JP2730715B2 - Shift control method for vehicle with continuously variable transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vehicle with a continuously variable transmission capable of performing appropriate control even when a drive wheel suddenly decelerates compared to the actual vehicle speed. The present invention relates to a shift control method. 2. Description of the Related Art In a conventionally known vehicle with a continuously variable transmission, a speed ratio is generally controlled based on an engine speed and a vehicle speed (for example, see Japanese Patent Application Laid-Open No. 57-161346). In this case, the vehicle speed is represented by the rotation speed of the normal drive wheel. [Problems to be Solved by the Invention] By the way, when the above-described conventional control is performed by mounting a continuously variable transmission on a motorcycle or the like for racing on uneven terrain such as a motocross race, the following problem occurs. is there. In other words, during a competition, when sudden braking is applied on a slippery road such as a muddy road, for example, the deceleration of the drive wheels becomes steeper than the actual change in the deceleration of the vehicle body due to excessive braking force or a decrease in the friction coefficient of the road surface. When the wheels are locked, the wheels may slide on the road surface. In this case, although the actual vehicle speed of the vehicle body does not change much, the engine speed and the rotation speed of the drive wheels suddenly decrease, so that the gear ratio moves to the maximum value side (LOW side) from the optimum value. Therefore, the next time the vehicle is out of the wheel lock state and the actual vehicle speed (vehicle speed) matches the wheel speed, the engine will overspeed. SUMMARY OF THE INVENTION It is an object of the present invention to provide a shift control method for a vehicle with a continuously variable transmission that enables the vehicle to run at a speed ratio suitable for the actual vehicle speed even in the case described above. [Means for Solving the Problems] A first invention of the present invention is a shift control method for a vehicle with a continuously variable transmission that controls a gear ratio based on an engine speed and a drive wheel rotation speed representing a vehicle speed. , A minimum reference acceleration in the vehicle is set, a wheel lock is determined when the rotational acceleration of the drive wheel exceeds the set value, and if the lock time is within a certain time, a shift immediately before the lock is performed. It is characterized in that it is controlled to maintain the ratio. According to a second aspect of the present invention, there is provided a shift control method for a vehicle with a continuously variable transmission that controls a gear ratio based on an engine speed and a drive wheel rotation speed representing a vehicle speed. Setting, when the deceleration of the rotational acceleration of the drive wheel exceeds the set value, it is determined that the wheel is locked, and when the lock time is equal to or more than a predetermined time,
The present invention is characterized in that control is performed such that the gear ratio is adjusted to a gear ratio suitable for the estimated actual vehicle speed calculated from the wheel lock time. [Operation] In the first invention of the present invention, when the deceleration of the rotational acceleration of the drive wheel exceeds the set value of the minimum reference acceleration at the time of sudden deceleration, it is determined that the wheel is locked, and if this loss time is within a certain time, Maintain the gear ratio just before locking. Also, the second
According to the invention, when the lock time is equal to or longer than a predetermined time, the speed ratio is adjusted to a speed suitable for the estimated actual vehicle speed calculated from the wheel lock time. In any case, when the vehicle comes out of the locked state at the time of sudden deceleration, a speed ratio suitable for the actual vehicle speed is secured, and the engine is prevented from over-rotating. Hereinafter, an embodiment in which the present invention is applied to a motorcycle for traveling on uneven terrain equipped with a hydraulic continuously variable transmission will be described with reference to the drawings. 1 and 2 show the overall structure of a motorcycle for running on uneven terrain. In the figure, reference numeral 1 denotes a vehicle body frame, E denotes a two-stroke engine supported by the vehicle body frame 1, and TM denotes a continuously variable transmission arranged at a subsequent stage of the engine E. The continuously variable transmission TM in this case is of a hydraulic type, and the output shaft 2 and the input shaft (input member) 3 are on the same axis. The two shafts 2, 3 are arranged in the left-right direction of the vehicle body so as to be parallel to the crankshaft 4 of the engine E, and the input shaft 3 is connected to the crankshaft 4 via a chain 5. In addition, the continuously variable transmission TM includes the engine E and the chain 5
