Electric automobile

Abstract

To provide a technique which, with a simple configuration, can eliminate a failure in passage of an electric current through a mechanical relay due to freezing.SOLUTION: An electric automobile includes: a battery; a charging inlet which can be connected to an external power source; a mechanical relay which is connected between the battery and the charging inlet, and switches connection of the battery and the charging inlet between on and off; a capacitor disposed at such a position as to be capable of being thermally coupled to the mechanical relay; a switching element connected between the capacitor and the battery; and a controller which, when an electric current cannot pass through the mechanical relay, controls the switching element to cause an electric current to pass through the capacitor from the battery via the switching element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to electric vehicles. [Background technology]

[0002] The electric vehicle includes a battery, a charging inlet configured to be connectable to an external power source, and a mechanical relay connected between the battery and the charging inlet. When the charging inlet is connected to the external power source, the mechanical relay connects the insulated wiring, so that the electric power supplied from the external power source charges the battery.

[0003] A mechanical relay is configured to switch between an ON state in which the movable element connects the wires and an OFF state in which the movable element is separated from the wires by applying a voltage to an excitation coil to move the movable element up and down. If the outside air temperature drops while the mechanical relay is OFF, ice may adhere to the contact portion where the movable element comes into contact with the wires. In this case, even if the mechanical relay tries to switch to the ON state, the contact between the movable element and the wires may be prevented. Patent Document 1 discloses an example of a technique for eliminating such electrical conduction failures in a mechanical relay caused by icing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-120380 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present specification is to provide a technique capable of eliminating a current flow failure of a mechanical relay caused by icing with a simple configuration. [Means for solving the problem]

[0006] The electric vehicle disclosed in this specification may include a battery, a charging inlet configured to be connectable to an external power source, a mechanical relay connected between the battery and the charging inlet and configured to switch the connection between the battery and the charging inlet on and off, a capacitor arranged in a position capable of being thermally coupled to the mechanical relay, a switching element connected between the capacitor and the battery, and a controller configured to control the switching element to energize the capacitor from the battery via the switching element when the mechanical relay cannot be energized.

[0007] According to the above configuration, when the mechanical relay cannot conduct electricity due to icing, the capacitor is energized to heat the capacitor, and the heat can melt the ice attached to the contacts of the mechanical relay. The electric vehicle has a simple configuration in which the capacitor is disposed at a position where it can be thermally coupled to the mechanical relay. The technology disclosed in this specification can eliminate the electrical conduction failure of the mechanical relay due to icing with a simple configuration. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of an electric vehicle. [Diagram 2] 1 is a flowchart of a dissolution process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] As shown in Fig. 1, an electric vehicle 2 includes a battery 3, an inverter 10, an electric motor 20 for driving the vehicle, and a controller 30. The dashed arrows in Fig. 1 represent signal lines.

[0010] The battery 3 is connected to the inverter 10. The positive electrode 3p of the battery 3 is connected to a DC terminal positive electrode 10p of the inverter 10, and the negative electrode 3n of the battery 3 is connected to a DC terminal negative electrode 10n of the inverter 10.

[0011] The inverter 10 includes three pairs of arm circuits 11a, 11b, and 11c. The arm circuit 11a includes an upper switching element 12a, a lower switching element 13a, a diode 14a connected in anti-parallel to the upper switching element 12a, and a diode 15a connected in anti-parallel to the lower switching element 13a. The upper switching element 12a and the lower switching element 13a are connected in series. The upper switching element 12a is connected to the positive electrode 3p of the battery 3 via the DC terminal positive electrode 10p. The lower switching element 13a is connected to the negative electrode 3n of the battery 3 via the DC terminal negative electrode 10n. The arm circuits 11b and 11c have the same structure as the arm circuit 11a, so their description will be omitted. The three pairs of arm circuits 11a, 11b, and 11c are connected in parallel between the DC terminal positive electrode 10p and the DC terminal negative electrode 10n of the inverter 10.

[0012] A capacitor 17 is connected between the DC end positive electrode 10p and the DC end negative electrode 10n of the inverter 10. The capacitor 17 is provided to suppress pulsation of the current flowing through the DC end of the inverter 10.

