JP2016003605A - Vehicle exhaust heat recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the appropriate operating state of a Rankine cycle in a vehicle exhaust heat recovery system including the Rankine cycle and an alternator with a regulator and recovering exhaust heat of a vehicle engine as electric power.SOLUTION: A vehicle exhaust heat recovery system 1 comprises: a Rankine cycle 2 in which a refrigerant pump 22 circulating refrigerant, an evaporator 23 heating and evaporating the refrigerant using exhaust heat of a vehicle engine 10, an expander 24 generating an output by expansion of the refrigerant passing through the evaporator 23, and a condenser 25 condensing the refrigerant passing through the expander 24 are provided in a refrigerant circulation passage 21; an alternator 3 with a regulator driven by the output of the expander 24 to generate electric power and charging an on-vehicle battery 13 with the generated electric power; and a control unit 4 controlling an operating state of the Rankine cycle 2 on the basis of engine state information and battery state information.

Description

  The present invention relates to a vehicle waste heat recovery device mounted on a vehicle, and more particularly to a vehicle waste heat recovery device that recovers waste heat (including exhaust heat) of a vehicle engine as electric power.

  As an example of this type of vehicle waste heat recovery device, a heat transport device described in Patent Document 1 is known. This heat transport device (waste heat recovery device for vehicles) is driven by a Rankine cycle in which an electric liquid pump, a steam generator, an expander, and a radiator are arranged in the refrigerant circuit, and the output of the expander And a generator that generates power and charges the battery, and a control device that controls the operation of the liquid pump. The control device changes the operation state of the liquid pump so as to increase the degree of supercooling when the degree of supercooling of the refrigerant flowing into the liquid pump is lower than a predetermined degree of subcooling. .

JP 2006-329149 A

  By the way, in order to actually apply the vehicle waste heat recovery apparatus as described above to a vehicle and supply the power generated by the generator to the battery (charging the battery), the generator generates power. It is necessary to handle power appropriately. For example, a rectifier or a regulator must be provided between the generator and the battery, and there is a concern that the entire apparatus is complicated and costs and development man-hours increase.

  Therefore, the inventors use an alternator, particularly a vehicle alternator that is widely used in automobiles, as the generator, in order to simplify the entire apparatus in the vehicle waste heat recovery apparatus as described above. Are considering. This is because the alternator is composed of an AC generator and a rectifier, and the vehicle alternator also has a regulator or a function corresponding to this (built in). In this case, the vehicle alternator and the expander operate at the intersection of the rotation speed-torque characteristic line of the vehicle alternator and the output characteristic line of the expander.

  However, the rotation speed-torque characteristic of an alternator with a regulator such as a vehicle alternator varies depending on the state of the battery (for example, battery voltage). Further, the output of the expander during the Rankine cycle operation is not always constant, but varies depending on the operating state of the engine of the vehicle. For this reason, simply operating the Rankine cycle may cause incompatibility between the rotational speed-torque characteristics of the alternator and the output of the expander, and the appropriate operation state of the Rankine cycle may not be maintained.

  Accordingly, an object of the present invention is to maintain an appropriate operating state of a Rankine cycle in a vehicle waste heat recovery apparatus that includes a Rankine cycle and an alternator with a regulator and recovers waste heat of a vehicle engine as electric power. To do.

  According to one aspect of the present invention, a vehicle waste heat recovery device that is mounted on a vehicle and recovers engine waste heat as electric power includes a refrigerant pump that circulates a refrigerant in a refrigerant circulation path, and the refrigerant by the waste heat of the engine. Rankine comprising an evaporator that heats and evaporates, an expander that generates an output by expansion of the refrigerant via the evaporator, and a condenser that condenses the refrigerant via the expander A cycle, a regulator built-in alternator that is driven by the output of the expander to generate electric power, and charges the in-vehicle battery of the vehicle with the generated electric power, engine state information indicating an operating state of the engine, and a state of the in-vehicle battery And a control unit for controlling the operation state of the Rankine cycle based on the battery state information.

  In the vehicle waste heat recovery apparatus, the control unit controls the operation state of the Rankine cycle based on engine state information indicating the operation state of the engine and battery state information indicating the state of the in-vehicle battery. For this reason, during the operation of the Rankine cycle, it is possible to suppress the occurrence of incompatibility between the rotation speed-torque characteristics of the alternator with a regulator and the output of the expander, and the appropriate operation state of the Rankine cycle can be maintained. .

