JP2526955B2 - Drive system with continuously variable transmission - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drive system with a continuously variable transmission that can be widely used in various industrial fields such as industrial machines and vehicles.

[Prior Art] A so-called fluid pressure transmission (HST) is known as a continuously variable transmission using a fluid pump / motor. However, although this is excellent in continuously variable transmission, its efficiency is not always good and the speed range is not satisfactory. Therefore, by using the HST and the differential gear mechanism together, and sharing the power transmission between the HST and the differential gear mechanism, both the stepless speed change of the HST and the high efficiency of gear transmission are demonstrated. A fluid-mechanical continuously variable transmission (HMT) has been developed that makes it possible {references, hydraulic engineering (Tomoo Ishihara, Asakura Shobo), theory and practice of piston pump motors (Sadao Ishihara Corona)}. That is, this continuously variable transmission has first, second, and third input / output ends, and a low-speed side mechanical transmission that passes between the first input / output end and the second input / output end. System and a differential gear mechanism forming a high-speed side mechanical transmission system passing between the first input / output terminal and the third input / output terminal, and a second input / output terminal of the differential gear mechanism. An input / output shaft of one fluid pump / motor is connected and an input / output shaft of the other fluid pump / motor is connected to the third input / output end, and a variable speed hydraulic transmission system is formed by these two pumps / motors. Fluid transmission mechanism, a low speed side clutch for moving the transmission end of the low speed side mechanical transmission system to and from a common rotating element provided on the input side or the output side, and a transmission end of the high speed side mechanical transmission system. And a clutch on the high-speed side for bringing the common rotating element into and out of contact with the common rotating element. By switching the switch to contradictory manner, and is configured so as to select one of the low-speed mode or the high speed mode.

By the way, in such a continuously variable transmission, in the operating region where the speed ratio represented by the output rotation speed / input rotation speed is smaller than the intermediate set speed ratio at which the speeds of the both transmission ends are equal, the clutch on the low speed side is A low speed mode in which only the high speed side is connected is selected, and when the speed ratio increases and reaches the intermediate speed ratio, the high speed side clutch is connected and the low speed side clutch is released to shift to the high speed mode. It is common to do so. When shifting from the high-speed mode to the low-speed mode, the reverse operation is performed.

However, in such a system, there are very few opportunities to suspend the fluid transmission system, which has a lower efficiency than the mechanical transmission system, and therefore it is difficult to further improve the efficiency of the entire continuously variable transmission. And in such a thing, since the differential pressure is almost always generated between the circuits of the fluid transmission system, the durability of the fluid pump / motor and its accessories that compose this fluid transmission system is improved. There is a problem that it is difficult to improve.

Therefore, recently, when the speed ratio reaches an operating state in which the speed ratio approaches the intermediate set speed ratio by a certain amount or more, the displacement volume of the fluid pump / motor is controlled to control the intermediate lock in which both the clutches are connected. Pull up mode,
In the intermediate lock-up mode, the displacement volume of the fluid pump / motor is controlled so that the differential pressure between the circuits of the fluid transmission system becomes substantially zero.

Thus, according to such a configuration, the fluid pump / motor forming the fluid transmission system can be in a rest state in the intermediate lockup mode described above.

[Problems to be Solved by the Invention] However, while operating in such an intermediate lockup mode, the gear ratio of the continuously variable transmission is fixed, and the speed ratio thereof is maintained at the intermediate set speed ratio. To be done. Therefore, the control of converging the engine rotation speed to the target rotation speed must be interrupted only by adjusting the gear ratio of the continuously variable transmission. Therefore, even if there is no change in the load resistance of the vehicle, the engine speed increases by the amount that the efficiency of the continuously variable transmission increases, and the vehicle speed increases. Therefore, in order to maintain the vehicle speed, the driver operates the accelerator. There is a problem that it has to be returned a little.

The present invention aims to solve such problems.

[Means for Solving Problems] The present invention adopts the following configuration in order to achieve such an object.

