Steering system

Abstract

To provide a highly practical steering system.SOLUTION: In a two-system steering system, a power source system includes: a first bus 82a and a second bus 82b communicating with each other via a breaker 80; a first power source 84a and a second power source 84b connected to the first bus and the second bus, respectively; and a backup power source 88 having a battery and capable of supplying power to both first systems 60a, 62a and second systems 60b, 62b. When one of the first bus and the second bus is grounded, the communication between the first bus and the second bus is interrupted by the breaker, and power is supplied from the backup power source to both the first system and the second system. With the backup power supply, it is possible to prevent the steering system from falling in a state in which both the first system and the second system cannot operate properly during a time lag from the detection of the ground fault to the operation of the breaker.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a steering system mounted on a vehicle. [Background technology]

[0002] Regarding power supply systems for various devices such as steering devices mounted on vehicles, there is a technology described in the following Patent Document, for example: This technology includes a main power supply system having a normal load group including several devices and an auxiliary power supply, and a backup power supply system having a backup load group including several devices, and in the event of a failure in the main power supply system, the converter serving as the main power supply is stopped, and then the connection line connecting the two systems under normal circumstances is cut off, and the devices in the backup load group are operated by the power supply from the converter serving as the backup power supply in the backup power supply system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-32346 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in the above patent document, the connection line is cut off in the event of a main power supply failure, but there is a possibility of a time lag between the detection of a main power supply failure and the cutting off of the connection line. If a time lag occurs, a state may occur in which power is not supplied to both the normal load group and the backup load group. If this state occurs, it is expected that the backup load group will not operate normally after the connection line is cut off. By avoiding such a situation, it is possible to improve the practicality of systems configured including equipment installed in a vehicle, such as steering systems. The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a highly practical steering system. [Means for solving the problem]

[0005] In order to solve the above problems, the steering system of the present invention comprises: A steering system mounted on a vehicle, The steering system is divided into two systems, a first system and a second system, each of which has a steering device with a power source; a control drive device which is divided into two systems, a first system and a second system, for controlling and driving the first system and the second system of the steering device, each of which has a driver for driving the power source and a controller for controlling the driver; two power supply buses connected in series to each other, the first bus being connected to a first system of the control drive device to supply power thereto, and the second bus being connected to a second system of the control drive device to supply power thereto; a circuit breaker that disconnects the first bus from the second bus; a first power supply connected to the first bus and a second power supply connected to the second bus; a backup power supply device having a battery and capable of supplying power from the battery; and The steering system is configured so that, under normal circumstances, with the first bus and the second bus in communication, power is supplied from at least one of the first power source and the second power source, and when a ground fault occurs in one of the first bus and the second bus, the first bus and the second bus are cut off by the circuit breaker, and power is supplied from either the first power source or the second power source connected to the other of the first bus and the second bus to one of the first system and the second system of the control drive device connected to the other of the first bus and the second bus, and The backup power supply device is configured to pass power supplied from at least one of the first bus and the second bus through itself, and when the power supply is cut off, to automatically supply power from its own battery to at least the controllers of both the first system and the second system of the control drive device. [Effects of the Invention]

[0006] A "ground fault" refers to a short circuit between a bus and a component at ground potential. Normally, if a ground fault occurs in either the first bus or the second bus, the other bus between the first bus and the second bus will also be grounded because the first bus and the second bus are connected. As a result, power is not supplied from either the first power source or the second power source to either the first system or the second system of the control drive device. To avoid this situation, when a ground fault occurs in either the first bus or the second bus, a circuit breaker cuts off the connection between the first bus and the second bus, and power from either the first power source or the second power source is supplied to either the first system or the second system of the control drive device via the other bus.

[0007] However, when a ground fault occurs in either the first bus or the second bus, there is a time lag between the detection of the ground fault and the circuit breaker cutting off communication between the first bus and the second bus, resulting in a state in which power is not supplied to either the first or second system of the control drive device, even if it is for a short time. In particular, if power is not supplied to the controller, the control by the controller is reset, and even if power is supplied again, neither the first nor second system of the steering device will be able to operate normally.

[0008] The "backup power supply device" is a device for avoiding this state, and can prevent a situation in which power is not supplied to both the first and second controllers of the control drive device when a ground fault occurs. By having the above configuration, the steering system of the present invention is highly practical.

[0009] The "steering device" in the steering system of the present invention (hereinafter sometimes referred to as "the present steering system") is configured to include at least an actuator for steering the wheels or assisting in steering the wheels. The actuator may be configured to include, for example, an electric motor as the drive source. When the power source is an electric motor, the steering device can be configured as a two-system motor, for example. Incidentally, when the electric motor is a DC brushless motor, the electric motor can be configured as a two-system motor, for example, by configuring the stator to include two sets of coils.

