CONTROL UNIT

A control unit includes multiple controllers, an intersystem communication circuit, an internal power supply circuit and a protection circuit. The controllers control a load, and are connected to individual circuit arrangements. The individual circuit arrangements are defined as systems. The intersystem communication circuit is connected between one of the systems and remainder of the systems. The internal power supply circuit is included in each system. The internal power supply circuit supplies electric power to corresponding one of the controllers and the intersystem communication circuit. The protection circuit cuts off an internal power supply line between the internal power supply circuit and the intersystem communication circuit or limits supply of the electric power to the intersystem communication circuit, in response to the occurrence of an overvoltage abnormality in which an output voltage of the internal power supply circuit is in an overvoltage state.

TECHNICAL FIELD

The present disclosure relates to a control unit.

BACKGROUND

An electric power steering system may be equipped with redundant drive. For example, there may be galvanic isolation between two drive electronic devices.

SUMMARY

The present disclosure describes a control unit having multiple controllers, an intersystem communication circuit, an internal power supply circuit, and a protection circuit.

DETAILED DESCRIPTION

In a control circuit included in multiple systems, if a fault occurs in which a voltage of an internal power supply that supplies electric power to a microcomputer or other devices increases, the normal control circuit may have a breakdown due to an increase in the voltage of the communication line. As a countermeasure for the above-mentioned situation, it is possible to provide an isolated communication buffer such as a photocoupler for intersystem communication. Since the isolated communication buffer is a relatively large element, it is necessary to secure a relatively large mounting area on a board.

According to an aspect of the present disclosure, a control unit includes multiple controllers, an intersystem communication circuit, an internal power supply circuit and a protection circuit. The controllers control a load, and are connected to individual circuit arrangements. The individual circuit arrangements are defined as systems. The intersystem communication circuit connects one of the systems to another of the systems. The internal power supply circuit is included in each of the systems. The internal power supply circuit supplies electric power to corresponding one of the controllers and the intersystem communication circuit. The protection circuit cuts off an internal power supply line between the internal power supply circuit and the intersystem communication circuit or limits supply of the electric power to the intersystem communication circuit, in response to the occurrence of an overvoltage abnormality in which an output voltage of the internal power supply circuit is in an overvoltage state.

The following describes multiple embodiments with reference to the drawings. Hereinafter, in the respective embodiments, substantially the same configurations are denoted by identical symbols, and repetitive description will be omitted.

First Embodiment

The first embodiment is shown inFIGS.1to8. An electronic control unit (ECU)10as a control unit according to the present embodiment is adapted to an electric power steering device8for assisting a steering operation of, for example, a vehicle.FIG.1shows a configuration of a steering system90including the electric power steering device8. The steering system90includes a steering wheel91as a steering member, a steering shaft92, a pinion gear96, a rack shaft97, wheels98, the electric power steering device8, and the like.

The steering wheel91is connected to the steering shaft92. A torque sensor94is provided on the steering shaft92to detect a steering torque. The torque sensor94has a first sensor unit194and a second sensor unit294, each of which is capable of detecting its own fault. A pinion gear96is provided at an axial end of the steering shaft92. The pinion gear96engages with the rack shaft97. A pair of road wheels98is coupled at both ends of the rack shaft97via, for example, tie rods.

When a driver of the vehicle rotates the steering wheel91, the steering shaft92connected to the steering wheel91rotates. A rotational motion of the steering shaft92is converted into a linear motion of the rack shaft97by the pinion gear96. The pair of road wheels98is steered to an angle corresponding to a displacement amount of the rack shaft97.

The electric power steering device8includes a driver40and the reduction gear89. The driver40includes a motor80, the ECU10, and the like. The reduction gear89as a power transmission unit reduces the rotation of the motor80and transmits it to the steering shaft92. In other words, the electric power steering device8according to the present embodiment is a so-called “column assist type”, but may be a so-called “rack assist type” which transmits the rotation of the motor80to the rack shaft97.

The motor80outputs a whole or a part of an assist torque required for a steering operation. As shown inFIG.2, the motor80is driven by electric power supplied from batteries190and290, each of which is a direct current power supply to rotate the reduction gear89in forward and reverse directions. The motor80is a three-phase brushless motor, but other motors may be used.

