JPH01106742A - Method of controlling speed change of continuously variable transmission for vehicle - Google Patents

Abstract

PURPOSE:To obtain an engine brake operation which gives a deceleration nearly equal to a value required by the driver, by compensating a speed change ratio at the time of operation by the driver in accordance with the cumulative time of operation of a service brake operated by the driver, in an increasing direction. CONSTITUTION:A desired speed change ratio R is read from a previously set table in accordance with a vehicle speed. Then, a compensating value (OFFSET) of a speed change ratio corresponding to the operation of a brake pedal is calculated. If the engine brake is effected, it is judged whether a service brake is operated or not. If the service brake is not operated, the compensating value is held as it is. On the contrary, if the service brake is operated, it is judged whether the operation of the service brake is continued over a time of Talpha or not. When the time Talpha elapses, the compensating value stored in memory is added with an increment alpha so as to correct the compensating value.

Description

Detailed Description of the Invention A9 Object of the Invention (Field of Industrial Application) The present invention relates to a method of controlling a gear ratio in a continuously variable transmission for a vehicle, and more specifically, to an engine braking method when decelerating a vehicle. A method of controlling force using variable speed control will be discussed.

(Prior art) While the vehicle is running, the accelerator pedal is released and the accelerator opening (the amount of accelerator pedal depression or the opening of the engine throttle that is operated in conjunction with this accelerator pedal) is reduced to almost zero, and the engine brake is applied. It is common practice to decelerate the vehicle by obtaining

This also applies to vehicles equipped with a continuously variable transmission, but in a continuously variable transmission, the gear ratio can be adjusted and controlled steplessly, and by controlling this gear ratio, the magnitude of the engine braking force can also be controlled. From the viewpoint of driving feeling, etc., the method of controlling the gear ratio during deceleration tends to be particularly problematic.

For this reason, in the past, for example, when decelerating a vehicle by obtaining an engine braking effect, the gear ratio was mechanically and uniquely reduced, or As disclosed in the publication, there is a speed ratio control method that changes the speed ratio so as to change the engine braking force in accordance with the vehicle speed at that time.

(Problem to be Solved by the Invention) However, in such mechanical gear ratio control or gear ratio control that corresponds to vehicle speed, the engine braking force is determined only by the current driving condition. Therefore, for example, even if the driver wants to decelerate at the same vehicle speed, even if the driver wants to apply a larger engine brake to decelerate, the driver can only obtain the predetermined engine braking force. In such a case, the driver depresses the brake pedal to activate the service brake and increase deceleration. That is, in the conventional method of controlling engine braking force using shift control as described above, there is a problem in that the driver's requests at that time are not taken into account.

In view of the above, the present invention is designed to determine the driver's request for braking force based on the operation status of the service brake operated by the driver, and to change the engine braking force in response to this request. The purpose of the present invention is to provide a speed change control method.

9. Structure of the invention (means for solving the problem) As a means for achieving the above object, the speed change control method of the present invention includes:
When the accelerator opening is almost zero and the engine braking action is being used to decelerate, the operating time of the service brake operated by the driver is accumulated, and the gear ratio at that time is adjusted according to this accumulated time. is corrected in the direction of increase, so that the greater the service brake operation by the driver, the greater the engine braking force.

(Function) When controlling the gear ratio using the above gear change control method,
It is thought that the longer the service brake operation time (the time the brake pedal is depressed), the stronger the driver's request for deceleration. is increased, and the engine braking force is strengthened. Therefore, it is possible to obtain an engine braking force close to the deceleration required by the driver, and the driving feeling is improved.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a hydraulic circuit of a continuously variable transmission having a speed change control device controlled by the method of the present invention. The vehicle includes a hydraulic pump P, and a variable displacement hydraulic motor M having an output shaft 2 that drives wheels W. These hydraulic pump P and hydraulic motor M have a first oil passage La that communicates the discharge port of the pump P and the suction port of the motor M, and a second oil passage Lb that communicates the suction port of the pump P and the discharge port of the motor M. The two oil passages form a hydraulic closed circuit and are connected.

