JP2017088052A - Vehicular control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular control apparatus capable of reducing a gear change shock, while improving fuel economy of the entire vehicle, when down-shifting while coasting.SOLUTION: When a revolution speed NE of an engine 1 is decreased to a predetermined given revolution speed that is equal to or higher than a fuel-cut-permissible revolution speed during an inertia travel with the fuel supply to the engine 1 cut, a controller 4 restarts the fuel supply to the engine 1 to drive the engine 1, where driving of the engine 1 is such that: the engine 1 outputs torque equivalent to friction torque of the engine 1 in the state of fuel-cut so that a change rate of the revolution speed NE of the engine 1 is within a predetermined given value; a down-shift is executed in a case where the change rate of the revolution speed of the engine 1 falls within the given value; and the fuel supply to the engine 1 is stopped again after a revolution speed NE of the engine 1 increases as a result the controller driving the engine as aforementioned.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vehicle control device that controls an engine mounted on a vehicle and a stepped automatic transmission, and more particularly, a device that performs control for reducing fuel cut and shift shock during a downshift during a coast. It is about.

  Patent Document 1 describes a control device for a stepped automatic transmission having a plurality of fastening elements. The control device described in Patent Document 1 is designed to prevent inertia when the vehicle is downshifted during coasting and the vehicle acceleration increases to the negative side, resulting in poor driving feeling. The fuel cut recovery is performed during the control period in the phase. Further, at that time, the number of cylinders that perform fuel cut recovery is limited.

  Patent Document 2 describes a control device for a torque converter with a lock-up and a power train having a plurality of shift stages. The control device described in Patent Document 2 controls the slip amount of the lockup clutch during the deceleration operation, prevents a sudden decrease in the engine rotation speed, and maintains the engine rotation speed in the fuel cut region. Thus, the speed change mechanism is configured to downshift.

  Further, in Patent Document 3, a fuel supply is performed while a fuel cut is performed due to a shock caused by a sudden change in engine brake due to a downshift during the coast, or because the engine speed falls below the fuel cut return speed. There is described a vehicle drive control device that is intended to be restarted and prevent fuel consumption from being impaired. The control device described in Patent Document 3 is configured such that the fuel-cut return rotational speed is continuously changed as the engine load is continuously changed by the variable capacity air conditioner. In addition, the vehicle speed at the time of downshift and the vehicle speed at the time of upshift during the coast according to the continuous change of the fuel cut return rotation speed so that the fuel cut is continued regardless of the change of the fuel cut return rotation speed. Are configured to be continuously changed.

  Patent Document 4 describes a vehicle control device for the purpose of extending the time for performing fuel cut control while suppressing the occurrence of a shift shock. The control device described in Patent Document 4 is configured such that the fuel cut return rotational speed at the time of downshift during fuel cut control is set to a lower speed than the fuel cut rotational speed at the time of normal control. Yes.

  Further, Patent Document 5 discloses that during a coast where fuel cut is performed, the engine rotation speed falls below the fuel cut return rotation speed and fuel supply is resumed, thereby preventing the fuel consumption from being impaired and reducing the engine braking force due to the downshift. A vehicle drive control device for reducing the occurrence of a shock due to a sudden change is described. The control device described in Patent Document 5 is configured to temporarily expand the air passage on the intake side of the engine while maintaining the fuel cut when a downshift is performed during coasting.

JP 2012-251575 A JP 2008-179179 A JP 2011-089642 A JP 2010-125874 A JP-A-2005-162205

  In order to reduce the shift shock accompanying the downshift in the coast state, it is effective to reduce the negative torque acting on the input side of the transmission, as described in Patent Document 1, for example. That is, in the control device described in Patent Literature 1, by limiting the number of cylinders that perform fuel cut recovery, the variation in the torque increase caused by the fuel cut recovery is reduced by the amount that limits the number of cylinders. Therefore, the increase in torque caused by the fuel cut recovery at the time of downshift during coasting is close to the target value, and it is possible to alleviate the feeling of entrainment due to reduction of shift shock and reduction of coasting torque to stop the vehicle. it can.