As shown inFIG.2, the motor80has two sets of motor windings (not shown). In the following, a configuration related to energization control of one motor winding may also be referred to as a first circuit unit100, and a configuration related to energization control of the other one motor winding may also be referred to as a second circuit unit200. Electronic components included in the first circuit unit100and the second circuit unit200mount on a board (not shown). All electronic components may mount on a single board. The single board may be divided into multiple boards, and the electronic components may mount on the multiple boards. The first circuit unit100may also be referred to as a first circuit arrangement, and the second circuit unit200may also be referred to as a second circuit arrangement.

In the present embodiment, since the circuit arrangement of the first circuit unit100and the circuit arrangement of the second circuit unit200are substantially identical, the following mainly describes the detailed circuit arrangement of the first circuit unit200. The combination of the first circuit unit100and the motor winding connected to the first circuit unit100is referred to as the first system, while the combination of the second circuit unit200and the motor winding connected to the second circuit unit200is referred to as the second system. In the present disclosure, the first system may be referred to as a local system or a self-system, and the second system may be referred to as an external system or an additional system. However, when the second system is referred to as a local system or a self-system, the first system is referred to as an external system or an additional system.

The first circuit unit100includes, for example, an inverter120, a motor relay123, an inverter driver circuit125, a current detector130, a rotation angle sensor135, a voltage detector136, a power supply relay141, a reverse-connection protection relay142, a relay driver circuit145, a communication driver circuit147, a microcomputer150, an integrated circuit151, an internal power supply circuit155, and a protection circuit160.

The first circuit unit100is supplied with electric power from the first battery190. In the first embodiment, the first battery190is, for example, a 48-volt power supply, and supplies electric power to the first circuit unit100via a PIG terminal191. The electric power of the first battery190is reduced to, for example,12volts by a reducer circuit193, and supplies the electric power to the first circuit unit100via an IG terminal192. The configuration related to boosting voltage or reducing voltage can be designed as appropriate, according to a voltage of the first battery190and a voltage required by the first circuit unit100.

The first circuit unit100is connected to a first sensor unit194of a torque sensor94via a torque sensor terminal195, and is connected to a vehicle communication network (not shown) via a communication terminal196. The vehicle communication network is connected to the microcomputer150via the communication driver circuit147so that various information can be transmitted and received. The present disclosure describes an example that the vehicle communication network is controller area network (CAN). However, any other standard such as CAN with Flexible Data rate (CAN-FD) or FlexRay may be adopted. The first circuit unit100is connected to a ground G1via a ground terminal198.

The second circuit unit200is supplied with electric power from a second battery290. In the present embodiment, the second battery290is, for example, a 48-volt power supply, and supplies electric power to the second circuit unit200via a PIG terminal291. The electric power of the second battery290is reduced to, for example, 12 volts by a reducer circuit293, and supplies the electric power to the second circuit unit200via an IG terminal292. The second circuit unit200is connected to a second sensor unit294of a torque sensor94via a torque sensor terminal295, and is connected to a vehicle communication network (not shown) via a communication terminal296. The vehicle communication network to which the first circuit unit100is connected and the vehicle communication network to which the second circuit unit200is connected may be identical or different. The second circuit unit100is connected to a ground G2via a ground terminal298. In the present embodiment, the ground G1of the first system and the ground G2of the second system are isolated.

The inverter120is a three-phase inverter that converts the electric power of the motor winding of the first system. The motor relay123is provided between the inverter120and the motor winding. The motor relay123can execute switchover between disconnection and connection of the inverter120and the motor winding. The inverter driver circuit125outputs a drive signal related to turning on or off the reverse-connection protection relay142and the switching elements (not shown) included in the inverter120and the motor relay123. The capacitor127is connected to the inverter120in parallel, and smoothens the electric power supplied to the inverter120by storing charge.

The current detector130is, for example, a shunt resistor provided in each phase, and detects the current flowing through each phase of the motor winding. The detection value is output to the microcomputer150via the integrated circuit151. InFIG.2, the integrated circuit151is indicated as “ASIC”. The rotation angle sensor135detects the rotation of the motor80, and outputs the detection value to the microcomputer150.

