JP2024138608A - Vehicle control method and vehicle control device - Google Patents

Abstract

To suppress excessive speed of an internal combustion engine without reducing torque more than necessary.SOLUTION: A control unit calculates a predetermined target differential rotation speed Rtd based on the difference between a current engine speed Rr of an internal combustion engine and an upper limit rotation speed Rm, and calculates a limit torque TL for limiting the output of the internal combustion engine based on an integrated value of the target differential rotation speed Rtd. When the target torque Tt of the internal combustion engine becomes equal to or larger than the limit torque TL, the control unit limits the torque of the internal combustion engine to the limit torque TL. The limit torque TL is set so that a ratio of change increases when a gear stage of a transmission is lower.SELECTED DRAWING: Figure 3

Description

The present invention relates to a vehicle control method and a vehicle control device.

For example, Patent Document 1 discloses a technology that prevents over-revving of the internal combustion engine while the vehicle is traveling by controlling the throttle valve opening to a target throttle opening set according to the gear position of the transmission when the engine speed of the internal combustion engine reaches a predetermined speed, regardless of the degree of accelerator opening.

JP 2003-314336 A

The rate at which the engine speed of an internal combustion engine increases until it reaches a predetermined speed varies depending on the gear position of the transmission. Therefore, if the predetermined engine speed at which torque down begins is set constant regardless of the gear position of the transmission, there is a risk that the torque down will be more than necessary, resulting in insufficient driving force, or that insufficient torque down will lead to over-revving.

In other words, there is room for further improvement in preventing over-revving of the internal combustion engine and protecting the engine.

The vehicle of the present invention calculates the limit torque of the internal combustion engine based on an integrated value of a target difference speed calculated based on the difference between the engine speed of the internal combustion engine and the upper limit speed of the internal combustion engine, and limits the torque of the internal combustion engine to the limit torque when the target torque of the internal combustion engine is equal to or greater than the limit torque. The limit torque is set so that the rate of change increases the lower the gear stage of the transmission connected to the internal combustion engine.

The present invention can prevent the driver from feeling a lack of driving force due to torque reduction more than necessary, and can also prevent over-rotation due to insufficient torque reduction.

4 is a timing chart showing an example of engine speed and torque behavior when preventing overspeed of the internal combustion engine. 4 is a timing chart showing an example of engine speed and torque behavior when preventing overspeed of an internal combustion engine to which the present invention is applied. 3 is a flowchart showing a flow of control of an internal combustion engine to which the present invention is applied.

Below, one embodiment of the present invention will be described in detail with reference to the drawings.

The vehicle to which this invention is applied has an internal combustion engine that serves as the drive source of the vehicle, a transmission that changes the drive force of the internal combustion engine, and drive wheels to which the drive force of the internal combustion engine is transmitted via the transmission.

The internal combustion engine is, for example, a gasoline engine or a diesel engine.

The transmission is a stepped or continuously variable transmission, and has a speed change mode in which the engine speed of the internal combustion engine increases as the vehicle speed increases.

The vehicle also has a sensor capable of detecting the engine speed of the internal combustion engine, and a control unit that serves as a control unit and performs various calculations based on signals from the various sensors.

The control unit controls the internal combustion engine so that the engine speed does not exceed a predetermined upper limit speed (permissible speed) Rm while the vehicle is running. The upper limit speed Rm is the maximum permissible speed of the internal combustion engine.

The engine speed of an internal combustion engine can be reduced by narrowing the throttle valve to reduce the amount of intake air and lower the torque of the internal combustion engine.

Therefore, the control unit calculates a predetermined target differential speed Rtd based on the difference between the current engine speed Rr and the upper limit speed Rm of the internal combustion engine, and calculates a limit torque TL for limiting the output of the internal combustion engine based on an integrated value of this target differential speed Rtd. In other words, the control unit corresponds to a target differential speed calculation section and a limit torque calculation section.

Then, when the target torque Tt of the internal combustion engine becomes equal to or greater than the limit torque TL, the control unit limits the torque of the internal combustion engine to the limit torque TL. The target torque Tt is set, for example, according to the accelerator opening (the amount of depression of the accelerator pedal).

The target differential rotation speed Rtd is a value obtained by multiplying the value obtained by subtracting the current engine rotation speed Rr from the upper limit rotation speed Rm by a predetermined first correction amount Gd. The first correction amount Gd is set to a larger value the lower the currently selected gear stage of the transmission. Therefore, the target differential rotation speed Rtd is set to a larger value the lower the currently selected gear stage of the transmission.

