JP4517719B2 - Control device for maintaining vehicle speed at low load of power train - Google Patents

Description

  The present invention relates to control of a power train in which a continuously variable transmission capable of continuously changing a gear ratio, such as a V-belt system or a toroidal system, and an engine composed of an internal combustion engine are combined.

Traditionally, as a power train that forms the main part of the drive system of a vehicle, the gear ratio that is the ratio of the input rotation speed and the output rotation speed is determined in advance as a predetermined value such as 1st speed, 2nd speed, 3rd speed, In general, a stepped automatic transmission that selects a gear from among a plurality of predetermined gears and executes a gear shifting operation and an engine that is an internal combustion engine are combined.
In this conventional power train, for example, when accelerating, the engine speed is temporarily increased to a high speed at a constant gear and then upshifted by one gear, and the engine speed is increased again under a new gear. The D range control of the stepped automatic transmission that repeats the operation of pulling up to the rotation and further upshifting by one gear stage (the reverse operation is performed during deceleration traveling) is executed.
On the other hand, in recent years, a V-belt type or toroidal type continuously variable transmission which can be continuously changed without intermittently switching by setting the gear ratio, which is the ratio between the input rotational speed and the output rotational speed, to several stages. Vehicle power trains that have been connected to the engine and engine have been developed and put into practical use.
This continuously variable transmission does not generate an acceleration / deceleration shock when switching the gear ratio, and the riding comfort performance and fuel efficiency are improved.
As a power train equipped with a continuously variable transmission, a power train described in, for example, Patent Document 1 is known.
The above-described conventional power train is characterized in that smooth acceleration / deceleration performance is realized by changing the gear ratio steplessly. Therefore, its spread has been increasing in recent years. This smooth acceleration / deceleration performance means that during acceleration / deceleration traveling, the engine speed is prevented and the gear ratio is changed.
In other words, compared to a stepped automatic transmission whose gear ratio is fixed at a constant speed, a continuously variable transmission changes the gear ratio even if the throttle opening of the engine changes slightly. In the power train equipped with the vehicle, the vehicle speed is easy to change.
Japanese Patent Laid-Open No. 11-141668

For this reason, the following problems arise in a vehicle equipped with the conventional power train. In other words, when driving at a constant speed on a flat paved road with low running resistance, the driving force of the wheels is not so large and the load on the engine is low. What is necessary is just to keep in the open state (low opening degree target value). In order to keep the throttle opening at the low opening target value, the driver must hold the position where the accelerator pedal is slightly depressed. Is unable to maintain a slight depression of the accelerator pedal, and the actual throttle opening becomes larger or smaller than the low opening target value. Therefore, the vehicle feels like accelerating or decelerating.
For this reason, if the driver tries to keep a constant speed on a flat pavement or the like, an accelerator pedal return operation is performed in order to correct the acceleration travel feeling, and then an accelerator pedal depression operation is performed in order to correct the deceleration travel feeling. Hunting such as performing, returning and stepping on is repeated.

To supplement this problem, when the vehicle travels, traveling resistance such as wheel rolling resistance, road surface gradient resistance, and air resistance acts on the vehicle. When the driving force of the wheel generated between the wheel and the road surface is larger than the traveling resistance, a marginal driving force is generated and the vehicle travels at an accelerated speed. On the other hand, when the driving force of the wheel is smaller than the running resistance, the marginal driving force becomes a negative value and the vehicle travels at a reduced speed. Further, when the running resistance and the wheel driving force are equal, the margin driving force is just 0, and the vehicle travels at a constant speed. This marginal driving force F is expressed by the following equation.
F = Te * ip * if * r-R (1)
Here, Te is the engine torque, ip is the gear ratio in the transmission, if is the final reduction ratio, r is a coefficient, and R is the running resistance.

The running resistance R in the equation (1) increases in proportion to the vehicle speed and the climbing gradient, and decreases on a flat paved road having no road surface gradient.
The engine torque Te in the equation (1) is determined by the throttle opening TVO and the engine speed Ne.
According to the equation (1), when the driver desires constant speed driving, the marginal driving force F may be set to 0, and the driver opens and closes the throttle opening of the engine by the accelerator operation, and the engine torque Te May be adjusted to the target engine torque value corresponding to the running resistance R corresponding to the target vehicle speed.
In particular, when the running resistance R is small, such as when driving on a flat paved road with no road surface gradient, the engine torque Te is also small. The engine torque Te must be adjusted to the target engine torque value with the accelerator pedal depression amount to be linked kept small.

  Further, when the driver desires acceleration driving, the marginal driving force F> 0 may be set, and the driver increases the throttle opening of the engine by the accelerator operation, and the target engine corresponding to the target acceleration with the engine torque Te. What is necessary is just to match with a torque value.

