JP2018146061A - Vehicular control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of tire slip due to unnecessarily effective engine brake, in downhill travelling.SOLUTION: A control system 2 of a vehicle 1 is configured to, when a gear stage of a transmission 12 is a predetermined gear stage with a large speed reduction ratio among a plurality of gear stages the transmission 12 has, an engine brake condition where engine brake of an engine 11 of the vehicle 1 acts is established, and a tire slip precondition where tire slip occurs is established, control a clutch 13 so that a rotational frequency on an output side of the clutch 13 becomes a target clutch rotational frequency.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicle control system.

  In general, a vehicle having an internal combustion engine as a power source is in a fuel cut state when an accelerator pedal is released during traveling, and an engine brake is applied. For this reason, for example, when the driver enters or enters a steep downhill slope, the driver stops the depression of the accelerator pedal, switches the gear position to the first speed (low gear), and activates the engine brake. Can be prevented or suppressed.

  Patent Document 1 discloses a transmission control device for a continuously variable transmission installed in a vehicle, a transmission ratio control means for controlling a transmission ratio so as to obtain a predetermined deceleration target value during engine braking, and a road surface. A continuously variable transmission comprising: a road surface gradient detecting unit that detects a gradient; and a deceleration changing unit that changes a target value of the deceleration based on the road surface gradient obtained by the detecting unit. A shift control apparatus is disclosed.

JP-A-10-103469

  The degree of effectiveness of the engine brake becomes stronger as the gear stage of the transmission is at a low speed side (as the reduction ratio is increased). For this reason, in the configuration disclosed in Patent Document 1, if the vehicle enters a steep downward slope at a gear stage having a large reduction ratio such as the first speed (low), the engine brake may be effective and tire slip may occur. . Further, there is a vehicle provided with a transmission having a gear stage (referred to as “super low” or “extra low”) having a larger reduction ratio than the normal first speed. If such a vehicle enters a steep downward slope at a gear stage having a larger reduction ratio than the normal first speed, the engine brake is too effective as described above, and tire slip may occur.

  In view of the above situation, the problem to be solved by the present invention is to prevent or suppress the occurrence of tire slip by preventing or suppressing the engine brake from being excessively effective at a gear stage having a large reduction ratio.

  In order to solve the above problems, the present invention provides an internal combustion engine, a transmission that has a plurality of gear stages and that changes the rotational power output from the internal combustion engine, and a clutch that connects and disconnects the rotational power output from the internal combustion engine. , A vehicle control system for controlling a vehicle having a gear stage condition in which the gear stage of the transmission is a predetermined low speed gear stage, and an engine brake of the internal combustion engine is applied. When the condition is satisfied and the pre-tire slip condition determined that the possibility of tire slip is high is satisfied, the clutch is set so that the rotational speed on the output side of the clutch becomes the target clutch rotational speed. It is characterized by controlling.

  According to the present invention, it is possible to prevent or suppress the occurrence of tire slip by preventing or suppressing the effect of the engine brake at a gear stage having a large reduction ratio.

FIG. 1 is a block diagram schematically illustrating a configuration example of a control system according to an embodiment of the present invention and a vehicle to which the control system is applied. FIG. 2A is a diagram schematically showing an example of the configuration of the acceleration threshold map, and FIG. 2B is a diagram schematically showing an example of the configuration of the target clutch rotational speed map. FIG. 3 is a flowchart showing an example of processing of the control system according to the embodiment of the present invention. FIG. 4 is a time chart schematically showing an example of transmission control and vehicle behavior by the control system. FIG. 5 is a diagram schematically illustrating an example of the hardware configuration of the control system according to the embodiment of the present invention.

<Outline of the invention>
The present invention relates to a vehicle that controls a vehicle having an engine (internal combustion engine), a transmission that has a plurality of gear stages and that changes the rotational power output from the engine, and a clutch that connects and disconnects the rotational power output from the engine. In this control system, there is a possibility that the gear stage condition that the gear stage of the transmission is a predetermined low speed gear stage is satisfied, the engine brake operation condition that the engine brake is applied is satisfied, and the tire slip occurs. When the pre-tire slip condition determined to be high is satisfied, the clutch is controlled so that the output speed of the clutch becomes the target clutch speed. Since the engine brake becomes stronger as the gear speed becomes lower and tire slip is more likely to occur, such a configuration prevents or prevents tire slip at low speed gear speeds where tire slip is likely to occur. Can be suppressed.

  It is assumed that the gear stage condition is satisfied when the gear stage of the transmission is a first gear or a gear step having a larger reduction ratio than the first gear. According to such a configuration, the occurrence of tire slip can be prevented or suppressed when the gear stage is the first speed with a large reduction ratio, or when the gear stage is a gear stage with a larger reduction ratio than the first speed.

  It is assumed that the engine brake action condition is satisfied when the accelerator opening is equal to or less than the accelerator opening threshold and the vehicle speed is equal to or higher than the vehicle speed threshold. With such a configuration, for example, when the driver releases the depression of the accelerator pedal in order to apply the engine brake when traveling downhill, the engine brake operation condition is satisfied. Therefore, for example, when an engine brake is applied during traveling on a downward slope, the occurrence of tire slip can be prevented or suppressed.

