JP2006302739A - Temperature estimation device of fuel cell and fuel cell system controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate the temperature of a fuel cell based on the temperature of cooling water delivered from the fuel cell and ambient temperature, and decide whether heating of the fuel cell is necessary or not. <P>SOLUTION: A fuel cell system controller equipped with a cooling means 3 cooling moisture exhausted from the fuel cell 1 in the downstream part of a heating means 11 heating the moisture in a circulation passage 37 through which the moisture is circulated to the fuel cell 1 is equipped with a first temperature detecting means 32 detecting the ambient temperature, a second temperature detecting means 30 detecting the temperature of moisture in an outlet of the fuel cell 1, a third temperature detecting means 33 detecting the temperature of moisture in an inlet of the cooling means 3, and the temperature of the fuel cell is estimated based on the temperature difference between the temperature detected with the second temperature detecting means 30 and the temperature detected with the third temperature detecting means 33 and the heat discharge of the fuel cell 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a temperature estimation device that estimates the temperature of a fuel cell from the temperature of water that circulates as cooling water in the fuel cell, and a fuel cell system control device that performs thawing determination of moisture according to the estimated temperature.

Conventionally, what heats a fuel cell by heating air supplied to the fuel cell according to the temperature of the fuel cell is known. According to this, since it is possible to warm up with air supplied to the fuel cell, it is possible to reduce the size of the device, improve the power generation efficiency of the fuel cell at the time of starting the system, or at the time of low temperature startup such as below freezing point The warming-up time for thawing the ice produced in is reduced. (For example, see Patent Document 1)
JP 2002-039445 A

  In the method of estimating the temperature of the air discharged from the conventional fuel cell as the temperature of the fuel cell or the method of estimating the temperature of the fuel cell from the temperature of the air supplied to the fuel cell, the fuel cell mounted on a vehicle or the like However, since the speed of temperature change differs depending on the part that detects the temperature of air or the like that estimates the temperature of the fuel cell, it is difficult to accurately estimate the temperature of the fuel cell, and the reliability of the estimated temperature is obtained. There was a problem that it was not possible.

  Therefore, an object of the present invention is to accurately estimate the temperature of the fuel cell even when the temperature of the fuel cell is estimated using the temperature of the cooling water discharged from the fuel cell having a different temperature change rate.

  The fuel cell temperature estimation apparatus according to the present invention is premised on a fuel cell comprising a circulation passage for circulating water in the fuel cell and a cooling means for cooling the water discharged from the fuel cell downstream of the heating means. The first temperature detecting means for detecting the water temperature at the fuel cell outlet, the second temperature detecting means for detecting the water temperature at the cooling means inlet, and the temperature detected by the first and second temperature detecting means. The temperature of the fuel cell is estimated on the basis of the difference in temperature and the amount of heat released from the fuel cell.

  Further, in the fuel cell system control device according to the present invention, on the premise of a fuel cell system comprising a circulation passage for circulating water in the fuel cell and a cooling means for cooling the water discharged from the fuel cell, the moisture at the fuel cell outlet First temperature detecting means for detecting temperature, second temperature detecting means for detecting moisture temperature at the inlet of the cooling means, third temperature detecting means for detecting outside air temperature, and heating the moisture in the circulation passage Heating means that heats the water in the circulation passage when the outside temperature detected by the third temperature detecting means is below freezing and the estimated temperature of the fuel cell is below freezing.

  According to the present invention, it is possible to determine whether or not the fuel cell needs to be warmed up when starting the fuel cell from the temperature of the fuel cell estimated from the temperature of moisture for cooling the fuel cell. In addition, this makes it possible to efficiently start the fuel cell at a low temperature.

  FIG. 1 shows a schematic configuration of a control device of the fuel cell system used in the first embodiment. In the present embodiment, a fuel cell 1 that generates power using a reaction gas and an oxidant gas is provided, a hydrogen-containing gas is used as the reaction gas, and an oxygen-containing gas such as air is used as the oxidant gas. The reaction gas is not limited to this, and for example, a hydrogen-containing gas reformed by a reformer can be used.