[0010] The "control drive device" is a device that controls and drives the steering device, more specifically, a device that controls the power source of the steering device. The two-system control drive device is composed of two drivers and two controllers corresponding to the two systems of the steering device. The "driver" can also be called a drive circuit; for example, if the power source is a DC brushless motor, an inverter can be used as the driver. The "controller" can also be composed of, for example, a computer as a main component.

[0011] The "first bus" and the "second bus" are both power supply lines, i.e., so-called electric wires, and may be in the form of bus bars. The first bus and the second bus supply power to the first system and the second system of the control drive device, respectively, but may also be connected to other systems, such as a brake system, to supply power to those systems as well. The "circuit breaker" may be a switch that switches between interconnection and non-communication between the two buses.

[0012] The power sources functioning as the "first power source" and the "second power source" may be, for example, in the case of electric vehicles such as battery electric vehicles and hybrid electric vehicles, a converter that converts high-voltage power from a drive battery that supplies power to a drive motor for driving the vehicle into low-voltage power, or may be an auxiliary battery such as a conventional lead battery. A "backup power supply device" is configured to include the above-mentioned "battery" inside, and the battery may be a power storage device with a small storage capacity known as a capacitor. Note that two or more of each of the first power source and the second power source may be provided.

[0013] The configuration of the "backup power supply device," specifically, the configuration for automatically supplying power from its own battery when power supply from both the first bus and the second bus is cut off, will be described in detail later.

[0014] The backup power supply device may be configured to supply power from the battery to only the controller of the driver and the controller for both the first and second systems of the control drive device. Such a configuration makes it possible to use a battery with a relatively small capacity. The backup power supply device may also be configured to be able to supply power from the battery to both the driver and the controller for at least one of the first and second systems of the control drive device. If power can be supplied to both the driver and the controller, a battery with a relatively large capacity is required, but proper operation of at least one of the steering devices is ensured even during the time lag, and the operation of the steering system when the ground fault occurs can be made more reliable.

[0015] Furthermore, the number of backup power supplies is not limited to one. For example, the backup power supplies may be configured to include a first backup power supply capable of supplying power to the first system of the control drive device and a second backup power supply capable of supplying power to the second system of the control drive device.

[0016] The steering system may be a so-called steer-by-wire type steering system. In the case of a steer-by-wire type steering system, the steering system may be configured such that each of the first and second systems of the steering device includes a steering actuator having a power source for steering the wheels, and a reaction force actuator having another power source for applying an operation reaction force to the steering operation member, and each of the first and second systems of the control drive device includes a control drive device for the steering actuator and a control drive device for the reaction force actuator. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing the overall configuration of a steering system according to an embodiment, and a diagram showing the configuration of an electronic control unit serving as a drive control device. [Figure 2]1 is a diagram showing a schematic diagram of the internal configuration of a power supply system of a steering system according to an embodiment, and a backup power supply device that constitutes the power supply system; [Figure 3] FIG. 1 is a diagram schematically illustrating the internal configuration of a conventional power supply system and a backup power supply device that constitutes the power supply system. [Figure 4] 10A and 10B are diagrams showing a first modified power supply system and a second modified power supply system that can be employed in the steering system of the embodiment; [Figure 5] FIG. 10 is a diagram schematically illustrating a power supply system according to a third modified example that can be employed in the steering system of the embodiment, and the internal configuration of a backup power supply device that constitutes the power supply system. [Figure 6] 10 is a flowchart of a termination processing program executed to terminate the operation of the electronic control unit. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, as a mode for carrying out the present invention, a steering system according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition to the following embodiment, the present invention can be carried out in various forms including the form described in the above section "Modes of the Invention" and various modifications and improvements based on the knowledge of those skilled in the art. [Example]

[0019] [A] Overall configuration of steering system The steering system of the embodiment (hereinafter sometimes referred to as "the present steering system") mounted on a vehicle is a system for steering two wheels (front wheels) 10, each of which is a steerable wheel, as shown schematically in FIG. 1(a), and is a steer-by-wire type steering system equipped with a reaction force actuator 12 and a steering actuator 14 that are mechanically independent of each other.

