JPH0526978B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed change control device for a belt-type continuously variable transmission, and more particularly to a speed change control device that arbitrarily maintains a minimum speed ratio.

[Conventional technology]

Regarding a speed change control device for a continuously variable transmission of this type, there is a prior art disclosed in, for example, Japanese Patent Laid-Open No. 55-65755. In this prior art, the speed change control valve supplies and drains line pressure to the main pulley side based on the relationship between the spring force according to the throttle opening and the pitot pressure according to the engine speed, thereby controlling the speed continuously. It is shown. Therefore, for example, when a centrifugal clutch and a continuously variable transmission are combined, the speed change characteristics are shown as a solid line in FIG. 4. That is, the clutch is engaged and the vehicle starts running at engine speeds N1 and N2 that are higher than the engine's idle speed Ni. At this time, since the throttle opening is large, oil is drained from the main pulley by the speed change control valve, so the vehicle runs at the maximum speed ratio l1. Thereafter, when the engine speed and pitot pressure increase due to an increase in vehicle speed, the gear shift starts, and the gear shifts up from P2 to P3 to reach the minimum gear ratio l2. Furthermore, when decelerating with the throttle fully closed, the pitot pressure is high to some extent when the vehicle speed is high, so the minimum gear ratio l2 is maintained and deceleration is performed from P3 to P4. The downshift starts at P4, when the engine speed drops to a point where the minimum spring force of the speed change control valve and the pitot pressure are balanced, and from then on, as the vehicle speed decreases, the engine speed changes from P4 to P5. Downshift to keep the ratio constant and return to the maximum gear ratio l1.

[Problem to be solved by the invention]

By the way, in the above prior art, the downshift start point P4 is uniquely set by the minimum spring force and pitot pressure characteristics of the shift control valve, and the downshift start point P4 is set at a relatively high vehicle speed V2.
Then, the engine brake is applied and deceleration is applied. As a result, the engine brake may be applied unnecessarily strongly and the deceleration may be long, which may be undesirable for the driver. In view of these problems in speed change control characteristics, the present invention aims to provide a speed change control device for a continuously variable transmission that can arbitrarily maintain a minimum speed change ratio and reduce the effectiveness of engine braking. purpose.

[Means to solve the problem]

To achieve the above object, the present invention has a main shaft on the engine side and a sub-shaft on the wheel side arranged parallel to this main shaft, and a main pulley and a sub-pulley with variable pulley intervals, and windings between the two pulleys. In a continuously variable transmission that has a drive belt and that controls the pulley ratio between the main and sub-shafts in a stepless manner by changing the effective diameter of the pulley using hydraulic pressure supplied to each servo device of the main and sub-pulleys, The hydraulic control circuit that communicates from the source to the servo device of the main and sub pulley has a pressure regulating valve that controls the line pressure supplied to the servo pulley servo device according to the gear ratio, and a spring force that corresponds to the throttle opening A transmission control valve that supplies and discharges line pressure to the main pulley servo device to change the gear ratio according to a relationship with pitot pressure depending on the rotation speed, and an oil passage that communicates the transmission control valve and the main pulley servo device. The flow path switching valve is provided with an inlet side port and an outlet side port communicating with the oil passage, and a second port whose outlet side port bypasses the speed change control valve and communicates with the line pressure oil passage on the pressure regulating valve side. and switching means for maintaining a minimum gear ratio by switching the flow path switching valve so that the second port communicates with the main pulley servo device in response to an electric signal from the detection means for detecting the running state. shall be.

[Effect]

