JP2018017203A - Rankine cycle system of vehicle and control method of Rankine cycle system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Rankine cycle system of a vehicle capable of improving a utilization efficiency of waste heat energy recovered from exhaust gas of an internal combustion engine, and a control method of the Rankine cycle system of a vehicle.SOLUTION: A Rankine cycle system of a vehicle includes a first flow passage switching device 40 in a flow passage for working fluid WF between an evaporator 12 and an expander 13, and a second flow passage switching device 41 in a flow passage for working fluid WF between the expander 13 and a condenser 14. The Rankine cycle system is configured to, when driving force of the expander 13 is used to increase braking force of an internal combustion engine 20, control the first flow passage switching device 40 and the second flow passage switching device 41 to inflow the working fluid WF from a second inflow outlet 13b of the expander 13 and outflow the working fluid from a first inflow outlet 13a, thereby performing control to rotate the expander 13 in a reverse direction to a rotation direction of the internal combustion engine 20.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicle Rankine cycle system and a control method for a vehicle Rankine cycle system.

  The vehicle collects a part of the heat energy (exhaust heat energy) of the exhaust gas of the internal combustion engine such as a diesel engine, and drives the expander such as a turbine connected to the engine by the recovered exhaust heat energy. In some cases, a Rankine cycle system that uses the driving force of the expander to assist the engine may be provided.

  As an example of this, a pump that pumps a liquid working fluid, a heater that heats the working fluid from a liquid to a high-temperature gas, an expander that converts the energy of the gas into rotational power for a vehicle, and gas operation There has been proposed a vehicular steam engine including a circuit for normal operation having a condenser that cools fluid back to liquid (see, for example, Patent Document 1).

JP 2011-89452 A

  By the way, in the Rankine cycle system of the conventional vehicle, when it is not necessary to assist the engine, the working fluid is not passed through the inflator but is passed through the passage that bypasses the inflator so that the inflator is not operated. I was doing.

  As described above, even when it is not necessary to assist the engine, no good plan has been proposed for a system for effectively utilizing the exhaust heat energy recovered by the Rankine cycle system or a control method using this system. .

  An object of the present invention is to provide a vehicle Rankine cycle system and a vehicle Rankine cycle system control method capable of improving the utilization efficiency of exhaust heat energy recovered from exhaust gas of an internal combustion engine.

  In order to achieve the above object, a Rankine cycle system for a vehicle according to the present invention includes an evaporator that heats and evaporates a working fluid from a liquid to a gas by exhaust heat of the internal combustion engine, and an evaporator connected to the internal combustion engine. In the Rankine cycle system for a vehicle, comprising: an expander driven by a heated and evaporated working fluid; a condenser that cools and condenses the working fluid that has passed through the expander from gas to liquid; and a control device. And a switching mechanism for switching the direction in which the working fluid flows in the reversal device in the forward and reverse directions, and when the control device assists the internal combustion engine, the switching mechanism causes the working fluid to flow in the expander in the forward direction. In the case where the internal combustion engine is assisted by rotating the expander forward and the braking force of the internal combustion engine is increased, the working fluid is moved forward by the switching mechanism. The direction of flow of the inflator in the opposite direction to reverse the rotation of said expander and is configured to perform control to increase the braking force of the internal combustion engine.

  In addition, the vehicle Rankine cycle system control method of the present invention for achieving the above object includes an evaporator that heats and evaporates a working fluid from a liquid to a gas by exhaust heat of the internal combustion engine, and the internal combustion engine. An expander driven by the working fluid heated and evaporated by the evaporator, a condenser for cooling and condensing the working fluid that has passed through the expander from a gas to a liquid, and a direction in which the working fluid flows in the expander When the internal combustion engine is assisted in the vehicle Rankine cycle system control method configured to switch to the switching mechanism, the expander sets the direction in which the working fluid flows through the expander as the positive direction by the switching mechanism. When the internal combustion engine is assisted by rotating it forward to increase the braking force of the internal combustion engine, the switching mechanism causes the working fluid to flow through the expander. Which is a reversed direction by the reverse rotation of said expander and wherein the performing control to increase the braking force of the internal combustion engine.

  According to the vehicle Rankine cycle system and the vehicle Rankine cycle system control method of the present invention, not only can the power of the expander be used for assisting the internal combustion engine, but also the direction in which the working fluid flows through the expander is reversed. By switching the rotation direction of the expander to the direction opposite to the rotation direction when assisting the internal combustion engine, the power of the expander can be used to increase the braking force of the internal combustion engine.

