The Rankine cycle system 20 is configured as described above, and the torque of the expander 23 (hereinafter referred to as “expander torque”, corresponding to “regenerative power” in the claims) Tex is transmitted via the power transmission mechanism 50. Is transmitted to the engine 10.

  FIG. 2A shows an example of the power transmission mechanism 50. The power transmission mechanism 50 includes an expander pulley 51 attached to the output shaft of the expander 23, an expander pulley 51, an alternator pulley 52, a crank pulley 53 of the engine 10, and a belt wound around the pulley 54 of the air conditioner compressor. 55. The expander torque Tex is transmitted to the engine 10, the alternator, and the air conditioner compressor via the belt 55, and the engine 10 is assisted.

  Here, when the expander torque Tex is positive, the engine 10 can be assisted by this, so that the fuel consumption of the engine 10 can be improved. However, when the expander torque Tex is zero or negative, conversely, the expander 23 becomes a load on the engine 10 and deteriorates the fuel consumption of the engine 10.

  For this reason, in this embodiment, the clutch 60 is disposed between the crankshaft (not shown) of the engine 10 and the crank pulley 53 so that the expander 23 can be disconnected from the engine 10 as necessary. Yes. The clutch 60 is, for example, an electromagnetic clutch, and is engaged / released in response to a control signal from the ECU 40.

  The position where the clutch 60 is disposed is not limited to this position, and may be on the power transmission path between the expander 23 and the engine 10 formed by the power transmission mechanism 50. For example, as shown in FIG. 2B, a clutch 60 can be disposed between the output shaft (not shown) of the expander 23 and the expander pulley 51.

  Returning to FIG. 1, the ECU 40 includes a CPU 41, a storage device 42 including a RAM / ROM, an input / output interface 43, and the like. The storage device 42 stores a program, a map, and the like for executing control to be described later. In addition to the detection signals of the sensors 31 to 33, the input / output interface 43 receives an engine rotation speed signal from an engine controller (not shown). The CPU 41 reads and executes a program stored in the storage device 42, and predicts the torque Tex of the expander 23 based on the rotational speed Ne of the expander 23 and the upstream refrigerant pressure Pd. Then, the CPU 41 generates an engagement / disengagement signal for the clutch 60 according to whether the expander torque Tex is positive or not, and outputs it to the clutch 60 from the input / output interface 43.

  FIG. 3 is a flowchart showing the contents of the engagement / release control of the clutch 60 executed by the ECU 40. This control is executed in the ECU 40 every predetermined time (for example, 10 milliseconds). Hereinafter, the engagement / release control of the clutch 60 will be described with reference to this.

  In ST01, the ECU 40 acquires the upstream refrigerant pressure Pd of the expander 23 from the upstream refrigerant pressure sensor 32.

  In ST02, the ECU 40 acquires the rotational speed Ne of the engine 10 from an engine controller (not shown). Then, the ECU 40 calculates the rotational speed Nex of the expander 23 based on the rotational speed Ne of the engine 10 and the pulley ratio of the crank pulley 53 and the expander pulley 51.

  In ST03, the ECU 40 predicts the expander torque Tex. The ECU 40 predicts the expander torque Tex by searching for values corresponding to the rotational speed Nex of the expander 23 and the upstream refrigerant pressure Pd from an expander torque map (FIG. 4) prepared in advance. Since the expander 23 receives the upstream refrigerant pressure Pd and rotates, the expander torque Tex increases as the upstream refrigerant pressure Pd increases if the rotational speed Nex of the expander 23 is the same. Further, if the rotational speed Nex of the expander 23 is high, the amount of refrigerant flowing into the expander 23 is insufficient, so that the expander torque Tex is zero or less in the high rotation range.

  In ST04, the ECU 40 determines whether or not the expander torque Tex is positive. When the expander torque Tex is positive, the process proceeds to ST05, and when the expander torque Tex is zero or negative, the process proceeds to ST06.

  In ST06, the ECU 40 outputs a fastening signal to the clutch 60 and fastens the clutch 60. Thereby, the expander torque Tex is transmitted to the engine 10 and the engine 10 is assisted.

  In ST07, the ECU 30 outputs a release signal to the clutch 60 to release the clutch 60. As a result, the expander 23 is mechanically disconnected from the engine 10, and the expander 23 is prevented from becoming a load on the engine 10.

  Then, the effect of this embodiment is demonstrated.

