Relay welding detection device

Abstract

To provide a relay welding determination device capable of determining relay welding without using a step-up converter.SOLUTION: A relay welding determination device is mounted on a vehicle which includes an internal combustion engine, a rotating electric machine capable of generating power using power from the internal combustion engine, an inverter for driving the rotating electric machine, a chargeable / dischargeable power storage device, a relay capable of connecting and releasing connection between the inverter and the power storage device, a capacitor connected in parallel between the inverter and the relay, and voltage detection means for detecting a voltage of the capacitor, generates power with the rotating electric machine using the power from the internal combustion engine, performs power control of varying a voltage of the capacitor, and determines presence / absence of welding of the relay.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a relay welding determination device. [Background technology]

[0002] Patent Document 1 discloses a hybrid vehicle that does not include a boost converter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-163529 Summary of the Invention [Problem to be solved by the invention]

[0004] In a vehicle that does not have a boost converter such as that disclosed in Patent Document 1, for example, it is not possible to use a boost converter to boost and fluctuate the voltage from the battery to charge a capacitor, and then determine whether a relay connected to the battery is welded based on the potential difference between the capacitor voltage and the battery voltage.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a relay welding determination device that can determine whether a relay is welded without using a boost converter. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the relay welding determination device of the present invention is mounted on a vehicle that includes an internal combustion engine, a rotating electric machine that can generate electricity using power from the internal combustion engine, an inverter that drives the rotating electric machine, a chargeable and dischargeable storage device, a relay that can connect and disconnect the inverter and the storage device, a capacitor connected in parallel between the inverter and the relay, and a voltage detection means that detects the voltage of the capacitor, and is characterized in that it generates electricity using power from the internal combustion engine at the rotating electric machine, performs power control to vary the voltage of the capacitor, and determines whether the relay is welded.

[0007] As a result, without using a boost converter, power from the internal combustion engine is used to generate electricity with the rotating electrical machine, and the capacitor voltage can be varied to determine whether the relay is welded.

[0008] Furthermore, in the above, after the connection is released by the relay, power from the internal combustion engine is used to generate electricity in the rotating electric machine, and power control is performed to vary the voltage of the capacitor in two stages, and if the absolute value of the difference between the voltage of the capacitor in the first stage of variation and the voltage of the capacitor in the second stage of variation is larger than a preset threshold value, it is determined that the relay is not welded, and if the absolute value is smaller than the threshold value, it is determined that the relay is welded.

[0009] As a result, even if the final value of the changed capacitor voltage becomes the same potential as the voltage of the power storage device, the capacitor voltage can be changed to determine whether the relay is welded. [Effects of the Invention]

[0010] The relay welding determination device according to the present invention has the advantage that it can determine whether the relay is welded by using power from an internal combustion engine to generate electricity with a rotating electric machine and fluctuating the capacitor voltage without using a boost converter. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a schematic overall configuration of a hybrid vehicle equipped with a relay welding determination device according to an embodiment. [Figure 2] FIG. 2 is a circuit block diagram for explaining the configuration of the vehicle's electrical system. [Figure 3] FIG. 3 is a diagram showing an example of how system voltage VH is varied in determining whether a relay is welded. [Figure 4] FIG. 4 is a flowchart showing an example of control of relay welding determination performed by the ECU in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of a relay welding determination device according to the present invention will be described below. However, the present invention is not limited to this embodiment. The relay welding determination device according to the present invention is mounted on, for example, a hybrid vehicle in which a rotating electric machine generates electricity using driving force from an internal combustion engine.

[0013] 1 is a block diagram showing a schematic overall configuration of a hybrid vehicle 1 equipped with a relay welding determination device according to an embodiment. The hybrid vehicle 1 includes an engine 100, a first motor generator 10 (hereinafter sometimes referred to as MG1) serving as a first rotating electric machine, a second motor generator 20 (hereinafter sometimes referred to as MG2) serving as a second rotating electric machine, a planetary gear mechanism 30, drive wheels 50, an output shaft 60 connected to the drive wheels 50, a wheel speed sensor 73, a battery 150, a system main relay (SMR) 160, a charging relay 170, a charging device 172, an inlet 174, a power control unit (PCU) 200, and an electronic control unit (ECU) 300. In this embodiment, the ECU 300 functions as a relay welding determination device equipped in the hybrid vehicle 1 to determine whether the SMR 160 is welded.

