JP3633389B2 - Driving force control device for continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving force control device for a continuously variable transmission, and more particularly, to improve control characteristics when switching between driving force control and engine brake control.
[0002]
[Prior art]
For a vehicle equipped with a continuously variable transmission, a combination that can achieve the optimum fuel consumption is calculated from the combination of engine torque and engine speed (or gear ratio) that achieves the driving force necessary to maintain the vehicle speed command value. Thus, a driving force control device for a continuously variable transmission that controls the throttle valve opening and the gear ratio is disclosed (for example, see the Society of Automotive Engineers of Japan, Vol. 48, No. 10, 1994). Specifically, the engine output command value is calculated based on the driving force command value and the vehicle speed, and the equal output line corresponding to the output command value and the optimum fuel consumption on the optimum fuel consumption driving line defined by the engine torque and the engine rotation speed are calculated. The engine torque and the engine speed (or gear ratio) at the intersection with the driving line are determined.
[0003]
In addition, when driving on the downhill road where the slope changes with the engine brake force with the accelerator pedal released, if the vehicle acceleration exceeds a predetermined value, the correction amount of the engine speed command value corresponding to the vehicle speed and acceleration is set. A shift control device for a continuously variable transmission is disclosed that corrects the engine rotational speed command value to suppress vehicle speed fluctuations on downhill roads (see, for example, Japanese Patent Laid-Open No. 9-100903).
[0004]
[Problems to be solved by the invention]
By the way, when the latter shift control device is combined with the former drive power control device for continuously variable transmission to perform shift control on a downhill road, the former drive force control device controls the engine output based on the output command value. In contrast, the latter shift control device controls the engine braking force based on the engine rotational speed command value. Therefore, when the engine output, that is, the driving force control and the engine braking control are switched, the engine output changes in a stepped manner. There is a possibility of feeling uncomfortable.
[0005]
An object of the present invention is to smoothly switch between driving force control and engine brake control.
[0006]
[Means for Solving the Problems]
Referring to FIG. 1 showing the configuration of an embodiment of the invention and FIGS. 2 and 3 showing the operation of the embodiment, the present invention will be described. The present invention includes vehicle speed detecting means 7 for detecting the vehicle speed ( S1), an accelerator detection means 8 for detecting the depression amount of the accelerator pedal (S2), a first calculation means 13 for calculating an engine output command value for normal travel based on the vehicle speed and the depression amount of the accelerator pedal (S3) ), An accelerator state detecting means 13 for detecting the depressed state and the released state of the accelerator pedal based on the depressed amount of the accelerator pedal (S4), and an engine for maintaining the acceleration of the vehicle at substantially 0 when the opened state of the accelerator pedal is detected. Second calculation means 13 for calculating an engine rotation speed command value for brake control (S5), engine brake characteristics and engine rotation for engine brake control Third calculation means 13 for calculating the engine output command value for engine brake control based on the degree command value (S7, S8), and when the depression state of the accelerator pedal is detected, the engine output command value for normal travel is finally When the engine output command value is determined and the accelerator pedal release state is detected , if the engine output command value for engine brake control becomes smaller than the engine output command value for normal driving, the final engine output command value is set to the normal engine output command value for normal driving. When the engine output command value for engine brake control becomes larger than the engine output command value for normal travel, the final engine output command value is changed from the engine output command value for engine brake control to the normal output for engine brake control. engine output command value determining to switch to the engine output command value In step 13 and (S9), when the final engine output command value is a positive value, the engine rotational speed command value is determined based on the engine optimum fuel consumption driving characteristic and the final engine output command value, and the final engine output command value is negative. In the case of a value, engine operating point determining means 13 for determining an engine rotational speed command value based on the engine brake characteristics and the final engine output command value (S10 to S14), and an engine for controlling the engine based on the engine rotational speed command value The control means 14 (S16 to S17), the continuously variable transmission control means 13 and 15 for calculating the gear ratio command value based on the engine rotational speed command value and the vehicle speed and controlling the continuously variable transmission (S16 to S17). ).