  In the present embodiment, the clutch 60 is disposed on the power transmission path between the expander 23 and the engine 10. The expander torque Tex is predicted based on the rotational speed Ne of the expander 23 and the upstream refrigerant pressure Pd. The clutch 60 is engaged when the predicted value of the expander torque Tex is positive, and the clutch is engaged when the value is zero or negative. 60 is released.

  When the expander torque Tex is predicted based on the rotational speed Ne of the expander 23 and the upstream refrigerant pressure Pd, the expander torque Tex can be predicted with higher accuracy than when predicted from the exhaust temperature. Engagement / release of the clutch 60 can be appropriately performed in accordance with the state of occurrence. That is, in the present embodiment, it is possible to prevent the clutch 60 from being released even when it is not actually a load, or to be engaged even when it is a load.

  FIG. 5A is a time chart showing how the engine 10 is assisted by the expander torque Tex during vehicle acceleration. FIG. 5B shows a state where the operating state of the expander 23 changes on the expander torque map.

  At time t1, the driver depresses the accelerator pedal, and the accelerator opening APO increases. At this time, the expander 23 generates a positive torque, and the engine 10 is assisted by the expander torque Tex.

  After time t1, the rotational speed Nex of the expander 23 increases in proportion to the rotational speed Ne of the engine 10, and the heat dissipation amount Q of the engine 10 increases with a delay in increasing the rotational speed Ne of the engine 10. Further, the amount of heat recovered by the Rankine cycle system 20 is proportional to the heat dissipation amount Q of the engine 10.

  As the rotational speed Nex of the expander 23 increases, the refrigerant flowing into the expander 23 becomes insufficient and the upstream refrigerant pressure Pd decreases, so the expander torque Tex decreases.

  When the expander torque Tex becomes zero or less at time t2, the clutch 60 is released. This prevents the expander 23 from becoming a load on the engine 10.

  After time t2, the upstream refrigerant pressure Pd of the expander 23 increases due to the increase in the heat dissipation amount Q of the engine 10, and the expander torque Tex becomes positive again at time t3. In response to this, at time t3, the clutch 60 is engaged again, whereby the assist of the engine 10 by the expander torque Tex is resumed.

  As described above, in the present embodiment, the clutch 60 can be appropriately engaged and disengaged according to the state of occurrence of the expander torque Tex.

  In this embodiment, the expander torque Tex is predicted based on the rotation speed Nex of the expander 23 and the upstream refrigerant pressure Pd. However, the rotation speed Ne of the expander 23 and the upstream side and downstream side of the expander 23 are estimated. The expander torque Tex may be predicted based on the refrigerant pressure difference ΔPex on the side. In this case, the expander torque Tex is predicted with reference to the map shown in FIG. 6 in ST03 of FIG. The expander torque Tex is affected by not only the upstream refrigerant pressure Pd of the expander 23 but also the downstream refrigerant pressure Ps, and the larger the difference between the two, the larger the expander torque Tex. Therefore, the prediction accuracy of the expander torque Tex can be further increased by predicting the expander torque Tex based on the refrigerant pressure difference ΔPex between the upstream side and the downstream side.

  The refrigerant pressure difference ΔPex between the upstream side and the downstream side of the expander 23 is the difference between the upstream side refrigerant pressure Pd acquired from the upstream side refrigerant pressure sensor 32 and the downstream side refrigerant pressure Ps acquired from the downstream side refrigerant pressure sensor 33. Obtained by calculation. Alternatively, a differential pressure sensor that detects a pressure difference between the upstream side and the downstream side of the expander 23 may be attached to directly acquire the refrigerant pressure difference ΔPex.

  The expander torque Tex is affected by the upstream side refrigerant temperature Tc of the expander 23. Even if the rotational speed Ne of the expander 23 and the upstream refrigerant pressure Pd (or refrigerant pressure difference ΔPex) are the same, the higher the upstream refrigerant temperature Tc, the more waste heat is recovered by the refrigerant. The machine torque Tex also increases. Therefore, as shown in FIG. 7, if a plurality of maps are prepared according to the upstream refrigerant temperature Tc, and the map referred to in ST03 of FIG. 3 is switched according to the upstream refrigerant temperature Tc, the expansion is performed. The prediction accuracy of the machine torque Tex can be further increased.

