JP2004301185A - Vehicle having toroidal type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle capable of securely preventing wheel spin when accelerating by speedily controlling torque for a driving wheel with the optimum slide rate always even if a road surface condition is changed. <P>SOLUTION: This vehicle 34 having the toroidal type continuously variable transmission is provided with a vehicle body 35, driving wheels 36 driving the vehicle body 35, a rotation power source 38 mounted inside the vehicle body 34, the toroidal type continuously variable transmission 41 which is mounted in the vehicle body 34 to change the number of revolutions of the rotation power source 38 and transmit it to the driving wheels 36 and adopts a torque control system for obtaining required output torque To by corresponding to only change of driving force for a speed change roller 14, and a controller 23 suppressing increase of output torque To of the toroidal type continuously variable transmission to obtain time series data μ(t), λ(t) of traction coefficient μ and slide rate λ at predetermined sampling timing and maintain evaluation function δμ/δλ (wherein, δ indicates a partial differential symbol) obtained by differentiating the traction coefficient μ by the slide rate λ based on the time series data μ(t), λ(t) at a positive number. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle having a toroidal-type continuously variable transmission, and more particularly to traction control thereof.
[0002]
[Prior art]
For example, when starting or accelerating or decelerating on a slippery road surface (although deceleration in this case means deceleration only by operating the accelerator), the driver's operation of the accelerator wheels via the transmission in response to the accelerator operation When excessive torque is generated in the wheels, the driving wheels may spin, and stable driving may not be performed. Therefore, conventionally, traction control has been adopted which applies an optimum driving force to the wheels so as not to spin the driving wheels at the time of start or acceleration / deceleration, thereby enabling safe driving of the vehicle.
[0003]
Such traction control of the vehicle is to maintain the slip ratio of the tire within a predetermined value (15 to 20%) so that the tire does not slip on the road surface when a high driving force is required. Specifically, the slip ratio of the tire is calculated from the difference between the rotation speed of the drive wheel and the rotation speed of the driven wheel, and the throttle valve of the engine is driven to be closed so that the slip ratio falls within a predetermined value. This is performed by suppressing the torque of the wheels (see Patent Document 1).
Conventionally, only when the response from the engine throttle is not sufficient, the brake of the drive wheels is operated or the operating oil pressure in the transmission is controlled to suppress the excessive torque of the wheels.
[0004]
[Patent Document 1]
JP-A-2002-52960 (Claims 1 to 6)
[0005]
[Problems to be solved by the invention]
By the way, in a normal vehicle equipped with rubber tires, a road surface friction curve (traction curve) representing a relationship between a tire slip ratio and a traction coefficient changes according to road surface conditions, and therefore, a tire slip ratio also changes every moment depending on road surface conditions. It is known to change.
However, in the conventional traction control, the engine throttle is controlled so that the slip rate is maintained within a predetermined range despite the fact that the slip rate of the tire is a physical quantity that fluctuates with a change in the road surface state. Because only feedback control is performed, it is difficult to say that excessive torque on the wheel can always be suppressed based on the optimum slip ratio, and therefore, wheel spin can be effectively prevented on particularly slippery road surfaces such as snow. It may not be possible.
[0006]
Further, in the above-described conventional traction control, the torque of the drive wheels is suppressed by adjusting the engine throttle, so that the torque response of the drive wheels after detecting the occurrence of slip is relatively slow (about 100 ms). Therefore, it takes time for the control to stabilize, and the wheel spin may not be effectively prevented.
The present invention has been made in view of the above circumstances, and it is possible to always control the torque applied to the drive wheels quickly with an optimum slip ratio even when the road surface condition changes, thereby more reliably preventing wheel spin during acceleration / deceleration. It is an object of the present invention to provide a vehicle capable of performing the following.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has taken the following technical measures.
That is, the present invention is a vehicle having a toroidal continuously variable transmission including the following members (a) to (e).
