JP3671699B2 - Vehicle driving force control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle driving force control apparatus, particularly a continuously variable transmission, which can generate a required axle driving force of a vehicle equipped with a continuously variable transmission by a combination with an optimum engine output and a gear ratio. The present invention relates to a driving force control device for a vehicle that can perform a useful operation when it is set to the neutral range during traveling or when it is subsequently returned to the traveling range.
[0002]
[Prior art]
A continuously variable transmission represented by a V-belt type continuously variable transmission or a toroidal type continuously variable transmission generally obtains a target gear ratio from an engine demand load and a vehicle speed, and the actual gear ratio becomes this target gear ratio. Shift control is performed.
Accordingly, during acceleration in which the driver depresses the accelerator pedal and the engine required load is increased, the target gear ratio is changed to become larger (the gear ratio on the low speed side), and the continuously variable transmission is changed to the increased target. Downshift to gear ratio,
Conversely, during low-load operation where the driver returns the accelerator pedal to reduce the engine load requirement, the target gear ratio is changed to become smaller (the gear ratio on the high speed side), and the continuously variable transmission becomes smaller. Upshift to the set target gear ratio is performed.
[0003]
On the other hand, as a technique for obtaining a required driving force of a vehicle, there is a conventional technique described in, for example, Japanese Patent Laid-Open No. 7-172217.
In this technique, a target driving force of a vehicle is obtained from the vehicle speed and the accelerator pedal depression amount, and a running resistance component that can be estimated from the vehicle speed is added to this to obtain a required driving force to be transmitted to the wheels.
[0004]
By the way, with the above-described shift control of the general continuously variable transmission, it is impossible to accurately realize the required driving force obtained by the technique according to the above-mentioned literature. However, it is impossible to achieve the required driving force obtained in such a manner that the fuel consumption of the engine is minimized, for example.
[0005]
For example, in order to achieve the required driving force in such a manner that the fuel consumption of the engine is minimized, the required driving force is controlled by engine output control and continuously variable transmission shift control (engine speed control). It is conceivable to control the driving force of the vehicle realized by the optimal combination of the above.
[0006]
As a driving force control system therefor, for example, the required minimum axle driving force is obtained by the method described in Japanese Patent Laid-Open No. 7-172217 from the driving state and traveling conditions of the vehicle such as the vehicle speed and the accelerator pedal depression amount,
Find the optimal combination of target engine speed and target engine output to achieve the required axle driving force with minimum fuel consumption, for example,
A driving force control device is conceivable that shifts the continuously variable transmission so as to achieve a transmission target input rotational speed corresponding to the target engine rotational speed, and controls the output of the engine by throttle opening operation so as to achieve the target engine output.
[0007]
[Problems to be solved by the invention]
By the way, the optimal combination of the target engine speed and the target engine output for achieving the required axle driving force is obtained, and the continuously variable transmission is controlled to be shifted and the throttle opening of the engine is achieved. It has been confirmed that the driving force control device for controlling (engine output) has the following problems.
[0008]
The engine output (torque) characteristics are determined by the throttle opening and the engine speed, and the engine output (torque) increases as the throttle opening increases, and the engine output (torque) increases as the engine speed increases. .
Therefore, even when the same target engine output is realized, the target throttle opening for that purpose increases as the engine speed increases.
Therefore, while the throttle opening (engine output) control is being performed, the driver changes the continuously variable transmission from the traveling range to a neutral range where power cannot be transmitted, or the continuously variable transmission cannot transmit power due to a failure. When the engine is in a neutral state and throttle opening (engine output) control is performed according to the target engine output determined above regardless of the engine speed even though the engine is unloaded However, no matter how small the throttle opening is, the throttle opening will be controlled to increase as the engine speed increases as the engine becomes unloaded. A rise is produced.
[0009]
According to the first aspect of the present invention, the normal target engine output determined regardless of the engine speed can be continuously controlled as it is in the engine output (throttle opening) state even under the no-load state of the engine. Based on the recognition of the fact that it contributes, the object of the present invention is to realize the solution to the above problem by contributing another engine output target value to engine output control when the engine is not loaded.
[0010]
The second aspect of the present invention is to propose a preferable method for obtaining another engine output target value and to make the operational effect of the first aspect remarkable.