  As a result, the utilization efficiency of the exhaust heat energy recovered from the exhaust gas of the internal combustion engine can be improved.

It is a figure which shows when a working fluid passes a normal flow path by the structure of the Rankine cycle system of the vehicle of this invention. It is a figure which shows when a working fluid passes a reverse flow path by the structure of the Rankine cycle system of the vehicle of this invention. It is a figure which shows the control flow of the Rankine cycle system of the vehicle of this invention. It is a figure which shows the structure of the Rankine-cycle system of the vehicle of a prior art.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a vehicle Rankine cycle system and a vehicle Rankine cycle system control method according to embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a Rankine cycle system 1 for a vehicle according to the present invention is a system including a pump 11, a boiler (evaporator) 12, a turbine (expander) 13, and a condenser 14. is there.

  The pump 11 is a device that pumps a working fluid WF (for example, water) in a liquid state to the boiler 12. The boiler 12 exchanges heat between the working fluid WF pumped from the pump 11 and the exhaust gas G of the engine (internal combustion engine) 20, so that the working fluid WF is gasified from the liquid by the heat energy (exhaust heat energy) of the exhaust gas G. It is a device that heats and evaporates. The turbine 13 is a device that is driven by a working fluid WF in a gas state that is heated and evaporated by the boiler 12, and is a device that supplies driving force by the working fluid WF to the engine 20 connected to the device. The condenser 14 heat-exchanges the working fluid WF that has passed through the turbine 13 with a cooling medium W such as engine cooling water, thereby cooling and condensing the working fluid WF from gas to liquid, and pumping the working fluid WF in a liquid state 11 is a device for sending out the data.

  That is, this Rankine cycle system 1 heats and evaporates the liquid working fluid WF pumped from the pump 11 into a gas by using the thermal energy of the exhaust gas G in the boiler 12, and then the gaseous working fluid WF. The driving force is generated in the turbine 13 by this, and the engine 20 is assisted by this driving force, and the working fluid WF that has passed through the turbine 13 is cooled and condensed by the cooling medium W by the condenser 14 to obtain the liquid working fluid WF. This is a system for delivering to the pump 11.

  More simply, the Rankine cycle system 1 is a system that recovers a part of the thermal energy of the exhaust gas G of the engine 20 and assists the engine 20 by the driving force of the turbine 13 driven by the recovered energy. is there.

  In the present embodiment, a turbine is used as the expander 13, but a device (for example, a piston) other than the turbine may be used as long as the device generates a driving force by using a gas expansion force. Further, the temperature difference between the working fluid WF and the exhaust gas G that exchange heat with the boiler 12 is about 50 ° C. to 150 ° C., although it depends on the use situation.

  Moreover, the control apparatus 30 which controls the Rankine cycle system 1 of this invention is provided. The control device 30 is a device that controls the pumping amount of the working fluid WF by the pump 11 in accordance with the operating state of the engine 20 and the like.

  By the way, in the Rankine cycle system 1X of the prior art vehicle shown in FIG. 4, the turbine 13 and the condenser 14 are further branched from the flow path of the working fluid WF between the boiler 12 and the turbine 13 via the bypass valve 51. The bypass passage 50 that joins the flow path of the working fluid WF between them is provided. When the engine 20 needs to be assisted, the control device 30 controls the bypass valve 51 so that the working fluid WF flows from the boiler 12 to the turbine 13, and there is no need to assist the engine 20. The control device 30 controls the bypass valve 51 so that the working fluid WF does not pass through the turbine 13 but passes through the bypass passage 50 so that the turbine 13 is not driven.

  On the other hand, the Rankine cycle system 1 for a vehicle according to the present invention can effectively utilize the exhaust heat energy recovered by the Rankine cycle system 1 even when the assist of the engine 20 is not required. It is a system that can improve the utilization efficiency of the recovered exhaust heat energy.