In the present invention having the above configuration, the continuously variable transmission basically controls the line pressure of the auxiliary pulley with the pressure regulating valve according to the gear ratio, and controls the oil pressure of the main pulley with the speed change control valve to perform speed change control. Ru. For example, during deceleration with the throttle fully closed, the electric signal from the detection means is input to the flow path switching valve of the minimum gear ratio holding means, and the line pressure oil path is switched to communicate with the servo device of the main pulley. By maintaining the pulley servo device in a lubricated state, the minimum gear ratio can be arbitrarily maintained regardless of the operation of the gear change control valve.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, referring to FIG. 1, a continuously variable transmission with an electromagnetic powder clutch will be described as an example of a continuously variable transmission to which the present invention is applied. Reference numeral 1 is an electromagnetic powder clutch, and reference numeral 2 is a continuously variable transmission. The continuously variable transmission 2 can be roughly divided into a forward/reverse switching section 3, a pulley ratio converting section 4,
It is composed of a final reduction section 5 and a hydraulic control section 6. In the electromagnetic powder clutch 1, a drive member 9 having a built-in coil 8 is integrally connected to a crankshaft 7 from the engine, and a driven member 11 is integrally connected in the rotation direction by a spline to a transmission input shaft 10. These drives and driven members 9, 11 are loosely fitted through a gap 12, and electromagnetic powder is accumulated in this gap 12 from a powder chamber 13. Further, a slip ring 15 is installed on the drive member 9 via a holder 14, and a brush 16 that supplies a clutch current to the slip ring 15 is installed on the drive member 9 via a holder 14.
are in sliding contact. For this reason, when a clutch current is supplied to the coil 8 by, for example, operating the lever of the switching unit 3 or depressing the accelerator, electromagnetic powder is chained to the gap 12 of the drive and driven members 9 and 11 due to the lines of magnetic force generated between them. The bonding force in this case causes the driven member 11 to
The two slide together as one piece, and the clutch automatically connects. On the other hand, when the clutch current is cut off depending on the running condition during deceleration, the binding force due to the electromagnetic powder disappears, and the clutch is automatically cut off to prevent the engine from stalling. Next, in the continuously variable transmission 2, the switching section 3 connects the input shaft 10 from the clutch 1 and the input shaft 10.
The main shaft 1 of the pulley ratio converter 4, which is arranged coaxially with
7. Therefore, a reverse drive gear 18 that is integrally coupled to the input shaft 10 and a reverse driven gear 19 that is rotatably fitted to the main shaft 17 are configured to mesh with each other via a counter gear 20 and an idler gear 21. A switching clutch 22 is provided between the gears 18 and 19. Then, when the switching clutch 22 is engaged to the gear 18 side from the neutral position of the P or N range, the input shaft 1
When the main shaft 17 is directly connected to the D or L range and the switching clutch 22 is engaged to the gear 19 side, the power of the input shaft 10 is transferred to the gears 18 to 21.
The vehicle is reversed and becomes the reverse position of R range. In the pulley ratio conversion unit 4, a sub-shaft 23 is arranged parallel to the main shaft 17, a main pulley 24 and a sub-pulley 25 are provided on both the shafts 17 and 23, respectively, and an endless belt is provided between the two pulleys 24 and 25. A drive belt 26 is wrapped around it. Both pulleys 24, 25
Both have stationary pulley halves 24b, 25b and movable pulley halves 24a, 25a, and hydraulic servo devices 27, 28 are attached to the movable pulley halves 24a, 25a, respectively, so that the pulley intervals can be adjusted. Configured variably. Then, hydraulic operation is performed to narrow the gap between one of the pulleys 24 and 25 and widen the gap between the other pulley, and changes the ratio of the winding diameter of the drive belt 26 to both pulleys 24 and 25 to continuously change the speed. It is configured to output the generated power to the subshaft 23. In the final reduction section 5, an output shaft 30 is connected to a subshaft 23 via an intermediate reduction gear 29, and a large diameter final gear 32 meshes with an output gear 31 of the output shaft 30.
The differential mechanism 33 of the final gear 32 transmits power to the left and right drive wheels via axles 34 and 35. Further, in the hydraulic control section 6, a hydraulic pump 37 is disposed adjacent to the main pulley 24. In addition, the pump drive shaft 36 directly connected to the engine crankshaft 7 is connected to the main shaft 1.
7 and the input shaft 10 to penetrate the hydraulic pump 3.
7 and is configured to constantly generate oil pressure during engine operation. On the other hand, it has a hydraulic control circuit 38 to which pump hydraulic pressure of the hydraulic pump 37 is supplied, and this hydraulic control circuit 38 and both hydraulic servo devices 27, 2
8 are connected through oil passages 39 and 40, respectively. The hydraulic control circuit 38 will be explained in FIG. The hydraulic servo device 27 is a movable half body 24a.
