Control device for a vehicle equipped with a continuously variable transmission

Abstract

Control device (14) for a vehicle equipped with a continuously variable transmission (26), comprising an acceleration request detection section (74) configured to determine, based on an actual actuation amount (accpfb) of a vehicle acceleration element (54) by a user of the vehicle, whether the user requests acceleration of the vehicle, a first setting section (76) for a limited accelerator pedal actuation amount configured to set a limited actuation amount (accpfctrl) of the vehicle acceleration element such that the limited amount gradually increases with an increase in a vehicle speed (spd) when the acceleration request detection section has determined that the user of the vehicle requests acceleration of the vehicle, and a shift control section (102) configuredthat this controls a speed ratio of the continuously variable transmission based on the limited actuation amount (accpfctrl) of the vehicle acceleration element, wherein the control device further comprises: , a second setting section (80) for a limited accelerator pedal actuation amount, which is configured such that it determines the limited actuation amount (accpfctrl) of the vehicle acceleration element starting from a value (accpfctrl (i-1) ) immediately before a moment of determination of a rapid release actuation of the vehicle acceleration element (54) at a lower rate than a decrease rate of the actual actuation amount (accpfb) of the vehicle acceleration element (54) after the moment of determination of the rapid release actuation, and an upper limit stop processing section (82) configured to limit the limited actuation amount (accpfctrl) of the vehicle acceleration element after a moment of determination that the vehicle user requests vehicle acceleration, such that the limited actuation amount is not greater than the actual actuation amount (accpfb), wherein The second adjustment section (80) for a limited accelerator pedal actuation amount comprises: a lower limit adjustment section (83) configured to provide a reduced accelerator pedal actuation amount (accpfdec) after the moment of rapid release actuation, corresponding to a lower limit of the limited actuation amount (accpfctrl) of the vehicle acceleration element, in each control cycle by subtracting a predetermined reduction value (Δaccpfdec) from a reduced accelerator pedal actuation amount value (accpfdec). (i-1)) calculated repeatedly in a final control cycle; and a lower limit stop processing section (84) configured to adjust the limited actuation amount (accpfctrl) of the vehicle acceleration element after the moment of rapid release actuation such that the limited actuation amount is not lower than the attenuated accelerator pedal actuation amount (accpfdec).

Description

Field of the invention

[0001] The present invention generally relates to a control device for a vehicle provided with a continuously variable transmission, and more particularly to a technology for improving an acceleration performance of the vehicle upon a vehicle acceleration operation of a vehicle acceleration member following the release operation thereof. Background of the invention

[0002] A vehicle equipped with a mechanical-type or electric-type continuously variable transmission is known. Examples of the mechanical-type continuously variable transmission include: a belt-and-pulley-type continuously variable transmission, in which a pair of variable-diameter pulleys whose effective diameters are continuously variable are connected to each other via a transmission belt; and a traction-type continuously variable transmission, in which a disk is supported between two annular U-grooves formed on opposite surfaces of a pair of cones, so that the disk is rotatable about an axis that is rotatable in a plane including rotation axes of the cones.An example of the electric type continuously variable transmission has a differential gear device including a first rotating element connected to an engine, a second rotating element connected to an electric motor for generating a reaction force according to an output of the engine, and a third rotating element outputting a vehicle driving force.

[0003] In the vehicle provided with such a continuously variable transmission as described above, the output torque of a vehicle drive power source and the speed ratio of the continuously variable transmission are controlled such that the operating state of the vehicle drive power source follows a line of highest fuel economy, so that the vehicle can have not only a high degree of fuel economy but also a high degree of drivability.However, controlling the output torque of the vehicle drive power source and the speed ratio of the continuously variable transmission to ensure the high fuel economy level tends to limit a target vehicle drive force and the operating speed of the vehicle drive power source with respect to an actual operation amount of a vehicle acceleration element (e.g., an accelerator pedal) by a user of the vehicle to accelerate the vehicle, resulting in a problem of insufficient acceleration level of the vehicle perceived by the vehicle user.

[0004] In view of the above-described problem, it has been proposed to temporarily increase the target vehicle driving force and increase the target rotational speed of an input shaft of the continuously variable transmission, that is, the operating rotational speed of the vehicle driving power source, with respect to an actual operation amount of the vehicle acceleration element by the vehicle user to accelerate the vehicle, in order to ensure a sufficient degree of acceleration of the vehicle perceived by the vehicle user. For example, JP 2006-51842 A proposes a control device configured to control the vehicle equipped with a continuously variable transmission as described above.However, this control technology to improve the acceleration performance of the vehicle as described above suffers from another problem of generating an initial acceleration shock upon operation of the vehicle acceleration element to accelerate the vehicle.

[0005] On the other hand, JP 2006 - 118 388 A proposes a control technology for mitigating initial acceleration and deceleration shocks of the vehicle upon operations of the vehicle acceleration element to accelerate and decelerate the vehicle by performing a smoothing operation with a second-order lag filter in the form of a filter section at a predetermined smoothing ratio with respect to initial rates of increase and decrease of the actual operation amount of the vehicle acceleration element by the vehicle user to accelerate and decelerate the vehicle.

[0006] Furthermore, US 2009 / 0 043 468 A1 discloses a control system for a vehicle with a continuously variable transmission. A controller, upon assessing an acceleration request, sets a target driving force that is higher than the target driving force under normal calculation during normal operation of an accelerator pedal, and sets a target engine speed for acceleration that is higher than the target engine speed under normal operation and increases with an increase in vehicle speed by a predetermined gradient. The gear ratio of the continuously variable transmission and the engine output torque are controlled so that the set target driving force is achieved and an input shaft speed of the continuously variable transmission matches the target engine speed for the set acceleration. Summary of the inventionTechnical problem

[0007] In fact, the vehicle acceleration element can be actuated quickly or rapidly to accelerate the vehicle to its fully released position immediately after a rapid release of the vehicle acceleration element. In this case, the vehicle user expects rapid or prompt acceleration of the vehicle.However, in the prior art control technology, even when the vehicle acceleration element is rapidly operated to accelerate the vehicle to its fully released position immediately after the rapid release operation of the vehicle acceleration element, the rates of increase and decrease of the actual operation amount of the vehicle acceleration element are smoothed, resulting in a significant difference between the actual acceleration degree of the vehicle and the degree expected by the vehicle user, and a risk of delay in the vehicle acceleration perceived by the vehicle user.