In addition, a charge pump 10 driven by the engine E
A charge oil passage L whose discharge port has a check valve 11
h and a third oil passage Lc having a pair of check valves 3.3, the hydraulic oil is pumped up from the oil sump 15 by the charge pump 10 and pressure regulated by the charge pressure relief valve 12. Due to the action of the check valve 3.3, the two oil passages La and Lb are
The oil is supplied to the low pressure side oil passage. Additionally, the oil sump 15 has high and low pressure relief valves 6.7.
A fourth oil passage Ld having a shuttle valve 4 to which fifth and sixth oil passages Le and Lf are connected is connected to the closed circuit. This shuttle valve 4 is a two-bottom, three-position switching valve that operates according to the oil pressure difference between the first and second oil passages La and Lb, and is operated on the higher pressure side of the first and second oil passages La and Lb. The oil passage on the high pressure side is made to communicate with the fifth oil passage Le, and the oil passage on the low pressure side is made to communicate with the sixth oil passage Lf.As a result, the relief oil pressure in the oil passage on the high pressure side is regulated by the high pressure relief valve 6, and the oil passage on the low pressure side is made to communicate with the sixth oil passage Lf. The relief oil pressure of the oil passage is regulated by a low pressure relief valve 7.

Furthermore, a seventh oil passage Lg is provided between the first and second oil passages La and Lb, and this seventh oil passage Lg is controlled by an opening/closing control device (not shown). A clutch valve 5 consisting of a variable throttle valve that controls the opening degree of the oil passage is provided.

Therefore, by controlling the throttle amount of the clutch valve 5, it is possible to perform clutch control that controls the transmission of driving force from the hydraulic pump P to the hydraulic motor M6. A speed change actuator that controls the speed ratio of the speed change mechanism T is a first and second speed change servo valve 30.50 connected by a link mechanism 45. This hydraulic motor M is a swash plate axial piston motor, and the swash plate angle is controlled by a speed change servo valve 30°50.
Its capacity is controlled.

The operation of the speed change servo valve 30.50 is controlled by the controller 1.
It is controlled by solenoid valves 151 and 152 whose duty ratio is controlled in response to a signal from 00. This controller 100 includes vehicle speed V, engine speed Ne, throttle opening θth, and swash plate inclination angle θtr of the hydraulic motor M.
Various signals indicating the above are inputted, and based on these signals, signals are outputted to control the respective solenoid valves so as to obtain desired running.

The structure and operation of each of the servo valves 30, 50 will be explained below with reference to FIG. 2.

This servo valve introduces high-pressure hydraulic oil led from the closed circuit of the continuously variable transmission tRT to the fifth oil path Le via the shuttle valve 4 through a high-pressure line 120 branched from the fifth oil path Le. , a first speed change servo valve 3 that controls the swash plate angle of the hydraulic motor M using the hydraulic pressure of this high-pressure hydraulic oil.
0, and a second speed change servo valve 50 that is connected to the first speed change servo valve 30 via a connection link mechanism 45 and controls the operation of this valve 30.

The first speed change servo valve 30 includes a housing 31 having a connection port 31a to which a high pressure line 120 is connected, a piston member 32 fitted into the housing 31 so as to be slidable left and right in the figure, and the piston member. A spool member 34 is fitted into the spool member 32 so as to be slidable from side to side.
It has the following. The piston member 32 includes a piston portion 32a formed at the right end portion and a cylindrical rod portion 32b corresponding to the piston portion 32a and extending to the left from the piston portion 32a.The piston portion 32a is formed within the housing 31. This cylinder hole 31c is inserted into the cylinder hole 31c.
The inside is divided into two to form left and right cylinder chambers 35 and 36, and the rod portion 32b is fitted into a rod hole 31d that is smaller in diameter than the cylinder hole 31c and corresponds thereto. In addition,
The right cylinder chamber 35 has a plug member 33a and a cover 3.
3b, and a spool member 34 is disposed passing through these.

A high pressure line 120 connected to the connection port 31a is connected to the left cylinder chamber 35 partitioned by the piston portion 32a through an oil passage 31b, and the piston member 32 is introduced into the left cylinder chamber 35. high pressure line 1
It receives a pushing force in the right direction in the figure by the hydraulic pressure of 20 mm.