In this regard, with the conventional power train that changes the engine torque Te with a stepped automatic transmission and transmits it to the wheels, the engine torque Te is temporarily increased to a high output at a constant shift stage for acceleration. Must be raised.
In addition, in the stepped automatic transmission, the transmission ratio ip and the final reduction ratio if are fixed in equation (1), and the contribution of the engine torque Te contributing to the marginal driving force F is large.
Therefore, the target value of the engine torque Te and the target throttle opening required for acceleration and constant speed driving are large, and the driver can easily adjust the engine torque Te to the target engine torque value by operating the accelerator. In a conventional powertrain equipped with a transmission, the driver was likely to keep the vehicle speed constant.

However, in the conventional power train in which the engine torque Te is changed by the continuously variable transmission and transmitted to the wheels, the engine speed is gradually changed to prevent the engine from rotating at high speed in order to achieve smooth acceleration / deceleration performance.
That is, in the continuously variable transmission, since the speed ratio ip varies in the equation (1), the contribution of the engine torque Te that contributes to the marginal driving force F is small, and it is directed to the low throttle opening region. The vehicle speed changes due to changes in the throttle opening.
Therefore, the target value of the engine torque Te and the target throttle opening required for constant speed driving and acceleration driving are small,
When driving at a constant speed on a flat pavement with no road surface gradient, for example, when the engine load is low, the driver must The engine torque Te must be adjusted to the target engine torque value by accurately accelerating the pedal depression amount, which is not easy for a driver who is not accustomed to the accelerator operation or a driver who has difficulty in walking.

In this way, drivers who are unfamiliar with accelerator operation cannot maintain the accelerator pedal depression amount at a low opening target value such as 1/16 or 1/32, and try to maintain constant speed running on a flat paved road. If so, hunting of the accelerator operation described above is performed and drivability is deteriorated.
In addition, the hunting and acceleration / deceleration running described above, although minute, has problems such as unintentionally accumulating fatigue for the driver, impairing ride performance for the passenger, and adversely affecting fuel consumption.

  In a power train in which engine output is changed by a continuously variable transmission and transmitted to a wheel, a driver who desires constant speed operation performs an accelerator operation so that the accelerator pedal depression amount is kept constant at a low opening. Even if it cannot be performed, the purpose is to realize a constant speed travel without deteriorating drivability by preventing acceleration operation hunting and repeated acceleration / deceleration travel of the vehicle. .

For this purpose, the control device for maintaining the vehicle speed at low load of the power train according to the present invention is as described in claim 1,
An engine that includes a throttle that is electronically controlled based on a driver's accelerator operation amount, and that generates an output in accordance with the throttle opening;
In a power train comprising a continuously variable transmission that transmits the output from the engine to the drive wheel side,
Vehicle speed holding intention detecting means for detecting the intention of the driver who desires constant speed driving from the driving state of the vehicle under a driving state in which the engine is lightly loaded;
When the vehicle speed holding intention detecting means detects the intention of traveling at a constant speed, it comprises throttle sensitivity reducing means for reducing the sensitivity of changing the throttle opening with respect to the accelerator operation amount,
The vehicle speed holding intention detecting means is provided for a driver when the accelerator operation amount is in a range of a predetermined opening or less set according to the vehicle speed within a range of 1/8 or less and the vehicle speed is substantially constant. The repetition of the accelerator pedal depression operation is detected, and the driver's intention to travel at a constant speed is detected when the repetition reaches a predetermined number of times.

Or as claimed in claim 5,
In the above power train, when the vehicle speed holding intention detecting means detects the intention of traveling at a constant speed, the vehicle includes a low load vehicle speed holding upshift detecting means for prohibiting an upshift of the continuously variable transmission,
The vehicle speed holding intention detecting means is provided for a driver when the accelerator operation amount is in a range of a predetermined opening or less set according to the vehicle speed within a range of 1/8 or less and the vehicle speed is substantially constant. The repetition of the accelerator pedal depression operation is detected, and the driver's intention to travel at a constant speed is detected when the repetition reaches a predetermined number of times.

According to the control device of the present invention, since the change sensitivity of the throttle opening is reduced, the driver cannot maintain the attitude of stepping on the accelerator pedal slightly, and even when the depression amount fluctuates, The fluctuation of the throttle opening becomes small, and it becomes possible to travel at a substantially constant speed.
Or, to prevent upshifting, even if the driver cannot hold the accelerator pedal slightly and the amount of depression changes slightly, the gear ratio will change steplessly and the vehicle speed will change. Can be suppressed.

  Therefore, the above-described hunting of the accelerator operation can be prevented, and a driver who is unfamiliar with the accelerator operation can travel at a constant speed even on a flat paved road or the like having a low travel resistance. In addition, it is possible to prevent the driver from unintentionally accumulating fatigue, and to prevent the passenger from deteriorating the ride comfort performance, thereby preventing the fuel efficiency from being adversely affected.