[0008] The present invention was made in view of the prior art described above. It is therefore an object of the present invention to provide a control device for a vehicle equipped with a continuously variable transmission, wherein the control device prevents a difference between the actual acceleration level of the vehicle and the level expected by the vehicle user, and a delay in the vehicle acceleration perceived by the vehicle user upon rapid actuation of a vehicle acceleration element to accelerate the vehicle immediately after its rapid release. Solution to the problem

[0009] The above object is achieved by the subject matter of claim 1. Advantageous developments of the invention are the subject matter of the subsequent dependent claims.

[0010] An illustrative aspect of the present disclosure relates to a control device for a vehicle provided with a continuously variable transmission, comprising an acceleration request determination section configured to determine whether a user of the vehicle requests acceleration of the vehicle based on an actual operation amount of a vehicle acceleration element by a user, that is, an accelerator pedal, a first accelerator pedal restriction operation amount setting section configured to set a restriction operation amount of the vehicle acceleration element such that the restriction amount gradually increases with an increase in a traveling speed of the vehicle when the acceleration request determination section has determined that the user of the vehicle requests acceleration of the vehicle, and a shift control section,which is configured to control a speed ratio of the continuously variable transmission based on the restricted operation amount of the vehicle acceleration element, wherein the control device further comprises a second restricted accelerator operation amount setting section which is configured to decrease the restricted operation amount of the vehicle acceleration element from a value immediately before a moment of detection of a quick release operation of the vehicle acceleration element at a lower rate than a decrease rate of the actual operation amount of the vehicle acceleration element after the moment of detection of the quick release operation, and an upper limit stop processing section which is configured to adjust the restricted operation amount of the vehicle acceleration element after a moment of detectionthat the user of the vehicle requests the acceleration of the vehicle, so that the limited amount of operation is not greater than the actual amount of operation. Advantageous effects of the invention

[0011] In the control device of the present invention described above, the second accelerator pedal operation restriction amount setting section is configured to decrease the restriction amount of operation of the vehicle acceleration element from the value immediately before the moment of detecting the quick release operation at a lower rate than the decrease rate of the actual operation amount of the vehicle acceleration element after the moment of detecting the quick release operation, and the upper limit stop processing section is configured to restrict the restriction amount of operation of the vehicle acceleration element after the moment of detecting that the user of the vehicle requests the acceleration of the vehicle so that the restriction amount of operation is not greater than the actual operation amount.Accordingly, the speed ratio of the continuously variable transmission is controlled based on the restricted accelerator pedal operation amount, the restriction of which is canceled by a rapid increase in the actual accelerator pedal operation amount following the rapid release operation of the vehicle acceleration element.Therefore, the speed ratio of the continuously variable transmission is controlled based on the restricted accelerator operation amount, which rapidly increases along with the rapid increase in the actual accelerator operation amount until the actual accelerator operation amount exceeds the restricted accelerator operation amount set as the lower limit due to the rapid increase in the actual accelerator operation amount upon the vehicle acceleration operation of the vehicle accelerator immediately after the rapid release operation, so that the vehicle driving force is rapidly increased after the vehicle acceleration operation of the vehicle accelerator. That is, the engine torque is rapidly increased after the rapid vehicle acceleration operation of the vehicle accelerator, and a risk of deceleration of the vehicle acceleration, which is perceived by the vehicle user, is reduced.

[0012] In a preferred form of the present invention, the rate of decrease of the restricted operation amount of the vehicle acceleration element from the value immediately before the quick release operation is set as a function of a traveling speed or a weight of the vehicle or a gradient of a road surface on which the vehicle is traveling, to decrease with an increase in the traveling speed or the weight of the vehicle or the gradient of the road surface. Accordingly, the rate of decrease of the restricted operation amount of the vehicle acceleration element is set to decrease with the increase in the traveling speed or the weight or the gradient of the road surface or the road surface gradient.Therefore, at a time when the restriction of the restricted operation amount of the vehicle acceleration element is canceled to a value not greater than the actual operation amount due to a rapid vehicle acceleration operation of the vehicle acceleration element following its rapid release operation, the restricted accelerator pedal operation amount is greater than the actual operation amount by an amount that increases with the increase in the vehicle traveling speed, weight, or road surface gradient. Accordingly, the risk of a delay in the vehicle acceleration perceived by the vehicle user is effectively reduced.

[0013] In another preferred form of the invention, the control device receives an output signal of an accelerator pedal operation amount sensor for detecting an actual operation amount of an accelerator pedal provided as the vehicle acceleration element. Short description of the figures Fig. 1 is a schematic view showing an arrangement of a vehicle to be controlled by a control device according to the present invention; Fig. 2 is a functional block diagram showing main control sections of a Fig. 1; Fig. 3 is a time chart showing an increase in a restricted accelerator operation amount (shown with a solid line) compared to a change in an actual accelerator operation amount (shown with a broken line) for explaining a function of a first restricted accelerator operation amount setting section of the embodiment shown in Fig. 2 for setting the restricted accelerator pedal operation amount in response to an operation of an accelerator pedal to accelerate the vehicle; Fig. 4 is a time chart indicating a machine operating speed (shown with a solid line) which is determined based on the Fig. 3, compared to an engine operating speed (shown with a broken line) which is to be controlled based on the actual accelerator pedal operation amount, which is also specified in Fig. 3 is specified; Fig. 5 is a time chart indicating a vehicle running speed (shown with a solid line) determined according to the Fig. 3, compared to a vehicle running speed (shown with a broken line) which is to be created according to the actual accelerator pedal operation amount, which is also specified in Fig. 3 is specified; Fig. 6 is a time chart showing changes in the restricted accelerator operation amount and a softened accelerator operation amount respectively determined by the first restricted accelerator operation amount setting section and a second restricted accelerator operation amount setting section as shown in Fig. 2, after a quick release of the accelerator pedal, compared to the actual accelerator pedal operation amount; Fig. 7 is a time chart showing a change in the restricted accelerator operation amount determined by the Fig. 2, and the actual accelerator pedal operation amount after the quick release operation of the accelerator pedal; Fig. Figure 8 is a flow chart showing an essential part of a process carried out by the Fig. 1 illustrates the main control routine executed by the electronic control device shown in FIG. 1 according to an embodiment of this invention; Fig. 9 is a flowchart showing an essential part of a process executed by the electronic control device during execution of the main control routine of Fig. 8 executed subroutine; and Fig. 10 is a flowchart corresponding to that of Fig. 9, which illustrates an essential part of a subroutine executed by the electronic control device according to another embodiment of this invention. Detailed description of preferred embodiments

