JP2017033835A - Fuel cell stack cooling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently control a flow rate of cooling water flowing in a cooling water flow passage without measuring nor estimating an intake/outlet temperature difference of the cooling water for cooling a fuel cell stack.SOLUTION: A fuel cell stack cooling apparatus 100 comprises a cooling water flow passage 9, an outlet temperature sensor 8, a radiator 5, a radiator fan 6, a cooling water pump 7, and an ECU 4 controlling the rotating speed of the radiator fan 6 and the rotating speed of the cooling water pump 7. The ECU 4 controls the rotating speed of the radiator fan 6 according to a fan rotating speed command value Rf, and controls the rotating speed of the cooling water pump 7 according to a pump rotating speed command value Rp, a first feedback term Fb1 of the fan rotating speed command value Rf having a first integral element In1, and a second feedback term Fb2 of the pump rotating speed command value Rp varying according to a second integral element In2 smaller in gain than the first integral element In1 as the rotating speed of the radiator fan 6 decreases.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell stack cooling device.

  In the fuel cell stack included in the fuel cell system mounted on the vehicle, hydrogen as fuel gas supplied from the hydrogen tank reacts with oxygen in the air supplied from the compressor to generate electric energy. As described in Patent Document 1, such a fuel cell system is provided with a cooling device that circulates cooling water through the fuel cell stack to prevent temperature rise of the fuel cell stack. The cooling device of Patent Document 1 has a cooling water passage through which cooling water for cooling the fuel cell stack circulates. A part of the cooling water flow path passes through the inside of the fuel cell stack, the point where the cooling water flows out from the inside of the fuel cell stack to the outside is the cooling water outlet of the fuel cell stack, and the cooling water is outside the fuel cell stack. The point that flows in from the inside is the cooling water inlet. And the radiator which is a heat exchanger is provided in a cooling water flow path, and the cooling water which distribute | circulates the inside of a radiator is cooled with the wind blown from a radiator fan. The radiator fan is controlled based on the temperature of the cooling water measured by the sensor, and the temperature of the cooling water decreases as the number of revolutions of the radiator fan increases.

  Furthermore, in order to efficiently cool the fuel cell stack, in the cooling water flow path, the inlet temperature of the cooling water flowing near the cooling water inlet of the fuel cell stack and the outlet temperature of the cooling water flowing near the cooling water outlet The temperature difference, that is, the inlet / outlet temperature difference needs to be within a predetermined value. In order to keep the temperature difference within a certain value and to circulate the cooling water by a necessary amount to reliably cool the fuel cell stack, the cooling water flow rate is controlled by the cooling water pump.

JP 2007-027047 A

In Patent Document 1, the cooling water outlet temperature is estimated based on the cooling water inlet temperature measured by a sensor. However, when the rotation speed of the radiator fan suddenly increases or decreases, the temperature of the cooling water that actually flows through the cooling water flow path fluctuates later than the change in the rotation speed of the radiator fan. There may be unevenness in the temperature of the cooling water. Therefore, even if the outlet temperature of the cooling water is estimated based on the inlet temperature of the cooling water, the temperature difference between the inlet and outlet of the cooling water cannot be accurately grasped.
Further, Patent Document 1 includes an example in which a temperature sensor is provided at each of the inlet and outlet of the fuel cell stack in the cooling water flow path, but the manufacturing cost of the cooling device is increased by providing two sensors.

  The present invention is made to solve such a problem, and can efficiently control the flow rate of the cooling water flowing through the cooling water flow path without measuring or estimating the temperature difference between the inlet and outlet of the cooling water. An object is to provide a stack cooling device.

  In order to solve the above problems, a fuel cell stack cooling device according to the present invention includes a fuel cell stack that generates electricity by reacting oxygen and fuel gas, and a cooling that is connected to the fuel cell stack and cools the fuel cell stack. A cooling water flow path through which water flows, a cooling water temperature detection means for detecting the temperature of the cooling water provided in the cooling water flow path, a radiator provided in the cooling water flow path through which the cooling water flows, and an air flow to the radiator A radiator fan that cools the cooling water, a cooling water pump that circulates the cooling water in the cooling water flow path, a cooling water temperature detection means, a radiator fan, and a cooling water pump that are electrically connected to the rotation of the radiator fan. Control means for controlling the number and the number of revolutions of the cooling water pump, the control means controls the number of revolutions of the radiator fan based on a predetermined fan revolution number command value, The rotation speed of the cooling water pump is controlled based on a constant pump rotation speed command value, and the fan rotation speed command value has a first feedback term based on the temperature of the cooling water, and the first feedback term is the first The pump rotational speed command value has a second feedback term based on the temperature of the cooling water, and the second feedback term is a first feedback term as the rotational speed of the radiator fan decreases. It fluctuates according to the second integral element whose gain is smaller than that of the integral element.

