JP5538117B2 - Engine brake control device - Google Patents

Description

  The present invention relates to an engine brake control device that suppresses engine braking when a reduction in wheel speed or slip is detected.

  In general, in a vehicle, when an accelerator is released or a downshift is performed while traveling on a low μ road or the like, if an excessive engine brake is applied, the drive wheels may slip or become locked. . For this reason, for example, in Japanese Patent Application Laid-Open No. 64-87844 (hereinafter referred to as Patent Document 1), when a decrease in wheel speed is detected, fuel cut during engine braking is stopped and fuel supply is resumed. A technique for recovering the grip of a wheel is disclosed. As a technique for accurately detecting such a decrease in wheel speed, Japanese Patent Application Laid-Open No. 8-207724 (hereinafter referred to as Patent Document 2) provides a longitudinal acceleration obtained from a vehicle body acceleration sensor and a wheel speed sensor. A technique for detecting a decrease in wheel speed by comparing with longitudinal acceleration is disclosed.

Japanese Patent Laid-Open No. 64-87844 JP-A-8-207724

  However, in the technique for detecting a decrease in wheel speed from two longitudinal accelerations as disclosed in Patent Document 2 described above, the longitudinal acceleration obtained from the vehicle body acceleration sensor includes, for example, an error corresponding to acceleration acting on the road surface gradient. In the longitudinal acceleration obtained from the wheel speed sensor, mechanical errors and control errors (for example, when the accelerator is turned on and off instantaneously, the mechanical delay of the throttle is Error due to throttle control settings, etc.), and there is a problem that it is impossible to detect a decrease in wheel speed with high accuracy.

  The present invention has been made in view of the above circumstances, and it is possible to accurately detect a decrease in wheel speed based on the longitudinal acceleration obtained from the vehicle body acceleration and the longitudinal acceleration obtained from the wheel speed, and to detect a decrease in wheel speed or slip. Another object of the present invention is to provide an engine brake control device capable of accurately suppressing engine braking.

The present invention provides a first acceleration detection means for detecting a longitudinal acceleration based on an acceleration acting on a vehicle body as a first acceleration, and a second acceleration detection for detecting a longitudinal acceleration based on a wheel speed as a second acceleration. And when it is determined that the stability of the difference value is secured based on a difference value between the first acceleration and the second acceleration, and the difference value is compared with a predetermined threshold value. It is characterized in the kite and control means for executing control to suppress an engine braking when determining the reduction of the wheel speed with.

  According to the engine brake control device of the present invention, when detecting a decrease in wheel speed with high accuracy by the longitudinal acceleration obtained from the vehicle body acceleration and the longitudinal acceleration obtained from the wheel speed, It becomes possible to suppress engine braking accurately.

It is explanatory drawing which shows schematic structure of the whole vehicle which concerns on one Embodiment of this invention. It is a flowchart of the fuel cut suppression control program which concerns on one Embodiment of this invention. It is a flowchart of a main drive wheel slip determination flag setting routine according to an embodiment of the present invention. It is a flowchart of the wheel speed fall determination flag setting routine which concerns on one Embodiment of this invention. It is a flowchart of the stability determination flag setting routine which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes an engine disposed in the front part of the vehicle, and the driving force by the engine 1 is transmitted from an automatic transmission with a manual mode (shown including a torque converter) 2 behind the engine 1 to a transmission output shaft It is transmitted to the transfer 3 via 2a.

  Further, the driving force transmitted to the transfer 3 is input to the rear wheel final reduction device 7 via the rear drive shaft 4, the propeller shaft 5, and the drive pinion shaft portion 6, while the reduction drive gear 8, the reduction driven gear 9. Then, it is input to the front wheel final reduction gear 11 via the front drive shaft 10 which is the drive pinion shaft portion. Here, the automatic transmission 2, the transfer 3, the front wheel final reduction gear 11 and the like are integrally provided in the case 12.

  The driving force input to the rear wheel final reduction gear 7 is transmitted to the left rear wheel 14rl via the rear wheel left drive shaft 13rl and to the right rear wheel 14rr via the rear wheel right drive shaft 13rr. The driving force input to the front wheel final reduction gear 11 is transmitted to the left front wheel 14fl via the front wheel left drive shaft 13fl and to the right front wheel 14fr via the front wheel right drive shaft 13fr.