  As the accelerator opening threshold, an accelerator opening at which a fuel cut state is established can be applied. With such a configuration, it is possible to prevent or suppress the occurrence of tire slip when the engine is braked in a fuel cut state.

  It is assumed that the pre-tire slip condition is satisfied when the vehicle acceleration is equal to or less than a negative acceleration threshold. At the time of deceleration (when the acceleration is a negative value), if the absolute value of the acceleration increases (the degree of deceleration increases), tire slip is likely to occur. Therefore, according to such a configuration, the occurrence of tire slip can be prevented or suppressed when the degree of deceleration of the vehicle increases.

  The acceleration threshold value is increased as the descending slope of the road surface on which the vehicle is traveling increases. During downhill traveling, tire slip is likely to occur as the road surface gradient increases. For this reason, according to such a structure, generation | occurrence | production of a tire slip can be prevented or suppressed when the downhill road surface gradient is large.

  The value of the target clutch rotational speed is decreased as the descending slope of the road surface on which the vehicle is traveling increases. During downhill traveling, the vehicle is more likely to increase in speed as the road surface gradient increases, and tire slip is more likely to occur at the start of deceleration as the speed increases. For this reason, if the target clutch rotational speed is decreased as the road surface gradient increases, the increase in vehicle speed can be prevented or suppressed even when the road surface gradient increases. Can be suppressed.

<Embodiment>
Embodiments of the present invention will be described below in detail with reference to the drawings. In the following embodiments of the present invention, “vehicle control system” may be simply abbreviated as “control system”. In the embodiment of the present invention, an example in which AMT (Automated Manual Transmission) is applied to a vehicle is shown. Furthermore, in the embodiment of the present invention, an example is shown in which a transmission having a gear stage that is lower than the normal first speed (having a large reduction ratio) is applied to a vehicle. For convenience of explanation, a gear stage having a gear ratio larger than that of the normal first speed is referred to as “extra low”.

<Control system configuration>
FIG. 1 is a block diagram illustrating a configuration example of a main part of a control system 2 according to an embodiment of the present invention and a vehicle 1 to which the control system 2 is applied.

  The vehicle 1 includes an engine 11 (internal combustion engine) as a driving force source, a transmission 12 that changes the rotational power output from the engine 11, and a clutch that connects and disconnects transmission of rotational power between the engine 11 and the transmission 12. 13. The transmission 12 is provided with a plurality of gear stages. The plurality of gear stages includes an extra low that is slower (larger reduction ratio) than the normal first speed (low gear). The transmission 12 is provided with a transmission actuator 14 for switching the gear stage. A friction clutch is applied to the clutch 13. For example, a multi-plate clutch is applied to the clutch 13. The clutch 13 is provided with a clutch actuator 15 that switches between a connected state (so-called “connected state” and “disconnected state”). As described above, the vehicle 1 is applied with the AMT that performs connection / disconnection of the clutch 13 and switching of the gear stage of the transmission 12 by the power of the actuators (the transmission actuator 14 and the clutch actuator 15). The AMT including the transmission 12 and the clutch 13 may be used, and the specific configuration is not particularly limited. For example, the total number of gear stages of the transmission 12 is not particularly limited. Further, the clutch 13 may be included in the transmission 12.

  The control system 2 includes a vehicle speed acquisition unit 21, an acceleration acquisition unit 22, a gear stage acquisition unit 23, an accelerator opening acquisition unit 24, a clutch rotational speed acquisition unit 30, a road surface gradient acquisition unit 25, and a control unit 26. A storage unit 27, a transmission actuator drive unit 28, and a clutch actuator drive unit 29. The vehicle speed acquisition unit 21 acquires the current traveling speed (vehicle speed) of the vehicle 1. The acceleration acquisition unit 22 acquires the current acceleration of the vehicle 1. The gear stage acquisition unit 23 acquires the current gear stage of the transmission 12. The accelerator opening acquisition unit 24 acquires the current accelerator opening (for example, the depression amount of an accelerator pedal (not shown)). The clutch rotational speed acquisition unit 30 acquires the rotational speed on the output side of the clutch 13. The road surface gradient acquisition unit 25 acquires the current road surface gradient. The control unit 26 controls the transmission actuator driving unit 28 and the clutch actuator driving unit 29. The storage unit 27 stores information used by the control unit 26 to control the transmission actuator driving unit 28 and the clutch actuator driving unit 29. The transmission actuator drive unit 28 drives the transmission actuator 14 according to the control of the control unit 26 and switches the gear stage of the transmission 12. The clutch actuator drive unit 29 drives the clutch actuator 15 according to the control of the control unit 26 and switches the connection / disconnection state of the clutch 13.

<Example of control>
Here, an example of control by the control system 2 will be described. When the depression of the accelerator pedal is released while the vehicle 1 is traveling, the fuel cut state is entered, and the engine brake is activated. The effectiveness of the engine brake becomes stronger as the gear stage of the transmission 12 is at a lower speed side (as the reduction ratio is larger). Therefore, the driver applies the engine brake by releasing the depression of the accelerator pedal and switching the gear stage of the transmission 12 to, for example, the first speed or the extra low when the vehicle 1 enters the down slope or before entering the vehicle. Thus, it is possible to prevent or suppress the speed increase of the vehicle 1 on a downward slope. However, if the vehicle enters a steep downward slope at a gear stage having a large reduction ratio such as first gear or extra low, the engine brake may be effective and tire slip may occur.

