JP2788569B2 - Method of determining shift control start timing at start of vehicle continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle equipped with a continuously variable transmission, which starts the vehicle by performing clutch control, and then shifts to shift control to drive the vehicle. The present invention relates to a control method for realizing a smooth transition from the clutch connection control to the shift control at the time of performing the control. 2. Description of the Related Art A clutch device for performing clutch connection control in a continuously variable transmission is disclosed, for example, in JP-A-56-56.
Japanese Unexamined Patent Publication (Kokai) No.-95722 discloses an example. In this device, a short-circuit path is formed between two oil paths that form a closed circuit by connecting a hydraulic pump and a hydraulic motor, and a clutch valve capable of adjusting the degree of opening is disposed in the short-circuit path. I have. The control device for controlling the operation of the clutch valve is connected to first detection means for detecting the engine speed and second detection means for detecting the throttle opening. And a control force proportional to the throttle opening to drive the clutch valve in the opening direction. When starting control using such a clutch device, the throttle opening is adjusted in response to the accelerator pedal being depressed and released so that the vehicle starts smoothly. The degree is shifted from the fully open state to the fully closed state via the half clutch state, and the clutch connection control is performed. That is, from the state where the clutch is released and its capacity becomes zero, through the state where this is partially connected and becomes a half clutch, the connection capacity of the clutch is controlled until the connection of the clutch is completed, and the start of vehicle use is started. Control is exercised. After the clutch has been connected in this manner, a speed change control is subsequently performed, and the speed ratio is controlled so as to gradually change from a maximum state (LOW) to a minimum state (TOP). Smooth acceleration can be obtained. The running control of such a continuously variable transmission for a vehicle has already been proposed by the present applicant (Japanese Patent Application Laid-Open No. 62-237164). [0004] After performing the clutch connection control as described above, when shifting to the control of the gear ratio,
Conventionally, the shift to the speed ratio control has been performed after the clutch connection is completed. For this reason, it is necessary to detect the completion of the connection of the clutch, and this detection method is performed based on the relationship between the engine speed and the vehicle speed or based on the relationship between the throttle opening (accelerator opening) and the vehicle speed. Methods and the like are known. However, in either case, the clutch connection is completed when the vehicle speed is low, and the vehicle speed sensor normally mounted on the vehicle is not very accurate at low vehicle speeds. Then, there is a problem that a shift easily occurs at a time when the completion of the clutch connection is detected. [0005] If there is such a shift, for example, if it is detected that clutch connection has actually been completed but not completed, the shift is started in a half-clutch state, and the clutch connection is completed. In this case, the speed ratio becomes small, and a problem arises that the engine speed decreases.
On the other hand, if this is detected later than the completion of the actual clutch connection, there is a problem that the start of the shift is delayed and the engine speed increases, or a sufficient feeling of acceleration cannot be obtained. [0006] It is considered that clutch connection can be completed by judging whether or not the clutch capacity (for example, clutch opening) is almost fully closed. However, even if the clutch capacity is the same, when the vehicle is on an uphill road, a flat road, or a downhill road at the start, the vehicle speed at that time is different. For example, when the vehicle starts on an uphill road, the vehicle speed is lower than that on a flat road even with the same clutch capacity. In this case, if the clutch opening degree is almost fully closed and the connection is determined to be completed while the vehicle speed is low and the shift control is performed, there is a problem that the engine rotation is reduced or sufficient acceleration cannot be obtained. . [0007] In view of such a problem, the present invention determines a shift control start timing at which a shift from clutch connection control to shift control can be performed smoothly (without impairing the running feeling) when the vehicle starts. The aim is to provide a method. In order to achieve the above object, according to the method of the present invention, the lower limit value of the planned clutch connection completion vehicle speed corresponding to the throttle opening is set in advance and the predetermined value is set. A clutch capacity slightly disengaged from the capacity when the clutch is completely connected is set in advance as the connection completion clutch capacity value, and when the engine throttle is released to start the vehicle, the actual clutch capacity is set to the actual engine speed. Control to make the target clutch capacity set in accordance with the actual throttle opening and the actual clutch opening. In addition to the comparison, the planned connection completion clutch capacity (opening) and the actual clutch capacity (opening) are compared, and the actual vehicle speed is compared with the actual throttle opening. If the expected clutch connection completion vehicle speed is above the lower limit,