It is a figure showing a schematic structure of a waste heat recovery device for vehicles by one embodiment of the present invention. It is a figure which shows an example of the rotation speed-torque characteristic of the alternator with a regulator which comprises the said waste heat recovery apparatus for vehicles. It is a figure which shows an example of the output characteristic of the expander of Rankine cycle which comprises the said waste heat recovery apparatus for vehicles. It is the figure which displayed the rotation speed-torque characteristic (FIG.2 (b)) of the said alternator, and the output characteristic (FIG.3) of the expander overlaid. It is a flowchart which shows the calculation process of the waste heat amount Qw of the engine which the control unit of the said waste heat recovery apparatus for vehicles performs. It is a flowchart which shows the starting determination process of Rankine cycle which the said control unit performs. It is a flowchart which shows starting control of Rankine cycle which the said control unit performs. It is a flowchart which shows control of the driving | running state of Rankine cycle which the said control unit performs.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a schematic configuration of a vehicle waste heat recovery apparatus 1 according to an embodiment of the present invention. The vehicle waste heat recovery apparatus 1 is mounted on a vehicle and recovers waste heat of the engine 10 of the vehicle as electric power. As shown in FIG. 1, the vehicle waste heat recovery apparatus 1 includes a Rankine cycle 2, an alternator (generator) 3, and a control unit 4.

  The engine 10 is a water-cooled engine, and is cooled by engine cooling water that circulates through the cooling water passage 11 by a cooling water pump (not shown). In the present embodiment, the cooling water pump is a mechanical pump driven by the engine 10. Further, the evaporator 23 of the Rankine cycle 2 to be described later is disposed in the cooling water flow path 11, and the engine cooling water that has absorbed heat from the engine 10 flows through the evaporator 23.

  Rankine cycle 2 collects waste heat of engine 10 and converts it into power. The Rankine cycle 2 has a refrigerant circulation path 21 through which a refrigerant circulates. A refrigerant pump 22, an evaporator (heater) 23, an expander 24, and a condenser 25 are arranged in this order in the refrigerant circulation path 21. It is installed. The Rankine cycle 2 includes a bypass passage 26 that bypasses the expander 24 and distributes the refrigerant, a bypass valve 27 that opens and closes the bypass passage 26, and a blower fan 28 that blows air to the condenser 25. .

  The refrigerant pump 22 is an electric pump and is operated by, for example, electric power from the vehicle-mounted battery 13 of the vehicle to circulate the refrigerant in the refrigerant circuit 21. The evaporator 23 is a heat exchanger that heats the refrigerant to form superheated vapor refrigerant by exchanging heat between the engine coolant that has absorbed heat from the engine 10 and the refrigerant. Although not shown, the evaporator 23 may be configured to exchange heat between the exhaust of the engine 10 and the refrigerant instead of the engine cooling water.

  The expander 24 is, for example, a scroll expander, and is a fluid machine that generates an output by expansion of the refrigerant (that is, superheated vapor refrigerant) via the evaporator 23. The condenser 25 is a heat exchanger that cools and condenses (liquefies) the refrigerant by causing heat exchange between the refrigerant via the expander 24 and the outside air.

  The alternator 3 is connected to the output shaft of the expander 24 and is driven by the output of the expander 24 to generate power. The alternator 3 is, for example, a three-phase alternating current generator including a rectifier, and converts the electric power generated as an alternating current into a direct current and supplies it to the in-vehicle battery 13 to charge the in-vehicle battery 13. The alternator 3 has a built-in regulator and is controlled so that the output voltage is substantially constant regardless of the rotational speed. In the present embodiment, a vehicular alternator that is widely used in automobiles or the like is used as the alternator 3. However, the present invention is not limited to this, and any one having the same function (that is, an alternator with a regulator) may be used.

  The in-vehicle battery 13 is electrically connected to an engine-side alternator 15 that is driven by the engine 10 and generates electric power, in addition to the alternator 3 (Rankine-side alternator) that is driven by the expander 24 to generate electric power. That is, the in-vehicle battery 13 is supplied with the power generated by the alternator (Rankine side alternator) 3 and the power generated by the engine side alternator 15. The in-vehicle battery 13 is also connected to various electric loads 17 mounted on the vehicle. Various electric loads 17 are configured to be operated by the power generated by the alternators 3 and 15 or the power supplied from the in-vehicle battery 13. In the present embodiment, the alternator 3 (Rankine side alternator) and the engine side alternator 15 basically have the same configuration and function.