  Therefore, the control system 2 satisfies the condition that the gear stage of the transmission 12 is a predetermined low speed gear stage (gear stage condition) and the condition that the engine brake is operating (engine brake operation condition). In addition, when the condition that the possibility of tire slip is increased (condition before tire slip) is satisfied, the rotation speed on the output side of the clutch 13 is controlled to prevent or suppress the occurrence of tire slip. .

Gear stage condition In the embodiment of the present invention, an extra row is applied as a predetermined low-speed gear stage. However, when the transmission 12 does not have an extra low, the first speed can be applied as the predetermined gear stage. Further, when the transmission 12 has an extra low, both the first speed and the extra low may be applied as the predetermined gear stage. In short, as the predetermined low-speed gear stage, one or a plurality of gear stages closer to the lowest speed (side closer to the larger reduction ratio) among the plurality of gear stages of the transmission 12 can be applied.

-Engine brake operation condition In the embodiment of the present invention, when the accelerator opening acquired by the accelerator opening acquisition unit 24 is equal to or smaller than the accelerator opening threshold and the vehicle speed is equal to or higher than the vehicle speed threshold, Is established. That is, when the accelerator opening condition that the accelerator opening is equal to or less than the accelerator opening threshold is satisfied, and the vehicle speed condition that the vehicle speed is equal to or higher than the vehicle speed threshold is satisfied, the engine brake operation condition is satisfied. . As the accelerator opening threshold value, for example, an accelerator opening degree that provides a fuel cut state is applied. A vehicle speed at which the vehicle 1 can be regarded as traveling on a downward slope can be applied to the vehicle speed threshold. The specific values of the accelerator opening threshold and the vehicle speed threshold are not particularly limited. These may be values that can be regarded as “the vehicle 1 is traveling on a downward slope while applying the engine brake”.

Tire pre-slip condition During tire deceleration (when acceleration is a negative value), the possibility of occurrence of tire slip increases as the absolute value of the negative acceleration increases. Therefore, in the embodiment of the present invention, when the acceleration is smaller than the acceleration threshold that is a negative value (when the absolute value of the acceleration that is a negative value is larger than the absolute value of the acceleration threshold that is a negative value) ), The possibility of tire slip is increased. That is, it is assumed that the condition before tire slip is satisfied when the acceleration is a negative value and the absolute value thereof is larger than the absolute value of the acceleration threshold value which is a negative value. Note that the ease of occurrence of tire slip varies depending on the road surface gradient during traveling. For this reason, the acceleration threshold value is determined based on the road surface gradient acquired by the road surface gradient acquisition unit 25.

-Clutch control When the gear stage condition and the engine brake condition are both satisfied, the control unit 26 sets a negative acceleration threshold value based on the current road surface gradient acquired by the road surface gradient acquisition unit 25. decide. And the control part 26 judges whether the tire slip precondition was satisfied using the determined acceleration threshold value. When the pre-tire slip condition is satisfied, the control unit 26 determines the target clutch rotational speed. The target clutch rotational speed is the rotational speed on the output side of the clutch 13 that can prevent or suppress the occurrence of tire slip. Since the ease of occurrence of tire slip varies depending on the road surface gradient, the control unit 26 determines the target clutch rotational speed based on the road surface gradient acquired by the road surface gradient acquisition unit 25. Then, the control unit 26 uses the current output speed of the clutch 13 acquired by the clutch speed acquisition unit 30 so that the output speed of the clutch 13 becomes the target clutch speed. The actuator drive unit 29 is feedback-controlled. The clutch actuator driving unit 29 drives the clutch actuator 15 according to the control by the control unit 26 and controls the connection / disconnection state of the clutch 13.

  FIG. 2A is a diagram illustrating an example of an acceleration threshold map used for determining an acceleration threshold. The control unit 26 determines the acceleration threshold value by applying the road surface gradient acquired by the road surface gradient acquisition unit 25 to this acceleration threshold value map shown in FIG. In general, during deceleration (when the acceleration is a negative value), tire slip is likely to occur as the absolute value of the negative acceleration increases. In addition, the ease of occurrence of tire slip during downhill traveling varies depending on the road surface gradient during traveling. Specifically, tire slips are more likely to occur as the road surface slope increases. Therefore, in order to prevent or suppress the occurrence of tire slip, as shown in FIG. 2A, in the acceleration threshold value map, the absolute value of the negative acceleration threshold value decreases as the gradient increases. It is defined (so that the negative acceleration threshold value approaches 0).

  FIG. 2B is a diagram showing an example of a target clutch rotational speed map used for determining the target clutch rotational speed. The control unit 26 determines the target clutch rotational speed by applying the road surface gradient acquired by the road surface gradient acquiring unit 25 to the target clutch rotational speed map shown in FIG. During downhill travel, the vehicle 1 increases in speed as the road surface gradient increases, and tire slip is likely to occur at the start of deceleration. Therefore, in order to prevent or suppress the occurrence of tire slip, the acceleration of the vehicle 1 is prevented or suppressed on a downward slope. In the embodiment of the present invention, in order to prevent or suppress the occurrence of tire slip, as shown in FIG. 2 (b), the value of the target clutch rotational speed is indicated by the road surface gradient (downhill gradient) in the target clutch rotational speed map. It is specified to become smaller as becomes larger.