[0014] Referring to the drawings, preferred embodiments of the present invention are described in detail. First embodiment

[0015] With reference first to the schematic view of Fig. 1, which shows main parts of a vehicle to be controlled by a control device according to the present invention, the vehicle includes an internal combustion engine 10, a power transmission system 12, and an electronic control device 14 serving as the control device according to the invention. The power transmission system 12 is provided with a transmission 16 connected to the engine 10 and a pair of axles 18 rotated by the engine 10 via the transmission 16. The pair of axles 18 are respectively connected to a pair of drive wheels 20, so that vehicle driving power generated by the engine 10 is transmitted to the drive wheels 20.

[0016] The transmission 16 includes a torque converter 22, a forward / reverse switching device 24, a continuously variable transmission 26, and a final speed reduction device 28 (in the form of a differential gear device). The torque converter 22 has a damper provided to damp a variation in torque or rotational motion received from the engine 10 and to transmit the thus smoothed torque or rotational motion to the forward / reverse switching device 24. The continuously variable transmission 26 has an input shaft 29 and an output shaft 30, and is configured to continuously change its speed ratio γ (= Nin / Nout), which corresponds to a ratio of a speed Nin of the input shaft 29 to a speed Nout of the output shaft 30.

[0017] In the present embodiment, the continuously variable transmission 26 is a belt-and-pulley type continuously variable transmission having a pair of variable-diameter pulleys 36 and 38 and a transmission belt 40 connecting these pulleys 36 and 38. The pulleys 36 and 38 are mounted on the respective input and output shafts 29 and 30, which are arranged parallel to each other, so that the effective diameters of the pulleys 36 and 38 are variable by respective hydraulic actuators 32 and 34. The speed ratio γ of the continuously variable transmission 26 is changed by controlling the hydraulic actuators 32 and 38 to change the effective diameters of the pulleys 36 and 38 in the opposite directions to each other.

[0018] As in Fig. 1, the electronic control device 14 is configured to receive various input signals, such as an output signal from a shift position sensor 44 indicating a currently selected shift position PSH of a shift lever 42; an output signal from an ignition switch 46 indicating an on / off state of an ignition key; an output signal from a throttle valve opening angle sensor 52 indicating an opening angle θth (%) of a throttle valve 50 operated by a throttle actuator 48; an output signal from an accelerator pedal operation amount sensor 56 indicating an operation amount pap (%) of a vehicle acceleration element in the form of an accelerator pedal 54, that is, indicating an engine output required by a user of the vehicle; an output signal from an engine speed sensor 58 indicating an operating speed Ne (rpm) of the engine 10;an output signal of a vehicle speed sensor 60 indicating a traveling speed spd (km / h) of the vehicle according to the rotational speed Nout of the output shaft 30 (hereinafter referred to as "output shaft rotational speed Nout"); an output signal of an input shaft rotational speed sensor 62 indicating the rotational speed Nin (rpm) of the input shaft 29 (hereinafter referred to as "input shaft rotational speed Nin"); and an output signal of an oil temperature sensor 64 indicating a temperature Toil (°C) of a working fluid in a hydraulic system in the transmission 16 that houses the continuously variable transmission 26.

[0019] The electronic control device 14 is a so-called microcomputer including a CPU, a ROM, a RAM, and an input-output interface. The electronic control device 14 performs control operations according to control programs stored in the ROM to process various input signals while utilizing a temporary data storage function of the RAM. Specifically, it performs a control operation to set a target value Nint of the input shaft speed Nin of the continuously variable transmission 26 to reduce a delay in the actual vehicle acceleration upon depression of the accelerator pedal 54 immediately after a quick release of the accelerator pedal 54, while ensuring a linear increase in the vehicle acceleration value upon depression of the accelerator pedal 54 by a relatively small amount.The electronic control device 14 is further configured to control a shift control valve 66 of the continuously variable transmission 26 to establish the thus set target value Nint of the input shaft speed Nin.

[0020] The electronic control device 14 comprises, with subsequent reference to the functional block diagram of Fig. 2, which shows the main control sections of the electronic control device 14 for controlling the vehicle driving force and the speed ratio γ of the continuously variable transmission 26, a restricted accelerator operation amount setting section 70, and a drive system control section 72. The restricted accelerator operation amount setting section 70 is configured to process an actual accelerator operation amount accpfb represented by the output signal pap of the accelerator operation amount sensor 56. The drive system control section 72 is configured to control a driving force of the vehicle based on a restricted accelerator operation amount accpfctrl generated by the restricted accelerator operation amount setting section 70.

[0021] The restricted accelerator operation amount setting section 70 includes an acceleration request determination section 74, a first restricted accelerator operation amount setting section 76, an accelerator release determination section 78, a second restricted accelerator operation amount setting section 80, and an upper limit stop processing section 82. The second restricted accelerator operation amount setting section 80 includes a second lower limit setting section 83 and a second lower limit stop processing section 84.

[0022] The acceleration request determination section 74 is configured to determine that the vehicle user requests acceleration of the vehicle when the amount and rate of increase of the actual accelerator pedal operation amount accpfb have exceeded respective predetermined thresholds. These thresholds are determined in advance through experimentation to detect a relatively rapid depression of the accelerator pedal 54 or to determine when the amount and rate of increase of the actual accelerator pedal operation amount accpfb exceed the determined thresholds.The first restricted accelerator operation amount setting section 76 is configured to perform a smoothing operation such as a first-order or second-order deceleration operation at a predetermined smoothing ratio with respect to the increase rate of the actual accelerator operation amount accpfb to generate the restricted accelerator operation amount accpfctrl when the acceleration request determining section 74 has determined that the vehicle user requests acceleration of the vehicle.The generated restricted accelerator operation amount accpfctrl is used to control the engine 10 and the continuously variable transmission 26 via the drive system control section 72 so that the increase rate of the restricted accelerator operation amount accpfctrl is lower than the increase rate of the actual accelerator operation amount accpfb, whereby the initial acceleration shock upon acceleration of the vehicle can be mitigated.