Further, when it is detected that the actual clutch capacity has become larger than the planned connection completion clutch capacity, it is determined that it is the timing to start the shift control. As described above, when the connection of the clutch is determined based on whether or not the clutch capacity is equal to or larger than the planned connection completion clutch capacity, when the vehicle is on an uphill road, a flat road, or a downhill road at the start, Since the vehicle speed at that time is different, there is a problem that it is difficult to shift to smooth shift control.If the clutch connection completion is determined based only on the vehicle speed, the vehicle speed detection accuracy is low because the vehicle speed is low when the clutch is connected, There is a problem that a shift between the actual connection completion and the completion determination occurs, and it is difficult to shift to a smooth shift control. For this reason, in the present invention, in addition to determining whether the actual vehicle speed is equal to or higher than the lower limit of the planned clutch connection completion vehicle speed, it is determined whether the clutch capacity is equal to or higher than the planned connection completion clutch capacity. It has become. That is, when the vehicle speed sensor exceeds the lower limit value and the clutch opening becomes equal to or more than the planned connection completion clutch capacity, it is determined that the timing to start the shift control has come. This makes it possible to accurately determine the timing of starting the shift control from the completion of the clutch connection, regardless of the starting conditions under any conditions, and realizes smooth clutch connection and acceleration control. However, in this case, the scheduled connection completion clutch capacity is a clutch capacity value that is on the release side from the state where the clutch is completely connected, and it is determined that the shift control start timing has been reached as described above. The clutch is slightly released. As described above, the shift control start timing is set to a time point when the clutch is slightly released, that is, at the shift control start timing, the clutch is not completely closed (connected) but slightly released. It is set to be. That is, even when the clutch is slightly released, the shift control is permitted at this point and the shift control is started immediately. Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show a hydraulic circuit of a hydraulic continuously variable transmission T having a clutch device and a transmission mechanism controlled by the method of the present invention. FIGS. 1 and 2 show the entire hydraulic circuit in which the oil passage 101 and the link mechanism 88 are connected to each other. The continuously variable transmission T has a constant displacement hydraulic pump P driven by the engine E via an input shaft 1 and a variable displacement hydraulic motor M having an output shaft 2 for driving wheels W. . The hydraulic pump P and the hydraulic motor M are provided with a first oil passage La communicating the discharge port of the pump P and the suction port of the motor M, and a second oil passage Lb communicating the suction port of the pump P and the discharge port of the motor M. And a hydraulic closed circuit is formed by the two oil passages. Of these two oil passages La and Lb,
When the pump P is driven by the engine E and the motor M is rotated by the hydraulic pressure from the pump P to drive the wheels W, the first oil passage La is driven by the engine E via the continuously variable transmission T. When the wheel W is driven,
High pressure. At this time, the second oil passage Lb is at a low pressure. On the other hand, the second oil passage Lb has a high pressure when the engine brake is applied by receiving the driving force from the wheel W, such as when the vehicle is decelerating. At this time, the first oil passage La has a low pressure. The discharge port of the charge pump 10 driven by the engine E is connected to a closed circuit via a charge oil passage Lh having a check valve 11 and a third oil passage Lc having a pair of check valves 3 and 3. ing. For this reason, the hydraulic oil pumped up from the oil tank 15 by the charge pump 10 and regulated by the charge pressure relief valve 12 is actuated by the check valves 3 and 3 so that the hydraulic oil of the two oil passages La and Lb has a lower pressure side. Oil supply. Further, a fourth oil passage Ld having a shuttle valve 4 having high and low pressure relief valves 6 and 7 connected to an oil tank 15 and connected to fifth and sixth oil passages Le and Lf is connected to the closed circuit. It is connected to the. The shuttle valve 4 is a two-port three-position switching valve.
The second oil passage La, Lb operates in response to a difference in oil pressure between the first and second oil passages La, Lb.