That is, a drive system with a continuously variable transmission according to the present invention includes the continuously variable transmission as described above, and reaches a driving state in which the speed ratio approaches the intermediate set speed ratio by a certain amount or more. In this case, the displacement volume of the fluid pump / motor is controlled to bring it into an intermediate lock-up mode in which both clutches are connected, and in this intermediate lock-up mode, the differential pressure between the circuits of the fluid transmission system is increased. An intermediate lockup means for controlling the displacement volume of the fluid pump / motor so as to be substantially zero, and a displacement transmission element for transmitting the throttle operation amount to the fuel control end of the engine.
Transmission displacement control means is provided in the middle of the displacement transmission element and corrects the displacement to be transmitted in the intermediate lockup mode to converge the rotation speed of the engine to a target rotation speed at which fuel consumption is minimized. It is characterized by

[Operation] When the speed ratio approaches the intermediate set speed ratio by a certain amount or more while operating in the low speed mode or the high speed mode, in other words, the rotational speed difference between the low speed side clutch and the high speed side clutch approaches a certain value or less. In this case, the continuously variable transmission control that sequentially changes the gear ratio in the direction in which the actual engine speed approaches the target engine speed is interrupted, and the displacement volume of the fluid pump / motor is controlled so that both clutches are synchronized. And both clutches are forced into an intermediate lockup mode where both clutches are engaged. Then, in the intermediate lockup mode, the differential pressure between the high and low circuits is controlled to be substantially zero. Therefore, leakage loss and pressure-dependent torque loss in the fluid pump / motor are reduced. That is, the energy loss in this fluid transmission system is significantly reduced, and it becomes possible to transmit the power substantially only through the mechanical transmission system. Therefore, in this intermediate lockup mode, the transmission efficiency of the continuously variable transmission is improved, and the both fluid pumps / motors are substantially completely released from the load.

In this intermediate lockup mode, the operation displacement transmitted from the driver to the fuel control end of the engine via the displacement transmission element is adjusted by the transmission displacement control means, and the engine rotation speed becomes the target rotation speed at which the fuel consumption is best. It is controlled to converge to the speed. Therefore, in the intermediate lockup mode in which the continuously variable transmission control cannot be performed, the engine can be operated at a rotational speed corresponding to the accelerator opening. Therefore, it is possible to set the speed so that it does not change before and after lockup, and the driver is not forced to perform an unnecessary accelerator operation.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

The drive system of this embodiment transmits the output of the engine I to the traveling wheels IV via the continuously variable transmission II and the final reduction gear III.

The continuously variable transmission II has first, second and third input / output terminals 1, 2, 3 as schematically shown in FIG.
Of the low-speed side mechanical transmission system a passing between the input / output end 1 and the second input / output end 2 and high speed passing between the first input / output end 1 and the third input / output end 3 Side mechanical transmission system b is formed in parallel, and the second input / output end 2 of the differential gear mechanism 4 is connected to one fluid pump / motor 7 via gears 5 and 6. The input / output shaft 7a is connected, and the input / output shaft 8a of the other fluid pump / motor 8 is connected to the third input / output end 3 via gears 9 and 11, and the pump / motors 7 and 8 are used to adjust the variable speed. Fluid transmission mechanism 12 forming the fluid transmission systems A and B, a low speed side clutch 14 for bringing the transmission end of the low speed side mechanical transmission system a into and out of contact with a center boss 13 which is a common rotating element, and the high speed side And a high speed side clutch 15 for connecting and disconnecting the transmission end of the mechanical transmission system b on the side to and from the center boss 13. . The center boss 13 is connected to the output shaft 18 via gears 16 and 17.

The differential gear mechanism 4 is of a planetary gear type in which a sun gear 22 is provided inside a plurality of planetary gears 21 provided at equal intervals in the circumferential direction, and a ring gear 23 is meshed with the outside. Then, the center of the gary retainer 24 that supports the planetary gears 21 is the first input / output end 1,
An input shaft 25 connected to the engine I is provided at the input / output end 1. The tip of the support shaft 22a of the sun gear 22 is 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 the third input / output terminal 3, and the gear 9 is provided at the input / output terminal 3. Then, the low speed side mechanical transmission system a includes the planetary gear 21, the sun gear 22, the gear 5, the gear 6, and the forward clutch 2 described later.
6, the gear 28 and the gear 29, and 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 high speed side mechanical transmission system b is composed of the planetary gear 21 and the ring gear 23, and the boss portion 23a of the ring gear 23 serves as a transmission end of the mechanical transmission system b. There is.

