JP2007123169A - Fuel cell vehicle and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure deceleration feeling in regenerative braking in a fuel cell vehicle and at the same time suppress dry up of a fuel cell. <P>SOLUTION: In a fuel cell system which is mounted on a movable body such as the fuel cell vehicle and operated, when braking is required in such a state that the residual capacity of a power storage device 15 constituting the fuel cell system is higher than the prescribed threshold value, a cathode compressor 5 is operated for only the prescribed time. For example, it is conducted when a shift device in the fuel cell vehicle is shifted from a no-regenerative braking position (a D range) to a regenerative braking position (a B range). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a control method thereof. More specifically, the present invention relates to an improvement in control technology when surplus regenerative power is consumed in a mobile body such as a fuel cell vehicle.

A mobile body (for example, a fuel cell vehicle) equipped with a fuel cell system generates torque equivalent to an engine brake by regenerating a drive motor while traveling on a long descent slope, for example, and the regenerative energy generated at this time is generated. In general, it is stored in a secondary battery. However, surplus regenerative power must be consumed somewhere in order to secure braking torque (brake torque) even if the storage capacity of the secondary battery is exceeded. The technology of consuming with a large air compressor) is used. In other words, power can be stored (charged) while the secondary battery recovery allowable power is greater than the regenerative power, but when the secondary battery is fully charged, no more power can be stored, so braking torque In order to ensure this, excessive regenerative power is consumed by an air compressor or the like (see, for example, Patent Document 1).
JP 2002-203583 A

  However, when the air compressor is operated as an auxiliary device to consume power, the air flow rate to the fuel cell increases with the operation of the air compressor, so that the electrolyte membrane of the fuel cell is likely to dry. There's a problem. This problem is more conspicuous when the air is hot or dry, and when drying proceeds in this way, the electrolyte membrane deteriorates in a so-called dry-up state, and eventually the voltage drops. It may lead to a phenomenon.

  Accordingly, an object of the present invention is to provide a fuel cell system and a control method therefor that can prevent the fuel cell from entering a dry-up state while ensuring a sense of deceleration during regenerative braking in a moving body. .

  In order to solve this problem, the present inventor has made various studies. In a mobile body (for example, a fuel cell vehicle) equipped with a fuel cell system, a braking request may be issued at one of the timings when a braking torque by regenerative braking is desired. Therefore, if a control method of consuming excess regenerative power by limiting the opportunity or time when a braking request is issued in this way can be established, the feeling of deceleration during regenerative operation is not impaired. We have obtained new knowledge that it is possible to control the dry-up phenomenon.

  The present invention is based on such knowledge, and the invention according to claim 1 is a fuel cell system including a power storage device, wherein the remaining capacity of the power storage device is high and the internal state of the fuel cell is determined. When there is a braking request, the cathode compressor is operated only for a predetermined time.

  According to the present invention, when the remaining capacity of the power storage device in the fuel cell system is high (for example, the power storage device is fully charged or close to this, and the surplus regenerative power generated during braking is sufficiently stored (absorbed). ), And when there is a braking request according to the internal state of the fuel cell, the surplus regenerative power is consumed and the braking torque is secured by operating the cathode compressor. Can do. In this case, since the cathode compressor is operated only for a predetermined time, it is possible to suppress drying of the fuel cell while ensuring braking torque. Examples of the state inside the fuel cell include the temperature of the fuel cell based on the operating state before braking or the ease of evaporation inside the fuel cell related to the temperature, in addition to the water retention state of the electrolyte membrane. According to the present invention, when there is a braking request according to such an internal state, the fuel cell is in a dry-up state while securing braking torque and ensuring a feeling of deceleration during the regenerative operation. Can be suppressed.

  According to a second aspect of the present invention, in the fuel cell system according to the first aspect, when the remaining capacity of the power storage device is high and the fuel cell stack is in a dry-up state and a braking request is made, the cathode The compressor is operated only for a predetermined time.

  According to the present invention, when the remaining capacity of the power storage device in the fuel cell system is high (for example, the power storage device is fully charged or close to this, and the surplus regenerative power generated during braking is sufficiently stored (absorbed). ), It is possible to ensure the braking torque by consuming surplus regenerative power by operating the cathode compressor. In addition, in this case, since the cathode compressor is operated only for a predetermined time, it is possible to suppress the drying of the fuel cell while securing the braking torque.