  The control unit 4 receives detection signals from various sensors, and the control unit 4 controls the operation state of the Rankine cycle 2 based on the input detection signals from the various sensors. Here, the various sensors include a first pressure sensor 51 that detects the high-pressure side pressure PH of the Rankine cycle 2, a second pressure sensor 52 that detects the low-pressure side pressure PL of the Rankine cycle 2, and the rotational speed of the engine 10 (engine The engine speed sensor 53 for detecting the rotational speed (NE), the water temperature sensor 54 for detecting the temperature (cooling water temperature) Tw of the engine cooling water flowing into the evaporator 23, and the voltage (battery voltage) Vb of the in-vehicle battery 13 are detected. A voltage sensor 55, an outside air temperature sensor 56 for detecting the outside air temperature Ta, and the like are included.

  Incidentally, as described above, the rotational speed-torque characteristic of the alternator 3 (alternator with a regulator) varies depending on the state of the in-vehicle battery 13 (for example, the battery voltage Vb). Further, the output of the expander 24 during the operation of the Rankine cycle 2 is not always constant, but varies depending on the operating state of the engine 1 and the like. For this reason, simply operating the Rankine cycle 2 may cause incompatibility between the rotational speed-torque characteristics of the alternator 3 and the output of the expander 24, and the appropriate operation state of the Rankine cycle 2 may not be maintained. . This point will be described with reference to FIGS.

  FIG. 2 is a diagram illustrating an example of the rotational speed-torque characteristic of the alternator 3. FIG. 2A shows the rotation speed-torque characteristic when the battery voltage Vb is low, and FIG. 2B shows the rotation speed-torque characteristic when the battery voltage Vb is medium. ) Shows the rotational speed-torque characteristics when the battery voltage Vb is high.

  As shown in FIG. 2, the torque required to drive the alternator 3 (hereinafter referred to as “load torque of the alternator 3”) increases from the lowest number of revolutions capable of generating power to a predetermined number of revolutions as the number of revolutions increases. When the rotation speed exceeds the predetermined rotation speed, it decreases as the rotation speed increases. That is, the load torque of the alternator 3 is indicated by a straight line rising to the predetermined rotational speed with respect to the rotational speed, and is indicated by a downward-sloping curve after the predetermined rotational speed. Further, the predetermined rotational speed and the load torque of the alternator 3 at the predetermined rotational speed vary according to the battery voltage Vb. Specifically, the load torque of the alternator 3 at the predetermined rotation speed and the predetermined rotation speed decreases as the battery voltage Vb increases. In the following description, the predetermined rotational speed is referred to as “the maximum load rotational speed of the alternator 3”, and the load torque of the alternator 3 at the predetermined rotational speed, that is, the maximum value of the load torque of the alternator 3 is expressed as “alternator 3. The maximum load torque.

FIG. 3 is a diagram illustrating an example of output characteristics of the expander 24.
Even when Rankine cycle 2 is operated under constant conditions (for example, the rotational speed of refrigerant pump 22 is constant), the output of expander 24 varies depending on the operating state of engine 10 and the like. For example, as shown in FIG. 3, when the amount of waste heat Qw of the engine 10 changes and changes to the heat recovery amount Qr of the Rankine cycle 2, the output of the expander 24 also changes accordingly. Specifically, the output of the expander 24 increases as the heat recovery amount Qr of the Rankine cycle 2 increases. Further, since the output of the expander 24 has a so-called constant output characteristic, the torque (drive torque) generated by the expander 24 decreases as the rotational speed increases (inversely proportional to the rotational speed).

