JP2015031323A - Vehicle transmission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle transmission control device which curbs a reduction in durability of a driving system.SOLUTION: An electronic control device 50: calculates inertial torque T applied to a predetermined area of a driving system when a vehicle 10 is in braking operation on the basis of deceleration of the vehicle for each of a plurality of shift stages; and curbs downshifting to a shift stage where the calculated inertial torque T exceeds a predetermine threshold. Thus, the electronic control device 50 can limit the inertial torque applied to the driving system within a level that does not affect durability of the driving system and thereby suitably protecting the same. That is, the control device 50 can curb a reduction in the durability of the driving system.

Description

  The present invention relates to a vehicle shift control device that controls the shift of an automatic transmission for a vehicle, and more particularly to an improvement for suppressing a decrease in durability of a drive system.

  2. Description of the Related Art A vehicle shift control device that performs shift control of an automatic transmission that selectively establishes a plurality of shift speeds is known. In such a vehicle shift control device, a technique for realizing stable shift control has been proposed. For example, a shift control device for an automatic transmission described in Patent Document 1 is an example. According to this technology, the shift control of the automatic transmission is performed in consideration of the vehicle acceleration. For example, when a road surface condition that is likely to slip is determined based on the vehicle acceleration, the gear position is set to a relatively high gear position. It is said that stable running performance can be obtained by control such as shifting to suppress slip.

Japanese Patent Laid-Open No. 3-24360 JP-A-9-303548

  However, in the conventional technique, for example, when the wheels are suddenly locked, the inertia torque on the engine side is amplified by the automatic transmission and input to the drive system, which may affect the durability of the drive system. was there. Such a problem has been newly found in the process of continual research by the present inventors with the intention of improving the durability of a vehicle equipped with an automatic transmission.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a vehicle transmission control device that suppresses a decrease in durability of a drive system.

  In order to achieve such an object, the gist of the first aspect of the present invention is that a vehicle automatic transmission that selectively establishes a plurality of shift speeds in a predetermined part of a drive system when the vehicle is being braked. Inertia torque loaded on the vehicle is calculated based on vehicle deceleration for each of the plurality of shift speeds, and downshift to a shift speed at which the calculated inertia torque exceeds a specified threshold is suppressed. It is.

  Thus, according to the first aspect of the present invention, when the vehicle is being braked, the inertia torque applied to the predetermined part of the drive system is calculated based on the vehicle deceleration for each of the plurality of shift speeds. The inertia torque applied to the drive system is suppressed to a magnitude that does not affect the durability, because the inertia torque to be applied is to suppress downshifting to a gear position that exceeds a prescribed threshold. The drive system can be suitably protected. That is, it is possible to provide a vehicle transmission control device that suppresses a decrease in durability of the drive system.

  In the first invention, preferably, the threshold value is determined based on an inertia torque applied to a predetermined portion of the drive system when a wheel is locked for each of the plurality of shift stages. In this way, it is possible to suitably suppress a decrease in the durability of the drive system due to the engine inertia torque when the wheel is locked, where a relatively large inertia torque is input to the drive system.

  In the first aspect of the present invention, preferably, the vehicle is a four-wheel drive vehicle including a transfer device that distributes a driving force output from the engine to front wheels or rear wheels, and inertia applied to the drive system. The torque is calculated in consideration of the inertia torque input to the transfer device. In this way, it is possible to more suitably suppress a reduction in the durability of the drive system by taking into account the inertia torque input to the drive system via the transfer device.

1 is a skeleton diagram illustrating a configuration of a vehicle to which the present invention is preferably applied. It is a functional block diagram explaining the principal part of the control function with which the electronic control apparatus in the vehicle of FIG. 1 was equipped. 2 is a flowchart for explaining a main part of an example of downshift suppression control by an electronic control unit in the vehicle of FIG. 1.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a skeleton diagram illustrating a configuration of a front and rear wheel drive vehicle 10 (hereinafter simply referred to as a vehicle 10) based on a front engine front wheel drive (FF) to which the present invention is preferably applied. As shown in FIG. 1, the vehicle 10 of the present embodiment includes an engine 12, a torque converter 14, an automatic transmission 16, a front wheel side drive shaft 18, a front wheel side differential device 20, and a pair of left and right front wheels. Axle 22, left and right pair of front wheels 24, transfer device 26, rear wheel side drive shaft 28, rear wheel side differential device 30, left and right pair of rear wheel axles 32, and right and left pair of rear wheels 34, a hydraulic control circuit 40, and an electronic control device 50. Hereinafter, when the front wheel 24 and the rear wheel 34 are not particularly distinguished, they are simply referred to as wheels 24 and 34.

