JP2758398B2 - Shift control method for vehicle with continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control method for a vehicle with a continuously variable transmission that can perform appropriate control even when a drive wheel slips. The present invention relates to a technique suitable for being applied to a leveling vehicle and the like. 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 traveling on uneven terrain, the following problem occurs. That is, when the throttle is suddenly opened during traveling, for example, on a muddy road, the drive wheels may slip due to a sudden increase in torque. In this case, the driving wheels are in a state close to idling, and the engine speed and the rotation speed of the driving wheels rapidly increase. Therefore, the vehicle actually slips and outputs an erroneous value as a vehicle speed signal even though the actual vehicle speed hardly changes. As a result, the gear ratio moves to the minimum value side (TOP side), and then the vehicle slips. When the drive wheels break off from the running surface and run down on the road surface, the gear ratio becomes the minimum value side (TOP side) even though the vehicle speed is not sufficiently increased, and the gear ratio does not become an appropriate gear ratio according to the vehicle speed. A desired driving force cannot be obtained and sufficient acceleration performance cannot be exhibited. 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 a vehicle to run at an appropriate speed ratio according to an actual vehicle speed when slipping during acceleration. [Means for Solving the Problems] The present invention relates to 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. Acceleration is set as a reference value, and when the rotation value of the drive wheel exceeds the reference value, it is determined that the drive wheel is slipping due to acceleration, and the speed ratio immediately before the slip is determined based on the slip determination. While controlling to hold,
The control for maintaining the speed ratio is continued until a predetermined time elapses after the determination of the slip escape. [Operation] In the present invention, when the vehicle slips during acceleration, the rotational acceleration of the drive wheel rapidly rises, and if the drive wheel idles or is nearly overrotated continuously, it is determined to be slip and the gear ratio is set immediately before the slip. Since the value is held at the value, a speed ratio suitable for the actual vehicle speed is secured when the vehicle comes out of the slip. Therefore, the driving force does not decrease after the slip, and sufficient acceleration can be maintained. [Example] Hereinafter, an example 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.
This 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. Also, 19a, 19b
Are brake pedals. In this case, the rear wheel Wr can be braked by operating either the left or right brake pedal 19a, 19b. 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 a hydraulic motor M
Oil passage connecting the discharge port of the hydraulic pump P and the suction port of the hydraulic pump P
21b. In addition, these oil passages 21a and 21b include:
The discharge port of the supply pump F driven by the input shaft 3 is connected via a supply oil passage 22 and check valves 23 and 24,
The hydraulic oil pumped from the oil tank T 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 maximum reference acceleration 1 is set and stored in advance as a control condition for the shift control. At this time, the first reference acceleration 1 is the wheel rotational acceleration when the motorcycle is running on the road surface while accelerating to the maximum, without slipping. That is, it is the limit value of the positive acceleration during normal running. The limit value of the acceleration is stored in the control means C as an electric signal. Therefore, when it is detected that the rotation speed of the rear wheel Wr has rapidly increased beyond the maximum reference acceleration 1, it can be determined that the rear wheel Wr is slipping.
