JP2011214480A - Waste heat using device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat using device of an internal combustion engine, equipped with a Rankine cycle capable of transmitting the rotation driving force generated at an expander to the internal combustion engine through a belt or the like and efficiently operating the Rankine cycle according to the operation state of the internal combustion engine while inhibiting adverse affection to the belt or the like and the expander.SOLUTION: A control means (40) controls a power transmission means (32), which connects and disconnects a transmission path (30) of the rotation driving force between the internal combustion engine (2) and the expander (20), into a connecting state and a disconnecting state according to rotation speed of the internal combustion engine (2) detected by an engine rotation speed detection means (48).

Description

  The present invention relates to a waste heat utilization apparatus for an internal combustion engine, and more particularly, to a waste heat utilization apparatus suitable for recovering and utilizing the waste heat of an internal combustion engine of a vehicle.

  This kind of waste heat utilization device is an evaporator that heats and evaporates the working fluid by the waste heat of the internal combustion engine in the circulation path of the refrigerant as the working fluid, and expands the working fluid that passes through the evaporator to drive rotation. An expander that generates a force, a driven transmission device to which a rotational driving force generated by the expander is transmitted, a condenser that condenses the working fluid that passes through the expander, and a working fluid that passes through the condenser It has a Rankine system in which pumps sent to the evaporator are sequentially inserted.

In recent years, Rankine systems have been developed in which the Rankine cycle is mounted on a vehicle and the power transmission device is an internal combustion engine, and the rotational driving force generated by the expander assists the rotational driving force of the internal combustion engine. (Patent Document 1).
In particular, recently, the rotating shaft of the expander and the crankshaft of the internal combustion engine are connected by a belt or a gear set (hereinafter referred to as a belt or the like), and the rotational driving force generated by the expander is transmitted to the internal combustion engine via the belt or the like. A Rankine system has been developed that directly assists the rotational driving force of an internal combustion engine in such a way that it is transmitted.

JP-A-57-99222

By the way, when the rotational driving force generated by the expander as described above is transmitted to the internal combustion engine via a belt or the like, the rotational speed of the internal combustion engine is extremely low (including the stop of the internal combustion engine) during the operation of the Rankine system. ), Only the rotational driving force of the expander is transmitted to the belt or the like, and there is a problem that an excessive load acts on the belt or the like and the belt or the like is easily damaged.
Also, for example, when starting the Rankine system, if the rotational speed on the expander side is smaller than the rotational speed on the internal combustion engine side, the expander and thus the Rankine system will be a load on the internal combustion engine, which will adversely affect the expander. There is also a problem.

  The present invention has been made in view of such a problem, and includes a Rankine cycle capable of transmitting a rotational driving force generated by an expander to an internal combustion engine via a belt or the like, and the Rankine cycle according to the operating state of the internal combustion engine. It is an object of the present invention to provide an internal combustion engine waste heat utilization device capable of operating a system efficiently while suppressing adverse effects on a belt or the like and an expander.

  In order to achieve the above object, an internal combustion engine waste heat utilization apparatus according to claim 1 is provided with an evaporator that heats and evaporates the working fluid by the waste heat of the internal combustion engine in the working fluid circulation path, and passes through the evaporator. An expander that expands the working fluid and transmits a rotational driving force to the internal combustion engine, a condenser that condenses the working fluid via the expander, and a pump that sends the working fluid via the condenser to the evaporator In a waste heat utilization apparatus for an internal combustion engine having a Rankine system comprising a Rankine cycle circuit sequentially provided, the rotational drive between the internal combustion engine and the expander is interposed between the internal combustion engine and the expander Power transmission means for connecting and disconnecting the force transmission path, engine rotation speed detection means for detecting the rotation speed of the internal combustion engine, and the engine rotation speed detection means according to the rotation speed of the internal combustion engine detected by the engine rotation speed detection means Power transmission hand And a controlling means for controlling the connected state and the disconnected state.

According to a second aspect of the present invention, there is provided a waste heat utilization apparatus for an internal combustion engine according to the first aspect, wherein when the rotational speed of the internal combustion engine detected by the engine rotational speed detection means is smaller than a predetermined rotational speed, the power transmission means Is controlled to a cut state.
The internal combustion engine waste heat utilization apparatus according to claim 3 is characterized in that, in claim 2, the predetermined rotational speed is smaller than an idle rotational speed of the internal combustion engine.

  The waste heat utilization apparatus for an internal combustion engine according to claim 4 further comprises expander rotation speed detection means for detecting the rotation speed of the expander according to any one of claims 1 to 3, wherein the control means is the expander. The rotational speed in the power transmission means based on the rotational speed of the expander detected by the rotational speed detection means is smaller than the rotational speed in the power transmission means based on the rotational speed of the internal combustion engine detected by the engine rotational speed detection means. In some cases, the power transmission means is held in a disconnected state.

