Circuit system

Abstract

To provide a technique capable of extending a period until a first relay fails while suppressing the first relay and a second relay from failing at the same time.SOLUTION: A circuit system includes: a series circuit in which a battery, an electrical load, a first relay, and a second relay are connected in series; a first deterioration detection unit that detects a first deterioration level of the first relay; a second deterioration detection unit that detects a second deterioration level of the second relay; and a control device that controls operations of the first relay and the second relay. The control device is configured to be able to execute a first operating mode in which the operations of the first relay and the second relay are controlled so that a difference value obtained by subtracting the second deterioration level from the first deterioration level becomes a predetermined value, and a second operating mode in which the operations of the first relay and the second relay are controlled so that the difference value is maintained at the predetermined value after the difference value becomes the predetermined value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a circuit system. [Background technology]

[0002] Patent Document 1 discloses a circuit system including a series circuit in which a battery, an electrical load, a first relay, and a second relay are connected in series, and a control device that controls the operation of the first relay and the second relay. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-266276 Summary of the Invention [Problem to be solved by the invention]

[0004] In one embodiment of Patent Document 1, when electrically connecting a battery to an electrical load, first the first relay is closed, and then the second relay is closed. When electrically disconnecting the battery from the electrical load, first the second relay is opened, and then the first relay is opened. In this case, the first relay and the second relay deteriorate in the same manner. As a result, the first relay and the second relay may fail at the same time.

[0005] In another embodiment of Patent Document 1, when electrically connecting the battery to the electrical load, the first relay is closed first, and then the second relay is closed. When electrically disconnecting the battery from the electrical load, the first relay is opened first, and then the second relay is opened. In this case, the deterioration of the first relay is accelerated compared to the deterioration of the second relay. This can cause the first relay to fail relatively early.

[0006] The present specification provides a technique that can extend the period until the first relay fails while preventing the first relay and the second relay from failing at the same time. [Means for solving the problem]

[0007] In a first aspect disclosed in the present specification, a circuit system includes a series circuit in which a battery, an electrical load, a first relay, and a second relay are connected in series, a first deterioration detection unit that detects a first deterioration level of the first relay, a second deterioration detection unit that detects a second deterioration level of the second relay, and a control device that controls operation of the first relay and the second relay, wherein the control device is configured to be able to execute a first operation mode in which operation of the first relay and the second relay is controlled so that a difference value obtained by subtracting the second deterioration level from the first deterioration level becomes a predetermined value, and a second operation mode in which operation of the first relay and the second relay is controlled so that the difference value becomes the predetermined value and is maintained at the predetermined value.

[0008] According to the above configuration, after the differential value becomes equal to or less than the predetermined value, the control device controls the operation of the first relay and the second relay so that the differential value is maintained at the predetermined value. By maintaining the differential value at the predetermined value, it is possible to prevent the first relay and the second relay from failing at the same time. Furthermore, because the differential value is maintained at the predetermined value, it is possible to prevent the first deterioration level from becoming larger than the second deterioration level. Therefore, it is possible to extend the period until the first relay fails. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram of a circuit system 2. [Figure 2] FIG. 4 is a diagram showing a first relay temperature and a second relay temperature in an initial state. [Figure 3] FIG. 10 is a diagram showing the temperature of a first relay and the temperature of a second relay after deterioration. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Example) A circuit system 2 will be described with reference to Fig. 1. As an example, the circuit system 2 is installed in a hybrid vehicle or an electric vehicle. The circuit system 2 includes a series circuit 10, a control device 12, a first temperature sensor 14, and a second temperature sensor 16.

[0011] The series circuit 10 includes a positive power line 20, a negative power line 22, a battery 24, an electrical load 26, a positive relay 28, and a negative relay 30. As an example, the electrical load 26 is a traction motor. The positive power line 20 electrically connects the positive electrode of the battery 24 to the electrical load 26. The negative power line 22 electrically connects the negative electrode of the battery 24 to the electrical load 26. The positive relay 28 and the negative relay 30 are provided on the positive power line 20 and the negative power line 22, respectively. A first temperature sensor 14 and a second temperature sensor 16 detect the temperatures of the positive relay 28 and the negative relay 30, respectively. Hereinafter, the temperatures detected by the first temperature sensor 14 and the second temperature sensor 16 will be referred to as the "first relay temperature" and the "second relay temperature," respectively.

[0012] The control device 12 includes a CPU and memories such as ROM and RAM. The control device 12 controls the operation of the positive relay 28 and the negative relay 30 based on the first relay temperature and the second relay temperature. The control device 12 is configured to be able to execute a first operation mode in which the operation of the positive relay 28 and the negative relay 30 is controlled so that the differential temperature, obtained by subtracting the second relay temperature from the first relay temperature, becomes a threshold temperature L (see FIG. 3 ), and a second operation mode in which the operation of the positive relay 28 and the negative relay 30 is controlled so that the differential temperature is maintained at the threshold temperature L after the differential temperature becomes the threshold temperature L. Here, maintaining the differential temperature at the threshold temperature L includes not only a case where the differential temperature and the threshold temperature L are completely identical, but also a case where the differential temperature and the threshold temperature L are slightly different (e.g., 5°C).

[0013] 2 and 3, the first and second operating modes executed by the control device 12 will be described. Figures 2 and 3 show the first and second relay temperatures when a predetermined current flows through the series circuit 10.