[0007]
In the section of the means for solving the above-described problem, a diagram of an embodiment is used for easy understanding of the description. However, the present invention is not limited to the embodiment.
[0008]
【The invention's effect】
According to the present invention, even when a continuously variable transmission driving force control device that performs driving force control during normal traveling is combined with a gear ratio control device that performs engine braking control on a downhill road, And engine brake control on downhill roads can be switched smoothly.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the configuration of an embodiment.
The set switch 1 is a switch for setting the current vehicle speed to the vehicle speed command value and starting the vehicle speed control. The acceleration switch 2 is a switch for increasing the set vehicle speed, and the coast switch 3 is a switch for reducing the set vehicle speed. The cancel switch 4 is a switch for canceling the vehicle speed control, and the brake switch 5 is a switch that operates when the foot brake is operated. When the brake switch 5 is actuated, the vehicle speed control is canceled in the same manner as when the cancel switch 4 is operated.
[0010]
The crank angle sensor 6 outputs a pulse train signal having a cycle corresponding to the engine speed, and the vehicle speed sensor 7 outputs a pulse train signal having a cycle corresponding to the vehicle speed. By measuring the pulse interval of these pulse train signals or the number of pulses per predetermined time, the engine rotational speed Ne [rpm] and the vehicle speed Vsp [km / h] can be detected. Further, the accelerator sensor 8 detects an accelerator pedal depression amount Acc as the occupant's acceleration intention. This accelerator pedal depression amount Acc is used for normal control when the vehicle speed control is released. The primary rotation sensor 9 outputs a pulse train signal having a period corresponding to the rotation speed of a primary pulley of a belt type continuously variable transmission 11 described later. By measuring the pulse interval of the pulse train signal or the number of pulses per predetermined time, the rotational speed of the primary pulley of the continuously variable transmission 11, that is, the input shaft rotational speed of the continuously variable transmission 11 can be detected.
[0011]
The lean combustion engine 10 is controlled so that the engine torque matches the command value by intake air amount control by the throttle valve actuator 10a, fuel injection amount control by the injector 10b, and ignition timing control by the spark plug 10c. . In the lean combustion engine 10, a fuel cut prohibition state and a fuel cut permission state are switched, and an ideal air-fuel ratio (stoichiometric) state and a lean combustion air-fuel ratio state are switched. Furthermore, the opening / closing timing of the intake / exhaust valve changes discontinuously by switching between the low rotation cam and the high rotation cam.
[0012]
The belt-type continuously variable transmission 11 is controlled so that the gear ratio matches the command value by changing the radii of the primary pulley and the secondary pulley by hydraulic control. The belt type continuously variable transmission 11 includes a torque converter 12 with a lockup clutch for starting. The continuously variable transmission is not limited to a belt type, and for example, a toroidal type continuously variable transmission may be used. The belt of the belt type continuously variable transmission is not limited to a metal belt, and for example, a composite dry belt can be used.
[0013]
The vehicle speed controller 13, engine torque controller 14, and gear ratio controller 15 each include a microcomputer and its peripheral components, various actuator drive circuits, and the like, and communicate with each other via a communication circuit. The vehicle speed controller 13 performs drive force control during normal travel and gear ratio control on a downhill road, and outputs an engine torque command value, an engine speed command value, and a gear ratio command value. The torque controller 14 performs throttle valve opening control based on the engine torque command value of the engine 10 and switching control of engine operating states such as air-fuel ratio, intake / exhaust valve opening / closing timing, fuel cut inhibition / permission. Further, the gear ratio controller 15 controls the gear ratio of the continuously variable transmission 11 based on the gear ratio command value.