  Further, the second feedback term of the pump rotational speed command value of the fuel cell stack cooling device according to the present invention is the third integral having a gain larger than that of the first integral element as the rotational speed of the radiator fan is increased. It may vary depending on factors.

  In addition, the second feedback term may be varied according to the larger integral element by comparing the second integral element and the third integral element.

  Further, the cooling water channel has a cooling water outlet at a point where the cooling water flows from the inside to the outside of the fuel cell stack, and the cooling water temperature detecting means is downstream of the cooling water outlet of the fuel cell stack in the cooling water channel. In addition, the temperature of the cooling water upstream of the radiator may be detected.

  According to the fuel cell stack cooling device of the present invention, the flow rate of the cooling water flowing through the cooling water passage can be efficiently controlled without measuring or estimating the temperature difference between the inlet and outlet of the cooling water for cooling the fuel cell stack. Can do.

It is a figure which shows typically the structure of the fuel cell stack cooling device which concerns on embodiment of this invention. It is a block diagram which shows control of the fuel cell stack cooling device shown in FIG. 2 is a graph showing a relationship among a coolant outlet temperature, a fan fan rotational speed command value of a radiator fan, and a pump rotational speed command value of a cooling water pump in the fuel cell stack cooling device shown in FIG.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The fuel cell system 200 includes a fuel cell stack 1 having a plurality of cells (not shown), a hydrogen tank 2 capable of supplying hydrogen gas as a fuel gas to the fuel cell stack 1, and oxygen in the fuel cell stack 1. And a compressor 3 capable of supplying air. In each cell of the fuel cell stack 1, the hydrogen supplied from the hydrogen tank 2 and the oxygen in the air supplied by the compressor 3 cause a chemical reaction to generate power. The fuel cell stack 1 is connected to a cooling water passage 9 through which cooling water for cooling the fuel cell stack 1 flows and circulates. Some of the cooling water passages 9 a are provided outside the fuel cell stack 1, while the other part of the passages 9 b are provided inside the fuel cell stack 1. Here, a point where the cooling water flows out from the cooling water flow path 9b inside the fuel cell stack 1 to the external cooling water flow path 9a is defined as a flow path outlet 9c. Further, a point at which cooling water flows from the cooling water flow path 9a outside the fuel cell stack 1 to the internal cooling water flow path 9b is defined as a flow path inlet 9d. In addition, an outlet temperature sensor 8 is attached to the cooling water passage 9 downstream of the passage outlet 9c.

Further, a radiator 5 is provided in the cooling water flow path 9 on the downstream side of the outlet temperature sensor 8. Further, a radiator fan 6 is provided adjacent to the radiator 5 so as to be able to blow air to the radiator 5. The radiator fan 6 is rotationally driven by a radiator fan motor 6a. Further, in the cooling water flow path 9, a cooling water pump 7 is provided on the downstream side of the radiator 5 and the upstream side of the flow path inlet 9 d to boost the cooling water and circulate it through the cooling water flow path 9. Note that when the number of rotations of the cooling water pump 7 increases, the flow rate of the cooling water also increases, and the cooling function for the fuel cell stack 1 is improved. On the other hand, when the rotational speed of the cooling water pump 7 decreases, the flow rate of the cooling water also decreases.
Furthermore, the ECU 4 is electrically connected to the solenoid valve 2a of the hydrogen tank 2, the compressor 3, the radiator fan motor 6a, the cooling water pump 7 and the outlet temperature sensor 8.
Here, the outlet temperature sensor 8 constitutes cooling water temperature detection means for detecting the temperature of the cooling water. Moreover, ECU4 comprises a control means.
Furthermore, the fuel cell stack 1, ECU 4, radiator 5, radiator fan 6, cooling water pump 7, outlet temperature sensor 8, and cooling water flow path 9 constitute the fuel cell stack cooling device 100 according to this embodiment.