[0014] 2 shows the first relay temperature and the second relay temperature in the initial state. In the initial state, the positive relay 28 and the negative relay 30 have the same contact resistance, so the first relay temperature and the second relay temperature are the same.

[0015] As the relay deteriorates, the contact resistance increases, and the amount of heat generated by the relay increases. Therefore, as the relay deteriorates, the relay temperature increases when a predetermined current flows through the series circuit 10. In other words, the higher the relay temperature, the higher the degree of deterioration of the relay. Therefore, the first relay temperature and the second relay temperature correspond to the first degree of deterioration of the positive-side relay 28 and the second degree of deterioration of the negative-side relay 30, respectively.

[0016] In the first operating mode, the control device 12 controls the operation of the positive side relay 28 and the negative side relay 30 so that the difference temperature between the first relay temperature and the second relay temperature becomes the threshold temperature L. The threshold temperature L is a threshold for preventing the positive side relay 28 and the negative side relay 30 from failing at the same time. In this embodiment, the control device 12 executes a first relay operation. The first relay operation includes a first relay closing operation and a first relay opening operation. In the first relay closing operation, when electrically connecting the battery 24 to the electrical load 26, the negative side relay 30 is first closed, and then the positive side relay 28 is closed. In the first relay opening operation, when electrically disconnecting the battery 24 from the electrical load 26, the positive side relay 28 is first opened, and then the negative side relay 30 is opened. As a result, the deterioration rate of the positive side relay 28 becomes faster than the deterioration rate of the negative side relay 30. As a result, the temperature difference increases, and as a result, the temperature difference reaches the threshold temperature L, as shown in FIG.

[0017] Thereafter, the control device 12 executes a second operation mode in which the operation of the positive side relay 28 and the negative side relay 30 is controlled so as to maintain the differential temperature at the threshold temperature L. In this embodiment, the control device 12 alternately executes the first relay operation and the second relay operation. The second relay operation includes a second relay closing operation and a second relay opening operation. In the second relay closing operation, when electrically connecting the battery 24 to the electrical load 26, the positive side relay 28 is closed first, and then the negative side relay 30 is closed. In the second relay opening operation, when electrically disconnecting the battery 24 from the electrical load 26, the negative side relay 30 is opened first, and then the positive side relay 28 is opened. As a result, the deterioration rates of the positive side relay 28 and the negative side relay 30 become the same, and the differential temperature is maintained at the threshold temperature L.

[0018] As described above, the circuit system 2 includes a series circuit 10 in which a battery 24, an electrical load 26, a positive side relay 28, and a negative side relay 30 are connected in series, a first temperature sensor 14 (an example of a "first deterioration detection unit") that detects a first relay temperature of the positive side relay 28 (an example of a "first deterioration level"), a second temperature sensor 16 (an example of a "second deterioration detection unit") that detects a second relay temperature of the negative side relay 30 (an example of a "second deterioration level"), and a control device 12 that controls the operation of the positive side relay 28 and the negative side relay 30. The control device 12 is configured to be able to execute a first operating mode in which the operation of the positive side relay 28 and the negative side relay 30 is controlled so that the differential temperature (an example of a "differential value") obtained by subtracting the second relay temperature from the first relay temperature becomes the threshold temperature L (an example of a "predetermined value"), and a second operating mode in which the operation of the positive side relay 28 and the negative side relay 30 is controlled so that the differential temperature is maintained at the threshold temperature L after the differential temperature becomes the threshold temperature L.

[0019] According to the above configuration, after the differential temperature reaches the threshold temperature L, the control device 12 controls the operation of the positive relay 28 and the negative relay 30 so that the differential temperature is maintained at the threshold temperature L. By maintaining the differential temperature at the threshold temperature L, it is possible to prevent the positive relay 28 and the second relay from failing at the same time. Furthermore, because the differential temperature is maintained at the threshold temperature L, it is possible to prevent the first degree of deterioration from becoming larger than the second degree of deterioration. Therefore, it is possible to lengthen the period until the positive relay 28 fails.

[0020] (First Modification) The series circuit 10 may have three or more relays.

[0021] (Second Modification) The negative relay 30 and the positive relay 28 may be examples of the "first relay" and the "second relay", respectively.

[0022] (Third Modification) In the first operation mode, the control device 12 may execute a second relay closing operation and a second relay opening operation in addition to the first relay closing operation and the first relay opening operation.

[0023] (Fourth Modification) In the second operation mode, the control device 12 does not have to alternately perform the first relay operation and the second relay operation. [Explanation of symbols]

[0024] 2: Circuit system, 10: Series circuit, 12: Control device, 14: First temperature sensor, 16: Second temperature sensor, 20: Positive power supply line, 22: Negative power supply line, 24: Battery, 26: Electrical load, 28: First relay, 30: Second relay

Claims

[Claim 1] a series circuit in which a battery, an electrical load, a first relay, and a second relay are connected in series; a first deterioration detection unit that detects a first deterioration degree of the first relay; a second deterioration detection unit that detects a second deterioration degree of the second relay; a control device that controls the operation of the first relay and the second relay, The control device a first operation mode in which operations of the first relay and the second relay are controlled so that a difference value obtained by subtracting the second deterioration degree from the first deterioration degree becomes a predetermined value; a second operation mode in which operations of the first relay and the second relay are controlled so that the difference value is maintained at the predetermined value after the difference value has reached the predetermined value. Circuit system.

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