  However, depending on the timing of fuel cut recovery and the amount of torque increase, the fuel consumption of the entire vehicle may be deteriorated. That is, there is room for studying when and how to implement the minimum torque increase control in order to reduce the shift shock while improving the fuel efficiency of the entire vehicle.

  The present invention has been made paying attention to the technical problem described above, and provides a vehicle control device capable of reducing the shift shock while improving the fuel efficiency of the entire vehicle at the time of downshift during coasting. It is intended to provide.

  In order to achieve the above object, the present invention is directed to a method in which when the vehicle having an engine and a stepped automatic transmission connected to the output side of the engine is coasting, the rotational speed of the engine is a fuel. The automatic transmission stops supply of fuel to the engine when the engine speed is equal to or higher than the cut-permitted speed, and maintains the engine speed at a speed equal to or higher than the fuel-cut permitted speed during the inertia traveling. And a controller for controlling the fuel supply of the engine and the shift of the automatic transmission, wherein the controller stops the fuel supply to the engine. When the engine speed decreases to a predetermined speed that is equal to or higher than the fuel cut permission speed during the inertia running, The fuel is restarted to drive the engine, and the engine is driven by the engine in the fuel cut state so that the rate of change of the engine speed is within a predetermined value. The engine is executed so that the torque corresponding to the friction torque is output, and when the rate of change of the engine speed falls within the predetermined value due to the driving of the engine, the downshift is executed, and the downshift is executed. Thus, after the engine speed increases, the fuel supply to the engine is stopped again.

  According to the present invention, the engine speed when performing a downshift during coasting is set to a higher speed than the normal fuel cut permission speed. Further, when the engine speed is lower than the engine speed, torque increase control is performed so that the sum of the engine torque and the friction torque with respect to the engine becomes 0 (zero). That is, it is configured to output a torque corresponding to the friction torque from the engine. Therefore, the behavior of the engine speed can be stabilized at a higher speed than the fuel cut permission speed. As a result, even when a downshift point is provided on the high vehicle speed side, a shift (downshift) can be started after the behavior of the engine speed is stabilized, so that a shift shock can be suppressed. In addition, since the behavior of the engine speed can be stabilized, the engine speed can be maintained longer in the engine speed range where the fuel can be cut, so that the fuel efficiency of the entire vehicle can be improved. .

It is a flowchart for demonstrating an example of the control performed by the control apparatus of the vehicle of this invention. It is a figure which shows an example of the structure of the vehicle used as the object of control by this invention, and a control system. It is a time chart for demonstrating an example of the control performed by the control apparatus of the vehicle in the Example of this invention. It is a time chart for demonstrating the torque increase control performed by the vehicle control apparatus in the Example of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings. A vehicle to which the present invention can be applied is a vehicle equipped with an automatic transmission capable of shifting the power output from an engine and transmitting it to drive wheels.

  As an example of a vehicle to which the present invention can be applied, FIG. 2 shows the configuration and control system of a vehicle in which an automatic transmission is mounted on the output side of the engine. This vehicle Ve passes the power output from the engine (ENG) 1 to a rear wheel via an automatic transmission (AT) 2 and a differential gear (not shown) via a torque converter (not shown) with a lock-up. It is configured as a rear wheel drive vehicle (FR (Front Engine Rear Drive) vehicle) that transmits driving force to generate. The vehicle Ve to which the present invention can be applied may be a front wheel drive vehicle (FF (Front Engine Front Drive) vehicle) that generates driving force by transmitting power output from the engine 1 to the front wheels. Alternatively, it may be a four-wheel drive vehicle (4WD (4 wheel drive) vehicle) that generates driving force by transmitting the power output from the engine 1 to the front wheels and the rear wheels, respectively.

  The engine 1 includes, for example, an electronically controlled throttle valve or an electronically controlled fuel injection device, and an airflow sensor that detects the flow rate of intake air. In the example shown in FIG. 2, an electronic throttle valve 3 is provided. Therefore, for example, the output of the engine 1 can be automatically controlled by electrically controlling the operation of the electronic throttle valve 3 based on the detection data of the accelerator opening sensor.