[0020] The reaction force actuator 12 has a function of accepting operation of a steering wheel 20 as an operating member that is operated by a driver (steering operation), and is configured to include: a) a steering shaft 22 to the tip of which the steering wheel 20 is attached; b) a steering column 24 that rotatably holds the steering shaft 22 and is supported by an instrument panel reinforcement (not shown); and d) a reaction force applying mechanism 28 that is provided on the steering column 24 and uses a reaction force motor 26, which is an electric motor, as a power source to apply an operation reaction force, which is a reaction force against the steering operation, to the steering wheel 20 via the steering shaft 22. The reaction force actuator 12 has a general structure, so a description of its specific structure will be omitted.

[0021] The reaction force motor 26 is a three-phase brushless DC motor with magnets attached to the outer periphery of the rotating shaft and coils arranged in the housing to face the magnets. The reaction force motor 26 is a two-system motor with two sets of coils arranged for one magnet. Hereinafter, each of the two systems may be referred to as a first reaction force motor 26a and a second reaction force motor 26b. In other words, the reaction force actuator 12 is composed of two systems of actuators (hereinafter, sometimes referred to as the "first reaction force actuator 12a" and the "second reaction force actuator 12b") that serve as redundant systems for each other.

[0022] Each of the wheels 10 is supported on the vehicle body via a steering knuckle 40, which is a component of a suspension system, so that it can be steered. Steering actuator 14 steers the two wheels 10 as a single unit by rotating steering knuckle 40. Steering actuator 14 is configured to include: (a) a steering rod (sometimes called a "rack bar") 46, both ends of which are connected to the left and right steering knuckles 40 via link rods 44, respectively; (b) a housing 48 that supports steering rod 46 so that it can move laterally and is fixedly held to the vehicle body; and (c) a rod moving mechanism 52 that uses steering motor 50, which is an electric motor, as a power source to move steering rod 46 laterally. Rod moving mechanism 52 mainly comprises a ball screw mechanism that includes a ball groove threaded into steering rod 46 and a nut that threadably engages with the ball groove via a bearing ball and is rotated by steering motor 50. Steering actuator 14 has a general structure, so a detailed description of its structure will be omitted.

[0023] Steering motor 50 is also a two-system three-phase brushless DC motor having a structure similar to that of reaction motor 26. Hereinafter, each of the two systems may be referred to as first steering motor 50a and second steering motor 50b. Therefore, steering actuator 14 is made up of two systems of actuators (hereinafter, sometimes referred to as "first steering actuator 14a" and "second steering actuator 14b") which are redundant systems for each other.

[0024] Control of reaction force actuator 12, more specifically, control of operation reaction force, i.e., control of reaction force motor 26, is performed by two reaction force electronic control units (hereinafter sometimes referred to as "reaction force ECUs") 60a, 60b, which are respective control drive devices, corresponding to the two systems of reaction force actuator 12. More specifically, control of first reaction force actuator 12a is performed by first reaction force ECU 60a, and control of second reaction force actuator 12b is performed by second reaction force ECU 60b. Similarly, control of steering actuator 14, more specifically, control related to wheel steering, i.e., control of steering motor 50, is performed by two steering electronic control units (hereinafter sometimes referred to as "steering ECUs") 62a, 62b, which are respective control drive devices, corresponding to the two systems of steering actuator 14. More specifically, first steering actuator 14a is controlled and driven by first steering ECU 62a, and second steering actuator 14b is controlled and driven by second steering ECU 62b. Incidentally, first reaction force ECU 60a and second reaction force ECU 60b will sometimes be collectively referred to as reaction force ECU 60, and first turning ECU 62a and second turning ECU 62b will sometimes be collectively referred to as turning ECU 62. In the drawings, first reaction force ECU 60a, second reaction force ECU 60b, first turning ECU 62a and second turning ECU 62b are represented as C-ECU 60a, C-ECU 60b, S-ECU 62a and S-ECU 62b, respectively.

[0025] As shown in FIG. 1(b), reaction force ECU 60 and steering ECU 62 (hereinafter sometimes collectively referred to as "ECUs 60, 62") each have an inverter 64, which is a driver (drive circuit), and a controller 66 that controls it. Controller 66 is configured with a computer, which is comprised of a CPU, ROM, RAM, etc., as its main components. Power is supplied to inverter 64 and controller 66 from a bus, which will be described later. More specifically, power (hereinafter sometimes referred to as "PIG power") is supplied to inverter 64 via a power supply line indicated as "PGI" in the figure, and power (hereinafter sometimes referred to as "IG power") is supplied to controller 66 via a power supply line indicated as "IG" in the figure. A control signal is sent from controller 66 to inverter 64, and inverter 64 operates based on the control signal and supplies drive current I to reaction force motor 26 and steering motor 50. Both the PIG power and the IG power are supplied to reaction force ECU 60 and steering ECU 62 at the same voltage, but because controller 66 operates at a relatively low voltage, IG power is supplied to controller 66 via step-down converter 68. The PIG power is used to drive reaction force motor 26 and steering motor 50, and is therefore larger than the IG power. In other words, a fairly large current is supplied to inverter 64.

