Fault diagnosis device

Abstract

Diagnose faults in alternators using field effect transistors. [Solution] The fault diagnosis device includes an alternator and a control unit that diagnoses faults in the alternator. The alternator includes a power generation unit that generates AC voltage using power output from the engine and a rectifier that rectifies the AC voltage to DC voltage. The rectifier includes a field effect transistor and a diode connected in parallel to the field effect transistor. The control unit diagnoses faults based on the power generation efficiency of the alternator.

Description

[Technical Field]

[0001] The present invention relates to the technical field of fault diagnosis devices. [Background technology]

[0002] Conventionally, an alternator has been proposed in which a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is used in the rectifier (see, for example, Patent Document 1). Patent Document 1 describes detecting a short circuit in the MOSFET based on the voltages of various parts of the alternator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-87093 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, a diode is connected in parallel to the MOSFET used in the alternator to protect the MOSFET from a back electromotive force (surge). Therefore, even if an open circuit fault occurs in the MOSFET of the alternator, rectification by the diode is possible, and power generation continues. Therefore, the method described in Patent Document 1 has the problem of being unable to detect an open circuit fault in the MOSFET of the alternator.

[0005] The present invention has been made in view of the above circumstances, and has as its object to diagnose faults in an alternator that uses a field effect transistor. [Means for solving the problem]

[0006] A fault diagnosis device according to one embodiment of the present invention includes an alternator and a control unit that diagnoses faults in the alternator, the alternator including a power generation unit that generates AC voltage using power output from an engine and a rectifier that rectifies the AC voltage to DC voltage, the rectifier including a field effect transistor and a diode connected in parallel to the field effect transistor, and the control unit diagnoses faults based on the power generation efficiency of the alternator. [Effects of the Invention]

[0007] According to the present invention, it is possible to diagnose a fault in an alternator that uses a field effect transistor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a vehicle. [Figure 2] FIG. 2 is a diagram showing the configuration of an alternator. [Figure 3] 4 is a flowchart showing a flow of a fault diagnosis process performed by a controller. [Figure 4] FIG. 10 is a diagram showing a theoretical value map of power generation efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0009] <1. Vehicle configuration> Fig. 1 is a block diagram showing an example configuration of a vehicle 1. In Fig. 1, power transmission is indicated by a thick solid line, power flow is indicated by a thin solid line, and signal flow is indicated by a dashed line.

[0010] As shown in FIG. 1, a vehicle 1, which is an example of a failure diagnosis device, includes an engine 2, a transmission 3, wheels 4, an alternator 5, an auxiliary battery 6, auxiliary equipment 7, a controller 8, and a display 9.

[0011] The engine 2 is, for example, a horizontally opposed engine in which a pair of cylinder groups are arranged horizontally in the left-right direction with a crankshaft in between. The engine 2 reciprocates pistons using combustion pressure obtained by burning a mixture of gasoline and air in the cylinders. The engine 2 obtains power by rotating a crankshaft connected to the pistons via connecting rods. The engine 2 may be an in-line engine, a V-type engine, or the like. The engine 2 may also be a diesel engine.

[0012] The transmission 3 is connected to the crankshaft of the engine 2, and transmits power from the engine 2 at a variable speed to the wheels 4, thereby rotating the wheels 4 and causing the vehicle 1 to travel.

[0013] The alternator 5 is connected to the crankshaft of the engine 2 via an accessory belt. When power from the engine 2 is input via the accessory belt, the alternator 5 generates electricity using the power. The electric power generated by the alternator 5 is supplied to the accessory battery 6 and the accessories 7.

[0014] The auxiliary battery 6 is, for example, a 12V battery, and is charged by power supplied from the alternator 5. The auxiliary battery 6 is also connected to the auxiliary device 7, and supplies power to the auxiliary device 7.

