JP2522219B2 - Clutch control mechanism for continuously variable transmission - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clutch control mechanism for a continuously variable transmission that is preferably applied to automobiles, tractors, and other industrial machines that utilize a fluid mechanical continuously variable transmission.

[0002]

2. Description of the Related Art A general hydromechanical continuously variable transmission is shown in FIG.
The configuration is shown schematically in FIG. This one is
A low speed mechanical transmission system having first, second and third input / output terminals 1, 2 and 3 and passing between the first input / output terminal 1 and the second input / output terminal 2. a, the first input / output terminal 1 and the third
High-speed mechanical transmission system b that passes between the
And a second input / output shaft 7a of one fluid pump / motor 7 are connected to a second input / output end 2 of the differential mechanism 4 via gears 5 and 6. With the third
Of the other fluid pump / motor 8 is connected to the input / output end 3 of the other via gears 9 and 11, and both pumps /
A fluid transmission mechanism 12 that forms variable-speed fluid transmission systems A and B by the motors 7 and 8 and a transmission end of the low-speed mechanical transmission system a are brought into contact with and separated from a center boss 13, which is a common rotating element. It comprises a low speed side clutch 14 and a high speed side clutch 15 for moving the transmission end of the high speed side mechanical transmission system b to and from the center boss 13. The center boss 13 is connected to the output shaft 18 via gears 16, 17, 20, 21. Wheels 26 are fixed to the output shaft 18.

The differential mechanism 4 is of a planetary gear type in which a sun gear 22 is arranged inside a plurality of planetary gears 21 arranged equidistantly in the circumferential direction and a ring gear 23 is meshed outside. The center of a gear retainer 24 that supports each planetary gear 21 is the first input / output end 1, and an output shaft 25 derived from the engine 19 is connected to the first input / output end 1. Further, the tip end of the support shaft 22a of the sun gear 22 serves as the second input / output end 2, and the gear 5 is fixed to the input / output end 2.
Further, the tip of the boss portion 23a of the ring gear 23 is set as the third input / output end 3, and the gear 9 is attached to the input / output end 3.
Is provided. Thus, the low speed side mechanical transmission system a
Is the planetary gear 21, the sun gear 22, the gear 5,
6 and gears 28 and 29, the boss portion 29a of the last gear 29 serves as a transmission end of the mechanical transmission system a. On the other hand, the mechanical transmission system b on the high speed side includes the planetary gear 21 and the ring gear 23.
And the boss portion 2 of the ring gear 23.
3a plays a role as a transmission end of the mechanical transmission system b.

The fluid transmission mechanism 12 includes a variable displacement type fluid pump / motor 7 and a variable displacement type fluid pump / motor 8 via a hydraulic circuit 31 similar to a normal HST. And the fluid pump / motor is connected in series.
The input / output shaft 7a of the motor 7 is connected to the support shaft 22a of the sun gear 22 via gears 6 and 5, and the input / output shaft 8a of the fluid pump / motor 8 is connected via gears 11 and 9 to the ring gear. It is connected to 23. An output direction switching mechanism (not shown) for switching between forward and backward movement is provided between the second input / output end 2 of the differential mechanism 4 and the one fluid pump / motor 7.

The clutches 14 and 15 are of the synchromesh type, and the clutches 14 and 15 have actuators 41 and 4 for connecting and disconnecting.
2 is attached. Also, the fluid pump motor 7,
8 also has a link mechanism 4 in which an actuator 44 for changing the displacement volumes DS, DR performs a predetermined operation.
It is attached via 4a.

By the way, in the shift control of the continuously variable transmission, in order to keep the actual engine speed at the target engine speed predetermined corresponding to the accelerator opening, the displacement volume DS,
The basic idea is to change the DR and adjust the speed ratio e. However, this continuously variable transmission has a high speed mode as well as a low speed mode for the purpose of ensuring a wide speed range.
The intermediate mode is set for the purpose of setting a mode and preventing frequent mode switching between both modes and reducing leakage loss in the hydraulic circuit. As a result, in this continuously variable transmission, in addition to the normal control for the displacements DS, DR, the switching control for the clutches 14, 15 for shifting between the modes,
Control is performed to reduce leakage in the hydraulic circuit. The range occupied by each mode corresponds to a region where the speed ratio e (output rotation speed / input rotation speed) is smaller than the intermediate set speed ratio em in the low speed mode, and the speed ratio e in the high speed mode. The intermediate mode corresponds to a region that becomes larger than the intermediate set pressure em, and the intermediate mode corresponds to a region where the speed ratio e is held equal to the intermediate set speed ratio em.

