JPH0737822B2 - Shift control device for continuously variable transmission - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a shift control device for a continuously variable transmission mainly used for vehicles.

[Prior art]

Regarding the shift control device of the continuously variable transmission as described above, there is the prior art described in Japanese Patent Application Laid-Open No. 60-159455, which was previously proposed by the applicant of the present application. This is intended for a belt-type continuously variable transmission that continuously changes the pulley ratio by hydraulic pressure, and has a hydraulic control system provided with a shift control valve for switching between supplying and discharging hydraulic oil. The shift control valve is formed with a pitot pressure chamber that receives pitot pressure oil as a control signal, and the spool uses a spring force as the pitot pressure oil enters according to the number of revolutions on the primary pulley side of the transmission. By moving against, the gear ratio is gradually reduced.

[Problems to be Solved by the Invention]

By the way, in this prior art, since the pitot pressure oil directly flows into and out of the pitot pressure chamber of the shift control valve,
Hunting was likely to occur in the spring-biased spool due to minute fluctuations in pitot pressure. In particular, in the large shift region indicated by the symbol A in the graph of FIG. 3, this tendency is large because the Pitot pressure itself is relatively low and the amount of change in the Pitot pressure with respect to the change in the rotational speed of the primary pulley is small. Therefore, there is a disadvantage that hysteresis occurs in the gear shift control and the gear ratio changes periodically, causing unpleasant vibration in the front and rear directions of the vehicle body. Therefore, it is an object of the present invention to prevent uncomfortable front-rear vibrations and abnormal fluctuations in hydraulic pressure that occur in the vehicle body by controlling the gear ratio in a stable state.

[Means for solving problems]

To this end, the present invention provides a hydraulic control system of a continuously variable transmission with a shift control valve having a pitot pressure chamber that receives pitot pressure oil corresponding to the rotation speed of the transmission input shaft as a control signal. In a shift control device for a continuously variable transmission that shifts the continuously variable transmission according to the spool operation of the valve, only the inflow of pitot pressure oil in the pitot pressure chamber is allowed in the pitot pressure oil passage of the shift control valve. The gist is that a check valve and an orifice arranged in parallel with it are provided.

[Action]

By such means, the pitot pressure oil immediately flows into the pitot pressure chamber of the shift control valve through the check valve, but the outflow from the pitot pressure oil is gently performed by passing through the orifice. Therefore, a damping effect is obtained in the operation of the spool, and the hysteresis phenomenon of the gear ratio control is eliminated by preventing spool hunting, and the gear ratio is controlled in a stable state.