The rotational acceleration of the rear wheel Wr can be calculated as a temporal change of the rotational speed V, that is, = (Vn-Vn- ₁ ) / (Tn-Tn- ₁ ). Here, Tn−Tn ₋₁ = T (constant). The principle of this determination will be described in more detail with reference to FIGS. 5 (a) and 5 (b). Fig. 5, said motorcycle have to travel at a constant velocity V _0, slip by the state of the road surface was the throttle opening large at some point, then with the vehicle speed V ₀ again to escape from the slip state The phenomenon when the vehicle travels is shown as a change in wheel (rear wheel) rotation speed and acceleration. FIG. 7A shows a change in the rotation speed of the wheel with time as the horizontal axis. Running at a constant speed V _0, open the throttle a little at a time T _0. As a result, the rear wheel Wr slipped, and the rotation speed of the rear wheel Wr rapidly increased, resulting in excessive rotation. The meantime while slipping to some degree, the rate of change of the wheel rotational speed is reduced in response to changes in the road surface at time T _1,
After becoming a maximum speed at the time T _2, it began to slow down. And finally, securely bite into the road surface at time T _3, it becomes equal to the actual vehicle speed. Say whether acceleration of the change in this case, as shown in Figure (b), the acceleration at the time T ₀ is started to rise, transitions to leave time T ₁ of the high value. Past the time T _1, the acceleration is started lowering, the T ₂ the acceleration = 0. Then, when decelerating, the acceleration becomes negative and the time
Become again = 0 at T _3. On the other hand, a reference curve indicated by a chain line in the figure is given as a criterion for determining that the wheel has slipped and caused excessive rotation. The reference curve represents the speed change and the acceleration change each time without slipping when accelerated to the maximum at time T _0. This is set based on data obtained by experiments and the like. From these curves, a comparison can be made between the case where slippage occurs and overspeeding occurs and the case where slippage does not occur, and the determination of wheel overspeeding can be made. In this case, particularly, the maximum reference acceleration 1 as shown in FIG. 2B is set, so that when the maximum reference acceleration 1 or more is reached, it can be determined that the overspeed due to the slip has started. This is the principle of slip start determination. In FIG. 5, Ps indicates the time when it is determined that the slip has started. The slip escape determination is based on the fact that a negative change in the rotation of the wheels has occurred, that is, the wheel acceleration has changed from positive to negative, and is used as a criterion for the determination. In this example, it is determined that the slip escape at time T _2. Pe indicates when it is determined that the vehicle has slipped out. 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 0 or more, that is, whether or not the vehicle is decelerating. If ≧ 0, the process proceeds to step S5. In this step S5, it is determined whether or not the wheels are slipping and rotating excessively, and it is determined whether or not the slip control is to be performed according to the determination. That is, first, it is determined whether or not the slip has started based on whether or not ≧ 1. ≧
If it is 1, it is determined that the slip has started (see FIG. 5 (b)).
A command is issued to perform slip control.
This command continues until a predetermined time elapses after the determination of the slip exit is made. The determination of slip escape is made based on whether or not <0, that is, whether or not a negative change appears in the rear wheel rotation. If no negative change appears, the slip control is continued. In this case, the reason why the slip control is continued until a predetermined time elapses from the determination of the slip escape is that the slip escape is determined based on <0. That At time T ₂ becomes <0, still greater wheel speed V as shown in Figure 5. Therefore, the slip control cannot be immediately released at this point, and the control is continued for a predetermined time. In the example of FIG. 5, it is desirable that the predetermined time be T ₃ −T ₂ or more. If it is determined that the slip control is performed in step S5, the process proceeds to step S6. In step S6, when the slip control is started, the set time Ts is set in the counter, and time measurement is started by the timer. The time Ts can be changed based on an arbitrary factor, and for example, the setting can be changed based on the length of the slip interval. If the slip interval is short, it is set small, and if it is long, it is set large. In this case, the counter is always set to 0 when a signal indicating that slip control is to be performed is not input. After setting the set time Ts in step S6,
Proceeding to S7, the stop position of the actuator 28 is maintained so that the speed ratio of the continuously variable transmission TM is maintained at the speed ratio immediately before the slip. Thereafter, the process proceeds to step S8. In this step S8, execution is performed so as not to update the previous vehicle speed V,
It returns to step S2. In step 8, the reason why the vehicle speed V is not updated last time is as follows. It is assumed that the slip has started and the wheel rotational speed has increased while slipping for a certain time. On this occasion,
The acceleration may initially rise sharply and exceed 1, but as the slip becomes steady, the acceleration itself decreases. This is the section indicated by (a) in FIG. 5 (b). In this section, due to the decrease in the acceleration, <1 has been reached halfway, and in fact, the vehicle is slipping while the speed still increases (section (b) in FIGS. 5A and 5B). Nevertheless, it is determined in step S5 that no slip has occurred. In order to eliminate such erroneous determination, the vehicle speed V is not updated. On the other hand, when the vehicle speed V is not updated last time, the slip control is continued once it is determined that the slip has started in step S5. So, step