[0011]
According to a third aspect of the present invention, if the accelerator pedal depression amount is constant, the other engine output target value to be given by the engine output control in the no-load state is reduced as the engine speed increases. From the viewpoint that the above problem can be solved by this, an object of the present invention is to propose a driving force control device that embodies this idea.
[0012]
A fourth aspect of the present invention is to propose a driving force control apparatus that can more easily obtain the other engine output target value.
[0013]
According to a fifth aspect of the present invention, when the continuously variable transmission returns from the neutral state to the power transmission enabled state, the engine is not loaded until the friction element for performing the return completes the fastening. In this state, the above-mentioned problem related to the engine speed increase still occurs, so the engine output control value at the time of return can also be avoided by continuing to use the other engine output target value for engine output control during this period. It is an object of the present invention to propose a driving force control device that can be used.
[0014]
A sixth aspect of the present invention is to propose a driving force control apparatus that can determine the completion of the engagement of the friction element in the fifth aspect at low cost without relying on a rotation sensor.
[0015]
According to a seventh aspect of the present invention, there is proposed a driving force control device that can reliably determine the completion of the engagement of the friction element in the fifth aspect by the output from the rotation sensor even when a torque converter is present. For the purpose.
[0016]
[Means for Solving the Problems]
  For these purposes, the vehicle driving force control apparatus according to the first invention
  A vehicle equipped with a power train that combines an engine whose output can be arbitrarily changed depending on factors other than the accelerator pedal operation and a continuously variable transmission,
  The target engine speed for realizing the required axle driving force determined by the driving state and driving conditions of the vehicle andTarget engine output torqueSeeking the best combination of
  Shifting the continuously variable transmission to a transmission target input rotational speed corresponding to the target engine rotational speed,Target engine output torqueIn the vehicle driving force control device that controls the output of the engine so that
  When the continuously variable transmission is in a neutral state where power cannot be transmitted during vehicle travel,The neutral engine output torque target value is obtained by limiting the target engine output torque according to the engine speed so that the engine speed does not increase even in the neutral state, and the neutral engine output torque is replaced with the neutral engine output torque. Engine output torque target valueIt is configured to contribute to the engine output control.
[0017]
  A vehicle driving force control apparatus according to a second aspect of the present invention is the first aspect of the invention,
  SaidNeutral engine output torque target valueIs obtained from the accelerator pedal depression amount and the engine speed based on a predetermined characteristic.
[0018]
  According to a third aspect of the present invention, there is provided a vehicle driving force control apparatus that achieves a predetermined characteristic according to the second aspect of the invention as the engine speed increases.Neutral engine output torque target valueTo reduce the accelerator pedal depression amountNeutral engine output torque target valueIt is characterized by having assigned the characteristics of.
[0019]
  According to a fourth aspect of the present invention, there is provided the vehicle driving force control apparatus according to any one of the first to fourth aspects of the invention.
  When the continuously variable transmission returns from the neutral state to the power transmission enabled state, the neutral engine output torque target value is continuously set to the engine output torque until the friction element for performing the return completes the engagement. It is characterized by being configured to contribute to control.
[0020]
  A vehicle driving force control apparatus according to a fifth aspect of the present invention is the fourth aspect of the invention,
The friction element is configured to determine that the engagement has been completed when a set time has elapsed since a command to change the continuously variable transmission from a neutral state to a power transmission enabled state is issued. .
[0021]
  The vehicle driving force control apparatus according to a sixth aspect of the present invention is the vehicle according to the fourth aspect or the fifth aspect,
  When the torque converter between the continuously variable transmission and the engine is in a lock-up state in which the input / output elements are directly connected, the friction element completes the engagement when the transmission input rotational speed matches the engine rotational speed. It is characterized by having comprised so that it may be judged.
[0022]
【The invention's effect】
  In the first invention, an optimum combination of the target engine speed and the target engine output torque for realizing the required axle driving force determined by the driving state and traveling conditions of the vehicle is obtained,
A driving force control is performed to control the transmission of the continuously variable transmission so as to be the transmission target input rotational speed corresponding to the target engine rotational speed and to control the output of the engine so as to be the target engine output torque.
  The output from the engine controlled in this way is shifted by the continuously variable transmission controlled as described above to become the output of the power train.
