JP2012228902A - Vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce shock generated due to torque of a motor generator defined by feedback control of an engine rotation speed NE.SOLUTION: An engine and a motor generator connected to an output shaft of the engine are mounted on a vehicle. Torque of the motor generator is controlled in accordance with a difference between an actual output shaft rotation speed of the engine and a target rotation speed. When the target rotation speed changes, the change rate of the change amount of the target rotation speed is limited so as to be equal to or less than a predetermined upper limit value.

Description

  The present invention relates to a vehicle control device, and more particularly to a vehicle control device in which an engine and an electric motor connected to an output shaft of the engine are mounted.

  In addition to the engine, a hybrid vehicle equipped with an electric motor for traveling is known. Hybrid vehicles may be classified as a form of electric vehicle. Some hybrid vehicles are equipped with a generator for storing electric power supplied to the electric motor. In a hybrid vehicle equipped with a generator, the engine speed can be controlled using the generator in a certain operating state, as described in paragraph 44 of Japanese Patent Laid-Open No. 2001-304022.

Japanese Patent Laid-Open No. 2001-304002

  However, if for some reason, the torque that the generator gives to the engine to control the engine speed increases transiently, a large shock may occur due to the torque of the generator.

  The present invention has been made to solve the above-described problems, and an object thereof is to reduce shock.

  In one embodiment, a control device for a vehicle on which an engine and an electric motor coupled to an output shaft of the engine are mounted is configured so that a difference between the actual output shaft rotational speed of the engine and the target rotational speed depends on the difference between the engine rotational speed and the target rotational speed. A control means for controlling the torque of the electric motor connected to the output shaft, and a limiting means for limiting the rate of change of the change amount of the target rotational speed to a predetermined upper limit value or less when the target rotational speed changes. Is provided.

  According to this configuration, the change rate of the change amount of the target rotation speed is limited to a predetermined upper limit value or less, so that the change amount of the target rotation speed can be prevented from increasing rapidly, and a sudden change in the target rotation speed can be suppressed. Therefore, it is possible to suppress a sudden increase in the difference between the actual output shaft speed of the engine and the target speed. As a result, the torque of the electric motor connected to the output shaft of the engine, which is determined based on the difference between the actual output shaft speed of the engine and the target rotational speed, is prevented from changing suddenly. The shock that may occur can be reduced.

In another embodiment, the limiting means increases the upper limit over time.
According to this configuration, by increasing the upper limit value as time elapses, the target rotational speed can be changed to a desired value while suppressing a sudden change in the target rotational speed immediately after the target rotational speed is changed.

  In yet another embodiment, the limiting means limits the rate of change in the amount of change in the target rotational speed to an upper limit value or less when the target rotational speed decreases.

  In yet another embodiment, the limiting means limits the rate of change in the amount of change in the target rotational speed to an upper limit value or less when the accelerator opening decreases to zero and the target rotational speed decreases.

  In yet another embodiment, the limiting means limits the change rate of the amount of change in the target rotational speed to an upper limit value or less when a shift operation is performed and the target rotational speed decreases.

  In yet another embodiment, the limiting means limits the rate of change in the amount of change in the target rotational speed to an upper limit value or less when the target rotational speed decreases while the engine is operating under load.

  In yet another embodiment, the limiting means limits the rate of change of the change amount of the target rotational speed to an upper limit value or less when the target rotational speed decreases while the engine is idling.

  In yet another embodiment, the limiting means limits the change rate of the amount of change in the target rotational speed to the upper limit value or less when the target rotational speed decreases while the engine is motored by the electric motor.

  According to these configurations, the target rotational speed decreases due to, for example, changes in the engine operating conditions, and as a result, the torque applied to the engine from the electric motor to reduce the engine output shaft rotational speed increases. In such a case, a sudden increase in the torque of the electric motor can be suppressed.