The output shaft 2 is housed in one casing 6 together with the like, and only the output shaft 2 is exposed to the outside from the left side of the vehicle body. Wf is a non-driven front wheel, Wr is a rear wheel to which the driving force is transmitted from the engine E, and a fuel tank 7 is provided on a front portion of the vehicle body frame 1 and a seat 8 is provided on a rear seat rail 1a. Fixed. The front wheel Wf is supported by a lower end of a front fork 10 attached to a head pipe 9 at a front portion of the body frame 1, and a handle 11 is attached on the head pipe 9. On the other hand, the rear wheel Wr is supported by the tip of a swing arm 13 mounted to swing while receiving the reaction force of the suspension 12 with respect to the vehicle body frame 1. Output shaft 2 of the step transmission TM
Is linked to As described above, in this motorcycle, the crankshaft 4, the input shaft 3, the output shaft 2, and the rear wheel Wr of the continuously variable transmission TM are all indicated by arrows by using the chains 5, 14 as the power transmission means. They are rotated in the same direction. Reference numeral 15 denotes an air cleaner, 16 denotes an exhaust pipe, 17 denotes an accelerator grip, and 18 denotes a clutch lever. Next, a hydraulic circuit of the power transmission system will be described with reference to FIG. Referring to FIG. 1, a hydraulic continuously variable transmission TM includes a constant discharge hydraulic pump P and a variable displacement hydraulic motor M which are connected to each other so as to form a hydraulic closed circuit 21. Is the input shaft 3 driven by the engine E
, And the hydraulic motor M is connected to the rear wheel Wr via the output shaft 2 and a chain (transmission device) 14. The hydraulic closed circuit 21 includes an oil passage 21a connecting the discharge port of the hydraulic pump P and the suction port of the hydraulic motor M, and an oil path 21b connecting the discharge port of the hydraulic motor M and the suction port of the hydraulic pump P. Have. A discharge port of a replenishing pump F driven by the input shaft 3 is connected to the oil passages 21a and 21b via a replenishing oil passage 22 and check valves 23 and 24. The supplied hydraulic oil is supplied to the hydraulic closed circuit 21 via the supply oil passage 22. Further, a relief valve 25 for keeping the oil pressure of the supply oil passage 22 constant is connected in the middle of the supply oil passage 22. The two hydraulic passages 21a and 21b of the hydraulic closed circuit 21 are connected via a clutch valve 26 that operates according to a manual operation. As the clutch valve 26, a throttle valve having an intermediate position and capable of switching between an opening degree for short-circuiting between the two oil paths 21a and 21b and an opening degree for shutting off between the two oil paths 21a and 21b. Is used. When the clutch valve 26 is short-circuited, the differential oil is not supplied to the hydraulic motor M, and the power between the hydraulic pump P and the hydraulic motor M is cut off. When the clutch valve 26 is turned off, the hydraulic pump P
The hydraulic oil circulates between the hydraulic motor M and the hydraulic motor M, so that the driving force is transmitted and the vehicle travels. The former state is a state in which the clutch is disengaged, and the latter state is a state in which the clutch is engaged. Further, when the opening of the clutch valve 26 reaches the intermediate position, the circulation of hydraulic oil occurs in the hydraulic closed circuit 21 according to the opening, and the clutch is brought into a half-clutch state. The hydraulic motor M is provided with an operation member 27 for adjusting the capacity. The operation member 27 is connected to an actuator 28, and the operation of the actuator 28 is controlled by control means C including a computer. In this case, the control means C includes a throttle opening sensor Sa for detecting the throttle opening θ of the engine E, an engine speed sensor Sb for detecting the rotation speed Ne of the engine E, that is, the rotation speed of the input shaft 3, and a vehicle speed. A vehicle speed sensor Sc for detecting the rotational speed of a rear wheel (drive wheel) Wr representing V and a speed ratio detection sensor Se for detecting the operating position of the actuator 28, ie, the speed ratio e, are connected. While reading the input signals from the sensors Sa, Sb, Sc and Se, the operation of the actuator 28 is controlled based on the procedure shown in FIG. By the way, in the control means C, a reference acceleration 1 is set and stored in advance as a control condition for the shift control. This reference acceleration 1 is the maximum negative wheel rotational acceleration when the motorcycle is running on a road surface and the wheels are not locked when sudden braking is applied. In other words, it is the limit value of the negative acceleration during normal running. The limit value of the acceleration is stored in the control means C as an electric signal. Therefore, when the reference wheel acceleration exceeds 1
