Field of the Invention
The present invention relates to a temperature detecting apparatus used for managing a state of an assembled battery (battery pack) formed by assembling a plurality of cells.
Description of Related Art
Conventionally, running vehicles, such as an electric vehicle (EV) and a hybrid vehicle (HEV), using an electric motor (motor) as a driving source are known. This kind of vehicle is equipped with a battery (electric storage device) for supplying electric power to the motor. As the battery, for example, a lithium ion cell is used. In a charging and discharging process of the battery (particularly, when charging is continued in a full charging state, and when a large current continues to flow according to a continuous high load state), the battery generates heat and a temperature of the battery is increased. When the temperature of the battery is increased, output characteristics of the battery can change, with the result that it is preferable to charge and discharge the battery after consideration of the temperature of the battery.
On the other hand, since the battery for driving the motor of the vehicle requires a high output voltage, an assembled battery (battery pack) formed by assembling a plurality of cells (unit cells) is generally used. In this assembled battery, the inside of the assembled battery may have a temperature distribution resulting from the fact that the extent of heat dissipation varies every cell, with the result that it is desirable to manage a temperature every cell.
For example, one conventional temperature detecting apparatus (hereinafter called a “conventional apparatus”) is configured to detect a temperature of an assembled battery (battery pack) using a plurality of temperature sensors. Concretely, in the conventional apparatus, the plurality of temperature sensors (with the number smaller than the number of cells) are arranged along an arrangement direction of the cells in the assembled battery. As one example, three temperature sensors are arranged for 100 or more cells in the conventional apparatus. And, the conventional apparatus is configured to estimate the temperature of the inside of the assembled battery based on output values of the temperature sensors and other parameters (for example, an ambient temperature or a cooling air volume). In addition, as the temperature sensor, a temperature-sensitive element such as a thermistor is used (for example, see Patent Document 1: JP-A-2011-222133).
[Patent Document 1] JP-A-2011-222133
According to a related art, an apparatus estimates a temperature of an assembled battery by temperature sensors with the number smaller than the number of cells. As a result, there are cases where the conventional apparatus cannot grasp a temperature state of the inside of the assembled battery with high resolution when the number of temperature sensors is insufficient with respect to the number of cells. Further, since the conventional apparatus is provided with a pair of detection lines (wiring connected to the temperature sensors) for each of the temperature sensors, when the number of temperature sensors is increased in order to increase resolution of temperature detection, the number of detection lines is also increased in proportion to the number of temperature sensors. As a result, many detection lines are cabled in limited space of the inside of a case in which the assembled battery is stored, and cabling work of the detection lines may become complicated. Thus, the conventional apparatus has an antinomy relation between an improvement in the resolution of temperature detection and workability of the cabling of the detection lines.