JP4072464B2 - Vehicle speed limiter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle speed limiting device (speed limiter device), and more particularly to a vehicle speed limiting device suitable for a vehicle equipped with an engine that uses gaseous fuel such as compressed natural gas (CNG).
[0002]
[Prior art]
In a diesel engine vehicle, the vehicle acceleration is not restricted to the upper limit of the vehicle speed limit, but when a constant speed request is generated, the fuel injection amount of the engine is controlled so that the actual vehicle speed is maintained at the target vehicle speed at that time. Is disclosed (Patent Document 1).
[0003]
In a compressed natural gas engine (CNG engine) in which a diesel engine is converted to an Otto cycle engine, a throttle valve (main throttle valve) that responds to an accelerator pedal, a sub-throttle valve that is driven (opened and closed) by a drive device, and an engine speed And a means for controlling the maximum throttle opening so that the engine torque according to the above does not exceed a predetermined value (Patent Document 2). The sub-throttle valve is normally kept fully open, and when the engine speed exceeds the point where the maximum engine output is achieved, the main throttle opening exceeds the maximum throttle opening. Thus, the opening is gradually reduced, and the engine is controlled to be fully closed when the engine speed reaches the maximum allowable speed. In other words, in constant speed running (see Patent Document 1), the actual vehicle speed is not controlled to be kept at the target vehicle speed (a constant value), but the engine output is limited based on the relationship with the mechanical strength of the engine. .
[0004]
[Patent Document 1]
JP-A-8-216729 [Patent Document 2]
Japanese Utility Model Publication No. 6-73346
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle speed limiting device capable of restricting acceleration of a vehicle to a predetermined value by using a sub-throttle valve in a vehicle equipped with an Otto cycle engine such as a CNG engine.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, in a vehicle equipped with an engine as a prime mover having a main throttle valve that responds to accelerator operation and means for supplying a fuel amount corresponding to the intake air amount upstream of the main throttle, the engine is sucked into the engine. As a means to control the sub throttle valve so that the actual vehicle speed does not exceed the limit vehicle speed, the opening range where the vehicle speed limit does not work and the opening degree that makes the vehicle speed limit effective Means to obtain the basic sub-throttle opening according to the actual vehicle speed and the main throttle opening from the characteristic that has a sudden change region of the opening at the boundary with the region, and the determination vehicle speed that is lower than the limit vehicle speed by a predetermined value or more Means for feedback control of the correction amount of the sub-throttle opening so that the deviation between the limit vehicle speed and the actual vehicle speed converges to 0 at the time of the basic sub-slot Means for controlling the sub-throttle valve based on the opening degree and the amount of feedback correction, and when the failure of the means for detecting the actual vehicle speed is judged, the control of the sub-throttle valve is switched to a sub-throttle opening degree according to the engine speed. As means for performing backup control, means for detecting the engine speed, means for detecting the intermittent transmission of power from the engine to the drive wheels, and means for determining whether the actual vehicle speed detecting means is faulty based on these detection signals And a means for switching the control of the sub-throttle valve at the time of the failure determination and controlling the sub-throttle opening according to the engine speed obtained from the characteristics for backup based on the detection signal of the engine speed. It is characterized by that .
[0007]
According to a second aspect of the present invention, in the vehicle speed limiting device according to the first aspect of the present invention, the engine that is obtained from the backup characteristics based on the detection signal of the engine speed by switching the control of the sub-throttle valve when determining the failure of the vehicle speed detecting means. The means for controlling the sub-throttle opening in accordance with the rotational speed includes a determination rotational speed set to a lower limit value of the engine rotational speed that may reach a determined vehicle speed lower than the limited vehicle speed by a predetermined value, and a detection signal for the engine rotational speed. And sub-throttle valve backup control is executed under the condition of engine speed ≧ determined rotation .
[0008]
A third invention is characterized in that in the vehicle speed limiting device according to the first or second invention, the fuel of the engine is a gaseous fuel such as compressed natural gas .
[0011]
【The invention's effect】
In the first to third aspects of the invention , the sub-throttle valve and its control means can create a vehicle speed governor characteristic that suppresses the amount of air-fuel mixture into the engine so that the actual vehicle speed does not exceed the limit vehicle speed. The amount of air-fuel mixture to the engine is adjusted according to the opening of the main throttle valve that is linked to the accelerator operation in a vehicle speed range where the vehicle speed restriction does not work. Meanwhile, the sub-throttle valve is controlled to an opening (for example, a fully opened state) that does not hinder the air-fuel mixture amount corresponding to the main throttle opening.