The limit torque TL is a value obtained by multiplying the target differential rotation speed Rtd by the second correction amount Gp and adding a predetermined torque correction amount Tc to the value. The second correction amount Gp is set to a predetermined constant value (fixed value) regardless of the gear stage of the transmission. The torque correction amount Tc is a value obtained by multiplying the target differential rotation speed Rtd by a predetermined fourth correction amount Gio equivalent to a correction coefficient and adding it to the previous value of the torque correction amount Tc. In other words, the limit torque TL is calculated based on the integrated value of the target differential rotation speed Rtd. The fourth correction amount Gio is a value set according to the gear stage of the transmission, and is set to a larger value the lower the gear stage of the transmission. The fourth correction amount Gio is a value that is relatively large relative to the third correction amount Gi described later, regardless of the gear stage of the transmission.

When the target torque Tt is less than the limit torque TL, the torque correction amount Tc is calculated using the third correction amount Gi, which corresponds to the correction coefficient, instead of the fourth correction amount Gio. In other words, when the target torque Tt is less than the limit torque TL, the torque correction amount Tc is a value obtained by multiplying the target differential rotation speed Rtd by a predetermined third correction amount Gi and adding the result to the previous value of the torque correction amount Tc. The third correction amount Gi is, for example, a small value close to "0", and is set to a predetermined constant value (fixed value) regardless of the gear stage of the transmission.

Therefore, the rate of change of the limit torque TL increases the lower the gear of the transmission.

Furthermore, when the limit torque TL falls below the torque threshold value Th during torque down, the internal combustion engine uses the third correction amount Gi, which corresponds to the correction coefficient, instead of the fourth correction amount Gio when calculating the torque correction amount Tc. In other words, when the target torque Tt is equal to or greater than the limit torque TL and the limit torque TL is less than the torque threshold value Th, the torque correction amount Tc is a value obtained by multiplying the target differential rotation speed Rtd by a predetermined third correction amount Gi and adding the result to the previous value of the torque correction amount Tc.

Figure 1 is a timing chart showing an example of engine speed and torque behavior when preventing over-revving of an internal combustion engine, comparing an internal combustion engine to which the present invention is applied with an internal combustion engine of a comparative example.

Characteristic line C1 shown in solid line in FIG. 1 indicates the engine speed of the internal combustion engine when the present invention is applied. Characteristic line C2 shown in dashed line in FIG. 1 indicates the engine speed of the internal combustion engine of the comparative example. Characteristic line C3 shown in solid line in FIG. 1 indicates the limit torque TL of the internal combustion engine when the present invention is applied. Characteristic line C4 shown in dashed line in FIG. 1 indicates the torque of the internal combustion engine of the comparative example.

In the comparative example, when the engine speed of the internal combustion engine reaches the upper limit speed Rm, the torque of the internal combustion engine is reduced to prevent the engine speed from exceeding the upper limit speed Rm.

In this comparative example, as shown in FIG. 1, if the rate of increase in the engine speed is large, the speed limit may not be implemented in time, and the engine speed may exceed the upper limit speed Rm.

In addition, in the comparative example, as shown in FIG. 1, the torque of the internal combustion engine is reduced only after the engine speed of the internal combustion engine reaches the upper limit speed Rm, so the torque decreases at a large rate during the torque reduction, and there is a risk that the driver will feel uncomfortable due to the deceleration G.

In addition, in the comparative example, as shown in Figure 1, the torque decreases at a faster rate when the torque is reduced, which may cause the driver to feel a lack of driving force due to the torque reduction.

The internal combustion engine to which the present invention is applied implements torque reduction to prevent over-revving of the internal combustion engine by utilizing a limit torque TL (characteristic line C3) calculated based on the integrated value of the target differential rotation speed Rtd, which is set to a larger value the lower the gear stage of the transmission.

Time t1 in Figure 1 is the timing when the accelerator pedal is depressed and the torque is set to a target torque Tt that is greater than a predetermined torque threshold Th.

The torque threshold Th is a torque value that corresponds to the running resistance (so-called "road load") when traveling at a constant speed, and the faster the vehicle speed, the larger the value becomes. In other words, the higher the gear, the larger the value becomes.