The oil passage Le is communicated with the oil passage Le, and the oil passage on the low pressure side is communicated with the sixth oil passage Lf. Thereby, the relief oil pressure of the high pressure side oil passage is adjusted by the high pressure relief valve 6, and the relief oil pressure of the low pressure side oil passage is adjusted by the low pressure relief valve 7. Between the first and second oil passages La and Lb, there is also provided a seventh oil passage Lg for short-circuiting both oil passages, and the seventh oil passage Lg controls the degree of opening of this oil passage. A clutch valve 5 including a variable throttle valve is provided. Therefore, by controlling the throttle amount of the clutch valve 5, it is possible to control the driving force transmission capacity (control of the clutch capacity) from the hydraulic pump P to the hydraulic motor M, and to perform clutch connection control at the time of starting or the like. Can be done. In this transmission, a hydraulic pump P is driven by an engine E, and a hydraulic motor M is rotationally driven by a hydraulic pressure from the hydraulic pump P, and the rotation is transmitted to a wheel W via an output shaft 2, W is driven. The hydraulic motor M is, for example, a swash plate axial piston motor. By controlling the angle of the swash plate, the speed ratio of the transmission T can be changed steplessly. The description of the control of the swash plate angle is well known and will not be repeated. On the other hand, the operation of the clutch valve 5 is controlled by a clutch servo unit 80 connected by a link mechanism 88.
The operation of the clutch servo unit 80 is controlled by a pair of solenoid valves 155 and 156 that receive a signal from the controller 100 and are controlled in duty ratio. Signals indicating the vehicle speed V, the engine speed Ne, the throttle opening θth, the swash plate inclination angle θtr of the hydraulic motor M, and the clutch opening θcl detected by the vehicle speed sensor are input to the controller 100. The controller 100 controls each of the solenoid valves based on these signals. The structure and operation of the clutch servo unit 80 will be described below in detail with reference to FIG.
The unit 80 includes a cylinder member 81, a piston member 82 slidably fitted to the cylinder member 81 in the left and right direction in the drawing, and a cover member 85 attached to cover the cylinder chamber in which the piston member 82 is fitted. And a spring 87 for urging the piston member 82 leftward in the figure. The piston 82a of the piston member 82 divides the above-mentioned cylinder chamber into two to form left and right cylinder chambers 83 and 84, and hydraulic pressure lines 112 and 110 are connected to the two cylinder chambers 83 and 84 via ports 86a and 86b. . The charge pump 1 is connected to the hydraulic line 110.
Hydraulic oil obtained by adjusting the discharge oil of 0 by the charge pressure relief valve 12 is guided through the hydraulic line 101. The hydraulic pressure of the hydraulic line 112 is determined by reducing the hydraulic pressure of the hydraulic line 111 having the orifice 111a branched from the hydraulic line 101 by the two solenoid valves 1 whose duty ratio is controlled.