The fluid transmission mechanism 12 is configured by connecting a variable displacement fluid pump / motor 7 and a variable displacement fluid pump / motor 8 in series via a hydraulic circuit 31 similar to a normal HST. Yes, the input / output shaft 7a of the fluid pump / 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 to the ring gear 23 via gears 11 and 9. Reference numeral 32 denotes a boost pump connected to the hydraulic circuit 31. And, the second of the differential gear mechanism 4
An output direction switching mechanism 33 is provided between the input / output end 2 and the one fluid pump / motor 7. The output direction switching mechanism 33 connects the gear 6 to the input / output shaft 7a of one fluid pump / motor 7 via the forward clutch 26, and
A one-way clutch 35 is provided between the gear 6 and the fixing member 34.
Is provided. The one-way clutch 35 is, for example, configured such that the claw 37 pivotally mounted on the fixing member 34 can be engaged with the claw wheel 36, does not restrain the rotation of the gear 6 when moving forward, and does not rotate the gear 6 when moving backward. The rotation of the second output end 2 of the differential gear mechanism 4 is restricted by prohibiting the rotation in the direction. In addition, as each of the clutches 14, 15, and 26,
A wet or dry multi-plate clutch can be used, or a so-called synchromesh type power interrupting mechanism can be used. The clutches 14, 15, and 26 can be intermittently operated by the actuators 41, 42, and 43.

In addition, this drive system changes the amount of operation displacement applied to the accelerator pedal 51 into an accelerator wire that is a displacement transmission element.
The output of the engine I can be controlled by transmitting the fuel to a fuel control end of the engine I, for example, a throttle operating shaft 59a for opening and closing a throttle valve 59 of a carburetor via 58. The accelerator wire 58 is divided into a wire front stage part 58a connected to the accelerator pedal 51 and a wire rear stage part 59b connected to the throttle control shaft 59a. A displacement adjusting device 60 that serves as a transmission displacement control means is provided between the wire front stage 59a and the wire rear stage 59b in cooperation with a computer to be described later.

The displacement adjusting device 60, as shown in FIG. 4 to FIG.
The operation input to the input terminal is differentially distributed and the first and second operations are performed.
Differential mechanism configured to be output from the output end of a planet
61 and a fixing mechanism 62 for fixing the second output end of the planetary differential mechanism 61 in a positionally changeable manner. Hereinafter, the configuration will be described in detail with reference to FIGS. First, the planetary differential mechanism 61 is arranged in the center of a box-shaped case 63, and one side wall 63a of the case 63 supports the wire front end portion 58a of the accelerator wire 58, and the other side wall 6 orthogonal thereto.
The wire rear part 58b of the accelerator wire 58 is supported by 3b. That is, the wire front portion 58a and the wire back-end section 58b is slidably received respectively wire tube 64 _1, 64 _2, they each wire tube 64 _1, 64 ₂
The end portions thereof are attached to the side walls 63a and 63b via the holders 65 ₁ and 65 ₂ . Then, the terminal end of the wire front stage part 58a is connected to the locking part 66a provided on the outer periphery of the input pulley 66 which is the input end of the planetary differential mechanism 61, and the starting end of the wire rear stage part 58b is 1 is connected to a locking portion 67a provided on the outer periphery of an output pulley 67 which forms an input end, and each wire 58
The a and 58b are wound around the respective pulleys 66 and 67. As shown in FIG. 5 and FIG. 6, the planetary differential mechanism 61 has a ring gear 68, a sun gear 69 arranged at an axial center portion of the ring gear 68, and an axis center of the sun gear 69 and the ring gear 68. The retainer 71 is rotatably installed.
And a plurality of planetary gears 72 which are supported by the retainer 71 via a shaft 71a and mesh with both the ring gear 68 and the sun gear 69. The input pulley 66 is fixed to the ring gear 68, and the output pulley 67 is attached to the support shaft 69a of the sun gear 69. Further, a hollow output shaft 73 forming a second output end is fixed to the lower end of the retainer 71, and the output shaft 73
Is rotatably supported on the inner circumference of the boss portion 63c of the case 63 via a bearing 73. The ring gear
68 is supported by a retainer 71 integrated with the output shaft 73 via a bearing 75, and supports the sun gear 69.
69a is rotatably supported by the output shaft 73 and the retainer 71 via bearings 76, 77. The output shaft 73 is locked by the fixing mechanism 62 so that its position can be adjusted. As shown in FIG. 7, the fixing mechanism 62 is configured by inserting a piston 82, which is operated by the pilot pressure taken out from the hydraulic circuit 31, into a cylinder 81 formed integrally with the boss portion 63c of the case 63. This piston 82
The rack portion 83 provided on the outer periphery of the above is engaged with the pinion portion 84 formed on the outer periphery of the output shaft 73. More specifically, the cylinder 81 is provided in a direction orthogonal to the output shaft 73, and lids 85 and 86 are closely screwed to both ends thereof.
The piston 82 has a cylindrical shape with a bottom, and is biased by the coil spring 87 toward one lid 85. Then, a pilot pressure introducing port 88 is provided in this one lid 85, and boost pressure is introduced into the pressure guiding chamber 89 formed between this lid 85 and the piston 82 via the restraint solenoid valve 90. I am trying.