It is a schematic block diagram which shows a hybrid vehicle. It is a figure which shows the electric system of a hybrid vehicle. It is a figure which shows the period which an engine drives, and the period which stops. It is a flowchart which shows the process which ECU performs. It is a figure which shows engine rotational speed NE, target rotational speed TNE, and the torque of a 1st motor generator. It is a figure which shows the change rate of the amount of change of the target rotation speed TNE and the amount of change of the target rotation speed TNE before and after limiting the change rate of the change amount of the target rotation speed TNE. It is a figure which shows the target rotational speed TNE before and after restrict | limiting the change rate of the variation | change_quantity of the target rotational speed TNE. It is a figure which shows the change rate of the engine rotation speed NE, the target rotation speed TNE, the torque of the first motor generator, and the change amount of the target rotation speed TNE after the change rate of the change amount of the target rotation speed TNE is before limiting. . It is a figure which shows the variation | change_quantity of target rotation speed TNE.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 1, engine 100, first motor generator 110, second motor generator 120, power split mechanism 130, reduction gear 140, and battery 150 are mounted on the hybrid vehicle. In the following description, a hybrid vehicle not having a charging function from an external power source will be described as an example, but a plug-in hybrid vehicle having a charging function from an external power source may be used.

  Engine 100, first motor generator 110, second motor generator 120, and battery 150 are controlled by an ECU (Electronic Control Unit) 170. ECU 170 may be divided into a plurality of ECUs.

  This vehicle travels by driving force from at least one of engine 100 and second motor generator 120. That is, either one or both of engine 100 and second motor generator 120 is automatically selected as a drive source according to the operating state.

  For example, engine 100 and second motor generator 120 are controlled in accordance with the result of the driver operating accelerator pedal 172 and shift lever 174. The operation amount (accelerator opening) of the accelerator pedal 172 is detected by an accelerator opening sensor (not shown) and input to the ECU 170. The position of shift lever 174 is detected by a position sensor (not shown) and input to ECU 170.

  When the accelerator opening is small and the vehicle speed is low, the hybrid vehicle runs using only the second motor generator 120 as a drive source. In this case, engine 100 is stopped. However, the engine 100 may be driven for power generation or the like.

  Further, when the accelerator opening is large, the vehicle speed is high, or the remaining capacity (SOC: State Of Charge) of battery 150 is small, engine 100 is driven. In this case, the hybrid vehicle runs using only engine 100 or both engine 100 and second motor generator 120 as drive sources.

  The engine 100 is an internal combustion engine. As the fuel / air mixture burns in the combustion chamber, the crankshaft as the output shaft rotates. The exhaust gas discharged from the engine 100 is purified by the catalyst 102 and then discharged outside the vehicle. The catalyst 102 exhibits a purification action by being warmed up to a specific temperature. The catalyst 102 is warmed up by utilizing the heat of the exhaust gas. The catalyst 102 is, for example, a three-way catalyst.

  The actual output shaft rotational speed of engine 100 (hereinafter also referred to as engine rotational speed NE) is detected by rotational speed sensor 104. A signal representing the detected rotational speed NE is input to ECU 170.

  Engine 100, first motor generator 110, and second motor generator 120 are connected via power split mechanism 130. The power generated by the engine 100 is divided into two paths by the power split mechanism 130. One is a path for driving the front wheels 160 via the speed reducer 140. The other is a path for driving the first motor generator 110 to generate power.

  First motor generator 110 is connected to the output shaft of engine 100 via power split mechanism 130. First motor generator 110 is a three-phase AC rotating electric machine including a U-phase coil, a V-phase coil, and a W-phase coil. First motor generator 110 generates power using the power of engine 100 divided by power split mechanism 130. The electric power generated by the first motor generator 110 is selectively used according to the running state of the vehicle and the remaining capacity of the battery 150. For example, during normal traveling, the electric power generated by first motor generator 110 becomes electric power for driving second motor generator 120 as it is. On the other hand, when the SOC of battery 150 is lower than a predetermined value, the electric power generated by first motor generator 110 is converted from AC to DC by an inverter described later. Thereafter, the voltage is adjusted by a converter described later and stored in the battery 150.

  When first motor generator 110 is acting as a generator, first motor generator 110 generates negative torque. Here, the negative torque means a torque that becomes a load on engine 100. When first motor generator 110 is supplied with electric power and acts as a motor, first motor generator 110 generates positive torque. Here, the positive torque means a torque that does not become a load on the engine 100, that is, a torque that assists the rotation of the engine 100. The same applies to the second motor generator 120.