[0026] Considering this steering system as a whole, first reaction force actuator 12a, first turning actuator 14a, first reaction force ECU 60a, and first turning ECU 62a constitute a first system, and second reaction force actuator 12b, second turning actuator 14b, second reaction force ECU 60b, and second turning ECU 62b constitute a second system, making it a two-system system. From another perspective, first reaction force actuator 12a and second reaction force actuator 12b function as the first and second systems of one reaction force actuator 12, and first turning actuator 14a and second turning actuator 14b function as the first and second systems of one turning actuator 14. Furthermore, it can be considered that the first system of one steering device is made up of first reaction force actuator 12a and first steering actuator 14a, and the second system of the same steering device is made up of second reaction force actuator 12b and second steering actuator 14b. One of the first system and the second system may be called the main system, and the other may be called the sub-system.

[0027] As shown in Figure 1(a), first reaction force ECU 60a and first steering ECU 62a are connected by a first dedicated communication line 70a, and second reaction force ECU 60b and second steering ECU 62b are connected by a first dedicated communication line 70b. In order to enable communication with reaction force ECUs 60 and steering ECUs 62 of different systems and to enable communication with other systems, each reaction force ECU 60 and each steering ECU 62 is connected to a CAN (car area network or controllable area network) 72 as a common communication line. Note that the control of operation reaction force and control related to wheel steering by reaction force ECU 60 and steering ECU 62 is common control, so a description thereof will be omitted here. Incidentally, under normal circumstances, first reaction force actuator 12a and first steering actuator 14a each bear half of the overall required operation reaction force, and first steering actuator 14a and second steering actuator 14b each bear half of the overall required steering force (the force exerted to steer the wheels).

[0028] [B] Power System This steering system is equipped with a power supply system as shown in Fig. 2(a). More specifically, the power supply system has a first bus 82a and a second bus 82b (hereinafter sometimes collectively referred to as "buses 82"), which are two power supply lines arranged in series with each other via a circuit breaker 80. Normally, the first bus 82a and the second bus 82b are connected to each other, and when an event occurs, the circuit breaker 80 cuts off the connection. Both the first bus 82a and the second bus 82b are arranged in the form of bus bars.

[0029] A first converter 84a, which serves as a first power source, is connected to the first bus 82a, and a second converter 84b, which serves as a second power source, is connected to the second bus 82b. The first converter 84a and the second converter 84b (represented as "DC-DCa" and "DC-DCb" in the figure) are respectively supplied with power from a high-voltage drive battery mounted on the vehicle and supply the power to the first bus 82a and the second bus 82b. An auxiliary battery (represented as "AB" in the figure) 86, which functions as a second power source, is connected to the second bus 82b. This auxiliary battery 86 is a so-called lead battery. Although not shown in the figure, other devices such as brake devices are also connected to the first bus 82a and the second bus 82b, and the first converter 84a, the second converter 84b, and the auxiliary battery 86 also supply power to these other devices. Although detailed description will be omitted, the auxiliary battery 86 also has the function of storing regenerated power from the steering device and other devices. In the following description, the first converter 84a, the second converter 84b, and the auxiliary battery 86 may be collectively referred to as the "normal power supply."

[0030] Although a detailed explanation will be omitted, the voltage of the power from the second converter 84b is slightly lower than the voltage of the power from the first converter 84a, and power is normally supplied from the first converter 84a. When the communication between the first bus 82a and the second bus 82b is cut off by the circuit breaker 80, power can be supplied to the first bus 82a from the first converter 84a, and to the second bus 82b from the second converter 84b.

[0031] First bus 82a is connected to first reaction force ECU 60a and first turning ECU 62a, each of which constitutes a first system of the control drive device, and second bus 82b is connected to second reaction force ECU 60b and second turning ECU 62b, each of which constitutes a second system of the control drive device. More specifically, first reaction force ECU 60a and first turning ECU 62a are connected to first bus 82a so that PIG power is input directly from first bus 82a, and second reaction force ECU 60b and second turning ECU 62b are connected to second bus 82b so that PIG power is input directly from second bus 82b.