More specifically, the low speed mode is selected by connecting the low speed side clutch 14 and disengaging the high speed side clutch 15. At this time, the input shaft 25 and the output shaft 18 are connected via the low-speed side mechanical transmission system a passing between the first input / output end 1 and the second input / output end 2 of the differential mechanism 4. It is directly connected and a part of the power input from the engine 19 is directly transmitted to the wheels 26 through the mechanical transmission system a. Therefore, in the normal traveling state, the one fluid pump / motor 7 functions as a motor, the other fluid pump / motor 8 functions as a pump, and at the same time, the third mechanism of the differential mechanism 4 is operated. The rotational force of the input / output end 3 is transmitted in parallel to the wheel 26 through a hydraulic transmission system A formed between the fluid pumps / motors 7 and 8. When the low speed mode is selected, as shown in FIG. 5, the displacement volume DS of the one fluid pump / motor 7 is initially kept at the maximum as the speed ratio e increases. And the displacement volume DR of the other fluid pump / motor 8
Is increased, and after the displacement volume DR becomes maximum, it is held and in turn, the one fluid pump /
The displacement volume DS of the motor 7 is gradually reduced.

The high speed mode is the clutch 1 on the high speed side.
5 is selected and the low speed side clutch 14 is disengaged. At this time, the input shaft 25 and the output shaft 18 are connected via the high-speed side mechanical transmission system b passing between the first input / output end 1 and the second input / output end 2 of the differential mechanism 4. It is directly connected and part of the power input from the engine 19 is directly transmitted to the wheels 26 through the mechanical transmission system b. Therefore, the one fluid pump / motor 7 functions as a pump, the other fluid pump / motor 8 functions as a motor, and the second input / output terminal 2 of the differential mechanism 4 is used. Is transmitted in parallel to the wheel 26 through a fluid transmission system B formed between the fluid pumps / motors 7 and 8. Then, in this high speed mode, as shown in FIG.
As shown in FIG. 4, initially, the displacement volume DS of the one fluid pump / motor 7 is gradually increased while the displacement volume DR of the other fluid pump / motor 8 is kept at the maximum, and the displacement volume DS is gradually increased. After the displacement volume DS becomes maximum, the displacement volume DS is maintained and this time the displacement volume DR of the other fluid pump / motor 8 is gradually decreased.

On the other hand, the intermediate mode is for both clutches 14, 1
Selected by connecting 5 together. And
Immediately thereafter, the displacement volume DS of the fluid pump / motor 7 is controlled to control the differential pressure between the circuits of the fluid transmission systems A and B, that is, the differential pressure between the two circuits 31a and 31b to be substantially zero. Is done. As a result, the speed ratio e is locked to the intermediate set speed ratio em, and only the mechanical transmission systems a and b function in that state, and the input from the engine 19 is as high as the normal HST. The power is transmitted to the wheels 26. Therefore, only in this intermediate mode, DS, D
Normal control over R is not done.

By the way, the clutch control for shifting between modes is carried out in two modes: pulling in to the intermediate mode and disengaging from the intermediate mode. Intermediate mode
The pulling into the drive is executed when the rotational speed difference between the transmission end of the low speed side mechanical transmission system a and the transmission end of the high speed side mechanical transmission system b falls below a certain value. If it is an access from the low speed mode side, the displacement volume DS of one fluid pump / motor 7 functioning as a motor is decreased toward point I in FIG. At that position, the rotation of the transmission end of the mechanical transmission system b on the high speed side and the rotation of the center boss 13 are synchronized to connect the clutch 15 on the high speed side. Thereafter, when the displacement volume of the one fluid pump / motor 7 is increased toward the point P, the hydraulic circuit 1 is located at that position.
The differential pressure of 2 can be maintained at substantially zero. If it is accessed from the high speed mode side, the displacement volume DS of one fluid pump / motor 7 functioning as a pump is reduced toward point II, and at that position the low speed side is reached. The rotation of the transmission end of the mechanical transmission system a and the rotation of the center boss 13 are synchronized to connect the low speed side clutch 14. After that, when the displacement volume of the one fluid pump / motor 7 is decreased toward the point P, the differential pressure of the hydraulic circuit 12 can be maintained at substantially zero at that position.