55 and 156. Solenoid valve 156 controls the flow rate of hydraulic oil from hydraulic line 111 to hydraulic line 112 according to the duty ratio. The solenoid valve 155 is disposed between the hydraulic line 113 branched from the hydraulic line 112 and the hydraulic line 114 communicating with the drain side via the orifice 114a, and operates from the hydraulic line 113 to the drain side according to a predetermined duty ratio. Control oil spills. Accordingly, the charge pressure regulated by the charge pressure relief valve 12 acts on the right cylinder chamber 84 via the hydraulic line 110. Hydraulic oil having a pressure lower than the charge pressure is supplied to the left cylinder chamber 83 from the hydraulic line 112 by the operation of the two solenoid valves 155 and 156. Here, the right cylinder chamber 8
4 is smaller than the pressure receiving area of the left cylinder chamber 83, the force received by the piston member 82 due to the oil pressure in the left and right cylinder chambers 83 and 84 is equal to that of the right cylinder chamber 84 even if the biasing force of the spring 87 is taken into consideration. The hydraulic pressure in the left cylinder chamber 83 is lower than the hydraulic pressure P1 by a predetermined value P2 (P1
> P2). For this reason, the solenoid valves 155, 15
By controlling the hydraulic pressure supplied from the hydraulic pressure line 112 to the left cylinder chamber 83 to be greater than the predetermined value P2, the piston member 82 can be moved to the right by 6,
If the hydraulic pressure supplied to the left cylinder chamber 83 is controlled to be smaller than P2, the piston member 82 can be moved to the left. The lateral movement of the piston member 82 is
The power is transmitted to the clutch valve 5 via the link mechanism 88. The clutch valve 5 includes a fixed member 5a having a first valve hole 5b, and a rotating member 5c rotatably disposed in the fixed member 5a and having a second valve hole 5d. An arm 5e connected to the rotating member 5c is connected to the link mechanism 88, and the piston member 8
The rotation member 5c is rotated in accordance with the movement of the rotation member 2. When the rotating member 5c is rotated, the first and second valve holes 5b and 5
The overlapping amount of d changes, and the communication opening degree of both changes from fully open to fully closed. As shown in the drawing, when the piston member 82 has moved to the left as far as possible, the communication opening of the clutch valve 5 is fully opened, and thereafter, as the piston member 82 is moved to the right, the communication opening is fully closed. It changes gradually until. Here, the first valve hole 5b is connected to the continuously variable transmission T.
And the second valve hole 5d communicates with the second oil passage Lb, so that the communication opening degree of the first and second valve holes 5b and 5d is changed. By doing so, the opening degree of the seventh oil path Lg, which is a short-circuit path between the first and second oil paths La and Lb, can be changed, thereby controlling the clutch opening degree. That is, by controlling the duty ratio of the solenoid valves 155 and 156 based on a signal from the controller 100,
The clutch opening control is performed. Such solenoid valves 155, 15
Clutch valve 5 when starting vehicle by duty ratio control of 6
The opening degree control method will be specifically described based on the flowchart of FIG. In this control, first, the accelerator opening θacc (or the corresponding throttle opening θth) is read, and the vehicle speed V is read by the vehicle speed sensor. Next, the read vehicle speed V
Is greater than or equal to the lower limit of the scheduled clutch connection completion vehicle speed. The scheduled clutch connection completion vehicle speed is a vehicle speed for judging that the clutch connection for starting the vehicle smoothly through the half-clutch state corresponding to the magnitude of the throttle opening at the time of starting the vehicle has been completed. , FIG.
As shown by the dashed line A, the throttle opening is predetermined. Here, in a normal vehicle speed sensor, the detection accuracy is low at a low vehicle speed at which the clutch connection is completed, and there is a variation in a range indicated by hatching in FIG. For this reason, in the present invention, a characteristic (solid line B) indicating the lower limit of the range of the variation indicated by hatching in the figure is set, and the vehicle speed V detected by the vehicle speed sensor exceeds the lower limit, and the clutch connection It is determined whether or not the user has entered an area where completion is possible. When the vehicle speed is equal to or lower than the lower limit value and the clutch connection is not completed, the opening of the clutch valve 5 is changed to the engine speed and the throttle opening in order to make the clutch valve 5 half-clutched for smooth start. Is controlled so that the target clutch opening is set in accordance with On the other hand, when the vehicle speed is equal to or higher than the lower limit value and the clutch connection can be completed, it is determined whether the actual clutch opening is larger than the planned connection completion clutch opening. The opening degree of the scheduled connection completion clutch is an opening degree at which a good transition can be made from the clutch connection control to the gear ratio control, and the clutch valve 5 is fully closed (the rotation angle of the rotating member 5c is 90 °). (A), the opening is set to be slightly opener. For this reason, as shown in FIG. 6, the scheduled connection completion clutch opening is set as a broken line E or a chain line F on the opening side from the line D where the clutch valve 5 is fully closed. In the case of the broken line E, a constant opening is always set regardless of the throttle opening, and in the case of the chain line F, the larger the throttle opening is, the larger the clutch connection completion opening is set to the opening side. Is done. In this manner, it is determined whether or not the clutch opening has become equal to or less than the planned connection completion clutch opening. As a result, if the vehicle is not yet closed to the completion clutch opening, the vehicle speed becomes the clutch connection completion. Even at the obtained vehicle speed, it is determined that the clutch connection has not been completed.