[0015] The accessories 7 are in-vehicle devices that operate when supplied with power, such as headlights, an air conditioner, a car navigation system, etc. The controller 8 and the display 9 are also examples of the accessories 7. The auxiliary device 7 operates on power supplied directly from the alternator 5 or power supplied from the auxiliary device battery 6.

[0016] The controller 8 is, for example, an ECU (Electronic Control Unit), which is a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, and the like. The controller 8 loads a program stored in the ROM or nonvolatile memory into the RAM and executes the program to diagnose a fault in the alternator 5. The fault diagnosis process for the alternator 5 will be described later.

[0017] When the controller 8 detects a malfunction of the alternator 5, it turns on the indicator 9 to notify the driver that the alternator 5 has malfunctioned. The indicator 9 is, for example, a lamp in an instrument panel located in front of the driver. The indicator 9 is controlled by the controller 8 to be turned off when the alternator 5 is normal and to be turned on when the alternator 5 is abnormal.

[0018] 2 is a diagram showing the configuration of the alternator 5. As shown in FIG. 2, the alternator 5 includes a power generating unit 11, a rectifying unit 12, and a control circuit 13.

[0019] The power generating section 11 is configured to include two three-phase AC windings 21 and 22 and a field winding 23.

[0020] The three-phase AC winding 21 has three star-connected windings (e.g., X-phase winding 21a, Y-phase winding 21b, and Z-phase winding 21c) wound around a stator core (not shown). Similarly, the three-phase AC winding 22 has three star-connected windings (e.g., X-phase winding 22a, Y-phase winding 22b, and Z-phase winding 22c) wound around a stator core (not shown) at a position shifted by 30 electrical degrees from the three-phase AC winding 21.

[0021] Field winding 23 is wound around field poles (not shown) arranged opposite each other on the inner periphery of the stator core to form a rotor. The field poles are magnetized by passing an excitation current through field winding 23. The rotating magnetic field generated when the field poles are magnetized causes three-phase AC windings 21 and 22 to generate AC voltage.

[0022] The rectifying unit 12 is configured to include rectifiers 31 and 32. The rectifier 31 is connected to the three-phase AC winding 21, and rectifies the AC voltage generated by the three-phase AC winding 21 into a DC voltage.

[0023] The rectifier 31 is configured by connecting six MOSFETs 33a to 33f in a bridge configuration. Specifically, MOSFET 33a and MOSFET 33b are connected in series to form one arm. Similarly, MOSFET 33c and MOSFET 33d are connected in series to form one arm, and MOSFET 33e and MOSFET 33f are connected in series to form another arm. The rectifier 31 then forms a three-phase bridge by connecting three arms in parallel. Hereinafter, when the six MOSFETs 33a to 33f are described without distinction, they will be referred to as MOSFET 33.

[0024] The drains of the MOSFETs 33a, 33c, and 33e are commonly connected and grounded, while the sources of the MOSFETs 33b, 33d, and 33f are commonly connected and connected to the anode of the auxiliary battery 6. The cathode of the auxiliary battery 6 is grounded.

[0025] The gates of the MOSFETs 33 are connected to the control circuit 13. The MOSFETs 33 function as a switching element in which current flows between the drain and source when an on signal is input to the gate from the control circuit 13 (when a voltage is applied), and the drain and source are disconnected when an on signal is not input to the gate from the control circuit 13 (when a voltage is not applied).

[0026] Diodes 34a are connected in parallel to MOSFET 33a to protect MOSFET 33a from back electromotive force (surges). Similarly, diodes 34b to 34f are connected in parallel to MOSFETs 33b to 33f to protect MOSFETs 33b to 33f from back electromotive force (surges). In the following description, the six diodes 34a to 34f will be referred to as diodes 34 when no distinction is made between them.