  The transfer 3 is a wet multi-plate clutch (transfer clutch) as a variable torque transmission capacity clutch in which a drive plate 15a provided on the reduction drive gear 8 side and a driven plate 15b provided on the rear drive shaft 4 side are alternately stacked. ) 15 and a transfer piston 16 that variably applies a fastening force (differential limit torque) of the transfer clutch 15. Therefore, this vehicle controls the pressing force by the transfer piston 16 and controls the differential limiting torque of the transfer clutch 15, so that the torque distribution ratio is between the front wheel and the rear wheel, for example, between 100: 0 and 50:50. It is a four-wheel drive vehicle with a front engine / front drive vehicle base (FF base) that can be changed by the vehicle. The pressing force of the transfer piston 16 is given by a transfer clutch drive unit (not shown) configured by a hydraulic circuit having a plurality of solenoid valves and the like, and a control signal for driving the transfer clutch drive unit is sent from a control device (not shown). Is output.

  In FIG. 1, reference numeral 20 denotes an engine control device that controls the engine 1, and the engine control device 1 includes a main control unit 21 that performs fuel injection control, ignition timing control, and other overall control for the engine 1; When the engine is braked, the engine is mainly configured to include an engine brake control unit 22 that instructs the main control unit 21 to execute the fuel cut when the fuel cut is not suppressed as described later.

  The engine brake control unit 22 detects four wheel speeds Vfl (front left wheel speed), Vfr (right front wheel speed), Vrl (left rear wheel speed), and Vrr (right rear wheel speed). A speed sensor 31fl, 31fr, 31rl, 31rr, a body acceleration sensor 32 as a first acceleration detecting means for detecting a longitudinal acceleration (first acceleration) GB based on an acceleration acting on the vehicle body, and a throttle opening θth A throttle opening sensor 33 to detect and an inhibitor switch 34 to detect the shift position of the automatic transmission 2 are connected.

  Based on these input signals, the engine brake control unit 22 determines that a condition such as when the engine is braked (for example, the throttle valve is fully closed and the engine speed exceeds a preset speed). In principle, when it is established, a fuel cut execution signal is output to the main control unit 21. At this time, the engine brake control unit 22 prohibits execution of fuel cut as a fuel cut suppression state when a fuel cut prohibition request is output by the fuel cut suppression control program shown in FIG.

Next, the fuel cut suppression control program executed by the engine brake control unit 22 will be described with reference to the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) 101, necessary parameters, specifically, a main driving wheel slip determination flag FL1 (main driving wheel slips) set in a main driving wheel slip determination flag setting routine described later. A flag set to “1” in the state), a wheel speed decrease determination flag FL2 (a flag set to “1” in the wheel speed decrease state) set in a wheel speed decrease determination flag setting routine described later, and the like are read.

  Next, in S102, it is determined whether or not a precondition for executing the fuel cut suppression control is satisfied. Here, the precondition for executing the fuel cut suppression control is, for example, within a set time (for example, 5 seconds) after the accelerator is released, whether the engine brake is weak, whether there is an abnormality in the sensor, etc. Is the condition.

  As a result of the determination in S102, if the above-mentioned precondition is not satisfied, the program is left as it is, while if the precondition is satisfied, the process proceeds to S103.

  When the above-mentioned preconditions are satisfied and the routine proceeds to S103, it is determined whether or not the main drive wheel slip determination flag FL1 is set (FL1 = 1), FL1 = 1, and the main drive wheel is in a slip state. In this case, the process proceeds to S104, where a fuel cut prohibition request is output to set a fuel cut suppression state and prohibit execution of fuel cut.

  On the other hand, if the main drive wheel slip determination flag FL1 is cleared (FL1 = 0) in S103 described above, the process proceeds to S105, and whether or not the wheel speed decrease determination flag FL2 is set (FL2 = 1). Determined. As a result of this determination, if FL2 = 1 and the wheel speed is in a reduced state, the process proceeds to S104, where a fuel cut prohibition request is output to prohibit execution of fuel cut in a fuel cut suppression state. Conversely, if the wheel speed decrease determination flag FL2 is cleared (FL2 = 0), the program is exited as it is.