In this case, the shift to the shift control is not started, and the opening of the clutch valve is set according to the engine speed and the throttle opening in order to realize a half-clutch state and to perform a smooth start. The clutch connection control is continued so as to reach the target clutch opening. On the other hand, when the vehicle speed is equal to or higher than the lower limit value and the clutch connection can be completed, and the clutch opening is equal to or less than the planned connection completion clutch opening (closer side than the planned connection completion clutch opening), It is determined that the connection of the clutch has been completed. At this time, the shift to the shift control is permitted while the clutch connection control is continued, and the control is shifted to the control for gradually reducing the gear ratio to perform smooth acceleration. As can be seen from the above description, when the opening of the clutch valve is fully open, the clutch is in the released state and its driving force transmission capacity is zero. At the time of starting, when the clutch valve is gradually closed, the clutch enters a partially connected state, that is, a half-clutch state, the driving force transmission capacity is increased, the clutch is gradually connected, and the clutch opening is fully closed. The connection of the clutch is completed. As can be seen from the above, in the case of the clutch valve, the clutch capacity is zero when the valve is fully opened, and becomes maximum when the valve is fully closed. Here, a method of starting and running the vehicle by shifting from the clutch connection control to the gear ratio control at the time of starting will be described with reference to FIG. In this figure, the vertical axis shows the engine speed, the horizontal axis shows the vehicle speed, and the solid lines L and H show the relationship between the engine speed and the vehicle speed when the gear ratio is maximum and minimum, respectively. When the vehicle starts running, the throttle opening is released and the engine rotation increases from the state where the vehicle speed is zero and the engine is idling, and at the same time, the clutch valve is closed, the clutch is connected, and the vehicle is driven. In this clutch connection, the connection completion engine speed and vehicle speed differ depending on the throttle opening. When the throttle opening is large, the clutch connection is made at a high engine speed as shown in FIG. When the degree is small, the clutch connection is made at a low engine speed as shown by a. Completion of the clutch connection is determined by the method shown in the flowchart of FIG. 4. When it is determined that the clutch connection has been completed, the start of the shift control is permitted. This allows a smooth transition to shift control (however,
When the throttle opening is large, as indicated by the line,
First, a speed change control is performed to increase the speed while maintaining the maximum speed ratio), and the speed is shifted from the maximum to the minimum state so that the vehicle speed increases while the engine speed is maintained substantially constant (linear or torque). When the gear ratio is shifted to the minimum, the vehicle speed is then increased in accordance with the increase in the engine speed while keeping the gear ratio at the minimum (running indicated by lines C and D). In the above description, the hydraulic continuously variable transmission has been described as an example. However, the method of controlling the shift from the clutch connection control to the shift control according to the present invention is not limited to this. Needless to say, the same can be used in the continuously variable transmission described above. As another continuously variable transmission, for example, there is a belt-type continuously variable transmission. In this transmission, a friction clutch is often used instead of a clutch valve. In this case, the engagement of the friction clutch is controlled instead of the clutch opening, and the transition from the disengaged state to the connected state of the clutch is controlled to perform the clutch connection control. In the case of a clutch valve, the clutch capacity is controlled by its opening degree control, and at the time of starting, the clutch is released and the capacity is connected from a state of zero to control the connection so that the capacity is maximized. In the case of a clutch, clutch capacity control is performed by controlling the degree of engagement. As described above, according to the present invention, the lower limit value of the planned clutch connection completion vehicle speed corresponding to the throttle opening and the planned connection completion clutch capacity which is the clutch capacity on the release side of the complete connection capacity are determined. When the vehicle speed is set in advance and the actual vehicle speed becomes equal to or higher than the lower limit value of the planned clutch connection completion vehicle speed and the actual clutch capacity becomes larger than the planned connection completion clutch capacity at the time of starting, it is determined as the timing for starting the shift control. Then, the shift control is started. As described in <Prior Art> and <Problem to be Solved by the Invention> described above, in the related art, the shift control is performed after