The voltage detector136detects a voltage of a power supply line Lp1connected to the PIG terminal191, and outputs the detection value to the microcomputer150. A choke coil137and a capacitor138included in a filter circuit are connected to the power supply line Lp1. The ground line Lg1is provided with a disconnection detector139that detects a disconnection of the ground.

The power supply relay141and the reverse-connection protection relay142are provided at the power supply line Lp1. In a case where the relays141,142are configured by a switching element such as a MOSFET having a parasitic diode, it may be desirable that two switching elements are connected in series so that the directions of the parasitic diodes are reversed. Thereby, even when the battery190is erroneously connected in the reverse direction, it is possible to prevent a reverse current from flowing. Further, the relays141and142may be mechanical relays. The relay driver circuit145outputs a drive signal related to turning on and off the power supply relay141.

The microcomputers150,250execute a variety types of calculation related to driving of the motor80, and are provided to send and receive information mutually. The electric power from the internal power supply circuit155is supplied to the microcomputer150. A capacitor156is connected to the internal power supply circuit155as illustrated inFIG.4. The capacitor156stabilizes the output voltage of the internal power supply circuit155.

If a fault occurs causing the output voltage (hereinafter referred to as “internal power supply voltage Vmi”) of the internal power supply circuit155supplying power to the microcontroller150and components related to intersystem communication to increase, there is a possibility that the fault may propagate by applying a voltage being in an overvoltage state to the external system that is normally functioning via the intersystem communication line Lc. As a countermeasure for the above situation, for example, an insulated communication buffer such as a photocoupler may be adopted for the intersystem communication. When the isolated communication buffer is a large device, it occupies a relatively large mounting area on the board.

In the present embodiment, the protection circuit160is provided for the internal power supply circuit155. The protection circuits160,260are illustrated inFIGS.3,4. InFIG.3, the interface circuits that connect different systems are collectively referred to as the intersystem communication circuits152and252. These circuits include the MCU-integrated SCI (Serial Communication Interface) and SPI (Serial Peripheral Interface), general-purpose port signals, monitoring signals from other ICs, transceivers for CAN and LIN, as well as branches from sensor interfaces. FromFIG.4onwards, the configuration in a single system is mainly described.

As shown inFIGS.3,4, the protection circuit160includes a fuse161and a Zener diode162. The fuse161is provided at the internal power supply line Li1that connects the internal power supply circuit155and the intersystem communication circuit152. The cathode of the Zener diode162is connected to the internal power supply line Li1, and the anode of the Zener diode162is connected to the ground G2being a ground in the external system via the diode163. The diode163is provided between the Zener diode162and the ground G2. The diode163is provided for preventing a current from flowing into the first system when the ground G2is floating.

The protection circuit260includes a fuse261and a Zener diode262. The fuse261is provided at the internal power supply line Li2that connects the internal power supply circuit255and the intersystem communication circuit252. The cathode of the Zener diode262is connected to the internal power supply line Li2, and the anode of the Zener diode262is connected to the ground G1being a ground in the external system via the diode263. The diode263is provided between the Zener diode262and the ground G1. The diode263is provided for preventing a current from flowing into the second system when the ground G1is floating.

In addition, as shown inFIG.5, when there are three or more systems and the grounds G1, G2, and G3in the individual systems are isolated, the Zener diodes162and the diode163are provided for each system and connected to the grounds G2and G3in the external systems, respectively. As shown inFIG.6, when the ground is common to each system, the diode163provided on the ground side of the Zener diode162can be omitted.

The following mainly describes the protection circuit160. When the internal power supply line Li1has a voltage being in the overvoltage state due to an abnormality in the internal power supply circuit155, the fuse161is melt down as a large current flows in a case where the voltage of the internal power supply line Li1becomes larger than the Zener voltage of the Zener diode162. Accordingly, it is possible to prevent a high voltage due to an abnormality in the internal power supply circuit155from being applied to the second system as the external system. In the present disclosure, the voltage being in the overvoltage state may be simply referred to as overvoltage.

The protection circuit160is constructed so that the fuse161is melt down before the Zener diode162has an open-circuit fault. In a case where If denotes a fusing current of the fuse161and Iz denotes the Zener disconnection current, the fuse161and the Zener diode162are constructed so that If is smaller than Iz.