【Example】

An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 2 shows a transmission system of a vehicle in which a continuously variable transmission to which the present invention is applied is incorporated. Reference numeral 1 denotes an electromagnetic powder clutch and 2 denotes a continuously variable transmission. The continuously variable transmission 2 is composed of a forward / backward switching unit 3, a pulley ratio conversion unit 4, a final reduction unit 5, and a hydraulic control unit 6 in order from the input side. In the electromagnetic powder clutch 1, a drive member 9 having a coil 8 therein is integrally connected to a crank shaft 7 from the engine, while a driven member 11 is integrally spline-connected in a rotational direction to a transmission input shaft 10. These drives and driven members 9 and 11 are loosely fitted through the gap 12 to collect electromagnetic powder from the powder chamber 13 in the gap 12. Further, a sleep ring 15 is installed on the drive member 9 via a holder 14, and a brush 16 for power supply is slidably brought into contact with the slip ring 15 so that a clutch current flows through the coil 8. In this way, when a clutch current is applied to the coil 8, the magnetic powder generated between the drive and the driven members 9 and 11 causes electromagnetic particles to be combined in a chain shape in the gap 12 between the drive members and the driven members 9 and 11 to be integrated, and the coupling force thereby causes the drive member 9 to join. Against driven member
The 11 slides into a state of being integrally connected and connected. On the other hand, when the clutch current is cut off, the coupling force between the drive and the driven members 9 and 11 due to the electromagnetic powder disappears and the clutch is disengaged. If the clutch current is supplied and cut in this case in conjunction with the operation of the switching unit 3 of the continuously variable transmission 2 with a shift lever or the like, P
(Parking) or N (Neutral) range to D
When switching to the (drive), L (low) or R (reverse) range, the clutch 1 is automatically engaged or disengaged, and the clutch pedal operation becomes unnecessary. Next, in the continuously variable transmission 2, the forward / reverse switching unit 3 is provided between the input shaft 10 from the clutch 1 and the main shaft 17 of the continuously variable transmission 2 coaxially arranged with the input shaft 10. A reverse drive gear 18 integrally connected to the shaft 10 and a reverse driven gear 19 rotatably fitted to the main shaft 17 are configured to mesh with each other via a counter gear 20 and an idler gear 21, and the main shaft 17 and gears 18, A switching clutch 22 is provided between the switches 19. When the switching clutch 22 is engaged with the gear 18 side from the neutral position of the P or N range, the input shaft 10 is rotated by the main shaft.
When 17 is directly connected to the forward state of the D or L range and the switching clutch 22 is engaged with the gear 19 side, the power of the input shaft 10 is decelerated and reversed by the gears 18 to 21 and transmitted to the main shaft 17,
The R range goes backward. In the pulley ratio conversion unit 4, the auxiliary shaft 23 is arranged in parallel with the main shaft 17, and the pulley pulley 2 is attached to both of these shafts 17, 23.
4, secondary pulley 25 is provided, and both pulleys 24, 25
An endless drive belt 26 is stretched between them. Each of the pulleys 24 and 25 is divided into two parts, and hydraulic servo devices 27 and 28 are attached to the movable pulley halves 24a and 25a to make the pulley interval variable. Then, in this case, the primary pulley 24 brings the movable pulley half 24a closer to the fixed pulley half 24b to sequentially reduce the pulley interval,
On the contrary, the secondary pulley 25 moves the movable pulley half 25a away from the fixed pulley half 25b and gradually widens the gap between the pulleys, thereby changing the winding diameter ratio of the pulleys 24, 25 of the drive belt 26. The power that has been shifted in steps is taken out to the auxiliary shaft 23. The final reduction unit 5 has a large-diameter final gear connected to an output gear 31 of an output shaft 30 connected to the auxiliary shaft 23 via an intermediate reduction gear 29.
32 meshes with each other, and is transmitted from the final gear 32 to the axles 34, 35 of the left and right drive wheels via the differential mechanism 33. Further, in the hydraulic control unit 6, a hydraulic pump 37 is provided on the primary pulley 24 side so that a hydraulic pressure is constantly generated during engine operation by a pump drive shaft 36 that penetrates through the main shaft 17 and the input shaft 10 and is directly connected to the engine crankshaft 7. Is provided. The pump hydraulic pressure is controlled by the shift control device 38 by the throttle opening degree and the engine speed according to the depression of the accelerator, and the hydraulic servo devices 27, 28 on the primary pulley side and the secondary pulley side via the oil passages 39, 40. Is supplied to
It is configured to perform continuously variable transmission control of the pulley ratio conversion unit 4. The shift control device 38 will be described with reference to FIG. 1. In the hydraulic servo device 27 on the primary pulley 24 side, the movable pulley half 24a is fitted to the cylinder 27a also as a piston so that it operates at the line pressure in the servo chamber 27b. Even in the hydraulic servo device 28 on the secondary pulley 25 side, the movable pulley half 25a fits into the cylinder 28a, and the servo chamber 28b
In this case, the pulley half 24a has a larger line pressure receiving area than the pulley half 25a. The oil passage 40 from the servo chamber 28b of the secondary pulley 25 communicates with the oil sump 42 via the hydraulic pump 37 and the filter 41, and branches from the hydraulic pump discharge side of the oil passage 40 to the servo chamber of the primary pulley 24. A pressure adjusting valve 43 and a shift control valve 44 are provided in an oil passage 39 communicating with 27b. The shift control valve 44 includes a valve body 45, a spool 46, a spring 47 biased to one side of the spool 46, and an actuating member 48 that changes the spring force, and is provided in a pitot pressure chamber 45e on the opposite side of the spring 47 of the spool 46. A pitot pressure corresponding to the engine speed from a rotation sensor 49 provided on the primary pulley 24 side is introduced to a communicating port 45a via an oil passage 50, and an actuating member 48 is provided with a throttle that rotates according to a throttle opening degree. The cam 51 is in contact. Also, the port 45b of the valve body 45 is
Depending on the position of the lands 46a and 46b of the spool 46, it selectively communicates with either the line pressure supply port 45c or the drain port 45d, and the port 45b is connected to the oil passage 39a of the oil passage 39.