  In the embodiment of the present invention, the configuration in which the acceleration threshold map is used to determine the acceleration threshold and the target clutch rotational speed map is used to determine the target clutch rotational speed is shown, but the present invention is not limited to such a configuration. For example, the control unit 26 may calculate (determine) the acceleration threshold value and the target clutch rotational speed using a calculation formula (function). In short, it may be determined so that the absolute value of the negative acceleration threshold value decreases as the road surface gradient increases (so that the negative acceleration threshold value approaches 0). Further, any configuration may be employed as long as the value of the target clutch rotational speed is decreased as the road surface gradient increases.

  Note that when the vehicle 1 is configured to be able to switch between two-wheel drive and four-wheel drive (all-wheel drive), the likelihood of tire slip is different between two-wheel drive and four-wheel drive. Specifically, tire slip is more likely to occur when driving two wheels than when driving four wheels. Therefore, in this case, the acceleration threshold map used for determining the acceleration threshold and the target clutch rotational speed map used for determining the target clutch rotational speed may be changed between when driving two wheels and when driving four wheels. . Specifically, tire slip is less likely to occur when driving four wheels than when driving two wheels, so the acceleration threshold map used when driving four wheels is compared to the acceleration threshold map used when driving two wheels. Thus, the absolute value of the acceleration threshold is defined as a large value. For the same reason, in the target clutch rotational speed map used at the time of four-wheel drive, the value of the target clutch rotational speed is defined to be larger than that of the target clutch rotational speed map used at the time of two-wheel drive. In this way, the conditions of acceleration and clutch rotational speed may be relaxed when driving four wheels as compared to when driving two wheels.

Other conditions As described above, in the embodiment of the present invention, the accelerator opening acquired by the accelerator opening acquiring unit 24 is equal to or less than the accelerator opening threshold, and the vehicle speed acquired by the vehicle speed acquiring unit 21 is the vehicle speed. It is assumed that the engine brake action condition is satisfied when it is equal to or greater than the threshold value. However, the present invention is not limited to such a configuration, and whether or not the driver is using the foot brake may be added to the determination of the condition for establishing the engine brake action condition. In other words, when the foot brake is used, or when the foot brake is used and the braking force is large, the driver intends to suppress the acceleration or decelerate (brake) by the foot brake. Can be considered. Therefore, in addition to the case where the accelerator opening is equal to or lower than the accelerator opening threshold and the vehicle speed is equal to or higher than the vehicle speed threshold, the engine is also operated when the foot brake is not used, for example, when the brake fluid pressure is equal to or lower than the threshold. The brake action condition may be satisfied.

  In this case, the control system 2 further includes a brake fluid pressure acquisition unit that acquires the current brake fluid pressure. It is assumed that the engine brake action condition is satisfied when the accelerator opening is equal to or less than the accelerator opening threshold, the vehicle speed is equal to or higher than the vehicle speed threshold, and the brake fluid pressure is equal to or lower than the brake threshold. That is, the accelerator opening condition that the accelerator opening is equal to or less than the accelerator opening threshold is satisfied, the vehicle speed condition that the vehicle speed is equal to or higher than the vehicle speed threshold is satisfied, and the brake fluid pressure acquired by the brake fluid pressure acquisition unit Assume that the engine brake action condition is satisfied when the brake condition that is equal to or less than the brake threshold is satisfied. The specific value of the brake threshold is not particularly limited, and for example, a value that can be regarded as not using or hardly using a foot brake is applicable.

<Processing flow>
Next, the flow of processing executed by the control system 2 will be described with reference to FIG. FIG. 3 is a flowchart illustrating an example of processing executed by the control system 2. The control system 2 according to the embodiment of the present invention periodically and continuously executes the process shown in FIG.

  In step S101 “Gear stage condition satisfied?”, The control unit 26 determines whether the gear stage condition is satisfied, that is, the current gear stage of the transmission 12 acquired by the gear stage acquisition unit 23 is a predetermined low speed. It is determined whether or not the gear stage. If the gear stage condition is not satisfied, that is, if the current gear stage of the transmission 12 is not a predetermined low gear stage (in the case of “No”), this step S101 is repeated. When the gear stage condition is satisfied, that is, when the current gear stage of the transmission 12 is a predetermined low gear stage (in the case of “Yes”), the process proceeds to step S102. In the embodiment of the present invention, it is assumed that the gear stage condition is satisfied when the gear stage is an extra low. However, when the transmission 12 does not have an extra low, the gear stage condition may be satisfied in the case of the first speed. Even when the transmission 12 has an extra low, the gear stage condition may be satisfied when the current gear stage is either the first speed or the extra low.