According to the waste heat utilization apparatus for an internal combustion engine according to claim 1, the Rankine system expander assists the internal combustion engine by transmitting a rotational driving force to the internal combustion engine. The power transmission means for connecting and disconnecting the transmission path of the rotational driving force between the two is controlled in a connected state and a disconnected state in accordance with the rotational speed of the internal combustion engine.
As a result, during operation of the Rankine system, the power transmission means can be freely controlled according to the rotational speed of the internal combustion engine according to the rotational speed of the internal combustion engine. As a result, the operation of the Rankine system can be controlled according to the rotational speed of the internal combustion engine. Control can be performed efficiently without adversely affecting the expander.

  According to the waste heat utilization apparatus for an internal combustion engine according to claim 2, when the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed, the power transmission means is controlled to be in a disconnected state, so the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed. In particular, when the internal combustion engine is stopped, if the operation of the Rankine system is continued, the belt or the like may be deteriorated due to the overload of the rotational driving force of the expander. Such deterioration of the belt or the like can be prevented.

  According to the waste heat utilization device for an internal combustion engine according to claim 3, since the predetermined rotational speed is a value smaller than the idle rotational speed of the internal combustion engine, the power transmission means can be controlled to be disconnected immediately before the internal combustion engine stops, The load on the belt or the like can be suppressed. Further, since the power transmission means is not frequently connected / disconnected during idling operation, energy loss can be eliminated, and the Rankine system can be satisfactorily operated even during idling operation. Thereby, the Rankine system can be operated efficiently, and the internal combustion engine can be favorably assisted by the Rankine system.

  According to the waste heat utilization apparatus for an internal combustion engine according to claim 4, when the rotational speed in the power transmission means based on the rotational speed of the internal combustion engine is greater than the rotational speed in the power transmission means based on the rotational speed of the expander, the power transmission means is Since it is held in a disconnected state, that is, in other words, if the rotational speed of the power transmission means based on the rotational speed of the expander does not exceed the rotational speed of the power transmission means based on the rotational speed of the internal combustion engine, the power transmission means is brought into the connected state. Therefore, for example, when starting up the Rankine system, an expander with a low rotational speed can be prevented from unnecessarily loading the internal combustion engine, and damage to the expander due to excessive operation of the internal combustion engine can be prevented. Can do.

1 is a schematic diagram showing a waste heat utilization apparatus for an internal combustion engine according to a first embodiment of the present invention. It is a flowchart which shows the control routine of the pump abnormal time control which concerns on 1st Example. It is a flowchart which shows the control routine of the control at the time of engine speed fall which concerns on 1st Example. It is a flowchart which shows the control routine of the control at the time of Rankine system starting based on 1st Example. It is a schematic diagram which shows the waste heat utilization apparatus of the internal combustion engine which concerns on 2nd Example of this invention. It is a flowchart which shows the control routine of the pump abnormal time control which concerns on 2nd Example. It is a flowchart which shows the control routine of the control at the time of engine speed fall which concerns on 2nd Example. It is a flowchart which shows the control routine of Rankine system starting time control which concerns on 2nd Example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the first embodiment will be described.
The internal combustion engine waste heat utilization apparatus according to the first embodiment of the present invention is mounted on, for example, a vehicle, and as shown in the schematic diagram of FIG. 1, a cooling water circuit 4 that cools the engine 2 of the vehicle, and the engine 2. And a Rankine system comprising a Rankine cycle circuit (hereinafter referred to as an RC circuit) 6 for recovering the waste heat of the engine.

The cooling water circuit 4 forms a closed circuit in which an evaporator 10, a radiator 12, a thermostat 14, and a water pump 16 are interposed in order from the cooling water flow direction in a cooling water circulation path 5 extending from the engine 2. is doing.
The evaporator 10 exchanges heat between the cooling water of the cooling water circuit 4 and the refrigerant of the RC circuit 6, thereby using the cooling water heated by the engine 2, that is, warm water as a heat medium, and the waste heat of the engine 2 as the RC circuit 6. End to end and collect. On the other hand, the cooling water absorbed by the refrigerant after passing through the evaporator 10 becomes warm water heated again by cooling the engine 2.