[0032] On the other hand, the power supply system includes a backup power supply device (represented as "BPS" in the figure), and first reaction force ECU 60a and first turning ECU 62a are connected to first bus 82a so that IG power is input from first bus 82a via backup power supply device 88, and second reaction force ECU 60b and second turning ECU 62b are connected to second bus 82b so that IG power is input from second bus 82b via backup power supply device 88. More specifically, backup power supply 88 has an internal configuration as shown schematically in FIG. 2(b), and IG power from first bus 82a passes through backup power supply device 88 to be supplied to first reaction force ECU 60a and first turning ECU 62a, and IG power from second bus 82b passes through backup power supply device 88 to be supplied to second reaction force ECU 60b and second turning ECU 62b.

[0033] More specifically, the backup power supply 88 comprises four rectifiers 90 that allow current to pass in one direction while prohibiting current from passing in the reverse direction, and a capacitor (represented as "CAP" in the figure) 92, which is a battery with a relatively small capacity. In more detail, the four rectifiers 90 are all so-called diodes, and include a first main rectifier 90am provided on a first main path 94a for outputting IG power from the first bus 82a to the first reaction force ECU 60a and the first steering ECU 62a, a second main rectifier 90bm provided on a second main path 94b for outputting IG power from the second bus 82b to the second reaction force ECU 60b and the second steering ECU 62b, a first sub-rectifier 90as provided on a first sub-path 96a connecting the capacitor 92 and the downstream portion of the first main rectifier 90am on the first main path 94a, and a second sub-rectifier 90bs provided on a second sub-path 96b connecting the capacitor 92 and the downstream portion of the second main rectifier 90bm on the second main path 94b.

[0034] Capacitor 92 is capable of supplying power at a voltage slightly lower than the voltage of the IG power supplied from first bus 82a and second bus 82b. Therefore, when IG power is supplied from first bus 82a, the IG power is supplied to first reaction force ECU 60a and first turning ECU 62a, and when IG power is supplied from second bus 82b, the IG power is supplied to second reaction force ECU 60b and second turning ECU 62b. When the supply of IG power from first bus 82a is cut off, the power from capacitor 92 is supplied as IG power to first reaction force ECU 60a and first turning ECU 62a, and when the supply of IG power from second bus 82b is cut off, the power from capacitor 92 is supplied as IG power to second reaction force ECU 60b and second turning ECU 62b. In other words, the backup power supply device 88 is configured to allow the IG power supplied to the ECUs 60, 62 of the first and second systems from the first bus 82a and the second bus 82b, respectively, to pass through itself, and to automatically, i.e., without any special control, supply IG power to both the ECUs 60, 62 of the first and second systems from its own battery when the supply of IG power from both the first bus 82a and the second bus 82b is cut off. In other words, the backup power supply device 88 is configured to use the voltage difference to instantly, i.e., without any time lag, switch the power supply source from the normal power source to its own battery. The backup power supply device may also supply PIG power, but because the capacitance of the capacitor 92 is small, it can only supply power for a relatively short period of time when it also supplies PIG power.

[0035] Incidentally, although not shown in the figure, the backup power supply device 88 has a circuit that receives power from at least one of the first bus 82a and the second bus 82b and charges the capacitor 92, and under normal circumstances, the capacitor 92 is maintained in a charged state.

[0036] 2(a), switches (represented as "SW" in the figure) 98, which are switches, are provided between first bus 82a and each of first converter 84a, first reaction force ECU 60a, first turning ECU 62a, and backup power supply device 88, and between second bus 82b and each of second converter 84b, second reaction force ECU 60b, second turning ECU 62b, and backup power supply device 88. Simply put, these switches 98 are closed when the ignition switch of the vehicle is turned on, and are open when the ignition switch is turned off. While a detailed description will be omitted, the operation of these switches 98 and the operation of the circuit breaker 80 described above are controlled by a domain controller (represented as "DCNT" in the figure) 100, which is a control device.

[0037] [C] Problems and solutions when a bus has a ground fault In this steering system having the above-described power supply system (hereinafter sometimes referred to as the "power supply system of the embodiment"), as explained above, under normal circumstances, the first bus 82a and the second bus 82b are connected, and power is supplied from the first converter 84a to all of the first reaction force ECU 60a, the first turning ECU 62a, the second reaction force ECU 60b, and the second turning ECU 62b.