[0012]
If a failure occurs in the vehicle speed detection means, the actual vehicle speed detection signal necessary for the control of the suspension throttle valve cannot be obtained, and the normal function of vehicle speed restriction is impaired. Therefore, in the first to third aspects of the invention , since the sub-throttle valve is provided with a backup control means, if it is determined that the vehicle speed detection means has failed, the backup control is performed from the vehicle speed limit control based on the actual vehicle speed. Therefore, the sub-throttle valve is controlled based on the engine speed. By this backup control, it is possible to ensure a normal function of limiting the vehicle speed even when the vehicle speed detecting means is out of order.
[0013]
In this case, it is possible to accurately determine whether or not the vehicle speed detection means is out of order from detection of the engine speed and intermittent transmission of power. That is, when the engine speed is detected and the power transmission is in contact (power is transmitted from the engine to the drive wheels), the vehicle is in a running state, and if the actual vehicle speed is not detected, the vehicle speed It is determined that the detection means is faulty. At the time of this failure determination, the sub-throttle valve is switched from the control based on the basic sub-throttle opening and the feedback correction to the backup control based on the engine speed. Therefore, the sub-throttle opening degree is controlled according to the engine speed, and the acceleration of the vehicle can be suppressed below the limit vehicle speed .
[0014]
In normal times when the actual vehicle speed detection means functions normally , the actual vehicle speed is determined by having a sudden change region of the opening between the opening region where the vehicle speed restriction does not work and the opening region where the vehicle speed restriction works. A basic sub-throttle opening corresponding to the main throttle opening is obtained, and the sub-throttle valve is controlled to an opening that adds a feedback correction amount to the basic opening. Due to the characteristics of the basic sub-throttle opening, the acceleration of the vehicle can suppress the increase in the actual vehicle speed beyond the limit vehicle speed with good response. In addition, because the sub-throttle valve opens and closes around the basic sub-throttle opening according to the actual vehicle speed and the main throttle opening by the feedback correction, it is stable to maintain the limited vehicle speed while maintaining the accelerator operation amount constant. Traveling is also possible.
[0015]
Since the transmission is interposed in the power transmission system of the vehicle, the number of revolutions transmitted from the engine to the drive wheels varies depending on the shift speed (gear ratio). In the second invention or the third invention, Since the lower limit value of the engine speed that may reach the determination vehicle speed lower than the predetermined value is set as the determination rotation, the engine is controlled by executing the backup control on the condition that the engine rotation speed (detection value) ≧ the determination rotation. Without converting the rotation speed into a vehicle speed value, the acceleration of the vehicle can be surely regulated below the limit vehicle speed.
[0016]
In the third aspect of the invention , when gaseous fuel such as CNG (compressed natural gas) is used as the engine fuel, the acceleration characteristic is gentler than that of the gasoline engine. However, a vehicle speed limiting characteristic suitable for such a vehicle is obtained. Be able to.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration for explaining application to a vehicle equipped with a CNG engine. A main throttle valve 1 is interposed in an intake passage 3 of the engine, and a sub-throttle valve 2 is interposed downstream thereof. The main throttle valve 1 (throttle valve) is connected to an accelerator pedal in the cab and is adjusted to an opening corresponding to the amount of pedal depression. The sub-throttle valve 2 is opened and closed by a step motor 4 (drive means), and an engine control unit 5 for controlling the drive means 4 is provided as will be described later. A fuel supply device (not shown) is provided, and a fuel amount corresponding to the intake air amount is supplied upstream of the main throttle valve 1 so as to generate an air-fuel mixture having a substantially constant air-fuel ratio.
[0018]
The engine control unit 5 includes an opening range where the vehicle speed limit is not effective and an opening range where the vehicle speed limit is applied based on a detection signal (actual vehicle speed) of the vehicle speed sensor and a detection signal (main throttle opening) of the throttle opening sensor. Means (basic sub-throttle opening control means 11) for obtaining the basic sub-throttle opening according to the actual vehicle speed and the main throttle opening from the characteristic of having a sudden change region of the opening at the boundary, and the actual vehicle speed from the limit vehicle speed Means for performing feedback control of the correction amount of the sub-throttle opening so that the deviation between the limit vehicle speed (predetermined value) and the actual vehicle speed is converged to zero when the vehicle speed is equal to or higher than the determination vehicle speed that is lower by a predetermined value (feedback correction control unit 12) And means for controlling the sub-throttle valve 2 based on the basic sub-throttle opening and the feedback correction (sub-throttle opening control Step 13) and means for switching the control of the sub-throttle valve 2 when a failure of the vehicle speed sensor is determined and performing backup control to the sub-throttle opening according to the detection signal (engine speed) of the crank angle sensor (failure determination of the vehicle speed sensor) Means 14, sub-throttle opening degree control means 15 based on engine speed, and control switching means 16).