  More specifically, in the Rankine cycle system 1 for a vehicle according to the present invention, as shown in FIG. 1, the flow path is switched (switched) to the flow path of the working fluid WF between the boiler 12 and the turbine 13. An electromagnetic switching valve (first flow path switching device) 40 is provided with a second electromagnetic switching valve (second flow path switching device) 41 in the flow path of the working fluid WF between the turbine 13 and the condenser 14. Further, when the working fluid WF flows into and out of the turbine 13, the first inflow port 13 a and the second inflow port 13 b are provided, and when the first inflow port 13 a is used as the inflow port of the working fluid WF, the second inflow port When the outlet 13b is an outlet for the working fluid WF and the second inlet / outlet 13b is an inlet for the working fluid WF, the first inlet 13a is configured as an outlet for the working fluid WF. The first electromagnetic switching valve 40, the second electromagnetic switching valve 41, the first inlet / outlet port 13a and the second inlet / outlet port 13b of the turbine 13 constitute a switching mechanism that switches the direction in which the working fluid WF flows in the turbine 13 between forward and reverse. To do.

  As shown in FIG. 1, the boiler 12 and the turbine 13 are connected to each other via the first position 40 a of the first electromagnetic switching valve 40 by the control device 30, and the turbine 13 and the condenser 14 are connected to the second position. When the electromagnetic switching valve 41 is connected at the first position 41a, the working fluid WF that has passed through the first electromagnetic switching valve 40 flows in from the first inlet 13a of the turbine 13 and flows out of the second inlet 13b. The turbine 13 is rotated in the same direction as the rotation direction of the engine 20 (the turbine 13 is operated so as to generate a positive torque with respect to the engine 20) and then passed through the second electromagnetic switching valve 41. . The flow path of the working fluid WF between the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 at this time is referred to as a normal flow path OF (thick line portion in FIG. 1).

  On the other hand, as shown in FIG. 2, the boiler 12 and the turbine 13 are connected via the second position 40 b of the first electromagnetic switching valve 40 by the control device 30, and the turbine 13 and the condenser 14 are connected to the second position. When connected at the second position 41b of the electromagnetic switching valve 41, the working fluid WF that has passed through the first electromagnetic switching valve 40 flows in from the second inlet / outlet 13b of the turbine 13 and flows out of the first inlet / outlet 13a. The turbine 13 is rotated in the direction opposite to the rotation direction of the engine 20 (the turbine 13 is operated so as to generate a reverse torque with respect to the engine 20), and then the second electromagnetic switching valve 41 is passed. . The flow path of the working fluid WF between the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 at this time is referred to as a reverse flow path RF (thick line portion in FIG. 2).

  The normal flow path OF and the reverse flow path RF are switched by the control device 30 by switching the connection positions of the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 with the flow path for the working fluid WF.

  When the control device 30 uses the power of the turbine 13 to assist the engine 20, the first electromagnetic switching valve 40 and the second electromagnetic switching valve 40 are controlled by controlling the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41. The flow path for the working fluid WF between the switching valves 41 is switched to the normal flow path OF, and the working fluid WF flows in from the first inlet / outlet 13a of the turbine 13 and flows out of the second inlet / outlet 13b. The turbine 13 is controlled to rotate in the same direction as the rotation direction. That is, control for assisting the engine 20 by the rotational power of the turbine 13 is performed.

  In the present invention, when the control device 30 further uses the power of the turbine 13 to increase the braking force of the engine 20, the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 are controlled to control the first electromagnetic switching valve 40. The flow path for the working fluid WF between the switching valve 40 and the second electromagnetic switching valve 41 is switched to the reverse flow path RF, and the working fluid WF flows in from the second inlet / outlet 13b of the turbine 13 and from the first inlet / outlet 13a. Control is performed to flow out and rotate the turbine 13 in the direction opposite to the rotation direction of the engine 20. That is, the rotational power of the turbine 13 is used to inhibit the rotation of the engine 20 that rotates in the opposite direction to the turbine 13 and to increase the braking force of the engine 20.

  In summary, according to the present invention, when the control device 30 assists the engine 20, the direction in which the working fluid WF flows through the turbine 13 by the switching mechanism is set to the forward direction (forward flow path OF), and the turbine 13 is rotated forward. When the engine 20 is assisted and the braking force of the engine 20 is increased, the direction in which the working fluid WF flows through the turbine 13 is reversed (reverse flow path RF) by the switching mechanism, and the turbine 13 is rotated in the reverse direction. Control is performed to increase the braking force.

  According to this configuration, not only the power of the turbine 13 can be used for assisting the engine 20, but also the inflow / outflow ports (13b, 13a) of the working fluid WF into and out of the turbine 13 when the engine 20 assists. By switching to the opposite direction to the outlets (13a, 13b) and switching the rotation direction of the turbine 13 to the opposite direction to the rotation direction at the time of assisting the engine 20, the power of the turbine 13 is increased (the braking force of the engine brake). Can also be used.