[0023]
  When the continuously variable transmission is set to a neutral state where power cannot be transmitted due to a range change or failure while the vehicle is running under such driving force control, the engine rotation is not increased even in such a neutral state. The target engine output torque limited according to the engine speed is used as a neutral engine output torque target value, and the neutral engine output torque target value is used for the engine output control instead of the target engine output torque.
[0024]
  Therefore, even when the continuously variable transmission is set to the neutral state during traveling, the above-described engine speed surging that has conventionally occurred by using the target engine output torque determined irrespective of the engine speed is continued. The problem can be solved reliably.
[0025]
  In the second invention, the aboveNeutral engine output torque target valueIs determined from the accelerator pedal depression amount and engine speed based on the planned characteristics,
  ConcernedNeutral engine output torque target valueCan be easily obtained by map search or the like, and can be accurately matched to the driving conditions.
[0026]
  In the third aspect of the invention, the expected characteristic in the second aspect of the invention is increased as the engine speed increases.Neutral engine output torque target valueTo reduce the accelerator pedal depression amountNeutral engine output torque target valueBecause we assigned the characteristics of
  Neutral engine output torque target valueHowever, under the same amount of depression of the accelerator pedal, it becomes smaller as the engine speed increases, and the above-mentioned problem related to engine speed increase can be solved more reliably.
[0027]
  In the fourth aspect of the invention, when the continuously variable transmission returns from the neutral state to the power transmission enabled state, the neutral engine is continuously used instead of the target engine output until the friction element for performing the return completes the engagement. Since the engine output torque target value contributes to the engine output torque control, the following effects can be obtained.
[0028]
  In other words, even when the continuously variable transmission returns from the neutral state to the state where power transmission is possible, the engine is in a no-load state until the friction element completes the engagement, and the target engine output is controlled to the engine output control during this period. While this still causes the above-mentioned problem related to the engine speed increase, the neutral engine output torque target value is continuously used for engine output torque control instead of the target engine output torque. It is possible to avoid the rising.
[0029]
  5th inventionIn determining the completion of the engagement of the friction element, it is determined that the engagement of the friction element has been completed when a set time has elapsed since the command for changing the continuously variable transmission from the neutral state to the power transmission enabled state is issued. Because
  It is advantageous that the completion of the engagement of the friction element can be determined at low cost without relying on a rotation sensor.
[0030]
  6th inventionIn determining the completion of the engagement of the friction element, when the torque converter between the continuously variable transmission and the engine is in a lock-up state in which the input / output elements are directly connected, the input speed of the transmission is the engine speed. Since it is judged that the friction element has completed the fastening when
  Even when a torque converter exists between the continuously variable transmission and the engine, it is possible to reliably determine the completion of the engagement of the friction element by the output from the rotation sensor.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a power train of a vehicle having a driving force control device according to an embodiment of the present invention and its control system. The power train is composed of an engine 1 and a continuously variable transmission 2.
Although the engine 1 is constituted by an internal combustion engine, the engine 1 includes a throttle valve 5 that is not linked to an accelerator pedal 3 that is operated by a driver, but is disconnected from the accelerator pedal 3 and the opening degree is electronically controlled by a step motor 4.
Step motor 4 is set to target throttle opening (TVO^*) Set the throttle valve 5 to the target throttle opening TVO by setting it to the rotational position corresponding to the command.^*Thus, the output of the engine 1 can be controlled by factors other than the accelerator pedal operation.
[0032]
The continuously variable transmission 2 is a well-known V-belt type continuously variable transmission, and includes a primary pulley 7 that is drive-coupled to the output shaft of the engine 1 via a torque converter 6 and a starting clutch 15, and a secondary pulley 8 that is aligned with the primary pulley 7. And a V-belt 9 spanned between these two pulleys.
Here, the starting clutch 15 is incorporated in a forward / reverse switching mechanism inserted between the torque converter 6 and the primary pulley 7, and is engaged during forward travel and transmits forward rotation to the primary pulley 7. There is a reverse gear that is fastened and transmits reverse rotation to the primary pulley 7. When the forward start clutch and the reverse start clutch are both released, the primary pulley 7 is disconnected from the torque converter 6 and continuously. Although the transmission is set in a neutral state where power cannot be transmitted, the forward / reverse switching mechanism is not shown in FIG. 1 for convenience, and these clutches are shown as one starting clutch 15.