  In the vehicle 10, torque (driving force) generated by the engine 12 that is a driving force source is the torque converter 14, the automatic transmission 16, the front wheel side drive shaft 18, the front wheel side differential device 20, and the left and right While being transmitted to the pair of left and right front wheels 24 via a pair of front wheel axles 22, the torque converter 14, automatic transmission 16, transfer device 26, rear wheel side drive shaft 28, rear wheel side differential device 30. , And a pair of left and right rear wheel axles 32. That is, the vehicle 10 of this embodiment distributes the torque generated by the engine 12 to the front wheels 24 as main driving wheels and the rear wheels 34 as auxiliary driving wheels (secondary driving wheels) according to the running state. 1 is an example of a drive system of a torque split type four-wheel drive vehicle. Alternatively, it may be a four-wheel drive vehicle in which the front wheels 24 are auxiliary drive wheels and the rear wheels 34 are main drive wheels. The present invention is also suitably applied to a two-wheel drive vehicle in which one of the front wheel 24 and the rear wheel 34 is a drive wheel.

  The automatic transmission 16 is a stepped automatic transmission mechanism that selectively establishes a plurality of shift stages. For example, a plurality of gear stages (shift stages) each including a plurality of hydraulic friction engagement devices, each corresponding to a predetermined gear ratio γ, are selectively selected according to the hydraulic pressure supplied from the hydraulic control circuit 40. It is a stepped automatic transmission mechanism (automatic transmission) that can be established. Preferably, in the automatic transmission 16, any one of a plurality of predetermined (for example, first to fourth speed) forward shift stages, reverse shift stages, and neutrals is selectively established. The speed conversion according to each gear ratio γ is performed.

  The transfer device 26 distributes a part of the torque output from the automatic transmission 16 to the rear wheel 34 side. That is, a part of the torque output from the automatic transmission 16 is transmitted to the rear wheel side drive shaft 28, and the left and right 1 are transmitted via the rear wheel side differential 30 and the left and right pair of rear wheel axles 32. Transmission to the rear wheels 34 of the pair. The transfer device 26 may be an electronically controlled coupling that controls the torque distribution amount (distribution ratio) to the rear wheel 34 by electronic control by the electronic control device 50 or the like, or a viscous coupling or the like. The rotational differential response type torque transmission device may be used.

  The electronic control unit 50 includes a CPU, a ROM, a RAM, an input / output interface, and the like. The CPU 50 uses the temporary storage function of the RAM to execute signal processing according to a program stored in advance in the ROM. It is a computer. The electronic control unit 50 controls the hydraulic pressure supplied from the hydraulic control circuit 40 to the automatic transmission 16 by controlling commands supplied to various electromagnetic control valves provided in the hydraulic control circuit 40, for example. And shift control for selectively establishing a plurality of shift stages in the automatic transmission 16 is performed. That is, in the present embodiment, the electronic control device 50 corresponds to a vehicle shift control device.