waiting for the clutch connection to be completed. Is inaccurate, which causes problems such as a rise in engine rotation and an inadequate feeling of acceleration. Therefore, in the present invention, the point at which clutch engagement is almost completed (the point at which the clutch is slightly released) is set as the shift start timing. The purpose is to make the transition from clutch connection completion control to shift control smooth by making a judgment. As can be seen from the above, the present invention is based on the assumption that the connection of the clutch is completed in the same manner as in the subject technology, and does not stop the connection control of the clutch when the shift start timing is determined. The control for completing the clutch connection is performed in the same manner as the conventional control. If the clutch connection completion is determined only based on whether the clutch capacity is equal to or greater than the planned connection completion clutch capacity, if the vehicle is on an uphill road, a flat road, or a downhill road at the start, the vehicle speed at that time is different. However, there is a problem that it is difficult to shift to smooth shift control, and when the completion of the clutch connection is determined based only on the vehicle speed, the vehicle speed is low when the clutch is connected, so that the detection accuracy of the vehicle speed is low, and it is determined that the actual connection is completed. And it is difficult to shift to smooth shift control. However, in the control method of the present invention, in addition to determining whether the actual vehicle speed is equal to or higher than the lower limit value of the planned clutch connection completion vehicle speed, it is determined whether the clutch capacity is equal to or higher than the planned connection completion clutch capacity. Has become. That is, it is determined that the connection of the clutch is completed only when the vehicle speed sensor exceeds the lower limit and the clutch capacity becomes equal to or more than the planned connection completion clutch capacity. This makes it possible to accurately judge the clutch connection completion even when the vehicle starts under any conditions. After that, if the gear ratio control is permitted, smooth clutch connection and acceleration control are realized. [0037]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission having a clutch device and a continuously variable transmission mechanism to which transition control is performed by the method of the present invention. FIG. 2 is a schematic view showing the clutch device. FIG. 3 is a cross-sectional view of a clutch servo unit that controls clutch opening of the clutch device. FIG. 4 is a flowchart illustrating a method for determining whether clutch connection is completed when shifting from clutch connection control to shift control. FIG. 5 is a graph showing a planned clutch connection completion vehicle speed with respect to a throttle opening used for clutch connection completion determination. FIG. 6 is a graph showing a clutch connection completion opening with respect to a throttle opening used for clutch connection completion determination. FIG. 7 is a graph showing running characteristics of a vehicle provided with the continuously variable transmission. [Description of Signs] 4 Shuttle valve 5 Clutch valve 80 Clutch servo unit 155, 156 Solenoid valve 100 Controller E Engine T Continuously variable transmission W Wheel

Claims (1)

(57) [Claims] In a continuously variable transmission for vehicles equipped with a clutch that controls the output transmission of the engine and a transmission mechanism that variably controls the gear ratio from maximum to minimum, the engine throttle is released when the vehicle is stopped and the vehicle starts. When letting
A method for determining a timing to start a shift control when a clutch is connected by performing control for connecting a clutch with an increase in an engine and a vehicle speed, wherein the scheduled clutch connection corresponding to the throttle opening of the engine is performed. A lower limit value of the completed vehicle speed is set in advance, and a clutch capacity when the clutch is on the disengaged side from a completely connected state is set in advance as a planned connection completed clutch capacity. When the actual vehicle speed and the actual clutch capacity of the clutch are detected and the throttle opening is released to start the vehicle,
The actual clutch capacity is controlled to be the target clutch capacity set in accordance with the actual engine speed and the actual throttle opening, control is performed to connect the clutch, and when this clutch connection control is being performed, The actual vehicle speed is compared with the lower limit value of the planned clutch connection completion vehicle speed corresponding to the actual throttle opening and the actual vehicle speed, and the actual vehicle speed is compared with the actual throttle opening. After detecting that the actual clutch capacity has reached the planned connection completed clutch capacity after the corresponding planned clutch connection completed vehicle speed becomes equal to or more than the lower limit value, it is determined that it is time to start the shift control. A method for determining a shift control start timing when a vehicle continuously variable transmission starts.