Therefore, the starting clutch 15 constitutes a friction element that makes the continuously variable transmission neutral or enables power transmission.
Then, a differential gear device 11 is drivingly coupled to the secondary pulley 8 via a final drive gear set 10, and a wheel (not shown) is driven to rotate.
[0033]
For shifting the continuously variable transmission 2, one of the flanges forming the V-grooves of the primary pulley 7 and the secondary pulley 8 is moved closer to the other fixed flange so that the V-groove So that the width of the V-groove can be increased by narrowing or separating the width,
Both movable flanges are connected to the target gear ratio (i^*) Primary pulley pressure P from the hydraulic actuator 12 responding to the command_priAnd secondary pulley pressure P_secBy shifting the position to a position corresponding to the actual transmission ratio of the continuously variable transmission 2, the target transmission ratio i^*It is assumed that the stepless speed change can be made to match
[0034]
Target throttle opening TVO^*And target gear ratio i^*Are calculated by the controller 13 that also performs lock-up control of the torque converter 6 and engagement / release control of the starting clutch 15.
For this reason, the controller 13 sends a signal from the accelerator pedal depression amount sensor 14 for detecting the depression position (accelerator pedal depression amount) APS of the accelerator pedal 3;
A signal from the throttle opening sensor 16 for detecting the throttle opening TVO;
Number of revolutions of primary pulley 7 (primary number of revolutions) N_priA signal from the primary pulley rotation sensor 17 for detecting
Secondary pulley 8 rotation speed (secondary rotation speed) N_secA signal from the secondary pulley rotation sensor 18 for detecting
A signal from the vehicle speed sensor 19 for detecting the vehicle speed VSP;
Engine speed N_eA signal from the engine rotation sensor 20 for detecting
A signal from the inhibitor switch 21 for detecting the selection range of the continuously variable transmission;
A signal from the start clutch engagement determination circuit 22 for determining completion of engagement of the start clutch 15 is input.
[0035]
The starting clutch engagement determination circuit 22 receives a selection range signal from the inhibitor switch 21 and a primary pulley rotation speed (N from the sensor 17 from the controller 13._pri) Signal and engine speed (N_e) Signal and a lockup (L / U) signal for the torque converter 6, it is determined that the start clutch 15 is completely engaged by the configuration shown in FIG. 2 or 3.
[0036]
First, the starting clutch engagement determination circuit of FIG. 2 will be described. In response to the selection range signal, the changeover switch 31 is in the solid line position in the neutral (N) range and is in the broken line position in the traveling (D) range.
Here, when the changeover switch 31 is switched from the solid line position to the broken line position by switching from the neutral (N) range to the traveling (D) range, the initial value TM is displayed in the block 32 during the neutral (N) range._SThe timer TM having been given the subtraction starts the subtraction in the block 33, the timer subtraction value is stored in the block 34, and used for the next subtraction in the block 33.
Thus, when it is detected in block 35 that the timer TM has become 0, that is, switching from the neutral (N) range to the traveling (D) range, the initial value (set time) TM from the moment._SWhen the time elapses, it is determined that the start clutch 15 has been engaged, and a start clutch engagement signal is output.
In this case, the completion of engagement of the starting clutch 15 can be determined without relying on a signal from the rotation sensor, and although there is a slight disadvantage in accuracy, the object can be achieved at low cost.
[0037]
Next, the starting clutch engagement determination circuit of FIG. 3 will be described. In this embodiment, a block 36 and a changeover switch 37 are provided in addition to those of FIG.
The changeover switch 37 is in a solid line position when the lockup (L / U) signal is present and the torque converter 6 is in the lockup state in which the input / output elements are directly connected to each other. Instead of the determination result, a start clutch engagement signal is output according to the determination result of block 36.
The block 36 has a primary pulley rotational speed N_priIs engine speed N_eIs determined, and when it is matched, it is determined that the start clutch 15 has completed the engagement, and a start clutch engagement signal is output.
[0038]
When it is determined by the block 36 that the start clutch 15 is completely engaged, the determination is accurate, but it is possible only when the torque converter 6 is in the lock-up state. Therefore, there is a lock-up (L / U) signal. If not, the changeover switch 37 is set to the position of the broken line, and the neutral (N) range is switched to the traveling (D) range as described above with reference to FIG._SA simple method of outputting a starting clutch engagement signal when the time elapses is used.