[0019]
In the basic sub-throttle opening control means 11, a basic sub-throttle according to the actual vehicle speed and the main throttle opening is obtained by searching a three-dimensional map as shown in FIG. 4 based on the actual vehicle speed and the main throttle opening. The opening is determined. In the three-dimensional map, the basic sub-throttle opening on the z axis is represented by the control command value (step value) of the step motor 4, and the sub-throttle opening decreases as the step value increases (the sub-throttle valve 2 Driven to the closed side). If the y-axis main throttle opening is in a predetermined range (for example, 18 ° to 60 °) and the x-axis vehicle speed exceeds a predetermined value (for example, 87 km / h), the z-axis step value suddenly increases from zero. It has a characteristic that it rises up to a gradient and continues to a step value of more than the limit vehicle speed (90 km / h) via a gentle gradient, and can regulate the acceleration of the vehicle to the limit vehicle speed (overshoot that increases the actual vehicle speed above the limit vehicle speed) To be suppressed).
[0020]
The feedback correction amount control means 12 calculates the feedback correction amount from the actual vehicle speed and the limit vehicle speed (predetermined value) by the calculation of equation (1).
[0021]
SLDFB _n = SLDFB _n-1 − {KP × SPD ₋ H1 + KI × (SPDLMIT−SPD _n ) −KD × (SPD ₋ H2−SPD ₋ H1)} (1)
SLDFB _n : Current feedback correction%
SLDFB _n-1 :% of previous feedback correction
KP: Proportional constant
KI: Integration constant
KD: Differential constant
SPD _- H1: SPD _n-1 −SPD _n
SPD _- H2: SPD _n-2 -SPD _n-1
SPD _n : Current vehicle speed km / h
SPD _n-1 : Vehicle speed km / h of the previous time (one execution cycle before)
SPD _n-2 : Vehicle speed km / h two times before (two execution cycles before)
SPDLMIT: Limit vehicle speed km / h (default)
[0022]
FIG. 2 is a flowchart for explaining the processing of the basic sub-throttle opening control means 11 and is executed at predetermined control cycles. In S1, the detection signal of the vehicle speed sensor is read. In S2, the detection signal of the throttle opening sensor is read. In S3, the basic sub-throttle opening corresponding to the actual vehicle speed and the main throttle opening is obtained from the three-dimensional map and output to the sub-throttle opening control means 13.
[0023]
FIG. 3 is a flowchart for explaining the processing of the feedback correction control unit 12 and is executed every predetermined control cycle. In S1, the detection signal of the vehicle speed sensor is read. In S2, it is determined whether the start condition for the calculation for feedback correction (PID control) is satisfied. In the PID calculation, when the actual vehicle speed is in a traveling state equal to or higher than the determination vehicle speed and the state continues for a predetermined time or longer, it is determined that the feedback control start condition is satisfied. When the determination of S2 is no, the process returns to S1, while when the determination of S2 is yes, the process proceeds to S3. In S3, the amount of feedback correction is obtained by PID calculation and output to the sub-throttle opening degree control means 13.
[0024]
In the sub-throttle opening control means 13, the sub-throttle opening is calculated from the basic sub-throttle opening and the feedback correction by the calculation of equation (2). Sub-throttle opening = Basic sub-throttle opening × (1 + Feedback correction / 100) (2)
In the means (14 to 16) for performing backup control of the sub-throttle valve, a crank angle sensor (engine speed detection means) and a transmission neutral switch (means for detecting intermittent power transmission from the engine to the drive wheels) are provided. Provided.
[0025]
The vehicle speed sensor failure determination means 14 determines that the neutral signal is OFF (transmission gear-engaged state) and the engine speed ≧ determination rotation based on the detection signal of the vehicle speed sensor, the neutral switch signal of the transmission, and the detection signal of the crank angle sensor. In this case, the vehicle is in a running state, and nevertheless, when there is no pulse signal (detection signal) of the vehicle speed sensor, it is determined that the vehicle speed sensor is out of order.