Time t2 in FIG. 1 is the timing when the target torque Tt becomes equal to or greater than the limit torque TL represented by the characteristic line C3. The internal combustion engine of this embodiment starts torque reduction from time t2 so that the engine speed does not exceed the upper limit speed Rm. Therefore, the internal combustion engine of this embodiment reduces the rate of increase (increase speed) of the engine speed from time t2. In addition, since the timing of torque reduction is earlier in the internal combustion engine of this embodiment than in the internal combustion engine of the comparative example, the rate of change of torque when torque reduction is performed is slower than in the internal combustion engine of the comparative example, and the impact of torque reduction on the driver (such as deceleration G and a feeling of insufficient driving force) can be suppressed.

Time t3 in FIG. 1 is the timing when the engine speed of the internal combustion engine of the comparative example, represented by characteristic line C2, reaches the upper limit speed Rm. The internal combustion engine of the comparative example starts torque reduction from time t3 so that the engine speed does not exceed the upper limit speed Rm. Therefore, since the internal combustion engine of the comparative example starts torque reduction from time t3 so that the engine speed does not exceed the upper limit speed Rm, the engine speed overshoots the upper limit speed Rm. Also, since the timing of torque reduction is delayed in the internal combustion engine of the comparative example compared to the internal combustion engine of this embodiment, the rate of change of torque when torque is reduced is faster than in the internal combustion engine of this embodiment.

Time t4 in FIG. 1 is the timing when the engine speed of the internal combustion engine of this embodiment, represented by characteristic line C1, reaches the upper limit speed Rm. As shown by the arrow in FIG. 1, the internal combustion engine of this embodiment starts torque down before the engine speed reaches the upper limit speed Rm, slowing down the rate of increase of the engine speed, so overshooting and undershooting of the engine speed with respect to the upper limit speed Rm after time t4 is suppressed. Similarly, as shown by the arrow in FIG. 1, the internal combustion engine of this embodiment starts torque down before the engine speed reaches the upper limit speed Rm, slowing down the rate of increase of the engine speed, so overshooting and undershooting of the torque with respect to the torque threshold value Th after time t4 is suppressed.

In addition, in the internal combustion engine of this embodiment, the target differential rotation speed Rtd used when calculating the limit torque TL changes depending on the gear stage of the transmission. In other words, in the internal combustion engine of this embodiment, the limit torque TL has a different value on the high gear stage side and the low gear stage side.

Figure 2 is a timing chart showing an example of engine speed and torque behavior when preventing overspeeding of an internal combustion engine to which the present invention is applied, comparing a low gear position with a high gear position.

The characteristic line _C1L shown by a solid line in Fig. 2 indicates the engine speed of the internal combustion engine when the gear is low. The characteristic line _C1H shown by a dashed line in Fig. 1 indicates the engine speed of the internal combustion engine when the gear is high. The characteristic line _C3L shown by a solid line in Fig. 1 indicates the limit torque TL of the internal combustion engine when the gear is low. The characteristic line _C3H shown by a dashed line in Fig. 1 indicates the limit torque TL of the internal combustion engine when the gear is high.

Time t1 in Figure 2 is the timing when the accelerator pedal is depressed and the torque is set to a target torque Tt that is greater than a predetermined torque threshold Th.

Time t2 in Fig. 2 is the timing when the target torque Tt becomes equal to or greater than the limit torque TL represented by the characteristic line _C3L . Time t3 in Fig. 2 is the timing when the target torque Tt becomes equal to or greater than the limit torque TL represented by the characteristic line _C3H .

In an internal combustion engine, the lower the gear position, the smaller the limit torque TL value, and the earlier torque reduction begins.

The rate at which the limit torque TL decreases (the rate of change) increases the lower the gear stage of the transmission. Also, the amount of change in the limit torque TL per given time (unit time) (the slope of characteristic line C3) increases the lower the gear stage of the transmission. Therefore, when the torque of the internal combustion engine is limited to the limit torque TL, the amount of change in torque per given time increases the lower the gear stage of the transmission.

When the limit torque TL becomes smaller than the target torque Tt, the amount of change in the limit torque TL per specified time (unit time) is greater than when the limit torque TL is equal to or greater than the target torque Tt. Between the target torque Tt and the torque threshold value Th, the amount of change in the limit torque TL per specified time (unit time) is increased by increasing the value of the torque correction amount Tc.

The engine speed at which the target torque Tt becomes equal to or greater than the limit torque TL becomes lower as the transmission gear becomes lower.

Time t4 in Figure 2 is the timing when the engine speed of the internal combustion engine reaches the upper limit speed Rm.