[0038] In this steering system, for example, consider a case where a ground fault, i.e., a short circuit that causes a voltage drop to ground potential, occurs in first bus 82a, as shown by the two-dot chain line in Figure 2(a). In this case, because first bus 82a and second bus 82b are connected to each other, power is not supplied to reaction force ECUs 60a, 60b or steering ECUs 62a, 62b from first converter 84a, second converter 84b, or auxiliary battery 86. Therefore, in this steering system, when a ground fault like the one described above occurs, circuit breaker 80 cuts off communication between first bus 82a and second bus 82b, ensuring power supply from second converter 84b via second bus 82b to second reaction force ECU 60b and second steering ECU 62b.

[0039] However, when a ground fault occurs, there is a certain time lag between detecting the ground fault and activating circuit breaker 80. During this time lag, that is, until the power supply from second converter 84b to second reaction force ECU 60b and second turning ECU 62b is restored, a problem occurs in that power is not supplied to either second reaction force ECU 60b or second turning ECU 62b. Specifically, if the supply of IG power to controller 66 of ECU 60 is interrupted even for a moment, the operation of controller 66 is reset. Therefore, if a ground fault occurs in first bus 82a, even if the power supply to second reaction force ECU 60b and second turning ECU 62b is restored, the second system of the steering device will not operate properly. In other words, a problem may occur in which both the first system and the second system of the steering device will not operate properly.

[0040] To address the above problem, in the present steering system, even during the time lag, the supply of IG power to second reaction force ECU 60b and controller 66 of second steering ECU 62b is automatically continued from backup power supply device 88. Therefore, after the power supply from second converter 84b is restored, that power ensures proper operation of the second system of the steering device.

[0041] The above description is for the case where the first bus 82a has a ground fault, but a similar problem occurs when the second bus 82b has a ground fault. Although a detailed description is omitted, even if a time lag occurs due to a ground fault in the second bus 82b, IG power is automatically supplied from the backup power supply device 88 to the first reaction force ECU 60a and the controller 66 of the first steering ECU 62a during that time lag. Therefore, after the power supply from the first converter 84a via the first bus 82a is restored, that power ensures proper operation of the first system of the steering device. In other words, in this steering system, proper operation of either the first system or the second system of the steering device is ensured even if a ground fault occurs in either the first bus 82a or the second bus 82b.

[0042] [D] Conventional power supply systems A conventional power supply system is shown in Fig. 3(a). In the following description, the same components as those in the power supply system of the steering system of the embodiment will be given the same reference numerals, and detailed description thereof will be omitted.

[0043] In the conventional power supply system, backup power supply device 110 is configured to back up only the first system. More specifically, when the supply of power from first bus 82a is cut off, backup power supply device 110 is configured to supply not only IG power but also PIG power from capacitor 92 to first reaction force ECU 60a and first steering ECU 62a.

[0044] Incidentally, because the backup power supply 110 requires a relatively large current supply for PIG power, it is possible to switch from power supply from the first bus 82a to power supply from the capacitor 92 by means of a semiconductor switching element 112, rather than a rectifier 90. Although a detailed explanation will be omitted, the backup power supply 110 has a built-in controller, and the operation of the switching element 112 is controlled by the controller depending on the power from the capacitor 92.

[0045] In a conventional power supply system, for example, if a ground fault occurs in second bus 82b, circuit breaker 80 cuts off communication between first bus 82a and second bus 82b. Even during the time until power supply from first bus 82a is restored, backup power supply device 110 ensures that the supply of IG power to first reaction force ECU 60a and first steering ECU 62a is uninterrupted. After power supply from first bus 82a is restored, that power maintains proper operation of the first system of the steering device. Incidentally, the second system of the steering device ceases to operate when a ground fault occurs.

[0046] In contrast, when a ground fault occurs in the first bus 82a, power is not supplied to the second reaction force ECU 60b and the second turning ECU 62b, and the operation of their controllers 66 is reset, from the time the ground fault occurs until the circuit breaker 80 cuts off communication between the first bus 82a and the second bus 82b. As a result, even if the power supply from the second bus 82b is restored, the second system of the steering system does not operate properly. Meanwhile, the first system of the steering system operates by receiving power from the backup power supply 110, but it only operates until the amount of electricity stored in the capacitor 92 is depleted, and this operation time is relatively short. In other words, in a conventional power supply system, when a ground fault occurs in the first bus 82a, only the first system of the steering system operates properly, but this operation does not continue for a sufficient period of time. Conventional power supply systems have such problems.

[0047] As explained above, in the steering system of the embodiment, even if a ground fault occurs in either the first bus 82a or the second bus 82b, proper operation of either the first system or the second system of the steering device is guaranteed for a sufficient period of time, thereby solving the problems associated with the conventional power supply systems described above.

[0048] [D] Modified power supply system The steering system of the embodiment can operate with several power supply systems other than the power supply system of the embodiment described above. Some modified examples of the power supply system that can be used in the steering system of the embodiment will be briefly described below.