A land portion 34a is formed at the tip of the spool member 34 so as to fit closely into the spool hole 32d, and two diagonal surfaces on the right side of the land portion 34a are formed in a predetermined axial direction. The dimensions are shaved off to form a recess 34b. A retaining ring 37 is fitted into the right side of this recess 34b, and is prevented from being removed by coming into contact with a retaining ring 38 fitted to the inner peripheral surface of the piston member 32.

The piston member 32 has a discharge passage 32e that can open the right cylinder chamber 35 to an oil sump (not shown) via the spool hole 32d in response to the rightward movement of the spool member 34, and a discharge passage 32e that can open the right cylinder chamber 35 to an oil sump (not shown) through the spool hole 32d in response to the leftward movement of the spool member 34. A communication path 32C is bored through which the right cylinder chamber 35 can communicate with the left cylinder chamber 36 via the recess 34b.

When the spool member 34 is moved to the right from this state, the land portion 34a closes the communication path 32c and opens the discharge path 32e. Therefore, the pressure oil from the high pressure line 120 flowing in through the oil passage 31b acts only on the left cylinder chamber 35, and moves the piston member 32 to the right to follow the spool member 34.

Next, when the spool member 34 is moved to the left, the concave portion 34b connects the communication path 32c to the right cylinder chamber 36, contrary to the above, and the land portion 34a closes the discharge path 32e. Therefore, the high pressure oil acts on both the left and right cylinder chambers 35 and 36, but due to the difference in pressure receiving area, the piston member 32
is moved to the left so as to follow the spool member 34.

Further, when the spool member 32 is stopped midway, the piston member 32 is placed in a hydraulic floating state due to the pressure balance between the left and right cylinder chambers 35, 36, and stops at that position.

In this way, by moving the spool member 34 from side to side, the piston member 32 can be moved to follow the spool member 34 using the hydraulic pressure of the high-pressure hydraulic oil from the high-pressure line 120, and thereby the link The displacement of the swash plate Mt of the hydraulic motor M connected to the piston member 32 via the piston member 39 can be variably controlled by rotating the swash plate Mt about the rotation axis Ms.

The spool member 34 is connected to a second speed change servo valve 50 via a link mechanism 45. This link mechanism 4
5 includes a first link member 47 having two substantially right-angled arms 47a and 47b that are rotatable about a shaft 47c, and a first link member 47 that is coupled to the tip of the arm 47b of the first link member 47 via a bottle. 2 link members 48, and the arm 4
The upper end of 7a is coupled to the right end of the spool member 34 of the first speed change servo valve 30, and
A lower end portion of the second link member 48 is coupled to a spool member 54 of the second speed change servo valve 50. Therefore, the spool member 5 of the second speed change servo valve 50
4 moves up and down, the spool member 34 of the first shift servo valve 30 is moved left and right.

The second speed change servo valve 50 has two hydraulic lines 10
2,104 are connected to the boat, 51a.

51b and this housing 51
A spool member 54 is fitted into the interior so as to be slidable up and down in the figure.
The spool member 54 includes a piston portion 54a and a rod portion 54b extending below and correspondingly to the piston portion 54a. The piston portion 54a is fitted into a cylinder hole 51c formed in the housing 51 to extend vertically, and divides the cylinder chamber surrounded by the cover 55 into upper and lower cylinder chambers 52 and 53. The rod portion 54b is fitted into a rod hole 51d that extends downward and is in contact with the cylinder hole 51c.

Note that the rod portion 54b has a concave portion 54e having a tapered surface.
A spool 58a of the top position determination switch 58 protrudes into the recess 54e, and as the spool member 54 moves upward, the spool 58 moves along the tapered surface.
By pushing up a, it is possible to detect whether the gear ratio of the hydraulic motor M has become minimum.

Additionally, hydraulic lines 102 and 104 are connected to the boats 51a and 51, respectively, to the upper and lower cylinder chambers 52 and 53, which are divided into two by the piston portion 54a.
b, and both hydraulic lines 102, 104
Hydraulic oil pressure and both cylinder chambers 5 supplied through
The spool member 54 is moved up and down in accordance with the magnitude of the hydraulic pressure applied to the piston portion 54a, which is determined by the pressure-receiving area of the piston portion 54a that receives the hydraulic pressure within 2.53.