When it is detected that the rotational speed of Wr has dropped sharply, it can be determined that the rear wheel Wr is locked and is suddenly decelerating from the actual vehicle speed. The rotational acceleration of the rear wheel Wr is the rotational speed V
, Ie, = (Vn−Vn ₋₁ ) / (Tn−Tn ₋₁ ). Here, Tn−Tn ₋₁ = T (constant). Further, a set value V1 is set and stored as a vehicle speed signal, and a set time T1 is also stored. In FIG. 4, the control procedure of the control means C will be described. First, after initialization is performed in step S1,
In S2 and S3, the engine speed sensor Sb and the vehicle speed sensor Sc
, Are sequentially read. Next, in step S4, it is determined whether or not the wheel acceleration is smaller than 0, that is, whether or not the vehicle is decelerating. If <0, it is further determined whether or not ≦ 1 in step S5, that is, the rear wheel Wr
It is determined whether the vehicle is suddenly decelerating from the actual vehicle speed. ≤
When the value is 1, the rear wheel is locked, and in that case, the process proceeds to step S6. In step S6, it is determined whether the vehicle speed VF read last time is equal to or higher than the set value V1. When it is not more than the set value V1,
The process proceeds to step S7 to perform normal control. In step S7, the optimum gear ratio is calculated based on the actual engine speed Ne, the target engine speed given by the throttle opening θ, and the vehicle speed V. Then, the process proceeds to step S8, in which the current gear ratio e sent from the gear ratio detection sensor Se.
Is compared with the speed ratio calculated in step S7. If the two are equal, it is determined that the shift is stopped. If they are not equal, it is determined that the shift is not stopped. If it is determined in step S8 that the shift is stopped, the shift operation of the actuator 28 is stopped, and the process returns to step S2. If it is determined in step S8 that the shift is not stopped,
Proceed to S9, actuate the actuator 28 by the required value,
It returns to step S2. The flow from step 7 to step 9 is a normal shift control flow, which is the same as the conventional shift control flow. If it is determined in step S4 that it is not <0, or if it is determined in step S5 that it is not ≤1, the process proceeds to step S7 to perform normal control. If it is determined in step S6 that V ≧ V1, the process proceeds to step S10. In step S10, it is determined whether or not the state in which the wheels are locked, that is, the state in which the wheel rotational speed is sharply lower than the actual vehicle speed, has continued for the set time T1 or more. The set time T1 in this case is determined by the following standard. That is, when the wheel lock time is short, there is almost no change in the actual vehicle speed, but when the wheel lock time is long, there is a deceleration effect due to friction during wheel lock. Therefore, the actual vehicle speed after the wheel lock is smaller than the actual vehicle speed before the wheel lock. How small it can be estimated to some extent from the friction coefficient and the wheel lock time. Therefore, it is determined whether or not it is necessary to take the deceleration effect due to such friction into consideration for control depending on the length of the wheel lock time. Therefore, whether to take into account the deceleration effect due to friction is a guideline for determining the set time T1. In step S10, when the wheel lock time T <T1, it is determined that the deceleration effect due to friction is negligible, and the process proceeds to step S11, where the gear ratio is held immediately before wheel lock, that is, immediately before rapid deceleration. Then, the process returns to step S2. When the wheel lock time T ≧ T1, it is determined that the deceleration effect due to friction significantly affects the actual vehicle speed, and the process proceeds to step S12 to estimate and calculate the actual vehicle speed according to the wheel lock time. Next, in step S13, a gear ratio suitable for the estimated vehicle speed is calculated, and in step S14, the gear ratio is shifted to the LOW side to control the gear ratio calculated in step 13. Thereafter, the process returns to step S2. Next, the operation of this embodiment will be described by taking as an example a case where the motorcycle is run on a lane having a muddy portion. It is assumed that while the vehicle is traveling on a muddy road, braking is suddenly applied, and the rear wheel Wr is decelerated to a speed equal to or higher than the actual speed of the vehicle body to lock the wheels.