[0008]
(A) a vehicle body (b) drive wheels for driving the vehicle body (c) a rotational power source mounted inside the vehicle body (d) a rotational speed of the rotational power source is changed and transmitted to the drive wheels A toroidal-type continuously variable transmission (e) that employs a torque control method that obtains a required output torque only in response to a change in the driving force of a support member that supports the rollers and is mounted in the vehicle body. While obtaining the time series data of the traction coefficient and the slip rate for each sampling time, so that the evaluation function obtained by differentiating the traction coefficient with the slip rate based on the time series data is maintained at a positive number, A control device for suppressing an increase in output torque of the toroidal type continuously variable transmission
In the vehicle according to the above configuration, the control device suppresses an increase in the output torque of the toroidal-type continuously variable transmission so that the evaluation function obtained by differentiating the traction coefficient with the slip ratio is maintained at a positive number. Therefore, even if the traction curve fluctuates with a change in the road surface condition, the output torque of the continuously variable transmission can be controlled based on the optimum slip ratio at which the traction coefficient is maximized.
The vehicle according to the present invention is equipped with a toroidal type continuously variable transmission that employs a torque control method that can obtain a required output torque only in response to a change in driving force applied to the speed change roller. Since the increase in the output torque of the transmission is suppressed by the above-described control device, the drive wheel torque can be more simply and quickly reduced compared to the conventional case where the engine throttle is closed and the torque of the drive wheel is suppressed. Traction control that suppresses torque can be performed.
[0010]
In the vehicle according to the present invention, it is preferable to use an estimated value calculated from the driving force applied to the speed change roller as the traction coefficient input to the control device. When such an estimated value is used, it is not necessary to provide a special sensor for detecting a traction coefficient when implementing the control method of the present invention, so that the manufacturing cost of the vehicle can be reduced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration diagram of a vehicle according to the present invention.
As shown in the figure, a vehicle 34 of the present embodiment is a rear-wheel drive type four-wheel passenger car, and a vehicle body 35, a drive wheel (rear wheel) 36 for driving the vehicle body 35, and A driven wheel (front wheel) 37 that supports the vehicle body 35 along with the wheels 36 so as to be able to run freely, an engine 38 as a rotational power source mounted on a front portion in the vehicle body 35, and a drive wheel that changes the rotational speed of the engine 38 And a transmission 39 mounted in the vehicle body 35 to transmit the power to the vehicle 36.
[0012]
The transmission 39 includes a torque converter 40 directly connected to an engine 38, and a continuously variable transmission 41 driven by the converter 40. The output of the continuously variable transmission 41 is a propeller shaft 42, a differential gear device 43, The power is transmitted to the drive wheel 36 via an accelerator shaft 44.
The vehicle 35 according to the present embodiment is equipped with a control device (hereinafter, referred to as an ECU) 23 that is an electronic control unit that collectively performs drive control of a throttle valve, engine control, transmission control, and the like. The ECU 23 is connected to a speed sensor 45 for detecting the rotation speed of the driving wheel 36 and a speed sensor 46 for detecting the rotation speed of the driven wheel 37. The output signals of these speed sensors 45, 46 Is taken into the ECU 23 in real time at the sampling time of.
[0013]
Further, as shown in FIG. 2, the ECU 23 has a speed sensor 30 for detecting a rotation speed ωi of the input disk 3 of the variator 1 and a rotation speed ωo of the output disk 12 of the variator 1, which will be described later. The speed sensors 31 are connected, and output signals of these speed sensors 30 and 31 are also taken into the ECU 23 in real time at a predetermined sampling time. Further, although not shown, the vehicle speed, the inclination angle of the vehicle body, and the depression amount of the accelerator pedal are obtained from a vehicle speed sensor, an inclination angle sensor, a pressure sensor provided corresponding to the accelerator pedal and a brake pedal, and an engine speed sensor, respectively. Information such as brake pedal depression pressure and engine speed is constantly input to the ECU 23.
[0014]
In this embodiment, a full toroidal type continuously variable transmission which is a kind of a toroidal type continuously variable transmission is adopted as the continuously variable transmission 41 constituting the transmission 39, and FIG. FIG. 2 is a schematic sectional view of a variator 1 constituting a main part of FIG.