  In “engine brake operation condition satisfied?” In step S102, the control unit 26 determines whether the accelerator opening condition is satisfied and whether the vehicle speed condition is satisfied. As described above, it is assumed that the accelerator opening condition is satisfied when the current accelerator opening acquired by the accelerator opening acquiring unit 24 is equal to or less than the accelerator opening threshold. Further, it is assumed that the vehicle speed condition is satisfied when the current vehicle speed acquired by the vehicle speed acquisition unit 21 is equal to or higher than the vehicle speed threshold. It is assumed that the engine brake action condition is satisfied when both the accelerator opening condition and the vehicle speed condition are satisfied. If the engine brake action condition is not satisfied, that is, if one or both of the accelerator opening condition and the vehicle speed condition are not satisfied, the process returns to step S101. If the engine brake action condition is satisfied, the process proceeds to step S103.

  In “acceleration threshold determination” in step S103, the control unit 26 determines an acceleration threshold value based on the road surface gradient acquired by the road surface gradient acquisition unit 25. In the embodiment of the present invention, the control unit 26 determines the acceleration threshold corresponding to the road surface gradient by applying the road surface gradient acquired by the road surface gradient acquisition unit 25 to the acceleration threshold value map. However, the acceleration threshold value may be calculated using a calculation formula without using the acceleration threshold value map. In this case, it is assumed that a calculation formula for calculating the acceleration threshold value is stored in the storage unit 27 in advance. Then, the process proceeds to step S104.

  In “Satisfaction before tire slip?” In step S104, the control unit 26 determines whether the pre-tire slip condition is satisfied, that is, the current acceleration acquired by the acceleration acquisition unit 22 is equal to or less than an acceleration threshold (acceleration is Whether it is a negative value and its absolute value is greater than or equal to the absolute value of the acceleration threshold value). If the current acceleration is not less than or equal to the acceleration threshold (in the case of “No”), that is, if the pre-tire slip condition is not satisfied, the process returns to step S101. When the current acceleration of the vehicle 1 is equal to or less than the acceleration threshold value (in the case of “Yes”), the process proceeds to step S105.

  In “determination of target clutch rotational speed” in step S105, the control unit 26 determines the target clutch rotational speed based on the current road surface gradient. In the embodiment of the present invention, the control unit 26 determines the target clutch rotational speed corresponding to the road surface gradient by applying the road surface gradient acquired by the road surface gradient acquisition unit 25 to the target clutch rotational speed map. However, the target clutch rotational speed may be calculated using a calculation formula without using the target clutch rotational speed map. In this case, it is assumed that this calculation formula is stored in the storage unit 27 in advance. Then, the process proceeds to step S106.

  In “clutch rotational speed control” in step S106, the control unit 26 controls the clutch actuator driving unit 29 so that the rotational speed on the output side of the clutch 13 becomes the target clutch rotational speed determined in step S105. The clutch actuator drive unit 29 drives the clutch actuator 15 according to the control by the control unit 26. In the embodiment of the present invention, the rotational speed on the output side of the clutch 13 is controlled by controlling the connection / disconnection state (degree of connection / disconnection) of the clutch 13. In the embodiment of the present invention, the control unit 26 performs feedback control using the rotation speed on the output side of the clutch 13 acquired by the clutch rotation speed acquisition unit 30. Then, the process proceeds to step S107.

  In step S107, “Is the clutch rotational speed the target value?”, The control unit 26 determines that the output rotational speed of the clutch 13 acquired by the clutch rotational speed acquisition unit 30 is the target clutch rotational speed determined in step S105. Determine whether or not. If the rotational speed on the output side of the clutch 13 is not equal to the target clutch rotational speed, the process returns to step S106. This process is terminated when the rotational speed on the output side of the clutch 13 reaches the target clutch rotational speed. Thus, steps S106 and S107 are repeated until the rotational speed on the output side of the clutch 13 reaches the target clutch rotational speed. When the rotation speed on the output side of the clutch 13 reaches the target clutch rotation speed, the series of processes is terminated.

<Examples of vehicle behavior>
Next, an example of the behavior of the vehicle 1 to which the control system 2 according to the embodiment of the present invention is applied will be described with reference to FIG. FIG. 4 is a time chart for explaining the behavior of the vehicle 1, and the horizontal axis represents time. Here, an example in which an extra low is applied as a predetermined low-speed gear stage is shown. When the vehicle 1 enters a downward slope, the driver cancels the depression of the accelerator pedal, and the gear stage of the transmission 12 is switched from the first speed to the extra low. In addition, the time chart of FIG. 4 is assumed to start from the timing when the vehicle 1 enters the downward slope. As shown in FIG. 4, the driver does not operate the foot brake during the period shown in FIG. 4, and the brake fluid pressure is maintained at 0 (the braking force by the foot brake is not acting).

When the driver releases the depression of the accelerator pedal, the accelerator opening acquired by the accelerator opening acquiring unit 24 is reduced to 0, which is lower than the accelerator opening threshold. Timing T ₁ of the in the figure indicates the timing at which the accelerator opening is equal to or less than the accelerator position threshold. Then, the timing T ₁ after the accelerator opening degree is continued following the state accelerator position threshold. Therefore, in the example shown in FIG. 4, the timing T ₁ Oite accelerator opening condition is satisfied, thereafter a state where the accelerator opening condition is satisfied.