  When the operation of the fuel cell 1 is started, the temperature of the fuel cell 1 rises due to a power generation reaction. Therefore, the cooling water flow that recirculates the cooling water discharged by the fuel cell 1 to the fuel cell 1 again so as to cool the fuel cell 1. A path 37 is provided, and a pump 2 is provided so that cooling water circulates.

  At the time of starting the system below the freezing point, the cooling water freezes in the cooling water flow path 37 and it becomes difficult to circulate the cooling water. Therefore, the heater 11 for thawing the cooling water is installed downstream of the fuel cell 1 and upstream of the pump 2. And the radiator 3 which cools the cooling water heated by the electric power generation reaction of the fuel cell 1 downstream is provided.

  A three-way valve 4 that provides a bypass passage 42 so as to bypass the radiator 3 and switches the cooling water passage to one of the cooling water passage 37 and the bypass passage 42 at a portion branched from the cooling water passage 37 to the bypass passage 42. Is installed.

  A temperature sensor 32 for detecting the temperature outside the system (for example, the outside air temperature) is provided, and a temperature sensor 30 is provided downstream of the fuel cell 1 and upstream of the heater 11 so as to detect the temperature of the cooling water discharged by the fuel cell 1. The temperature sensor 33 is installed downstream of the pump 2 and upstream of the radiator 3 so as to detect the temperature of the cooling water supplied to the radiator 3. A temperature sensor 31 is installed in the bypass passage 42 to detect the temperature of the cooling water in the bypass passage 42.

  In starting the fuel cell system below the freezing point, the cooling water in the cooling water passage 37 may be frozen, so it is necessary to determine whether the cooling water is heated or thawed by the heater 11. On the other hand, in starting the fuel cell system in a temperature range exceeding the freezing point, the cooling water in the cooling water flow path 37 is not frozen and the cooling water is flowing smoothly, so that the heater 11 does not need to be heated. Therefore, when the temperature outside the system detected by the temperature sensor 32 is below freezing point, is it necessary to heat the cooling water in the cooling water flow path 37 based on the detection values obtained from the temperature sensors 30, 31 and 33 described above? Make a decision.

  While the temperature outside the fuel cell system is low and the cooling water discharged from the fuel cell 1 circulates through the cooling water flow path 37 and is supplied to the fuel cell 1 again, the cooling water is cooled by heat radiation, and the fuel cell 1 is sufficiently discharged. When the temperature of the cooling water is low enough to cool, the opening of the three-way valve 4 is adjusted so that the cooling water discharged from the fuel cell 1 bypasses the radiator 3 so that the cooling water circulates in the bypass passage 42. To do.

  Next, a method for estimating the temperature of the fuel cell 1 that is difficult to measure from the temperature at the start of starting the fuel cell system will be described.

  When the fuel cell 1 does not generate heat and is cooled by outside air, if the temperature distribution inside the fuel cell 1 is not taken into consideration, the heat dissipation amount formula (1) of the fuel cell 1 is established. Equation (2) is derived by solving the differential equation of Equation (1).

Here, C is the heat capacity of the fuel cell 1, T is the temperature of the fuel cell 1, H is the heat transfer coefficient of the fuel cell 1, A is the heat radiation area of the fuel cell 1, T ₀ is the temperature before heating of the fuel cell 1, T _air is the outside air temperature, Δt is the elapsed time during standing, β is a constant (β = −H · A / C), and α is a constant (α = L _n (T ₀ −T _air )). Arranging the constants of equation (2) as described above yields equation (3).

Similarly, Expression (4) and Expression (5) are established in the temperature sensor 30 and the temperature sensor 31 temperature detection unit. However, the temperatures TT ₁ and TT ₂ are values detected by the temperature sensor 30 and the temperature sensor 31.

Note that β used in the equations (4) and (5) is a fixed value that varies depending on the temperature detection portion. Therefore, β ₁ and β ₂ are determined from the heat capacity, heat transfer coefficient, and heat radiation area of the cooling water at each temperature measurement position. Here, since the temperatures of the two locations TT ₁ and TT ₂ immediately before the stop of the fuel cell system are substantially equal to T ₀ , α ₁ and α ₂ are also substantially equal to α. Since β ₁ and β ₂ are fixed values depending on the temperature measurement position, the elapsed time Δt and the temperature T ₀ of the cooling water path immediately before the system stop can be obtained from the equations (4) and (5). .