FIG. 4 is a diagram in which the rotational speed-torque characteristics (FIG. 2B) of the alternator 3 and the output characteristics of the expander 24 (FIG. 3) are displayed in a superimposed manner when the battery voltage Vb is medium.
The alternator 3 is driven by the expander 24. For this reason, the alternator 3 and the expander 24 operate at the intersection of the rotation speed-torque characteristic line of the alternator 3 and the output characteristic line of the expander 24. Therefore, for example, when the output of the expander 24 changes from “WA” to “WB (<WA)” during the operation of the Rankine cycle 2, the operating points of the alternator 3 and the expander 24 are the points A in FIG. To point B. In this case, the rotation speed of the expander 24 is greatly changed (decreased) from “NexA” to “NexB”. When the rotational speed of the expander 24 changes greatly, the pressure difference before and after the expander 24 (high and low pressure difference in the Rankine cycle 2) changes abruptly, which hinders the operation of the Rankine cycle 2. That is, the appropriate (stable) operating state of Rankine cycle 2 cannot be maintained.

  On the other hand, when the output of the expander 24 changes from “WB” to “WC (<WB)”, the operating point of the alternator 3 and the expander 24 moves from point B to point C in FIG. In this case, the rotation speed of the expander 24 changes (decreases) from “NexB” to “NexC”, but the change (decrease) width is when the output of the expander 24 changes from “WA” to “WB”. Smaller than For this reason, there is almost no possibility that the operation of Rankine cycle 2 will be hindered. That is, an appropriate operation state of the Rankine cycle 2 can be maintained.

  The above is the same when the output of the expander 24 is increased. Further, not only when the battery voltage Vb is medium (FIG. 2B), but also when the battery voltage Vb is high (FIG. 2A) or when the battery voltage Vb is low (FIG. 2C). It is the same.

  Therefore, in the present embodiment, the control unit 4 controls the operating state of the Rankine cycle 2 so that the influence is small even when the output of the expander 24 changes. Specifically, the control unit 4 operates the Rankine cycle 2 within a range in which the output of the expander 24 does not exceed the output upper limit value set according to the battery voltage Vb indicating the state of the in-vehicle battery 13. In other words, the control unit 4 operates the Rankine cycle 2 in a state where the output characteristic line of the expander 24 intersects the straight line portion of the alternator 3 in each state of the in-vehicle battery 13 that rises to the right. Thereby, during the operation of the Rankine cycle 2, the expander 24 operates at a rotational speed lower than the maximum load rotational speed of the alternator 3 in each state of the in-vehicle battery 13.

Hereinafter, various processes executed by the control unit 4 will be described.
FIG. 5 is a flowchart showing a calculation process of the amount of waste heat Qw of the engine 10. This flowchart is started when the engine 10 is started, and is repeatedly executed at a predetermined cycle while the engine 10 is operating.

In step S1, the engine speed NE (engine speed) NE is read.
In step S2, the flow rate (cooling water flow rate) q of the engine cooling water is calculated based on the read engine speed Ne. For example, the control unit 4 calculates the cooling water flow rate q with reference to a cooling water flow rate map (not shown) in which the engine speed Ne and the cooling water flow rate q are associated with each other.

In step S3, the engine cooling water temperature (cooling water temperature) Tw is read.
In step S4, the amount of waste heat Qw of the engine 10 is calculated based on the calculated cooling water flow rate q and the read cooling water temperature Tw. For example, the control unit 4 calculates the waste heat amount Qw of the engine 10 with reference to a waste heat amount map (not shown) in which the coolant temperature Tw and the coolant flow rate q are associated with the waste heat amount Qw of the engine 10. .

FIG. 6 is a flowchart showing start-up determination processing in Rankine cycle 2. This flowchart is repeatedly executed at a predetermined cycle while the Rankine cycle 2 is stopped.
In step S11, the amount of waste heat Qw of the engine 10 is read.
In step S12, it is determined whether or not the read waste heat amount Qw of the engine 10 is equal to or greater than the waste heat amount threshold Qth. If the amount of waste heat Qw of the engine 10 is greater than or equal to the waste heat amount threshold value Qth, the process proceeds to step S13. On the other hand, if the waste heat amount Qw of the engine 10 is less than the waste heat amount threshold value Qth, this flow is terminated. In this case, Rankine cycle 2 is not activated. This is because when the waste heat amount Qw of the engine 10 is less than the waste heat amount threshold value Qth, even if the Rankine cycle 2 is operated, a sufficient output of the expander 24 cannot be obtained and the engine 10 may become a load on the contrary.

