JP2012254688A - Shift control device of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control shock in upshift to change the gear ratio in stepwise in a hybrid vehicle.SOLUTION: A shift control device of the hybrid vehicle which includes an engine and electric generator as a driving power source, and can change the gear ratio in stepwise by controlling the engine speed by the electric generator, includes a shift speed setting means (step S107) which changes faster the shift speed of the upshift as larger the friction torque generated by the engine when the supply of the fuel to the engine is stopped in order to perform upshift to decreases the gear ratio. The friction torque can be offset by the inertia torque according to the decrease in the rotation speed, and smoothing change in the drive torque.

Description

  The present invention relates to a hybrid vehicle including an engine and a generator or a motor as a power source, and more particularly to a device that performs shift control for changing the engine speed with respect to the vehicle speed.

  Various types of hybrids in vehicles are known. As an example, a hybrid drive device configured to divide the power output from the engine into a wheel side and a generator (or a motor / generator) is known. . In this type of hybrid drive system, not only can the energy be regenerated, but the engine speed can be controlled by the generator as part of the driving force output by the engine is converted into electric power. It is possible to improve the fuel efficiency of the vehicle as a whole by controlling the engine speed to the optimum fuel efficiency.

  Control of the engine speed by the generator in this type of hybrid drive apparatus can be arbitrarily performed in terms of the configuration of the apparatus, and therefore, the ratio of the engine speed to the vehicle speed, that is, the gear ratio is maintained at a predetermined value. Is also possible. An example is described in Patent Document 1, and six types of gear ratios, which are ratios of engine speed to vehicle speed or output shaft speed, are prepared, and those gear ratios are selected based on the running state of the vehicle or manual operation. Japanese Patent Application Laid-Open No. H10-228867 describes an apparatus configured to set the above. In addition, in the device described in Patent Document 1, the engine power is reduced at the time of upshifting to reduce the gear ratio, and in that case, inertia power is generated as the engine speed decreases. The engine is controlled up to the power obtained by reducing the inertia power.

  Conventionally, since a shock is generated when the drive torque changes suddenly at the time of shifting, the change in torque before and after the shifting is made smooth. The same applies to a continuously variable transmission. For example, in Patent Document 2, when a gear ratio can be selected by manual operation and a torque difference before and after a gear shift or a gear ratio difference is large, A continuously variable transmission configured to slow down the shift speed as compared with a small case is described.

JP 2008-179291 A JP 2006-071005 A

  If the engine power is reduced in consideration of the inertia power accompanying the shift as described in Patent Document 1, the upshift proceeds quickly and the shift feeling is improved. However, depending on what is called traveling conditions such as engine output and vehicle speed during upshifting, it is necessary to greatly reduce the engine power, and the target power may be below the lower limit value that can be output by the engine. In such a case, in the device described in Patent Document 1, the engine power cannot be reduced to the target value, so that the upshift does not proceed, and there is a possibility that a shift delay or a sense of incongruity due to the shift may occur. . Note that the device described in Patent Document 2 is configured to reduce the shift speed and suppress the amount of torque change or shock, so that the actual shift can be performed while the shift is performed manually. Since it becomes slow, drivability may be deteriorated or uncomfortable.

  The present invention has been made paying attention to the above technical problem, and in a hybrid vehicle configured to advance the upshift by lowering the engine speed by the generator, the engine output is stopped and the engine is stopped. An object of the present invention is to provide a shift control device capable of improving a shock when a shift is advanced.

  In order to achieve the above object, the invention of claim 1 includes an engine and a generator as driving force sources, and controls the rotational speed of the engine by the generator to change the gear ratio stepwise. When the fuel supply to the engine is stopped to perform an upshift that reduces the gear ratio, the higher the friction torque generated in the engine, the higher the shift speed of the upshift. A speed change speed setting means for increasing the speed is provided.

  According to a second aspect of the present invention, in the first aspect of the invention, the generator includes a generator that generates electric power when power output from the engine is transmitted, and the shift speed setting means generates electric power with the generator. A shift control apparatus for a hybrid vehicle comprising means for increasing a required torque to increase the shift speed.

