JP5100362B2 - Shift-down control device - Google Patents

Description

  The present invention relates to downshift control when deceleration is performed with an auxiliary brake in cruise control or the like.

  In recent years, an increasing number of large-sized vehicles such as trucks have an auto cruise control (ACC) function that performs a constant speed travel while maintaining an appropriate inter-vehicle distance. In this ACC, when an inter-vehicle distance becomes short, an auxiliary brake such as an exhaust brake is operated to decelerate and control is performed so as to maintain an appropriate inter-vehicle distance (Patent Document 1).

If the auxiliary brake used for the deceleration is traveling on a highway or the like and the transmission (transmission) is shifted up to a high number of stages, the auxiliary brake may not be able to obtain a deceleration effect due to the gear ratio. Therefore, in a vehicle equipped with a mechanical automatic transmission that has become widespread in recent years, a shift-down control is proposed in which a downshift is automatically performed when the auxiliary brake is operated to enhance the deceleration action of the auxiliary brake (Patent Document 2). .
JP 2005-263098 A Japanese Utility Model Publication No. 06-006815

  When a downshift is performed while the auxiliary brake is operating, the mechanical automatic transmission disengages the clutch and executes a shift, but during the downshifting operation in which the clutch is disengaged, that is, during the shift time, Thus, the auxiliary brake does not work, and so-called “missing deceleration” occurs. This omission gives the driver a sense of incongruity, and also affects the distance and time required to decelerate to the target vehicle speed.

  The present invention has been made in view of such a technical background, and devise a mechanism for eliminating a loss of deceleration at the time of downshifting of a mechanical automatic transmission.

  According to the present invention, as a downshift control device for a vehicle equipped with a mechanical automatic transmission capable of executing a downshift accompanying the operation of an auxiliary brake, the mechanical automatic transmission starts and ends a downshift operation. A shift-down control device is proposed in which the main brake is operated during the shifting time up to.

  The shift-down control device according to the above proposal operates the main brake during the shift time in which the deceleration is lost, and obtains the deceleration by the braking force. That is, the deceleration is continued by making up for the loss of deceleration by the main brake. As a result, the driver's uncomfortable feeling can be eliminated, and as a result, the distance and time required for deceleration to the target speed can be shortened, which is convenient for inter-vehicle distance control by ACC.

  FIG. 1 shows a configuration example of a main part of a vehicle to which a shift down control device according to the present invention is applied.

  A large vehicle 1 such as a truck is provided with an exhaust brake 3 by an exhaust shutter disposed in an exhaust passage of an engine 2 as an auxiliary brake, and an auxiliary brake control device that controls opening and closing of the shutter is an engine ECU (electronic control unit). ) 4 is incorporated. The transmission 5 for transmitting the output of the engine 1 to the wheels is a mechanical automatic transmission controlled by an automatic transmission ECU 6 that is an automatic transmission control device. As described in Patent Document 2 above, It is possible to execute a downshift accompanying the operation of the auxiliary brake 3 in accordance with conditions such as the vehicle speed.

  As the main brake of the vehicle 1, a drum brake whose braking force can be controlled by the brake ECU 7 is used. The vehicle 1 further includes an auto-cruise ECU 8 that executes an ACC function. The auto-cruise ECU 8 follows the inter-vehicle distance radar 9 such as a millimeter wave radar that detects a front obstacle such as the preceding vehicle. And determine the distance, relative speed, and direction.

  These ECUs 4, 6, 7, 8 and the radar 8 communicate with each other via a CAN (Controller Area Network).

  The shift-down control device may be provided with a dedicated ECU. However, in this embodiment, the shift-down control device is realized in the auto-cruise ECU 8. That is, the auto cruise ECU 8 operates as a shift down control device according to the program. The auto-cruise ECU 8 including the function of this shift-down control device executes the control flow shown in the flowchart of FIG. 2 together with the engine ECU 4, the automatic transmission ECU 6 and the brake ECU 7.

  First, the auto-cruise ECU 8 monitors whether or not the execution of ACC is selected by the driver's ACC switch operation or the like, and when the ACC is selected, the ACC system is started (step S1). Then, the radar 9 detects the inter-vehicle distance and relative speed from the preceding vehicle (step S2). The auto-cruise ECU 8 that has obtained the information determines whether or not the auxiliary brake operation condition is satisfied based on the ACC map of FIG. 3 (step S3).

  The ACC map of FIG. 3 is for determining whether to execute main brake, auxiliary brake, downshift, engine brake, or acceleration based on the information on the inter-vehicle distance and the relative speed with the preceding vehicle obtained from the radar 9. The difference between the set inter-vehicle distance and the actual inter-vehicle distance is on the horizontal axis and the relative speed is on the vertical axis. The set inter-vehicle distance is a predetermined value of, for example, 40 m. If the actual inter-vehicle distance measured by the radar 9 is 40 m, the horizontal axis is zero, and if the actual inter-vehicle distance is far from the set inter-vehicle distance, + (right ), If you are close, go to-(left). The vertical axis is zero when the relative speed with the preceding vehicle is constant, + is approaching (up), and-is separated (down). Therefore, the closer to the upper left in the map, the closer to the preceding vehicle, the stronger the brake is switched to. Among them, a region indicated by shading in the drawing is a determination region for executing the auxiliary brake + shift down. In addition, the boundary part of each control switching can have a hysteresis characteristic.