Next, the operation of the fuel cell stack cooling device 100 of the fuel cell system 200 will be described.
The cooling water flowing through the cooling water flow path 9 of the fuel cell stack cooling device 100 is first pressurized by the cooling water pump 7 and flows into the cooling water flow path 9b inside the fuel cell stack 1 from the flow path inlet 9d. And the cooling water which distribute | circulates the cooling water flow path 9b cools each cell of the fuel cell stack 1, and flows out into the cooling water flow path 9a outside the fuel cell stack 1 after passing through the flow path outlet 9c. Next, the cooling water flowing through the cooling water flow path 9 a flows into the radiator 5 and is cooled by the wind blown from the radiator fan 6 toward the radiator 5. Further, the cooling water that has flowed out of the radiator 5 is increased in pressure again by the cooling water pump 7 provided on the downstream side of the radiator 5 and circulates in the cooling water passage 9.

The ECU 4 calculates a fan rotation speed command value Rf based on the coolant outlet temperature Tout detected by the outlet temperature sensor 8, and controls the radiator fan motor 6a based on the fan rotation speed command value Rf. The fan rotation speed command value Rf has a first feedback term Fb1 based on the coolant outlet temperature Tout. The first feedback term Fb1 includes a first integral element In1 that is a command value that varies based on a change in the coolant outlet temperature Tout.
Further, the ECU 4 calculates a pump rotation speed command value Rp based on the cooling water outlet temperature Tout, and controls the rotation speed of the cooling water pump 7 based on the pump rotation speed command value Rp. The pump rotation speed command value Rp has a second feedback term Fb2 based on the coolant outlet temperature Tout.
Here, the cooling water outlet temperature Tout refers to the temperature of the cooling water downstream of the flow path outlet 9c of the cooling water flow path and upstream of the radiator 5. Further, the cooling water inlet temperature Tin refers to the temperature of the cooling water upstream of the flow path inlet 9 d of the cooling water flow path and downstream of the cooling water pump 7.

  Furthermore, the ECU 4 can adjust the amount of hydrogen and air supplied to the fuel cell stack 1 by controlling the opening and closing of the electromagnetic valve 2 a of the hydrogen tank 2 and the compressor 3. That is, the ECU 4 controls the power generation amount of the fuel cell stack 1.

Next, a method for calculating the pump rotation speed command value Rp by the ECU 4 will be described with reference to FIG.
First, the ECU 4 calculates a current command value Cv, which is a current value generated by the fuel cell stack 1, in the current command value calculation unit 11, based on the accelerator opening, the vehicle request, and the like. Then, the pump rotation speed calculation unit 12 of the ECU 4 corresponds to the current command value Cv based on a predetermined map M1 indicating the relationship between the current value generated by the fuel cell stack 1 and the rotation speed of the coolant pump 7. The rotational speed Rp1 of the cooling water pump 7 to be calculated is calculated. Then, the feedforward term storage unit 13 of the ECU 4 stores the rotational speed Rp1 as the feedforward term Ff of the pump rotational speed command value Rp.

Further, the target temperature calculation unit 14 of the ECU 4 calculates the target temperature Tt of the cooling water from the power generation amount of the fuel cell stack 1 and the like. The temperature difference calculation unit 15 of the ECU 4 calculates a temperature difference ΔT between the coolant outlet temperature Tout detected by the outlet temperature sensor 8 and the target temperature Tt. Next, the second integration element integration unit 16 of the ECU 4 calculates a second integration element In2 with the temperature difference ΔT as an input value. At the same time, the third integration element integration unit 17 of the ECU 4 calculates a third integration element In3 with the temperature difference ΔT as an input value.
Here, the gain k2 of the second integration element In2 is smaller than the gain k3 of the third integration element In3. When the gain k1 of the first integral element In1 of the fan rotational speed command value Rf with respect to the temperature difference ΔT is 1, the gain k2 of the second integral element In2 takes a value of 0.1 to 0.7, and The gain k3 of the third integral element In3 takes a value of 3-10. Accordingly, the gain k2 of the second integral element In2 is smaller than the gain k1 of the first integral element In1, and the gain k3 of the third integral element In3 is larger than the gain k1 of the first integral element In1. That is, the gains k1 to k3 have a relationship of k2 <k1 <k3.