Accordingly, the estimated temperature T _s of the fuel cell at the time of starting the fuel cell system is also determined by using the equation (2) as the temperature T ₀ of the cooling water discharged from the fuel cell at the time of stopping the fuel cell system. The fuel cell temperature at the time can be estimated. And when this temperature is below freezing point, thawing control of the fuel cell system mentioned later is performed, and when it exceeds freezing point, starting of the fuel cell system is started.

  As described above, the temperature of the fuel cell 1 that is difficult to measure can be estimated from the temperature at the start of starting the fuel cell system, and this temperature is compared with a predetermined temperature to appropriately determine the thawing of the fuel cell system. Is possible. Here, the predetermined temperature is a temperature for determining whether or not the fuel cell 1 needs to be defrosted, and is obtained in advance by experiments or calculations and stored in a microcomputer as a database.

  In this fuel cell system, control of the fuel cell system thawing determination executed by the control unit 20 will be described with reference to the flowchart of FIG. The processing of each flowchart is periodically executed by the control unit 20.

In S201, it is determined whether or not there is a request for starting the fuel cell system. If there is no request for activation of the fuel cell system, the fuel cell system remains stopped. If there is a request for activation, the process proceeds to S202. In this step, the temperature sensor 32 detects the external temperature (T _air ) of the fuel cell system. Here, the external temperature T _air is a constant, but even if the external temperature changes during the control shown in FIG. 2, it is sufficiently smaller than the temperature change of the cooling water discharged from the fuel cell 1. The effect is negligible.

In S203, it is determined whether or not the external temperature (T _air ) detected by the temperature sensor 32 is below the freezing point. When the external temperature is higher than the freezing point, it is considered that the cooling water in the cooling water passage 37 is smoothly flowing without freezing, and the heater 11 performs normal activation without heating the cooling water. On the other hand, when the external temperature is below freezing point, it is considered that the cooling water in the cooling water passage 37 is frozen. Therefore, the thawing determination of the fuel cell system is performed by the following method.

Proceeding to S204, the temperature of each part of the system is detected by the temperature sensor 30 (T ₁ ), the temperature sensor 31 (T ₂ ), and the temperature sensor 33 (T ₃ ).

In S205, it is determined whether or not the temperatures of T ₁ , T ₂ , and T ₃ are below freezing point. If all of them are below freezing point, it is considered that the cooling water is frozen. After performing S304), the present system is activated. On the other hand, if any one of T ₁ , T ₂ , and T ₃ is above the freezing point, it is difficult to determine whether or not the cooling water of this system is frozen. Is selected as “1”, and the flow path through which the cooling water has circulated immediately before the stop of the fuel cell system is selected. Note that the reference temperature set near the freezing point does not have to be the freezing point accurately.

  When the temperature of the cooling water rises to such an extent that the cooling water discharged from the fuel cell 1 cannot be sufficiently cooled by the operation of the fuel cell 1, the cooling water discharged from the fuel cell 1 passes through the radiator 3. The opening degree of the three-way valve 4 is adjusted so as to be cooled. At this time, the cooling water flow path flag is set to “1” in the former case and “0” in the latter case. A control unit 20 composed of a microcomputer is provided so as to perform such control.

When the cooling water flow path flag is “1”, that is, when the cooling water flows through the bypass passage 42 so as to bypass the radiator 3 when the system is stopped, the process proceeds to S207 and the temperature sensor 30 and the temperature sensor 31 The detected temperature T ₁ at the start of operation is input to TT ₁ , and T ₂ is input to TT ₂ .

On the other hand, when the cooling water flow path flag is “0”, that is, when most of the cooling water is recirculating through the cooling water flow path 37 via the radiator 3 when the system is stopped, the process proceeds to S208 and the temperature sensor 30 is reached. The temperature T ₁ at the start of operation detected by the temperature sensor 33 is input to TT ₁ , and T ₃ is input to TT ₂ .