  As a result, the utilization efficiency of the exhaust heat energy recovered from the exhaust gas G of the engine 20 can be improved.

  In the Rankine cycle system 1 for a vehicle described above, the case where the vehicle is traveling at a reduced speed is the case where the power of the turbine 13 is used to increase the braking force of the engine 20, and the vehicle is traveling at an accelerated speed or at a constant speed. Is the case where the power of the turbine 13 is used for assisting the engine 20. That is, when the vehicle is traveling at a reduced speed, the braking force of the engine 20 is increased by the power of the turbine 13, while the engine 20 is always assisted by the power of the turbine 13 when the vehicle is not traveling at a reduced speed.

  According to this configuration, when the vehicle is traveling at a reduced speed, the braking force by the foot brake can be reduced by the increase in the braking force of the engine 20 by the turbine 13. As a result, the usage frequency of the foot brake can be reduced, and the durability of the foot brake can be improved.

  Further, when the vehicle is not traveling at a reduced speed, the output of the engine 20 can be reduced by the amount of assist of the engine 20 by the turbine 13. As a result, the fuel injection amount of the engine 20 can be reduced, and the fuel consumption of the engine 20 can be improved.

  Although not shown, the configuration shown in FIG. 1 is further provided with a bypass passage 50 and a bypass valve 51 as shown in FIG. 4, and particulate collection for PM collection provided in the exhaust passage (not shown) of the engine 20 is provided. When the exhaust gas G is excessively heated and the working fluid WF exchanging heat between the exhaust gas G and the boiler 12 is excessively heated, for example, during forced PM regeneration control of a collector (not shown), the control device 30 By controlling the bypass valve 51, the working fluid WF may pass through the bypass passage 50 without passing through the turbine 13.

  By doing in this way, since the excessive thermal energy of the working fluid WF does not flow into the turbine 13, the durability of the turbine 13 can be improved.

  The determination as to whether or not the exhaust gas G and the working fluid WF are excessively heated includes, for example, a temperature sensor (not shown) provided in the exhaust passage or the working fluid flow path, and a detection value of the temperature sensor. This is performed depending on whether or not becomes equal to or greater than a set threshold value (optimal value set by experiment etc.).

  Next, a control method of the vehicle Rankine cycle system of the present invention will be described based on the control flow shown in FIG. The control flow of FIG. 3 is shown as a control flow that is called from the advanced control flow and starts whenever a preset control time elapses during operation of the engine 20.

  When the control flow of FIG. 3 starts, it is determined in step S10 whether or not the vehicle is traveling at a reduced speed. This determination is performed, for example, according to whether the amount of change per unit time of the detected value of a vehicle speed sensor (not shown) provided in the vehicle is positive or negative. In step S10, when the vehicle is traveling at a reduced speed (YES), the process proceeds to step S20. In step S20, the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 are controlled, and the first electromagnetic switching is performed. The flow path for the working fluid WF between the switching valve 40 and the second electromagnetic switching valve 41 is switched to the reverse flow path RF, and the working fluid WF flows in from the second inlet / outlet 13b of the turbine 13 and from the first inlet / outlet 13a. The engine 13 flows out, rotates the turbine 13 in the direction opposite to the rotation direction of the engine 20, and inhibits the rotation of the engine 20 by the rotational power of the turbine 13 to increase the braking force of the engine 20. After executing the control in step S20, the process proceeds to return, and this control flow ends.

  On the other hand, when the vehicle is not decelerating at step S10 (NO), the process proceeds to step S30. At step S30, the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 are controlled, and the first electromagnetic switching valve 41 is controlled. The flow path for the working fluid WF between the first electromagnetic switching valve 40 and the second electromagnetic switching valve 41 is switched to the normal flow path OF, and the working fluid WF flows in from the first inlet / outlet 13a of the turbine 13 and flows into the second inlet. Control that assists the engine 20 with the rotational power of the turbine 13 is performed by flowing out of the outlet 13b and rotating the turbine 13 in the same direction as the rotational direction of the engine 20. After executing the control in step S30, the process proceeds to return, and this control flow ends.