When the high-speed solenoid valve 90 is closed, the piston 82 of the fixing mechanism 62 is held at the position where it is brought into contact with the one lid 85 by the urging force of the spring 87.
The output shaft 73 of the planetary differential mechanism 61 is locked at a fixed position. Therefore, the planetary gear 72 is held at a predetermined standby position, and the operation amount of the accelerator pedal 51 is sequentially transmitted as it is from the input pulley 66 and the ring gear 68 to the sun gear 69 via the planetary gear 72. Then, the output pulley 6 fixed to the upper end of the support shaft 69a of the sun gear 69
7 rotates in the direction opposite to the input, and the opening operation of the throttle valve 59 is performed according to the operation amount of the accelerator wire 58.

On the other hand, when the high-speed solenoid valve 90 is opened and the boost pressure is introduced into the pressure guiding chamber 89 of the fixing mechanism 62, the piston 82 moves while resisting the biasing force of the spring 87. The output shaft 73 of the planetary differential mechanism 61 that meshes with the rack portion 83 rotates around its axis within a predetermined angle range. Along with this, the position of the planetary gear 72 pivotally supported by the galtainer 71 changes, and the output displacement amount from the sun gear 69 is reduced. That is, the operation amount of the accelerator pedal 51 transmitted to the input pulley 66 is subtracted by an amount corresponding to the fixed position change amount of the output shaft 73 and output from the output pulley 67, and the opening degree of the throttle valve 59 is controlled. .

Further, the actuators 41, 4 of the continuously variable transmission II are
A computer 91 controls the actuators 44 and 45 for changing the displacement volumes of the hydraulic pumps / motors 7 and 8, and the high-speed solenoid valve 90.

The computer 91 is composed of a normal microcomputer system including a central processing unit 92, various memories 93, and an interface 94.
A signal p from the rotation speed sensor 95 for detecting the output rotation speed, a signal q from the rotation speed sensor 96 for detecting the input rotation speed, and a low speed mode are selected for the interface 94. From the signal r from the pressure sensor 97 provided in the circuit portion 31a of the hydraulic circuit 31 that becomes high pressure during operation, and from the pressure sensor 98 provided in the circuit portion 31b that becomes high pressure when the high speed mode is selected. Signal s and a signal t corresponding to the accelerator operation amount for controlling the output rotation of the engine I are respectively input. Further, from the interface 94, a signal u for operating the actuator 41 of the low speed side clutch 14 is output.
And a signal v for operating the actuator 42 of the high speed side clutch 15 and the actuator 43 of the forward clutch 26.
Signal w for operating the hydraulic pump / motor 7,
An actuator 44 for adjusting the displacement volume of 8,
Signals x and y for actuating 45 and actuator 46
And a signal g for controlling the high-speed solenoid valve 90 are output.