  In the present embodiment, the engine speed NE is controlled by controlling the torque of the first motor generator 110 by feedback control based on the difference between the engine speed NE and the target speed TNE in a predetermined operating state. The For example, in order to make the engine speed NE coincide with the target speed TNE, at least one of proportional control using the difference between the engine speed NE and the target speed TNE, integral control, and differential control, The torque of first motor generator 110 is determined. The target rotational speed TNE may be set to an appropriate value by the developer in consideration of various conditions.

  Second motor generator 120 is a three-phase AC rotating electric machine including a U-phase coil, a V-phase coil, and a W-phase coil. Second motor generator 120 is driven by at least one of the electric power stored in battery 150 and the electric power generated by first motor generator 110.

  The driving force of the second motor generator 120 is transmitted to the front wheels 160 via the speed reducer 140. As a result, the second motor generator 120 assists the engine 100 or causes the vehicle to travel by the driving force from the second motor generator 120. The rear wheels may be driven instead of or in addition to the front wheels 160.

  During regenerative braking of the hybrid vehicle, the second motor generator 120 is driven by the front wheels 160 via the speed reducer 140, and the second motor generator 120 operates as a generator. Accordingly, second motor generator 120 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by second motor generator 120 is stored in battery 150.

  Power split device 130 includes a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so that it can rotate. The sun gear is connected to the rotation shaft of first motor generator 110. The carrier is connected to the crankshaft of engine 100. The ring gear is connected to the rotation shaft of second motor generator 120 and speed reducer 140.

  The engine 100, the first motor generator 110, and the second motor generator 120 are connected via a power split mechanism 130 that is a planetary gear, so that the rotational speeds of the engine 100, the first motor generator 110, and the second motor generator 120 are increased. Are connected by a straight line in the nomograph.

  The battery 150 is an assembled battery configured by connecting a plurality of battery modules in which a plurality of battery cells are integrated in series. The voltage of the battery 150 is about 200V, for example. The battery 150 is charged with electric power supplied from a power source external to the vehicle in addition to the first motor generator 110 and the second motor generator 120. A capacitor may be used instead of or in addition to the battery 150. The temperature of the battery 150 is detected by the temperature sensor 152.

  With reference to FIG. 2, the electric system of the hybrid vehicle will be further described. The hybrid vehicle is provided with a converter 200, a first inverter 210, a second inverter 220, and a system main relay 230.

  Converter 200 includes a reactor, two npn transistors, and two diodes. One end of the reactor is connected to the positive electrode side of each battery, and the other end is connected to the connection point of the two npn transistors.

  Two npn-type transistors are connected in series. The npn transistor is controlled by the ECU 170. A diode is connected between the collector and emitter of each npn transistor so that a current flows from the emitter side to the collector side.

  For example, an IGBT (Insulated Gate Bipolar Transistor) can be used as the npn transistor. Instead of the npn type transistor, a power switching element such as a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) can be used.

  When the electric power discharged from the battery 150 is supplied to the first motor generator 110 or the second motor generator 120, the voltage is boosted by the converter 200. Conversely, when charging the battery 150 with the electric power generated by the first motor generator 110 or the second motor generator 120, the voltage is stepped down by the converter 200.

  System voltage VH between converter 200 and each inverter is detected by voltage sensor 180. The detection result of voltage sensor 180 is transmitted to ECU 170.

  First inverter 210 includes a U-phase arm, a V-phase arm, and a W-phase arm. The U-phase arm, V-phase arm and W-phase arm are connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two npn transistors connected in series. Between the collector and emitter of each npn-type transistor, a diode for passing a current from the emitter side to the collector side is connected. A connection point of each npn transistor in each arm is connected to an end portion different from neutral point 112 of each coil of first motor generator 110.

  First inverter 210 converts a direct current supplied from battery 150 into an alternating current and supplies the alternating current to first motor generator 110. The first inverter 210 converts the alternating current generated by the first motor generator 110 into a direct current.

  Second inverter 220 includes a U-phase arm, a V-phase arm, and a W-phase arm. The U-phase arm, V-phase arm and W-phase arm are connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two npn transistors connected in series. Between the collector and emitter of each npn-type transistor, a diode for passing a current from the emitter side to the collector side is connected. A connection point of each npn transistor in each arm is connected to an end portion different from neutral point 122 of each coil of second motor generator 120.