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 including a control device according to an embodiment of the present invention and a control system thereof. The power train is composed of an engine 1 and a continuously variable transmission 2.
Although the engine 1 is a gasoline engine, the throttle valve 5 is not mechanically connected to the accelerator pedal 3 operated by the driver, but is separated from the throttle pedal 5 by the throttle valve actuator 4 (throttle opening). ) Is electronically controlled.

The operation amount of the throttle actuator 4 is controlled by an engine controller 14 that responds to a command related to a target throttle opening tTVO determined by the general controller 16 as will be described later, whereby the opening of the throttle valve 5 is controlled by the target throttle opening. The output of the engine 1 is basically controlled so as to become a value corresponding to the accelerator pedal operation in accordance with tTVO, but can also be controlled by factors other than the accelerator pedal operation as necessary.
The engine controller 14 not only performs the throttle opening control via the throttle actuator 5 but is not shown in the figure, but other fuel injection amount control, fuel cut control, ignition timing, etc., which are necessary for the operation of the engine 1. Control shall also be performed.

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, a secondary pulley 8 that is aligned with the primary pulley 7, and both A V-belt 9 is provided between pulleys.
Then, the differential gear device 11 is drivingly coupled to the secondary pulley 8 via the final drive gear set 10, and a wheel (not shown) is rotationally driven by these.

The speed change operation of the continuously variable transmission 2 is such that, among the flanges forming the V-grooves of the primary pulley 7 and the secondary pulley 8, one movable flange is brought relatively close to the other fixed flange to make the V-groove width Narrowing the width or conversely increasing the V groove width,
The stroke positions of both movable flanges are determined by the primary pulley pressure Ppri and the secondary pulley pressure Psec from the transmission control hydraulic circuit 12.

  The transmission control hydraulic circuit 12 includes a step motor 13 as a transmission actuator, and the transmission controller 15 is driven to a step position STP corresponding to a target transmission ratio tRATIO described later, so that the continuously variable transmission 2 is realized. The continuously variable transmission can be performed so that the gear ratio matches the target gear ratio tRATIO.

It is assumed that the target throttle opening tTVO command to the engine controller 14 and the target gear ratio tRATIO command to the transmission controller 15 are respectively obtained by the control described later.
Therefore, the general controller 16 includes a signal from the accelerator opening sensor 17 that detects the depression position of the accelerator pedal 3 (also referred to as the accelerator pedal depression amount or the accelerator opening) APO,
A signal from an engine rotation sensor 18 that detects an engine rotation speed (equivalent to the input rotation speed to the continuously variable transmission 2) Npri from the ignition signal of the engine 1 or the rotation speed of the output shaft of the engine 1;
A signal from the vehicle speed sensor 19 that detects the vehicle speed VSP from the number of rotations of the wheel is input.

In normal control, the general controller 16 reads these input information at regular control intervals by a scheduled interruption, and realizes normal gear ratio control and normal throttle opening control based on these input information.
In normal gear ratio control, a target input rotation speed is obtained with reference to a known gear ratio map (not shown). Then, the target speed ratio tRATIO is obtained from the target input speed and the vehicle speed, and the speed ratio control is realized via the step motor 13 so that the actual speed ratio becomes the target speed ratio. In a well-known transmission ratio map (not shown), a predetermined transmission line for setting a target input rotation speed with respect to the vehicle speed is set for each throttle opening.
In normal throttle opening control, the target throttle opening tTVO is obtained from the accelerator pedal depression amount APO based on the target throttle opening map (not shown) that is proportional to the accelerator pedal depression amount APO. The opening control of the throttle valve 5 is realized via the throttle actuator 4 so that the throttle opening becomes the target throttle opening tTVO.

In addition to the normal control described above, the general controller 16 executes the control program shown in FIG. 2 to reduce the throttle opening in a traveling environment where the driving load of the engine 1 is low, such as a flat pavement road. It is determined whether or not to execute a control for maintaining a low-load constant-speed traveling, which will be described later, that travels at a constant speed while being held in the opening range.
In step S1 of FIG. 2, the above-described normal control is performed to obtain the target throttle opening tTVO and the target gear ratio tRATIO.

In the next steps S2 to S4, it is detected whether or not the vehicle is traveling at a low load constant speed based on the accelerator pedal depression amount APO and the vehicle speed VSP.
First, in step S2, referring to the low load constant speed traveling determination map shown in FIG.
It is determined whether the vehicle speed VSP is within the range of diagonal lines (20-100 km / h). If the vehicle speed VSP is within the range of 20 to 100 km / h (Yes), the process proceeds to step S3. On the other hand, if it is out of range (No), the process returns to step S1 and the running state is continuously monitored.
In the next step S3, it is determined whether or not the accelerator pedal 3 is depressed. If the accelerator pedal 3 is depressed (Yes), the process proceeds to step S4. On the other hand, if it is not depressed (No), the process returns to step S1 and the running state is continuously monitored.
In the next step S4, referring to the low load constant speed traveling determination map shown in FIG. 3, it is determined whether or not the accelerator pedal depression amount APO is in the low opening range represented by the oblique lines (0/8 to 1/8). to decide. For example, if the accelerator pedal depression amount APO is a low opening range of 0/8 to 0.5 / 8 while traveling at a constant speed of 40 km / h, it is determined that the vehicle is traveling at a low load constant speed (Yes), Proceed to step S5. On the other hand, if the accelerator pedal depression amount APO is 0.5 / 8 or more while traveling at a constant speed of 40 km / h, it is determined that the vehicle is not traveling at a low load constant speed (No), and the process returns to step S1 and continues to travel. Monitor status.