[0014] The hybrid vehicle 1 runs using the power of at least one of the engine 100 and the second motor generator 20. During normal running, the hybrid vehicle 1 can switch its running mode between electric vehicle running (hereinafter referred to as "EV running"), in which it runs (runs electrically) using the power of the second motor generator 20 without using the power of the engine 100 (i.e., with the engine 100 stopped), and hybrid vehicle running (hereinafter referred to as "VH running"), in which it runs using the power of both the engine 100 and the second motor generator 20.

[0015] The engine 100 is an internal combustion engine such as a gasoline engine or a diesel engine. The engine 100 generates power for running the hybrid vehicle 1 in response to a control signal from the ECU 300. The power generated by the engine 100 is output to the planetary gear mechanism 30.

[0016] Engine 100 is provided with an engine rotation speed sensor 410. Engine rotation speed sensor 410 detects the rotation speed (engine rotation speed) Ne of crankshaft 110 of engine 100, and outputs a signal indicating the detection result to ECU 300.

[0017] Each of the first motor generator 10 and the second motor generator 20 is a three-phase AC permanent magnet synchronous motor. When starting the engine 100, the first motor generator 10 rotates the crankshaft 110 of the engine 100 using power from the battery 150. The first motor generator 10 can also generate power using power from the engine 100. The AC power generated by the first motor generator 10 is converted to DC power by the PCU 200 and charged into the battery 150. The AC power generated by the first motor generator 10 may also be supplied to the second motor generator 20.

[0018] The rotor of the second motor generator 20 is connected to an output shaft 60. The second motor generator 20 rotates the output shaft 60 using electric power supplied from at least one of the battery 150 and the first motor generator 10. The second motor generator 20 is also capable of generating electric power through regenerative braking. The AC electric power generated by the second motor generator 20 is converted to DC electric power by the PCU 200 and charged into the battery 150.

[0019] The output shaft 60 is connected to the left and right drive wheels 50 via a differential gear. The drive wheels 50 are provided with wheel speed sensors 73. The wheel speed sensors 73 detect the rotational speeds of the drive wheels 50 as wheel speeds VS and output signals indicating the detection results to the ECU 300. The wheel speed sensors 73 can detect the magnitude (absolute value) of the rotational speeds of the drive wheels 50, but cannot detect the rotational direction of the drive wheels 50. In other words, the ECU 300 can determine the magnitude (absolute value) of the rotational speeds of the drive wheels 50 from the output value of the wheel speed sensor 73, but cannot determine the rotational direction of the drive wheels 50. Note that while one wheel speed sensor 73 is shown in FIG. 1 , the number of wheel speed sensors 73 is not limited to one. For example, a wheel speed sensor 73 may be provided for each of the four wheels (the left and right drive wheels 50 and the left and right driven wheels (not shown)) of the hybrid vehicle 1.

[0020] Planetary gear mechanism 30 mechanically couples engine 100, first motor generator 10, and output shaft 60, and is configured to transmit torque between engine 100, first motor generator 10, and output shaft 60. Specifically, planetary gear mechanism 30 includes, as rotating elements, a sun gear S coupled to the rotor of first motor generator 10, a ring gear R coupled to output shaft 60, a carrier CA coupled to crankshaft 110 of engine 100, and a pinion gear P meshing with sun gear S and ring gear R. Carrier CA holds pinion gear P so that pinion gear P can rotate and revolve about its axis.