  An automatic transmission 2 that increases or decreases the output torque of the engine 1 and transmits it to the drive wheel side is provided on the output side of the engine 1. The automatic transmission 2 is a general stepped automatic transmission that includes, for example, a planetary gear mechanism, a clutch mechanism, and a brake mechanism. By controlling the operation of the clutch mechanism and the brake mechanism, the automatic transmission 2 2 is configured so that the gear position (or gear ratio) set in 2 can be automatically controlled. The automatic transmission 2 may be a transmission configured to change the transmission ratio of the continuously variable transmission stepwise.

  A controller (ECU) 4 for controlling the output of the engine 1 and the shift operation of the automatic transmission 2 is provided. The controller 4 is an electronic control device mainly composed of a microcomputer, for example. The controller 4 is electrically connected to the engine 1 and the automatic transmission 2 so as to transmit a control command signal. Although FIG. 2 shows an example in which one controller 4 is provided, a plurality of controllers 4 may be provided for each device to be controlled or for each control content.

  The controller 4 is configured to receive detection signals from various sensors in each part of the vehicle Ve, information signals from various in-vehicle devices, and the like. For example, the air flow sensor, the accelerator opening sensor, the brake sensor that detects the amount of depression of the brake pedal, the engine rotation speed sensor 5 that detects the rotation speed of the output shaft of the engine 1, and the rotation speed of the output shaft of the automatic transmission 2 A detection signal from an output rotational speed sensor for detecting the vehicle speed and a vehicle speed sensor for detecting the rotational speed of each wheel to obtain the vehicle speed is input to the controller 4. And it is comprised so that it may calculate using the input data, the data memorize | stored previously, etc., and a control command signal may be output based on the calculation result.

  In the vehicle Ve configured as described above, as described above, a shift shock occurs when the vehicle Ve is on the coast and is downshifted. In particular, if the downshift is performed on the high vehicle speed side, that is, the high rotation side in order to lengthen the fuel cut time, there is a risk that the shift shock will deteriorate. Therefore, the controller 4 performs a downshift in the coast state so as to continue the fuel cut for a long time while suppressing the shift shock. Below, the concrete control content performed by the controller 4 is demonstrated.

  FIG. 1 is a flowchart for explaining an example of the control. The flowchart of this control shows the control when downshifting during the coasting. “Coasting” means a state where the engine 1 is coasting without the engine 1 outputting a driving torque. The “fuel cut” is a cylinder deactivation operation in which combustion in all or a part of the cylinders in the engine 1 is suspended. For example, the fuel cut is a control for stopping fuel supply to the engine during coasting to improve fuel consumption. is there. The determination as to whether or not the vehicle is coasting is made, for example, when the fuel is being cut and the vehicle speed detected by the vehicle speed sensor is decreasing. In addition, “downshift” is a shift that increases the gear ratio, and this downshift can be performed by switching between a pair of clutches on the disengagement side and the engagement side.

  Hereinafter, this flowchart will be specifically described. This flowchart is a diagram for explaining an example of the control, and the routine shown here is repeatedly executed every predetermined short time during coasting. In this embodiment, the engine speed NE is described as a control target. However, when the lockup clutch provided in the torque converter is engaged, the engine speed NE and the input shaft of the automatic transmission 2 are used. Since there is a known correlation with the rotational speed NT of the connected turbine, the turbine rotational speed NT may be used instead of the engine rotational speed NE.