serves as a piston and fits into the cylinder 27a, and a servo chamber 27b is provided behind the movable half 24a. Also in the hydraulic servo device 28, the movable half body 25a is fitted into the cylinder 28a, and a servo chamber 28b is provided behind the movable half body 25a. Here, the pressure receiving area of the main pulley movable half 24a is set larger than that of the auxiliary pulley movable half 25a, so that the hydraulic pressure of the main pulley 24 can be used to arbitrarily control the speed change. The suction side of the hydraulic pump 37 communicates with an oil reservoir 42 via a filter 41, and the line pressure oil passage 39 on the discharge side of the hydraulic pump 37 communicates with a pressure regulating valve 43, and the oil passage 39 branches from this oil passage 39. A passage 40 communicates with the sub-pulley servo chamber 26b. The oil passage 39 further includes a speed change control valve 44 and is connected to the main pulley servo chamber 27b.
communicate with. The main pulley 24 also has a rotation sensor 4.
9, which generates a pitot pressure according to the main pulley rotation speed when the clutch is disengaged, and generates a pitot pressure according to the engine rotation speed when the clutch is connected. In the speed change control valve 44, a spool 46 is movably inserted into a valve body 45, and a throttle cam 5 is mounted on one side of the spool 46 to lift according to the throttle opening.
1 is an actuating member 4 that moves in response to the lift.
8. Connected via a spring 47. Also, the port 4 on the opposite side of the spring 47 of the spool 46
Pitot pressure is introduced and acts on 5a through the oil passage 50. Port 45b of valve body 45 is connected to spool 4
The lands 46a and 46b of No. 6 selectively communicate with one of the line pressure supply port 45c and the drain port 45d, and the port 45b communicates with the servo chamber 27b through the oil passage 39a of the oil passage 39, and the port 45c communicates with the pressure regulating valve 43 through the oil passage 39b, and the drain port 45d communicates with the oil passage 52.
This communicates with the oil sump 42. In this way, the speed change control valve 44 operates so that a pitot pressure corresponding to the engine speed and a spring force corresponding to the throttle opening act against each other on the spool 46, so that the two are always balanced. That is, when the spring force is greater, the ports 45b and 45d are communicated to drain the main pulley servo chamber 27b and the main pulley servo oil pressure is reduced, and when the pitot pressure overcomes the spring force, the ports 45b and 45c are communicated. Then, oil is supplied to the main pulley servo chamber 27b using line pressure to increase the main pulley servo oil pressure. Then, the shift is controlled to upshift or downshift by changing the main pulley servo oil pressure. Next, the spool 54 of the pressure regulating valve 43 is movably inserted into the valve body 53. Further, a feedback link 56 is provided on the main pulley movable half body 24a.
It is attached to detect the actual gear ratio according to the movement of the half body 24a. A feedback link 56 is attached to one side of the spool 54, and a feedback link 56 is attached to one side of the spool 54.
7. Connected via a spring 55, peat pressure is introduced into the port 53a of the spool 54 on the opposite side of the spring 55 through the oil passage 50, and line pressure is introduced into the port 53b through the oil passage 39c. act. The spool 54 communicates the port 53c and the oil drain side oil passage 52 through a notch in the land 54a to regulate the pressure. In this way, the spool 54 of the pressure regulating valve 43 has
The line pressure and pitot pressure act in the direction of increasing the amount of oil discharged through communication between ports 53c and 53d and lowering the line pressure, and the spring force according to the gear ratio decreases the amount of oil discharged and increasing the line pressure. It acts on As a result, at the maximum gear ratio, the line pressure is controlled to the maximum because the spring force is the largest, and from this state the line pressure is smoothly reduced as the spring force is gradually reduced as the gear shifts to high gear. Control the line pressure as follows. On the other hand, when the pump discharge pressure increases due to an increase in the engine speed, the drain amount is increased by the pitot pressure, and correction is made to maintain the line pressure control state according to the speed ratio. Line pressure prevents belt slip and always applies pulley pressing force in accordance with the transmitted torque. In such a configuration, the present invention provides that the oil passage 39a that communicates the transmission control valve 44 and the main pulley servo chamber 27b is connected to the oil passage 3 as the minimum gear ratio holding means.
A flow path switching valve 60 is provided in these oil passages 39a' and 39a'' and a bypass oil passage 65 that branches from oil passage 39b as a line pressure oil passage. The flow path switching valve 60 has a spool 62 on the valve body 61.
is inserted, a return spring 63 is biased on one side of the spool 62, and a solenoid 64 is provided on the other side of the spool 62. Further, the port 61a communicates with the oil passage 39a' on the main pulley side, and the port 61c
communicates with the oil passage 39a'' on the speed change control valve side, and connects to port 6.
1b communicates with an oil passage 65. and solenoid 64
Port 61a is connected to port 61 depending on whether or not the power is energized.
b or port 61c. The detection means includes an accelerator switch 66 that is turned on when the throttle is fully closed. Also, the vehicle speed is point P4