Next, the integration element selection unit 18 of the ECU 4 compares the second integration element In2 and the third integration element In3, and selects the one with the larger value. Then, the feedback term storage unit 19 of the ECU 4 stores the selected second or third integral element as the second feedback term Fb2 of the pump rotation speed command value Rp.
The pump rotation speed command value calculation unit 20 of the ECU 4 adds the feedforward term Ff stored in the feedforward term storage unit 13 and the feedback term Fb stored in the feedback term storage unit 19, and a value obtained as a result Is calculated as a pump rotation speed command value Rp.
The rotational speed of the cooling water pump 7 is controlled by the pump rotational speed command value Rp thus calculated. And since the flow volume of the cooling water which distribute | circulates the cooling water flow path 9 changes with the fluctuation | variation of the rotation speed of the cooling water pump 7, the cooling water outlet temperature Tout also fluctuates with it. Therefore, the ECU 4 repeats calculating the pump rotation speed command value Rp again based on the cooling water outlet temperature Tout that varies in this way.

Furthermore, with reference to FIG. 3, the fluctuation | variation of the fan rotation speed command value Rf and the pump rotation speed command value Rp based on the change of the cooling water outlet temperature Tout detected by the outlet temperature sensor 8 is demonstrated.
The pump rotation speed command value Rp varies between the rotation speed lower limit value Lp and the rotation speed upper limit value Hp of the cooling water pump 7. Also, the alternate long and short dash line in the graph indicates the pump rotation speed command when the second integral element In2 is selected as the second feedback term Fb2 under the assumption that the rotation speed upper limit value Hp of the cooling water pump 7 does not exist. This is a virtual line representing the transition of the value Rp = Lp + In2. Further, the two-dot chain line in the graph indicates the pump speed when the third integral element In3 is selected as the second feedback term Fb2 under the assumption that the rotation speed upper limit value Hp of the cooling water pump 7 does not exist. This is a virtual line representing the transition of the command value Rp = Lp + In3.
Here, the rotation speed lower limit Lp of the cooling water pump 7 is a value determined mainly based on the feedforward term Ff of the pump rotation speed command value Rp. Further, the rotation speed upper limit value Hp of the cooling water pump 7 is a value calculated based on the performance of the cooling water pump 7 and the like.
Further, the times t1 to t6 are sequentially passed from t1 to t6.

  First, the cooling water outlet temperature Tout according to the example of FIG. 3 gradually increases with respect to the target temperature Tt until the time t2 is reached. Here, the fan rotation speed command value Rf has, as the first feedback term Fb1, a first integration element In1 that has a temperature difference ΔT between the cooling water outlet temperature Tout and the target temperature Tt as an input value. Accordingly, the fan rotational speed command value Rf increases as the cooling water outlet temperature Tout increases. Regarding the pump rotation speed command value Rp, when the cooling water outlet temperature Tout is rising, the imaginary line Lp + In3 exceeds the imaginary line Lp + In2, and therefore the third integration element In3 is used as the second feedback term Fb2. Selected. That is, as the fan rotational speed command value Rf increases, the second feedback term Fb2 of the pump rotational speed command value Rp varies according to the third integral element In3. Therefore, even when compared with the increase in fan rotational speed command value Rf, pump rotational speed command value Rp increases more rapidly and reaches rotational speed upper limit value Hp at time t2.

Next, as the rotational speed of the radiator fan 6 and the rotational speed of the cooling water pump 7 are increased, the cooling water outlet temperature Tout gradually decreases after time t1 and decreases to the target temperature Tt at time t3. However, the cooling water outlet temperature Tout continues to decrease so as to be lower than the target temperature Tt even after time t3.
Here, the fan rotation speed command value Rf increases until time t3, and then gradually decreases after time t3. Further, the virtual line Lp + In2 and the virtual line Lp + In3 of the pump rotation speed command value Rp also draw a trajectory that gradually decreases after time t3 after increasing to time t3. From time t1 to time t4, the virtual line Lp + In3 exceeds the rotation speed upper limit value Hp of the cooling water pump 7. Accordingly, the pump rotation speed command value Rp rapidly decreases along the virtual line Lp + In3 from time t4 to time t5 after holding a constant rotation speed Rp = Hp from time t1 to time t4. Then, after time t5, since the value of the virtual line Lp + In2 exceeds the value of the virtual line Lp + In3, the pump rotation speed command value Rp is switched to the value of the virtual line Lp + In2 and gradually decreases. That is, as the fan rotational speed command value Rf decreases, the second feedback term Fb2 of the pump rotational speed command value Rp varies according to the second integral element In2.
Furthermore, the cooling water outlet temperature Tout rises again from time t4 due to the decrease in the rotational speed of the radiator fan 6 and the rotational speed of the cooling water pump 7.