[0021] With the planetary gear mechanism 30 configured as described above, the rotational speed of the sun gear S (= MG1 rotational speed Nm1), the rotational speed of the carrier CA (= engine rotational speed Ne), and the rotational speed of the ring gear R (= MG2 rotational speed Nm2) are connected by a straight line on a collinear diagram (a relationship in which the rotational speed of the remaining one is determined when any two of the rotational speeds are determined; hereinafter, this relationship may also be referred to as the "collinear diagram relationship"). Note that, because the ring gear R is connected to the drive wheels 50 via the output shaft 60, the magnitude (absolute value) of the rotational speed of the ring gear R (= MG2 rotational speed Nm2) is proportional to the magnitude (absolute value) of the wheel speed VS.

[0022] The battery 150 is a rechargeable lithium ion secondary battery, but may be another secondary battery such as a nickel-metal hydride secondary battery.

[0023] SMR 160 is connected in series to a power line between battery 150 and PCU 200. SMR 160 switches between a conductive state and a cut-off state between battery 150 and PCU 200 in response to a control signal from ECU 300.

[0024] The PCU 200 converts the DC power stored in the battery 150 into AC voltage and supplies it to the first motor generator 10 and the second motor generator 20. The PCU 200 also converts the AC power generated by the first motor generator 10 and the second motor generator 20 into DC power and supplies it to the battery 150.

[0025] The ECU 300 includes a CPU (Central Processing Unit), memory, input / output buffers, and the like, all of which are not shown. Based on signals from various sensors and devices, as well as maps and programs stored in the memory, the ECU 300 controls the output (fuel injection, ignition timing, valve timing, etc.) of the engine 100 and the output (amount of current) of the first motor generator 10 and the second motor generator 20 so that the hybrid vehicle 1 operates in a desired driving state. Note that the various controls are not limited to being processed by software, and can also be processed by dedicated hardware (electronic circuits).

[0026] 2 is a circuit block diagram for explaining the configuration of the electrical system of hybrid vehicle 1. The electrical system of hybrid vehicle 1 includes battery 150, SMR 160, PCU 200, first motor generator 10, second motor generator 20, and ECU 300. PCU 200 includes capacitor C1, first inverter 221, second inverter 222, and voltage sensor 230.

[0027] The battery 150 is provided with a monitoring unit 440. The monitoring unit 440 detects the voltage (battery voltage) VB of the battery 150, the current (battery current) IB supplied to the battery 150, and the temperature (battery temperature) TB of the battery 150, and outputs signals indicating the detection results to the ECU 300.

[0028] The capacitor C1 is connected in parallel between the first inverter 211 and the second inverter 222 and the SMR 160, and smoothes the battery voltage VB before supplying it to the first inverter 211 and the second inverter 222.

[0029] Voltage sensor 230 detects system voltage VH, which is the voltage across capacitor C1, and outputs a signal indicating the detection result to ECU 300.

[0030] When system voltage VH is supplied, first inverter 221 converts the DC voltage into AC voltage in response to a control signal from ECU 300 to drive first motor generator 10. First inverter 221 includes a U-phase arm 1U, a V-phase arm 1V, and a W-phase arm 1W. The phase arms are connected in parallel between power lines PL and NL. U-phase arm 1U has switching elements Q3 and Q4 connected in series. V-phase arm 1V has switching elements Q5 and Q6 connected in series. W-phase arm 1W has switching elements Q7 and Q8 connected in series. Diodes D3 to D8 are connected in anti-parallel between the collector and emitter of each of switching elements Q3 to Q8.

[0031] When system voltage VH is supplied to second inverter 222, second inverter 222 converts the DC voltage into AC voltage in response to a control signal from ECU 300 to drive second motor generator 20. Second inverter 222 includes phase arms 2U to 2W, switching elements Q9 to Q14, and diodes D9 to D14. Note that the configuration of second inverter 222 is basically the same as the configuration of first inverter 221, and therefore detailed description thereof will be omitted.