Then, in the memory 93 of this computer 91, the second
A program related to the control shown in the figure, that is, a program relating to capacity control in a low speed mode and transition control from the low speed mode to the intermediate lockup mode, and capacity control in a high speed mode and the high speed mode to the intermediate lockup mode The program relating to the shift control, or a program executed in the intermediate lockup mode, as schematically shown in FIG. 8, is incorporated.

Next, the operation of the drive system when the vehicle moves forward (the forward clutch 26 is engaged and the clutch 35 is released) will be described.

Speed ratio represented by the output rotation speed / input rotation speed is smaller operation region than the intermediate setting speed ratio e _m, only the clutch 14 for low speed side is a connected low-speed mode. Specifically, the speed ratio is sequentially calculated based on the output rotation speed detected by the rotation speed sensor 95 and the input rotation speed detected by the rotation speed sensor 96. Intermediate set speed ratio e _m corresponds to the speed ratio in the state where the speed is equal to a transmission end of said low speed side mechanical transmission system a, the high-speed side mechanical transmission end of the transmission system b. In this low speed mode, the input side and the output side are passed through 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 operating gear mechanism 4. Are directly connected to each other, and part of the input power is output through this mechanical transmission system a.
Directly transmitted to 18. At this time, the one fluid pump / motor 7 functions as a motor, and the other fluid pump / motor 8 functions as a pump. That is, the rotational force of the third input / output end 3 of the differential gear mechanism 4 is transmitted to the output shaft 18 through the hydraulic transmission system A formed between the quantity pump / motors 7, 8. In this low speed mode, the displacement volume of the other fluid pump / motor 8 is increased as shown in FIG. 2, and after the displacement volume is maximized, the one fluid pump is removed. /
By gradually reducing the displacement volume of the motor 7, the rotation speed of the output shaft 18 with respect to the rotation of the input shaft 25 increases. Then, in the control of the displacement volume of the fluid pumps / motors 7 and 8, the target rotation speed SD corresponding to the accelerator operation amount and the actual rotation speed SE of the engine I detected by the rotation speed sensor 56 become equal. Thus, the differential command signal is output to the actuators 44 and 45. The target rotation speed SD corresponds to the rotation speed of the engine I that provides the best fuel economy corresponding to each accelerator operation amount, and is determined in advance by experiments or the like.
The table is stored in the memory 93 as a table. Therefore, the target rotation speed SD in each operating state is selected based on the signal t corresponding to the accelerator operation amount that is sequentially input.

In such a low speed mode, when the rotational speed difference between the low speed side clutch 14 and the high speed side clutch 15 becomes smaller than a certain value, the mode shifts to the intermediate lockup mode.
That is, when shifting to the intermediate lockup mode, the displacement volume of the fluid pump / motor 7 is controlled to synchronize the low speed side clutch 14 and the high speed side clutch 15, and thereafter, if only the low speed side clutch 14 is used. It not, and also connected to the clutch 15 of the high-speed side, to lock the speed ratio is in the intermediate setting speed ratio e _m. Immediately thereafter, the displacement volume 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 pressure P _A of the circuit portion 31a and the pressure P _{B of the} circuit portion 31b. The differential pressure of is made zero. Therefore, this control operates the actuator 44 so that the detection values of the pressure sensors 57 and 58 provided on both circuit portions 31a and 31b of the fluid transmission mechanism 12 become equal.