The radiator 12 is arranged in series with the evaporator 10 and further cools the cooling water that has passed through the evaporator 10 and has been absorbed by the refrigerant by heat exchange with the outside air.
The thermostat 14 is a mechanical three-way valve that controls the amount of cooling water that is passed to the radiator 12 according to the cooling water temperature, and has two inlet ports and one outlet port. The two inlet ports are connected to a flow path 5a extending from the radiator 12 and a bypass path 5c connected to bypass the radiator 12 from the flow path 5b between the evaporator 10 and the radiator 12, respectively. ing. Thereby, the amount of cooling water passed to the radiator 12 is increased or decreased according to the cooling water temperature, and the engine 2 is prevented from being overheated or overcooled.

The water pump 16 is attached to the engine 2 and is driven according to the rotational speed of the engine 2 to circulate the cooling water in the cooling water circuit 4.
On the other hand, the RC circuit 6 is connected to the refrigerant circulation path 7 in order from the refrigerant flow direction, the evaporator 10, the electromagnetic expander inlet valve 18, the expander 20, the regenerator 22, the Rankine cycle condenser (condenser, hereinafter). (Referred to as an RC capacitor) 24, a gas-liquid separator 26, a refrigerant pump 28, and a check valve 29 are arranged in this order to form a closed circuit.

The expander inlet valve 18 is, for example, a normally open solenoid valve, and is configured to supply a valve closing signal when the Rankine system is stopped.
The expander 20 is a fluid device that expands the refrigerant heated to the superheated steam state by the evaporator 10 and generates a rotational driving force by the flow of the refrigerant, and assists the rotational driving of the engine 2. It is configured. Specifically, the pulley 21a joined to the drive shaft 21 of the expander 20 is connected to the pulley 3a joined to the crankshaft 3 of the engine 2 via an endless belt (transmission path) 30 so as to be able to rotate synchronously. Has been.

An electromagnetic clutch (power transmission means) 32 is interposed on the drive shaft 21 of the expander 20, and the drive shaft 21 of the expander 20, the belt 30, and thus the engine 2 are connected by operating the electromagnetic clutch 32. It is possible to connect and disconnect the rotational drive force transmission path between the crankshafts 3.
The regenerator 22 is an internal heat exchanger of the RC circuit 6 that heats the refrigerant at the inlet of the evaporator 10 with the refrigerant at the outlet of the expander 20, and positively transfers the heat amount at the outlet of the expander 20 to the inlet side of the evaporator 10. By supplying, the recovered energy in the RC circuit 6 is increased. The regenerator 22 is not essential and may be omitted.

The RC condenser 24 is a heat exchanger that condenses and liquefies the refrigerant that has passed through the regenerator 22, and is cooled by the cooling fan 25.
The gas-liquid separator 26 is a receiver that separates the refrigerant condensed by the RC capacitor 24 into two layers of gas and liquid, and only the liquid refrigerant separated here flows out to the refrigerant pump 28 side.
The refrigerant pump 28 is an electric pump that is driven based on a signal that is input to the drive unit according to the operating state of the engine 2 and the like, and pumps the liquid refrigerant that has flowed out of the gas-liquid separator 26 to the evaporator 10 side. Circulate.

The check valve 29 is disposed in the circulation path 7 so as to allow the refrigerant flow from the refrigerant pump 28 to the expander 20 while blocking the refrigerant flow from the reverse expander 20 to the refrigerant pump 28. .
In the circulation path 7 of the RC circuit 6, a pressure sensor 42 is disposed on the upstream side of the expander 20, and a pressure sensor 44 is disposed on the downstream side.
The drive shaft 21 of the expander 20 is provided with an expander rotation speed sensor (expander rotation speed detection means) 46 that detects the rotation speed Nb of the expander 20. An engine rotation speed sensor (engine rotation speed detection means) 48 for detecting the rotation speed Ne is provided.

  The electronic control unit (ECU, control means) 40 is a control device that performs various controls of the waste heat utilization device of the internal combustion engine according to the present invention in addition to the control of the engine 2. , 44, various sensors such as an expander rotational speed sensor 46 and an engine rotational speed sensor 48 are electrically connected, and various devices such as the expander inlet valve 18, the refrigerant pump 28, and the electromagnetic clutch 32 are provided on the output side. Is connected.

Hereinafter, the operation of the waste heat utilization apparatus for an internal combustion engine according to the first embodiment of the present invention configured as described above, that is, the control contents of the expander inlet valve 18 and the electromagnetic clutch 32 will be described.
[When pump is abnormal]
Referring to FIG. 2, a control routine of the pump abnormal time control executed by the ECU 40 when the refrigerant pump 28 according to the first embodiment of the present invention is abnormal is shown in a flowchart, which will be described below.