In addition, when determining the completion of engagement of the start clutch 15, it may be determined that the engagement is complete when the hydraulic pressure of the start clutch 15 rises to a value indicating the completion of engagement of the clutch.
[0039]
Based on the input information including the start clutch engagement signal from the start clutch engagement determination circuit 22 described above, the controller 13 controls the shift control of the continuously variable transmission 2 and the engine 1 as shown in the functional block diagram of FIG. The throttle opening control is performed as follows, and the vehicle driving force control targeted by the present invention is executed.
Based on the accelerator pedal depression amount APS detected by the sensor 14 and the vehicle speed VSP detected by the sensor 19, the requested axle driving force calculation unit 41 uses, for example, a method described in Japanese Patent Laid-Open No. 7-172217. Required minimum axle drive force T according to driving conditions and driving conditions_SAsk for.
[0040]
The axle rotation speed calculation unit 42 is connected to the secondary rotation speed N detected by the sensor 18._secThat is, the transmission output rotational speed is determined by the gear ratio of the final drive gear set 10 (final drive gear ratio) i._FBy dividing by the current axle speed N_SAsk for.
Then, the requested horsepower calculating unit 43 obtains the requested axle driving force T obtained as described above._SAnd axle speed N_SDemand horsepower HP by multiplying with_SIs calculated.
[0041]
The transmission target input rotational speed / target engine output calculating unit 44 calculates the above-described calculated required horsepower HP based on the characteristic diagram of the engine illustrated in FIG._SEngine speed N to generate the lowest fuel consumption_eTarget value N_e ^*And target engine output T_e ^*Next, the target engine speed N_e ^*Transmission target input speed (target primary speed) N corresponding to_pri ^*Ask for.
[0042]
FIG. 7 shows the engine speed N_eAnd engine output (torque) T_eIs expressed as an equal fuel consumption line α where the fuel consumption rate is the same, and an equal horsepower line β where the output horsepower is the same, and the fuel consumption rate is the best on each equal horsepower line β. The connected minimum fuel consumption line is indicated by δ.
In FIG. 7, the required horsepower HP_SIf the intersection point of one equal horsepower line β and the minimum fuel consumption line δ corresponding to is, for example, the Z point in FIG._SOptimum target engine speed N for generating the minimum fuel consumption_e ^*And target engine output T_e ^*As shown in FIG. 7, the combination can be obtained as a scale value that is lowered from the Z point on the horizontal axis and the vertical axis.
[0043]
In a continuously variable transmission vehicle, the torque converter 6 is in a lock-up state in which the input / output elements are directly connected for most of the time during power transmission. N_pri ^*The target engine speed N_e ^*For convenience, they are treated as the same value.
[0044]
Transmission target input speed N_pri ^*Is input to the target gear ratio calculation unit 45, which calculates the transmission target input rotational speed N._pri ^*The transmission output speed N_secBy dividing by the transmission target input speed N_pri ^*Target gear ratio i corresponding to^*1 is output to the hydraulic actuator 12 as shown in FIG.^*Is achieved, that is, the target input speed N_pri ^*Shift control is performed so that is achieved.
[0045]
On the other hand, the target engine output T from the calculation unit 44_e ^*Is supplied to one input terminal of the changeover switch 46, and the neutral engine output target value T from the neutral engine output target value calculation unit 47 is supplied to the other input terminal of the changeover switch 46._eHWill be supplied.
Then, the calculation unit 47 calculates the accelerator pedal depression amount APS and the engine speed N._eTo the neutral engine output target value T based on the map corresponding to the scheduled characteristics illustrated in FIG._eHSearch for.
Accordingly, the neutral engine output target value T illustrated in FIG._eHThe characteristic of the engine output target value T for the neutral for each accelerator pedal depression amount APS_eHIs engine speed N_eAs a result, the engine output target value is decreased when the continuously variable transmission is neutralized during driving and the engine speed increases, in other words, At this time, the throttle opening control for the engine output control does not increase the throttle opening to what extent, and the problem relating to the engine rotation is prevented.