In S209, the value detected in the previous step is substituted into Expressions (4) to (5), and the temperature (T _s ) of the fuel cell 1 is estimated. In S210, when the estimated temperature of the fuel cell 1 is below freezing, the process proceeds to S211 and below-freezing thawing start control (S301 to S304) described later is performed, and then the fuel cell system is started. On the other hand, when the estimated temperature of the fuel cell 1 is higher than the freezing point, the process proceeds to S212 and the fuel cell system is activated.

Next, the below-freezing thawing start control described above will be described based on the flowchart of FIG. In S301, since the cooling water of the fuel cell system is frozen, the three-way valve is controlled so that only the cooling water passage 37 is circulated when the cooling water is thawed. In S <b> 302, the pump 2 is activated and the cooling water discharged from the fuel cell 1 circulates through the cooling water passage 37 and is supplied to the fuel cell 1 again. In step S303, the heater 11 is turned on, and the cooling water is heated and defrosted. In S304, the temperature of the cooling water discharged by the fuel cell 1 detected by the temperature sensor 30 (TT ₁ ) is increased by the heater 11 until the cooling water in the cooling water flow path 37 becomes higher than the freezing point so that the cooling water can be thawed and smoothly circulated. Continue heating the cooling water. By the above control, it becomes possible to thaw the cooling water of the fuel cell system.

  Since the temperature of the fuel cell 1 is estimated from the temperature of the cooling water discharged from the fuel cell 1 when the fuel cell 1 is started below the freezing point, the temperature of the fuel cell 1 can be grasped more accurately than before. It is possible to more accurately determine whether or not the cooling water in the water flow path 37 is thawed.

  When the fuel cell system is mounted on the vehicle, the temperature of the cooling water discharged from the fuel cell 1 and the temperature of the cooling water in the cooling water passage 37 or the temperature of the cooling water in the bypass passage 42 are greatly different if the temperature measurement portions are different. However, by selecting one of the temperature detected by the temperature sensor 30 and the temperature detected by the temperature sensor 31 or the temperature detected by the temperature sensor 33 and estimating the temperature of the fuel cell 1, the cooling can be performed more accurately. It is possible to determine whether or not the cooling water in the water channel 37 is thawed.

  In this system, the temperature of the cooling water in the cooling water flow path 37 detected by the temperature sensor 33 is longer than the part detected by the temperature sensor 31 in the distance until the cooling water heated by the fuel cell 1 arrives. Since it is easily cooled, the detection values detected by the temperature sensor 31 and the temperature sensor 33 are greatly different. Therefore, even when the temperature of the cooling water is different in each part, it is possible to estimate the temperature of the fuel cell 1 and determine whether or not the cooling water in the cooling water channel 37 is thawed.

  A schematic configuration of a control device for a fuel cell system used in the second embodiment will be described with reference to FIG. 4 with a focus on differences from the first embodiment. In the present invention, the timer 21 for measuring the time from when the fuel cell system is stopped to when it is started is provided.

  Next, in this fuel cell system, control of the fuel cell system thawing determination executed by the control unit 20 will be described with reference to the flowchart of FIG.

  In S501, it is detected whether or not there is a request for starting the system. If there is no request for starting the system, the system is not started as it is. On the other hand, if there is a request to start the system, the process proceeds to S502, and the timer 21 measures the time during which the system is stopped. Here, the details of the time measurement method (S601 to S605) by the timer 21 will not be described, but the time measurement by the timer 21 is performed from the stop of the system until a request for activation is made.

  Next, in S503 and S504, the temperature outside the system is detected by the temperature sensor 32, and it is determined whether or not the outside air temperature is below freezing point. When the outside air temperature is higher than the freezing point, it is determined that the cooling water is not frozen, and the process proceeds to S511 to start normally. When the outside air temperature is below the freezing point, the cooling water may be frozen.

S505, detects the temperature of the cooling water at the temperature sensor 30 in S506, stores the TT _0, stores the stop time fuel cell 1 obtained in S502 to △ t. Note that Δt measurement control (S601 to S6)
05) will be described later.