  In step S10, it is determined whether or not the Rankine system is operating. For example, a valve opening signal is supplied from the ECU 40 to the expander inlet valve 18, and it is determined whether or not the refrigerant is in a state where it can flow through the circulation path 7. If the determination result is false (No) and the Rankine system is not in operation, the determination in step S10 is repeated. If the determination result is true (Yes) and the Rankine system is in operation, the process proceeds to step S12. . In determining whether or not the Rankine system is in operation, it may be determined that the Rankine system is in operation if the high-pressure or high-low pressure difference between the Rankine system is equal to or greater than a predetermined value.

  In step S12, it is determined whether or not the refrigerant pump 28 has an abnormality. Here, for example, based on the pressure information of the refrigerant from the pressure sensors 42 and 44, it is determined whether or not the refrigerant pressure difference between the upstream side and the downstream side of the expander 20 has decreased to less than a predetermined value. If the determination result is false (No), the determination in step S12 is repeated. If the determination result is true (Yes) and it is determined that the pressure difference of the refrigerant has decreased below a predetermined value, the refrigerant pump It can be determined that there is an abnormality in 28 and the refrigerant does not sufficiently circulate through the circulation path 7 and the expander 20 does not function normally, and the process proceeds to step S14.

In step S14, in response to the determination in step S12 that the refrigerant pump 28 is abnormal, the operation of the refrigerant pump 28 is stopped.
In step S16, in order to stop the operation of the Rankine system, a valve closing signal is supplied to the expander inlet valve 18 to shut off the valve opening signal to the expander inlet valve 18, and the expander inlet valve 18 is closed.
In step S18, the connection signal to the electromagnetic clutch 32 is cut off, and the electromagnetic clutch 32 is brought into a disconnected state. As a result, the connection between the drive shaft 21 of the expander 20 and the belt 30 and thus the crankshaft 3 of the engine 2 is released.

  Thus, during operation of the Rankine system, the electromagnetic clutch 32 is disconnected and the connection between the expander 20 and the engine 2 is released under a situation where the refrigerant pump 28 is abnormal and the refrigerant does not circulate sufficiently through the circulation path 7. Therefore, the expander 20 that does not function normally and therefore the Rankine cycle can be prevented from being unnecessarily loaded on the engine 2, and the expander 20 can be prevented from being forced to rotate by the engine 2 when the refrigerant is insufficient. 20 damage can be prevented.

Since the expander inlet valve 18 is closed in step S16 before the electromagnetic clutch 32 is disengaged in step S18, the refrigerant whose temperature has been raised by the evaporator 10 and has become relatively high pressure is reversed. It can be confined between the stop valve 29 and the expander inlet valve 18. Thereby, even if it is a case where the electromagnetic clutch 32 is made into a cutting | disconnection state after that, it is prevented that the expansion machine 20 with which the connection with the engine 2 was cancelled | released and rotated freely with the pressure of a refrigerant | coolant, Vibration and noise generated by the expander 20 can be prevented so as not to cause discomfort to the vehicle occupant, and damage to the expander 20 can also be prevented.
[When engine speed decreases]
Referring to FIG. 3, a control routine of the control at the time of lowering of the engine rotation speed in the engine 2 according to the first embodiment of the present invention executed by the ECU 40 is shown in a flowchart, and will be described along the flowchart.

In step S20, as in the case of the pump abnormality, it is determined whether or not the Rankine system is operating. If the determination result is false (No) and the Rankine system is not operating, the determination in step S20 is repeated. If the determination result is true (Yes) and it is determined that the Rankine system is operating, the process proceeds to step S22.
In step S22, it is determined whether or not the engine rotational speed Ne detected by the engine rotational speed sensor 48 is less than a predetermined rotational speed N1. Here, the predetermined rotational speed N1 is a value (for example, 100 rpm) lower than the idle rotational speed. If the determination result is false (No) and the engine rotational speed Ne is determined to be equal to or higher than the predetermined rotational speed, the determination in step S22 is repeated, and the determination result is true (Yes) and the engine rotational speed Ne is less than the predetermined rotational speed. If it is determined, the process proceeds to step S24.

In step S24, in order to stop the operation of the Rankine system, the valve opening signal to the expander inlet valve 18 is shut off, and the expander inlet valve 18 is closed.
In step S26, the connection signal to the electromagnetic clutch 32 is cut off, and the electromagnetic clutch 32 is brought into a disconnected state. As a result, the connection between the drive shaft 21 of the expander 20 and the belt 30 and thus the crankshaft 3 of the engine 2 is released.

Further, in step S28, the operation of the refrigerant pump 28 is stopped.
Thus, during operation of the Rankine system, when the engine rotational speed Ne is less than the predetermined rotational speed N1, the electromagnetic clutch 32 is disconnected and the connection between the expander 20 and the engine 2 is released. Even when the output of the cycle is large and the rotational driving force of the expander 20 becomes larger than the rotational driving force of the engine 2, the rotational driving force of the expander 20 is not unnecessarily transmitted to the belt 30. And deterioration of the belt 30 can be prevented.