Generally, when a bare chip of a Zener diode is subjected to an overload due to an overvoltage, a short circuit occurs between the cathode and anode of the Zener diode. At this time, when the current after the occurrence of the short circuit is large, the bonding may be cut and an open-circuit fault may occur. Accordingly, a metal clip connection structure, which is less likely to cause an open-circuit fault, may be adopted as the Zener diode162of the protection circuit160.

In the present embodiment, a board-mounted fuse such as a square chip current fuse or a mold-mounted current fuse is used as the fuse161. A chip resistor with low resistance (for example, several ohms) and low rated current may be used as the fuse161.

As illustrated inFIG.7, an integrated circuit (IC)55included in the internal power supply circuit155includes a die551, an output terminal552connected to the intersystem communication circuit152, and a bonding wire533connecting the die551and the output terminal552. The bonding wire553may have a function as the fuse by making the disconnection current of the bonding wire553to have be smaller than the disconnection current of the Zener diode162. In this case, the design is made so that dependent faults such as overheating and faults in other systems do not occur before the bonding wire553is melted down.

As shown inFIG.8, in the wiring pattern of the board included in the internal power supply line Li1, a fuse pattern Pf as a pattern being locally thinner than other locations may be formed as the fuse. In this case, it is necessary to design a board such that no other wiring provided at the regions above and below the layer where the fuse pattern Pf is formed. InFIG.8, locations where no pattern is formed are shown in satin finish.

In the present embodiment, the protection circuit160is constructed such that the fuse161and the Zener diode162are connected in series between the internal power supply circuit155and the ground G2of the external system. An overvoltage through the intersystem communication line Lc is prevented from being applied to the external system by melting down the fuse161in a case where an overvoltage of the internal power supply circuit155occurs. Therefore, when an overvoltage occurs in the internal power supply circuit155, it is possible to prevent a fault from propagating to the external system via the intersystem communication circuit152.

The ECU10includes the microcomputers150,250, the intersystem communication circuits152,252, the internal power supply circuits155,255, and the protection circuits160,260. The microcomputers150and250control driving of the motor80. The circuit arrangement corresponding to each of the microcomputers150,250is referred to as a system. The intersystem communication circuit152is connected to the external system that corresponds to the microcomputer250.

The internal power supply circuit155is provided for each system, and supplies the electric power to the microcomputer150and the intersystem communication circuit152. The protection circuit160may cut off the internal power supply line Li1leading to the intersystem communication circuit152from the internal power supply circuit155or limit the power supply to the intersystem communication circuit152, when the internal power supply voltage Vmi causes an overvoltage fault due to overvoltage. The internal power supply voltage Vmi is an output voltage of the internal power supply circuit155.

Thus, it is possible to prevent fault propagation to the external system due to overvoltage caused by abnormality in the internal power supply circuits155,255being applied to the external system via the intersystem communication circuits152,252.

When the ground in each system is isolated, the protection circuits160and260are connected to the ground of the external system. Thereby, it is possible to appropriately prevent overvoltage due to an abnormality in the internal power supply circuits155and255from being applied to the external system.

The protection circuit160according to the present embodiment includes the fuse161and the Zener diode162. The fuse161is provided at the internal power supply line Li1. The Zener diode162is provided at the wiring connected between the ground and the fuse161on the intersystem communication circuit152side. When the internal power supply voltage Vmi has the occurrence of overvoltage abnormality caused by overvoltage, it is possible to cut off the internal power supply line Li1by melting the fuse161. Thereby, it is possible to appropriately prevent overvoltage due to an abnormality in the internal power supply circuits155and255from being applied to the external system.

The fuses161,261are chip-like current fuses mounting on the board, or the chip resistors disconnected at a voltage being lower than the Zener diode. Therefore, the protection circuits160,260can be made with relatively small components.

The fuse161may be a bonding wire553connected to the output terminal552, which is connected to the intersystem communication circuit152, inside the IC55included in the internal power supply circuit155. Thus, the fuse161can be made without increasing the number of components.

The fuse161may serve as a fuse pattern Pf being locally formed thinner than other locations in the wiring pattern on the board included in the current path P connecting the internal power supply circuit155and the intersystem communication circuit152. Thus, the fuse161can be made without increasing the number of components.