  Second inverter 220 converts a direct current supplied from battery 150 into an alternating current, and supplies the alternating current to second motor generator 120. Second inverter 220 converts the alternating current generated by second motor generator 120 into a direct current.

  Converter 200, first inverter 210, and second inverter 220 are controlled by ECU 170.

  System main relay 230 is provided between battery 150 and converter 200. The system main relay 230 is a relay that switches between a state where the battery 150 and the electric system are connected and a state where the battery 150 is disconnected. When system main relay 230 is in an open state, battery 150 is disconnected from the electrical system. When system main relay 230 is in a closed state, battery 150 is connected to the electrical system.

  The state of system main relay 230 is controlled by ECU 170. For example, when ECU 170 is activated, system main relay 230 is closed. When ECU 170 stops, system main relay 230 is opened.

  With reference to FIG. 3, the control mode of engine 100 will be further described. As shown in FIG. 3, when the output power of the hybrid vehicle becomes equal to or higher than the engine start threshold value, engine 100 is driven. For example, the engine 100 is started by cranking the engine 100 by the first motor generator 110. Thus, the hybrid vehicle travels using the driving force of engine 100 in addition to or instead of the driving force of second motor generator 120. Further, the electric power generated by first motor generator 110 using the driving force of engine 100 is directly supplied to second motor generator 120.

  The output power is set as power used for running the hybrid vehicle. The output power is calculated by ECU 170 according to a map having, for example, the accelerator opening and the vehicle speed as parameters. The method for calculating the output power is not limited to this. Instead of output power, torque, acceleration, driving force, accelerator opening, and the like may be used. For example, engine 100 may be driven when the accelerator opening is equal to or greater than a threshold value determined for each vehicle speed.

  On the other hand, when the output power of the hybrid vehicle is smaller than the engine start threshold, the hybrid vehicle travels using only the driving force of second motor generator 120. In this case, in principle, the fuel supply to engine 100 is stopped, and engine 100 is stopped.

  Processing executed by ECU 170 will be described with reference to FIG. Note that the processing described below may be realized by software or hardware.

  Whether or not feedback control is being executed in step (hereinafter abbreviated as S) 100 in order to control the torque of first motor generator 110 in accordance with the difference between engine speed NE and target speed TNE Is judged.

  If feedback control is being executed (YES in S100), it is determined in S102 whether or not accelerator pedal 172 has been turned off from on, in other words, whether or not the accelerator opening has been reduced to zero. .

  If the accelerator opening has not decreased to zero (NO in S102), it is determined in S104 whether the elapsed time since the shift operation is performed is less than a predetermined threshold value. As an example, more specifically, a garage shift operation is performed to change the shift position from a travel position (forward position or reverse position) to a non-travel position (neutral position or parking position) or from a non-travel position to a travel position. It is determined whether the elapsed time from is less than a threshold value.

  If the elapsed time after the shift operation is equal to or greater than a predetermined threshold (NO in S104), the shift position is the parking position and engine 100 is in a load operation or an idle operation in S106, or Whether or not the engine 100 is being motored is determined by the first motor generator 110.

  A known technique is used to determine whether the engine 100 is in a load operation, whether the engine 100 is in an idle operation, and whether the engine 100 is being motored by the first motor generator 110. Therefore, detailed description thereof will not be repeated here.

  If the accelerator opening is reduced to zero (YES in S102), if the elapsed time after the shift operation is less than a predetermined threshold (YES in S104), the shift position is the parking position. When engine 100 is in a load operation (YES in S106), the shift position is a parking position, and when engine 100 is in an idle operation (YES in S106), the shift position is a parking position. If the engine 100 is being motored by first motor generator 110 (YES in S106), it is determined in S108 whether or not target rotational speed TNE has changed. As an example, more specifically, it is determined whether or not the target rotational speed TNE has decreased.