In particular, when the engine 2 is stopped, the belt 30 can be prevented from being forcibly pushed or pulled by the rotational driving force of the expander 20, and the belt 30 can be prevented from being damaged by the rotational driving force of the expander 20. Can do.
Here, the predetermined rotational speed N1 is set to a value lower than the idle rotational speed (for example, 100 rpm). In this way, if the electromagnetic clutch 32 is disengaged after the engine 2 is completely stopped, the belt Although a large load is applied to the belt 30 to some extent, the load on the belt 30 can be suppressed by disconnecting the electromagnetic clutch 32 immediately before the engine 2 stops.

  Further, if the predetermined rotational speed N1 is set to a value lower than the idle rotational speed (for example, 100 rpm) as described above, if the predetermined rotational speed N1 is equal to or higher than the idle rotational speed, the frequency of idling operation is high. For this reason, the electromagnetic clutch 32 must be frequently connected and disconnected during operation of the Rankine system, which causes energy loss. However, such energy loss can be eliminated and even during idle operation. Rankine system can be operated well. Accordingly, the Rankine system can be operated efficiently, and the engine 2 can be favorably assisted by the Rankine system.

Further, as in the case of pump abnormality, the expander inlet valve 18 is closed in step S24 before the electromagnetic clutch 32 is disconnected in step S26. The high pressure refrigerant that is pressed by the pump 28 can be confined between the check valve 29 and the expander inlet valve 18. Therefore, it is possible to prevent the expander 20 that has been released from the connection with the engine 2 from being freely rotated by the pressure of the refrigerant, and to prevent the expander 20 from being damaged.
[When Rankine system starts]
Referring to FIG. 4, a control routine of the Rankine system start-up control according to the first embodiment of the present invention, which is executed by the ECU 40, is shown in a flowchart, and will be described along the flowchart.

  At the start of the Rankine system, as shown in FIG. 4, first, in step S30, based on the refrigerant pressure information from the pressure sensors 42 and 44, the refrigerant pressure difference between the upstream side and the downstream side of the expander 20 is predetermined. It is determined whether or not it is greater than or equal to the value. That is, it is determined whether or not the pressure of the refrigerant confined between the check valve 29 and the expander inlet valve 18 just after the operation of the Rankine system is stopped is sufficiently high. If the determination result is false (No) and the refrigerant pressure difference between the upstream side and the downstream side is less than a predetermined value, the process proceeds to step S32, and Rankine system initial startup control is performed.

At the time of initial startup of the Rankine system, in step S32, a valve opening signal is supplied to the expander inlet valve 18, and the expander inlet valve 18 is opened. In step S34, the operation of the refrigerant pump 28 is started.
In step S36, the rotational speed Nb of the expander 20 detected by the expander rotational speed sensor 46 is read. In step S38, it is determined whether or not the rotational speed Nb is higher than the rotational speed of the pulley 21a by the engine 2 (pulley rotational speed: engine rotational speed Ne x pulley ratio of the pulley 21a). If the determination result is false (No) and the rotational speed Nb is equal to or lower than the rotational speed of the pulley 21a, the expander 20 becomes a load on the engine 2 when the electromagnetic clutch 32 is connected. The determination in S38 is repeated.

On the other hand, if the determination result in step S38 is true (Yes) and the rotational speed Nb is greater than the rotational speed of the pulley 21a, it can be determined that the expander 20 will not become a load on the engine 2, and the process proceeds to step S40. The electromagnetic clutch 32 is connected.
As described above, at the time of initial startup of the Rankine system, the electromagnetic clutch 32 is opened only when the rotational speed Nb is higher than the rotational speed of the pulley 21a after opening the expander inlet valve 18 and starting the operation of the refrigerant pump 28. The Rankine system can be activated so that the expander 20 does not become a load on the engine 2, and the expander 20 is not forced to rotate by the engine 2 when the refrigerant is insufficient. Damage to the expander 20 can be prevented.

On the other hand, if the determination result in step S30 is true (Yes) and the refrigerant pressure difference between the upstream side and the downstream side is equal to or greater than a predetermined value, the Rankine system immediately after the operation of the Rankine system is temporarily stopped. It can be considered that the system is restarted, and the process proceeds to step S42, where Rankine system restart control is performed.
At the time of restarting the Rankine system, the electromagnetic clutch 32 is connected in step S42, and then the expander inlet valve 18 is opened in step S44. In step S46, the operation of the refrigerant pump 28 is started.