[0023] The first restricted accelerator operation amount setting section 76 includes a first lower limit setting section 86, a sweep-up processing section 88, and a first lower limit stop processing section 90. The first lower limit setting section 86 is configured to set a lower limit of an amount of attenuation or decrease of the accelerator operation amount, that is, calculates a first lower limit value accpflogrd according to the following equation (1) by subtracting a predetermined value from the actual accelerator operation amount accpfb. The increase processing section 88 is configured to calculate the restricted accelerator operation amount value accpfctrl. (i) in the present control cycle according to the following equation (2) by adding a predetermined increase value Δaccpfctrl to the restricted accelerator operation amount value accpfctrl (i-1)in the last control cycle, so that the restricted accelerator operation amount accpfctrl is linearly increased. The first lower limit stop processing section 90 is configured to stop the increase processing operation of the increase processing section 88 according to the following equation (3) to prevent the restricted accelerator operation amount accpfctrl from decreasing below the first lower limit value accpflogrd, that is, to prevent the restricted accelerator operation amount accpfctrl from decreasing from the actual accelerator operation amount accpfb by more than the above-described predetermined value with reference to the first lower limit setting section 86. accpflogrd=accpfb−predetermined value accpfctrl(i)=accpfctrl(i−1)+predetermined increase value Δaccpfctrl accpflogrd≤accpfctrl

[0024] The accelerator pedal release determination section 78 is configured to determine that the vehicle user has quickly released the accelerator pedal 54 when an amount and a rate of decrease of the actual accelerator pedal operation amount accpfb have exceeded respective predetermined thresholds. These thresholds are determined in advance through experimentation to detect a relatively rapid release of the accelerator pedal 54 or to determine when the amount and the rate of decrease of the actual accelerator pedal operation amount accpfb exceed the determined thresholds. The second lower limit setting section 83 of the second restricted accelerator pedal operation amount setting section 80 is configured to set the restricted accelerator pedal operation amount accpfctrl. (i-1)in the last control cycle, that is, the actual accelerator pedal operation amount accpfb in the last control cycle, as an attenuated accelerator pedal operation amount accpfdec according to the following equation (4) repeatedly until the accelerator pedal release determination section 78 determines that the vehicle user has quickly released the accelerator pedal 54. After the accelerator pedal release determination section 78 determines that the vehicle user has quickly released the accelerator pedal 54, the second lower limit setting section 83 performs a sweep-down processing operation to obtain a predetermined decrease value Δaccpfdec from the attenuated accelerator pedal operation amount accpfdec. (i-1) in the last control cycle to thereby repeatedly calculate the attenuated accelerator pedal operation amount accpfdec (i)in the present control cycle so that the attenuated accelerator pedal operation amount accpfdec used as a second lower limit value is linearly decreased. The above-indicated predetermined decrease value Δaccpfdec corresponds to a decrease amount in each control cycle, which therefore represents a decrease rate of the attenuated accelerator pedal operation amount accpfdec. The decrease value Δaccpfdec is set as a function of the vehicle traveling speed spd or the weight or a gradient of a road surface on which the vehicle is traveling. That is, the decrease value Δaccpfdec is set to decrease with an increase in the vehicle traveling speed spd or the weight or the road surface gradient.The second lower limit stop processing section 84 of the second restricted accelerator operation amount setting section 80 is configured to perform a lower limit processing operation for stopping the decrease processing operation of the second lower limit setting section 83 according to the following equation (5) to prevent the restricted accelerator operation amount accpfctrl from decreasing below the relaxed accelerator operation amount accpfdec during the decrease processing operation of the second lower limit setting section 83.Therefore, the second restricted accelerator operation amount setting section 80 including the second lower limit setting section 83 and the second lower limit stop processing section 84 serves to decrease the restricted accelerator operation amount accpfctrl at a lower rate than the decrease rate of the actual accelerator operation amount accpfb, the decrease rate being generally high, after the accelerator release determining section 78 determines that the vehicle user has quickly released the accelerator pedal 54.The upper limit stop processing section 82 is configured to prevent an increase in the restricted accelerator operation amount accpfctrl above the actual accelerator operation amount accpfb according to the following equation (6), so that the restricted accelerator operation amount accpfctrl is linearly decreased to the actual accelerator operation amount accpfb at the rate lower than the decrease rate of the actual accelerator operation amount accpfb during the release operation of the accelerator pedal 54. accpfctrl(i)=accpfctrl(i−1)−Δaccpfctrl accpfdec≤accpfctrl accpfctrl≤accpfb

[0025] The drive system control section 72 includes a target driving force calculation section 92, a target output torque calculation section 94, a target engine torque setting section 96, an engine torque control section 98, a target input shaft speed setting section 100, and a shift control section 102.

[0026] The target driving force calculation section 92 is configured to repeatedly calculate a target (required) vehicle driving force FORCEDCL during normal travel, acceleration travel (which may occur following a release of the accelerator pedal 54), or deceleration travel of the vehicle based on the actual vehicle running speed spd and the restricted accelerator operation amount accpfctrl, and according to a predetermined and stored relationship between the target vehicle driving force FORCEDCL and the vehicle running speed spd and the restricted accelerator operation amount accpfctrl. The target output torque calculation section 94 is configured to repeatedly calculate a target output POWER by multiplying the calculated target vehicle driving force FORCEDCL by the vehicle running speed spd.The target engine torque setting section 96 is configured to repeatedly calculate a target torque TE of the engine 10 by dividing the target output POWER calculated by the target output torque calculating section 94 by the current operating speed Ne of the engine 10 or a target input shaft speed Nint calculated by the target input shaft speed setting section 100. The engine torque control section 98 is configured to repeatedly control the throttle actuator 48 to control the opening angle θth of the throttle valve 50 to establish the calculated target engine torque TE.