  According to the present invention, when the fuel supply to the engine is stopped during the upshift in which the speed change ratio is reduced by reducing the engine speed by the generator, the friction torque determined from the speed of the hybrid vehicle or the engine. The transmission speed is determined according to the above. That is, the greater the friction torque, the faster the speed change speed. As a result, the increase in the inertia torque accompanying the decrease in the engine speed can suppress the decrease in the generator torque and the engine torque due to the friction torque. Shock can be prevented or suppressed.

  According to the second aspect of the present invention, when the engine speed is decreased by the generator in accordance with the shift speed set by the shift speed setting means, it is possible to suppress excessive increase in generated power and power consumption. Alternatively, the energy balance in a power storage device such as a battery to which a generator is connected is prevented.

It is a flowchart for demonstrating an example of the control performed by the transmission control apparatus which concerns on this invention. It is an example of the map which defined target shift time. 2 is a time chart showing changes in drive torque, engine speed, and first motor / generator speed when the control shown in FIG. 1 is executed. FIG. 2 is a time chart showing changes in drive torque, engine speed, and first motor / generator speed when the control shown in FIG. 1 is not executed during upshift with fuel cut. FIG. It is a schematic diagram which simplifies and shows the drive system and control system of the hybrid vehicle which can be the object of the present invention. It is a collinear diagram about the planetary gear mechanism that constitutes the power split mechanism. It is a figure which shows an example of the gear stage map which defined the relationship between an engine speed, a vehicle speed, and a gear stage. It is a figure which shows the relationship between engine power and an engine speed.

  The hybrid vehicle targeted by the speed change control device according to the present invention includes an engine and a generator (or a motor / generator), and controls the rotational speed of the engine with the power generator, so that the rotational speed of the drive wheels and the output shaft is controlled. The hybrid vehicle is configured to set a gear ratio, which is a ratio between the engine speed and the engine speed, to a predetermined value, and to execute a gear shift that changes the gear ratio. An example of a hybrid drive apparatus in this type of vehicle is an apparatus configured to connect an engine to a power split mechanism and to split power output from the engine into an output side and a generator side by the power split mechanism. is there. This is schematically shown in FIG. 5, and an internal combustion engine (hereinafter referred to as an engine) 1 such as a gasoline engine or a diesel engine is connected to a power split mechanism 2. The power split mechanism 2 is a mechanism having a differential action, and is constituted by a planetary gear mechanism as an example. The sun gear 3, the ring gear 4 arranged concentrically with the sun gear 3, the sun gear 3 and And a carrier 5 for holding the pinion gear meshing with the ring gear 4 so as to rotate and revolve freely. The engine (E / G) 1 is connected to the carrier 5 and the sun gear 3 is connected to a first motor / generator (MG1) 6 corresponding to the generator in the present invention. The ring gear 4 serves as an output element and outputs a driving force to driving wheels (not shown). The ring gear 4 is connected to a second motor / generator (MG2) 7 that outputs electric power as driving force or regenerates traveling inertia energy of the vehicle as electric power.

  These motor generators 6 and 7 are electrically connected to a power storage device such as a battery and a controller 8 including an inverter. Further, an electronic control unit (ECU) 9 for controlling power generation by each motor / generator 6, 7, driving as a motor, torque and rotational speed thereof is electrically connected to the controller 8. This electronic control unit 9 is mainly composed of a microprocessor, performs calculations using data input from various sensors (not shown) and prestored data, and uses the result of the calculation as a control signal as a controller. 8 is configured to output to 8.

  A collinear diagram of the planetary gear mechanism constituting the power split mechanism 2 is shown in FIG. 6, where “S” indicates the sun gear 3, “C” indicates the carrier 5, and “R” indicates the ring gear 4. The arrows indicate the direction of torque applied to each of these rotating elements. A load (resistance force) that accompanies traveling acts on the ring gear 4 that is an output element, and on the other hand, the driving torque output from the engine 1 acts on the carrier 5. Then, by causing the first motor / generator 6 to function as a generator, a torque in a direction of reducing the rotational speed acts on the sun gear 3. Accordingly, in such a driving state, the rotational speed of the engine 1 increases / decreases in accordance with the increase / decrease of the rotational speed of the first motor / generator 6, so that the first motor / generator 6 controls the vehicle speed or the rotational speed of the drive wheels. The speed ratio that is the rotational speed of the engine 1 can be controlled appropriately. For example, in the control with an emphasis on fuel efficiency, the rotational speed at which the fuel efficiency at the required output is minimized is obtained, and the rotational speed of the first motor / generator 6 is controlled so that the engine rotational speed becomes the rotational speed. The Further, in order to improve the power performance and the so-called sportiness, the rotational speed of the first motor / generator 6 is controlled so as to be the engine rotational speed corresponding to the speed ratio selected based on the manual operation. The Briefly explaining an example of the control for setting the gear ratio based on such manual operation, the relationship among the vehicle speed V, the engine speed Ne, and each gear stage illustrated in FIG. 7 is prepared in advance as a map. The target engine speed Ne is calculated from the map based on the vehicle speed V and the gear stage selected at that time. Then, the target torque of the engine 1 is calculated by dividing the target power by the target engine speed Ne, and the engine 1 is controlled so as to output the target torque. In a gasoline engine, the throttle opening is controlled.