Next, the main drive wheel slip determination flag setting routine executed by the engine brake control unit 22 will be described with reference to the flowchart of FIG.
First, in S201, necessary parameters, specifically, wheel speeds Vfl, Vfr, Vrl, Vrr of four wheels are read.
Next, the process proceeds to S202, in which it is determined whether or not the main drive wheel speed / driven wheel speed has been kept below a preset ratio rc1 (eg, 0.92) for a set time (eg, 0.06 seconds). . Here, in the case of an FF-based four-wheel drive vehicle or a front wheel drive vehicle as in this embodiment, the main drive wheel wheel speed is the wheel speed of the front wheel, that is, (Vfl + Vfr) / 2. Conversely, the driven wheel speed is the wheel speed of the rear wheel, that is, (Vrl + Vrr) / 2.

  As a result of the determination in S202, when the main driving wheel speed / driven wheel speed does not continue below the preset ratio rc1 for the set time or more, the main driving wheel speed is substantially the same as the driven wheel speed. However, since it is not considered that the main driving wheel is slipping, the process proceeds to S203, the main driving wheel slip determination flag FL1 is cleared (FL1 = 0), and the program is exited.

  On the other hand, when the main driving wheel speed / driven wheel speed is less than the preset ratio rc1 for the set time or longer, the main driving wheel speed is slower than the driven wheel speed. Since it is considered that the main drive wheel is slipping, the process proceeds to S204.

  When the process proceeds to S204, it is determined whether or not the main driving wheel speed is equal to or higher than a set speed (for example, 10 km / h). When the process proceeds to S205, it is determined whether or not the driven wheel speed is equal to or higher than a set speed (for example, 10 km / h). If it is determined that both S204 and S205 are equal to or higher than the set speed, it can be determined that the slip determination can be performed with sufficient accuracy. Therefore, the process proceeds to S206, where the main drive wheels are determined to be in the slip state and the main drive The wheel slip determination flag FL1 is set (FL1 = 1) and the program is exited. Conversely, if either of S204 and S205 is less than the set speed, it cannot be determined that the slip determination has been performed with sufficient accuracy, so the routine proceeds to S203 and the main drive wheel slip determination flag FL1 is cleared (FL1 = 0) to exit the program.

  Next, a wheel speed reduction determination flag setting routine executed by the engine brake control unit 22 will be described with reference to the flowchart of FIG.

  First, in S301, necessary parameters, specifically, throttle opening θth, longitudinal acceleration GB based on acceleration acting on the vehicle body, four-wheel wheel speeds Vfl, Vfr, Vrl, Vrr, shift position of automatic transmission 2 A stability determination flag FL3 set in a stability determination flag setting routine described later (a flag set to “1” when it is determined that the stability of a difference value ΔG described later is secured), The road gradient correction reference value CGS calculated by the sex determination flag setting routine is read.

In step S302, an acceleration difference value ΔG is calculated. This is calculated by the following equation (1), for example.
ΔG = GB − ((dVfl / dt) + (dVfr / dt) + (dVrl / dt) + (dVrr / dt)) / 4 (1)

  Next, the process proceeds to S303, where it is determined whether FL3 = 1, that is, whether the stability of the difference value ΔG is ensured. If FL3 = 0 and the stability of the difference value ΔG is not secured, the process proceeds to S304, the wheel speed decrease determination flag FL2 is cleared (FL2 = 0), and the program is exited. Conversely, if FL3 = 1 and the stability of the difference value ΔG is ensured, the process proceeds to S305.

  In S305, it is determined whether or not the accelerator has changed from ON to OFF. If the accelerator has not changed from ON to OFF, it is not necessary to determine the reduction in wheel speed during engine braking. Proceed to clear the wheel speed decrease determination flag FL2 (FL2 = 0) and exit the program.

  If it is determined in S305 that the accelerator has changed from ON to OFF, the process proceeds to S306, and the difference value ΔG after the update of the reference value updated in the later-described stability determination flag setting routine is set to (C + CGS: C is set in advance). It is determined whether or not the predetermined value) is continued for the set time, that is, whether or not the set time is equal to or greater than the value obtained by removing the error corresponding to the acceleration caused by the road surface gradient.

  As a result of this determination, if it is determined that the difference value ΔG is not longer than (C + CGS) for the set time, the process proceeds to S304, the wheel speed decrease determination flag FL2 is cleared (FL2 = 0), and the program exits. .