In step S13, the battery voltage Vb is read.
In step S14, the maximum load torque and the maximum load rotation speed of the alternator 3 are obtained based on the read battery voltage Vb. For example, the control unit 4 obtains the maximum load torque and the maximum load rotational speed of the alternator 3 with reference to an alternator characteristic map in which the battery voltage Vb is associated with the maximum load torque and the maximum load rotational speed of the alternator 3.

In step S15, the output upper limit value of the expander 24 is calculated (set) based on the maximum load torque and the maximum load rotation speed of the alternator 3. The output upper limit value of the expander 24 is calculated (set) to a smaller value as the battery voltage Vb is higher.
In step S16, the calculated (set) output upper limit value of the expander 24 is compared with the previously stored minimum output value of the expander 24 during the Rankine cycle 2 operation. If the output upper limit value of the expander 24 is equal to or greater than the output minimum value of the expander 24, the process proceeds to step S17 and the start of the Rankine cycle 2 is permitted. On the other hand, if the output upper limit value of the expander 24 is smaller than the output minimum value of the expander 24, this flow ends. In this case, Rankine cycle 2 is not activated. This is because an appropriate operating state of the Rankine cycle 2 may not be maintained due to output fluctuation of the expander 24 or the like.

  FIG. 7 is a flowchart showing the start-up control of Rankine cycle 2. This flowchart is started when the Rankine cycle 2 is permitted to start in step S17 of FIG.

In step S21, the bypass valve 27 is opened.
In step S22, the refrigerant pump 22 and the blower fan 28 are operated. For example, the control unit 4 operates the refrigerant pump 22 at a predetermined rotation speed (for example, rotation speed at startup) set in advance, and operates the blower fan 28 at a rotation speed set according to the outside air temperature Ta. it can.

In step S23, the high pressure side pressure PH and low pressure side pressure PL of Rankine cycle 2 are read.
In step S24, the high / low pressure difference ΔP (= PH−PL) of Rankine cycle 2 is calculated based on the read high pressure side pressure PH and low pressure side pressure PL.

  In step S25, the calculated high / low pressure difference ΔP is compared with the pressure threshold value Pth for starting determination. If the high / low pressure difference ΔP ≧ the pressure threshold Pth, the process proceeds to step S26, and if the high / low pressure difference ΔP <the pressure threshold Pth, the process proceeds to step S27.

In step S26, the bypass valve 27 is closed. As a result, the expander 24 can generate an output, and the start-up of the Rankine cycle 2 is completed.
In step S27, it is determined whether or not a predetermined time has elapsed since the refrigerant pump 22 was operated. If the predetermined time has not elapsed, the process returns to step S23. If the predetermined time has elapsed, the process proceeds to step S28, and the refrigerant pump 22 and the blower fan 28 are stopped. In this case, Rankine cycle 2 is not started (operated). This is because there is a possibility that an abnormality (failure) has occurred in the Rankine cycle 2.

  FIG. 8 is a flowchart showing the control of the operating state of Rankine cycle 2. This flowchart is repeatedly executed at a predetermined cycle during the operation of the Rankine cycle 2.

  In step S31, it is determined whether the engine 10 has stopped. If engine 10 has stopped, it will progress to Step S32 and will stop operation of Rankine cycle 2 (stops refrigerant pump 22). On the other hand, if the engine 10 is not stopped, the process proceeds to step S33.

In step S33, the battery voltage Vb is read.
In step S34, as in step S14 of FIG. 6, the maximum load torque and the maximum load rotational speed of the alternator 3 are obtained based on the read battery voltage Vb.
In step S35, the output upper limit value of the expander 24 is calculated (set) based on the maximum load torque and the maximum load rotational speed of the alternator 3 as in step S15 of FIG.

In step S36, the amount of waste heat Qw of the engine 10 is read.
In step S37, the current output of the expander 24 is calculated based on the read waste heat amount Qw of the engine 10 and the current rotational speed (pump rotational speed) Np of the refrigerant pump 22. The output of the expander 24 depends on the heat recovery amount Qr of the Rankine cycle 2, and the heat recovery amount Qr of the Rankine cycle 2 depends on the waste heat amount Qw of the engine 10 and the pump rotational speed Np. Therefore, the control unit 4 refers to the expander output map (not shown) in which the waste heat amount Qw of the engine 10, the rotation speed of the refrigerant pump 22, and the output of the expander 24 are associated with each other, for example. Calculate the current output.