When the driver performs an operation of switching the gear stage from the first speed to the extra low, the control unit 26 controls the clutch actuator driving unit 29 to shift the clutch 13 to the “disengaged state”. 26 controls the transmission actuator drive unit 28 to switch the gear stage of the transmission 12 from the first speed to the extra low. The timing T ₂ in the figure indicates the start timing of the operation in which the clutch actuator 15 shifts the clutch 13 to the “disengaged state”. Timing T ₃ indicates the timing at which the transmission actuator 14 switches the transmission 12 from the first speed to the extra low. Timing T ₃ later, gear acquired by the gear position acquisition unit 23 becomes extra low. Then, at this timing T ₃ , the gear stage condition is satisfied, and thereafter the state where the gear stage condition is satisfied continues.

When the gear stage of the transmission 12 is switched from the first speed to the extra low, the control unit 26 controls the clutch actuator driving unit 29 to shift the clutch 13 from the “disengaged state” to the “connected state”. Timing T ₄ in the figure indicates the start timing of the operation of switching the clutch 13 from the “disengaged state” to the “connected state”.

When the timing T ₂ after the clutch 13 is traveling downward slope in the "off state", the vehicle speed rises. Timing T ₅ in figure indicate when the current vehicle speed acquired by the vehicle speed acquisition unit 21 becomes equal to or higher than the vehicle speed threshold. In this timing T _5, the vehicle speed condition is satisfied. As described above, since the accelerator opening condition is established at the timing T ₁ , the engine brake operation condition is established when the vehicle speed condition is established at the timing T ₅ . Further, since the gear stage condition at timing T ₃ is established, at the timing T _5, so that the gear condition and the engine braking condition is established.

When the gear stage condition and the engine braking action condition are satisfied at timing T ₅ , the control unit 26 determines an acceleration threshold value, and the acceleration of the vehicle 1 acquired by the acceleration acquisition unit 22 is equal to or less than the determined acceleration threshold value. It is determined whether or not the acceleration is negative (whether the absolute value is equal to or greater than the acceleration threshold).

Timing T ₆ indicates the timing of clutch meet. When the clutch meet is performed by the operation of the clutch actuator 15, the engine brake is applied, so that the vehicle speed and the clutch rotational speed start to decrease. For this reason, after the clutch meet timing T ₆ , the vehicle 1 changes from speeding up to deceleration due to the action of the engine brake. That is, the acceleration changes from a positive value to a negative value. As the clutch 13 approaches the “connected state” completely from the clutch meet timing T _6, the force applied by the engine brake increases, so the acceleration is negative and the absolute value increases.

A timing T ₇ in the figure indicates a timing at which the acceleration of the vehicle 1 acquired by the acceleration acquisition unit 22 becomes equal to or less than the determined acceleration threshold. When the acceleration is a negative value and its absolute value increases (the degree of deceleration increases) and becomes a value equal to or less than the determined acceleration threshold, the pre-tire slip condition is satisfied.

The timing T ₁ after a state in which the gear stage condition is satisfied, the timing T ₅ after a state where the engine braking condition is satisfied. Therefore, the when the timing T ₇ tire slip preconditions in is satisfied, a state in which the gear stage condition and the engine braking condition and tire slip before conditions are all met. For this reason, at timing T ₇ , the control unit 26 determines the target clutch rotational speed and starts controlling the rotational speed on the output side of the clutch 13 so as to be the determined target clutch rotational speed. Therefore, as shown in FIG. 4, the rotational speed on the output side of the clutch 13 approaches the target clutch rotational speed. Timing T ₈ indicates the timing at which the output side rotational speed of the clutch 13 reaches the target clutch rotational speed. When the rotational speed on the output side of the clutch 13 reaches the target clutch rotational speed, the series of processes is terminated.

<Action and effect>
When the vehicle 1 enters a downward slope, when the driver releases the depression of the accelerator pedal and switches the gear to a predetermined low gear, the gear condition and the accelerator opening condition are satisfied. When the vehicle speed increases in this state and the vehicle speed condition is satisfied, the engine brake operation condition is satisfied, and both the gear stage condition and the engine brake operation condition are satisfied. When both the gear stage condition and the engine braking action condition are satisfied, the control unit 26 determines whether the acceleration of the vehicle 1 is equal to or less than the acceleration threshold, that is, whether the pre-tire slip condition is satisfied, and before the tire slip. When the condition is satisfied, the target clutch rotational speed is determined, and control is performed so that the rotational speed of the clutch 13 becomes the target clutch rotational speed.

  The engine brake becomes stronger as the gear stage of the transmission 12 becomes lower, and tire slip is more likely to occur. For this reason, according to such a structure, generation | occurrence | production of a tire slip can be prevented or suppressed in the low speed gear stage which is easy to generate | occur | produce a tire slip.

  Further, it is assumed that the engine brake condition is satisfied when the accelerator opening is equal to or less than the accelerator opening threshold and the vehicle speed is equal to or higher than the vehicle speed threshold. With such a configuration, for example, when the driver depresses the accelerator pedal in order to apply the engine brake while traveling at a vehicle speed that is equal to or higher than the vehicle speed threshold, the engine brake operation condition is satisfied. Become. Therefore, for example, when an engine brake is applied during traveling on a downward slope, the occurrence of tire slip can be prevented or suppressed.