Then, as the rotational speed V of the rear wheel Wr drops sharply, it is determined that the wheel lock has started. When it is determined that the wheel lock has started, the speed ratio of the continuously variable transmission TM is maintained at the value immediately before the wheel lock according to the wheel lock time or is shifted to the LOW side by an amount corresponding to the estimated vehicle speed. It is shifted. Therefore, when the rear wheel Wr bites against the running road surface, a speed ratio suitable for the actual vehicle speed is secured, and the engine is prevented from over-rotating. Note that, in the above embodiment, when the wheel rotational acceleration is equal to or less than a certain set value, the case where it is determined that the rear wheel rotational speed has sharply decreased to the actual vehicle speed or more has been described. Not exclusively. For example, the rate of change of wheel rotational speed, that is, the acceleration when the wheels are stopped with braking from the no-load idling state can be stored in advance as data, so that the acceleration curve is approximated within a certain error range. At this time, it can be determined that the wheels are decelerating at a speed higher than the actual vehicle speed. Further, it is also possible to detect the wheel rotation speed separately for the front wheel and the rear wheel, and to make the same determination when the rotation speed of the rear wheel drops sharply compared to the rotation speed of the front wheel. Further, in the above embodiment, the case where the present invention is applied to a motorcycle for running on uneven terrain has been described, but the present invention may be applied to various types of vehicles with a continuously variable transmission irrespective of type and type. Can be applied. Further, the type of the continuously variable transmission is not limited to the hydraulic type, and may be a belt driven type or another type. [Effects of the Invention] As described above, according to the first aspect of the present invention, when the rotational acceleration of the drive wheel during the rapid deceleration exceeds the set value of the minimum reference acceleration, it is determined that the wheel is locked. If the time is within a certain time, the gear ratio just before the lock is maintained. In the second invention, when the lock time is equal to or longer than a certain time, the speed ratio is adjusted to a speed ratio suitable for the estimated actual vehicle speed calculated from the wheel lock time. In any case, when the vehicle is released from the locked state at the time of sudden deceleration, a speed ratio suitable for the actual vehicle speed is secured, and an effect of preventing overspeed of the engine is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings are for describing an embodiment of the present invention, and
2 is a plan view of the motorcycle, FIG. 2 is a side view thereof, FIG. 3 is a hydraulic circuit diagram of a power transmission system, and FIG. 4 is a control flowchart. E: engine, TM: continuously variable transmission, Sb: engine speed sensor, Sc: vehicle speed sensor, wheel rotation acceleration, 1: reference acceleration.

Continuation of front page    (72) Inventor Tetsuya Ichikawa               1-4-1, Chuo, Wako-shi Book Co., Ltd.               Field Technology Research Institute (72) Inventor Nobuyuki Yagigaya               1-4-1, Chuo, Wako-shi Book Co., Ltd.               Field Technology Research Institute (72) Inventor Kiyoshi Katahira               1-4-1, Chuo, Wako-shi Book Co., Ltd.               Field Technology Research Institute                (56) References JP-A-52-25971 (JP, A)                 JP-A-60-192155 (JP, A)                 JP-A-63-74732 (JP, A)                 Shokai 61-161455 (JP, U)

Claims (1)

(57) [Claims] A shift control method for a vehicle with a continuously variable transmission that controls a gear ratio based on a driving wheel rotation speed representing an engine rotation speed and a vehicle speed, wherein a minimum reference acceleration in the vehicle is set, and the rotation acceleration of the driving wheel is reduced. If the value exceeds the set value, it is determined that the wheel is locked, and if the lock time is within a certain period of time, control is performed to maintain the gear ratio immediately before the lock. Shift control method. 2. A shift control method for a vehicle with a continuously variable transmission that controls a gear ratio based on a driving wheel rotation speed representing an engine rotation speed and a vehicle speed, wherein a minimum reference acceleration in the vehicle is set, and the rotation acceleration of the driving wheel is reduced. If the value exceeds the set value, it is determined that the wheel is locked, and if the lock time is equal to or longer than a predetermined time, control is performed so as to adjust the gear ratio to the estimated actual vehicle speed calculated from the wheel lock time. Transmission control method for a vehicle with a continuously variable transmission.