[0027] The target input shaft speed setting section 100 is configured to repeatedly calculate the target input shaft speed Nint based on the actual vehicle running speed spd and the restricted accelerator pedal operation amount accpfctrl and according to a predetermined and stored relationship between the target input shaft speed Nint and the vehicle running speed spd and the restricted accelerator pedal operation amount accpfctrl.The shift control section 102 is configured to repeatedly control the shift control valve 66 so that the actual input shaft speed Nin matches the calculated target input shaft speed Nint, that is, to repeatedly control the flow rate of the working fluid into the hydraulic actuator 32 of the input-side variable-diameter pulley 36 or out of the hydraulic actuator 32, thereby controlling the speed ratio γ of the belt-and-pulley type continuously variable transmission. For example, the shift control section 102 controls the speed ratio γ of the continuously variable transmission 26 according to a PI feedback control equation so that the input shaft speed Nin matches the target value Nint, that is, a difference (=Nint-Nin) is reduced.Since the target input shaft speed Nint is calculated based on the restricted accelerator operation amount accpfctrl, the shift control section 102 controls the speed ratio γ of the continuously variable transmission 26 based on the restricted accelerator operation amount accpfctrl.

[0028] In the time diagram of Fig. 3, the broken and solid lines respectively represent changes in the actual accelerator pedal operation amount accpfb and the restricted accelerator pedal operation amount accpfctrl compared to each other when the acceleration request of the vehicle user is determined by the acceleration request determination section 74. In the example of the time chart of Fig. 3, in which the actual accelerator pedal operation amount accpfb is rapidly increased at a very high rate at a time t1, the restricted accelerator pedal operation amount setting section 76 increases the restricted accelerator pedal operation amount accpfctrl linearly at a lower rate than the increase rate of the actual accelerator pedal operation amount accpfb to mitigate the initial vehicle acceleration shock. In the time chart of Fig. 4, the broken line represents a change in an actual engine speed Neb to be controlled based on the actual accelerator pedal operation amount accpfb, while the solid line represents a change in an engine speed Nectrl to be controlled based on the restricted accelerator pedal operation amount accpfctrl when the acceleration request determining section 74 has determined that the vehicle user requests acceleration of the vehicle. In the example of the time chart of Fig. 4, in which the engine speed Neb to be controlled based on the actual accelerator pedal operation amount accpfb is increased at a high rate in a short time from a time t1, the drive system control section 72 controls the engine speed Nectrl controlled based on the restricted accelerator pedal operation amount accpfctrl so that the engine speed Nectrl is increased at a lower rate than the increase rate of the engine speed Neb in a comparatively long time from the time t1. In the time chart of Fig. 5, the broken line represents a change in the vehicle running speed spdb when the vehicle is driven by the driving force to be controlled by the drive system control section 72 based on the actual accelerator operation amount accpfb, while the solid line represents a change in the vehicle running speed spdctrl when the vehicle is driven by the driving force to be controlled by the drive system control section 72 based on the restricted accelerator operation amount accpfctrl when the acceleration request determination section 74 has determined that the vehicle user requests acceleration of the vehicle. In the example of the time chart of Fig. 5, the traveling speed spdctrl of the vehicle to be driven by the driving force to be controlled by the drive system control section 72 based on the restricted accelerator operation amount accpfctrl is increased at a lower rate than an increasing rate of the traveling speed spdb of the vehicle to be driven by the driving force to be controlled by the drive system control section 72 based on the actual accelerator operation amount accpfb.

[0029] Fig. 6 is the time chart indicating changes in the restricted accelerator pedal operation amount accpfctrl and the attenuated accelerator pedal operation amount accpfdec, which are respectively set by the first and second restricted accelerator pedal operation amount setting sections 76 and 80, the actual accelerator pedal operation amount accpfb, and the first lower limit value accpflogrd when the accelerator pedal 54 is quickly depressed immediately after a quick release of the accelerator pedal 54. In the example of the time chart of Fig. 6, the vehicle is driven in a steady state until a time t1. During this stable vehicle drive, the actual accelerator pedal operation amount accpfb, indicated by a solid line, the restricted accelerator pedal operation amount accpfctrl, indicated by a broken line, and the mitigated accelerator pedal operation amount accpfdec, indicated by a two-dot chain line, are all kept constant at the same value, while the first lower limit value accpflogrd is kept constant at a value smaller than the actual accelerator pedal operation amount accpfb by the predetermined value.In response to the rapid release operation of the accelerator pedal 54 at time t1, the actual accelerator operation amount accpfb shown by the solid line is rapidly decreased, while the restricted accelerator operation amount accpfctrl, also shown by the broken line, is rapidly decreased to the same value as the actual accelerator operation amount accpfb, under a restriction process of the lower limit stop processing section 82. Thereafter, the actual and restricted accelerator operation amounts accpfb and accpfctrl are maintained at this value until a time t4 at which the accelerator pedal 54 is depressed again.After the quick release operation of the accelerator pedal 54, the mitigated accelerator operation amount accpfdec is decreased by a decrease processing operation of the second lower limit stop processing section 84 from the restricted accelerator operation amount accpfb immediately before the quick release operation at a lower rate than the decrease rate of the actual accelerator operation amount accpfb.However, during a time period from time t1 to time t4 in which the accelerator pedal 54 is maintained in the released state and the attenuated accelerator operation amount accpfdec serves as the lower limit (second lower limit) of the restricted accelerator operation amount accpfctrl, under a restriction process of the upper limit stop processing section 82, the restricted accelerator operation amount accpfctrl is held ineffective until time t4 at which the actual accelerator operation amount accpfb rapidly increases to a value larger than the attenuated accelerator operation amount accpfdec due to the subsequent depression operation of the accelerator pedal 54.