  First, it is determined whether or not the engine speed NE is equal to or less than the fuel cut permission (return) speed + α speed (step S1). The fuel cut permission rotational speed + α rotational speed is a threshold value for operating the fuel cut for a long time (hereinafter, also simply referred to as a threshold value). Specifically, the fuel cut permission rotational speed is the engine speed set to the lowest possible rotational speed that does not lead to engine stall when the fuel cut is stopped and the fuel supply is resumed. The number NE (or the input rotational speed of the automatic transmission 2). Therefore, in this embodiment, in order to operate the fuel cut for a long time, the fuel cut permission rotational speed is set higher by the α rotational speed. Further, the α rotation speed corresponds to a reduction amount of the engine rotation speed NE during a shift, and refers to a rotation speed of about 100 (rpm). Therefore, if the engine speed NE of the vehicle Ve is higher than the fuel cut permission rotational speed + α rotational speed, a negative determination is made in this step S1. If the determination in step S1 is negative, there is no need to perform a shift (downshift), so the routine shown in FIG. 1 is temporarily terminated without any particular control.

  On the other hand, if the engine speed NE is equal to or lower than the fuel cut permission rotational speed + α rotational speed, that is, the rotational speed equal to or lower than the threshold value, if the determination in step S1 is affirmative, the process proceeds to step S2. . In step S2, a torque necessary for stabilizing the engine speed NE is calculated. “Stable engine speed NE” means that a predetermined change rate of the engine speed NE is once determined in order to suppress a shift shock when the engine speed NE decreases during a coast and downshifts. The number of rotations that is within the value. That is, the engine speed NE is approximately constant. Further, in order to stabilize the rotational speed, the friction torque for the engine 1 is discriminated (calculated) by a friction monitor. The friction torque is a torque due to a frictional force or a pumping loss in the engine 1, and can be obtained by measuring in advance for each engine speed. Therefore, in step S2, the measurement value may be read to calculate the friction torque.

  The friction monitor calculates the friction torque and outputs the torque from the engine 1 so as to amplify the torque corresponding to the friction torque. That is, the intake air amount is increased by the electronic throttle valve 3 and idle speed control (ISC: not shown) so that the sum of the friction torque and the engine torque during the downshift becomes 0 (zero), and the fuel is Be injected. That is, torque increase control is performed. That is, in order to suppress the shift shock, the fuel cut control is temporarily interrupted and the torque corresponding to the friction torque is increased. Accordingly, the torque necessary for stabilizing the rotational speed is calculated in step S2, and an instruction to increase or decrease the torque corresponding to the friction torque is given (step S3).

  Next, it is determined whether or not the engine speed NE has been stabilized by increasing or decreasing the torque instructed in step S3 (step S4). As described above, the engine speed NE is stabilized in order to suppress the shift shock. Therefore, if it is determined that the engine speed NE is not stable, this control flow is temporarily terminated, and the process returns to step S2 without any particular shift, and is necessary again to stabilize the engine speed NE. Calculate the torque.

  On the other hand, if the determination in step S4 is affirmative, that is, if it is determined that the engine speed NE is stable, a shift command is issued. That is, the hydraulic pressure for shifting is output (step S5). In other words, the hydraulic pressure of the engagement clutch is output. Then, the hydraulic pressure is output, and when the clutch is completely engaged, the shift is finished (step 6).

  FIG. 3 is a diagram for explaining a time chart showing the behavior when the above-described flowchart is executed. In particular, when the downshift is performed during the coast, the engine speed NE (turbine speed NT), the clutch pressure FIG. 5 is a time chart showing an example of a change in gear change instruction, vehicle acceleration, and torque increase amount (electronic throttle valve 3). FIG. FIG. 3 shows an example of shifting (downshifting) from the fourth speed to the third speed as an example.

  As shown in FIG. 3, at time t1, it is determined that the engine speed NE has dropped below the speed of step S1, ie, the engine speed NE + α speed (threshold), and the intake air amount is reduced by the electronic throttle valve. Will be increased. Further, the fuel injection amount is increased as the air amount increases. That is, a friction torque is calculated by the friction monitor, and torque increase control is started so as to compensate for the friction torque. As a result, the engine speed NE begins to stabilize (time t2). When the engine speed NE starts to stabilize, a gear shift command is issued from the 4th speed to the 3rd speed, and accordingly, the hydraulic pressure applied to the clutch is outputted in a stepwise manner in order to speed up the start of movement of the piston of the clutch. . Therefore, the shift control is started at this point. This shift control is a so-called clutch-to-clutch shift control in which the release-side clutch is released and then the engagement-side clutch is engaged. Further, when the shift control is started, the acceleration of the vehicle becomes larger on the minus side.