  That is, when the Rankine system is restarted, the temperature of the evaporator 10 is raised during operation of the Rankine system and the refrigerant pressed by the refrigerant pump 28 is interposed between the check valve 29 and the expander inlet valve 18 as described above. When the expander inlet valve 18 is opened, the expander 20 can be quickly operated with the high-pressure refrigerant. As a result, the Rankine system can be started efficiently and smoothly to assist the engine 2 satisfactorily.

Here, in step S36, the rotational speed Nb of the expander 20 is detected by the expander rotational speed sensor 46, but the rotational speed Nb is an estimated value based on the following functions (1) to (3). It may be.
Nb = f (pressure difference between the upstream side and the downstream side of the refrigerant expander 20) (1)
Nb = f (refrigerant flow rate) (2)
Nb = f (elapsed time since the refrigerant pump was operated) (3)
Next, a second embodiment will be described.

The waste heat utilization apparatus for an internal combustion engine according to the second embodiment of the present invention is integrated with the expander 20 instead of the electric refrigerant pump 28 of the first embodiment as shown in the schematic diagram of FIG. The difference from the first embodiment is that a refrigerant pump 28 'that rotates synchronously with the expander 20 is provided. Hereinafter, description of the same parts as those of the first embodiment will be omitted, and different parts will be described.
As shown in FIG. 5, the drive shaft 21 of the expander 20 passes through the expander 20, and a refrigerant pump 28 ′ can rotate synchronously with the expander 20 at the tip of the drive shaft 21 opposite to the pulley 21 a. It is connected. That is, the expander 20 and the refrigerant pump 28 'constitute a pump integrated expander.

The operation of the waste heat utilization apparatus for an internal combustion engine according to the second embodiment of the present invention thus configured, that is, the control contents of the expander inlet valve 18 and the electromagnetic clutch 32 will be described below.
[When pump is abnormal]
Referring to FIG. 6, a control routine of the pump abnormal time control executed by the ECU 40 when the refrigerant pump 28 ′ according to the second embodiment of the present invention is abnormal is shown in a flowchart, and will be described along the flowchart. . The description of the same steps as those in the first embodiment will be simplified.

In step S110, it is determined whether or not the Rankine system is operating. If the determination result is false (No) and the Rankine system is not in operation, the determination in step S110 is repeated. If the determination result is true (Yes) and the Rankine system is in operation, the process proceeds to step S112. .
In step S112, it is determined whether or not there is an abnormality in the refrigerant pump 28 '. If the determination result is false (No), the determination in step S112 is repeated, and if the determination result is true (Yes) and it is determined that the refrigerant pressure difference has decreased below a predetermined value, the refrigerant pump It is determined that there is an abnormality in 28 ', and the process proceeds to step S116.

In step S116, the expander inlet valve 18 is closed to stop the operation of the Rankine system. In step S118, the electromagnetic clutch 32 is disengaged. As a result, the connection between the drive shaft 21 of the expander 20 and the belt 30 and thus the crankshaft 3 of the engine 2 is released.
As described above, even when the pump-integrated expander is used, the electromagnetic clutch 32 is not operated in a situation where the refrigerant pump 28 'is abnormal during operation of the Rankine system and the refrigerant does not sufficiently circulate through the circulation path 7. By disconnecting and releasing the connection between the expander 20 and the refrigerant pump 28 'and the engine 2, it is possible to prevent the expander 20 and the refrigerant pump 28' and therefore the Rankine cycle that do not function normally from becoming an unnecessary load on the engine 2. In addition, it is possible to prevent the expander 20 from being damaged by forcibly rotating the expander 20 with the engine 2 in a state where the refrigerant is insufficient.

Since the expander inlet valve 18 is closed in step S116 before the electromagnetic clutch 32 is disengaged in step S118, the refrigerant whose temperature has been raised by the evaporator 10 and has become relatively high pressure is reversed. It can be confined between the stop valve 29 and the expander inlet valve 18. Thereby, even if it is a case where the electromagnetic clutch 32 is made into a cutting | disconnection state after that, it is prevented that the expansion machine 20 with which the connection with the engine 2 was cancelled | released and rotated freely with the pressure of a refrigerant | coolant, Vibration and noise generated by the expander 20 can be prevented so as not to cause discomfort to the vehicle occupant, and damage to the expander 20 can also be prevented.
[When engine speed decreases]
Referring to FIG. 7, a control routine for the engine speed reduction control in the engine 2 according to the second embodiment of the present invention, which is executed by the ECU 40, is shown in a flowchart, and will be described along the flowchart. In this case as well, the description of the same steps as in the first embodiment will be simplified.