As shown in FIG. 1, the variator 1 includes an input shaft 2 that is driven to rotate by an engine 38 of a vehicle 34 such as a passenger car, and input disks 3 are supported near both ends thereof. A concave curved track surface 3b is formed on one side surface of each input disk 3, and a spline hole 3a formed by cutting a plurality of grooves is formed on the inner periphery thereof.
[0015]
Each input disk 3 is assembled so as to be integrally rotatable with the input shaft 2 by inserting a spline shaft portion 2a formed on the input shaft 2 into the spline hole 3a. The right input disk 3 is restricted from moving rightward from the state shown in the figure by a locking flange 2b provided integrally with the input shaft 2. On the back surface of the left input disk 3 opposite to the raceway surface 3b, a casing 4 covering the entire back surface, a backup plate 5 inscribed on the inner periphery of the casing 4, and an input shaft 2 fixed to the input shaft 2. A locking ring 6 and a retaining ring 7 for restricting the disk 3 and the backup plate 5 from moving to the left in the axial direction, and a washer 8 mounted on the outer periphery of the locking ring 6 and applying a preload to the backup plate 5 are provided. Is provided.
[0016]
An O-ring 5 a is mounted on the outer periphery of the backup plate 5, and an oil chamber 9 a is formed in a space around the input shaft 2 surrounded by the inner surface of the casing 4, the back surface of the input disk 3, and the backup plate 5. Have been. The oil chamber 9a communicates with a first oil passage 2c extending in the axial direction of the input shaft 2 and a second oil passage 2d extending radially from the right end thereof. Hydraulic pressure is supplied. In this way, a hydraulic cylinder device in which the casing 4 and the backup plate 5 are used as the pressing cylinder 9 and the input disk 3 is used as the piston.
[0017]
An output unit 10 of the variator 1 is supported at the axial center of the input shaft 2 so as to be rotatable relative to the input shaft 2. The output unit 10 includes an output member 11 and a pair of output disks 12 supported by the output member 11 so as to be integrally rotatable. A concave curved track surface 12b is formed on one side of each output disk 12 facing the track surface 3b of the input disk 3. Further, a sprocket gear 11a that meshes with the power transmission chain 13 is formed on the outer periphery of the output member 11.
[0018]
A toroidal gap is formed between the raceway surface 3b of the input disk 3 and the raceway surface 12b of the output disk 12 facing the raceway surface, and the toroidal clearance is pressed against the raceway surfaces 3b and 12b to rotate. The three disk-shaped speed change rollers 14 are provided on the circumference equally (only one is shown in FIG. 5). Accordingly, a total of six transmission rollers 14 are arranged in a pair of left and right toroidal gaps. Each transmission roller 14 is rotatably supported around a rotation shaft 14a by a carriage (support member) 15, and the carriage 15 can adjust a relative contact position with respect to each of the raceway surfaces 3b and 12b. I have.
[0019]
In the variator 1 of the present embodiment, when a hydraulic pressure as a terminal load is applied to the oil chamber 9a via the first oil passage 2c, the left input disk 3 is urged rightward and transmitted via the speed change roller 14. The left output disk 12 is biased to the right. As a result, the left output disk 12 is urged rightward from the right output disk 12 via the output member 11. Further, the right input disk 3 is pressed from the right output disk 12 via the speed change roller 14, but since this input disk 3 is stopped by the locking flange 2b, a terminal load is applied to the entire variator 1. As a result, the left and right transmission rollers 14 are held between the two disks 3 and 12 at a predetermined pressure. When power is applied to the input shaft 2 in this state, torque is transmitted from the input disk 3 to the output disk 12 via a total of six transmission rollers 14.
[0020]
FIG. 2 is a circuit configuration diagram of the hydraulic control system of the variator 1.
Although FIG. 2 shows a circuit configuration relating to one transmission roller 14 for simplification of the description, in practice, a transmission cylinder 16 is provided for each transmission roller 14.