The vehicle 10 is provided with sensors for detecting various relational values related to the driving thereof. For example, a brake sensor 52 that detects a brake operation such as turning on / off of a foot brake pedal, a depression amount of the foot brake pedal, a vehicle speed sensor 54 that detects a vehicle speed V corresponding to the rotational speed of the wheels 24, 34, and the vehicle 10 an acceleration sensor 56 for detecting a longitudinal acceleration (longitudinal G), and the rotational speed N _E various sensors such as an engine rotational speed sensor 58 for detecting are provided to the engine 12, the brake operation from the respective sensor A signal indicating the vehicle speed V, a signal indicating the acceleration G in the longitudinal direction of the vehicle, a signal indicating the engine rotational speed _NE, and the like are supplied to the electronic control unit 50. A wheel speed sensor that detects the wheel speed ω of each of the four front and rear wheels 24, 34 may be provided, and a signal representing the wheel speed ω of each wheel 24, 34 may be supplied to the electronic control unit 50. Among the wheel speeds ω detected corresponding to the pair of left and right front wheels 24 and rear wheels 34, the vehicle speed corresponding to the wheel speed ω corresponding to the slowest wheel is detected as the vehicle speed V. It may be.

FIG. 2 is a functional block diagram for explaining a main part of the control function provided in the electronic control unit 50. The shift control unit 80 shown in FIG. 2 performs shift control of the automatic transmission 16. For example, based on driving force-related values such as the vehicle speed V and the throttle valve opening θ _TH detected by the vehicle speed sensor 54 from a predetermined shift map, the gear position (speed ratio γ) to be established at that time point And the engagement state of the hydraulic friction engagement device provided in the automatic transmission 16 is controlled so that the gear position is established. That is, a control signal for controlling various electromagnetic control valves provided in the hydraulic control circuit 40 is output in order to establish the determined shift speed in the automatic transmission 16.

  The brake determining unit 82 determines whether or not the vehicle 10 is braking. Preferably, based on a signal representing a brake operation detected by the brake sensor 52, it is determined whether or not the vehicle 10 is being braked. For example, when the brake sensor 52 detects that the brake operation is being performed, it is determined that the vehicle 10 is being braked. When the depression amount of the foot brake pedal detected by the brake sensor 52 is not less than a specified value, it is determined that the vehicle 10 is being braked. The during-braking determination unit 82 preferably determines whether the vehicle 10 is being braked based on the deceleration (acceleration in the front-rear direction) of the vehicle 10. For example, when the deceleration of the vehicle 10 detected by the acceleration sensor 56 is a specified value or more (negative acceleration is a predetermined value or more), it is determined that the vehicle 10 is being braked. When the time change rate of the vehicle speed V detected by the vehicle speed sensor 54 is a negative value and the value is less than a predetermined value, it is determined that the vehicle 10 is being braked.

  The inertia torque calculation unit 84 is configured to perform inertia torque (inertia torque) applied to a predetermined part of the drive system in the vehicle 10 when the determination by the determination unit 82 during braking is affirmed, that is, when the vehicle 10 is braking. ) Is calculated. The predetermined portion is, for example, a hardware dynamic weakest portion on a drive system (drive train) in the vehicle 10 and is a portion specified in advance by design or experiment. For example, the inertia torque applied to the predetermined portion corresponds to the inertia torque (engine inertia torque) of the engine 12 or the inertia torque input from the wheels 24 and 34 when the vehicle 10 is braked. This is the inertia torque that can be applied to the site. That is, the inertia torque loaded on the predetermined portion is preferably input from the engine 12 via the automatic transmission 16 and input from the rear wheel 34 via the transfer device 26. The calculated inertia torque (inertia torque loaded on the transfer device 26) is taken into consideration.

  The inertia torque calculator 84 calculates an inertia torque that can be applied to the predetermined portion for each of the plurality of shift speeds that are selectively established in the automatic transmission 16 (that is, for each shift speed). The inertia torque input from the engine 12 via the automatic transmission 16 differs depending on the gear position (speed ratio γ) established in the automatic transmission 16. Therefore, the inertia torque calculation unit 84 calculates the inertia torque that can be applied to the predetermined portion when the vehicle 10 is braking, for each of the plurality of shift speeds. Preferably, the inertia torque applied to the predetermined portion is calculated based on at least the deceleration (negative acceleration in the front-rear direction) of the vehicle 10 for each of the plurality of shift speeds. The deceleration of the vehicle 10 preferably corresponds to the time change rate of the vehicle speed V, but may correspond to the time change rate of the rotational angular acceleration ω of the wheels 24 and 34. . For example, the inertia torque calculation unit 84 may generate torque Tx flowing from the engine 12 side to the front wheel side differential (front differential) 20 and the front wheels from the left and right rear wheels 34 for each of the plurality of shift speeds. The torque Tr flowing to the side differential device 20 is calculated, and the sum of the calculated torques Tx and Tr (= Tx + Tr) is calculated as the inertia torque T loaded on the predetermined portion.