  In step S38, the output upper limit value of the expander 24 calculated (set) in step S35 is compared with the current output of the expander 24 calculated in step S37. If the current output of the expander 24> the output upper limit value of the expander 24, the process proceeds to step S32, and the operation of the Rankine cycle 2 is stopped. On the other hand, if the current output of the expander 24 ≦ the output upper limit value of the expander 24, the process proceeds to step S39.

  In step S39, a target output (<output upper limit value) of the expander 24 is set. The control unit 4 sets the target output of the expander 24 in consideration of the fluctuation amount of the battery voltage Vb. For example, the control unit 24 determines the maximum load torque and the maximum load rotation of the alternator 3 based on the value (Vb−ΔVb) obtained by subtracting the fluctuation range ΔVb of the battery voltage Vb when the vehicle travels from the battery voltage Vb read in step S33. The target output of the expander 24 is calculated based on the calculated maximum load torque and maximum load rotation speed of the alternator 3. Here, the fluctuation range ΔVb of the battery voltage Vb when the vehicle travels includes a fluctuation amount of the battery voltage Vb that may be caused by the use of auxiliary equipment such as an air conditioner in the vehicle, and is measured in advance for each vehicle. . However, the present invention is not limited to this, and the control unit 4 more easily sets a value of about 80 to 90% of the output upper limit value of the expander 24 calculated (set) in step S35 as the target output. Can do.

  In step S40, the current output of the expander 24 is brought close to the target output. For example, the control unit 4 controls (increases / decreases) the rotational speed (pump rotational speed Np) of the refrigerant pump 22 in accordance with the difference between the target output and the current output of the expander 24, thereby causing the current of the expander 24 to be increased. Is brought close to the target output. This is because if the pump speed Np is changed, the heat recovery amount Qr of Rankine cycle 2 and, in turn, the output of the expander 24 change.

  In the present embodiment, the amount of waste heat Qw, the engine speed Ne, the cooling water temperature Tw, etc. of the engine 10 correspond to “engine state information” of the present invention, and the battery voltage Vb corresponds to “battery state information” of the present invention. .

  According to the present embodiment, the control unit 4 controls the operation state of the Rankine cycle 2 based on the engine state information indicating the operation state of the engine 10 and the battery state information indicating the state of the in-vehicle battery 13. Specifically, the control unit 4 operates the Rankine cycle 2 within a range where the output of the expander 24 does not exceed the output upper limit value set according to the battery voltage Vb. For this reason, even if the output of the expander 24 fluctuates during the operation of the Rankine cycle 2 due to the operating state of the engine 10, the output of the expander 24 is reliably driven by the output of the expander 24. Rapid fluctuations in the rotational speed can be suppressed. Thereby, the suitable driving | running state of Rankine cycle 2 is maintained.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Of course, a further deformation | transformation and change are possible based on the technical idea of this invention. . Some examples are given below.

  In the above-described embodiment, the control unit 4 sets a target output of the expander 24 that is smaller than the output upper limit value, and the rotation speed (pump of the refrigerant pump 22) so that the output of the expander 24 approaches the target output. Rotational speed) Np is controlled. More specifically, the control unit 4 controls (increases / decreases) the pump rotational speed Np according to the difference (output difference) between the target output and the current output of the expander 24 in step S40 of FIG. Thus, the output of the expander 24 is brought close to the target output. However, it is not limited to this. The control unit 4 may control the rotational speed (fan rotational speed) Nf of the blower fan 28 instead of or in addition to controlling the pump rotational speed Np. This is because changing the fan speed Nf changes the condensing capacity of the condenser 25 and also changes the output of the expander 24. In this case, the control unit 4 can increase or decrease the fan rotation speed Nf according to the difference (output difference) between the target output and the current output of the expander 24, similarly to the pump rotation speed Np.

  Further, the control unit 4 may control the opening degree of the bypass valve 27 instead of or in addition to controlling (increasing or decreasing) the pump rotational speed Np in step S40 of FIG. This is because by opening the bypass valve 27, the amount of the refrigerant corresponding to the opening degree does not pass through the expander 24, and the output of the expander 24 decreases. In this case, the control unit 4 can control the opening degree of the bypass valve 27 according to the difference (output difference) between the target output and the current output of the expander 24.