In step S120, as in the case of the pump abnormality, it is determined whether or not the Rankine system is operating. If the determination result is false (No) and the Rankine system is not operating, the determination in step S120 is repeated. If the determination result is true (Yes) and it is determined that the Rankine system is operating, the process proceeds to step S122.
In step S122, it is determined whether or not the engine rotational speed Ne detected by the engine rotational speed sensor 48 is less than a predetermined rotational speed N1. If the determination result is false (No) and the engine rotation speed Ne is determined to be equal to or higher than the predetermined rotation speed, the determination in step S122 is repeated, and the determination result is true (Yes) and the engine rotation speed Ne is less than the predetermined rotation speed. If it is determined, the process proceeds to step S124.

  In step S124, in order to stop the operation of the Rankine system, the valve opening signal to the expander inlet valve 18 is shut off, and the expander inlet valve 18 is closed. In step S126, the connection signal to the electromagnetic clutch 32 is cut off, and the electromagnetic clutch 32 is brought into a disconnected state. As a result, the connection between the drive shaft 21 of the expander 20 and the belt 30 and thus the crankshaft 3 of the engine 2 is released.

  Thus, even when the pump-integrated expander is used, when the engine rotational speed Ne is less than the predetermined rotational speed N1 during operation of the Rankine system, the electromagnetic clutch 32 is disconnected and the expander 20 is disconnected. Since the connection between the engine 2 and the engine 2 is released, for example, when the output of the Rankine cycle is large and the rotational driving force of the expander 20 becomes larger than the rotational driving force of the engine 2, the rotational driving force of the expander 20 Can be prevented from being transmitted to the belt 30 unnecessarily, and deterioration of the belt 30 can be prevented.

In particular, when the engine 2 is stopped, the belt 30 can be prevented from being forcibly pushed or pulled by the rotational driving force of the expander 20, and the belt 30 can be prevented from being damaged by the rotational driving force of the expander 20. Can do.
Further, as in the case of the pump abnormality, the expander inlet valve 18 is closed in step S124 before the electromagnetic clutch 32 is disconnected in step S126, so that the connection with the engine 2 is released and free. It is prevented that the expander 20 that has become abruptly rotated by the pressure of the refrigerant, and it is possible to prevent the expander 20 from being damaged.
[When Rankine system starts]
Referring to FIG. 8, a control routine for Rankin system start-up control according to the second embodiment of the present invention, which is executed by the ECU 40, is shown in a flowchart, which will be described below. In this case as well, the description of the same steps as in the first embodiment will be simplified.

When the Rankine system is started, as shown in FIG. 8, it is determined in step S130 whether or not the refrigerant pressure difference is greater than or equal to a predetermined value between the upstream side and the downstream side of the expander 20. If the determination result is false (No) and the refrigerant pressure difference between the upstream side and the downstream side is less than a predetermined value, the process proceeds to step S132, and Rankine system initial startup control is performed.
At the initial startup of the Rankine system, in step S132, a valve opening signal is supplied to the expander inlet valve 18, and after the expander inlet valve 18 is opened, the process proceeds to step S140, and the electromagnetic clutch 32 is connected.

As described above, when the pump-integrated expander is used, the electromagnetic clutch 32 is connected after the expander inlet valve 18 is opened when the Rankine system is initially started. The Rankine system can be started smoothly while operating the refrigerant pump 28 'with the driving force.
On the other hand, if the determination result in step S130 is true (Yes) and the refrigerant pressure difference between the upstream side and the downstream side is equal to or greater than a predetermined value, the Rankine system immediately after the operation of the Rankine system is temporarily stopped. It can be considered that the system is restarted, and the process proceeds to step S142 to perform control when the Rankine system is restarted.

When the Rankine system is restarted, the expander inlet valve 18 is opened in step S144 after the electromagnetic clutch 32 is connected in step S142.
That is, even when the pump-integrated expander is used, when the Rankine system is restarted, as described above, the temperature is raised by the evaporator 10 during operation of the Rankine system and the refrigerant pressed by the refrigerant pump 28 ' The high pressure is confined between the check valve 29 and the expander inlet valve 18, and when the expander inlet valve 18 is opened, the expander 20 can be quickly operated with this high pressure refrigerant. . As a result, the Rankine system can be started efficiently and smoothly to assist the engine 2 satisfactorily.

This is the end of the description of the embodiment of the present invention, but the present invention is not limited to the above embodiment.
For example, in the above embodiment, in both the first example and the second example, whether or not the refrigerant pumps 28 and 28 ′ are abnormal is determined based on, for example, the refrigerant pressure information from the pressure sensors 42 and 44. 20 is determined based on whether or not the refrigerant pressure difference between the upstream side and the downstream side of the compressor 20 has decreased below a predetermined value. However, only the refrigerant pressure on the upstream side of the expander 20, that is, the high-pressure side refrigerant, is determined. Alternatively, the determination may be made based on the refrigerant flow rate, or the refrigerant flow rate flowing through the circulation path 7 may be detected.