  Further, when the acceleration of the vehicle 1 is equal to or less than a negative acceleration threshold (when the acceleration is negative and the absolute value is equal to or greater than the absolute value of the acceleration threshold. In other words, the degree of deceleration is defined by the acceleration threshold. The condition before occurrence of tire slip is satisfied when the degree of deceleration is greater than or equal to the degree of deceleration performed. During deceleration, tire slip is likely to occur as the absolute value of acceleration, which is a negative value, increases. For this reason, according to such a structure, generation | occurrence | production of a tire slip can be prevented or suppressed on the conditions on which a tire slip is easy to generate | occur | produce.

  Further, when the vehicle travels on an inclining gradient with the engine brake applied, tire slip is likely to occur as the gradient increases. Therefore, the absolute value of the acceleration threshold is increased as the road surface gradient on which the vehicle is traveling increases. According to such a configuration, occurrence of tire slip can be prevented or suppressed under conditions where tire slip is likely to occur.

  During downhill traveling, the vehicle 1 increases in speed as the road surface gradient increases, and tire slip tends to occur at the start of deceleration. Therefore, it is specified that the value of the target clutch rotational speed decreases as the road surface gradient increases. With such a configuration, even if the road surface gradient increases, the speed increase of the vehicle 1 can be prevented or suppressed. Therefore, even when the road surface gradient increases, the occurrence of slip at the start of deceleration can be prevented or suppressed.

<Hardware configuration example of control system>
Next, a hardware configuration example of the control system 2 will be described with reference to FIG. FIG. 5 is a diagram schematically illustrating a hardware configuration example of the control system 2 and a configuration example of a main part of the vehicle 1 to which the control system 2 is applied.

  The vehicle 1 is provided with a transmission ECU 51 (Electric Control Unit), a vehicle speed sensor 52, an acceleration sensor 53, a gear stage sensor 54, an accelerator opening sensor 56, a gradient sensor 57, and an engine ECU 58. Yes. The transmission ECU 51 may also be referred to as a TCU (Transmission Control Unit). These are connected so that signals can be transmitted and received, for example, by an in-vehicle LAN.

  The transmission ECU 51 includes a computer having a CPU 511, a ROM 512, and a RAM 513. A computer program for controlling the transmission 12 and the clutch 13 and information used for controlling the transmission 12 and the clutch 13 are stored in advance in a format readable by the CPU 511 in the ROM 512 of the computer of the transmission ECU 51. . Information used for controlling the transmission 12 and the clutch 13 includes an acceleration threshold map and a target clutch rotational speed map. The RAM 513 can temporarily store a detection result by a predetermined sensor described later. The CPU 511 of the computer of the transmission ECU 51 reads out a computer program stored in the ROM 512 and executes it using the RAM 513 as a work area. Thus, the transmission ECU 51 functions as the control unit 26, the storage unit 27, the transmission actuator driving unit 28, and the clutch actuator driving unit 29, and the above-described control is realized.

  The vehicle speed sensor 52 detects the vehicle speed. The vehicle degree sensor 52 functions as the vehicle speed acquisition unit 21. The configuration of the vehicle speed sensor 52 is not particularly limited, and various known vehicle speed sensors can be applied. Further, the vehicle 1 may not have the vehicle speed sensor 52. For example, the transmission ECU 51 may calculate the vehicle speed based on the rotation speed on the output side of the clutch 13 detected by a clutch rotation speed sensor 55 described later and the gear position sensor 54. In this case, the transmission ECU 51, the clutch rotational speed sensor 55, and the gear position sensor 54 function as the vehicle speed acquisition unit 21.

  The acceleration sensor 53 detects the acceleration of the vehicle 1. The acceleration sensor 53 functions as the acceleration acquisition unit 22. The configuration of the acceleration sensor 53 is not particularly limited, and various types of known acceleration sensors can be applied. Note that the vehicle 1 may not have the acceleration sensor 53. For example, the transmission ECU 51 may calculate the acceleration by differentiating the vehicle speed detected by the vehicle speed sensor 52. In this case, the transmission ECU 51 and the vehicle speed sensor 52 function as the acceleration acquisition unit 22.

  The gear stage sensor 54 detects the current gear stage of the transmission 12. In the embodiment of the present invention, the gear stage sensor 54 functions as the gear stage acquisition unit 23. The detection result is transmitted to the transmission ECU 51. The gear stage sensor 54 only needs to be configured to detect the current gear stage of the transmission 12, and the specific configuration is not particularly limited. Various known gear stage sensors can be applied to the gear stage sensor 54.

  The clutch rotational speed sensor 55 detects the rotational speed on the output side of the clutch 13. In the embodiment of the present invention, the clutch rotational speed sensor 55 functions as the clutch rotational speed acquisition unit 30. The configuration of the clutch rotational speed sensor 55 is not particularly limited, and various known rotational speed sensors such as a rotary encoder can be applied.

  The accelerator opening sensor 56 detects the current depression amount (operation amount) of the accelerator pedal. In the embodiment of the present invention, the accelerator opening sensor 56 functions as the accelerator opening acquisition unit 24. The configuration of the accelerator opening sensor 56 is not particularly limited, and various known position sensors, for example, can be applied.