  Note that the method of using the influence of the upstream refrigerant temperature Tc for prediction is not limited to the method of switching the map in this way, and is predicted from the rotational speed Ne of the expander 23 and the upstream refrigerant pressure Pd (or refrigerant pressure difference ΔPex). A method of correcting the expander torque Tex according to the upstream refrigerant temperature Tc may be used.

  The embodiment of the present invention has been described above, but the above embodiment is merely an example of application of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configuration of the above embodiment.

  For example, the Rankine cycle system 20 in the above embodiment is a system that recovers the waste heat of the engine 10 from the cooling water of the engine 10, but may be a system that recovers the waste heat of the engine 10 from the exhaust of the engine 10. . In this case, water having a higher boiling point is used as the refrigerant.

  Further, the configuration of the power transmission mechanism 50 is not limited to the configuration using the belt 55, and may be a mechanism that transmits to the engine 10 or a transmission (not shown) connected to the engine 10 via a gear.

  In the above embodiment, the control is performed based on the expander torque Tex. However, the control is performed based on the expander output Wex obtained by multiplying the torque Tex by the expander rotation speed Nex instead of the expander torque Tex. It is also possible. The expression “power” used in the claims includes these torques and outputs.

DESCRIPTION OF SYMBOLS 10 ... Engine 20 ... Rankine cycle system 21 ... Pump 22 ... Heat exchanger 23 ... Expander 24 ... Condenser 31 ... Upstream refrigerant temperature sensor (upstream refrigerant temperature acquisition means)
32 ... Upstream refrigerant pressure sensor (upstream refrigerant pressure acquisition means, refrigerant pressure difference acquisition means)
33 ... Downstream refrigerant pressure sensor (refrigerant pressure difference acquisition means)
40. Electronic control unit (ECU)
DESCRIPTION OF SYMBOLS 50 ... Power transmission mechanism 60 ... Clutch ST02 ... Rotational speed acquisition means ST03 ... Expander torque prediction means ST04-ST06 ... Clutch control means

Claims (4)

A Rankine cycle system comprising: an engine; and a Rankine cycle system that recovers the waste heat of the engine into a refrigerant and regenerates the recovered waste heat as power (hereinafter referred to as “regenerative power”) by an expander. An on-board vehicle,
A power transmission mechanism for transmitting the regenerative power to the engine;
A clutch disposed on a power transmission path between the expander and the engine formed by the power transmission mechanism;
Rotational speed acquisition means for acquiring the rotational speed of the expander;
Upstream refrigerant pressure acquisition means for acquiring an upstream refrigerant pressure that is the pressure of the refrigerant flowing into the expander;
Regenerative power prediction means for predicting the regenerative power based on the rotational speed and upstream refrigerant pressure of the expander;
Clutch control means for engaging the clutch when the predicted value of the regenerative power is positive, and releasing the clutch when zero or negative;
A vehicle equipped with a Rankine cycle system. A vehicle equipped with a Rankine cycle system according to claim 1,
An upstream refrigerant temperature acquisition means for acquiring an upstream refrigerant temperature that is a temperature of the refrigerant flowing into the expander;
The regenerative power prediction means predicts the regenerative power based on the rotational speed of the expander, the upstream refrigerant pressure, and the upstream refrigerant temperature.
A vehicle equipped with a Rankine cycle system. A Rankine cycle system comprising: an engine; and a Rankine cycle system that recovers the waste heat of the engine into a refrigerant and regenerates the recovered waste heat as power (hereinafter referred to as “regenerative power”) by an expander. An on-board vehicle,
A power transmission mechanism for transmitting the regenerative power to the engine;
A clutch disposed on a power transmission path between the expander and the engine formed by the power transmission mechanism;
Rotational speed acquisition means for acquiring the rotational speed of the expander;
Refrigerant pressure difference acquisition means for acquiring a refrigerant pressure difference between the upstream side and the downstream side of the expander;
Regenerative power prediction means for predicting the regenerative power based on the rotational speed and refrigerant pressure difference of the expander;
Clutch control means for engaging the clutch when the predicted value of the regenerative power is positive, and releasing the clutch when zero or negative;
A vehicle equipped with a Rankine cycle system. A Rankine cycle system-equipped vehicle according to claim 3,
An upstream refrigerant temperature acquisition means for acquiring an upstream refrigerant temperature that is a temperature of the refrigerant flowing into the expander;
The regenerative power prediction means predicts the regenerative power based on the rotational speed of the expander, the refrigerant pressure difference and the upstream refrigerant temperature.
A vehicle equipped with a Rankine cycle system.

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