  From the above, the vehicle Rankine cycle system control method of the present invention based on the vehicle Rankine cycle system 1 of the present invention is an evaporator 12 that heats and evaporates the working fluid WF from liquid to gas by exhaust heat of the engine 20. And an expander 13 connected to the engine 20 and driven by the working fluid WF heated and evaporated by the evaporator 12, and a condenser 14 for cooling and condensing the working fluid WF that has passed through the expander 13 from gas to liquid. In the vehicle Rankine cycle system control method configured to switch the flow direction of the working fluid WF in the expander 13 between forward and reverse, when the engine 20 is assisted, the working fluid WF is expanded by the switching mechanism. The engine 20 is assisted by rotating the expander 13 forward with the direction of flow through the expander 13 in the positive direction, and braking of the engine 20 A method of increasing the braking force of the engine 20 by reversely rotating the expander 13 with the switching mechanism flowing in the reverse direction of the working fluid WF by the switching mechanism. Become.

  According to the vehicle Rankine cycle system 1 and the vehicle Rankine cycle system control method of the present invention, the utilization efficiency of exhaust heat energy recovered from the exhaust gas G of the engine 20 can be improved.

  1, 2, and 4, the engine 20 and the boiler 12 are directly connected, but actually, an exhaust passage that leads from the engine 20 to the atmosphere via an exhaust gas purification processing device (not shown) or the like. It branches from the (exhaust pipe) and is connected to the boiler 12.

1, 1X Rankine cycle system for vehicles 12 Boiler (evaporator)
13 Turbine (expander)
13a 1st inlet / outlet 13b 2nd inlet / outlet 14 Condenser 20 Engine (internal combustion engine)
30 Control device 40 First electromagnetic switching valve (first flow path switching device)
41 Second electromagnetic switching valve (second flow path switching device)
G Exhaust gas WF Working fluid

Claims (4)

An evaporator that heats and evaporates the working fluid from a liquid to a gas by exhaust heat of the internal combustion engine, an expander that is connected to the internal combustion engine and is driven by the working fluid heated and evaporated by the evaporator, and passes through the expander In a Rankine cycle system for a vehicle configured by a condenser that cools and condenses the working fluid from gas to liquid, and a control device,
A switching mechanism for switching the direction in which the working fluid flows in the expander to forward and reverse, and
When the control device assists the internal combustion engine, the switching mechanism assists the internal combustion engine by rotating the expander forward by setting the direction in which the working fluid flows through the expander to be a positive direction. When the braking force of the internal combustion engine is increased, the switching mechanism performs control to increase the braking force of the internal combustion engine by reversely rotating the expander with the direction in which the working fluid flows through the expander reversed. The Rankine cycle system of the vehicle that has been. The switching mechanism switches the first flow path switching device to the working fluid flow path between the evaporator and the expander, and switches the second flow path to the working fluid flow path between the expander and the condenser. A first inflow outlet and a second inflow outlet through which the working fluid flows in and out of the expander,
The control device is
When the power of the expander is used for assisting the internal combustion engine, the first fluid path switching device and the second fluid path switching device are controlled so that the working fluid flows in from the first inlet / outlet of the expander. And outflowing from the second inlet / outlet of the expander, and performing control to rotate the expander in the same direction as the rotation direction of the internal combustion engine,
When the power of the expander is used to increase the braking force of the internal combustion engine, the first flow path switching device and the second flow path switching device are controlled to supply the working fluid to the second of the expander. 2. The vehicle Rankine according to claim 1, wherein control is performed to control the rotation of the expander in a direction opposite to a rotation direction of the internal combustion engine, flowing in from an inflow / outflow port and flowing out of the first inflow / outflow port. Cycle system.   When the vehicle is traveling at a reduced speed, the power of the expander is used for increasing the braking force of the internal combustion engine, and when the vehicle is traveling at an accelerated speed or at a constant speed, the expander is used. The Rankine cycle system for a vehicle according to claim 1 or 2, wherein the motive power is used for assisting the internal combustion engine. An evaporator that heats and evaporates the working fluid from a liquid to a gas by exhaust heat of the internal combustion engine, an expander that is connected to the internal combustion engine and is driven by the working fluid heated and evaporated by the evaporator, and passes through the expander In a method for controlling a Rankine cycle system for a vehicle, comprising: a condenser that cools and condenses the working fluid from gas to liquid; and a switching mechanism that switches a direction in which the working fluid flows in the expander forward and backward.
When assisting the internal combustion engine, the switching mechanism assists the internal combustion engine by rotating the expander forward with the direction in which the working fluid flows through the expander as a positive direction,
When increasing the braking force of the internal combustion engine, the switching mechanism performs control to increase the braking force of the internal combustion engine by rotating the expander in the reverse direction with the working fluid flowing through the expander in the reverse direction. A control method for a Rankine cycle system for a vehicle.

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