In step S5, the vehicle speed VSP detected in step S2 is stored in the depressed vehicle speed A. Then, the vehicle speed B and the vehicle speed C, which are threshold values obtained by adding and subtracting a predetermined value to the vehicle speed A at the time of depression, are set. The relationship between these A, B, and C is illustrated in FIG.
In the next step S6, it is determined whether or not the low load constant speed travel flag is 0. If the low load constant speed travel flag is 0, the process proceeds to step S7. S7 is omitted and the process proceeds to step S8.
In step S7, the count timer CNT is set to zero.

In step S8, it is determined whether the driver has lifted his or her foot from the accelerator pedal 3 (whether the accelerator pedal is released). If the accelerator pedal is not released (No), the process returns to step S6. If the accelerator pedal is released (Yes), the process proceeds to step S9, and the vehicle speed when the accelerator pedal is released (referred to as vehicle speed D when released) is within the range of vehicle speed B and vehicle speed C, which are the above threshold values. Judge whether there is. If the vehicle speed D when the foot is released is not within the range of the vehicle speed B and the vehicle speed C (No), it is determined that the vehicle is not traveling at a low load constant speed, and the process proceeds to step S17.
In step S17, the count timer CNT is reset to 0, the low load constant speed running flag is reset to 0, and the process proceeds to step S18.
In step S18, A, B, and C stored in step S5 are cleared, and the process returns to step S1.

On the other hand, as shown in FIG. 4 (b), if the vehicle speed D when the foot is released is within the range of the vehicle speed B and the vehicle speed C (Yes) as shown in step S9, the driver desires low-load constant speed traveling. Since it is considered, the process proceeds to step S10, the count timer CNT is incremented, and the low load constant speed travel flag is set to 1.
In the next step S11, it is determined whether or not the count timer CNT is 2. If it has not reached 2 (No), the process proceeds to step S19, and it is determined whether or not the accelerator pedal 3 released in step S8 is depressed. If not depressed (No), since the accelerator pedal is released, the process returns to step S9 to continue monitoring whether or not the driver desires a low load constant speed traveling.
In the present embodiment, the driving state of the vehicle is monitored until the count timer CNT becomes 2, but if the driver wants to make a more accurate determination as to whether or not he / she desires a low-load constant-speed driving, the driving state is more than 2. Just set it to a large number.
On the other hand, if the accelerator pedal 3 is being depressed (Yes), the process proceeds to step S20.
In step S20, it is determined whether or not the accelerator pedal depression amount APO is in the low opening range with reference to the low load constant speed travel determination map shown in FIG. If the accelerator pedal depression amount APO is in the low opening range (Yes), the process returns to step S6. On the other hand, if it is not within the region (No), it is determined that the vehicle is not running at a low load constant speed (No), and the count timer CNT is reset to 0 in the next step S21, and the low load constant speed running flag is set to 0. Reset to step S22.
In step S22, A, B, and C stored in step S5 are cleared, and the process returns to step S1.

If the count timer CNT has reached 2 in step S11 (Yes), the process proceeds to step S12, and the current speed D when the foot is released is read again. This is because, since the accelerator pedal 3 has been released since step S8, the foot release time vehicle speed D stored in step S9 may vary. Then, it is determined again whether or not the vehicle speed D when the foot is released is within the range of the threshold values B to C.
If the vehicle speed D when the foot is released is not within the ranges of the vehicle speed B and the vehicle speed C (No), it is determined that the vehicle is not traveling at a low load constant speed, and the process proceeds to step S17.
On the other hand, if the step-off vehicle speed D is within the range of the vehicle speed B and the vehicle speed C (Yes) in step S9, it is considered that the driver desires low-load constant speed travel, so the process proceeds to step S13. It is determined whether or not the accelerator pedal 3 released in step S8 is depressed. If the accelerator pedal is being released (No), the process returns to step S12 and the above processing is continued. On the other hand, when the accelerator pedal 3 is depressed (Yes), the process proceeds to step S14, and it is determined whether or not the accelerator pedal depression amount APO is in the low opening degree region.

If the accelerator pedal depression amount APO is not in the low opening range at step S14 (No), it is determined that the vehicle is not traveling at a low load constant speed, and the process proceeds to step S17.
On the other hand, when it is in the low opening range (Yes), the process proceeds to step S15.