[0027] The rectifier 32 is configured by connecting six MOSFETs 35a to 35f in a bridge configuration. Specifically, MOSFET 35a and MOSFET 35b are connected in series to form one arm. Similarly, MOSFET 35c and MOSFET 35d are connected in series to form one arm, and MOSFET 35e and MOSFET 35f are connected in series to form another arm. The rectifier 32 then forms a three-phase bridge by connecting three arms in parallel. Hereinafter, when the six MOSFETs 35a to 35f are described without distinction, they will be referred to as MOSFET 35.

[0028] The drains of the MOSFETs 35a, 35c, and 35e are commonly connected and grounded, and the sources of the MOSFETs 35b, 35d, and 35f are commonly connected and connected to the positive electrode of the auxiliary battery 6.

[0029] The gates of the MOSFETs 35 are connected to the control circuit 13. The MOSFETs 33 function as a switching element in which current flows between the drain and source when an on signal is input to the gate from the control circuit 13 (when a voltage is applied), and the drain and source are disconnected when an on signal is not input to the gate from the control circuit 13 (when no voltage is applied).

[0030] Diodes 36a to 36f are connected in parallel to the MOSFETs 35a to 35f, respectively, to protect the MOSFETs 35a to 35f from back electromotive voltages (surges). In the following description, the six diodes 36a to 36f will be referred to as diodes 36 when no distinction is made between them.

[0031] The control circuit 13 is connected to the gates of the MOSFETs 33 and 35. The control circuit 13 controls the operations of the rectifiers 31 and 32 by appropriately outputting ON signals to these gates. In this way, the control circuit 13 causes the rectifiers 31 and 32 to rectify the AC voltages generated in the three-phase AC windings 21 and 22 into DC voltages.

[0032] Furthermore, the control circuit 13 is connected to the field winding 23. The control circuit 13 controls the excitation current supplied to the field winding 23 to adjust the intensity of magnetization of the field poles.

[0033] The control circuit 13 measures the generated current and voltage generated when the power generation unit 11 generates power, and outputs these to the controller 8.

[0034] The alternator 5 is also provided with sensors for measuring the temperature, the number of rotations of the rotor, and the load torque, and the measured values ​​obtained by these sensors are output to the controller 8 via the control circuit 13.

[0035] Hereinafter, the generated current, generated voltage, temperature, rotation speed, and load torque of the alternator 5 may be collectively referred to as operating state information of the alternator 5.

[0036] The controller 8 is connected to the control circuit 13, and issues an operation request for the alternator 5 to the control circuit 13, and also acquires operating state information of the alternator 5. The controller 8 performs a fault diagnosis of the alternator 5 based on the acquired operating state information.

[0037] Fig. 3 is a flowchart showing the flow of the fault diagnosis process by the controller 8. As shown in Fig. 3, when the fault diagnosis process starts, the controller 8 acquires operating state information from the alternator 5 in step S1.

[0038] In step S2, the controller 8 determines whether there is any abnormality in the alternator 5. Here, it determines whether there is a drop in the generated voltage, an abnormality in communication with the alternator 5, or the like, for example.

[0039] If there is no abnormality in the alternator 5 (Yes in step S2), in step S3 the controller 8 determines whether the rotation speed of the alternator 5 is equal to or greater than the power generation speed. The power generation speed is the rotation speed at which the alternator 5 can generate electricity.

[0040] If the rotation speed of the alternator 5 is equal to or greater than the power generation speed (Yes in step S3), in step S4 the controller 8 calculates the power generation efficiency of the alternator 5. Specifically, the controller 8 calculates the input energy input to the alternator 5 and the output energy obtained by power generation by the alternator 5, and calculates the power generation efficiency by dividing the calculated output energy by the input energy.