Communicates with the servo chamber 27b, the port 45c communicates with the pressure adjusting valve 43 side through the oil passage 39b, and the drain port 45d communicates with the oil sump 42 side through the drain oil passage 52. As a result, in the spool 46 of the shift control valve 44, the pitot pressure corresponding to the engine speed of the pitot pressure chamber 45e and the force of the spring 47 corresponding to the throttle opening degree accompanying the rotation of the throttle cam 51 oppose each other. Functioning, and operate according to the relationship between them. That is, when the pitot pressure increases as the engine speed increases, the spool 46 moves to the left in the figure so that the ports 45b and 45c communicate with each other and the primary pulley
The line pressure is supplied to the servo chambers 27b of 24 to start shifting to the high speed side where the gear ratio becomes small. At this time, the greater the force of the spring 47 according to the throttle opening, the more the shift start point shifts to the higher engine speed. Next, the pressure regulating valve 43 comprises a valve body 53, a spool 54, and a spring 55 biased to one side of the spool 54. Ports 53a and 53b on the opposite side of the spring 55 of the spool 54 are connected to the pitot of the oil passage 50, respectively. Pressure, the line pressure of the oil passage 39c is introduced. A feedback sensor 56, which engages with the movable pulley half 24a of the primary pulley 24 and detects the actual pulley ratio, is connected to the spring 55 so as to increase the spring force as the pulley ratio increases. Furthermore, the pump side oil passage 39
c always indicates the speed change control valve 44 regardless of the position of the spool 54.
It communicates with the oil passage 39b. The spool 54 is balanced by the pitot pressure applied to the port 53a and the force of the spring 55, and the movement of the land 54a of the spool 54 controls the communication between the line pressure port 53c and the drain oil passage 52 side port 53d. By doing so, the exhaust pressure is controlled. A lubricating oil passage 61 is branched from the upstream side of the ball check valve 60 of the drain oil passage 52, and a line pressure reduction in the pressure adjusting valve 43 is made to the lubricating oil passage 61 via a throttle 62 and a discharge duty solenoid valve 63. Side port 64 is communicating. The solenoid valve 63 is controlled to reduce the exhaust pressure amount as the throttle opening becomes smaller by a means (not shown), so that a larger lubricating oil pressure is applied to the port 64 as the engine torque is smaller. There is. Here, according to the present invention, the pitot pressure chamber of the shift control valve 44 is
Check valve 71 in the pitot pressure oil passage 50 leading to 45e.
And an oil passage 75 having an orifice 72 in parallel therewith. This check valve 71 is composed of a biasing spring 73 and a ball valve 74 incorporated in the port 45a of the valve body 45 which communicates with the pitot pressure chamber 45e, and allows only the inflow of pressure oil to the pitot pressure chamber 45e and prevents the outflow. It is supposed to do. An oil passage 75 with an orifice 72 that directly connects the pitot pressure chamber 45e and the oil passage 50 is formed in the valve body 45 so as to bypass the check valve 71. Next, the operation of the shift control device for a continuously variable transmission having such a configuration will be described. Now, assuming that the forward / reverse switching unit 3 of the continuously variable transmission 2 is in the parking range or the neutral range, the primary pulley
The engine rotation is not transmitted to 24, so pitot pressure is not generated. Therefore, the shift control valve 44 is changed to the spool 46.
Receives only the spring force of the spring 47 to communicate the ports 45b and 45d with each other to drain the servo chamber 27b of the primary pulley 24. At this time, the hydraulic pump
Since 37 is already in operation, line pressure is being supplied to the servo chamber 28b of the secondary pulley 25, and the pulley ratio conversion unit 4 has the maximum belt winding radius of the secondary pulley 25, that is, the maximum gear ratio. It is at a low speed. Next, when the forward / reverse switching unit 3 is actuated as a drive range to perform an accelerator operation, a Pitot pressure is generated in accordance with the rotation of the primary pulley 24, and this pressure oil passes through the oil passage 50 and the check valve 71 to cause the shift control valve 44 to move. It flows into the pitot pressure chamber 45e. For this reason, when the pitot pressure rises as the engine speed increases, the spool 46 starts to move against the spring pressure of the spring 47, and eventually the ports 45b and 45c communicate with each other to connect the servo chamber of the primary pulley 24. Line pressure is supplied to 27b. This line pressure is the spring of the pressure adjusting valve 43.
55 is subjected to the action of the spring force applied by the feedback sensor 56, and the spool 54 is maintained at a high pressure because the spool 54 is not exerting pressure. Since such line pressure is supplied to the servo chambers 27b and 28b of the primary pulley 24 and the secondary pulley 25, the respective pulley halves 24a and 25a move and drive based on the difference in their pressure receiving areas. The half-wrap radius of the belt 26 is gradually changed to start the continuously variable shift to the high speed stage. The start point of the continuously variable shift is when the accelerator operation is gentle and the throttle opening is small, whereas in the case of rapid acceleration where the throttle opening is large, the shift control valve is set by the throttle cam 51.
By adding a spring force to the spring 47 of 44, it will be delayed by that amount. For example, in the case of gentle acceleration, the shift start point is near the engine speed of 1600 rpm, whereas in the case of sudden acceleration, the shift start point is near 4000 rpm. Therefore, in the case of gentle acceleration, the continuously variable transmission is started relatively early after starting, and the engine speed is kept substantially constant during that time.
During the period up to m, the vehicle accelerates strongly in a low speed roll state with a large gear ratio (see FIG. 3). When the accelerator pedal is released, the engine speed decreases and the pitot pressure decreases.
The spring pressure of the spring 47 causes the spool 46 to move to drain the line pressure on the primary pulley 24 side. When the spool 46 is moved, the pressure oil in the pitot pressure chamber 45e is transferred to the orifice 72.
By gradually flowing out through it, stable damping is achieved with a sufficient damping effect, and hunting due to excessive return of the spool 46 is prevented. The effect of preventing hunting is particularly remarkable in the region of a large gear ratio on the low speed side where the Pitot pressure itself is relatively low. By thus moving the spool without hunting, the gear ratio is stably and smoothly controlled.