The torque Tx flowing from the engine 12 side to the front wheel side differential 20 is, for example, engine inertia (inertia torque of the engine 12), engine angular acceleration (angular acceleration of the engine 12 output shaft), torque converter ratio, transmission gear ratio, and the like. From the (gear ratio of the automatic transmission 16), the transfer gear ratio (gear ratio of the transfer device 26), etc., it is calculated as shown in the following equation (1). The engine inertia, for example, is calculated based on the engine rotational speed N _E detected by the engine rotational speed sensor 58. The engine angular acceleration, for example, is calculated based on the time variation of the engine rotational speed N _E detected by the engine rotational speed sensor 58. The torque Tr flowing from the left and right rear wheels 34 to the front wheel side differential 20 is, for example, tire inertia (inertia torque of the left and right rear wheels 34), tire angular acceleration (angular acceleration of the rear wheels 34), vehicle weight. From the tire radius (the radius of the rear wheel 34), the differential ratio (the differential ratio of the rear wheel side differential device 30), etc., it is calculated as shown in the following equation (2). The tire inertia is calculated based on the vehicle speed V detected by the vehicle speed sensor 54, for example. The tire angular acceleration is calculated based on, for example, a time change of the vehicle speed V calculated by the vehicle speed sensor 54. The tire angular acceleration includes a wheel speed sensor that individually detects the wheel speed of each of the wheels 24 and 34. Is calculated based on the wheel speed detected by each wheel speed sensor.

  As described above, the inertia torque calculation unit 84 is preferably configured so that, when the vehicle 10 is being braked, the inertia torque (inner gear torque for each gear stage) that can be applied to the predetermined portion for each of the plurality of shift speeds. ) T is calculated based on various vehicle specifications such as vehicle weight and tire diameter, and deceleration of the vehicle 10 corresponding to angular acceleration of the wheels 24 and 34. The inertia torque calculation unit 84 does not necessarily calculate the inertia torques Tx and Tr based on the equations (1) and (2). Various vehicle specifications and the vehicle are determined from a predetermined map or the like. Based on the deceleration of 10 or the like, the inertia torque Tx, Tr, or the inertia torque T that can be applied to the predetermined portion may be derived.

  The lower limit shift speed determination unit 86 determines the shift speed x corresponding to the maximum speed ratio (gear ratio) γ established in the automatic transmission 16 based on the inertia torque T calculated by the inertia torque calculation unit 84. judge. That is, the gear position (that is, the lowest gear stage) x corresponding to the maximum gear ratio γ in the range where the inertia torque T calculated by the inertia torque calculator 84 does not exceed the prescribed threshold value is determined. Preferably, the inertia torque T calculated by the inertia torque calculator 84 has a maximum speed ratio γ in a range that does not affect the durability of the predetermined portion (for example, a range in which the predetermined portion is not damaged). The corresponding gear stage x is determined. That is, the threshold value is determined, for example, by experimentally obtaining in advance based on the durability of the predetermined part. Preferably, each of the plurality of shift speeds is predetermined based on an inertia torque applied to the predetermined portion when the wheels 24 and 34 are locked. In other words, the lower limit speed determining unit 86 preferably has the inertia torque T calculated by the inertia torque calculating unit 84 when the wheels 24 and 34 are locked, so that the durability of the predetermined portion is determined. The shift speed x corresponding to the maximum speed ratio γ in a range not affecting the performance is determined.