It turns on when the vehicle speed V2 corresponding to (for example, V2 = 15 km/h) corresponds to a predetermined vehicle speed V1 lower than this vehicle speed V2.
It has a vehicle speed switch 67 that turns off when the vehicle is turned off, and both switches 66 and 67 detect the driving state after the start of a downshift during deceleration with the throttle fully closed. Both switches 66 and 67 are connected to the solenoid 64 via an AND gate 68. Next, the operation of this embodiment will be explained. First, when the vehicle is stopped, the vehicle speed switch 67 is turned off, and when the vehicle is running with the accelerator depressed, the accelerator switch 66 is turned off. For this reason, the flow path switching valve 60
When the solenoid 64 is de-energized, the spring 63 moves the spool 62 to the right and communicates with the ports 61a and 61c. Therefore, the bypass oil passage 65 is shut off, and the speed change control valve 44 is closed to the oil passage 3.
9a', 39a'' communicate with the main pulley servo chamber 27b, and this speed change control valve 44 allows oil to be supplied and drained from the main pulley servo chamber 27b using line pressure to control speed change. The line pressure regulated in step 43 has already reached the sub-pulley servo chamber 28b.
It works by introducing it into. On the other hand, in the speed change control valve 44, the force of the spring 47 depending on the throttle opening is greater than the pitot pressure depending on the engine speed, so the spool 46 is moved to the right.
Port 45b communicates with drain port 45d to drain oil from main pulley servo chamber 27b. Therefore, the movable half 24a of the main pulley 24 is moved backward, and the drive belt 26 is wound deeply, resulting in a low speed stage with the maximum gear ratio. After starting to run at this maximum gear ratio, as the vehicle speed increases, the pitot pressure increases along with the engine speed.
moves to the left side and communicates the port 45b with the port 45c, thereby supplying oil to the main pulley servo chamber 27b at line pressure. Here, since the pressure-receiving area of the main pulley 24 is larger than that of the sub-pulley side, the drive belt 2
6 is pressed and moves to the main pulley side. In this way, the winding diameter of the drive belt 26 around the main pulley 24 gradually increases, and the drive belt 26 is upshifted to a high speed stage from P2 to P3 in FIG. At this time, in the pressure regulating valve 43, the force of the spring 55 is sequentially decreased by the feedback link 56 as the upshift occurs, and the line pressure is controlled to decrease from the highest state of the maximum gear ratio. On the other hand, during deceleration with the throttle fully closed, the spring force in the shift control valve 44 is at its minimum, but when the vehicle speed is high, the pitot pressure is also high to some extent, so the main pulley servo chamber 27b is in communication with the port 45b and port 45c. It becomes refueled. Therefore, the minimum gear ratio l2 shown in FIG. 4 is maintained. Then, the vehicle speed is the vehicle speed at downshift starting point P4
When the pressure drops to V2, the pitot pressure in the speed change control valve 44 becomes smaller than the minimum spring force. Therefore, communication between ports 45b and 45d operates to drain oil from main pulley servo chamber 27b. At this time, in addition to the access switch 66 already being turned on, the vehicle speed switch 67 is also turned on, and the output signal from the AND gate 68 causes the flow path switching valve 60 to be turned on.
The solenoid 64 of is energized. Therefore, the flow path switching valve 60 is switched to communicate the ports 61a and 61b, and the line pressure of the oil path 65 is supplied to the main pulley servo chamber 27b bypassing the speed change control valve 44, and the oiled state is maintained. . Therefore, regardless of the operation of the speed change control valve 44, the minimum speed ratio l2 is maintained as shown by the broken line in FIG. 4, and the vehicle speed is further reduced in a state where the engine brake is not effective. When a predetermined vehicle speed V1 is reached, the vehicle speed switch 67 is also turned off, so that the flow path switching valve 60 returns to its original state, and the oil paths 39a' and 39a'' communicate with each other, and the main pulley servo chamber 27b is controlled by the speed change control valve. Therefore, as shown in Fig. 4, a downshift starts at point P4' of vehicle speed V1, and from this point on, the vehicle speed further decreases and returns to a low gear while engine braking is applied during the downshift. The oil passage 65 is the oil passage 39 in
Of course, it may communicate with any location within b. Another embodiment of the present invention will be described with reference to FIG. In this embodiment, a solenoid 64 that operates under the same conditions as described above is directly provided on the opposite side of the spring 47 in the spool 46 of the speed change control valve 44 as a minimum speed ratio holding means. In the range of vehicle speeds V2 and V1 during deceleration, the spool 46 of the speed change control valve 44 is locked in the oiled state by the solenoid 64, thus maintaining the minimum speed ratio l2 as described above. Note that the area where the minimum gear ratio l2 is maintained depends on the vehicle speed.
Expanding below V1 or engine speed Ni and N1
It can also be set between. It goes without saying that the present invention can also be applied to clutches other than electromagnetic powder clutches.