[0013] The upper switching elements 12a, 12b, 12c and the lower switching elements 13a, 13b, 13c of the inverter 10 are appropriately controlled by a controller 30. When the upper switching elements and the lower switching elements are alternately turned on and off, AC is output from the midpoints 16a, 16b, 16c of the three arm circuits 11a, 11b, 11c, respectively.

[0014] An electric motor 20 is connected to the midpoints 16a, 16b, and 16c. The electric motor 20 includes three coils 21a, 21b, and 21c. The three coils 21a, 21b, and 21c are wound around a stator (not shown) of the electric motor 20. One end of each of the three coils 21a, 21b, and 21c is connected to a corresponding one of the three midpoints 16a, 16b, and 16c. The other end of each of the three coils 21a, 21b, and 21c is connected to one other point. The point where the other ends of the three coils 21a, 21b, and 21c are connected to each other is called a neutral point 22. The configuration in which the other ends of the coils of each phase of the stator are connected to the neutral point 22 is called a star connection, and is a well-known circuit structure for three-phase AC motors.

[0015] The electric vehicle 2 further includes a first wiring 23p, a second wiring 23n, a mechanical charging relay 24, a charging inlet 28, a voltage sensor 32, and a capacitor 34. The charging inlet 28 is provided on the body of the electric vehicle 2. The charging inlet 28 includes a first terminal 28p and a second terminal 28n. A positive electrode 40p of the external DC power supply 40 is connected to the first terminal 28p of the charging inlet 28 via a power cable 41, and a negative electrode 40n of the external DC power supply 40 is connected to the second terminal 28n of the charging inlet 28 via the power cable 41. In this way, the external DC power supply 40 is connected to the charging inlet 28. The external DC power supply 40 may be, for example, a charging stand.

[0016] The first wiring 23p is a wiring that connects a first terminal 28p of the charging inlet 28 and the neutral point 22 of the electric motor 20. The second wiring 23n is a wiring that connects a second terminal 28n of the charging inlet 28 and the negative electrode 3n of the battery 3. The second wiring 23n is also called a ground wire. The charging relay 24 includes a first charging relay 24p provided in the first wiring 23p and a second charging relay 24n provided in the second wiring 23n.

[0017] The voltage sensor 32 is disposed between the charging relay 24 and the electric motor 20. Specifically, the voltage sensor 32 is connected between the first wiring 23p and the second wiring 23n, and is configured to measure the potential difference between the first wiring 23p and the second wiring 23n that are closer to the electric motor 20 than the charging relay 24. As will be described later, whether or not icing has occurred in the charging relay 24 can be detected based on the output of the voltage sensor 32.

[0018] The capacitor 34 is disposed between the charging relay 24 and the electric motor 20 at a position where it can be thermally coupled to the charging relay 24. Here, the term "thermally coupled position" refers to a position where heat generated in the capacitor 34 can be transferred to the charging relay 24. In this example, the first wiring 23p and the second wiring 23n are configured with metal bus bars. Therefore, the heat generated in the capacitor 34 can be transferred to the charging relay 24 via the metal bus bars of the first wiring 23p and the second wiring 23n. If necessary, a material with high thermal conductivity may be provided between the capacitor 34 and the charging relay 24 so that the heat generated in the capacitor 34 can be efficiently transferred to the charging relay 24.

[0019] (Boost circuit using electric motor 20) In the wiring from the charging inlet 28 to the battery 3, a boost circuit is formed by the lower switching element 13a and diode 14a constituting one arm circuit 11a of the inverter 10, and the coil 21a of the electric motor 20. Similarly, the lower switching element 13b, diode 14b, and coil 21b also constitute a boost circuit, and the lower switching element 13c, diode 14c, and coil 21c also constitute a boost circuit. In this way, the inverter 10 and the electric motor 20 can be regarded as three boost circuits connected in parallel between the charging inlet 28 and the battery 3. By using the inverter 10 and the electric motor 20 as a boost circuit, the electric vehicle 2 can rapidly charge the battery 3 even if the output voltage of the external DC power supply 40 is lower than that of the battery 3.