[0026]
In the sub-throttle opening control means 15 based on the engine speed, a two-dimensional map as shown in FIG. 6 is set, and when the control switching means 16 is switched by the failure determination means 14 of the vehicle speed sensor, the detection signal of the crank angle sensor is detected. The sub-throttle opening corresponding to the engine speed is obtained from the two-dimensional map based on the above, and the step motor 4 is controlled to the sub-throttle opening.
[0027]
The control switching means 16 is controlled by the vehicle speed sensor failure determination means 14, and when the vehicle speed sensor is normal, the terminal on the sub-throttle opening control means 13 side is connected to the terminal on the step motor 4 side while the vehicle speed sensor is in failure. The step motor 4 side terminal is connected to the sub throttle opening control means 15 side terminal based on the engine speed.
[0028]
In the vehicle speed sensor failure determination means 14, if the determination rotation to be compared with the engine speed is simply determined whether the vehicle is in a running state including the neutral signal, it can be determined that it is not 0 rpm (engine stop). The start condition of the sub-throttle opening control means 15 based on the engine speed is also defined, and the lower limit of the engine speed that may reach the determination vehicle speed that is lower than the limit vehicle speed by a predetermined value. Set to a value.
[0029]
FIG. 5 is a flowchart for explaining the backup control of the sub-throttle valve 2 and is executed every predetermined control cycle. In S1, it is determined whether engine speed ≧ determination rotation. In S2, it is determined whether or not the neutral switch is OFF. In S3, it is determined whether or not there is a pulse signal from the vehicle speed sensor. If the conditions that the determination of S1 is yes, the determination of S2 is yes, and the determination of S3 is yes are satisfied, in S4, the vehicle speed sensor is determined to be out of order. In S5, the step motor is controlled to the sub-throttle opening according to the engine speed by switching from the control based on the basic sub-throttle opening and the feedback correction to the backup control based on the engine speed by this determination. .
[0030]
With this configuration, the sub-throttle valve 2 and its control unit 5 can create a vehicle speed governor characteristic that suppresses the amount of air-fuel mixture into the engine so that the actual vehicle speed does not exceed the limit vehicle speed. The amount of air-fuel mixture to the engine is adjusted in accordance with the opening of the main throttle valve 1 that is linked to the accelerator operation in a vehicle speed region where the vehicle speed restriction does not work. Meanwhile, the sub-throttle valve 2 is controlled to an opening (for example, a fully opened state) that does not hinder the air-fuel mixture amount corresponding to the main throttle opening.
[0031]
The sub-throttle valve 2 is controlled to a sub-throttle opening corresponding to the basic sub-throttle opening and the feedback correction amount at the normal time when the vehicle speed sensor functions normally. Since the 3D map has a characteristic of having a sudden change region of the opening at the boundary between the opening region where the vehicle speed restriction does not work and the opening region where the vehicle speed restriction works, the actual vehicle speed is slightly reduced in the sudden change region of the opening. Due to the rise, the control command value (sub-throttle opening) to the step motor 4 rises with good response. In FIG. 4, since the basic sub-throttle opening suddenly changes from 0 to around 180 while the vehicle speed increases from 87 km / h to 90 km / h (restricted vehicle speed), there is an overshoot that increases the actual vehicle speed beyond the limited vehicle speed. It can be suppressed appropriately.
[0032]
The basic sub-throttle opening is a basic control amount of the sub-throttle opening that suppresses the amount of air-fuel mixture to the engine so that the actual vehicle speed does not exceed the limit vehicle speed, and the step motor 4 adds a feedback correction amount to this basic control amount. The sub-throttle opening to be applied is controlled. The feedback correction is controlled according to the deviation between the limit vehicle speed and the actual vehicle speed. When the actual vehicle speed = the limit vehicle speed, 0%, and when the actual vehicle speed> the limit vehicle speed, the + (closed side) correction amount, the actual vehicle speed <the limit At the vehicle speed, a minus (open side) correction amount is given to the sub-throttle opening. By this feedback control, the sub-throttle valve 2 is opened / closed so that the actual vehicle speed converges to the limit vehicle speed, and stable travel is possible so as to maintain the limit vehicle speed while maintaining the accelerator operation amount constant.