[0041] The input energy is the kinetic energy input from the engine 2 to rotate the rotor of the alternator 5, and is calculated by the following equation (1). Input energy = load torque of alternator 5 × rotation speed of alternator 5 × π / 30 (1)

[0042] The output energy is the electrical energy obtained by the alternator 5 generating electricity, and is calculated by the following formula (2). Output energy = generated current of alternator 5 × generated voltage of alternator 5 (2)

[0043] The controller 8 calculates the input energy using equation (1) and calculates the output energy using equation (2). Then, the controller 8 calculates the power generation efficiency using equation (3) below. Power generation efficiency = output energy / input energy (3)

[0044] FIG. 4 is a diagram showing a theoretical value map of power generation efficiency. In step S5, the controller 8 calculates the theoretical value of power generation efficiency by referring to the theoretical value map of power generation efficiency shown in FIG. 4 based on the power generation current, power generation voltage, rotation speed, and temperature of the alternator 5 acquired in step S1.

[0045] The theoretical value is the power generation efficiency that is theoretically obtained when the alternator 5 operates at a predetermined power generation current, power generation voltage, rotation speed, and temperature.

[0046] The controller 8 has a theoretical value map of power generation efficiency stored in ROM as shown in Fig. 4. The theoretical value maps are provided for different temperatures, and the theoretical value maps for each different temperature are stored in the ROM.

[0047] As shown in Fig. 4, the theoretical value map shows the theoretical values ​​of power generation efficiency for each of the generated current, generated voltage, rotation speed, and temperature of the alternator 5. The generated voltage is controlled by the controller 8 to be constant (about 14 V in this case), and is shown in Fig. 4 as generated power (generated voltage x generated current).

[0048] The controller 8 calculates the theoretical value by interpolating the value obtained from the theoretical value map based on the generated current, generated voltage, rotation speed, and temperature of the alternator 5 acquired in step S1.

[0049] In step S6, the controller 8 compares the power generation efficiency calculated in step S4 with the theoretical value of the power generation efficiency calculated in step S5. Here, for example, it calculates whether the difference between the power generation efficiency calculated in step S5 and the theoretical value with respect to the power generation efficiency calculated in step S4 is equal to or less than a predetermined ratio (ratio to the theoretical value).

[0050] In step S7, the controller 8 determines whether the power generation efficiency of the alternator 5 has decreased based on the comparison result in step S7. Here, it determines whether the difference from the theoretical value is greater than a predetermined percentage.

[0051] If the power generation efficiency of the alternator 5 has not decreased (No in step S7), the controller 8 ends the failure diagnosis process.

[0052] On the other hand, if there is an abnormality in the alternator 5 (No in step S2), if the rotation speed of the alternator 5 is lower than the rotation speed at which power can be generated (No in step S3), or if the power generation efficiency has decreased (Yes in step S4), the controller 8 proceeds to step S8.

[0053] In step S8, the controller 8 turns on the indicator 9 indicating that the alternator 5 is abnormal, and ends the fault diagnosis process.

[0054] In this way, in vehicle 1, a fault is diagnosed based on the power generation efficiency of alternator 5. MOSFETs 33 and 35 are used in rectifiers 31 and 32 of alternator 5. Diodes 34 and 36 are connected in parallel to these MOSFETs 33 and 35, respectively. Therefore, even if MOSFETs 33 and 35 fail, current flows through diodes 34 and 36, reducing the power generation efficiency, but allowing power generation to continue.

[0055] Therefore, simply monitoring the generated current and generated voltage is not enough to determine whether an open circuit fault has occurred in the MOSFETs 33 and 35. On the other hand, if an open circuit fault occurs in the MOSFETs 33 and 35 and current flows through the diodes 34 and 36, causing power generation, the power generation efficiency will decrease. Therefore, in the vehicle 1, by diagnosing a failure based on the power generation efficiency of the alternator 5, it becomes possible to determine that the MOSFETs 33, 35 have an open failure, that is, that the alternator 5 has a failure.

[0056] <2. Modifications> Although the embodiments have been described above, the present invention is not limited to the specific examples described above and various configurations can be adopted.

[0057] For example, in the above embodiment, the controller 8 acquires the generated current, generated voltage, rotation speed, load torque, and temperature of the alternator 5 from the control circuit 13. However, the controller 8 may acquire one or more of these pieces of information directly.