[0046]
The changeover switch 46 is selected while the selection range is in the neutral (N) range at block 48 (the start clutch 15 is disengaged) or from the neutral (N) range to the travel (D) range at blocks 49 and 50. Even if there is a switching command, the neutral engine output target value T from the calculation unit 47 is set to the solid line position while it is determined that the completion of engagement of the start clutch 15 has not been detected yet._eHEngine output control data T_eTage,
The changeover switch 46 is set to the broken line position while the start clutch 15 to be engaged in the driving (D) range other than the above is completed in the D range, and the target engine output T from the calculation unit 44 is set._e ^*Engine output control data T_eTTo function.
[0047]
Engine output control data T obtained as described above_eTIs input to the target throttle opening calculation unit 51, which calculates the engine output control data T_eTTarget throttle opening TVO^*1 is output to the step motor 4 as shown in FIG. 1, and the throttle valve 5 is set to the target throttle opening TVO.^*The opening degree is controlled so that
[0048]
According to the present embodiment as described above, in the traveling (D) range in which the starting clutch 15 is in the engaged state, the changeover switch 46 is set to the broken line position and the target engine output T from the calculation unit 44 is obtained._e ^*Engine output control data T_eTTherefore, the required axle driving force T_SShift control of the continuously variable transmission (i^*) And throttle opening control of the engine (TVO)^*)It can be performed.
[0049]
By the way, during the N range where the starting clutch 15 is released and the continuously variable transmission is in the neutral state, or while the starting clutch 15 has not yet completed the engagement immediately after switching from the N range to the D range, While the engine is in a no-load state, the changeover switch 46 is set to the solid line position, and the target engine output T from the calculation unit 44 is set._e ^*Instead of the neutral engine output target value T from the calculation unit 47_eHEngine output control data T_eTAnd neutral engine output target value T_eHAs shown in FIG. 10, the engine speed N_eTherefore, the following effects can be achieved.
That is, while the continuously variable transmission is set to the N range during driving and becomes in a neutral state, or when the continuously variable transmission is returned to the D range, the start clutch 15 has not yet been engaged, so the continuously variable transmission is in the neutral state. Increases the engine speed when the engine is in a no-load state, but when the engine speed increases due to the no-load state, the neutral engine output target value T_eHTherefore, at this time, the throttle opening control for engine output control does not increase the throttle opening to what extent, and the problem related to the engine speed increase can be solved. .
[0050]
FIG. 5 shows another embodiment of the present invention. The driving force control apparatus shown in FIG._pri ^*And target engine output T_e ^*Unlike the above-described embodiment, it is obtained as follows.
The required axle drive force T is calculated based on the accelerator pedal depression amount APS and the vehicle speed VSP by the requested axle drive force calculator 41._SIs input to the transmission target input rotational speed calculation unit 61, and the vehicle speed detection value VSP from the sensor 19 is further input to the calculation unit 61.
[0051]
In the transmission target input rotational speed calculation unit 61, the requested axle driving force T_SAnd the vehicle speed VSP based on the characteristic curve of the engine shown in FIG. 7 and the map corresponding to the data shown in FIG._SEngine speed N for generating low fuel consumption_eTarget value N_e ^*Next, this target engine speed N_e ^*Transmission target input speed (target primary speed) N corresponding to_pri ^*And the target gear ratio i in the calculation unit 45^*Contributes to the calculation of
[0052]
Here, the data of FIG. 9 will be explained. This data is obtained from the characteristic diagram of the engine shown in FIG. 7 as follows, and the vehicle speed VSP and the axle driving force T_SAnd engine speed N_eAnd the relationship.
Although FIG. 7 has already been described, the engine speed N_eAnd engine output (torque) T_eIs expressed as an equal fuel consumption line α where the fuel consumption rate is the same, and an equal horsepower line β where the output horsepower is the same, and the fuel consumption rate is the best on each equal horsepower line β. The connected minimum fuel consumption line is indicated by δ.
As shown in FIG. 8, the individual points on the minimum fuel consumption line δ shown in FIG._eTo vehicle speed VSP and engine output (torque) T_eAxle driving force T_SThe vehicle speed VSP and engine output (torque) T, which are transferred to the two-dimensional coordinates replaced with_eIs obtained as shown in FIG.
[0053]
And the engine speed N on the characteristic diagram for each gear ratio_eWhen the points where the two are equal are plotted, a certain engine speed N_eIn this case, the engine speed is as shown by A in FIG._eEvery vehicle speed VSP and axle drive force T_SThe minimum fuel consumption line δ in FIG. 7 can be represented by a line as shown in FIG.