In S507, the fuel cell 1 starts the temperature (T _s0) and TT _0, estimates the temperature of the fuel cell 1 using the estimation method of the fuel cell 1 in S508. Here, the estimation method of the fuel cell 1 inputs the temperature TT ₀ immediately before the stop of the system into the temperature variable T _s0 of the fuel cell 1. T _s0 , the outside air temperature T _air , and the elapsed time Δt are input to T ₀ in Equation (2), and the obtained temperature T _s is set as the estimated temperature of the fuel cell 1.

  When the estimated temperature of the fuel cell 1 is below freezing in S509, it is determined that the cooling water is frozen, and the below freezing thaw starting control (S301 to S304) is performed. After the cooling water is thawed, the fuel cell 1 is started in S511. To do. On the other hand, when the estimated temperature of the fuel cell 1 is equal to or higher than the freezing point, it is determined that the cooling water is not frozen, and the process proceeds to S511 and the fuel cell 1 is started without performing the below-freezing thawing start control.

  Next, a method for measuring the time during which the system is stopped will be described with reference to FIG.

In S601, when a system stop request of the system, S602, the fuel cell 1 detects the temperature of cooling water discharged by the temperature sensor 30 in S603, and inputs the detected value of the temperature variable TT _1. In S604, the value of the temperature variable is stored in the microcomputer as a database. After that, the process proceeds to S605, and time measurement is started until there is a request for activation of this system.

The effect of 2nd Embodiment is demonstrated below. When the fuel cell 1 is stopped, the temperature of the cooling water discharged by the fuel cell 1 detected by the temperature sensor 30 is assumed to be the temperature of the fuel cell 1 at that time and stored in the microcomputer. Then, the temperature of the fuel cell 1 at the start of the system is estimated from the time (Δt) from the stop to the start of the fuel cell 1 and the external temperature of the system. Therefore, in this system, it is possible to estimate the temperature of the fuel cell 1 with only one temperature sensor for detecting the temperature of the cooling water and the system stop time, and to perform the thawing determination of the cooling water.

  The third embodiment will be described below with respect to differences from the second embodiment. The system configuration used in this embodiment is the same as that in the second embodiment.

  In the fuel cell system of the present embodiment, control of the fuel cell system thawing determination executed by the control unit 20 will be described with reference to the flowchart of FIG.

S701 to S708 describe the processing of this system from when the fuel cell 1 is stopped to when it is started. Specifically, the temperature sensor 30 detects the temperature T _s0 of the cooling water discharged from the fuel cell 1 in the temperature sensor 30 before stopping the system. Then, the external temperature (T _air ) of the present system is detected at regular time intervals (Δt), substituted into the equation (2) to estimate the temperature (T _s ) of the fuel cell 1, and the system startup request Update until it is detected. Here, the predetermined time interval is determined in advance according to the temperature change of the fuel cell 1 through experiments and calculations. The updated estimated temperature of the fuel cell 1 is stored as a database.

  If there is a system activation request in S709, the external temperature of the system is detected in S710, and if the external temperature is higher than the freezing point in S711, the fuel cell 1 is activated in S715. On the other hand, when the external temperature is below freezing point, the process proceeds to S712 and the estimated temperature of the fuel cell 1 estimated as described above is referred to.

  In S713, when the estimated temperature of the fuel cell 1 is higher than the freezing point, the fuel cell 1 is started as it is. When the estimated temperature is lower than the freezing point, the below-freezing thawing starting control is performed in S714, and the cooling water in the cooling water channel 37 is thawed, The battery 1 is activated.

  The effects of the third embodiment will be described below. By preliminarily estimating the temperature of the fuel cell 1 from the external temperature of the system detected by the temperature sensor 32 at regular time intervals from the stop of the fuel cell 1 to the start of the fuel cell 1 and the certain time, It is not necessary to estimate the temperature of the fuel cell 1 again at the time of starting the system, and it can be determined whether or not to quickly defrost.

It is obvious that the present invention is not limited to the above-described embodiments, and includes various improvements and modifications that can be made by those skilled in the art within the scope of the technical idea of the invention described in the claims. .