When the process proceeds to step S15, it is determined that the driver depresses or releases the accelerator pedal 3 or performs a hunting operation during low load constant speed traveling as described above. Is the holding vehicle speed E. Then, the vehicle speed B and the vehicle speed C, which are threshold values obtained by adding a predetermined value to the holding vehicle speed E, are set again. The magnitude relationship between E, B, and C is illustrated in FIG.
In the next step S16, it is comprehensively determined that the driver desires the low load constant speed running at the holding vehicle speed E, and the process proceeds to the control for holding the low load constant speed running, and this flowchart is ended.

  Control for maintaining the low load constant speed running is performed by controlling the opening degree of the throttle valve 5 and by controlling the gear ratio of the continuously variable transmission 2.

FIG. 5 is a flowchart showing throttle opening control during low load constant speed traveling.
First, in step S31, a target throttle opening tTVO necessary for the holding vehicle speed E is calculated. Since the target throttle opening tTVO required for the holding vehicle speed E depends on the characteristics of the vehicle type such as the engine type and the vehicle body shape, the R / L vehicle speed-target throttle opening determination map shown in FIG. The target throttle opening tTVO is calculated by referring to this map.
FIG. 6 shows the target throttle opening that must be maintained by the engine in order for the vehicle to maintain a constant vehicle speed (also referred to as road load R / L vehicle speed) under a certain traveling resistance. The axis indicates the R / L vehicle speed VSP, and the vertical axis indicates the target throttle opening tTVO.
For example, when the holding vehicle speed E = 42 km / h, the target throttle opening tTVO is 0.25 / 8 (also referred to as 0.5 / 16 or 1/32).

  In the next step S32, the sensitivity of changing the throttle opening with respect to the accelerator pedal depression amount APO is lowered. Specifically, the accelerator pedal depression amount APO is assumed to have hysteresis, and the vehicle speed-hysteresis addition depression amount setting map shown in FIG. 7 is referred to. The target throttle opening is fixed to the target throttle opening tTVO calculated in step S31 regardless of the pedal depression amount APO. For example, when the holding vehicle speed E is 42 km / h, if the accelerator pedal depression amount APO is in the range of 0/8 to 1.45 / 8, the target throttle opening tTVO is calculated in step S31 regardless of the accelerator pedal depression amount APO. 0.25 / 8.

In the next step S33, it is determined whether or not the current vehicle speed VSP is within the range of the threshold values B and C set in step S15, and it is determined whether or not the retained vehicle speed E is maintained.
When the holding vehicle speed E is not maintained (No), such as a brake operation by the driver, the present control is terminated and the normal control is restored.

On the other hand, if the holding vehicle speed E is maintained (Yes), the process proceeds to step S34 to determine whether or not the accelerator pedal 3 is depressed. If the accelerator pedal 3 is not depressed (No), the process returns to step S33 and the current vehicle speed VSP is continuously monitored. On the other hand, if it is depressed (Yes), the process proceeds to step S35.
In step S35, it is determined whether the accelerator pedal depression amount APO is equal to or less than the hysteresis addition accelerator pedal depression amount set in step S32. When the driver depresses the accelerator pedal 3 beyond the hysteresis addition accelerator pedal depression amount set in step S32 (No), this control is terminated and the normal control is resumed.

  On the other hand, if the hysteresis addition accelerator pedal is not more than the depression amount (Yes), the process proceeds to step S36 to determine whether or not the depression speed ΔAPO of the accelerator pedal 3 is less than a predetermined threshold value F. If the driver depresses or releases the accelerator pedal quickly after exceeding a predetermined threshold F (No), the driver determines that he / she does not desire constant speed driving at the holding vehicle speed E and terminates this control. The normal control is resumed.

On the other hand, if it is less than the predetermined threshold value F (Yes), it is determined that the driver desires constant speed traveling at the holding vehicle speed E, and the routine proceeds to step S37, where the target throttle opening calculated in step S31 is obtained. The opening control of the throttle valve 5 is executed so as to be tTVO, and the process returns to step S31 and the above control is repeated.
As a result, the vehicle speed VSP can be held constant (held vehicle speed E) regardless of the accelerator pedal depression amount APO.