[0014]
In this embodiment, the engine output, that is, the driving force of the vehicle is controlled on the normal traveling road, and the engine braking force is controlled on the downhill road. First, a normal travel engine output command value Lacc is calculated based on the vehicle speed Vsp and the accelerator pedal depression amount Acc. When the accelerator pedal is depressed, the normal travel engine output command value Lacc is determined as the final engine output command value L. On the other hand, when the accelerator pedal is released, an engine rotation speed command value Nerb for engine brake control is calculated and converted into an engine output command value Leb for engine brake control based on the engine brake characteristics when the throttle valve is fully closed. Then, the smaller one of the normal running engine output command value Lacc and the engine brake control engine output command value Leb is determined as the final engine output command value L.
[0015]
Next, when the final engine output command value L is a positive value, the intersection of the equal output line corresponding to the output command value L and the optimum fuel consumption driving line on the optimum fuel consumption driving line defined by the engine torque and the engine speed. The engine torque and the engine speed at are determined as engine operating points. On the other hand, when the final engine output command value L is a negative value, the final engine output command value L is inversely converted to the engine rotational speed command value Ne according to the engine brake characteristics when the throttle valve is fully closed, and the engine rotational speed command value Ne is decide. Thereby, it is possible to smoothly switch between driving force control and engine brake control during normal traveling without causing a step in the engine output.
[0016]
2 and 3 are flowcharts showing a driving force control program according to an embodiment. The operation of the embodiment will be described with reference to these flowcharts.
[0017]
The microcomputer of the vehicle controller 13 executes this driving force control program every predetermined time, for example, 10 msec. In step 1, the vehicle speed sensor 7 detects the vehicle speed Vsp, and in the subsequent step 2, the accelerator sensor 8 detects the accelerator pedal depression amount Acc. In step 3, an engine output command value Lacc for normal running is calculated. Specifically, a table of output command values Lacc for the vehicle speed and accelerator pedal depression amount as shown in FIG. 4 is set in advance, and output commands corresponding to the vehicle speed detection value Vsp and the accelerator pedal depression amount detection value Acc are set. The value Lacc is looked up.
[0018]
In step 4, it is detected whether the accelerator pedal depression amount Acc is equal to or greater than a predetermined value Accth, that is, whether the accelerator pedal is depressed. When Acc ≧ Accth and the accelerator pedal is depressed, the routine proceeds to step 9, and when Acc <Accth and the accelerator pedal is not depressed, the routine proceeds to step 5.
[0019]
When the accelerator pedal is released, an engine speed command value Nerb for engine brake control is calculated in step 5. For the calculation of the engine speed command value Nerb for engine brake control, for example, a method disclosed in JP-A-9-100903 can be used. That is, a table of the correction amount ΔDSR per unit time of the engine rotation speed command value Nerb corresponding to the acceleration of the vehicle as shown in FIG. 5 is set in advance, and the acceleration detection value detected by the acceleration sensor or the vehicle speed Vsp A correction amount ΔDSR corresponding to the acceleration calculation value calculated by the change is subjected to a table calculation, and this correction amount ΔDSR is added to the previously calculated engine rotation speed command value to obtain a new engine rotation speed command value Nerb. FIG. 5 shows the correction amount ΔDSR per 5 msec with respect to the vehicle acceleration. When calculating the engine speed command value Nerb for the first time, the engine speed command value Nerb is calculated by adding the correction amount ΔDSR to the actual engine speed Ne detected by the crank angle sensor 6.
[0020]
In step 6, it communicates with the engine controller 14 to confirm whether or not it is in a fuel cut state. When the engine 10 is in the fuel cut prohibition state, the process proceeds to step 7 where the engine output command value Leb for engine brake control in the fuel cut prohibition state is calculated. A control engine output command value Leb is calculated.
[0021]
FIG. 6 shows engine brake characteristics of the engine 10 measured in advance. In the figure, “emblem” refers to engine braking.