This vertical movement of the spool member 54 is transmitted to the spool member 34 of the first speed change servo valve 30 via the link mechanism 45, causing it to move laterally. That is, by controlling the hydraulic pressure supplied via the hydraulic lines 102 and 104, the spool member 34 of the first shift servo valve 30 is controlled.
The piston member 32 is moved to control the swash plate of the hydraulic motor M, thereby controlling the capacity of the motor M, thereby controlling the gear ratio.

Specifically, by moving the spool member 54 of the second speed change servo valve 50 upward, the piston member 32 of the first speed change servo valve 30 is moved to the right to reduce the swash plate angle, and the hydraulic motor M is rotated. By reducing the capacity, the gear ratio can be reduced.

The hydraulic pressure in the hydraulic line 102 connected from the boat 51a to the inside of the upper cylinder chamber 52 is the hydraulic oil obtained by adjusting the pressure of the discharge oil of the charge pump 10 by the charge pressure relief valve 12, and is led through the hydraulic lines 101 and 102. , hydraulic line 1 connected from the boat 51b to the lower cylinder chamber 53
The hydraulic pressure of 04 is the hydraulic pressure of the hydraulic line 103 having an orifice 103a branched from the hydraulic line 102, by two solenoid valves 151.15 whose duty ratio is controlled.
This is the oil pressure obtained by controlling by 2. Solenoid valve 151 is connected to hydraulic line 10 having orifice 103a.
3 to the hydraulic line 104 according to the duty ratio, and the solenoid valve 152 is connected to the hydraulic line 1 branched from the hydraulic line 104.
05 and a hydraulic line 106 that communicates with the drain side via an orifice 106a, and causes hydraulic oil to flow from the hydraulic line 104 to the drain side in accordance with a predetermined duty ratio.

For this reason, the upper cylinder chamber 52 is connected via the hydraulic line 102.
The charge pressure regulated by the charge pressure relief valve 12 acts on the lower cylinder chamber 53 , but a pressure lower than the charge pressure is applied from the hydraulic line 104 to the lower cylinder chamber 53 due to the operation of the two solenoid valves 151 and 152 . is supplied to Here, since the pressure-receiving area of the upper cylinder chamber 52 is smaller than the pressure-receiving area of the lower cylinder chamber 53, the force that the spool member 54 receives due to the oil pressure in the upper and lower cylinder chambers 52 and 53 is due to the oil pressure Pu in the upper cylinder chamber 52. On the other hand, the oil pressure in the lower cylinder chamber 53 is a predetermined value Pjl lower than this value.
(Pu>Pjl). Therefore, the solenoid valves 151 and 152 control the hydraulic pressure supplied from the hydraulic line 104 to the lower cylinder chamber 53 to the predetermined value P1.
If it is controlled to become larger, the spool member 54 can be moved upward to reduce the swash plate angle of the hydraulic motor M, thereby reducing the gear ratio, and the hydraulic pressure supplied to the lower cylinder chamber 53 can be made smaller than Pffl. If controlled in this manner, the spool member 54 can be moved downward to increase the swash plate angle of the hydraulic motor M, thereby increasing the gear ratio.

Both solenoid valves 151 and 152 are driven and controlled by signals from the controller 100, and as can be seen from this, the signals from the controller 100 control the first and second shift servo valves 30.5.
0, the capacity of the hydraulic motor M, and the gear ratio are also controlled.

A vehicle equipped with a continuously variable transmission configured as described above is
Control of the gear ratio by the controller 100 when decelerating while operating the engine brake will be explained based on the flowchart in FIG. 3.

In this control, first, the roadway is read and this information is input, and the target gear ratio R for the current vehicle speed is read from a table set in advance corresponding to the vehicle speed. This table sets the gear ratio corresponding to the vehicle speed so as to obtain the engine braking force that is normally required during deceleration when driving on a flat road, for example.

Next, a correction value (0FFSET) of the gear ratio corresponding to the operation of the brake pedal by the driver is calculated.