[0058] In the above embodiment, the theoretical value of the power generation efficiency of the alternator 5 is calculated using a theoretical value map. However, the theoretical value of the power generation efficiency of the alternator 5 may be calculated by any other method as long as it can be calculated.

[0059] In the above embodiment, the power generation efficiency is calculated from the input energy and output energy of the alternator 5. However, the power generation efficiency of the alternator 5 may be calculated by any other method as long as it can be calculated.

[0060] <3. Summary of the embodiment> As described above, the fault diagnosis device (vehicle 1) of the embodiment includes an alternator 5 and a control unit (controller 8) that diagnoses a fault in the alternator 5. The alternator 5 includes a power generation unit 11 that generates an AC voltage using power output from the engine 2, and rectifiers 31 and 32 that rectify the AC voltage to a DC voltage. The rectifiers 31 and 32 include field effect transistors (MOSFETs 33 and 35) and diodes 34 and 36 connected in parallel to the field effect transistors. The control unit diagnoses a fault based on the power generation efficiency of the alternator 5. As a result, in vehicle 1, even when an open fault occurs in MOSFETs 33, 35 and current flows through diodes 34, 36, causing alternator 5 to generate power, it is possible to diagnose an open fault in MOSFETs 33, 35. That is, in vehicle 1, it is possible to diagnose a fault in alternator 5 using MOSFETs 33, 35.

[0061] The control unit (controller 8) calculates the power generation efficiency based on the input energy input to the alternator 5 and the output energy obtained by the alternator 5 generating electricity. As a result, the controller 8 calculates the power generation efficiency based on the actual input energy and output energy, and therefore the power generation efficiency can be calculated accurately and in real time.

[0062] The control unit (controller 8) compares the calculated power generation efficiency with the theoretical value of the power generation efficiency of the alternator 5, and determines that a failure has occurred if the difference between the calculated power generation efficiency and the theoretical value is greater than a predetermined percentage. This allows the controller 8 to accurately calculate the decrease in the power generation efficiency of the alternator 5.

[0063] The theoretical value is calculated based on the generated current, generated voltage, rotation speed, and temperature of the alternator 5. The controller 8 can accurately calculate the theoretical value of the power generation efficiency of the alternator 5 using the theoretical value map shown in FIG.

[0064] If the alternator 5 is abnormal, the control unit (controller 8) notifies the user via the display 9 that the alternator 5 is abnormal. When the controller 8 detects a failure in the alternator 5, it turns on the indicator 9, thereby allowing the driver to easily recognize that the alternator 5 has failed. [Explanation of symbols]

[0065] 1 vehicle 5 Alternator 8 Controller 11 Power Generation Department 31, 32 rectifier 33, 35 MOSFET 34, 36 Diodes

Claims

1. An alternator, a control unit that diagnoses a fault in the alternator, the alternator includes a power generating unit that generates AC voltage using power output from an engine, and a rectifier that rectifies the AC voltage to DC voltage; the rectifier comprises a field effect transistor and a diode connected in parallel to the field effect transistor; The control unit diagnoses a fault based on the power generation efficiency of the alternator. Fault diagnosis device.

2. The control unit calculates a power generation efficiency based on input energy input to the alternator and output energy obtained by power generation by the alternator. The fault diagnosis device according to claim 1 .

3. The control unit compares the calculated power generation efficiency with a theoretical value of the power generation efficiency of the alternator, and determines that a failure has occurred when the difference between the calculated power generation efficiency and the theoretical value is greater than a predetermined percentage. The fault diagnosis device according to claim 2 .

4. The theoretical value is calculated based on the generated current, generated voltage, rotation speed, and temperature of the alternator. The fault diagnosis device according to claim 3 .

5. When the alternator is abnormal, the control unit notifies the user that the alternator is abnormal via a display.

5. The fault diagnosis device according to claim 1.

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