  In the above hybrid vehicle, when performing an upshift to reduce the gear ratio, which is the ratio between the rotational speed of the drive wheel or output shaft and the engine rotational speed, the engine determined by the speed ratio after shifting and the vehicle speed or output shaft rotational speed The engine speed is decreased by the first motor / generator 6 with the engine speed as the target engine speed. The control is first performed by reducing the rotational speed by reducing the power output by the engine 1. The target reduction amount of the power is the target shift speed, the gear ratio of the planetary gear mechanism constituting the power split mechanism 2, the rotational speed of the first motor / generator 6, the first motor / generator 6 and the engine 1. It depends on the moment of inertia. Therefore, when the reduction amount of the engine power is large, the required output power of the engine 1 may be lower than the lower limit output power. In such a case, the supply of fuel to the engine 1 is stopped.

  FIG. 8 is a diagram for explaining the situation, in which the engine power is taken on the vertical axis, the engine speed is taken on the horizontal axis, and the higher the engine speed, the more the engine 1 can output. Maximum power increases. Further, the amount of fuel supplied to the engine 1 and its combustion efficiency (output efficiency) are substantially determined by the structure of the engine 1, and therefore the lower limit output power of the engine 1 in the state where fuel is being supplied is also substantially determined. In FIG. 8, this is described as “predetermined value”. A region between the maximum power line and the lower limit power line described as “predetermined value” is an area where the output power of the engine 1 can be reduced (down). Further, since the negative output power generated in the engine 1 when the fuel supply is stopped is mostly due to friction and air compression, the absolute value thereof increases as the engine speed increases. This is described as “fuel cut line” in FIG. The area between the fuel cut line and the above-mentioned “predetermined value” line is a region where the engine power is reduced by fuel cut (FC).

  Then, an upshift request is generated at the engine operating point indicated by reference numeral “P1” in FIG. 8, and the engine power indicated by reference numeral “P2” is required due to the large amount of engine power reduction required. is there. In that case, since the operating point of the engine 1 is below the lower limit line, the supply of fuel to the engine 1 is stopped. In that case, since the output power (negative output power) generated by the engine 1 cannot be actively controlled, there is a possibility that the driving torque of the vehicle will be excessively reduced, resulting in so-called torque loss and accompanying shock. In order to prevent or suppress this, the control device according to the present invention is configured to perform the control described below.

  FIG. 1 is a flowchart for explaining an example of the control, and is repeatedly executed every predetermined short time when an upshift is requested. First, the target shift speed is set from the deviation between the target engine speed and the actual engine speed, and the target shift speed is calculated (step S101). Here, the target engine speed can be obtained based on the vehicle speed or output shaft speed at that time and the speed ratio after the upshift. Further, the actual engine speed can be obtained by a sensor generally mounted on the engine 1. Furthermore, a preferable value for the target shift time can be prepared in advance by experiment, simulation, or the like. That is, in the case of a stepped shift, the amount of change or the range of the change in the rotational speed that accompanies the speed change varies depending on the vehicle speed. For example, in an upshift from the third speed to the fourth speed, Become. On the other hand, it is desirable to keep the time required for shifting within a certain amount of time in terms of the feeling given to the driver such as so-called shift feeling. Therefore, the shift time is determined experimentally or empirically, and the shift speed is determined so that the shift is completed within that time. FIG. 2 shows an example. The “mode” in FIG. 2 is a mode that can be selected by the driver or preset in the vehicle, or a mode of change thereof. “Normal” means that the driving force is not particularly large. The change is not particularly quick, and is a mode set to perform so-called mild driving. “Sport” is a mode in which the driving force is relatively large and the change is relatively agile.