FIG. 8 is a flowchart showing gear ratio control during low-load constant-speed traveling.
First, in step S41, the speed ratio of the continuously variable transmission 2 is limited not to be upshifted, and a target speed ratio tRATIO command is output to the transmission controller 15 to execute speed ratio control. Specifically, for example, the current speed ratio α is set to the target speed ratio tRATIO, and the current speed ratio α is fixed to the current speed ratio α as shown in FIG. To do.
Note that with respect to FIG. 9, the gear ratio is a linear gradient connecting the origin in FIG. 9 and the combination point of the vehicle speed VSP and the engine speed (also the input speed of the continuously variable transmission 2) Npri. Yes, the steepest slope is the lowest gear and the gentlest slope is the highest gear. The current speed ratio α is, for example, when the holding vehicle speed E = 42 km / h and the engine speed Npri = 1500 rpm, as shown in FIG. 9, the origin, the combination point of VSP = 42 km / h and Npri = 1500 rpm The slope of a straight line connecting
In FIG. 9, if the combination point is moved to the upper side (steep slope) than the gear ratio α, the downshift is performed, and if the combination point is moved to the lower side (slow gradient), the upshift is performed. δ represents a coast shift line when the accelerator pedal depression amount is 0 (during coasting).
By fixing the speed ratio as it is, execution of smooth speed change control which is a characteristic of the continuously variable transmission 2 is prohibited, and the vehicle speed VSP is prevented from changing due to a slight change in the accelerator pedal depression amount APO. be able to.

  Alternatively, limiting the speed ratio of the continuously variable transmission 2 so as not to upshift may be specifically downshifting the speed ratio so that the current speed ratio α becomes β in FIG. . By downshifting, the change width of the vehicle speed VSP can be reduced and the vehicle speed VSP can be prevented from changing due to a slight change in the accelerator pedal depression amount APO.

  Alternatively, to limit the speed ratio of the continuously variable transmission 2 so as not to upshift, specifically, for example, from the current speed ratio α, the vehicle speed VSP is maintained regardless of the engine speed Npri as indicated by γ in FIG. The transmission ratio may be controlled so as to be maintained at E. As a result, the vehicle speed VSP can be kept constant regardless of the accelerator pedal depression amount APO.

In the next step S42, it is determined whether or not the current vehicle speed VSP is within the range of the threshold values B and C set in step S15, and it is determined whether or not the retained vehicle speed E is maintained.
When the holding vehicle speed E is not maintained (No), such as a brake operation by the driver, the present control is terminated and the normal control is restored.

  On the other hand, if the holding vehicle speed E is maintained (Yes), the process proceeds to step S43, and it is determined whether the accelerator pedal depression amount APO is equal to or less than the hysteresis addition accelerator pedal depression amount set in step S32. When the driver depresses the accelerator pedal 3 beyond the hysteresis addition accelerator pedal depression amount set in step S32 (No), this control is terminated and the normal control is resumed.

  On the other hand, when the hysteresis addition accelerator pedal depression amount is kept below (Yes), the process proceeds to step S44, and it is determined whether or not the depression speed ΔAPO of the accelerator pedal 3 is less than a predetermined threshold value F. If the driver depresses or releases the accelerator pedal quickly after exceeding a predetermined threshold F (No), the driver determines that he / she does not desire constant speed driving at the holding vehicle speed E and terminates this control. The normal control is resumed.

On the other hand, if it is less than the predetermined threshold value F (Yes), it is determined that the driver desires constant speed traveling at the holding vehicle speed E, and the routine proceeds to step S45, where the target throttle opening calculated in step S41 is calculated. The opening degree control of the throttle valve 5 is executed so as to become tTVO, and the above control is repeated by returning to step S41.
As a result, the vehicle speed VSP can be held constant (held vehicle speed E) regardless of the accelerator pedal depression amount APO.

By the way, according to the above-described embodiment, the driver travels at a constant speed with the vehicle speed A at the time of stepping, the vehicle speed D at the time of stepping off, and the holding vehicle speed E during the low load constant speed driving with a low load on the engine 1. When the driver performs the hunting operation of the accelerator pedal 3 when desired, the control shifts from the normal control to the control for maintaining the low load constant speed travel, and the target throttle opening with respect to the accelerator pedal depression amount APO is shifted. By reducing the change sensitivity of degree tTVO,
The driver does not need to maintain a state where the accelerator pedal 3 is depressed by a small amount by an accurate accelerator operation.
In other words, by making the accelerator pedal depression amount larger than the actual throttle opening, for example, when the target throttle opening is 0.25 / 8, the driver does not need to keep the accelerator pedal depression amount at 0.25 / 8. What is necessary is just to keep in the range of 8-1.4 / 8.
Therefore, even a driver who cannot maintain the position where the accelerator pedal is slightly depressed is kept substantially constant at the holding vehicle speed E if the amount of depression of the accelerator pedal is maintained at an approximate low opening without repeating hunting. High speed driving can be realized.
As a result, fatigue does not accumulate unintentionally for the driver, and it is possible to prevent the passenger from deteriorating the ride comfort performance and to prevent adverse effects on fuel consumption.

To reduce the change sensitivity of the target throttle opening tTVO with respect to the accelerator pedal depression amount APO described above, specifically, a hysteresis is applied, and the throttle opening is reduced to the low opening shown in FIG. 6 regardless of the accelerator pedal depression amount APO. It is something that you keep.
In the wording of claim 1 of the present invention, “reducing the throttle opening change sensitivity relative to the accelerator operation amount” is not limited to the throttle opening shown in FIG. It may take into account the environment. Alternatively, even if the accelerator pedal depression amount APO changes greatly, even if the throttle opening changes slightly, it is possible to realize the constant speed travel that is the object of the present invention.