On the other hand, the separation from the intermediate mode is
It is executed when the difference between the actual engine speed and the target engine speed exceeds a certain value. If it is the separation to the high speed mode side, the one fluid pump / mode
By increasing the displacement volume DS of the motor 7 from point P to point II in FIG. 5, the fluid pump / motor 7 functions as a pump and the fluid pump / motor 8 functions as a motor. To be able to. As a result, the transmission torque to the transmission end of the low speed side mechanical transmission system a is released, so that the low speed side clutch 14 can be disengaged. If it is the separation to the low speed mode side, the displacement volume DS of the one fluid pump / motor 7 is decreased from the point P to the point I, and the fluid pump / motor is reduced. The motor 7 functions as a motor and the fluid pump / motor 8 can function as a pump. As a result, the transmission torque to the transmission end of the mechanical transmission system b on the high speed side is released, so that the clutch 15 on the high speed side can be disengaged.

[0012]

However, according to the above-mentioned conventional clutch control, the clutch 15 on the high speed side is disengaged when shifting from the intermediate mode to the low speed mode with the engine brake applied. Hassle, and as a result,
There is a problem that an engine stall is likely to occur when it is desired to change gears rapidly, such as during a sudden break. More specifically, FIG. 6 shows the states of the two fluid pumps / motors 7 and 8 at the time of engine braking, corresponding to FIG. 5, and is shown in the low speed mode and the high speed mode. The control for the displacement volumes DS, DR may be performed in the same manner, but this engine blur
In the key state, the torque is transmitted from the wheel 26 to the engine 19, so that both fluid pumps / motors 7 and 8 are transmitted.
The function of the pump as a pump and the function of the motor are reversed. For this reason, it is necessary to carry out the capacity operation opposite to the above-mentioned operation after the pull-in operation to the intermediate mode and before the withdrawal from the intermediate mode. That is, when drawing in the intermediate mode, if it is accessed from the low speed mode side, the displacement volume DS of one fluid pump / motor 7 functioning as a pump is shown in FIG. , Toward the point II, and at that position, the rotation of the transmission end of the mechanical transmission system b on the high speed side and the rotation of the center boss 13 are synchronized to connect the clutch 15 on the high speed side. After that, when the displacement volume of the one fluid pump / motor 7 is reduced toward the point P, the differential pressure of the hydraulic circuit 12 can be maintained at substantially zero at that position. If it is accessed from the high-speed mode side, the displacement volume DS of one fluid pump / motor 7 functioning as a motor is decreased toward point I, and at that position. The low speed side clutch 14 is connected by synchronizing the rotation of the transmission end of the low speed side mechanical transmission system a and the rotation of the center boss 13. Then, when the displacement volume of the one fluid pump / motor 7 is increased toward the point P, the differential pressure of the hydraulic circuit 12 can be maintained at substantially zero.

Further, if the separation from the intermediate mode is the separation to the high-speed mode side, the one fluid pump /
By decreasing the displacement volume DS of the motor 7 from the point P toward the point I, the fluid pump / motor 7 is driven by the motor.
Functioning as a pump, allowing the fluid pump / motor 8 to function as a pump. As a result, the transmission torque to the transmission end of the low speed side mechanical transmission system a is released, so that the low speed side clutch 14 can be disengaged. Also, if it is the separation to the low speed mode side, the one fluid pump /
By increasing the displacement volume DS of the motor 7 from the point P toward the point II, the fluid pump / motor 7 can function as a pump and the fluid pump / motor 8 can function as a motor. To do so. As a result, the transmission torque to the transmission end of the mechanical transmission system b on the high speed side is released, so that the clutch 15 on the high speed side can be disengaged.