  According to a third aspect of the present invention, in the fuel cell system according to the first or second aspect, when there is a regeneration request, the cathode compressor is operated only for a predetermined time.

  In this case, surplus regenerative power is consumed according to the regeneration request, so that braking torque can be generated according to the request. In addition, by limiting the operation of the cathode compressor to a predetermined time, it is possible to prevent the fuel cell from drying while securing the braking torque.

  Furthermore, the invention according to claim 4 is the fuel cell system according to any one of claims 1 to 3, wherein the cathode is changed when the shift is changed from a position where regenerative braking is not performed to a position where regenerative braking is performed. The compressor is operated only for a predetermined time.

  For example, when such a shift change is performed in a fuel cell vehicle or the like, it is determined that there is a braking request, and a braking torque is generated by operating the cathode compressor in accordance with this request. In this case, since the operation of the cathode compressor is limited to a predetermined time, it is possible to prevent the fuel cell from drying while securing the braking torque.

  According to a fifth aspect of the present invention, there is provided a fuel cell that generates electric power by receiving gas supply, a cathode compressor that supplies cathode gas to a fuel cell stack of the fuel cell, and a control device that controls the operation of the cathode compressor. And a power storage device that stores the electric power generated by the fuel cell, and is mounted on a mobile body and operates, wherein the control device has a remaining capacity of the power storage device that exceeds a predetermined threshold value. The cathode compressor is operated only for a predetermined time when there is a braking request from the moving body in a high state.

  According to the present invention, when the remaining capacity of the power storage device is higher than the predetermined threshold, it is determined that the power storage device is fully charged or is in a state close to this, and the cathode compressor is operated. Excess regenerative power is consumed. According to this, a braking torque can be ensured when there is a braking request from the moving body. In addition, in this case, since the cathode compressor is operated only for a predetermined time, it is possible to suppress the drying of the fuel cell while securing the braking torque.

  In the fuel cell system according to claim 5, the control device operates the cathode compressor only for a predetermined time when there is a regeneration request.

  In this case, surplus regenerative power is consumed according to the regeneration request, so that braking torque can be generated according to the request. In addition, by limiting the operation of the cathode compressor to a predetermined time, it is possible to prevent the fuel cell from drying while securing the braking torque.

  Further, the invention according to claim 7 is the fuel cell system according to claim 5 or 6, wherein the control device is configured such that the shift device in the moving body performs regenerative braking from a position where regenerative braking is not performed. When the shift is changed to the position, the cathode compressor is operated only for a predetermined time.

  For example, when such a shift change is made in a fuel cell vehicle, the fuel cell system (or its control device) determines that a braking request has been made, and braking is performed by operating the cathode compressor in accordance with this request. Generate torque. In this case, since the operation of the cathode compressor is limited to a predetermined time, it is possible to prevent the fuel cell from drying while securing the braking torque.

  According to an eighth aspect of the present invention, in the control method for a fuel cell system in a mobile body equipped with the fuel cell system, there is a braking request when the remaining capacity of the power storage device constituting the fuel cell system is high. In this case, the cathode compressor is operated only for a predetermined time.

  According to the present invention, when the remaining capacity of the power storage device in the fuel cell system is high, surplus regenerative power can be consumed by operating the cathode compressor, and braking torque can be ensured. In addition, in this case, since the cathode compressor is operated only for a predetermined time, it is possible to suppress the drying of the fuel cell while securing the braking torque.

  According to a ninth aspect of the present invention, in the control method for the fuel cell system according to the eighth aspect, when there is a regeneration request for the moving body, the cathode compressor is operated only for a predetermined time.

  In this case, surplus regenerative power is consumed according to the regeneration request, so that braking torque can be generated according to the request. In addition, by limiting the operation of the cathode compressor to a predetermined time, it is possible to prevent the fuel cell from drying while securing the braking torque.

  Furthermore, the invention according to claim 10 is the control method for the fuel cell system according to claim 8 or 9, wherein the shift device in the moving body is moved from a position where regenerative braking is not performed to a position where regenerative braking is performed. When the shift is changed, the cathode compressor is operated only for a predetermined time.