Then, in the intermediate lockup mode, the control as shown in FIG. 8 is repeatedly executed. That is, first, in step 101, the actual rotation speed SE of the engine I detected by the rotation speed sensor 96 is divided by a target rotation speed SD predetermined corresponding to the optimum fuel consumption curve Q or the like (SE
/ SD) has exceeded a set value α greater than 1, and if it has been exceeded, step 10
Although the process proceeds to step 2 and shifts to the high speed mode, if it is determined that the speed has not been exceeded, the process proceeds to step 103. Step 103
Then, it is determined whether or not the above-mentioned value (SE / SD) is smaller than the set value β less than 1, and when it is determined that it is smaller,
The process proceeds to step 104 to return to the low speed mode, but if it is determined that the mode is not small, the process proceeds to step 105. When the above value (SE / SD) exceeds the set value α, the operator suddenly decreases the accelerator operation amount, which causes the target rotation speed SD to temporarily lower than the actual rotation speed SE. And the state in which the actual rotation speed SE temporarily increases sharply because the load on the output side suddenly decreases despite the operator holding the accelerator operation amount substantially constant. In such a case, since it is better to increase the load on the engine itself, the lockup state in the intermediate lockup mode is released and the mode shifts to the high speed mode. At this time, the displacement volume of one of the fluid pumps / motors 7 is increased by a little more to make the transmission torque from the low speed side mechanical transmission system a to the center boss 13 zero, and then the low speed side Release the clutch 14. Also,
When the value (SE / SD) becomes smaller than the set value β, the rotation speed of the engine I rises to a value corresponding to it even though the operator drastically increased the accelerator operation amount. This includes both the state in which the accelerator operation amount is not maintained and the state in which the operator keeps the accelerator operation amount substantially constant, but the actual rotation speed SE sharply decreases due to the sudden increase in the load on the output side. In such a case, since it is necessary to reduce the load on the engine I, the lockup state in the intermediate lockup mode is released and the low speed mode is entered.
At the time of this transition, the displacement volume of one of the fluid pumps / motors 7 is reduced by a slight amount to make the transmission torque from the mechanical transmission system b on the high speed side to the center boss 13 zero. , Release the clutch 15 on the high speed side.

On the other hand, in this intermediate lockup mode, when the routine proceeds to step 105, it is judged whether the pressure P _A of one circuit portion 31a of the fluid transmission mechanism is higher than the pressure P _B of the other circuit portion 31b. If it is determined to be large, the routine proceeds to step 106, where the displacement volume of the fluid pump / motor 7 on the high speed side is controlled in the increasing direction, and the routine proceeds to step 110. If it is determined that it is not larger, the process proceeds to step 107. In step 107, the pressure P _B of the other circuit portion 31b is
It is determined whether or not the pressure is higher than the pressure P _A of the one circuit portion 31a, and if it is determined to be higher, the process proceeds to step 108, and the displacement volume of the high speed side fluid pump / motor 7 is decreased. Control is performed, and the process proceeds to step 110. If it is not larger, it is judged that both the pressures P _A and P _B have become equal, and the routine proceeds to step 109. In step 109, the control of the displacement volume of the fluid pump / motor 7 is stopped, and the step
Go to 110. At step 110, the rotational speed SE of the engine I
However, it is determined whether or not the target rotational speed SD is higher than the target rotational speed SD, and only when it is determined that the target rotational speed SD is higher, the process proceeds to step 111. In step 111, the high speed solenoid valve 90 is opened. Then, the above routine is repeatedly executed at minute time intervals.

Therefore, in this intermediate lockup mode,
Speed ratio of the continuously variable transmission II is, is fixed to an intermediate setting speed ratio e _m, as well as both the circuit portion 31a of the fluid transmission mechanism 12, the differential pressure between 31b is maintained at zero, the accelerator wire 58
By adjusting the displacement of, the actual rotational speed SE of the engine I becomes
Target rotation speed SD determined according to accelerator operation amount
It will be controlled to converge to. Even when the above control is performed, when the above-mentioned sudden change in the situation occurs, the engine rotation speed SE temporarily deviates from the target rotation speed SD. , A low speed mode or a high speed mode.

When shifting to the high speed mode, a mechanical transmission system b passing between the first input / output end 1 and the third input / output end 3 of the differential gear mechanism 4 is formed and input. A part of the power is transmitted directly to the output shaft 18 through this mechanical transmission system b. At this time, the one fluid pump / motor 7 functions as a pump, and the other fluid pump / motor 8
Works as a motor. That is, the rotational force of the second input / output end 2 of the differential gear mechanism 4 passes through the fluid transmission system B formed between the one fluid pump / motor 7 and the other fluid pump / motor 8. It is transmitted to the output shaft 18. In this high speed mode, as shown in FIG. 2, the displacement volume of the one fluid pump / motor 7 is gradually increased, and after the displacement volume is maximized, the other fluid pump / motor 8 is displaced. By gradually reducing the displacement volume, the rotation speed of the output shaft 18 with respect to the rotation speed of the input shaft 25 increases.