  In the above hybrid vehicle, the engine speed is controlled by the first motor / generator 6. Therefore, when performing an upshift, the target value (target MG1 speed) for the first motor / generator 6 is set. ) And the actual value (actual MG1 rotation speed) is obtained (step S102). As known from the collinear chart shown in FIG. 6 described above, the vehicle speed or the output shaft rotational speed, the engine rotational speed, and the first rotational speed are the gear ratio of the planetary gear mechanism constituting the power split mechanism 2. Since the parameters are related to each other, the target rotational speed of the first motor / generator 6 can be obtained from the target engine rotational speed.

Next, the required down amount is calculated from the target shift speed of the shaft to which the first motor / generator 6 is connected (the sun gear shaft in the example shown in FIG. 5) and the actual rotational speed of the first motor / generator 6. Then, the required engine power during the upshift is calculated (step S103). The rotational speed of the first motor / generator 6, the engine rotational speed, and the vehicle speed are in the relationship shown in the collinear chart of FIG. 6. Therefore, even if the engine rotational speed is the same, if the vehicle speed is different, the first motor Since the rotational speed of the generator 6 is different, the deviation of the engine rotational speed obtained in step S101 described above is converted into the rotational speed deviation of the shaft to which the first motor / generator 6 is connected, and based on this, the required engine power is converted. The down amount (decrease amount) ΔPe is calculated. The calculation can be performed by the following equation.
ΔNetgt × [(1 + rh0) / rh0] × Ng × {Ig + Ie × [(1 + rh0) / rh0] ² }
Here, ΔNetgt is the target speed determined in step S101, rh0 is the gear ratio of the planetary gear mechanism constituting the power split mechanism 2 described above (ratio between the number of teeth of the sun gear 3 and the number of teeth of the ring gear 4). , Ng is the actual rotational speed of the first motor / generator 6, Ig is the moment of inertia of the first motor / generator 6, and Ie is the moment of inertia of the engine 1. The required engine power down amount obtained in this way corresponds to the difference in power between the operating point indicated by the symbol “P1” and the operating point indicated by the symbol “P2” shown in FIG. The required engine power at the time of upshift can be calculated by subtracting the required engine power down amount from the power.

  In the subsequent step S104, it is determined whether or not the required engine power during the upshift is equal to or greater than a predetermined value shown in FIG. 8, that is, a lower limit power in a state where fuel is being supplied. In short, it is determined whether or not the target value of the engine output power can be achieved by reducing the fuel supply amount. If the determination in step S104 is affirmative, control for reducing the output power of the engine 1 is executed based on the required engine power down amount (step S105), and then the routine shown in FIG. The Specifically, the intake air amount or the fuel supply amount (fuel injection amount) is controlled so that the required engine power is obtained.

  On the other hand, if a negative determination is made in step S104, fuel cut (FC) is performed (step S106). That is, if fuel is supplied to the engine 1 even if it is at a minimum, a power larger than the required engine power is output, so that the fuel supply to the engine 1 is stopped. The engine 1 generates a negative torque when the fuel supply is stopped. However, since the inertia torque is generated in the process in which the rotational speed is decreased, the engine 1 is used as a drive torque to change the drive torque. In order to make it smooth, the target shift speed associated with the fuel cut is calculated (step S107), and then the routine of FIG. 1 is once ended.

The target shift speed is given by the following equation.
(−Pm + Win + Pefc) / Snesin / {Ig + Ie × [(1 + rh0) / rh0] ² }
Here, Pm is a motor output, which may be replaced with a battery output Pbatt. Win is the battery charge upper limit value, Pefc is the engine power, that is, the friction torque in a state where the fuel cut is executed, and can be obtained in advance in the form of a map or the like using the engine speed as an argument. Furthermore, Snesin is the engine speed at the present time. Therefore, the target shift speed at the time of the upshift with fuel cut increases as the friction torque of the engine 1 increases. In other words, in this state, the rotational speed of the engine 1 is decreased relatively quickly, and the inertia torque increases accordingly, so that a drop in the drive torque is suppressed.