As described above, in the continuously variable transmission, control for pulling in the intermediate mode and control for releasing from the intermediate mode are performed depending on whether the vehicle is running normally or the engine is being braked. The opposite must be done.
However, it is often difficult to correctly determine whether the vehicle is running normally or the engine is being braked. Since the control toward the neutral point P can be performed relatively easily by the feedback control using the differential pressure sensor 50 shown in FIG. 4, there are few problems, but there is no clue in the control related to the departure. The displacement volume DS of one fluid pump / motor 7 is swung in the forward and reverse directions by a trial and error, and as a result, it is determined whether or not the clutch 15 on the high speed side is actually disengaged. That is, in a normal traveling state, the displacement volume DS of the fluid pump / motor 7 is first
Is shifted from the point P in the decreasing direction as shown in FIG. 7, this direction coincides with the direction toward the point I shown in FIG. 5, and the fluid pump / motors 7, 8 are shown as shown in FIG. Since the function as the pump or the motor of the above-mentioned appears properly, the transmission torque to the transmission end of the mechanical transmission system b on the high speed side is released, and the clutch 15 on the high speed side can be smoothly disengaged. . However, when the displacement volume DS of the fluid pump / motor 7 is first shifted in the decreasing direction from the point P as shown in FIG.
Since it is opposite to the direction toward the point II shown in FIG. 10, it appears in the opposite direction to the original function of the fluid pump / motor 7, 8 as a pump or motor as shown in FIG. Instead of releasing the transmission torque to the transmission end of the mechanical transmission system b on the high speed side, the synchromesh clutch is engaged more deeply and the disengagement fails. Then, for the first time, the function of the fluid pumps / motors 7 and 8 is improved by correcting the displacement volume DS of the one fluid pump / motor 7 toward point II as shown in FIG. After being optimized, the disengagement of the clutch can finally be achieved. For this reason, it takes time to disengage the clutch 15 on the high speed side, and as a result, there is a problem that engine stall is likely to occur when a rapid gear shift is desired such as during sudden braking. Further, as a result, as shown in FIG. 10, there is a problem that a peak pressure is generated in the discharge pressure of the other fluid pump / motor 8 in the hydraulic circuit 12.

It is an object of the present invention to provide a clutch control mechanism for a continuously variable transmission which can effectively solve such problems.

[0016]

In order to achieve the above object, the present invention employs the following configuration.

That is, the clutch control mechanism according to the present invention is
In the continuously variable transmission described above, from the middle mode to the low speed mode.
When the condition for leaving the engine is satisfied, first, the output torque of the engine is forcibly reduced to a negative value, and then the fluid pump / The displacement volume of the motor is changed in the direction of separation from the intermediate mode at the time of engine braking, and then,
It is characterized in that a control means for controlling the re-supply of fuel by disengaging the high speed clutch is provided.

[0018]

With this structure, the engine from which the fuel has been cut always has a negative torque, and the vehicle is always in the engine brake state. In this way, by positively specifying the control direction for the displacement volume of the fluid pump / motor as one direction, it is possible to smoothly disengage the clutch. However, since this control is performed only when the accelerator opening is small, immediately before the control is started, the engine is in a brake state, or even when the vehicle is in a normal running state, the positive drive torque is not so large. It never grows. Therefore, it is considered that even if the driver temporarily cuts off the fuel, no great shock is caused, and that the driver can be careful.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

This clutch control mechanism serves as a fuel injection device 51 incorporated in a part of the engine 19, an accelerator opening detection means 52 provided in association with the accelerator, and a control means referred to in the present invention. The eggplant mission controller 53 is provided. This mission control
The accelerator opening signal from the accelerator opening detection means 52 is input to the rotor 53, and the engagement / disengagement signals of both the clutches 14 and 15 or the difference detected by the differential pressure sensor 50 is used as in the conventional control. A pressure signal is input. Further, the controller 53 can output a fuel cut signal to the fuel injection device 51 to cut off the fuel to the engine 19 during that time.
Both fluid pumps / motors 7, as in conventional control,
A volume control signal can be output to the control actuator 44 of FIG.

In the conventional control, when the condition for leaving from the intermediate mode to the low speed mode is set, the accelerator opening read at that time is a preset value (for example, 0 to several). %) The control according to the present invention is started only when it is less than or equal to%. Therefore, the control is performed by first outputting the fuel cut signal to the fuel injection device 51, and then, by the trial and error as shown in FIG. 2, the displacement volume DS of the one fluid pump / motor 7. Always try to increase. As a result, as shown in FIG. 3, when one fluid pump / motor 7 can function as a pump and the other fluid pump / motor 8 can function as a motor, the clutch 15 on the high speed side can be used. The fuel injection device 5 after the fuel cut signal is output.
Operate 1 normally.