  As shown in FIG. 2, the shift control unit 80 includes a downshift suppression control unit 88. The downshift suppression control unit 88 performs control to suppress the range of the shift stage established in the automatic transmission 16 based on the shift stage x determined by the lower limit shift stage determination unit 86. That is, a downshift to a gear position having a gear ratio γ larger than the gear speed x determined by the lower limit gear speed determining unit 86 is suppressed. For example, a downshift to a gear stage having a gear ratio γ larger than the gear stage x determined by the lower limit gear stage determining unit 86 is prohibited. In other words, the shift stage x determined by the lower limit shift stage determination unit 86 is set to the lower limit shift stage (the shift stage having the largest speed ratio γ), and a shift that selectively establishes a plurality of shift stages that are greater than or equal to the shift stage x. Take control.

  FIG. 3 is a flowchart for explaining a main part of an example of the downshift suppression control of the present embodiment by the electronic control unit 50, and is repeatedly executed at a predetermined cycle.

First, in step (hereinafter, step is omitted) S1, whether or not the vehicle 10 is being braked is determined based on a signal indicating a brake operation detected by the brake sensor 52 or the like. If the determination at S1 is negative, the routine is terminated accordingly. If the determination at S1 is affirmative, the engine speed N detected by the engine speed sensor 58 is detected at S2. Based on _{E and the} like, an engine inertia torque that is an inertia torque of the engine 12 is calculated. Next, in S3, engine inertia torques Tx1 to Txn obtained by multiplying the engine inertia torque calculated in S2 by the gear ratios (gear ratios) γ1 to γn of the respective shift stages 1 to n in the automatic transmission 16 are obtained. Calculated. Next, in S4, a rear wheel side inertia torque Tr input to the drive system from the rear wheel 34 side via the transfer device 26 is calculated. The processes of S2 and S3 and the process of S4 may be executed in parallel. Next, in S5, the inertia that can be applied to a predetermined part of the drive system for each shift stage from the engine-side inertia torque Tx1 to Txn calculated in S3 and the rear wheel-side inertia torque Tr calculated in S4. Torque T (= Tx + Tr) is calculated. Next, in S6, a shift stage (shift stage) x corresponding to the maximum speed ratio γ is calculated (determined) in a range where the inertia torque T calculated in S5 is equal to or less than a predetermined threshold value. Next, in S7, the shift stage x calculated in S6 is set as the lower limit shift stage (the shift stage having the largest speed ratio γ), and downshifting to a gear stage having a larger speed ratio γ than the speed stage x during traveling is performed. Is suppressed, this routine is terminated.

  As described above, according to this embodiment, when the vehicle 10 is being braked, the inertia torque T that can be applied to a predetermined part of the drive system is set to the deceleration of the vehicle 10 for each of the plurality of shift speeds. Since the calculated inertia torque T suppresses the downshift to the gear position where the calculated inertia torque exceeds the specified threshold, the inertia torque applied to the drive system is large enough not to affect the durability. Thus, the drive system can be suitably protected. Furthermore, the maximum engine brake can be secured while suppressing the influence on the durability of the predetermined portion. That is, it is possible to provide the electronic control device 50 as a vehicle transmission control device that suppresses a decrease in durability of the drive system.

  The threshold is determined based on an inertia torque applied to a predetermined part of the drive system when the wheels 24 and 34 are locked for each of the plurality of shift speeds. When the wheels 24 and 34 to which a large inertia torque is input are locked, it is possible to suitably suppress a decrease in durability of the drive system due to the engine inertia torque.

  The vehicle 10 is a four-wheel drive vehicle including a transfer device 26 that distributes the driving force output from the engine 12 to the front wheels 24 to the rear wheels 34. The inertia torque T applied to the drive system is the Since the torque is calculated in consideration of the inertia torque Tr input to the transfer device 26, the durability of the drive system is reduced by adding the inertia torque Tr input to the drive system via the transfer device 26. Can be more suitably suppressed.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention. Is.

  10: front and rear wheel drive vehicle, 16: automatic transmission, 50: electronic control device (vehicle speed change control device)

Claims (1)

In an automatic transmission for a vehicle that selectively establishes a plurality of shift speeds,
When the vehicle is being braked, inertia torque applied to a predetermined part of the drive system is calculated based on vehicle deceleration for each of the plurality of shift speeds, and the calculated inertia torque exceeds a specified threshold. A shift control apparatus for a vehicle, which suppresses downshifting to a vehicle.

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