  FIG. 3 is a time chart showing changes in drive torque and engine speed when the above control is executed when the gear ratio is changed stepwise from the third speed to the fourth speed as the vehicle speed increases. It is. In FIG. 3, a solid line indicating engine power and driving torque indicates a real value, and a broken line indicates a command value. When a request for an upshift from the third speed to the fourth speed occurs at time t1 when the vehicle travels at the third speed and the vehicle speed is gradually increasing, first, a rotational speed deviation of the first motor / generator 6 occurs. In addition, control for reducing the engine power is executed. The shift to the fourth speed is started at time t2 when the engine power is reduced to almost zero, and the fuel supply to the engine 1 is stopped (fuel cut). Since the upshift to the fourth speed is executed by reducing the engine speed, the speed of the engine 1 is reduced by reducing the speed of the first motor / generator 6 from the time t2.

  As the torque of the first motor / generator 6 (specifically, the power generation torque) increases, the engine speed decreases more rapidly and the shift speed becomes faster, so that the shift speed becomes the target shift speed described above. The torque of the first motor / generator 6 is controlled, and therefore the torque of the first motor / generator 6 gradually increases in the negative direction as the shift proceeds. Accordingly, the change rate (change rate) of the engine speed approximates the change in the torque of the first motor / generator 6. In this process, the inertia torque that accompanies the decrease in the rotational speed of the engine 1 appears as the drive torque. Therefore, even if the engine 1 outputs a negative torque by executing fuel cut, the drive torque is It drops smoothly and so-called shock is prevented or suppressed. In addition, since the inertial torque of the engine 1 is output as a driving torque and power generation is continued in the first motor / generator 6 using a part of the inertial torque, the battery power is the upper limit of charging and discharging. Small change within range. Therefore, excessive charging and excessive discharging do not occur, and the power balance of the battery is improved.

  Then, the engine speed and the rotation speed of the first motor / generator 6 approach the rotation speed determined based on the speed ratio after the shift and the vehicle speed (so-called synchronous rotation speed after the shift), and the deviation is a predetermined value. The fuel cut is terminated at the time t3 when the following is reached, and the fuel supply to the engine 1 is resumed.

  For comparison, changes in drive torque, engine speed, etc., when fuel cut is executed during upshift from 3rd speed to 4th speed and shift is advanced at engine speed by fuel cut Is shown in FIG. In this case, after the shift request is generated, while the engine 1 is outputting power, the torque of the first motor / generator 6 is increased in the negative direction to increase the amount of power generation. When the engine 1 is in a state of outputting a negative torque, the first motor / generator 6 functions as a motor to increase the discharge amount. In the course of such control, the drive torque decreases in accordance with the fuel cut, which becomes a so-called torque loss and the shock is worsened. In addition, the battery may be charged exceeding the upper limit of charge or discharged at the discharge limit, resulting in a deterioration in the power balance of the battery.

  Here, the relationship between the above specific example and the present invention will be briefly described. The functional means for executing the control in step S107 shown in FIG. 1 corresponds to the shift speed setting means in the present invention.

  The above example is an example of an upshift from the third speed to the fourth speed, but the present invention can be similarly controlled during an upshift between other shift stages. The hybrid vehicle targeted by the present invention may be any vehicle that can control the engine speed by a generator or a motor / generator. Therefore, the hybrid device has the configuration shown in FIG. Not limited to.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine (engine), 2 ... Power split mechanism, 3 ... Sun gear, 4 ... Ring gear, 5 ... Carrier, 6 ... 1st motor generator (MG1), 7 ... 2nd motor generator (MG2), 8 ... Controller, 9 ... Electronic control unit (ECU).

Claims (2)

In a shift control apparatus for a hybrid vehicle that includes an engine and a generator as a driving force source, and that can control the rotational speed of the engine by the generator and change the gear ratio stepwise.
When the supply of fuel to the engine is stopped in order to perform an upshift that reduces the gear ratio, a shift speed setting means is provided that increases the shift speed of the upshift as the friction torque generated in the engine increases. A shift control apparatus for a hybrid vehicle characterized by the above. The generator includes a generator that generates power by transmitting power output from the engine,
2. The shift control apparatus for a hybrid vehicle according to claim 1, wherein the shift speed setting means includes means for increasing the torque required for power generation by the generator to increase the shift speed.

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