As shown in the figure, a carriage 15 inclined with a predetermined caster angle β is connected to the speed change roller 14. A speed change cylinder 16 is connected to the carriage 15 and moves forward or backward in response to a differential pressure Pr (= P1−P2) of the hydraulic pressures P1 and P2 supplied to the oil chambers 16a and 16b of the cylinder 16, respectively. A driving force (hereinafter, referred to as a reaction force) is applied.
[0021]
That is, the hydraulic circuit of the variator 1 is provided with a hydraulic pressure generation path formed by the first pump 17 and the first pressure control valve 18 and a hydraulic pressure generation path formed by the second pump 20 and the second pressure control valve 21. The hydraulic pressure controlled by the first pressure control valve 18 is supplied to the first oil chamber 16 a and the pressing cylinder 9 of the transmission cylinder 16, and the hydraulic pressure controlled by the second pressure control valve 21 is controlled by the hydraulic pressure of the transmission cylinder 16. The oil is supplied to the second oil chamber 16b.
[0022]
The pressure control valves 18 and 21 are operated by the command signal (indicated as Pr * in FIG. 1) of the ECU 23 to adjust the pressures of the first and second oil chambers 16a and 16b of the transmission cylinder 16. Thus, a reaction force in the forward or backward direction is applied to the carriage 15. The oil pressure applied to the first oil chamber 16a and the oil pressure applied to the second oil chamber 16b are detected in real time by the first and second pressure gauges 24 and 25, respectively. All are sent to the ECU 23 (indicated as Pr in FIG. 1).
[0023]
In the hydraulic circuit of the variator 1 according to the present embodiment, a hydraulic pressure generating circuit including a third pump 32 dedicated to lubricating oil and a relief valve 33 is provided separately from the first and second pumps 17 and 20. The discharge side of the third pump 32 is connected to a nozzle 28 disposed near each of the disks 3 and 12 via a cooling device (usually off) 26 including an oil cooler and the like and a flow control valve 27. Then, traction oil is injected from the nozzles 28 onto the raceway surfaces 3b and 12b of the disks 3 and 12, respectively. A temperature sensor 29 is arranged between the disks 3 and 12 and at a position where the traction oil ejected from the nozzle 28 is applied. The temperature sensor 29 detects the temperature of the jetted traction oil and sends an output signal to the ECU 23.
[0024]
Therefore, in the variator 1 of the present embodiment, the temperature to of the traction oil is read at a predetermined sampling time, the temperature to is compared with a predetermined limit temperature, and when the measured temperature to exceeds the limit temperature, the temperature to is exceeded. Feedback control by the ECU 23 is performed so as to operate the cooling device 26 in accordance with the degree, thereby preventing a spin loss of the speed change roller 14 due to an increase in oil temperature.
In the variator 1 according to the above configuration, the speed change roller 14 is interposed between the disks 3 and 12 in a state where the carriage 15 is inclined at the predetermined caster angle β. When a force imbalance occurs between the force and the output torque required to drive the output disk 12, the speed change roller 14 and carriage 15 cause the imbalance by tilting the rotation shaft 14a about the axis of the carriage 15. Try to break the balance.
[0025]
As a result, the position of the speed change roller 14 changes as shown by the two-dot chain line in FIG. 1, and the speed ratio between the disks 3 and 12 changes continuously. Therefore, for example, when a large resistance force such that the carriage 15 is pushed back against the reaction force is generated on the output disk 12, the speed change roller 14 changes the inclination angle of the rotating shaft 14a to generate a larger output torque. Thus, the speed ratio of the variator 1 is eventually "shifted down".
[0026]
That is, in the variator 1 of the present embodiment, torque control is performed such that a necessary output torque can be obtained instantaneously in response to only a change in the reaction force of the carriage 15 supporting the speed change roller 14 (ie, the driving force for the speed change roller 14). The speed ratio is changed as a result. Such a change in the torque and the speed ratio is simply executed only in response to an increase or decrease in the reaction force or a change in the external resistance (running resistance), and it has been confirmed that the change is extremely quick and efficient. In particular, in a full toroidal type continuously variable transmission, the responsiveness of torque control is higher than that of a half toroidal type due to its structure.