[0033]
When the vehicle speed sensor fails, the actual vehicle speed necessary for control based on the basic sub-throttle opening and the feedback correction cannot be obtained. In this embodiment, when the failure of the vehicle speed sensor is determined, the sub-throttle valve 2 is switched to perform backup control to the sub-throttle opening according to the detection signal (engine speed) of the crank angle sensor (failure of the vehicle speed sensor). Since the determination means 14, the sub-throttle opening degree control means 15 based on the engine speed, and the control switching means 16) are provided, even when the vehicle speed sensor fails, the sub-throttle opening degree is controlled according to the engine speed and the vehicle speed is limited. Can work effectively.
[0034]
The number of revolutions transmitted from the engine to the drive wheels varies depending on the gear position (gear ratio), but in the backup control based on the engine revolution number, the determined revolution compared with the engine revolution number is a predetermined value that is less than the limited vehicle speed. Since the lower limit value of the engine speed that can reach a low judgment vehicle speed is set, the characteristic that the sub-throttle valve 2 suddenly changes to the closed side (see Fig. 6) ensures that the vehicle acceleration is controlled below the limit vehicle speed. It is possible.
[0035]
As for the backup control, it is conceivable to convert the engine speed (detection signal of the crank angle sensor) into a vehicle speed value. In this example, the control for obtaining the sub-throttle opening degree according to the engine speed from a two-dimensional map. Therefore, no means for detecting the gear ratio (shift position) of the transmission is required, in other words, the present invention is not limited to the presence or absence of the shift position detecting means, and can be widely applied to existing vehicles.
[Brief description of the drawings]
FIG. 1 is a system outline diagram illustrating an embodiment of the present invention.
FIG. 2 is a flowchart for explaining the control contents in the same manner.
FIG. 3 is a flowchart for explaining the control content in the same manner.
FIG. 4 is also a characteristic diagram of control.
FIG. 5 is a flowchart for explaining the control contents in the same manner.
FIG. 6 is also a characteristic diagram of control.
[Explanation of symbols]
1 Main throttle valve (throttle valve)
2 Sub-throttle valve 4 Step motor (drive means)
5 Engine control unit 11 Basic sub-throttle opening control means 12 Feedback correction control means 13 Sub-throttle opening control means 14 Vehicle speed sensor failure determination means 15 Sub-throttle opening control means 16 based on engine speed Control switching means

Claims (3)

In a vehicle equipped with an engine having a main throttle valve that responds to accelerator operation and means for supplying a fuel amount corresponding to the intake air amount upstream of the main throttle as a prime mover,
A sub-throttle valve for suppressing the amount of air-fuel mixture sucked into the engine,
As a means to control the sub-throttle valve so that the actual vehicle speed does not exceed the limit vehicle speed, a characteristic that has a sudden change range of the opening at the boundary between the opening range where the vehicle speed limit does not work and the opening range where the vehicle speed limit works To obtain the basic sub-throttle opening according to the actual vehicle speed and the main throttle opening, and to converge the deviation between the limit vehicle speed and the actual vehicle speed to zero when the actual vehicle speed is equal to or higher than a determination vehicle speed that is lower than the limit vehicle speed by a predetermined value. Means for feedback-controlling the correction amount of the sub-throttle opening so as to perform, and means for controlling the sub-throttle valve based on the basic sub-throttle opening and the feedback correction amount,
When the failure of the actual vehicle speed detection means is determined, the engine speed detection means and the power from the engine to the drive wheels are switched as a means for switching the sub-throttle valve control and performing backup control to the sub-throttle opening according to the engine speed. Means for detecting intermittent transmission, means for judging whether the actual vehicle speed detecting means is faulty based on these detection signals, and switching the control of the sub-throttle valve at the time of the fault judgment to detect the engine speed A means for controlling the sub-throttle opening according to the engine speed determined from the backup characteristics based on
A vehicle speed limiting device. The means for switching the control of the sub-throttle valve at the time of failure determination of the vehicle speed detecting means and controlling the sub-throttle opening according to the engine speed obtained from the backup characteristic based on the detection signal of the engine speed is limited vehicle speed The lower limit value of the engine speed that may reach the judgment vehicle speed that is lower than the predetermined value is compared with the detection speed of the engine speed and the detection signal of the engine speed. The vehicle speed limiting device according to claim 1, wherein backup control is executed . The vehicle speed limiting device according to any one of claims 1 and 2, wherein the engine fuel is a gaseous fuel such as compressed natural gas .

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