  The auto-cruise ECU 8 releases the auxiliary brake 3 and the main brake if the conditions are not met as a result of the auxiliary brake operation condition determination based on the ACC map (steps S4 and S5), and performs engine control according to information from the radar 9 Is executed together with the engine ECU 4 (step S6).

  On the other hand, if the auxiliary brake operation condition is satisfied, the auto-cruise ECU 8 determines whether the shift-down execution condition is satisfied based on the inter-vehicle distance and the relative speed obtained from the radar 9 (step S7). At this time, it is determined in the ACC map of FIG. 3 whether or not the region is an auxiliary brake + shift down region indicated by hatching in the drawing. As a result, if the downshift execution condition is satisfied, it is confirmed whether or not the downshift has been completed first, that is, whether or not the deceleration is already underway with the auxiliary brake + downshift (step S8). Even when the downshift execution condition is not satisfied, the auto-cruise ECU 8 checks whether or not the downshift has already been completed (step S9). If the downshift has been completed, the automatic upshift control is performed. This is executed together with the ECU 6 (step S10). The upshift control at this time is a control to return to the original number of steps instructed by the automatic transmission ECU 6 before downshifting. After the upshift control or when the downshift has not been completed in step S9, it is determined that the main brake operation condition is satisfied (step S11).

  When the downshift execution condition is satisfied and the downshift has not been completed (steps S7 and S8), the auto cruise ECU 8 executes the downshift of the mechanical automatic transmission 5 together with the automatic transmission ECU 6 and the brake ECU 7 (step A). ).

  In this downshift control, the auto-cruise ECU 8 operates the main brake during the shift time until the mechanical automatic transmission 5 starts and finishes the downshift operation, and compensates for missing deceleration. The operation image is shown in FIG.

  FIG. 4 is an image diagram in which time is plotted on the horizontal axis and deceleration is plotted on the vertical axis. The upper half shows the prior art in which missing deceleration occurs, and the lower half makes up for this embodiment. Although the deceleration is higher at the time after shifting after shifting down than before shifting before shifting down, the time required for the shifting down, that is, until the clutch is disengaged, the gear is shifted and the clutch is engaged During this shift time, the auxiliary brake 3 does not work (conventional). Therefore, in the present embodiment, the main brake is operated during the shift time, and the deceleration is compensated by the braking force as shown by the dotted line. At that time, the braking force of the main brake is adjusted so that the deceleration before the downshift is smoothly connected to the deceleration after the downshift with a more dominant force without jerking.

  That is, based on the number of stages of the mechanical automatic transmission 5 before downshifting and the engine rotational speed at that time obtained from the engine ECU 4, the auto cruise ECU 8 displays an auxiliary brake deceleration map as shown in FIG. Access and calculate the deceleration before shifting by the auxiliary brake 3 (step A1). Further, the auto-cruise ECU 8 also uses an auxiliary brake deceleration map as shown in FIG. 5, and uses the auxiliary brake deceleration map based on the number of stages of the mechanical automatic transmission 5 after the downshift and the engine speed expected after the downshift. The deceleration after shifting by the brake 3 is calculated (step A2).

  The predicted engine speed after the downshift is a value obtained by predicting and adding an increase in the rotational speed during the shift time from the engine speed before the downshift. FIG. 6 shows a map for each stage number of the engine speed (horizontal axis) and the auxiliary brake deceleration (vertical axis) in consideration of this. As an example, the deceleration before shifting and the deceleration after shifting when the number of shift stages is shifted down from 12 to 9 are shown. Deceleration increases with downshifting, but an increase in engine rotation speed (as an example, about 100 to 200 rpm) occurs during shifting, that is, while the clutch is disengaged. Based on this, the deceleration after shifting is determined. . The auto-cruise ECU 8 may have the map of FIG. 6 for each number of stages and determine the deceleration by accessing the map.

  The auto-cruise ECU 8 that has calculated the deceleration before and after the gear shift issues a command for operating the main brake to the brake ECU 7 (step A3), and then issues a shift-down instruction to the automatic gear shift ECU 6 to execute the shift-down (step A4). ).

In this embodiment, the main brake is started to operate before the start of the downshift operation. In the case of a main brake system using air pressure used for a large vehicle, there is a time difference of about several hundred ms from when the brake ECU 7 starts the main brake control until the actual braking force is generated. The braking force generating delay time of the main brake that auto cruise ECU8 is to produce rice, the operation command of the main brake before the downshift in anticipation of the braking force generating delay time as a parameter, the auxiliary brake 3 Smooth control can be implemented so that the driver does not feel the shift to the main brake.