[0030] After time t4 at which the actual accelerator operation amount accpfb rapidly increases due to the depression of the accelerator pedal 54 and exceeds the attenuated accelerator operation amount accpfdec, the restricted accelerator operation amount accpfctrl, whose lower limit is set to the attenuated accelerator operation amount accpfdec without the restriction process of the upper limit stop processing section 82, is increased at a lower rate than the increase rate of the actual accelerator operation amount accpfb under an increase processing process of the first restricted accelerator operation amount setting section 76, and the vehicle is brought into a stable running state at time t5.During a time period from a time t3 at which the accelerator pedal 54 is depressed again to the time t4 at which the actual accelerator operation amount accpfb exceeds the mitigated accelerator operation amount accpfdec, the restricted accelerator operation amount accpfctrl is rapidly increased together with the actual accelerator operation amount accpfb, which makes it possible to prevent or reduce a difference in the output torque of the engine 10 from the value expected by the vehicle user and a risk of deceleration of the vehicle acceleration, which is perceived by the vehicle user when the accelerator operation amount is increased again after being decreased once.

[0031] The above-mentioned time t4 is represented by an intersection point between the line representing the change in the actual accelerator pedal operation amount accpfb and the line representing the change in the attenuated accelerator pedal operation amount accpfdec. This time t4 is delayed with a decrease in the slope or gradient of the line representing the attenuated accelerator pedal operation amount accpfdec, so that the time phase between times t3 and t4, in which the actual and attenuated accelerator pedal operation amounts accpfb and accpfdec are rapidly increased, is correspondingly extended. The decrease value Δaccpfdec, which defines the gradient of the line representing the attenuated accelerator pedal operation amount accpfdec, is set as a function of the vehicle traveling speed spd, the weight, or the road surface gradient.such that the reduction value Δaccpfdec decreases with an increase in the vehicle traveling speed spd or the weight or the road surface gradient, so that the time phase between times t3 and t4 in which the actual and attenuated accelerator pedal operation amounts accpfb and accpfdec are rapidly increased is increased with the increase in the vehicle traveling speed spd or the weight or the road surface gradient, which makes it possible to prevent or reduce the difference in the output torque of the engine 10 from the value expected by the driver and the risk of deceleration of the vehicle acceleration perceived by the vehicle user when the accelerator pedal operation amount is increased again after it has been decreased once, regardless of the vehicle traveling speed spd or the weight or the road surface gradient.

[0032] The time diagram of Fig. 7 indicates a change in the restricted accelerator operation amount accpfctrl set by the first restricted accelerator operation amount setting section 76 and the actual accelerator operation amount accpfb when the accelerator pedal 54 is depressed after a quick release operation of the accelerator pedal 54, wherein the second restricted accelerator operation amount setting section 80 according to the present invention is not provided, that is, without the second lower limit stop processing section 84 configured to perform the decrease processing operation for decreasing the attenuated accelerator operation amount accpfdec from the restricted accelerator operation amount accpfctrl. (i-1)in the last control cycle immediately before the quick release operation of the accelerator pedal 54 at a lower rate than the decrease rate of the actual accelerator operation amount accpfb, to set the thus reduced attenuated accelerator operation amount accpfdec as the lower limit of the restricted accelerator operation amount accpfctrl. Accordingly, the restricted accelerator operation amount accpfctrl is increased by the first restricted accelerator operation amount setting section 76 at a lower rate than the increase rate of the actual accelerator operation amount accpfb, as shown in Fig. 3, in response to a rapid increase in the actual accelerator pedal operation amount accpfb upon the depression of the accelerator pedal 54 at time t3, resulting in a significant difference in the engine output torque from the value expected by the vehicle user and a risk of a delay in the vehicle acceleration perceived by the vehicle user while the vehicle is being accelerated.

[0033] The flowchart of Fig. 8 represents an essential part of a main control routine executed by the electronic control device 14. The main control routine of Fig. 8 begins with a step S1 to obtain the actual accelerator pedal operation amount accpfb based on the accelerator pedal operation amount sensor 56, which indicates the operation amount pap (%) of the accelerator pedal 54. Subsequently, the control flow proceeds to a step S2 according to the acceleration request determination section 74 to determine whether the vehicle user requests acceleration of the vehicle. This determination is made depending on whether the rate of increase of the actual accelerator pedal operation amount accpfb has exceeded the predetermined value.At this step S2, which also corresponds to the first lower limit setting section 86, the first lower limit value accpflogrd for a reduced value of the operation amount pap of the accelerator pedal 54 is calculated according to the actual accelerator pedal operation amount accpfb according to the above-mentioned equation (1) so that the first lower limit value accpflogrd is smaller than the actual accelerator pedal operation amount accpfb by the predetermined value or ratio.

[0034] The control flow then proceeds to step S3 according to the increase processing section 88 to perform the increase processing operation for repeatedly calculating the restricted accelerator pedal operation amount accpfctrl according to the above-mentioned equation (2) so that the restricted accelerator pedal operation amount accpfctrl is linearly increased from the value smaller than the actual accelerator pedal operation amount accpfb. The restricted accelerator pedal operation amount accpfctrl corresponds to a control command value of the operation amount pap of the accelerator pedal 54, which is used to control the engine 10 and the continuously variable transmission 26. According to the equation (2), the predetermined increase value Δaccpfctrl is set to the restricted accelerator pedal operation amount accpfctrl every control cycle. (i-1) added in the last tax cycle.

[0035] Subsequently, the control flow proceeds to a step S4 according to the first lower limit stop processing section 90 to perform the lower limit stop processing operation according to the above-mentioned equation (3) based on the first lower limit value accpflogrd for preventing the restricted accelerator operation amount accpfctrl from decreasing below the first lower limit value accpflogrd obtained at S2.

[0036] The control flow then proceeds to step S5 according to the second lower-limit stop processing section 84 to perform the lower-limit stop processing according to the above-mentioned equation (5) after the decrease processing to repeatedly decrease the attenuated accelerator operation amount after the release operation of the accelerator pedal 54, in order to prevent the restricted accelerator operation amount accpfctrl from decreasing below the attenuated accelerator operation amount accpfdec (lower limit value). That is, one of the attenuated accelerator operation amount accpfdec (lower limit value) and the restricted accelerator operation amount accpfctrl, which is larger than the other, is used to determine the target input shaft speed Nint.

[0037] Subsequently, the control flow proceeds to step S6 according to the upper-limit stop processing section 82 to perform the upper-limit stop processing according to the above-mentioned equation (6) to prevent the restricted accelerator pedal operation amount accpfctrl from increasing beyond the upper limit, that is, the actual accelerator pedal operation amount accpfb. Since this step S6 is implemented as the last step in the main control routine, the upper-limit stop processing takes precedence over the lower-limit stop processing operations in steps S4 and S5.