The control of the displacement volume of the fluid pumps / motors 7 and 8 in this case also includes the target rotation speed SD corresponding to the accelerator operation amount and the actual rotation speed SE of the engine I detected by the rotation speed sensor 56. This is done by outputting operation command signals to the actuators 44 and 45 so as to make them equal.

In such a high speed mode, when the rotational speed difference between the low speed side clutch 14 and the high speed side clutch 15 becomes smaller than a constant value, the intermediate lockup mode is entered by the same procedure as described above.

If this is the case, the low speed clutch
When the rotational speed difference between the high speed side clutch 15 and the high speed side clutch 15 becomes smaller than a certain value, the normal continuously variable transmission control described above is interrupted and the low speed side clutch 14 and the high speed side clutch 15 are both in the connected state. Therefore, once the intermediate lockup mode is set, the deviation between the actual rotation speed SE of the engine I and the target rotation speed SD exceeds a certain range. Unless turned around, it is impossible to switch to the high speed mode or the low speed mode.
Therefore, even if such a relatively long-term use in the vicinity of the intermediate set speed ratio e _m, may be clutch 14 and high speed side clutch 15 of the low-speed side to prevent frequent switching it switched to. Therefore, the life of the clutches 14 and 15 and the actuators 41 and 42 that actuate the clutches 14 and 15 can be reasonably extended.

Moreover, in the intermediate lockup mode, the displacement volume of the fluid pump / motor 7 is controlled to control the circuit portion 31a.
And the pressure difference between the circuit portion 31b and the circuit portion 31b are made to be substantially zero, whereby the power transmission ratio of the hydraulic transmission systems A and B is made zero, and the power is generated only by the mechanical transmission systems a and b. It is designed to communicate. Although the efficiency of the fluid pumps / motors 7 and 8 constituting the hydraulic transmission systems A and B has been increasing in recent years, they are inferior to the mechanical transmission, and thus the power transmission of the hydraulic transmission systems A and B is as described above. If the operating range where the ratio becomes zero can be secured, the system efficiency can be improved. That is, as described above, when the differential pressure between the circuits is controlled to be substantially zero, the leakage loss inside the fluid pump / motors 7 and 8 is significantly reduced, and the torque loss depending on the pressure is also reduced. Therefore, the energy loss in the hydraulic transmission systems A and B is reduced, and the transmission efficiency of the continuously variable transmission is greatly improved. Further, if the chances of making the differential pressure between the circuits of the hydraulic transmission system to be substantially zero during the operation are increased, the durability of the fluid pumps / motors 7 and 8 and their accessories will be improved. .

FIG. 9 shows the mode switching mode of this embodiment when performing acceleration or deceleration, which is clearly different from the mode switching mode of the conventional example shown in FIG.

Moreover, in this drive system, the rotational speed SE of the engine I can be controlled to converge to the target rotational speed SD even in the intermediate lockup mode.
The engine I can always be operated in a desired state.
That is, in the intermediate lockup mode, the speed ratio of the continuously variable transmission II is fixed, so if the control by the transmission displacement control means is not performed, if the throttle operation amount is kept constant, When the load torque changes from T _A to T _B when the differential pressure (P _A −P _B ) between the circuit parts 31a and 31b of the continuously variable transmission II is controlled to be zero, it is shown in FIG. As described above, the operating state of the engine I shifts from point A to point B along the constant throttle opening curve d ₁ and the vehicle speed also changes (because the speed ratio is constant). . However, in this drive system, the transmission displacement due to the accelerator wire 58 is sequentially corrected, so that the engine I
The actual throttle opening is changed to a position corresponding to the curve d _2, and the operating state of the engine I shifts from the point a to the point c. Therefore, the efficiency of the continuously variable transmission II can be improved, and when the load resistance of the vehicle does not change, the driver is not forced to perform an unnecessary accelerator operation, and the system efficiency is reasonably and effectively achieved. It can be improved.

The differential gear mechanism is not limited to the planetary gear type as described above.