In FIG. 9, for the sake of convenience, the engine speed N_eThe target engine speed N_e ^*It was written as.
Such vehicle speed VSP and axle driving force T_SAnd target engine speed N_e ^*According to the data representing the relationship between the current vehicle speed VSP and the axle driving force T_SFor example, the case where the combination with the point Z corresponds to the point Z will be described._STarget engine speed N to generate the minimum fuel consumption_e ^*Can be obtained as a parameter value (engine speed) related to a line passing through the Z point in FIG.
In a continuously variable transmission vehicle, the torque converter 6 is in a lock-up state in which the input / output elements are directly connected for most of the time during power transmission. However, the transmission target input rotational speed (target primary rotational speed) N_pri ^*The target engine speed N_e ^*Are treated as the same value.
[0054]
On the other hand, in the present embodiment, the primary pulley rotation speed (transmission input rotation speed) N detected by the sensor 17 in the wheel drive system actual transmission ratio calculation unit 62._priAxle rotation speed N from the calculation unit 42_SWheel drive system actual transmission ratio i by dividing by_TAnd
In the target engine output calculation unit 63, the requested axle driving force T from the calculation unit 41 is obtained._SWheel drive system actual transmission ratio i_TThis required axle drive force T by dividing by_STarget engine output (torque) T for achieving minimum fuel consumption_e ^*Seeking
This target engine output (torque) T_e ^*Is supplied to the corresponding input terminal of the changeover switch 46.
Where target engine output (torque) T_e ^*7 is a value corresponding to the torque scale value of the line drawn from the Z point on the vertical axis from the Z point, and is substantially the same as in FIG.
[0055]
Also in the present embodiment, in the traveling (D) range in which the starting clutch 15 is in the engaged state, the changeover switch 46 is set to the broken line position and the target engine output T from the calculation unit 63 is set._e ^*Engine output control data T_eTTherefore, the required axle driving force T_SShift control of the continuously variable transmission (i^*) And throttle opening control of the engine (TVO)^*)It can be performed.
[0056]
Further, during the N range where the starting clutch 15 is released and the continuously variable transmission is in the neutral state, or while the starting clutch 15 has not yet completed the engagement immediately after switching from the N range to the D range, While the engine is in the no-load state, the changeover switch 46 is set to the solid line position, and the target engine output T from the calculation unit 63 is set._e ^*Instead of the neutral engine output target value T from the calculation unit 47_eHEngine output control data T_eTTherefore, when the engine speed increases due to such a no-load state, the throttle opening control for engine output control does not increase the throttle opening to what extent, and the engine rotation speed increases. The problem can be solved.
[0057]
FIG. 6 shows still another embodiment of the present invention. In this embodiment, the neutral engine output target value calculation unit 47 basically follows the configuration of FIG. Is a neutral engine output target value T by another method._eHIs to ask for.
In other words, in the present embodiment, the neutral engine output target value calculation unit 47 performs the target engine output (torque) T obtained by the target engine output calculation unit 63._e ^*Engine speed N_eAccordingly, as in the above-described embodiment, the neutral engine output target value T is limited to a value that can solve the problem related to the engine speed increase at no load._eHAnyway.
In this case, the neutral engine output target value T_eHCan be obtained simply and inexpensively, and the same operational effects as in the above-described embodiments can be achieved economically.
[0058]
In each of the embodiments, the case where the traveling range is the D range has been described. However, even when the traveling range is the reverse (R) range, the start clutch 15 is completely engaged during the N → R selection operation. Target engine output (torque) T_e ^*Instead of neutral engine output target value T_eHIt goes without saying that the same effect can be obtained by contributing to engine output (throttle opening) control.
[0059]
In each embodiment, the transmission target input rotational speed (target primary rotational speed) N_pri ^*Shift control to achieve the required axle drive force T when no load is applied, as in the case of load_SSo that the target gear ratio i is selected when D → N is selected.^*Therefore, when returning to the D range again by the N → D select operation, there is no change in the gear ratio, and a smooth shift can be maintained.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic explanatory view showing a power train of a continuously variable transmission equipped with a driving force control device according to an embodiment of the present invention together with its control system.