[0032] The first motor generator 10 is provided with a resolver 421. The resolver 421 detects the rotation speed (MG1 rotation speed Nm1) of the first motor generator 10 and outputs a signal indicating the detection result to the ECU 300. The resolver 421 can detect the magnitude (absolute value) and rotation direction of the rotation speed. That is, the ECU 300 can determine not only the magnitude (absolute value) of the rotation speed of the first motor generator 10 but also the rotation direction from the output value of the resolver 421.

[0033] The second motor generator 20 is provided with a resolver 422. The resolver 422 detects the rotation speed (MG2 rotation speed Nm2) of the second motor generator 20 and outputs a signal indicating the detection result to the ECU 300. Similar to the resolver 421, the resolver 422 can detect the magnitude (absolute value) and rotation direction of the rotation speed. That is, the ECU 300 can determine not only the magnitude (absolute value) of the rotation speed of the second motor generator 20 but also the rotation direction from the output value of the resolver 422.

[0034] Furthermore, the first motor generator 10 and the second motor generator 20 are provided with current sensors 241, 242, respectively. The current sensor 241 detects a motor current IM1 that is a current flowing through the first motor generator 10. The current sensor 242 detects a motor current IM2 that is a current flowing through the second motor generator 20. These sensors each output a signal indicating the detection result to the ECU 300.

[0035] Based on information from each sensor, the ECU 300 controls the PCU 200 (the first inverter 221 and the second inverter 222) so that the outputs of the first motor generator 10 and the second motor generator 20 become desired outputs. In the example shown in Fig. 2, the ECU 300 is configured as one unit, but the ECU 300 may be divided into multiple units.

[0036] Next, an example of relay welding determination performed in the hybrid vehicle 1 according to this embodiment will be described. In this embodiment, when determining whether the SMR 160 is welded, the first motor generator 10 is driven using power from the engine 100 to generate electricity, and the system voltage VH is varied to determine whether the SMR 160 is welded. For example, when a battery failure requires that the SMR 160 be shut off, the SMR is checked for shutoff by controlling the power generated by the engine 100 to drive the first motor generator 10 to generate electricity, thereby varying the system voltage VH (the input voltage of the second inverter 222) and creating a potential difference with the battery voltage VB. During this time, to prevent the second motor generator 20 from affecting the system voltage VH, the gate of the second inverter 222 is shut off to reduce power consumption when the second motor generator 20 is not generating back electromotive force (MG2 back electromotive force) at low vehicle speeds. On the other hand, if a back electromotive force (MG2 back electromotive voltage) is generated in the second motor generator 20 at high vehicle speeds, a torque of 0 [Nm] is commanded (power is consumed on the d-axis where no torque is generated on the dq-axis). In this way, disturbances caused by the second motor generator 20 to the system voltage VH when determining whether the SMR 160 is welded are suppressed.

[0037] Fig. 3 is a diagram showing an example of how system voltage VH is varied in determining whether a relay is welded. The initial value VH1 of system voltage VH shown in Fig. 3 varies depending on the remaining charge of battery 150 because, when first motor generator 10 is not generating power and SMR 160 is in a conductive state, capacitor C1 is charged with power from battery 150, and battery voltage VB and system voltage VH have the same potential. Furthermore, by driving first motor generator 10 to generate power using power from engine 100, capacitor C1 is also charged with power according to the amount of power generated. Therefore, system voltage VH can be varied depending on the power from battery 150 and the power generated by first motor generator 10.

[0038] When varying the system voltage VH, the final value of the varied system voltage VH is set to the median value of the inverter operation guaranteed voltage range as the target value V1 to prevent control failure. If the target value V1 and the battery voltage VB were at the same potential, the system voltage VH could not be varied. Therefore, in the relay welding determination performed in this embodiment, the system voltage VH is varied in two stages depending on the elapsed time since the SMR was disconnected, and the target value V1 is set in the second stage of the variation. When varying the system voltage VH in two stages, the target value of the system voltage VH in the first stage is selected as the efficient target value V2 or V3, which does not cause excessive voltage fluctuation, depending on the magnitude relationship between the initial value VH1 of the system voltage VH and the target value V1. That is, if the initial value VH1 of the system voltage VH is equal to or greater than the target value V1, the target value of the system voltage VH in the first stage is selected as the target value V2, which is higher in potential than the target value V1. On the other hand, when the initial value VH1 of the system voltage VH is less than the target value V1, the target value of the system voltage VH in the first stage is set to a target value V3 that is lower than the target value V1.