  For example, when such a shift change is performed in a fuel cell vehicle or the like, it is determined that there is a braking request, and a braking torque is generated by operating the cathode compressor in accordance with this request. In this case, since the operation of the cathode compressor is limited to a predetermined time, it is possible to prevent the fuel cell from drying while securing the braking torque.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that a fuel cell will be in a dry-up state, ensuring the feeling of deceleration at the time of the regenerative braking in a moving body. Therefore, when surplus regenerative power is consumed, it is possible to suppress the phenomenon that the electrolyte of the fuel cell deteriorates and the voltage drops.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  1 to 3 show an embodiment of a fuel cell system according to the present invention. The fuel cell system 1 according to the present embodiment is a system that can be mounted on a mobile body such as a fuel cell vehicle, and has a remaining capacity (hereinafter referred to as SOC (State of Charge)) of a power storage device (hereinafter referred to as a secondary battery) 15. Judgment is made as to how much the battery is charged. Here, when there is a braking request from a fuel cell vehicle under a high SOC condition, a cathode compressor (hereinafter referred to as an air compressor) 5 such as an air compressor is operated only for a predetermined time. Hereinafter, first, the outline of the fuel cell system 1 will be described, and then the contents of control for the air compressor 5 and the like will be described (see FIGS. 1 to 3).

  FIG. 1 shows a schematic configuration of a fuel cell system 1 according to the present embodiment. The fuel cell system 1 shown in the present embodiment can be used as, for example, an on-vehicle power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle), but is not limited to this, and various mobile objects (for example, ships) Naturally, it can also be used as a power generation system mounted on a self-propelled device such as a robot or a robot. Here, a fuel cell stack (hereinafter also simply referred to as a fuel cell) 2 has a stack structure in which a plurality of single cells are stacked in series, and is composed of, for example, a solid polymer electrolyte fuel cell. .

  The oxidizing gas supply system to the fuel cell 2 includes an air compressor 5, an intercooler 3, and an intercooler cooling water pump 4 (see FIG. 1). The air compressor 5 compresses air taken from outside air through an air filter (not shown). The intercooler 3 cools the air that has been compressed to a high temperature. The intercooler cooling water pump 4 circulates cooling water for cooling the intercooler 3. The air compressed by the air compressor 5 is cooled by the intercooler 3 in this way, passes through the humidifier 17, and is supplied to the cathode (oxygen electrode) of the fuel cell 2. The oxygen off-gas after being subjected to the cell reaction of the fuel cell 2 flows through the cathode off-gas channel 16 and is exhausted out of the system. This oxygen off gas is in a highly moist state because it contains moisture generated by the cell reaction in the fuel cell 2. Therefore, the humidifier 17 exchanges moisture between the oxidant gas before supply in a low wet state and the oxygen off gas in high wet state flowing through the cathode offgas flow path 16, and the oxidant gas supplied to the fuel cell 2 Humidify moderately.

  A cooling water pipe 11 for circulating the cooling water is provided at the inlet / outlet of the cooling water (LLC) of the fuel cell 2. The cooling water pipe 11 is provided with a water pump 10 that sends out the cooling water and a flow path switching valve 12 for adjusting the cooling water supply amount.

  A part of the DC power generated by the fuel cell 2 is stepped down by the DC / DC converter 14 and stored in the secondary battery (battery) 15. The motor inverter 7 converts the DC power supplied from the fuel cell 2 into AC power and supplies the AC power to the traction motor 8. Further, the water pump inverter 9 converts the DC power supplied from the fuel cell 2 into AC power and supplies the AC power to the water pump 10. Further, the air compressor driving inverter 6 converts the DC power supplied from the fuel cell 2 into AC power and supplies the AC power to the air compressor 5.

  For example, if the control device 13 is mounted on a fuel cell vehicle, the control device 13 obtains the system required power (the sum of the vehicle travel power and the auxiliary power) based on the accelerator opening, the vehicle speed, etc. It is a device that controls the system to match the power. More specifically, the control device 13 controls the air compressor driving inverter 6 to adjust the rotational speed and the oxidizing gas supply amount of a motor (not shown) that drives the air compressor 5. Further, the temperature of the compressed air is adjusted by controlling the water pump 4 for cooling the intercooler. Further, the motor inverter 7 is controlled to adjust the rotational speed of the traction motor 8, and the water pump inverter 9 is controlled to adjust the water pump 10. Further, the operation point (output voltage, output current) of the fuel cell 2 is adjusted by controlling the DC / DC converter 14 so that the output power of the fuel cell 2 matches the target power.