This calculation is performed according to the subroutine shown in FIG. 4, and begins by determining whether or not the engine brake is operating. This judgment, for example,
This is done by detecting whether the accelerator opening (accelerator pedal depression amount or engine throttle opening) has become zero and deceleration is occurring. When the engine brake is not operating (not during engine braking), the control shown in FIG. 3 is not performed, so the correction value (0FFSET) is reset to zero.

When the engine brake is activated (in the case of engine braking), it is determined whether the service brake is activated, that is, whether the brake pedal is depressed by the driver, and the service brake is activated. If not, the correction value (0FFSET) is held as it is and this flow ends.

On the other hand, if the service brake is operated, it is detected whether or not this operation has continued for Tα time, and Tα
As time passes, the stored correction value (0FFSET
This correction value is corrected by adding an increment value α to >.

This subroutine of FIG. 4 is performed at predetermined intervals (for example, 10
m5), so that when the service brake is applied, the correction value (0FFSET) is modified by adding an increment α every Tα time. Even when the service brake is not applied, this correction value (0FFSET) is held as is as long as the engine brake is applied, and the next time the service brake is applied, this held value is incremented every Tα time. α
will be added and corrected. In other words, while the engine brake is operating, the correction value (0FFSET) is corrected and determined according to the cumulative operating time of the service brake, and when the accelerator pedal is depressed again and the engine brake is not applied, this correction value is changed. (0FFSE
T) is reset to zero.

Once the correction value (0FFSET) is calculated as described above, the process returns to the flow shown in Fig. 3 and this correction value (0FFSET) is calculated.
0FFSET) is added to the target gear ratio R to obtain a corrected target gear ratio. Therefore, a predetermined duty ratio signal is output from the controller 100 to the solenoid valves 151 and 152 so that the gear ratio of the continuously variable transmission matches the corrected target gear ratio.

As described above, when the engine brake is activated to perform deceleration, the speed change MfH is performed so as to increase the gear ratio according to the service brake activation time, which is the driver's intention to decelerate. This allows the engine braking force to be increased when a stronger deceleration is required, such as when the driver is depressing the brake pedal. That is, it is possible to generate an engine braking action that approaches the deceleration force requested by the driver, depending on the current driving situation.

In the above embodiment, a case where a continuously variable transmission consisting of a hydraulic pump and a hydraulic motor is used is shown, but the control method of the present invention is applicable not only to such a continuously variable transmission but also to other types of continuously variable transmission. It is a heat theory that can be used for transmissions. Furthermore, the gear ratio control device can be used not only as an electro-hydraulic device that controls a solenoid valve using an electric controller to operate a servo valve as in this example, but also as a gear ratio control device that directly controls the gear ratio using an electric motor, etc. A device that does this may also be used.

C1 As described in detail of the invention, it is thought that the longer the service brake operation time (the time the brake pedal is depressed), the stronger the driver's request for deceleration. When decelerating using brake action, the current gear ratio is corrected in the direction of increase in response to the accumulated operating time of the service brake operated by the driver. It is possible to obtain the engine braking force close to the deceleration required by the driver, and it is possible to improve the driving feeling.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram of a continuously variable transmission controlled by the method of the present invention, Fig. 2 is a cross-sectional view of the servo valve for first and second speeds, and Figs. 3 and 4 are the above-mentioned speed change control. FIG. 4...Shuttle valve 5...Clutch valve 10.
...Charge pump 30.50...Speed servo valve 100...Controller E...Engine P...
Hydraulic pump M... Hydraulic motor T... Continuously variable transmission W... Wheels Figure 3 Figure 4

Claims (1)

[Claims] 1) The speed of the engine connected to the input shaft is changed steplessly between the maximum gear ratio and the minimum gear ratio to drive the wheels connected to the output shaft, thereby driving the vehicle. In a continuously variable transmission for a vehicle that is used for driving, when the accelerator opening is set to almost zero and deceleration is performed using engine braking action, the operation time of the service brake by the driver's operation is accumulated, A speed change control method for a continuously variable transmission for a vehicle, characterized in that the speed ratio at that time is corrected in an increasing direction in accordance with the accumulated time, and engine braking force is increased.