[0049] As shown in FIG. 4(a), the power supply system of the first modified example is a system in which a backup power supply device 110, which is employed in conventional power supply systems, is provided not only on the first system side but also on the second system side. Although this system requires two backup power supplies, even if a ground fault occurs in either the first bus 82a or the second bus 82b, IG power is supplied to all of the first reaction force ECU 60a, the first turning ECU 62a, the second reaction force ECU 60b, and the second turning ECU 62b during the time lag described above. Therefore, one of the first system and the second system of the steering device on the side where the ground fault does not occur continues to operate properly once the power supply from either the first bus 82a or the second bus 82b is restored. The other of the first system and the second system of the steering device on the side where the ground fault occurs continues to operate properly as long as the power stored in the capacitor 92 of the backup power supply device 110 continues. Although this power supply system requires two backup power supplies, it can construct a more reliable steering system.

[0050] It should be noted that in this power supply system, the two backup power supplies can be considered to constitute one backup power supply that automatically supplies power from its own battery to all of controllers 66 of first reaction force ECU 60a, first turning ECU 62a, second reaction force ECU 60b, and second turning ECU 62b when the supply of power from both first bus 82a and second bus 82b is cut off. It should be noted that in backup power supply device 110, the source of PIG power may be automatically switched by rectifier 90 between first bus 82a or second bus 82b and capacitor 92, as in the case of IG power.

[0051] 4(b), the power supply system of the second modified example is configured so that IG power is also supplied to second reaction force ECU 60b and second steering ECU 62b via backup power supply device 110, which is employed in conventional power supply systems. Therefore, unlike conventional power supply systems, even if a ground fault occurs in first bus 82a, the above-mentioned time lag does not occur in the second system of the steering device, and proper operation of the second system of the steering device is maintained by the restoration of power supply from second bus 82b.

[0052] As shown in Fig. 5(a), the power supply system of the third modified example has one backup power supply device 120, and backup power supply device 120 has one capacitor 122. As shown in Fig. 5(b), backup power supply device 120 receives IG power and PIG power from first bus 82a and second bus 82b, respectively, and is configured to supply IG power and PIG power from capacitor 122 to first reaction force ECU 60a, first turning ECU 62, second reaction force ECU 60b, and second turning ECU 62b when the power supply from first bus 82a and second bus 82b is cut off.

[0053] According to this power supply system, similar to the power supply system of the first modification, even if a ground fault occurs in either the first bus 82a or the second bus 82b, IG power is supplied to all of the first reaction force ECU 60a, the first turning ECU 62a, the second reaction force ECU 60b, and the second turning ECU 62b during the time lag described above. After the power supply from either the first bus 82a or the second bus 82b, which is not affected by the ground fault, is restored, that power maintains proper operation of either the first system or the second system of the steering device. Then, either the first system or the second system of the steering device on the ground fault side operates properly, although only until the power stored in the capacitor 122 is depleted. Incidentally, compared to the capacitor 92 of the backup power supply device 110 of the power supply system of the first modification, the capacitor 122 of the backup power supply device 120 of this power supply system has a larger capacity, so that the proper operation time of either the first system or the second system of the steering device on the ground fault side is relatively long. In the backup power supply device 120, the source of the PIG power may also be automatically switched by the rectifier 90 between either the first bus 82a or the second bus 82b and the capacitor 122, as in the case of the IG power.

[0054] Several power supply systems have been described above, and in each of the power supply systems, the first converter 84a is connected to the first bus 82a, and the second converter 84b and the auxiliary battery 86 are connected to the second bus 82b. A power supply system that can be used in the steering system of the embodiment may have the auxiliary battery 86 connected to the first bus 82a, or may have both the first converter 84a and the second converter 84b connected to one of the first bus 82a and the second bus 82b, and only the auxiliary battery 86 connected to the other.

[0055] [E] Termination process of control drive unit First reaction force ECU 60a, first turning ECU 62a, second reaction force ECU 60b, and second turning ECU 62b each execute a process to terminate their own operation. In a steering system without a backup power supply, for example, the operation of each ECU is terminated when two conditions are met: power is not actually being supplied from the normal power supply, that is, the corresponding switch 98 is in a closed state, and the power (voltage) supplied to each ECU is reduced. Incidentally, switch open / close information, which is information about the open / close status of the corresponding switch 98, is transmitted by domain controller 100 via CAN 72.