  Further, the fuel cell system 1 of the present embodiment is configured such that surplus regenerative power during braking of the fuel cell vehicle can be consumed by the air compressor 5 described above (see FIG. 1). That is, in the fuel cell vehicle having the configuration including the secondary battery 15, for example, the torque equivalent to the engine brake is generated by regenerating the traction motor (drive motor) 8 on a long downhill road. The regenerative energy is stored in the secondary battery 15 described above. However, since the energy needs to be consumed by another method when the storage capacity is exceeded, for example, in the present embodiment, extra regenerative energy is consumed by operating the air compressor 5, and thus stable. Brake torque is obtained.

  Here, in the fuel cell system 1 according to the present embodiment, when the air compressor 5 consumes extra regenerative energy (excess regenerative power), control is performed as follows (see FIG. (See 3 etc.).

  First, when there is a braking request from a mobile body (fuel cell vehicle), it is determined how much the SOC (State of Charge, battery storage state) of the secondary battery 15 is. Here, there are various types of braking requests from the fuel cell vehicle. As an example, the case where the range of the shift device 18 is changed will be described in the present embodiment. The shift device 18 illustrated in FIG. 2 is a gate-type device including a so-called push-pull type shift lever 18a. The shift positions in the shift device 18 are, in order from the upper side (front of the car) to the lower side (back of the car), P position (parking range), R position (reverse range), N position (neutral range), D position (drive). Range) and B position (brake range) (see FIG. 2). In the case of such a shift device 18, when it is desired to generate a brake torque (braking torque) on a long downhill road during traveling at the D position, the shift lever 18 a is shifted to the previous B position to perform braking. The brake torque can be obtained upon request. When such a brake torque is generated, an occupant such as a driver of a fuel cell vehicle can feel a deceleration feeling like an engine brake in a vehicle using an internal combustion engine as a power source.

  As described above, when the braking request is issued by shifting the shift lever 18a to the B position, the fuel cell system 1 according to the present embodiment determines the SOC of the secondary battery 15 as described above. When the SOC of the secondary battery 15 is a specified value (for example, 80%) or less, the regenerative power is stored in the secondary battery 15. That is, the traction motor 8 is rotated by the driving wheel of the fuel cell vehicle, and the regenerative power generated at this time is stored, and the kinetic energy is converted into electrical energy to be stored.

  On the other hand, when the SOC of the secondary battery 15 exceeds the specified value, the secondary battery 15 is fully charged or close to this, and the remaining regenerative power is sufficiently stored. It is determined that the SOC is so high that it cannot be performed. In this case, it is determined whether or not the fuel cell 2 is in a dry-up state. If the fuel cell 2 is in a dry-up state, the air compressor 5 is operated by the electric power so as to effectively consume surplus regenerative power. To do.

  Whether or not the fuel cell 2 is in the dry-up state (or the degree of the state) is referred to, for example, a related map between the monitored AC impedance and the wet state, and the wet state is compared with a predetermined threshold value. It can be judged by. That is, a measurement device (not shown) that can measure the impedance of a single cell or a single cell stack (fuel cell stack) can be used to make a determination from the measurement result. For example, since the overall impedance of the fuel cell 2 shows a high value when the electrolyte membrane is changed from a wet state to a dry state and the proton conductivity is lowered, it is possible to determine the internal state using this fact. is there.

  Here, when the air compressor 5 is operated by surplus regenerative power as described above, the air compressor 5 is operated only for a predetermined time in the present embodiment (see FIG. 3). As described above, according to the control method of the present embodiment that limits the operation time of the air compressor 5, it is possible to prevent the fuel cell 2 from being in a dry-up state while ensuring regenerative braking. The predetermined time in this case can take various values depending on the specification or rating of the fuel cell system 1, the drying state (dry-up state), the atmosphere (environment) at that time, etc. It is preferable to set it to such an extent that it is not impaired (a degree that allows a feeling of deceleration to be sufficiently experienced), for example, about 2 to 3 seconds (see FIG. 3). In such a case, since it is possible to ensure both a feeling of deceleration in the fuel cell vehicle and to suppress drying of the electrolyte membrane, the electrolyte of the fuel cell 2 is deteriorated due to deterioration of the electrolyte of the fuel cell 2 when surplus regenerative power is consumed. It is possible to suppress the occurrence of a phenomenon such as a decrease. Thus, if electrolyte deterioration is suppressed, it becomes possible to prolong the life of the fuel cell 2 (and the fuel cell system 1 including the same).