Second Embodiment

A second embodiment is shown inFIG.9toFIG.11. The present embodiment is different from the embodiment described above in the protection circuit, and therefore, the following explanation mainly focuses on the first system. As shown inFIG.9, the protection circuit62includes switching elements621to623, a Zener diode624, and resistors625to627.

The switching elements621and622are P-channel MOSFETs, and are connected so that their sources are on the internal power supply circuit155side. The drain of the switching element621is connected to the intersystem communication circuit152side, and the gate of the switching element621is connected between the switching element622and the resistor625. The drain of the switching element622is connected to the ground G1via a resistor625, and the gate of the switching element622is connected to the drain of the switching element623.

The switching element623is an N-channel MOSFET. The source of the switching element623is connected to the ground G2being a ground in the external system. The drain of the switching element623is connected to the gate of the switching element622. The wiring, which connects the drain of the switching element623and the gate of the switching element622, is connected to the internal power supply line Li1via a resistor626. The gate of the switching element623is connected to the anode side of the Zener diode624. The cathode side of the Zener diode624is connected to the internal power supply line Li1, and the anode side of the Zener diode624is connected to the ground G2via a resistor627.

When the internal power supply circuit155is normal, no current flows to the Zener diode624. Therefore, a gate voltage is applied to the switching elements622and621via the resistor626, and the switching elements622and621are turned on. As a result, the electric power from the internal power supply circuit155is supplied to the intersystem communication circuit152via the switching element621.

When the internal power supply line Li1becomes overvoltage due to an abnormality in the internal power supply circuit155, the internal power supply voltage Vmi becomes higher than the Zener voltage of the Zener diode624. Thus, a gate voltage is applied to the switching element623via the Zener diode624, and the switching element623is turned on. When the current from the internal power supply line Li1flows to the switching element623side via the resistor626, the voltage applied to the gate of the switching element622decreases, and the switching elements622and621are turned off. As a result, it is possible to prevent the overvoltage of the internal power supply circuit155from being applied to the external system via the intersystem communication circuit152.

As shown inFIG.10, when there are three or more systems and the ground of each individual system is isolated, the switching element623, the Zener diode624, and the resistor627are provided for the individual system and connected to the ground of individual system. As shown inFIG.11, when multiple systems have a common ground, the source of the switching element623and the anode side of the Zener diode624are connected to the common ground.

The protection circuit62includes: the switching element621that is provided at the internal power supply line Li1; and the Zener diode624that is connected to the internal power supply line Li1and the ground. The switching element621is turned on when the internal power supply voltage Vmi is normal, and is turned off when the internal power supply voltage Vmi is an overvoltage because a current flows to the Zener diode624side. Thereby, when an overvoltage of the internal power supply voltage Vmi occurs, the internal power supply line Li1can be appropriately cut off. Further, the similar advantageous effects to those of the embodiment described above can also be achieved.

Third Embodiment

A third embodiment is shown inFIG.12toFIG.14. As shown inFIG.12, a protection circuit63includes an overvoltage detection circuit631, an overvoltage threshold generation circuit632, and a cutoff relay635. The internal power supply voltage Vmi is a voltage of the internal power supply line Li1. A comparative voltage Vref is a voltage generated in the overvoltage threshold generation circuit632. The overvoltage detection circuit631compares the internal power supply voltage Vmi with the comparative voltage Vref, and turns off the cutoff relay635in a case where the internal power supply voltage Vmi is larger than the comparative voltage Vref. Although the cutoff relay635in the present embodiment is a semiconductor relay, the cutoff relay635may be a mechanical relay.

The overvoltage threshold generation circuit632is a circuit that generates an overvoltage threshold based on the ground G2being a ground in the external system. The overvoltage threshold generation circuit632adopts, for example, a circuit provided with a Zener diode or a circuit for generating an arbitrary voltage by an amplifier for amplifying a bandgap voltage to generate a voltage value not exceeding the circuit breakdown voltage in the external system as the comparative voltage Vref.

As shown inFIG.13, when there are three or more systems and the ground in each individual system is isolated, the overvoltage threshold generation circuit632is provided for each system and is connected to the ground of each system. The diodes633are provided in the individual systems. By providing the diode633, the lowest value among the comparative voltages Vref generated by the overvoltage threshold generation circuits632in the individual systems is output to the overvoltage detection circuit631. This prevents circuit breakdown among the systems. As shown inFIG.14, the multiple systems have a common ground, the overvoltage threshold generation circuits632are connected to the common ground.