[0039] Then, when the SMR disconnection elapsed time is in the range of 0 to time A, power control is performed by generating power from first motor generator 10 so that target system voltage VH* becomes target value V2 or target value V3 in the first stage of fluctuation, and actual system voltage VH2 detected by voltage sensor 230 is latched. Thereafter, when the SMR disconnection elapsed time is in the range of time A to time B, power control is performed by generating power from first motor generator 10 so that target system voltage VH* becomes target value V1 in the second stage of fluctuation, and actual system voltage VH3 detected by voltage sensor 230 is latched. Then, when the SMR disconnection elapsed time is equal to or greater than time B, the presence or absence of welding of SMR 160 is determined from the absolute value of the difference (potential difference) between actual system voltage VH3 and actual system voltage VH2.

[0040] Specifically, when the initial value VH1 of the system voltage VH is equal to or greater than the target value V1, the difference (potential difference) between the target value V2 and the target value V1 is set as a threshold value VC, and it is determined whether the absolute value of the difference (potential difference) between the actual system voltage VH3 and the actual system voltage VH2 is equal to or greater than the threshold value VC. If it is determined that the absolute value is equal to or greater than the threshold value VC, it is determined that the SMR 160 is not welded. On the other hand, if it is determined that the absolute value is less than the threshold value VC, it is determined that the SMR 160 is welded.

[0041] Furthermore, when the initial value VH1 of the system voltage VH is less than the target value V1, the difference (potential difference) between the target value V1 and the target value V3 is set as a threshold value VC, and it is determined whether the absolute value of the difference (potential difference) between the actual system voltage VH3 and the actual system voltage VH2 is equal to or greater than the threshold value VC. If it is determined that the absolute value is equal to or greater than the threshold value VC, it is determined that the SMR 160 is not welded. On the other hand, if it is determined that the absolute value is less than the threshold value VC, it is determined that the SMR 160 is welded.

[0042] FIG. 4 is a flowchart showing an example of control of relay welding determination performed by ECU 300 in this embodiment. First, in step S1, ECU 300 performs preparations for SMR disconnection. For example, engine 100 is started so that first motor generator 10 can generate power at any timing and change system voltage VH. Next, in step S2, ECU 300 determines whether the relationship MG2 back electromotive force ≥ battery voltage VB is satisfied. If ECU 300 determines that the relationship MG2 back electromotive force ≥ battery voltage VB is satisfied (Yes in step S2), ECU 300 permits the gate of second inverter 222 to be opened and outputs a 0 [Nm] command in step S3, and proceeds to step S5. On the other hand, if ECU 300 determines that the relationship MG2 back electromotive force ≥ battery voltage VB is not satisfied (No in step S2), ECU 300 shuts off the gate of second inverter 222 in step S4, and proceeds to step S5.

[0043] Next, in step S5, ECU 300 detects and latches initial value VH1 of system voltage VH before SMR shutoff using voltage sensor 230. Next, in step S6, ECU 300 performs SMR shutoff processing. Next, in step S7, ECU 300 determines whether the relationship of initial value VH1 of system voltage VH≧target value V1 is satisfied. If ECU 300 determines that the relationship of initial value VH1 of system voltage VH≧target value V1 is satisfied (Yes in step S7), in step S8, ECU 300 adjusts the amount of power generated by first motor generator 10 to vary system voltage VH so that target system voltage VH*=target value V2, and proceeds to step S10. On the other hand, if the ECU 300 determines that the relationship of the initial value VH1 of the system voltage VH≧the target value V1 is not satisfied (No in step S7), then in step S9, the ECU 300 adjusts the amount of power generated by the first motor generator 10 using power from the engine 100 to vary the system voltage VH so that the target system voltage VH*=the target value V3, and then proceeds to step S10.