In this embodiment, the internal combustion engine uses different correction coefficients when calculating the torque correction amount Tc depending on the magnitude relationship between the limit torque TL and the torque threshold value Th. Specifically, when the limit torque TL becomes smaller than the torque threshold value Th, the target differential rotation speed Tcd is multiplied by the third correction amount Gi instead of the fourth correction amount Gio when calculating the torque correction amount Tc. Therefore, the characteristic lines C3L and C3H representing the limit torque TL are suppressed from undershooting the torque threshold value Th at the timing when the engine speed of the internal combustion engine reaches the upper limit rotation speed Rm.

The internal combustion engine of the above embodiment is set so that the rate of change of the limit torque TL increases the lower the gear stage of the transmission.

Therefore, the internal combustion engine of this embodiment can perform appropriate rotation speed control (rotation speed limit) by torque control (torque limit) using a limit torque TL according to the rate of increase of the engine rotation speed.

Note that while rotation speed control is prone to misjudgment due to its high fluctuation frequency, torque control has the advantage that misjudgment is less likely to occur due to its low fluctuation frequency. Furthermore, rotation speed control is prone to hunting of the engine rotation speed to be controlled due to its high fluctuation frequency, but torque control is less likely to cause hunting of the torque to be controlled due to its low fluctuation frequency.

In other words, the internal combustion engine of the above embodiment can prevent the driver from feeling a lack of driving force due to an excessive torque reduction, and can also prevent over-revolution due to insufficient torque reduction.

Figure 3 is a flowchart showing the control flow of the internal combustion engine in the above-mentioned embodiment.

In step S1, the current gear position of the transmission is detected and read.

In step S2, the target differential rotation speed Rtd, limit torque TL, and torque correction amount Tc are calculated. The torque correction amount Tc calculated in step S2 is calculated using the third correction amount Gi.

In step S3, it is determined whether the target torque Tt is smaller than the limit torque TL. If the target torque Tt is smaller than the limit torque TL in step S3, the process proceeds to step S4. If the target torque Tt is equal to or greater than the limit torque TL in step S3, the process proceeds to step S5.

In step S4, the limit torque TL is calculated based on the torque correction amount Tc using the third correction amount Gi.

In step S5, it is determined whether the limit torque TL is equal to or greater than the torque threshold value Th. If in step 5, the limit torque TL is equal to or greater than the torque threshold value Th, the process proceeds to step S6. If in step 5, the limit torque TL is less than the torque threshold value Th, the process proceeds to step S4.

In step S6, the limit torque TL is calculated based on the torque correction amount Tc using the fourth correction amount Gio.

Although specific examples of the present invention have been described above, the present invention is not limited to the above examples, and various modifications are possible without departing from the spirit of the present invention.

For example, the present invention can also be applied to hybrid vehicles that have a driving mode in which the drive wheels are driven by the power of an internal combustion engine.

The above-described embodiments relate to a vehicle control method and a vehicle control device.

Claims (5)

calculating a predetermined target difference rotation speed based on a difference between an engine rotation speed of the internal combustion engine and a preset upper limit rotation speed of the internal combustion engine;
calculating a limit torque of the internal combustion engine based on the integrated value of the target difference rotation speed;
When a target torque of the internal combustion engine becomes equal to or greater than the limit torque, the torque of the internal combustion engine is limited to the limit torque;
A vehicle control method, characterized in that the limit torque is set so that the rate of change increases as the gear stage of a transmission connected to the internal combustion engine becomes lower. The vehicle control method according to claim 1, characterized in that when the torque of the internal combustion engine is limited to the limit torque, the amount of change in torque per given time increases as the gear stage of the transmission becomes lower. The vehicle control method according to claim 2, characterized in that the amount of change in the limit torque per given time is greater when the limit torque is smaller than the target torque of the internal combustion engine than when the limit torque is equal to or greater than the target torque of the internal combustion engine. A method for controlling a vehicle according to any one of claims 1 to 3, characterized in that the transmission has a speed change mode in which the engine speed of the internal combustion engine increases as the vehicle speed increases. a target difference rotation speed calculation unit that calculates a predetermined target difference rotation speed based on a difference between an engine rotation speed of the internal combustion engine and a preset upper limit rotation speed of the internal combustion engine;
a limit torque calculation unit that calculates a limit torque of the internal combustion engine based on the integrated value of the target difference rotation speed;
a control unit that limits the torque of the internal combustion engine to the limit torque when a target torque of the internal combustion engine becomes equal to or greater than the limit torque,
A vehicle control device, characterized in that the limit torque has a greater rate of change as the gear stage of a transmission connected to the internal combustion engine becomes lower.

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