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, it has been described that the air compressor 5 is operated when the fuel cell 2 is in the dry-up state. However, this is only a preferable example, and the compressor 5 is operated even if it is not in the dry-up state. It is also possible to make it. In short, the present invention aims to avoid drying of the electrolyte membrane of the fuel cell 2 while ensuring a feeling of deceleration that can be experienced (or actually acts) during regenerative braking. However, it is also effective to limit the operating time of the air compressor 5 as a preventive measure. In addition, the dry-up state is not a binary thing such as whether or not it is dry, but can change continuously. Therefore, the air compressor 5 is limited as necessary while sequentially referring to the state. It is good to do. Alternatively, it may be an effective means to appropriately change the operation time of the air compressor 5 within a range that does not lead to dry-up in response to the dry-up state. If other examples are given here, the fuel cell 2 is in a state other than the dry-up state inside the fuel cell, for example, the temperature of the fuel cell 2 based on the operating state before braking, or the fuel cell 2 related to the temperature. It is possible to take into account the easiness of evaporation in the interior of the container.

  Moreover, in this embodiment, the case where the range of the shift device 18 was changed was given as an example of the braking request, but this is just an example. In addition, an operation of stepping on the foot brake can be included in the braking request, or an operation of releasing the accelerator can be included in the braking request. Furthermore, the operation of pulling the handbrake can also be included in the braking request. In short, a braking torque is obtained in response to a request to brake a mobile object such as a fuel cell vehicle (in some cases, a regeneration request to obtain regenerative power using the operation at the time of braking is included). It is possible to apply the present invention during the operation to be performed.

  Furthermore, in the present embodiment, it is shown that the predetermined operation time of the air compressor 5 is about 2 to 3 seconds. However, this is only an example, and as described above, the specifications and ratings of the fuel cell system 1 and the like. It can be changed as appropriate according to various factors. Even when the time is changed to various times as described above, at least during this time, a braking force such as an engine brake in an automobile using an internal combustion engine as a power source acts. You can get a feeling of slowdown.

1 is a diagram showing a schematic configuration of a fuel cell system according to an embodiment of the present invention. It is a figure which shows an example of a shift apparatus. It is a graph which shows an example of the change of the braking torque when the operation time of an air compressor is limited to predetermined time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell (fuel cell stack), 5 ... Air compressor (cathode compressor), 13 ... Control apparatus, 15 ... Secondary battery (electric storage apparatus), 18 ... Shift apparatus

Claims (10)

In a fuel cell system equipped with a power storage device,
A fuel cell system, wherein a cathode compressor is operated only for a predetermined time when a remaining capacity of the power storage device is high and a braking request is made according to an internal state of the fuel cell.   2. The fuel according to claim 1, wherein the cathode compressor is operated only for a predetermined time when the remaining capacity of the power storage device is high and a braking request is made while the fuel cell stack is in a dry-up state. Battery system.   3. The fuel cell system according to claim 1, wherein the cathode compressor is operated only for a predetermined time when there is a regeneration request. 4.   4. The fuel cell system according to claim 1, wherein the cathode compressor is operated only for a predetermined time when a shift is changed from a position where regenerative braking is not performed to a position where regenerative braking is performed. 5. . A fuel cell that generates electricity by receiving gas supply;
A cathode compressor for supplying a cathode gas to the fuel cell stack of the fuel cell;
A control device for controlling the operation of the cathode compressor;
A power storage device for storing electric power generated by the fuel cell;
In a fuel cell system that is mounted on a moving body and operates,
The control device operates the cathode compressor only for a predetermined time when there is a braking request from the moving body under a state where the remaining capacity of the power storage device is higher than a predetermined threshold value. A fuel cell system.   6. The fuel cell system according to claim 5, wherein the control device operates the cathode compressor only for a predetermined time when there is a regeneration request.   The control device operates the cathode compressor only for a predetermined time when a shift device in the moving body is shifted from a position where regenerative braking is not performed to a position where regenerative braking is performed. Item 7. The fuel cell system according to Item 5 or 6. In a control method of the fuel cell system in a mobile body equipped with the fuel cell system,
A control method for a fuel cell system, comprising: operating a cathode compressor only for a predetermined time when a braking request is made in a state where a remaining capacity of a power storage device constituting the fuel cell system is high.   9. The control method for a fuel cell system according to claim 8, wherein the cathode compressor is operated only for a predetermined time when there is a regeneration request for the moving body. The shift device in the moving body operates the cathode compressor only for a predetermined time when the shift is changed from a position where regenerative braking is not performed to a position where regenerative braking is performed. The fuel cell system control method described.

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