Further, the structure of the fluid transmission mechanism is not limited to that of the above embodiment, and various modifications can be made, for example, one of the fluid pumps / motors can be of a fixed displacement type.

Furthermore, in the above-described embodiment, the input distribution system having the differential gear mechanism arranged on the input side has been described, but the present invention can be similarly applied to the output distribution system.

Further, the configuration of the displacement transmission control means is not limited to the one described above, and various modifications can be made without departing from the spirit of the present invention, for example, by operating with a hydraulic pressure other than the boost pressure. is there.

[Effects of the Invention] As described in detail above, according to the present invention, when the switching range between the low-speed mode and the high-speed mode is approached, the intermediate lock-up mode is forcibly pulled in and the circuit between the circuits of the hydraulic transmission system is Not only does the differential pressure become approximately zero, but in the intermediate lockup mode, it does not force the driver to perform unnecessary accelerator operation, and it is possible to improve system efficiency reasonably and effectively. It is possible to provide a drive system with a device.

[Brief description of drawings]

1 to 9 show an embodiment of the present invention, FIG. 1 is a system explanatory diagram, FIGS. 2 and 3 are explanatory diagrams for explaining a control mode, and FIG. 4 is a transmission displacement control. FIG. 5 is a plan view of a displacement adjusting device which is a main part of the means, FIG. 5 is a vertical sectional view of the device,
FIG. 6 is a schematic plan sectional view showing a planetary differential mechanism portion of the device, FIG. 7 is a sectional view taken along line RR in FIG. 6, and FIG. 8 is a flow chart diagram schematically showing the contents of control. FIG. 9 is an explanatory diagram showing a mode switching mode. FIG. 10 is an explanatory view corresponding to FIG. 9 showing a conventional mode switching mode. I ... Engine, II ... Continuously variable transmission 4 ... Differential gear mechanism 7 ... One fluid pump / motor 8 ... Other fluid pump / motor 12 ... Fluid transmission mechanism 13 ... Common rotating element ( Center boss) 14 …… Low speed clutch 15 …… High speed clutch 51 …… Computer 56 …… Displacement transmission element (accelerator wire) 60 …… Transmission displacement control means (displacement adjusting device, computer) a, b …… Mechanical transmission system A, B ... Fluid type transmission system

Claims (1)

(57) [Claims] 1. A differential gear mechanism for forming a low-speed side mechanical transmission system and a high-speed side mechanical transmission system in parallel between input and output ends, and a pair in the middle of each of the mechanical transmission systems. A fluid transmission mechanism that connects respective input / output shafts of a fluid pump / motor and forms a variable speed fluid transmission system by both of these fluid pumps / motors, and a transmission end of the low-speed side mechanical transmission system at the input side or A low-speed side clutch that is brought into contact with and separated from the common rotating element provided on the output side, and a high-speed side clutch that brings into contact with and separates the transmission end of the high-speed side mechanical transmission system from the common rotating element are provided. In an operating range in which the speed ratio represented by the rotation speed / input rotation speed is smaller than the intermediate set speed ratio at which the rotation speed difference between the low speed side clutch and the high speed side clutch becomes zero, only the low speed side clutch is connected. Select low speed mode, A drive system in which a continuously variable transmission capable of selecting a high speed mode in which only the high speed side clutch is connected is disposed in a rear stage of an engine in an operating region in which a speed ratio is larger than the intermediate set speed ratio, When the speed ratio reaches an operating state in which the speed ratio approaches the intermediate set speed ratio by a certain amount or more, the displacement volume of the fluid pump / motor is controlled to bring it into an intermediate lockup mode in which the both clutches are connected together. Intermediate lock-up means for controlling the displacement volume of the fluid pump / motor so that the differential pressure between the circuits of the hydraulic transmission system becomes substantially zero in the intermediate lock-up mode; and a throttle operation amount for controlling fuel of the engine. A displacement transmission element that transmits to the end and a displacement transmission element that is interposed in the middle of this displacement transmission element and corrects the displacement that should be transmitted in the intermediate lockup mode Drive system with a continuously variable transmission apparatus characterized by comprising; and a transmitting displacement control means for causing the rotational speed to converge to the target rotational speed corresponding to the throttle opening of the engine.