Further, according to the present embodiment, the upper limit value shown in FIG. 7 is set for the accelerator pedal depression amount APO when the throttle opening is held at the low opening shown in FIG. Because
Regardless of the accelerator pedal depression amount APO, the vehicle speed VSP can be kept constant, and the driver can easily drive at a constant vehicle speed E and drive by increasing the accelerator pedal depression amount APO. The person can easily end the control for maintaining the low load constant speed running and return to the normal control.

Furthermore, according to the present embodiment, in executing the control for maintaining the low load constant speed running, the upshift of the gear ratio of the continuously variable transmission 2 is prohibited.
This is a characteristic of the continuously variable transmission 2 and prohibits the execution of smooth shift control executed in the normal control. Thereby, it is possible to prevent the vehicle speed VSP from changing due to a slight change in the accelerator pedal depression amount APO.

  In this embodiment, the throttle opening degree control and the gear ratio control are used together in the control for maintaining the low load constant speed running, and the holding speed E is effectively maintained. However, the object of the present invention can be achieved.

  Specifically, prohibiting the upshift of the transmission ratio of the continuously variable transmission 2 is to fix the transmission ratio to the current transmission ratio α as shown in FIG. By fixing the speed ratio, it is possible to prohibit the execution of the smooth speed change control, which is a characteristic of the continuously variable transmission 2, and to prevent the vehicle speed VSP from changing due to a slight change in the accelerator pedal depression amount APO. .

Alternatively, the gear ratio may be downshifted to be β in FIG. 9, and by downshifting, the change in the vehicle speed VSP with respect to the change in the engine input rotational speed Npri is reduced, and the accelerator pedal depression amount APO is slightly reduced. It is possible to prevent the vehicle speed VSP from changing due to a change.
Therefore, it is not necessary for the driver to accurately hold the accelerator pedal depression amount in the low opening range, and the vehicle speed VSP can be kept substantially constant.

Alternatively, the gear ratio is controlled so that the continuously variable transmission 2 outputs the retained vehicle speed E as the vehicle speed VSP regardless of the engine speed Npri that is the input rotation speed to the continuously variable transmission 2 so as to be γ in FIG. Accordingly, the vehicle speed VSP can be kept constant regardless of the engine input rotational speed Npri.
Therefore, the vehicle speed VSP can be kept substantially constant for the driver without worrying about the accelerator pedal depression amount APO.

  Further, according to the present embodiment, referring to the low load constant speed traveling determination map shown in FIG. 3, the accelerator pedal depression amount APO is in the low opening range, and steps S3, S8, S13, S19 shown in FIG. In this process, the driver repeats the input operation and the return operation to the accelerator pedal 3 by the count timer CNT, and when the repeat operation reaches twice in step S11, the driver's intention to drive at a constant speed is detected. Then, by shifting to the control for maintaining the low load constant speed traveling, it is possible to accurately detect the driver's intention of traveling at a constant speed.

  Further, according to the present embodiment, the driver applies the accelerator pedal 3 to the accelerator pedal 3 in the processes of steps S3, S8, S13, and S19 shown in FIG. 2 when the vehicle speed is within the range of the threshold values B and C. The repetition of the input operation and the return operation is detected by the count timer CNT, and the constant vehicle speed desired by the driver can be accurately detected by setting the latest depressing vehicle speed in step S15 as the holding vehicle speed E.

1 is a system diagram showing a vehicle power train according to an embodiment of the present invention, together with its control system. It is a flowchart which shows the control program performed in order to detect whether the driver | operator desires constant speed driving | running | working in the low opening degree area | region of accelerator pedal depression amount. 3 is a low load constant speed travel determination map referred to in the control program. FIG. 6 is a diagram schematically showing the magnitude relationship between various vehicle speeds set to detect the holding vehicle speed E in the control program, wherein (a) is a stepping-on vehicle speed A and thresholds B, C based on this, (B) shows the vehicle speed D when the foot is in the range of the threshold value, and (c) shows the holding vehicle speed E and the threshold values B and C based thereon. It is a flowchart which shows the control program regarding target throttle opening calculation execution for hold | maintaining low load constant speed driving | running | working. 4 is an R / L vehicle speed-target throttle opening degree determination map referred to in order to calculate a target throttle opening degree in the control program. 5 is a vehicle speed-hysteresis addition depression amount setting map that is referred to in order to add hysteresis to the accelerator pedal depression amount APO in the control program. It is a flowchart which shows the control program regarding the target gear ratio performed in order to hold | maintain low load constant speed driving | running | working. It is a shift diagram which shows the target gear ratio performed with the control program. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Continuously variable transmission 3 Accelerator pedal 4 Throttle actuator 5 Strot valve 6 Torque converter 7 Primary pulley 8 Secondary pulley 9 V belt 10 Drive gear set 11 Differential gear device 12 Shift control hydraulic circuit 13 Step motor 14 Engine controller 15 Transmission Controller 16 General controller 17 Accelerator opening sensor 18 Engine rotation sensor 19 Vehicle speed sensor