  Of course, the control unit 4 performs the control of the pump speed Np, the control of the fan speed Nf, and the control of the opening degree of the bypass valve 27 in an appropriate combination so as to bring the output of the expander 24 closer to the target output. It may be.

  Further, in the above-described embodiment, the control unit 4 stops the operation of the Rankine cycle 2 when the current output of the expander 24> the output upper limit value of the expander 24 in step S38 of FIG. (Step S32). However, for example, when the current output of the expander 24-the output upper limit value of the expander 24 is equal to or less than a predetermined value, the output reduction process of the expander 24 may be performed. In this case, the control unit 4 reduces the current output of the expander 24 by, for example, decreasing the pump rotational speed Np, decreasing the fan rotational speed Nf, and / or increasing the opening of the bypass valve 27. The output upper limit value is set.

  Furthermore, in the above-described embodiment, the battery voltage Vb is used as information indicating the state of the in-vehicle battery 13, but instead of this, an SOC (State of Charge) value indicating the state of charge of the in-vehicle battery 13 is used. Also good.

  DESCRIPTION OF SYMBOLS 1 ... Waste heat recovery apparatus for vehicles, 2 ... Rankine cycle, 3 ... Alternator, 4 ... Control unit, 10 ... Engine, 11 ... Cooling water flow path, 13 ... In-vehicle battery, 15 ... Engine side alternator, 17 ... Electric load, 21 Refrigerant circuit, 22 ... Refrigerant pump, 23 ... Evaporator, 24 ... Expander, 25 ... Condenser, 26 ... Bypass passage, 27 ... Bypass valve, 28 ... Blower fan, 51 ... First pressure sensor, 52 ... First 2 pressure sensor, 53 ... engine rotation sensor, 54 ... water temperature sensor, 55 ... voltage sensor, 56 ... outside air temperature sensor

Claims (8)

A vehicle waste heat recovery device mounted on a vehicle and recovering engine waste heat as electric power,
A refrigerant pump that circulates the refrigerant in the refrigerant circulation path, an evaporator that heats and evaporates the refrigerant by waste heat of the engine, an expander that generates an output by expansion of the refrigerant via the evaporator, and the expansion A Rankine cycle configured to be provided with a condenser for condensing the refrigerant via a machine;
An alternator with a regulator that is driven by the output of the expander to generate power, and that charges the in-vehicle battery of the vehicle with the generated power;
A control unit for controlling the operating state of the Rankine cycle based on engine state information indicating the operating state of the engine and battery state information indicating the state of the in-vehicle battery;
Waste heat recovery device for vehicles including   The control unit operates the Rankine cycle so that the expander operates at a rotational speed lower than a maximum load rotational speed at which a load torque for driving the alternator is maximized in each state of the in-vehicle battery. The vehicle waste heat recovery apparatus according to claim 1, wherein the state is controlled.   3. The vehicle waste heat recovery according to claim 1, wherein the control unit operates the Rankine cycle within a range in which an output of the expander does not exceed an output upper limit value set according to the battery state information. apparatus.   The waste heat recovery apparatus for a vehicle according to claim 3, wherein the output upper limit value is set to a smaller value as a battery voltage of the in-vehicle battery is higher.   The waste heat recovery apparatus for a vehicle according to claim 3 or 4, wherein the output upper limit value is set based on a rotation speed-torque characteristic of the alternator that changes according to a state of the in-vehicle battery.   The said control unit sets the target output of the said expander smaller than the said output upper limit, and controls the rotation speed of the said refrigerant | coolant pump so that the output of the said expander may approach the said target output. The waste heat recovery apparatus for vehicles as described in any one of these. The Rankine cycle includes a blower fan that blows air to the condenser,
The said control unit sets the target output of the said expander smaller than the said output upper limit, and controls the rotation speed of the said ventilation fan so that the output of the said expander may approach the said target output. The waste heat recovery apparatus for vehicles as described in any one of these. The Rankine cycle is
A bypass flow path for circulating the refrigerant around the expander;
A bypass valve for opening and closing the bypass flow path;
With
The said control unit sets the target output of the said expander smaller than the said output upper limit, and controls the opening degree of the said bypass valve so that the output of the said expander may approach the said target output. The waste heat recovery apparatus for vehicles as described in any one of these.