It is a block diagram of the system of a 1st embodiment. It is a flowchart which controls the thawing | decompression determination of the fuel cell of 1st Embodiment. It is a flowchart which controls the thawing | decompression of the fuel cell of 1st Embodiment. It is a block diagram of the system of a 2nd embodiment. It is a flowchart which controls the thawing | decompression determination of the fuel cell of 2nd Embodiment. It is a flowchart which controls the measurement of the fuel cell stop time of 2nd Embodiment. It is a flowchart which controls the thawing | decompression determination of the fuel cell of 3rd Embodiment.

Explanation of symbols

1 Fuel cell 2 Pump 3 Radiator (cooling means)
4 Three-way valve (switching means)
11 Heater (heating means)
21 Timer (measuring means)
30 Temperature sensor (first temperature detection means)
31. Temperature sensor (fourth temperature detection means)
32 Temperature sensor (third temperature detection means)
33 Temperature sensor (second temperature detection means)
37 Cooling water flow path (circulation passage)
42 Bypass passage (branch passage)

Claims (7)

A circulation passage for circulating water in the fuel cell;
In a fuel cell temperature estimation device comprising cooling means for cooling the water discharged from the fuel cell,
First temperature detecting means for detecting the moisture temperature at the fuel cell outlet;
Second temperature detecting means for detecting the moisture temperature at the cooling means inlet;
A third temperature detecting means for detecting the outside air temperature,
An apparatus for estimating a temperature of a fuel cell, wherein the temperature of the fuel cell is estimated based on a constant related to a heat radiation amount of the fuel cell and a temperature detected by the first to third temperature detecting means. A circulation passage for circulating water in the fuel cell;
In a fuel cell system control device comprising a cooling means for cooling moisture discharged from the fuel cell,
First temperature detecting means for detecting the moisture temperature at the fuel cell outlet;
Second temperature detecting means for detecting the moisture temperature at the cooling means inlet;
Third temperature detecting means for detecting the outside air temperature;
Heating means for heating the water in the circulation passage;
The fuel cell system control device, wherein when the outside air temperature detected by the third temperature detecting means is below freezing point and the estimated temperature of the fuel cell is below freezing point, the water in the circulation passage is heated. A branch passage provided in the circulation passage so as to bypass the cooling means;
Switching means for switching the flow path to the circulation path or the branch path;
A fourth temperature detecting means for detecting the temperature of moisture in the branch passage,
3. The fuel cell according to claim 2, wherein the temperature estimation unit estimates the temperature of the fuel cell based on any one of the first, second, and fourth temperature detection units. System controller. The temperature estimating means includes a temperature detected by the third temperature detecting means and the first temperature detecting means,
The temperature of the fuel cell is estimated from the temperature of the second temperature detecting means or the fourth temperature detecting means on the side where moisture has circulated when the fuel cell is stopped. Item 4. The fuel cell system control device according to Item 3. Comprising measuring means for measuring the time from stop to start of the fuel cell;
The temperature at which the temperature of the fuel cell is estimated based on the values detected by the third temperature detecting means, the first temperature detecting means, and the measuring means when the value detected by the third temperature detecting means is below freezing point. An estimation means,
3. The fuel cell system control device according to claim 2, wherein when the temperature of the fuel cell estimated by the temperature estimation unit is below freezing, the water in the circulation passage is heated.   The temperature estimation unit is configured to detect the fuel cell based on a detection temperature of the first temperature detection unit, a detection temperature of the third temperature detection unit, and a stop time of the fuel cell when the operation of the fuel cell is stopped. The fuel cell system control device according to claim 5, wherein the temperature of the fuel cell system is estimated. A circulation passage for circulating water in the fuel cell;
Heating means for heating moisture in the circulation passage;
A fuel cell system control device comprising cooling means for cooling the water discharged from the fuel cell downstream of the heating means;
First temperature detecting means for detecting the moisture temperature at the fuel cell outlet;
Second temperature detecting means for detecting the outside air temperature;
When the value detected by the second temperature detection means is below freezing point, the temperature of the fuel cell is determined based on the relationship between the second, the detection temperature of the first temperature detection means, and the predetermined time at regular intervals. Temperature estimation means for estimating,
When the temperature of the fuel cell estimated by the temperature estimating means is below freezing point, the fuel in the circulation passage is heated.

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