When the internal power supply voltage Vmi exceeds the comparative voltage Vref, the cutoff relay635is turned off. Therefore, even if the internal power supply line Li1becomes overvoltage, it is possible to prevent the high voltage exceeding the comparative voltage Vref from being applied to the external system via the intersystem communication circuit152.

The protection circuit63includes: the overvoltage detection circuit631that monitors the internal power supply voltage Vmi; and the cutoff relay635that is provided at the internal power supply line Li1and is turned off when an overvoltage of the internal power supply voltage Vmi is detected. Thereby, when an overvoltage of the internal power supply voltage Vmi occurs, the internal power supply line Li1can be appropriately cut off. Further, the similar advantageous effects to those of the embodiment described above can also be achieved.

Fourth Embodiment

A fourth embodiment is shown inFIG.15toFIG.18. As shown inFIG.15, a protection circuit64includes an overcurrent limiter circuit641and a Zener diode642. The overcurrent limiter circuit641detects the current of the output line using a current mirror circuit of an output element or a current detection element (for example, a Hall integrated circuit or a shunt resistor), and limits the output circuit. The overcurrent limiter circuit641may be built into the internal power supply circuit155as long as its independence is maintained.

The Zener diode642is provided between the overcurrent limiter circuit641and the ground G2being a ground in the external system. The Zener diode642is provided for preventing chain breakdown affecting the external system due to overvoltage.

The output current limit value Ilim of the overcurrent limiter circuit641is set to be greater than the maximum total current consumption Imax of the circuit that supplies power from the internal power supply circuit155, and also set to a value that does not cause open-circuit breakdown of the Zener diode642or overheating that affects the external system. By designing the overcurrent limiter circuit641to have an output limitation characteristic shown inFIG.16, it is possible to construct the protection circuit64using a relatively small-sized Zener diode642, which has a Fold-back Type Drooping Characteristic.

As shown inFIG.17, when there are three or more systems and the ground in each individual system is isolated, the Zener diode642is provided for each system and is connected to the ground of each system. As shown inFIG.18, when multiple systems have a common ground, the anode side of the Zener diode642is connected to the common ground.

The protection circuit64according to the present embodiment includes the overcurrent limiter circuit641provided at the output unit of the internal power supply circuit155, and can limit the power supply to the intersystem communication circuit152when an overvoltage abnormality occurs. Therefore, when the overvoltage of the internal power supply voltage Vmi occurs, it is possible to appropriately limit the voltage applied to the intersystem communication circuit152. Further, the similar advantageous effects to those of the embodiment described above can also be achieved.

In the present disclosure, the ECU10corresponds to a control unit; the motor80corresponds to a load; each of the microcomputers150,250corresponds to a controller; and an internal power supply voltage Vmi corresponds to an output voltage of an internal power supply circuit.

Other Embodiments

In the above embodiments, the number of systems is two or three. In other embodiments, the number of systems may be four or more. In the above embodiments, the load is the motor. In other embodiments, the load may be a generator, or may be a so-called motor generator having the functions of an electric motor and a generator, or may be other devices different from the motor. In the above embodiment, the control unit is applied to the electric power steering apparatus. In other embodiments, the control unit may be applied to other apparatuses different from the electric power steering apparatus.

The controller and the technique according to the present disclosure may be achieved by a dedicated computer provided by constituting a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the controller and the method described in the present disclosure may be realized by a dedicated computer configured as a processor with one or more dedicated hardware logic circuits. Alternatively, the controller and method described in the present disclosure may be realized by one or more dedicated computer, which is configured as a combination of a processor and a memory, which are programmed to perform one or more functions, and a processor which is configured with one or more hardware logic circuits. The computer programs may be stored, as instructions to be executed by a computer, in a tangible non-transitory computer-readable medium. The present disclosure is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the present disclosure.

The present disclosure has been made in accordance with the embodiments. However, the present disclosure is not limited to such embodiments and configurations. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combination and formation, and other combination and formation including one, more than one or less than one element may be made in the present disclosure.