【The invention's effect】

As described above, according to the present invention, hunting of the spool of the shift control valve is prevented and the gear ratio of the continuously variable transmission is controlled in a stable state. Unpleasant front-back vibration of the car body is prevented,
Also, abnormal fluctuations in the hydraulic pressure of the hydraulic system are prevented.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a shift control device for a continuously variable transmission according to an embodiment of the present invention, and FIG. 2 is a skeleton diagram of a vehicle transmission system incorporating the continuously variable transmission to which the present invention is applied. Third
The figure is a shift characteristic diagram of a continuously variable transmission. 1 ... Electromagnetic powder clutch, 2 ... Continuously variable transmission, 3 ... Forward / reverse switching section, 4 ... Pulley ratio conversion section, 5 ... Final reduction section,
6 ... hydraulic control part, 24 ... primary pulley, 25 ... secondary pulley, 27,28 ... hydraulic servo device, 38 ... transmission control device, 39,40 ... line pressure oil passage, 43 ... pressure adjustment Valve, 44 ... Shift control valve, 45 ... Valve body, 45e ... Pitot pressure chamber, 46 ... Spool, 50 ... Pitot pressure oil passage, 71 ... Check valve, 72 ... Orifice, 73 ... Power spring, 74
…… Ball valve.

Claims (1)

[Claims] 1. A hydraulic control system of a continuously variable transmission, comprising a shift control valve having a pitot pressure chamber for receiving pitot pressure oil according to a rotation speed of a transmission input shaft side as a control signal, and the spool of the shift control valve. In a shift control device for a continuously variable transmission that shifts a continuously variable transmission according to an operation, a check valve that allows only the inflow of pitot pressure oil into a pitot pressure chamber is provided in the pitot pressure oil passage of the above speed change control valve. A shift control device for a continuously variable transmission, characterized in that an orifice arranged in parallel with it is provided.