【Effect of the invention】

As explained above, according to the present invention, the minimum gear ratio holding means is provided in the hydraulic system of the continuously variable transmission,
When the electrical signal from the detection means is input to the flow path switching valve of the minimum gear ratio holding means, the line pressure oil path is switched to communicate with the servo device of the main pulley, and the servo device of the main pulley is maintained in a lubricated state. By doing this, the minimum gear ratio is arbitrarily maintained regardless of the operation of the gear change control valve, so engine braking can be reduced during deceleration with the throttle fully closed, and discomfort and shock caused by large decelerations can be reduced. It disappears.
When the vehicle stops, it returns to the original maximum gear ratio, so
It does not affect driving performance and prevents the engine from stalling during sudden stops. If the minimum gear ratio holding means is configured such that a solenoid is provided in the gear change control valve and is forcibly moved to the refueling position by an electric signal, the structure is simplified.

[Brief explanation of the drawing]

Fig. 1 is a skeleton diagram showing an example of a continuously variable transmission to which the present invention is applied, Fig. 2 is a configuration diagram showing one embodiment of the device according to the present invention, and Fig. 3 is a main part showing another embodiment. FIG. 4 is a diagram of the transmission characteristics. 2...Continuously variable transmission, 17...Main shaft, 23...Subshaft, 24...Main pulley, 25...Sub-pulley, 26
... Drive belt, 27 ... Main pulley servo device, 28 ... Sub-pulley servo device, 43 ... Pressure adjustment valve, 44 ... Speed change control valve, 39 ... Oil supply and drainage oil path, 65 ... Line pressure oil path, 60...flow path switching valve, 64...solenoid, 66...accelerator switch, 67...vehicle speed switch.

Claims (1)

[Claims] 1. A main shaft on the engine side and a sub-shaft on the wheel side arranged parallel to the main shaft, each having a main pulley and a sub pulley with variable pulley intervals, and a drive belt wound between both pulleys. In a continuously variable transmission, the effective diameter of the pulley is changed by the hydraulic pressure supplied to each servo device of the main and sub pulleys, and the pulley ratio between the main and sub shafts is controlled steplessly. In the hydraulic control circuit that communicates with the servo device of the pulley, there is a pressure regulating valve that controls the line pressure supplied to the auxiliary pulley servo device according to the gear ratio, and a pressure regulating valve that controls the spring force and engine speed according to the throttle opening. a gear change control valve that changes the gear ratio by supplying and discharging line pressure to the main pulley servo device in accordance with the relationship with the corresponding pitot pressure, and an oil passage communicating between the gear change control valve and the main pulley servo device. A flow path switching valve is provided, which has an inlet side port and an outlet side port communicating with the oil passage, and a second port whose outlet side port bypasses the speed change control valve and communicates with the line pressure oil passage on the pressure regulating valve side. The invention further comprises a switching means for maintaining a minimum gear ratio by switching the flow path switching valve so that the second port communicates with the main pulley servo device in response to an electric signal from the detection means for detecting the state. Speed change control device for gear transmission.