FIG. 2 is an explanatory block diagram showing an example configuration of a starting clutch engagement determination circuit in the same embodiment;
FIG. 3 is an explanatory block diagram showing another configuration example of the start clutch fastening determination circuit.
4 is a functional block diagram of shift control and throttle opening control for driving force control executed by a controller in the embodiment shown in FIG. 1; FIG.
FIG. 5 is a functional block diagram of shift control and throttle opening control for driving force control according to the embodiment of the present invention.
FIG. 6 is a functional block diagram of speed change control and throttle opening control for driving force control according to still another embodiment of the present invention.
FIG. 7 is an engine characteristic diagram showing an iso-fuel consumption line, an iso-horsepower line, and a minimum fuel consumption line on a two-dimensional coordinate defined by an engine speed axis and an engine output torque axis.
FIG. 8 is a diagram when the minimum fuel consumption line is rewritten as a relationship diagram between the vehicle speed and the axle driving force for each gear ratio.
FIG. 9 is a relationship diagram between vehicle speed and axle driving force, represented as a diagram connecting points at which the input rotation speed becomes equal for each gear ratio on the diagram of FIG. 9;
10 is a change characteristic diagram of a neutral engine output target value obtained by a neutral engine output target value calculation unit in the embodiment of FIGS. 4 and 5. FIG.
[Explanation of symbols]
1 engine
2 continuously variable transmission
3 Accelerator pedal
4 Step motor
5 Electronically controlled throttle valve
6 Torque converter
7 Primary pulley
8 Secondary pulley
9 V belt
10 Final drive gear set
  11 Differential gear unit
  12 Hydraulic actuator
  13 Controller
  14 Accelerator pedal depression sensor
  15 Starting clutch (friction element)
  16 Throttle opening sensor
  17 Primary pulley rotation sensor
  18 Secondary pulley rotation sensor
  19 Vehicle speed sensor
  20 Engine rotation sensor
  21 Inhibitor switch
  22 Start clutch engagement determination circuit
  41 Required axle driving force calculator
  42 Axle speed calculator
  43 Required horsepower calculator
44 Transmission target input speed and target engine output calculator
  45 Target gear ratio calculator
46 selector switch
  47 Neutral engine output target value calculator
  48 Neutral range judgment block
  49 N → D select detection block
50 Start clutch non-engagement determination block
  51 Target throttle opening calculator
61 Transmission target input speed calculator
  62 Wheel drive system actual gear ratio calculator
  63 Target engine output calculator

Claims (6)

A vehicle equipped with a power train that combines an engine whose output can be arbitrarily changed depending on factors other than the accelerator pedal operation, and a continuously variable transmission,
Find the optimal combination of target engine speed and target engine output torque to achieve the required axle driving force determined by the driving state and driving conditions of the vehicle,
A driving force control device for a vehicle that controls the transmission of the continuously variable transmission so as to be a transmission target input rotational speed corresponding to the target engine rotational speed and controls the output of the engine so as to be the target engine output torque. In
When the continuously variable transmission is set in a neutral state where power cannot be transmitted while the vehicle is running, the target engine output torque is limited according to the engine speed so that the engine speed does not rise even in the neutral state. Is a neutral engine output torque target value, and instead of the target engine output torque, the neutral engine output torque target value contributes to the engine output control. 2. The vehicle driving force control device according to claim 1, wherein the neutral engine output torque target value is obtained from a predetermined characteristic from an accelerator pedal depression amount and an engine speed. Characterized in that in claim 2, characteristic of the expected are those assigned the characteristics of the neutral engine output torque target value for the accelerator pedal depression amount to the neutral engine output torque target value with increasing engine speed is reduced A vehicle driving force control device. In any one of Claims 1 thru | or 3, when the continuously variable transmission returns from a neutral state to a power transmission enabled state, the friction element for performing the return continues until the fastening is completed. A vehicle driving force control device characterized in that a neutral engine output torque target value contributes to the engine output torque control. 5. The structure according to claim 4, wherein the friction element is determined to be engaged when a set time elapses after a command to change the continuously variable transmission from a neutral state to a power transmission enabled state is issued. A vehicle driving force control device. 6. When the torque converter between the continuously variable transmission and the engine is in a lock-up state in which the input / output elements are directly connected to each other, the input speed of the transmission coincides with the engine speed. A driving force control device for a vehicle, characterized in that it is determined that the friction element has completed fastening.

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