In S5, it has to make its own slip escape decision. As described above, in step S5, <0
, That is, whether a negative change has occurred in the rear wheel rotation. At this time, the signal of the previous vehicle speed V is required as a criterion for the determination. However, the previous vehicle speed V is not updated. Therefore, the vehicle speed V is separately stored as VN in order to determine slip escape. Then, when V-VN becomes negative, it is determined that the vehicle has slipped out, and the vehicle speed is updated last time. Of course, if the current vehicle speed is lower than the previous vehicle speed, it is determined that the vehicle is slipping out. By doing so, the judgment of the slip start and the judgment of the slip escape are made according to the actual situation. When it is determined in step S4 that ≧ 0, the process proceeds to step S9. In step S9, it is determined whether or not the time measured by the timer is equal to or longer than the time Ts set in step S6. If Ts is not reached, the routine proceeds to step S7, where the gear ratio is held at the value immediately before the slip. If it is not less than Ts, the process proceeds to step S10. In step S10, an optimal 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 proceed to step S11,
The current gear ratio e sent from the gear ratio detection sensor Se is compared with the gear ratio calculated in step S10. If the two are equal, it is determined that the gear shift is stopped, and if they are not equal, it is determined that the gear shift is not stopped. If it is determined in step S11 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 S11 that the shift is not stopped, the process proceeds to step S12, the actuator 28 is operated by a necessary value, and the process returns to step S2. Step 10 from this step
The flow shifting to 12 is a normal shift control flow, which is the same as the conventional shift control flow. If it is determined in step S5 that slip control is not to be performed, the process proceeds to step S9, and normal shift control is performed. 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 the vehicle reaches a muddy point during running, suddenly opens the throttle, and the rear wheel Wr slips. Then, the rear wheel Wr
Becomes almost idle, and the engine speed and the rotation speed of the rear wheel Wr rapidly increase. Then, it is determined that the slip has started as the rear wheel rotation speed V increases. When it is determined that the slip has started, the speed ratio of the continuously variable transmission TM is held at the value immediately before the slip. And when the rear wheel Wr eats on the running surface,
A gear ratio suitable for the actual vehicle speed is secured, and the driving force does not decrease, and sufficient acceleration can be maintained. Note that, in the above-described embodiment, a case has been described in which when the wheel rotational acceleration exceeds a certain set value, it is determined that the vehicle has slipped and over-rotated, but the method of determining over-rotation is different. Not limited to that. For example, the rate of change of wheel rotation speed during no-load idling, that is, acceleration, can be stored in advance as data.
It can also be determined that the wheel is slipping and over-rotating. In addition, the rotational speeds of the front wheels and the rear wheels are separately detected, and if the rotational speed of the rear wheels suddenly increases compared to the rotational speed of the front wheels, it may be determined that the vehicle is slipping and over-rotating. it can. 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 present invention, a slip is determined at the time of acceleration and the rotational acceleration of the drive wheel suddenly increases, and the slip is determined when the drive wheel idles or closes to the idle state and subsequently over-rotates. And the speed ratio is held at the value immediately before the slip. In addition, since the control for maintaining the gear ratio at the value immediately before the slip is continued until a predetermined time has elapsed since the determination of the slip escape, the drive wheel rotational speed that has not been sufficiently reduced at the time of the slip escape is maintained. The speed ratio control based on the drive wheel rotational speed is resumed in a state where the vehicle is surely escaped from the slip without being controlled based on the speed ratio. Therefore, when the vehicle comes out of the slip, a gear ratio suitable for the actual vehicle speed can be reliably ensured, and it is possible to reliably prevent a situation in which the driving force drops after the slip and maintain a sufficient acceleration performance. can do.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings are for describing an embodiment of the present invention, and
FIG. 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, FIG. 4 is a control flowchart, and FIG. 5 is a diagram for explaining the principle of slip determination. Yes, (a) is a diagram showing changes in wheel rotation speed, (b)
The figure shows a change in wheel rotational acceleration. E: engine, TM: continuously variable transmission, Sb: engine speed sensor, Sc: vehicle speed sensor, wheel rotation acceleration, 1: maximum 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-60-192155 (JP, A)                 JP-A-60-249762 (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 an engine rotation speed and a drive wheel rotation speed representing a vehicle speed, wherein a maximum acceleration in the vehicle is set as a reference value, and the reference value is set to the reference value. When the rotational acceleration of the drive wheel is exceeded, it is determined that the drive wheel is slipping due to acceleration, and based on the slip determination, control is performed to maintain the speed ratio immediately before the slip, and the speed ratio is maintained. A shift control method for a vehicle with a continuously variable transmission, wherein the control is continued until a predetermined time elapses from the determination of slip escape.