In the above embodiment, both the first and second examples determine whether or not the engine rotational speed Ne is less than the predetermined rotational speed N1, but in the case where the engine 2 stops. The stop of the engine 2 may be determined by obtaining stop information (such as an idle stop signal) of the engine 2 from the vehicle side.
Here, the engine rotational speed Ne is detected by the engine rotational speed sensor 48, but the rotational speed information of the vehicle ECU may be received by CAN communication or the like.

  Further, in the above embodiment, the rotational speed Nb on the expander 20 side and the rotational speed of the pulley 21a on the engine 2 side are compared at the time of initial startup of the Rankine system in the first example. In both the second embodiment, the electromagnetic clutch 32 may be controlled by comparing the rotational speed Nb with the rotational speed of the pulley 21a even when the Rankine system is restarted or during operation of the Rankine system. In this case, during operation of the Rankine system, the rotational speed Nb may be an estimated value based on the above function (1). For example, the pressure difference between the high pressure side and the low pressure side of the Rankine system and the electromagnetic clutch 32 A correlation equation with the rotation speed when the is in the cut state may be obtained by experiments or the like, and the rotation speed Nb may be calculated using this correlation expression.

  In the above embodiment, in both the first and second examples, when the Rankine system is started, when the Rankine system is restarted, after the electromagnetic clutch 32 is connected, the expander inlet valve 18 is opened. However, the expander inlet valve 18 may be opened at the same time as the electromagnetic clutch 32 is connected. As a result, the Rankine system can be started efficiently and smoothly to assist the engine 2 even better.

In the above embodiment, the engine 2 and the expander 20 are connected by the belt 30 in both the first example and the second example. Instead, the engine 2 and the expander 20 are geared together. The transmission path may be configured so as to be connected in pairs.
In the above embodiment, the refrigerant pump 28 is an electric pump in the first example. However, the refrigerant pump may be operated by the belt 30 or the gear set. In this case, the refrigerant pump The pump may be connected to the belt 30 or the gear set via an electromagnetic clutch, and the operation of the electromagnetic clutch may be controlled by the ECU 40 so that the refrigerant pump is activated and deactivated.

2 Engine 3 Crankshaft 3a Pulley 4 Cooling water circuit 6 Rankine cycle circuit 7 Circulation path 10 Evaporator 18 Expander inlet valve 20 Expander 21 Drive shaft 21a Pulley 28 Refrigerant pump 29 Check valve 30 Belt (transmission path)
32 Electromagnetic clutch (power transmission means)
40 ECU (control means)
42, 44 Pressure sensor 46 Expander rotational speed sensor (Expander rotational speed detection means)
48 Engine rotation speed sensor (Engine rotation speed detection means)

Claims (4)

An evaporator that heats and evaporates the working fluid by waste heat of the internal combustion engine in the working fluid circulation path, an expander that expands the working fluid via the evaporator and transmits a rotational driving force to the internal combustion engine, and the expansion Waste heat utilization of an internal combustion engine having a Rankine system comprising a Rankine cycle circuit in which a condenser for condensing the working fluid passing through the machine and a pump for sequentially sending the working fluid passed through the condenser to the evaporator are provided In the device
A power transmission means interposed between the internal combustion engine and the expander, for connecting and disconnecting the transmission path of the rotational driving force between the internal combustion engine and the expander;
Engine rotational speed detecting means for detecting the rotational speed of the internal combustion engine;
A waste heat utilization apparatus for an internal combustion engine, comprising: control means for controlling the power transmission means in a connected state and a disconnected state in accordance with the rotational speed of the internal combustion engine detected by the engine rotational speed detection means.   2. The internal combustion engine according to claim 1, wherein the control means controls the power transmission means to be in a disconnected state when the rotational speed of the internal combustion engine detected by the engine rotational speed detection means is smaller than a predetermined rotational speed. Waste heat utilization equipment of the engine.   The waste heat utilization apparatus for an internal combustion engine according to claim 2, wherein the predetermined rotational speed is a value smaller than an idle rotational speed of the internal combustion engine. Further comprising expander rotation speed detection means for detecting the rotation speed of the expander;
The control means is based on the rotation speed of the expander detected by the expander rotation speed detection means, the rotation speed of the power transmission means based on the rotation speed of the internal combustion engine detected by the engine rotation speed detection means. The waste heat utilization apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the power transmission means is held in a disconnected state when the rotational speed of the power transmission means is greater.

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