  Further, when the rate of change of the engine speed NE falls within a predetermined value, that is, when the engine speed NE is stabilized to some extent (at time t3), the increase control by the electronic throttle valve 3, that is, the torque increase control is performed. finish. This torque increase control will be described more specifically. As shown in FIG. 4, the engine torque due to combustion starts to increase at the time t1. That is, torque is output from the engine 1 when it is determined that the engine speed NE has become equal to or less than the threshold value in step S1 of the flowchart of FIG. The behavior of the engine torque is indicated by a broken line. On the other hand, the friction torque for the engine 1 is also increased at a constant rate of change. The behavior of the friction torque is indicated by a one-dot chain line. Therefore, the engine speed NE is stabilized by amplifying the torque corresponding to the friction torque by the engine 1. That is, control is performed so that the sum of the engine torque and the friction torque becomes 0 (zero). The behaviors of the engine torque and the friction torque are shown by solid lines.

  As described above, the engine speed NE or the turbine speed NT is stabilized, a shift command is issued, and the shift control is performed, so that the engine speed NE increases. Along with this, the hydraulic pressure of the engagement clutch also increases and the clutch starts to be engaged. When the clutch is completely engaged, the shift is finished (at time t4). Note that the fuel cut control that has been temporarily suspended when the engine speed NE returns to a speed equal to or higher than the threshold after the engine speed NE has stabilized is resumed.

  Thus, in order to suppress the shift shock, the fuel cut is temporarily interrupted, and the downshift is executed in a state where the engine speed NE is stabilized by performing the torque increase control corresponding to the friction torque. As a result, the shift shock can be suppressed. In addition, by setting the fuel cut permission rotational speed as high as the α rotational speed, it is possible to control based on the threshold value, so that the fuel cut time can be lengthened and the total fuel consumption can be improved. be able to. That is, by performing torque increase control so that the sum of the torque output from the engine 1 and the friction torque becomes 0 (zero) so as to compensate for the friction torque, a shift (down) is performed after the engine speed NE is stabilized. Shift) can be started. Therefore, shift shock can be suppressed and fuel consumption can be improved.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications are made without departing from the spirit of the present invention. For example, in the above-described example, the shift from the fourth speed to the third speed (downshift) is shown as an example, but the present invention may be applied to other shifts (downshift) such as the third speed to the second speed.

  DESCRIPTION OF SYMBOLS 1 ... Engine (ENG), 2 ... Automatic transmission (AT), 3 ... Electronic throttle valve, 4 ... Controller (ECU), 5 ... Engine speed sensor, Ve ... Vehicle, NE ... Engine speed, NT ... Turbine speed number.

Claims (1)

When a vehicle equipped with an engine and a stepped automatic transmission connected to the output side of the engine is coasting, the fuel for the engine when the engine speed is equal to or higher than the fuel cut permission speed Of the vehicle configured to perform a downshift with the automatic transmission so as to maintain the engine speed at a speed equal to or higher than the fuel cut permission speed during the inertia traveling. In the control device,
A controller for controlling fuel supply of the engine and shifting of the automatic transmission;
The controller is configured to supply fuel to the engine when the rotational speed of the engine decreases to a predetermined rotational speed that is equal to or higher than the fuel-cut permission rotational speed during the inertial traveling in which fuel supply to the engine is stopped. Restart supply and drive the engine,
The engine is driven so that the engine outputs a torque corresponding to the friction torque of the engine in the fuel cut state so that the rate of change of the engine speed falls within a predetermined value. And
When the rate of change of the engine speed is within the predetermined value due to the driving of the engine, the downshift is executed,
The vehicle control apparatus is configured to stop the fuel supply to the engine again after the engine speed increases due to the downshift.

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