  The gradient sensor 57 detects the road surface gradient (that is, the inclination of the vehicle 1) in which the vehicle 1 is currently traveling. In the embodiment of the present invention, the gradient sensor 57 functions as the road surface gradient acquisition unit 25. The detection result by the gradient sensor 57 is transmitted to the transmission ECU 51. For the gradient sensor 57, for example, various known tilt sensors can be applied. Note that the vehicle 1 may not have the gradient sensor 57. For example, the transmission ECU 51 may calculate (estimate) the road surface gradient currently being traveled from the relationship between the load applied to the engine 11 and the vehicle speed. In this case, the load of the engine 11 is measured from the vehicle speed detected by the vehicle speed sensor 52, the current gear position detected by the gear position sensor 54, and the current accelerator position detected by the accelerator position sensor 56. it can. Therefore, in this case, the transmission ECU 51, the vehicle speed sensor 52, the gear position sensor 54, and the accelerator opening sensor 56 function as the road surface gradient acquisition unit 25.

  Here, a configuration is shown in which the transmission ECU 51 functions as the control unit 26, the storage unit 27, and the like, but is not limited to such a configuration. As shown in FIG. 5, the engine ECU 58 also includes a computer having a CPU, a ROM, and a RAM. The transmission ECU 51 and the engine ECU 58 may function as the control unit 26, the storage unit 27, and the like by the cooperation of the transmission ECU 51 and the engine ECU 58. The vehicle 1 may be provided with a drive circuit that is controlled by the transmission ECU 51 to drive the transmission actuator 14 and a drive circuit that is controlled by the transmission ECU 51 to drive the clutch actuator 15. In this case, these function as the transmission actuator drive unit 28 and the clutch actuator drive unit 29.

  As mentioned above, although embodiment of this invention was described in detail with reference to drawings, the said embodiment only showed the specific example in implementation of this invention. The technical scope of the present invention is not limited to the embodiment described above. The present invention can be variously modified without departing from the spirit thereof, and these are also included in the technical scope of the present invention.

  For example, the configuration of the transmission is not particularly limited. As described above, the transmission may have a gear stage having a larger reduction ratio than the normal first speed. Further, the total number of gears of the transmission is not particularly limited. In addition, the clutch is designed to transmit rotational power without being moistened in a fully connected state, and may be any clutch designed to transmit rotational power while slipping in a so-called half-clutch state. The specific configuration is not limited. For example, a friction clutch such as various multi-plate clutches can be applied. Further, the type and configuration of the vehicle to which the control system of the present invention can be applied are not particularly limited.

  The present invention is a technique effective for a control system for a vehicle. And according to this invention, when the gear stage of a transmission is a predetermined low speed gear stage, generation | occurrence | production of a tire slip can be prevented or suppressed.

1: vehicle, 11: engine, 12: transmission, 13: clutch, 14: transmission actuator, 15: clutch actuator, 2: vehicle control system, 21: vehicle speed acquisition unit, 22: acceleration acquisition unit, 23: gear Step acquisition unit, 24: accelerator opening acquisition unit, 25: road surface gradient acquisition unit, 26: control unit, 27: storage unit, 28: transmission actuator drive unit, 29: clutch actuator drive unit, 30: acquisition of clutch rotation speed , 51: transmission ECU, 511: CPU, 512: ROM, 513: RAM, 52: vehicle speed sensor, 53: acceleration sensor, 54: gear position sensor, 55: clutch rotational speed sensor, 56: accelerator opening sensor, 57: Gradient sensor, 58: Engine ECU

Claims (7)

A vehicle control system that controls a vehicle having an internal combustion engine, a transmission that has a plurality of gear stages and that shifts the rotational power output from the internal combustion engine, and a clutch that connects and disconnects the rotational power output from the internal combustion engine Because
There is a possibility that a gear stage condition in which the gear stage of the transmission is a predetermined low speed gear stage is satisfied, an engine brake operating condition in which the engine brake of the internal combustion engine is applied, and tire slip occurs. When the pre-tire slip condition determined to be high is satisfied, the vehicle control system controls the clutch so that the output side rotational speed of the clutch becomes a target clutch rotational speed.   2. The vehicle control system according to claim 1, wherein the gear stage condition is satisfied when the gear stage of the transmission is a first gear or a gear step having a larger reduction ratio than the first gear. .   2. The vehicle control system according to claim 1, wherein the engine brake action condition is satisfied when the accelerator opening is equal to or less than an accelerator opening threshold and the vehicle speed is equal to or higher than the vehicle speed threshold.   The vehicle control system according to claim 3, wherein the accelerator opening threshold is an accelerator opening at which a fuel cut state is established.   5. The vehicle control system according to claim 1, wherein the pre-tire slip condition is satisfied when the acceleration of the vehicle is equal to or less than a negative acceleration threshold value. 6.   The vehicle control system according to claim 5, wherein the absolute value of the acceleration threshold value is decreased as a downward gradient of a road surface on which the vehicle is traveling increases.   The vehicle control system according to any one of claims 1 to 4, wherein the value of the target clutch rotational speed is decreased as the descending slope of the road on which the vehicle is traveling increases.

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