In parallel with the execution of the downshift, the auto-cruise ECU 8 controls the elapsed time of the main brake braking force (step A5). That is, the operation of the main brake is started with the braking force corresponding to the deceleration before shifting in step A1, and the braking force of the main brake is increased to the braking force corresponding to the deceleration after shifting in step A2 during the shifting time. Execute the control. Specifically, the deceleration before shifting in step A1, the elapsed time since the start of the shift-down operation, and the shift time required for the mechanical automatic transmission 5 to shift down (preferably the time when the clutch is disengaged). And the variable K determined by the difference between the deceleration before shifting at step A1 and the deceleration after shifting at step A2, the formula [main brake deceleration (m / s ² ) = deceleration before shifting (m / s ² ) Based on + K {elapsed time (s) / shift time (s)}], the brake ECU 7 is instructed to control the braking force of the main brake. This equation ends when “elapsed time / shift time” becomes 1, and the auto-cruise ECU 8 releases the main brake (step A6). The variable K is determined in accordance with the difference in deceleration before and after the shift down as can be seen from the map of FIG. 6. When the “elapsed time / shift time” becomes 1, the “main brake deceleration” is A map that is determined to have a value that matches the post-shift deceleration and that is mapped in advance according to the deceleration difference may be stored.

  The auto-cruise ECU 8 determines whether or not the main brake operation condition is satisfied after the main brake is released or when the downshift has been completed in step S8 (step S11). This main brake operation condition is determined from the ACC map of FIG. 3 based on the information of the radar 9, and when the condition is satisfied, an accurate main brake braking is executed (step S12), and when the condition is not satisfied, the main brake is released. (Step S13).

  Thereafter, the auto-cruise ECU 8 determines whether or not the ACC end condition is satisfied (step S14). The ACC end condition is that the ACC switch is turned off, the foot brake is operated, a failure is detected, etc. If this is established, the ACC system is stopped (step S15). If the end condition is not satisfied, the process is repeated from step S2.

  In the present embodiment, the system control device realized in the auto cruise ECU 8 executes the downshift control in step A, thereby operating the main brake during the shift time in which the deceleration is lost, and the deceleration is caused by the braking force. Can be compensated. As a result, the deceleration can be continued, the driver's uncomfortable feeling can be eliminated, and as a result, the distance and time required for the deceleration to the target speed can be shortened. By increasing the deceleration effect of the auxiliary brake, the use frequency of the main brake can be reduced as a result, so that the lining wear of the main brake is also suppressed.

Schematic which showed the example of a principal part structure of the vehicle to which the downshift control apparatus is applied. The flowchart which showed the control flow of ACC including the downshift control which concerns on this invention. An example of an ACC map for determining a brake operation condition. The figure showing the concept of the downshift control which concerns on this invention. The example of the map which calculates the deceleration of an auxiliary brake. The example of the map regarding the deceleration before and behind gear shifting.

Explanation of symbols

2 Engine 3 Auxiliary brake 4 Engine ECU
5 Mechanical automatic transmission 6 Automatic transmission ECU
7 Brake ECU
8 Autocruise ECU
9 Radar

Claims (5)

A downshift control device for a vehicle including a mechanical automatic transmission capable of executing a downshift accompanying the operation of an auxiliary brake,
During the shifting time until the mechanical automatic transmission is completed to start the downshift operation, and controls to so that actuates the main brake,
In the operation control of the main brake, before the shift down instruction is issued to the mechanical automatic transmission, the main brake operation command is issued in anticipation of the braking force generation delay time of the main brake.
A downshift control device characterized by the above. The shift-down control apparatus according to claim 1 , wherein an execution condition of the downshift is determined based on an inter-vehicle distance and a relative speed with a preceding vehicle obtained from a radar. A downshift control device for a vehicle including a mechanical automatic transmission capable of executing a downshift accompanying the operation of an auxiliary brake,
The mechanical automatic transmission is controlled to operate the main brake during a shift time from the start of the downshift operation to the end thereof;
In the operation control of the main brake, the operation of the main brake is started with a braking force corresponding to the deceleration before shifting of the auxiliary brake obtained based on the number of steps before the downshift and the engine speed.
During the shift time, the braking force corresponding to the shift after deceleration of the auxiliary brake obtained based on the number of stages and the expected engine speed after the downshift, Ki have strong braking force of the main brake,
The predicted engine rotation speed has a value obtained by adding an increase in rotation speed during the shift time from the engine rotation speed before the downshift.
A downshift control device characterized by the above . Formula [Main brake] based on the deceleration before the shift, the elapsed time since the start of the shift-down operation, the shift time, and the variable K determined by the difference between the deceleration before the shift and the deceleration after the shift. 4. The shift down control device according to claim 3 , wherein the braking force of the main brake is controlled based on “deceleration = deceleration before shift + K (elapsed time / shift time)”. 4. The main brake operation command is issued in advance in anticipation of a braking force generation delay time of the main brake before a downshift instruction is issued to the mechanical automatic transmission. 5. A downshift control device according to 4.

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