[0038] While the above-described steps S1 to S4 and S6 in the present embodiment are also implemented in the prior art, the present embodiment differs from the prior art in that step S5 and steps S7 to S9 of a flowchart described below with reference to the flowchart of Fig. 9 are additionally implemented in the present embodiment. In the subroutine of Fig. 9, step S7 is implemented according to the accelerator pedal release determination section 78 to make a determination as to whether the vehicle user has released the accelerator pedal 54 quickly. For example, this determination is made depending on whether the actual accelerator pedal operation amount accpfb is less than a predetermined threshold. If a negative determination is obtained in step S7, the control flow proceeds to step S8 to determine the restricted accelerator pedal operation amount accpfctrl. (i-1)in the last control cycle as an initial value of the attenuated accelerator pedal operation amount accpfdec. If an affirmative determination is obtained at step S7, the control flow proceeds to step S9 according to the second lower limit setting section 83 to execute the decrease processing operation for repeatedly decreasing the attenuated accelerator pedal operation amount accpfdec in each control cycle according to the above-mentioned equation (4) by subtracting the predetermined decrease value Δaccpfdec from the value accpfdec held at step S8 in the last control cycle. (i-1) The predetermined reduction value Δaccpfdec is determined such that the attenuated accelerator pedal operation amount accpfdec is reduced at a lower rate than the rate of decrease of the actual accelerator pedal operation amount accpfb. Steps S8 and S9 follow step S5 of Fig. 8. The attenuated accelerator operation amount accpfdec reduced as described above is calculated at step S5 and the subsequent steps of Fig. 8 used.

[0039] According to the electronic control device 14 provided in the present embodiment, the second restricted accelerator operation amount setting section 80 is configured to set the attenuated accelerator operation amount accpfdec, which is used as the lower limit of the restricted accelerator operation amount accpfctrl, from the restricted accelerator operation amount accpfctrl (i-1)immediately before the quick release operation of the accelerator pedal 54 is decreased at the lower rate than the decrease rate of the actual accelerator pedal operation amount accpfb after the moment of detecting the quick release operation of the accelerator pedal 54, and the upper limit stop detecting section 82 is configured to restrict the restricted operation amount accpfctrl of the accelerator pedal 54 after the moment of detecting that the vehicle user requests the acceleration of the vehicle, so that the restricted accelerator pedal operation amount accpfctrl is not greater than the actual accelerator pedal operation amount accpfb.Accordingly, the speed ratio of the continuously variable transmission 26 is controlled by the drive system control section 72 based on the restricted accelerator operation amount accpfctrl, the restriction of which is canceled by rapidly increasing the actual accelerator operation amount accpfb upon a rapid depression operation of the accelerator pedal 54 following the rapid release operation of the accelerator pedal 54.Therefore, the speed ratio of the continuously variable transmission 26 is controlled based on the restricted accelerator operation amount accpfctrl, which rapidly increases along with a rapid increase in the actual accelerator operation amount accpfb, until the actual accelerator operation amount accpfb exceeds the mitigated accelerator operation amount accpfdec, which is provided as the lower limit of the restricted accelerator operation amount accpfctrl, due to the increase in the actual accelerator operation amount accpfb upon a rapid depression of the accelerator pedal 54 immediately after the rapid release operation, so that the vehicle driving force is rapidly increased after the depression of the accelerator pedal 54. That is, the engine torque is rapidly increased after the rapid depression of the accelerator pedal 54, and the risk of a delay in the vehicle acceleration perceived by the vehicle user is reduced.

[0040] The electronic control device 14 is further configured such that the rate of decrease of the attenuated accelerator operation amount accpfdec is used as the lower limit of the restricted accelerator operation amount accpfctrl, so that the restricted accelerator operation amount accpfctrl is determined from the value accpfctrl (i-1)immediately before the quick release operation of the accelerator pedal 54 at a lower rate than the rate of decrease of the actual accelerator pedal operation amount accpfb after the moment of the quick release operation of the accelerator pedal 54. This rate of decrease of the attenuated accelerator pedal operation amount accpfdec is set as a function of the vehicle traveling speed spd or the weight or the road surface gradient to decrease with an increase in the vehicle traveling speed spd or the weight or the road surface gradient. Accordingly, the rate of decrease of the restricted accelerator pedal operation amount accpfctrl is set to decrease with the increase in the vehicle traveling speed spd or the weight or the road surface gradient.Therefore, at time t4, at which the restriction of the restricted accelerator pedal operation amount accpfctrl to a value not greater than the actual accelerator pedal operation amount accpfb is canceled due to a rapid depression of the accelerator pedal 54 following its rapid release operation, the restricted accelerator pedal operation amount accpfctrl is greater than the actual accelerator pedal operation amount accpfb by an amount that increases with the increase in the vehicle traveling speed spd or the weight or the road surface gradient. Accordingly, the risk of a delay in the vehicle acceleration perceived by the vehicle user after the rapid release of the accelerator pedal 54 is effectively reduced. Second embodiment

[0041] The flowchart of Fig. Fig. 10 illustrates a control process of the electronic control device 14 according to another embodiment of this invention, that is, a subroutine in which steps S10 to S13 are performed in addition to steps S7 to S9 in the subroutine of Fig. 9 according to the previous embodiment of Fig. 8 are implemented. In Fig. 10 are the same steps as in the embodiment of Fig. 8 are marked by the same step numbers as in Fig. 9 are used, and these are not described repeatedly.