[0056] However, when a power supply system equipped with a backup power supply device is used, power is supplied from the backup power supply device even when power is not being supplied from the normal power supply, so it is not desirable to terminate the operation of the backup power supply device itself when the above two conditions are met. Therefore, in the steering system of the embodiment, the backup power supply devices 88, 110, 120 detect the BPS input voltage, which is the voltage on the input side, and transmit a BPS input voltage signal, which is a signal regarding the BPS input voltage, to the ECUs 60, 62 via the CAN 72. The corresponding ECUs 60, 62 terminate their own processing based on the signal.

[0057] Specifically, controller 66 of ECU 60, 62 connected to the backup power supply device terminates its own operation in accordance with a termination processing program shown in the flowchart of FIG. 6. To explain the termination processing in accordance with the flowchart, controller 66 of ECU 60, 62 first acquires switch open / close information in step 1 (hereinafter abbreviated as "S1"; the same applies to the other steps), and then receives a BPS input voltage signal in step S2. Then, when two conditions are met in step S3: switch 98 is closed, and the BPS input voltage of backup power supply device 88, 110, 120 is low (for example, approximately 0 V), controller 66 terminates its own operation in step S4. That is, the operation of reaction force actuator 12 and steering actuator 14, which are controlled and driven by ECU 60, 62 that includes controller 66, is terminated. This termination processing program is repeatedly executed at short time intervals. [Explanation of symbols]

[0058] 10: Wheel 12: Reaction force actuator (steering device) 12a: First reaction force actuator (first system) 12b: Second reaction force actuator (second system) 14: Turning actuator (steering device) 14a: First turning actuator (first system) 14b: Second turning actuator (second system) 26: Reaction force motor (power source) 50: Turning motor (power source) 60: Reaction force electronic control unit (reaction force ECU) (control drive device) 60a: First reaction force ECU (first system) 60b: Second reaction force ECU (second system) 62: Turning electronic control unit (turning ECU) (control drive device) 62a: First turning ECU (first system) 62b: Second turning ECU (second system) 64: Inverter (driver) 66: Controller 80: Circuit breaker 82a: First bus 82b: Second bus 84a: First converter (first power supply) 84b: Second converter (second power supply) 86: Auxiliary battery (second power supply) 88: Backup power supply unit 90: Rectifier 92: Capacitor (battery) 110: Backup power supply unit 112: Switching element 120: Backup power supply unit 122: Capacitor (battery) PIG: Power supply line (to driver) IG: Power supply line (to controller) I: Drive current

Claims

1. A steering system mounted on a vehicle, a steering device having two systems, a first system and a second system, each of which has a power source; a control drive device which is divided into two systems, a first system and a second system, for controlling and driving the first system and the second system of the steering device, each of which has a driver for driving the power source and a controller for controlling the driver; two power supply buses connected in series to each other, the first bus being connected to a first system of the control drive device to supply power thereto, and the second bus being connected to a second system of the control drive device to supply power thereto; a circuit breaker that disconnects the first bus from the second bus; a first power supply connected to the first bus and a second power supply connected to the second bus; a backup power supply device having a battery and capable of supplying power from the battery; and The steering system is configured so that, under normal circumstances, with the first bus and the second bus in communication, power is supplied from at least one of the first power source and the second power source, and when a ground fault occurs in one of the first bus and the second bus, the first bus and the second bus are cut off by the circuit breaker, and power is supplied from either the first power source or the second power source connected to the other of the first bus and the second bus to one of the first system and the second system of the control drive device connected to the other of the first bus and the second bus, and A steering system in which the backup power supply device passes power supplied from at least one of the first bus and the second bus through itself, and when the power supply is cut off, automatically supplies power from its own battery to at least the controllers of both the first system and the second system of the control drive device.

2. The steering system A steer-by-wire type steering system, each of the first system and the second system of the steering device includes a steering actuator having the power source and steering wheels, and a reaction force actuator having another power source and applying an operation reaction force to a steering operation member; 2. The steering system according to claim 1, wherein each of the first and second control drive systems includes the control drive system for the steering actuator and the control drive system for the reaction force actuator.

3. 2. The steering system according to claim 1, wherein the backup power supply device is configured to supply power from the battery only to the controller of the driver and the controller for both the first system and the second system of the control drive device.

4. 2. The steering system according to claim 1, wherein the backup power supply device is configured to supply power from the battery to both the driver and the controller for at least one of the first system and the second system of the control drive device.

5. 2. The steering system according to claim 1, wherein the backup power supply device includes a first backup power supply device capable of supplying power to a first system of the control drive device, and a second backup power supply device capable of supplying power to a second system of the control drive device.

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