  As described above, in the fuel cell stack cooling device 100 according to this embodiment, when the rotational speed of the radiator fan 6 decreases, the rotational speed of the cooling water pump 7 is the first integral element In1 of the fan rotational speed command value Rf. The gain fluctuates according to the second integration element In2 having a smaller gain. That is, the rotational speed of the cooling water pump 7 is gradually decreased as compared with the decrease in the rotational speed of the radiator fan 6. Accordingly, in consideration of the case where the temperature of the cooling water is delayed due to the decrease in the cooling fan temperature due to the decrease in the rotation speed of the radiator fan 6 and the temperature unevenness occurs in the cooling water flow path 9, the cooling water pump 7 is rotated at a slightly higher rotation speed. It is possible to suppress the fluctuation of the temperature difference between the channel outlet 9c and the channel inlet 9d by continuing to rotate. Therefore, the ECU 4 can more efficiently control the amount of cooling water circulated by the cooling water pump 7.

  Further, when the rotational speed of the radiator fan 6 increases, the rotational speed of the cooling water pump 7 varies in accordance with the third integral element In3 having a gain larger than that of the first integral element In1 of the fan rotational speed command value Rf. To do. That is, the rotational speed of the cooling water pump 7 increases more rapidly than the increase in the rotational speed of the radiator fan 6. Thereby, prior to the temperature drop of the cooling water, the cooling water pump 7 can increase the flow rate of the cooling water, and can cool the fuel cell stack 1 more efficiently.

  Further, by comparing the second integral element In2 and the third integral element In3 of the pump rotational speed command value Rp and selecting the larger one, the degree of change in the rotational speed of the cooling water pump 7 is moderated. Can be switched more appropriately, and the flow rate of the cooling water can be controlled more efficiently.

  Furthermore, even in the cooling water flow path 9, temperature unevenness due to a change in the rotational speed of the radiator fan 6 tends to occur on the downstream side of the radiator 5. Therefore, the outlet temperature sensor 8 as the cooling water temperature detecting means detects the cooling water outlet temperature Tout on the downstream side of the flow passage outlet 9c and the upstream side of the radiator 5, thereby more accurately detecting the temperature of the cooling water. be able to.

  DESCRIPTION OF SYMBOLS 1 Fuel cell stack, 4 ECU (control means), 5 Radiator, 6 Radiator fan, 7 Cooling water pump, 8 Outlet temperature sensor (cooling water temperature detection means), 9 Cooling water flow path, 9c Cooling water outlet, 100 Fuel cell stack Cooling device, Fb1 first feedback term, Fb2 second feedback term, In1 first integral element, In2 second integral element, In3 third integral element, Rf fan rotational speed command value, Rp pump rotational speed command value.

Claims (4)

A fuel cell stack for generating electricity by reacting oxygen and fuel gas; and
A cooling water passage connected to the fuel cell stack and through which cooling water for cooling the fuel cell stack flows;
Cooling water temperature detecting means provided in the cooling water flow path for detecting the temperature of the cooling water;
A radiator provided in the cooling water flow path, through which the cooling water flows;
A radiator fan that blows air to the radiator to cool the cooling water;
A cooling water pump for circulating the cooling water in the cooling water flow path;
The cooling water temperature detecting means, electrically connected to the radiator fan and the cooling water pump, and comprising a control means for controlling the rotational speed of the radiator fan and the rotational speed of the cooling water pump,
The control means includes
Controlling the rotation speed of the radiator fan based on a predetermined fan rotation speed command value;
Controlling the number of revolutions of the cooling water pump based on a predetermined pump revolution number command value;
The fan rotation speed command value has a first feedback term based on the temperature of the cooling water, and the first feedback term has a first integral element,
The pump rotation speed command value has a second feedback term based on the temperature of the cooling water,
The fuel cell stack cooling device, wherein the second feedback term varies according to a second integral element having a gain smaller than that of the first integral element as the rotational speed of the radiator fan decreases.   2. The fuel according to claim 1, wherein the second feedback term varies according to a third integral element having a gain larger than that of the first integral element as the rotational speed of the radiator fan increases. Battery stack cooling device.   3. The fuel cell stack cooling device according to claim 2, wherein the second feedback term varies according to an integral element having a larger value by comparing the second integral element and the third integral element. 4. The cooling water flow path has a cooling water outlet at a point where the cooling water flows from the inside of the fuel cell stack to the outside,
The fuel cell stack cooling device according to any one of claims 1 to 3, wherein the cooling water temperature detecting means detects a temperature of the cooling water downstream of the cooling water outlet and upstream of the radiator.

Images