When the engine 10 is in the fuel cut prohibited state (state 1) with the throttle valve fully closed, the engine speed control value Nerb for engine brake control and the engine brake characteristic line in the fuel cut prohibited state (state 1) with the throttle valve fully closed The engine output command value Leb is obtained from an iso-output line passing through the intersection with the. On the other hand, when the engine 10 is in the fuel cut state (state 2) with the throttle valve fully closed, the engine speed control value Nerb for engine brake control and the engine brake characteristic line in the fuel cut state (state 2) with the throttle valve fully closed The engine output command value Leb is obtained from an iso-output line passing through the intersection with the.
[0022]
In step 9, the final engine output command value L is determined as follows.
[Expression 1]
When Acc ≧ Accth (accelerator pedal depression), L = Lacc,
If Acc <Accth (accelerator pedal release) and Leb> Lacc, then L = Lacc,
When Acc <Accth (accelerator pedal release) and Leb ≦ Lacc, L = Leb
Here, Accth is a predetermined value of the accelerator pedal depression amount described above. When the accelerator pedal is released, the smaller one of the normal travel engine output command value Lacc and the engine brake control engine output command value Leb is selected.
[0023]
In step 10, it is confirmed whether or not the final engine output command value L is 0 or more. When L ≧ 0, the routine proceeds to step 11 where an engine rotation speed command value Ner for driving force control is calculated. Specifically, the engine speed at which the fuel consumption is minimized while realizing the engine output command value L (positive value) using the engine characteristic diagram 7 representing the optimum fuel consumption driving line for realizing the engine output with the minimum fuel consumption. The speed command value Ner is searched. Actually, the engine rotation speed that realizes the engine output with the minimum fuel consumption is tabulated in advance, and the engine rotation speed command value Ner corresponding to the engine output command value L is calculated by a table calculation.
[0024]
On the other hand, when L <0, the engine speed command value Ner for realizing the engine output command value L (Lacc or Leb) determined in step 9 is calculated in steps 12 to 14. First, in step 12, communication with the engine controller 14 is performed, and it is confirmed whether or not the fuel is cut. When the engine 10 is in the fuel cut prohibited state, the process proceeds to step 13 to calculate the engine speed control value Ner for engine brake control in the fuel cut prohibited state. Specifically, the engine speed command value Ner that realizes the engine output command value L (negative value) when the throttle valve is fully closed and the fuel cut prohibited state (state 1) is searched using the engine brake characteristic FIG. Actually, the engine rotational speed with respect to the engine output in the throttle valve fully closed and fuel cut prohibited state (state 1) is previously tabulated, and the engine rotational speed command value Ner corresponding to the engine output command value L is tabulated and calculated. do it.
[0025]
When the engine 10 is in the fuel cut state, the routine proceeds to step 14, where the engine speed control value Ner for engine brake control in the fuel cut state is calculated. Specifically, the engine speed command value Ner that realizes the engine output command value L (negative value) when the throttle valve is fully closed and the fuel cut state (state 2) is searched using the engine brake characteristic diagram 8. Actually, the engine rotation speed with respect to the engine output in the throttle valve fully closed and fuel cut state (state 2) is previously tabulated, and the engine rotation speed command value Ner corresponding to the engine output command value L is calculated by a table calculation. That's fine.
[0026]
In step 15 after calculating the engine speed command value Ner for drive control or engine brake control, the engine speed command value Ner is determined by the speed ratio range that the continuously variable transmission 11 can take, the engine 10, and the like. When the rotation speed limit value is exceeded, a limit value is set to the engine rotation speed command value Ner. In the subsequent step 16, the engine torque command value Ter and the gear ratio command value Gcvtr are calculated by the following equations.
[Table 1]
Gcvtr = Ner · Rt / Vsp / Gf,
Ter = Tor / Gcvt / Gf
Here, Gf is the final reduction ratio, and Gcvt is the actual gear ratio.