Claims (9)

In a power train comprising an engine that generates an output corresponding to a throttle opening that is electronically controlled based on the accelerator operation amount of the driver, and a continuously variable transmission that transmits the output from the engine to the drive wheel side,
Vehicle speed holding intention detecting means for detecting the intention of the driver who desires constant speed driving from the driving state of the vehicle under a driving state in which the engine is lightly loaded;
When the vehicle speed holding intention detecting means detects the intention of traveling at a constant speed, it comprises throttle sensitivity reducing means for reducing the sensitivity of changing the throttle opening with respect to the accelerator operation amount,
The vehicle speed holding intention detecting means is provided for a driver when the accelerator operation amount is in a range of a predetermined opening or less set according to the vehicle speed within a range of 1/8 or less and the vehicle speed is substantially constant. A control device for maintaining a vehicle speed at a low load of a power train, which detects repetition of an accelerator pedal depression operation of the vehicle and detects a driver's intention of traveling at a constant speed when the repetition reaches a predetermined number of times. In the control apparatus for vehicle speed maintenance at the time of low load of the power train according to claim 1,
The throttle sensitivity lowering means calculates a throttle opening for maintaining the vehicle speed required to maintain the constant vehicle speed desired by the driver when the vehicle speed holding intention detecting means detects the driver's intention to travel at a constant speed. With means,
When the vehicle speed holding intention detecting means detects the driver's intention to travel at a constant speed, the throttle opening is held at the vehicle speed holding throttle opening regardless of the accelerator operation amount. A control device for maintaining the vehicle speed when the train is under low load. In the control device for holding the vehicle speed at low load of the power train according to claim 2,
The throttle sensitivity reducing means holds the throttle opening at the vehicle speed maintaining throttle opening only when the accelerator operation amount is within a hysteresis range determined for each constant vehicle speed, regardless of the accelerator operation amount. A control device for maintaining a vehicle speed at a low load of a power train, characterized by being operated. In the control apparatus for vehicle speed holding | maintenance at the time of the low load of the power train of any one of Claims 1-3,
A power having a low load vehicle speed holding upshift prohibiting means for prohibiting an upshift of the continuously variable transmission when the vehicle speed holding intention detecting means detects a driver's intention to travel at a constant speed. A control device for maintaining the vehicle speed when the train is under low load. In a power train comprising an engine that generates an output corresponding to a throttle opening that is electronically controlled based on the accelerator operation amount of the driver, and a continuously variable transmission that transmits the output from the engine to the drive wheel side,
Vehicle speed holding intention detecting means for detecting the intention of the driver who desires constant speed driving from the driving state of the vehicle under a driving state in which the engine is lightly loaded;
When the vehicle speed holding intention detecting means detects the intention of traveling at a constant speed, the vehicle speed holding intention detecting means includes an upshift prohibiting means for holding the vehicle speed at low load that prohibits upshifting of the continuously variable transmission,
The vehicle speed holding intention detecting means is provided for a driver when the accelerator operation amount is in a range of a predetermined opening or less set according to the vehicle speed within a range of 1/8 or less and the vehicle speed is substantially constant. A control device for maintaining a vehicle speed at a low load of a power train, which detects repetition of an accelerator pedal depression operation of the vehicle and detects a driver's intention of traveling at a constant speed when the repetition reaches a predetermined number of times. In the control apparatus for vehicle speed maintenance at the time of low load of the power train according to claim 4 or 5,
The low-load vehicle speed holding upshift prohibiting means fixes the speed ratio of the continuously variable transmission, and the power train low-load vehicle speed holding control device. In the control apparatus for vehicle speed maintenance at the time of low load of the power train according to claim 4 or 5,
The low-load vehicle speed holding upshift prohibiting means downshifts the continuously variable transmission, and the powertrain low-load vehicle speed holding control device. In the control device for maintaining the vehicle speed at low load of the power train according to claim 7,
The low-load vehicle speed holding upshift prohibiting means is a constant vehicle speed desired by the driver when the vehicle speed holding intention detecting means detects the driver's intention to travel at a constant speed during the downshift of the continuously variable transmission. A control device for maintaining a vehicle speed at a low load of a power train, wherein the speed ratio of the continuously variable transmission is controlled so as to be maintained. In the control device for holding the vehicle speed at low load of the power train according to any one of claims 1 to 8,
The vehicle speed holding intention detecting means detects the driver's intention to travel at a constant speed, and then detects further repetition of the driver's accelerator pedal depression operation, and the vehicle speed when the detection is made is determined by the driver A control device for maintaining a vehicle speed at a low load of a power train, characterized by having a constant vehicle speed.

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