With such a structure, the engine 19 that has been subjected to the fuel cut always has a negative torque, and the vehicle is always in the engine brake state. In this way,
If the control direction for the displacement volume DS of the fluid pump / motor 7 is positively specified in one direction, it is promptly shown in FIG.
You can take the procedure from point P to point II,
As shown in FIG. 3, the function of the fluid pump / motors 7, 8 as a pump or motor can be matched to that in FIG. As a result, the transmission torque to the transmission end of the mechanical transmission system b on the high speed side can be quickly removed, and the clutch 15 on the high speed side can be smoothly disengaged. Therefore, in this continuously variable transmission, it is possible to reliably eliminate the problem that has conventionally been stalled during a sudden break or the like. Further, the problem that the peak value is generated in the discharge pressure of the other fluid pump / motor 8 in the hydraulic circuit 12 can be solved. Moreover, since this control is performed only when the accelerator opening is small, most of the time immediately before the control is started, the engine is in the brake state, or even in the normal running state, the positive drive is performed. The torque is not so large. Therefore, even if a temporary fuel cut is performed, a large shock is not caused, and the driver need only be aware of some shock.

By changing the ignition timing of the engine, the torque can be reduced and the same effect can be obtained.

[0024]

When the clutch control mechanism of the present invention is applied to the continuously variable transmission, it is possible to smoothly disengage the clutch from the intermediate mode to the low speed mode. Therefore, it is possible to smoothly shift, and it is possible to surely eliminate the problem that the engine stalls during the sudden brake and the problem that the peak pressure is generated at that time. . Further, since this control is performed only when the accelerator depression amount is small, there is no inconvenience that the driver is suddenly given a large shock.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a continuously variable transmission to which an embodiment of the present invention is applied.

FIG. 2 is a diagram showing control performed before and after an intermediate mode in the embodiment.

FIG. 3 is a view showing a state change of the fluid pump / motor at the time of mode switching in the embodiment.

FIG. 4 is a configuration diagram showing a conventional continuously variable transmission.

FIG. 5 is a diagram showing the control of a fluid pump / motor which is conventionally performed over the entire mode and its role during normal traveling.

FIG. 6 is a diagram showing the control of a fluid pump / motor which is conventionally performed over all modes and its role during engine braking.

FIG. 7 is a diagram showing a conventional control performed before and after an intermediate mode during normal traveling.

FIG. 8 is a view showing a state change of a fluid pump / motor when mode switching is performed during normal traveling in the related art.

FIG. 9 is a diagram showing a conventional control performed before and after an intermediate mode during engine braking.

FIG. 10 is a view showing a state change of the fluid pump / motor when the mode is switched during the engine brake in the related art.

[Explanation of symbols]

 1, 2, 3 ... Input / output end 4 ... Differential mechanism 7, 8 ... Fluid pump / motor 7a, 8a ... Input / output shaft 13 ... Common rotating element (center-boss) 14 ... Low speed side clutch 15 ... High speed Side clutch 19 ... Engine 53 ... Control means (mission controller) a ... Low speed side mechanical transmission system b ... High speed side mechanical transmission system A, B ... Fluid type transmission system e ... Speed ratio em ... Intermediate setting Speed ratio DS, DR ... Exclusion volume

Claims (1)

(57) [Claims] 1. A fluid pump which forms a pair of a low-speed side mechanical transmission system and a high-speed side mechanical transmission system in parallel between input and output ends, and a fluid pump paired in the middle of each of the mechanical transmission systems. /
A fluid transmission mechanism for connecting each input / output shaft of the motor and forming a variable speed fluid transmission system by these two fluid pumps / motors, and a transmission end of the low speed side mechanical transmission system for the input side. Or a low-speed side clutch that is brought into contact with or separated from the common rotating element provided on the output side, and a high-speed side clutch that brings the transmission end of the high-speed side mechanical transmission system into contact with or separates from the common rotating element, In the operating region where the speed ratio represented by the output rotation speed / input rotation speed becomes smaller than the intermediate set speed ratio at which the rotation speed difference between the low speed side transmission end and the high speed side transmission end becomes zero, the low speed side A low speed mode that connects only the clutch.
Mode, select a high speed mode in which only the clutch on the high speed side is connected in an operating range in which the speed ratio is larger than the intermediate set speed ratio, and further, set the intermediate ratio under the condition that the speed ratio is constant. In a continuously variable transmission configured to select an intermediate mode in which both clutches are connected together in an operating region where the speed ratio is kept equal, the disengagement condition from the intermediate mode to the low speed mode is At the time of preparation, on condition that the accelerator opening is equal to or less than a predetermined set value, first the output torque of the engine is forcibly reduced to a negative value,
Next, the control means for changing the displacement volume of the fluid pump / motor in the direction of disengagement from the intermediate mode at the time of engine braking, and thereafter for controlling the disengagement of the high speed clutch to re-supply the fuel. A clutch control mechanism for a continuously variable transmission characterized by being provided with.