[0044] Next, in step S10, ECU 300 detects and latches actual system voltage VH2 when SMR cutoff elapsed time<time A using voltage sensor 230. Next, in step S11, ECU 300 determines whether the relationship time A≦SMR cutoff elapsed time<time B is satisfied. If ECU 300 determines that time A≦SMR cutoff elapsed time<time B is not satisfied (No in step S11), it repeats the processing of step S11 until the relationship time A≦SMR cutoff elapsed time<time B is satisfied. On the other hand, if ECU 300 determines that the relationship time A≦SMR cutoff elapsed time<time B is satisfied (Yes in step S11), ECU 300 varies system voltage VH by adjusting the amount of power generated by first motor generator 10 using power from engine 100 so that target system voltage VH*=target value V1 is satisfied (step S12). Next, in step S13, ECU 300 causes voltage sensor 230 to detect and latch actual system voltage VH3 at time A≦SMR cutoff elapsed time<time B.

[0045] Next, in step S14, ECU 300 determines whether the relationship SMR cutoff elapsed time ≧ time B is satisfied. If ECU 300 determines that the relationship SMR cutoff elapsed time ≧ time B is not satisfied (No in step S14), it repeats the processing of step S14 until the relationship SMR cutoff elapsed time ≧ time B is satisfied. On the other hand, if ECU 300 determines that the relationship SMR cutoff elapsed time ≧ time B is satisfied (Yes in step S14), it determines in step S15 whether the relationship | actual system voltage VH3 − actual system voltage VH2 | ≧ threshold value VC is satisfied. If ECU 300 determines that the relationship | actual system voltage VH3 − actual system voltage VH2 | ≧ threshold value VC is satisfied (Yes in step S15), it determines in step S16 that SMR 160 is not welded, and ends the series of control operations. On the other hand, if ECU 300 determines that the relationship |actual system voltage VH3-actual system voltage VH2|≧threshold value VC is not satisfied (No in step S15), ECU 300 determines in step S17 that SMR 160 is welded, and ends the series of controls.

[0046] As described above, in the relay welding determination device according to the embodiment, without using a boost converter to boost the battery voltage VB, power is generated by the first motor generator 10 using power from the engine 100, and the system voltage VH is varied to determine whether the SMR 160 is welded. [Explanation of symbols]

[0047] 1 Hybrid vehicle 10. First motor generator 20 Second motor generator 30 Planetary gear mechanism 50 drive wheels 60 output shaft 73 Wheel speed sensor 100 Engine 110 crankshaft 150 Battery 160 SMR 200 PCU 221 First inverter 222 Second inverter 230 Voltage Sensor 241,242 Current Sensor 300 ECU 410 Engine speed sensor 421,422 resolver 440 Monitoring Unit

Claims

[Claim 1] an internal combustion engine; a rotating electric machine capable of generating electricity using power from the internal combustion engine; an inverter that drives the rotating electric machine; a chargeable and dischargeable electricity storage device; a relay capable of connecting and disconnecting the inverter and the power storage device; a capacitor connected in parallel between the inverter and the relay; a voltage detection means for detecting a system voltage, which is a voltage across the capacitor; It is installed in a vehicle equipped with a relay welding determination device that, after the connection is released by the relay, generates power in the rotating electric machine using power from the internal combustion engine, performs power control to vary the system voltage in two stages, and determines that the relay is not welded if an absolute value of a difference between the system voltage in the first stage of variation and the system voltage in the second stage of variation is larger than a preset threshold value, and determines that the relay is welded if the absolute value is smaller than the threshold value, If the initial value of the system voltage is less than a first target value, a second target value lower in potential than the first target value is set as the target value of the system voltage in the first stage, and the capacitor is charged with power corresponding to the amount of power generated by the rotating electric machine; and the first target value is set as the target value of the system voltage in the second stage, and the capacitor is charged with power corresponding to the amount of power generated by the rotating electric machine. A relay welding determination device characterized by:

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