  On the other hand, if it is determined that the difference value ΔG continues for (C + CGS) or more for the set time, the process proceeds to S307, where it is determined whether or not the accelerator OFF is continued for the set time. As a result of this determination, if the accelerator OFF is not continued for the set time, an error due to the mechanical delay of the throttle, the throttle control setting, etc. after the accelerator OFF may be included in the determination. Then, the wheel speed reduction determination flag FL2 is cleared (FL2 = 0) and the program is exited.

  In S307, if the accelerator OFF is continued for the set time, the process proceeds to S308, and it is determined whether the set time has elapsed after the completion of the upshift. That is, during the upshift or immediately after the completion of the upshift, there is a large acceleration fluctuation, which may cause an error in determining a decrease in wheel speed. If not, the process proceeds to S304, where the wheel speed reduction determination flag FL2 is cleared (FL2 = 0) and the program is exited.

  In S308, if the set time has elapsed after the completion of the upshift, the process proceeds to S309 to determine whether the set time has elapsed after the completion of the downshift. Similarly to S308, this S309 is also accompanied by large fluctuations in acceleration during downshifting or immediately after completion of downshifting, and this fluctuation may cause an error in determining a decrease in wheel speed. If the set time has not elapsed after completion of the downshift, the process proceeds to S304, the wheel speed decrease determination flag FL2 is cleared (FL2 = 0), and the program is exited.

  In S309, if the set time has elapsed after the completion of the downshift, the process proceeds to S310, where it is determined that the wheel speed is decreasing, and the wheel speed decrease determination flag FL2 is set (FL2 = 1). And exit the program.

  Next, a stability determination flag setting routine executed by the engine brake control unit 22 will be described with reference to the flowchart of FIG.

  First, in S401, necessary parameters, specifically, throttle opening θth, longitudinal acceleration GB based on acceleration acting on the vehicle body, and wheel speeds Vfl, Vfr, Vrl, Vrr of four wheels are read.

In step S402, the acceleration difference value ΔG is calculated by the above-described equation (1).
Next, in S403, the absolute value | dΔG / dt | of the acceleration difference value change rate is calculated.

  Next, the process proceeds to S404, where it is determined whether or not the absolute value | dΔG / dt | of the acceleration difference value change rate is within a set time and a preset threshold value. If it is not within the preset threshold as a result of this determination, it is determined that the state is unstable, the process proceeds to S405, the stability determination flag FL3 is cleared (FL3 = 0), and the program is exited.

  Conversely, if the absolute value | dΔG / dt | of the acceleration difference value change rate is within the set time, a preset threshold value, the process proceeds to S406 and the set time immediately before the accelerator changes from ON to OFF, the acceleration difference value It is determined whether or not the absolute value | dΔG / dt | of the change rate is within a threshold value. If the result of this determination is that it is not within the threshold value, it is determined that the state is unstable, the process proceeds to S405, the stability determination flag FL3 is cleared (FL3 = 0), and the program is exited.

  Conversely, if it is determined that the absolute value | dΔG / dt | of the acceleration difference value change rate is within the set time and threshold value immediately before the accelerator ON changes to OFF, the process proceeds to S407 and the accelerator ON changes to OFF. The longitudinal acceleration (vehicle acceleration) GB based on the acceleration acting on the vehicle body at the time and the longitudinal acceleration (wheel acceleration) Gw based on the four-wheel wheel speed as reference values (first reference value and second reference value, respectively) Update.

  In step S408, the stability determination flag FL3 is set (FL3 = 1). In step S409, the difference value of the second reference value Gw from the first reference value GB set as the reference value is set on the road surface. Set as gradient correction reference value CGS and exit the program. As described above, the engine brake control unit 22 functions as the second acceleration detection means, the main drive wheel slip determination means, and the control means.