[0020] (Operation flow chart of melting process) When power cable 41 of external DC power supply 40 is connected to charging inlet 28, charging relay 24 closes and charging of electric vehicle 2 begins. Here, mechanical charging relay 24 has a problem in that if the outside air temperature drops while charging relay 24 is off, icing can prevent contact between the moving element and the wiring, resulting in poor electrical conduction. The following describes a process for melting ice that has adhered to charging relay 24 when icing occurs on charging relay 24.

[0021] FIG. 2 shows a flowchart of the melting process. When the power cable 41 of the external DC power source 40 is connected to the charging inlet 28 of the electric vehicle 2 and the user turns on a charging switch (not shown), the process of FIG. 2 is started. The controller 30 closes the charging relay 24 and determines whether or not the relay operation is executable (step S1). When the charging relay 24 executes the relay operation, the voltage sensor 32 outputs a signal corresponding to the output voltage of the external DC power source 40. If at least one of the first charging relay 24p and the second charging relay 24n of the charging relay 24 is frozen, no signal is output from the voltage sensor 32. The controller 30 can check the relay operation of the charging relay 24 based on the presence or absence of the output of the voltage sensor 32. If the relay operation of the charging relay 24 is executable, the process proceeds to step S4, and the controller 30 performs quick charging. If the relay operation of the charging relay 24 is not executable, the process proceeds to step S2. The method for checking the relay operation is not limited to the above example, and the output of the voltage sensor 32 may be determined by other logic, or the output of another sensor (such as a current sensor) may be used for the determination.

[0022] In step S2, the controller 30 applies an AC current to the capacitor 34 to ripple heat the capacitor 34. Specifically, the controller 30 turns on at least one of the upper switching elements 12a, 12b, and 12c of the inverter 10 to apply current to the capacitor 34. When a ripple current flows through the capacitor 34, the capacitor 34 generates heat due to internal resistance, and the temperature of the capacitor 34 rises. The heat generated in the capacitor 34 is transferred to the charging relay 24 via the first wiring 23p and the second wiring 23n, and melts the ice adhering to the charging relay 24. After ripple heating is performed for a predetermined time, the process proceeds to step S3.

[0023] In step S3, controller 30 again determines whether relay operation is executable. This determination process is the same as step S1. If relay operation of charging relay 24 is executable, the process proceeds to step S4, where controller 30 performs quick charging. If relay operation of charging relay 24 is not executable, the process proceeds to step S5, where controller 30 abandons charging and notifies the user that charging is not possible via a notification means (not shown).

[0024] The electric vehicle 2 disclosed in this specification is able to deal with freezing of the charging relay 24 by providing a capacitor 34 near the charging relay 24. The supply of current to the capacitor 34 for ripple heating can be achieved by controlling the inverter 10, and no dedicated circuit is required. In this way, the electric vehicle 2 disclosed in this specification is able to eliminate poor current flow in the charging relay 24 due to freezing with a simple configuration.

[0025] The above circuit configuration is an example, and the technology disclosed in this specification may be realized by other types of circuit configurations. For example, the capacitor 34 may be located at any position where it can be thermally coupled to the charging relay 24, and may not be located between the first wiring 23p and the second wiring 23n. In the above example, the ripple current is caused to flow from the battery 3 to the capacitor 34 via the inverter 10, but the present invention is not limited to this example. Various other circuit configurations that can cause a ripple current to flow from the battery 3 to the capacitor 34 when the charging relay 24 freezes, such as various circuit configurations in which a switching element is connected between the battery 3 and the capacitor 34, may be employed. [Explanation of symbols]

[0026] 2: electric vehicle, 3: battery, 10: inverter, 20: electric motor, 24: charging relay, 28: charging inlet, 30: controller, 34: capacitor, 40: external DC power supply

Claims

[Claim 1] A battery; A charging inlet configured to be connectable to an external power source; a mechanical relay connected between the battery and the charging inlet and configured to switch a connection between the battery and the charging inlet on and off; a capacitor disposed at a position capable of being thermally coupled to the mechanical relay; a switching element connected between the capacitor and the battery; and a controller configured to control the switching element to energize the capacitor from the battery through the switching element when the mechanical relay cannot be energized.

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