[0042] The subroutine of Fig. 10 is initiated with a step S10 to determine whether the vehicle user has rapidly released the accelerator pedal 54. This determination is made depending on whether a decrease amount Δaccpfb of the accelerator pedal 54 is smaller than a predetermined value. If a negative determination is obtained in step S10, the control flow proceeds to a step S12, while skipping a step S11. If an affirmative determination is obtained in step S10, the control flow proceeds to step S11 to set an accelerator pedal release flag xaccpfdec to an on state. Subsequently, the control flow proceeds to step S12 to determine whether the vehicle user has rapidly depressed the accelerator pedal 54. This determination is made depending on whether the decreased accelerator pedal operation amount accpfdec (i-1) in the last control cycle is less than the restricted accelerator pedal operation amount accpfctrl (i-1)in the last control cycle. If a negative determination is obtained at step S12, the control flow proceeds to step S7, while skipping a step S13. If an affirmative determination is obtained at step S12, the control flow proceeds to step S13 to reset the accelerator pedal release flag xaccpfdec to an off state. Then, the control flow proceeds to step S7 to determine whether the accelerator pedal 54 is in the released state. This determination is made depending on whether the accelerator pedal release flag xaccpfdec is in the on state. If a negative determination is obtained at step S7, the control flow proceeds to step S8 to reset the restricted accelerator pedal operation amount accpfctrl. (i-1)in the last control cycle as the attenuated accelerator pedal operation amount accpfdec. If an affirmative determination is obtained at step S7, the control flow proceeds to step S9 to set the attenuated accelerator pedal operation amount accpfdec such that the attenuated accelerator pedal operation amount accpfdec decreases at a lower rate than the decrease rate of the actual accelerator pedal operation amount accpfb. The attenuated accelerator pedal operation amount accpfdec, which is decreased as described above, is set at step S5 and the subsequent steps of Fig. 8 used.

[0043] While the preferred embodiments of this invention have been described in detail with reference to the drawings, it will be understood that the invention may be embodied otherwise.

[0044] In the vehicle provided with the continuously variable transmission 26 in the illustrated embodiments, the output torque of the engine 10 and the speed ratio γ of the continuously variable transmission 26 are controlled by so-called "drive force request type" control implemented by the drive system control section 72. However, the drive system control section 72 may be replaced by a drive system control section configured to determine the target input shaft speed Nint based on the vehicle traveling speed spd and the opening angle θth of the throttle valve 50, and according to a predetermined relationship between the vehicle traveling speed spd and the target input shaft speed Nint with the accelerator pedal operation amount used as a control parameter.This relationship is represented by a two-dimensional coordinate system in which the vehicle speed spd and the target input shaft speed Nint are recorded along the two respective axes.

[0045] In the illustrated embodiments, the continuously variable transmission 26 corresponds to the so-called "belt and pulley type" continuously variable transmission. However, this continuously variable transmission can be replaced by a so-called "traction type" continuously variable transmission, in which a roller is supported between a pair of cones arranged for rotation relative to each other about a common axis, so that the roller is rotatable about an axis that is rotatable in a plane including the axes of rotation of the cones.

[0046] In the illustrated embodiments, the continuously variable transmission 26 corresponds to the so-called "belt and pulley type" continuously variable transmission. However, the continuously variable transmission 26 may be replaced by an electrically controlled continuously variable transmission having a differential gear device with a first rotating element (input shaft) connected to an engine, a second rotating element connected to a first motor / generator, and a third rotating element connected to drive wheels via a power transmission shaft (output shaft), and further having a second motor / generator connected to the power transmission shaft. The first motor / generator, which generates a reaction force according to an output of the engine, is controlled to control the speed ratio of the continuously variable transmission.

[0047] It is to be understood that the above-described embodiments and modifications are given for the purpose of illustration only, and that the present invention may be embodied with various other changes and improvements which will be apparent to those skilled in the art. List of reference symbols 10 machines 14 Electronic control device 26 Continuously variable transmission 54 Accelerator pedal 70 Setting section for a limited accelerator pedal operation amount 72 Drive system control section 76 First setting section for a limited accelerator pedal operation amount 80 Second setting section for a limited accelerator pedal operation amount 102 Switch control section

Claims

[1] A control device (14) for a vehicle provided with a continuously variable transmission (26), comprising an acceleration request determination section (74) configured to determine, based on an actual operation amount (accpfb) of a vehicle acceleration element (54) by a user of the vehicle, whether the user requests acceleration of the vehicle, a first accelerator pedal restriction amount setting section (76) configured to set a restriction amount (accpfctrl) of the vehicle acceleration element such that the restriction amount gradually increases with an increase in a traveling speed (spd) of the vehicle when the acceleration request determination section has determined that the user of the vehicle requests acceleration of the vehicle, and a shift control section (102) configured tothat it controls a speed ratio of the continuously variable transmission based on the limited operation amount (accpfctrl) of the vehicle acceleration element, the control device further comprising: a second accelerator pedal restricted operation amount setting section (80) configured to set the restricted operation amount (accpfctrl) of the vehicle acceleration element from a value (accpfctrl (i-1) ) immediately before a moment of detection of a quick release operation of the vehicle acceleration element (54) at a lower rate than a rate of decrease of the actual operation amount (accpfb) of the vehicle acceleration element (54) after the moment of detection of the quick release operation, and an upper limit stop processing section (82) configured to limit the restricted operation amount (accpfctrl) of the vehicle acceleration element after a moment of determining that the user of the vehicle requests the acceleration of the vehicle, so that the restricted operation amount is not greater than the actual operation amount (accpfb), wherein the second restricted accelerator operation amount setting section (80) comprises: a lower limit setting section (83) configured to set an attenuated accelerator operation amount (accpfdec) after the quick release operation detection moment, which corresponds to a lower limit of the restricted operation amount (accpfctrl) of the vehicle acceleration element, in each control cycle by subtracting a predetermined reduction value (Δaccpfdec) from an attenuated accelerator operation amount value (accpfdec (i-1)) in a last control cycle; and a lower limit stop processing section (84) configured to set the restricted operation amount (accpfctrl) of the vehicle acceleration element after the moment of detection of the quick release operation such that the restricted operation amount is not lower than the attenuated accelerator pedal operation amount (accpfdec). [2] A control device according to claim 1, wherein the rate of decrease of the restricted operation amount (accpfctrl) of the vehicle acceleration element (54) from the value (accpfetrl (i-1)) immediately before the quick release operation as a function of a vehicle speed (spd) or a weight of the vehicle or a gradient of a road surface on which the vehicle is traveling, is set to decrease with an increase in the vehicle speed or the weight of the vehicle or the gradient of the road surface. [3] A control device according to claim 1 or 2, which is configured to receive an output signal of an accelerator pedal operation amount sensor (56) for detecting an actual operation amount (accpfb) of an accelerator pedal provided as the vehicle acceleration element.

Images