The three speed change rollers 14 on the left and right in FIG. 5 incline the rotation shaft 14a synchronously so as to be symmetrical left and right, and their inclination angles are the same for all six rollers.
[0027]
Next, traction control of the vehicle 34 performed by the ECU 23 will be described with reference to a flowchart of FIG.
First, the ECU 23 reads the rotation speed ω1 of the driving wheel 36, the rotation speed ω2 of the driven wheel 37, and the differential pressure Pr of the transmission cylinder 16 in real time at a specific sampling time Δt (the same time interval as the hydraulic control cycle) (step S1) Based on the measured values, a traction coefficient μ (t) between the drive wheel 36 and the road surface and a slip ratio λ (t) are calculated as time-series data (step S2).
Note that the above-described sampling can be performed not only at every predetermined time Δt but also at any other appropriate timing that can be smoothly controlled.
[0028]
Here, the slip ratio λ can be calculated from the rotational speeds ω1 and ω2 of the drive wheel 36 and the driven wheel 37 by the following equation (1).
λ = 2 × (ω1−ω2) / (ω1 + ω2) (1)
On the other hand, in the variator 1 of the present embodiment that performs the above-described torque control, the traction coefficient μ can be obtained indirectly from the reaction force on the speed change roller 14.
That is, in the variator 1, the output torque To and the differential pressure Pr of the transmission cylinder 16 that generates the reaction force of the transmission roller 14 have a relationship represented by the following equation (3).
[0029]
To = {rt × So × cosβ / (1-Rv)} × Pr (2)
However,
rt: toroid radius (see FIG. 5)
So: cross-sectional area of transmission cylinder β: caster angle (see FIG. 2)
Rv: speed ratio of variator (= −ωo / ωi)
ωo: output speed of the variator ωi: input speed of the variator
Further, the traction coefficient μ between the drive wheel 36 and the road surface and the output torque To of the variator 1 have a relationship represented by the following equation (3).
μ = To × Rg / (M × g × rw) (3)
However,
Rg: Torque ratio calculated from gear ratio M: Body mass g: Gravitational acceleration rw: Radius of drive wheel
Accordingly, the speed ratio (ratio) Rv calculated by reading the outputs ωi, ωo from the input speed sensor 30 and the output speed sensor 31 in real time at a predetermined sampling time Δt, and the hydraulic pressure read into the ECU 23 at the same sampling time Δt. By substituting the differential pressure Pr between P1 and P2 into the above equation (2) to obtain the output torque To generated on the output disk 12, and substituting the output torque To into the above equation (3), The traction coefficient μ of the drive wheel 36 can be obtained indirectly.
[0032]
Incidentally, it is known that the traction coefficient μ is a nonlinear function (road friction curve: also referred to as traction curve) substantially determined by only the slip ratio λ of the tire as shown in FIG. Since such a traction curve changes depending on the road surface condition, the slip ratio λ of the tire also changes every moment depending on the road surface condition, but if a traction curve 48 on a certain road surface is assumed, the inclination of the tangent line 49 is positive. In the range of the slip ratio λ, the traction coefficient μ does not fall below the peak value μmax with the increase of the slip ratio λ. Therefore, the spin of the drive wheel 36 is generated regardless of the shape change of the traction curve 48. It can be determined that they do not.
[0033]
Then, the ECU 23 calculates the traction coefficient μ and the slip rate based on the time series data μ (t) and λ (t) of the traction coefficient μ and the slip rate λ of the drive wheel 36 obtained at the specific sampling time Δt. An evaluation function ∂μ / ∂λ is calculated one by one by differentiating with λ (step S3). Then, the ECU 23 constantly compares whether or not the evaluation function ∂μ / 超 え λ exceeds a predetermined threshold value tan θmin (however, θmin is a positive number) (step S4). It is determined that there is a risk of the wheel 36 spinning, and a command is issued to the variator 1 to reduce the output torque To (step S5).