  If the target rotational speed TNE changes in the above-described state (YES in S108), as shown in FIG. 5, the actual engine rotational speed NE indicated by a solid line and the target rotational speed TNE indicated by a broken line may be greatly different. Therefore, the torque of first motor generator 110, which is determined in feedback control using the difference between engine speed NE and target speed TNE, can vary greatly. FIG. 5 shows that the absolute value of the torque of first motor generator 110 increases in the direction of decreasing engine speed NE, that is, the direction in which engine 100 is loaded. When the absolute value of the torque of the first motor generator 110 is increased, a large shock of the vehicle can occur.

  Therefore, when target speed TNE changes (YES in S108), more specifically, when target speed TNE decreases, the rate of change in the amount of change in target speed TNE of engine 100 changes in S110 of FIG. It is limited to a predetermined upper limit value or less. As a result, as shown in FIG. 6, the rate of change in the amount of change in target rotational speed TNE of engine 100 is reduced as compared with the case where the rate of change in amount of change in target rotational speed TNE of engine 100 is not limited.

  In the present embodiment, “the amount of change in target engine speed TNE of engine 100” refers to a differential value of “target engine speed TNE of engine 100”, and “the rate of change in target engine speed TNE of engine 100”. Means the same. “Change rate of change amount of target rotational speed TNE of engine 100” refers to a second-order differential of “target rotational speed TNE of engine 100”, and “change rate of change rate of target rotational speed TNE of engine 100” It has the same meaning.

  By limiting the rate of change of the target engine speed TNE of the engine 100 to the upper limit value or less, as shown in FIG. 7, the target engine speed TNE is delayed compared to the target engine speed TNE before the limit indicated by the broken line. Can be changed.

  Therefore, as shown in FIG. 8, it is possible to prevent the actual engine speed NE indicated by the solid line and the target speed TNE indicated by the broken line from greatly deviating from each other. Therefore, it is possible to reduce the torque fluctuation amount of first motor generator 110, which is determined in the feedback control using the difference between engine speed NE and target speed TNE.

  When the target rotational speed TNE increases, the change rate of the amount of change in the target rotational speed TNE of the engine 100 may be limited to an upper limit value or less.

  The upper limit value may be increased as time passes. In this way, as shown in FIG. 9, the gradient of the change amount of the target rotational speed TNE can be increased as time elapses. Therefore, as time passes, the amount of change in the target rotational speed TNE can be increased in a parabolic shape. Therefore, immediately after the target rotational speed TNE changes, the target rotational speed TNE can be quickly changed to a desired value while suppressing a sudden change in the target rotational speed TNE.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Engine, 102 Catalyst, 104 Speed sensor, 110 First motor generator, 120 Second motor generator, 130 Power split mechanism, 140 Reducer, 150 Battery, 160 Front wheel, 170 ECU, 172 Accelerator pedal.

Claims (8)

A control device for a vehicle equipped with an engine and an electric motor coupled to the output shaft of the engine,
Control means for controlling the torque of the electric motor connected to the output shaft of the engine according to the difference between the actual output shaft rotational speed of the engine and the target rotational speed;
A control device for a vehicle, comprising: limiting means for limiting a change rate of a change amount of the target rotational speed to a predetermined upper limit value or less when the target rotational speed changes.   2. The vehicle control device according to claim 1, wherein the limiting unit increases the upper limit value as time elapses.   3. The vehicle control device according to claim 1, wherein when the target rotational speed is reduced, the limiting unit limits a change rate of a change amount of the target rotational speed to the upper limit value or less.   4. The vehicle according to claim 3, wherein when the accelerator opening decreases to zero and the target rotational speed decreases, the limiting means limits the rate of change of the change amount of the target rotational speed to the upper limit value or less. Control device.   4. The vehicle control device according to claim 3, wherein when the shift operation is performed and the target rotational speed decreases, the limiting means limits the change rate of the change amount of the target rotational speed to the upper limit value or less. 5.   4. The vehicle according to claim 3, wherein when the target rotational speed decreases while the engine is operating under load, the limiting means limits the rate of change of the amount of change in the target rotational speed to the upper limit value or less. Control device.   4. The vehicle according to claim 3, wherein when the target rotational speed decreases while the engine is idling, the limiting means limits the change rate of the change amount of the target rotational speed to the upper limit value or less. Control device.   The limiting means limits the rate of change of the amount of change in the target rotational speed to the upper limit value or less when the target rotational speed decreases while the engine is being motored by the electric motor. The vehicle control device described.

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