  Thus, according to the embodiment of the present invention, the difference value ΔG between the longitudinal acceleration GB acting on the vehicle body and the longitudinal acceleration Gw based on the wheel speed is calculated, and the predetermined time immediately before the accelerator changes from ON to OFF. When the absolute value | dΔG / dt | of the change rate of the difference value does not exceed the preset threshold value, it is determined that the stability of the difference value ΔG is secured, and the accelerator changes from ON to OFF. Sometimes the longitudinal acceleration GB and the longitudinal acceleration Gw are updated as the first reference value and the second reference value, the first reference value and the second reference value are updated, and the accelerator is in the OFF state. At a certain time, the difference value ΔG after the update of the first reference value and the second reference value is set to a difference equal to or larger than the set value corrected by the difference value of the second reference value Gw from the first reference value GB. The time continues and the accelerator is off for the set time. And, further, the wheel speed is adapted to prohibit fuel cut is determined to be decreased when the elapsed up / downshift completion setting time. Therefore, in an appropriate vehicle state, an error in acceleration caused by the road surface gradient with a difference value of the second reference value Gw from the first reference value GB is accurately removed. The first reference value GB and the second reference value Gw are updated as appropriate when the stability of the difference value ΔG is ensured and the accelerator changes from ON to OFF, and the reference values GB and Gw are updated. If there is a possibility that the fluctuation of acceleration may be included as an error, such as when the accelerator OFF is not continued for a set time, or when the set time has not elapsed after completion of up / downshift, Misjudgment is suppressed without judging wheel speed reduction. For this reason, when the decrease in the wheel speed is accurately detected by the longitudinal acceleration GB obtained from the vehicle body acceleration and the longitudinal acceleration Gw obtained from the wheel speed, and when the wheel speed drop or slip is detected, the engine brake It becomes possible to perform suppression.

  In the embodiment of the present invention, an example of an FF-based four-wheel drive vehicle has been described. However, it goes without saying that the present invention can be applied to other types of vehicles. Further, in the embodiment of the present invention, the control for outputting the fuel cut prohibition request has been described as an example of the control for suppressing the engine brake. However, in addition, the engine braking is performed by upshifting the shift position of the automatic transmission. You may make it suppress, or you may make it prohibit a downshift.

DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Transfer 14fl, 14fr, 14rl, 14rr Wheel 20 Engine control device 21 Main control part 22 Engine brake control part (2nd acceleration detection means, main drive wheel slip determination means, control means)
31fl, 31fr, 31rl, 31rr Wheel speed sensor 32 Car body acceleration sensor (first acceleration detecting means)
33 Throttle opening sensor 34 Inhibitor switch

Claims (6)

First acceleration detecting means for detecting a longitudinal acceleration based on an acceleration acting on the vehicle body as a first acceleration;
Second acceleration detecting means for detecting the longitudinal acceleration based on the wheel speed as the second acceleration;
When it is determined that the stability of the difference value is ensured based on the difference value between the first acceleration and the second acceleration, and the wheel is compared with the difference value and a predetermined threshold value. Control means for executing control to suppress engine braking when it is determined that the speed has decreased;
Engine brake control device characterized by comprising a.   When it is determined that the stability of the difference value is ensured, the control means compares the difference value with the predetermined threshold value in a preset driving state of the vehicle to reduce the wheel speed. The engine brake control device according to claim 1, wherein the determination is made. The difference value is calculated by subtracting the second acceleration from the first acceleration,
When the control means determines that the stability of the difference value is secured, the state in which the difference value exceeds the predetermined threshold when the accelerator changes from on to off continues for a set time, 3. The engine brake control device according to claim 1, wherein it is determined that the wheel speed has decreased when the off state continues for a predetermined time.   The predetermined threshold value used for comparison by the control means is set as a first reference value and a second reference value, respectively, for a first acceleration and a second acceleration in a preset driving state of the vehicle. 4. The value according to claim 1, wherein a difference value between the reference value and the second reference value is a correction value, and a value set in advance is added to the correction value. 5. Engine brake control device.   The first reference value and the second reference value are the difference between a predetermined time immediately before the accelerator changes from on to off and the absolute value of the change rate of the difference value does not exceed a preset threshold value. 5. The engine brake control device according to claim 4, wherein in a state where it is determined that the stability of the value is secured, the value is updated to a new value when the accelerator changes from on to off. A main drive wheel slip determining means for comparing the main drive wheel speed and the driven wheel speed to determine the slip of the main drive wheel;
The control means is configured to execute control for suppressing engine braking in at least one of a case where a decrease in the wheel speed is determined and a case where the main drive wheel slip determination means determines a slip of the main drive wheel. The engine brake control device according to any one of claims 1 to 5.

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