[0027]
In step 17, the engine speed command value Ner and the engine torque command value Ter are output to the engine controller 14, and the speed ratio command value Gcvtr is output to the speed ratio controller 15. The engine controller 14 controls the engine 10 according to the engine rotation speed command value Ner and the engine torque command value Ter. The gear ratio controller 15 controls the continuously variable transmission 11 according to the gear ratio command value Gcvtr.
[0028]
FIG. 9 is a time chart showing the driving force control result of the embodiment. In the figure, “emblem” refers to engine braking.
The accelerator pedal depression amount Acc is smaller than the predetermined value Accth, that is, the accelerator pedal depression amount is substantially 0 (accelerator pedal release), and the engine output command value Leb for engine brake control is the engine output command value Lacc for normal travel. When it becomes smaller (time t1), the final engine output command value L is switched from the engine output command value Lacc for normal travel to the engine output command value Leb for emblem control. Next, when the engine output command value Leb for engine brake control becomes larger than the engine output command value Lacc for normal travel (time t2), the final engine output command value L is switched from Leb for emblem control to Lacc for normal travel. At these switching times t1 and t2, the engine output command value does not change stepwise, and the switching between the driving force control and the engine brake control is performed smoothly.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment.
FIG. 2 is a flowchart illustrating a driving force control program according to an embodiment.
FIG. 3 is a flowchart illustrating the driving force control program according to the embodiment following FIG. 2;
FIG. 4 is a diagram showing an example of a normal traveling engine output command value Acc map;
FIG. 5 is a diagram showing a correction amount table per unit time of an engine rotation speed command value with respect to vehicle acceleration.
FIG. 6 is a graph showing engine brake characteristics.
FIG. 7 is a graph showing an optimum fuel consumption characteristic of the engine.
FIG. 8 is a graph showing engine brake characteristics.
FIG. 9 is a diagram illustrating a driving force control result according to one embodiment.
[Explanation of symbols]
1 set switch 2 acceleration switch 3 coast switch 4 cancel switch 5 brake switch 6 crank angle sensor 7 vehicle speed sensor 8 accelerator sensor 9 primary rotation sensor 10 engine 10a throttle valve actuator 10b injector 10c spark plug 11 continuously variable transmission 12 torque converter 13 Vehicle speed controller 14 Engine controller 15 Gear ratio controller

Claims (1)

Vehicle speed detection means for detecting the vehicle speed;
Accelerator detecting means for detecting the amount of depression of the accelerator pedal;
First computing means for computing an engine output command value for normal running based on the vehicle speed and the accelerator pedal depression amount;
An accelerator state detecting means for detecting a depressed state and an opened state of the accelerator pedal based on the amount of depression of the accelerator pedal;
Second calculating means for calculating an engine speed command value for engine brake control for maintaining the acceleration of the vehicle at substantially zero when detecting the release state of the accelerator pedal ;
Third computing means for computing an engine output command value for engine brake control based on engine brake characteristics and the engine speed command value for engine brake control;
When the depression state of the accelerator pedal is detected, the engine output command value for normal travel is determined as the final engine output command value, and when the accelerator pedal is released, the engine output command value for engine brake control is determined for the normal travel. When the engine output command value is smaller than the engine output command value, the final engine output command value is switched from the normal travel engine output command value to the engine brake control engine output command value, and the engine brake control engine output command value is changed to the normal travel command value. An engine output command value determining means for switching the final engine output command value from the engine output command value for engine brake control to the engine output command value for normal running when the engine output command value is greater than
When the final engine output command value is a positive value, an engine rotational speed command value is determined based on the engine optimum fuel efficiency operation characteristic and the final engine output command value. When the final engine output command value is a negative value, Engine operating point determining means for determining an engine rotation speed command value based on the engine brake characteristics and the final engine output command value;
Engine control means for controlling the engine based on the engine rotation speed command value;
A continuously variable transmission driving force control comprising: a continuously variable transmission control means for calculating a gear ratio command value based on the engine rotational speed command value and the vehicle speed and controlling the continuously variable transmission. apparatus.

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