[0034]
As described above, in the vehicle 34 of the present embodiment, the ECU 23 operates the toroidal stepless step so that the evaluation function ∂μ / ∂λ obtained by differentiating the traction coefficient μ with the slip ratio λ is maintained at a positive number. Since the output torque To of the transmission 41 is suppressed from increasing, even if the traction curve 48 fluctuates with a change in the road surface condition, the traction coefficient μ is maximized based on the optimum slip ratio λ at which the traction coefficient μ becomes maximum. The output torque To of the continuously variable transmission 41 can be controlled.
[0035]
Further, in the vehicle 34 of the present embodiment, a toroidal-type continuously variable transmission 41 that employs a torque control method that can obtain a required output torque To only in response to a change in the driving force applied to the transmission roller 14 is mounted. Since the increase in the output torque To of the continuously variable transmission 41 is suppressed by the ECU 23, the driving wheel 36 is more easily and quickly and easily compared with the case where the engine throttle is slightly closed and the torque of the driving wheel 36 is suppressed. Traction control for suppressing the torque of the vehicle.
In particular, in the case of the full toroidal type, the responsiveness of the torque control is high as described above. Therefore, it can be said that the spin prevention effect accompanying the application of the traction control according to the present invention is large.
[0036]
Note that the above-described embodiments are all examples and are not restrictive. The scope of the present invention is defined by the appended claims, and all changes within the scope equivalent to the configuration described therein are also included in the present invention.
For example, in the above embodiment, the speed ratio Rv is obtained from the detection values of the speed sensors 30 and 31 for directly detecting the rotation speeds of the input / output disks 3 and 12, but instead of this, the inclination angle α of the speed change roller 14 is determined. The gear ratio Rv may be obtained indirectly by calculation using an angle sensor that detects (see FIG. 5).
[0037]
Specifically, the gear ratio Rv (= −ωi / ωo) can be obtained by the following equation (4), and thus the gear ratio Rv is obtained from the inclination angle α of the transmission roller 14 using this equation (4). be able to. However, in equation (4), rt is a toroid radius (see FIG. 5), and ru is a radius of the speed change roller 14.
ωi / ωo = (rt + ru · sinα) / (rt−ru · sinα) (4)
Further, the present invention can be applied to not only a full toroidal type continuously variable transmission but also a half toroidal type continuously variable transmission.
[0038]
【The invention's effect】
As described above, according to the present invention, even when the road surface condition changes, the torque to the drive wheels can be quickly controlled at an optimum slip ratio, so that wheel spin during acceleration is more reliably prevented. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a vehicle according to the present invention.
FIG. 2 is a circuit diagram of a hydraulic control system of a variator constituting a main part of the toroidal type continuously variable transmission.
FIG. 3 is a flowchart of traction control performed by an ECU.
FIG. 4 is a graph showing a relationship (traction curve) between a slip ratio and a traction coefficient.
FIG. 5 is a schematic sectional view of a variator.
[Explanation of symbols]
14 speed change roller 23 control unit (ECU)
34 vehicle 35 body 36 drive wheel 37 driven wheel 37 engine (rotary power source)
41 continuously variable transmission

Claims (2)

Body and
Drive wheels for driving the vehicle body,
A rotary power source mounted inside the vehicle body,
A torque control system which is mounted in the vehicle body so as to transmit the rotational speed of the rotational power source to the drive wheels by shifting the rotational speed, and which can obtain a required output torque only in response to a change in the driving force applied to the speed change roller. With the adopted toroidal type continuously variable transmission,
At a predetermined sampling timing, the traction coefficient and the time series data of the slip rate are obtained, and the evaluation function obtained by differentiating the traction coefficient with the slip rate based on the time series data is maintained at a positive number. A control device for suppressing an increase in output torque of the toroidal-type continuously variable transmission,
A vehicle having a toroidal continuously variable transmission, comprising: The vehicle having a toroidal-type continuously variable transmission according to claim 1, wherein an estimated value calculated from a driving force applied to a speed change roller is used as a traction coefficient input to the control device.

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