JPH0526973B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a shift control device for a belt-type continuously variable transmission for a vehicle, and more particularly to a shift control device that provides an appropriate engine braking effect when switching to an L range for engine braking.

[Conventional technology]

Regarding speed change control of belt-type continuously variable transmissions for vehicles, there is a prior art technology described in, for example, Japanese Unexamined Patent Publication No. 157930/1983, in which line pressure is always applied to either the main pulley or the sub pulley with variable pulley groove width. introduced,
On the other hand, it is shown that the line pressure is drained and refueled and controlled by a speed change control valve that operates depending on the relationship between the engine speed and the amount of accelerator depression, thereby achieving continuously variable speed. By the way, in such a configuration, as in the case of an automatic transmission with a torque converter, when the vehicle is decelerating, the gear position is shifted to the high speed gear side, so that engine braking is not effective. Therefore, in addition to the continuously variable D range, which has limited limits, an L range for engine braking is added, and when switching to this L range, the speed change control valve is controlled by spring force or oil pressure to the pitot pressure according to the engine speed. It has been proposed to perform downshift control by forcibly discharging the pressure.

[Problem to be solved by the invention]

However, in the L range, the spring that works against the pitot pressure of the shift control valve is compressed by a spring or hydraulic actuator regardless of whether the accelerator is depressed, and the shift is controlled so that the engine speed is higher than a certain level. Because of this structure, the effectiveness of the engine brake changes depending on the engine speed before applying the engine brake. That is, as shown in FIG. 5, since the engine speed is also low at low vehicle speed V1, the engine speed changes significantly from n1 to n0, resulting in strong engine braking. On the other hand, since the engine speed is high at high vehicle speed V2, the engine speed changes only slightly from n2 to n0, resulting in the disadvantage that almost no engine braking effect can be expected. In view of these problems in the L range speed change control for engine braking, the present invention provides a speed change control device for a continuously variable transmission that can obtain an optimal engine braking effect over the entire range from low vehicle speeds to high vehicle speeds. The purpose is to

[Means to solve the problem]

For this purpose, the present invention has a main shaft connected to the engine side and a subshaft connected to the wheel side, which are arranged in parallel, and a main pulley and a sub pulley with variable pulley intervals are mounted on both shafts, and windings are wound between the two pulleys. In a continuously variable transmission, the effective diameter of the pulley is changed by the hydraulic pressure supplied to the servo device of both pulleys, and the pulley ratio between the main and counter shafts is controlled steplessly. The hydraulic circuit has a hydraulic circuit that connects to each servo device of the main and sub pulleys, and the hydraulic circuit uses line pressure from a hydraulic source to increase the line pressure in low speed gears where the pulley ratio is large depending on the relationship between the pulley ratio and the engine rotation speed. , a pressure regulating valve that regulates the line pressure to a low level when shifting to a high speed gear, and a supply/discharge control of the hydraulic pressure from the pressure regulating valve to the servo device on the main pulley side in relation to the throttle opening and engine speed. A low shift valve for controlling the discharge pressure of the secondary hydraulic pressure is provided in a secondary hydraulic oil passage provided in communication with the drain oil passage of the hydraulic circuit, and the low shift valve is connected to a predetermined position. A shift lever for switching the L range controls exhaust pressure in the operating range, and when the secondary hydraulic pressure is exhausted by the low shift valve, the movable member engages with the control member of the speed change control valve to control the main pulley side servo device. A first actuator for engine braking that operates hydraulic pressure toward the exhaust pressure side, and a second actuator that is connected to the first actuator and whose movable amount changes depending on the level of line pressure in the hydraulic circuit. The second actuator is configured to move more as the line pressure is higher and to restrict the amount of movement of the first actuator to a smaller range.

[Effect]

In the present invention employing such means, the continuously variable transmission is basically controlled to change speed according to the operation of the speed change control valve. When the shift lever is switched to the L range while driving, the low shift valve discharges the secondary hydraulic pressure leading to the first actuator for engine braking, causing the movable part of the first actuator to shift gears. It engages with the control member of the control valve and operates the speed change control valve to the side that exhausts the hydraulic pressure of the main pulley side servo device regardless of the throttle opening, thereby forcibly downshifting the continuously variable transmission. Control. In this case, the operating amount of the first actuator for engine braking is regulated according to the operating amount of the second actuator, and the higher the line pressure, the greater the movement of the second actuator increases the operating amount of the first actuator. Regulate within a small range. As a result, when comparing the same gear position, at low vehicle speeds, the rotation speed of the main pulley is low and the line pressure regulated by the pressure regulating valve is high, so the operating amount of the first actuator is regulated to a small range and there is no The downshift control amount of the gear transmission decreases accordingly, but at high vehicle speeds the main pulley rotation speed is high and the line pressure regulated by the pressure regulating valve is low, so the first actuator for engine braking The amount of operation increases, and the amount of downshift control of the continuously variable transmission also increases accordingly. Therefore, the engine braking action is prevented from becoming too effective at low vehicle speeds, and sufficient engine braking action is obtained at high vehicle speeds, and optimal engine braking action is obtained over the entire range from low vehicle speeds to high vehicle speeds.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, a continuously variable transmission with an electromagnetic powder clutch will be explained as an example of a continuously variable transmission to which the present invention is applied in FIG. Broadly speaking, the gear transmission 2 includes a forward/reverse switching section 3, a pulley ratio converting section 4, 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 to the transmission input shaft 10 by a spline in the direction of rotation. The drive member 9 and the driven member 11 are loosely fitted through a gap 12, so that electromagnetic powder from a powder chamber 13 is collected in the gap 12. In addition, a slip ring 15 is connected to the drive member 9 via a holder 14.
is installed, and a brush 16 for power supply is in sliding contact with the slip ring 15 to cause a clutch current to flow through the coil 8. When a clutch current is applied to the coil 8 in this way, electromagnetic particles are combined and accumulated in a chain in the gap 12 between the drive member 9 and the driven member 11 due to the lines of magnetic force generated between the drive member 9 and the driven member 11. On the other hand, the driven member 11 slides and becomes integrally connected. On the other hand, when the clutch current is cut off, the coupling force between the drive member 9 and the driven member 11 due to the electromagnetic powder disappears, resulting in the clutch being in a disengaged state. In this case, the clutch current supply and cut are as follows:
If the switching unit 3 of the continuously variable transmission 2 is operated in conjunction with the shift lever etc., it will be possible to switch from the P (parking) or N (neutral) range to the D (drive) or R (reverse) range. At the time of switching, clutch 1 is automatically disengaged, eliminating the need for clutch pedal operation. Next, in the continuously variable transmission 2, the switching section 3 is provided between the input shaft 10 from the clutch 1 and the main shaft 17 disposed coaxially therewith, and is connected to a reverse drive drive integrally connected to the input shaft 10. gear 18
and a reverse driven gear 19 rotatably fitted to the main shaft 17 are meshed together via a counter gear 20 and an idler gear 21, and a switching clutch 22 is provided between the main shaft 17 and the gears 18 and 19. When the switching clutch 22 is engaged from the neutral position of the P or N range to the gear 18 side, the main shaft 17 is directly connected to the input shaft 10, resulting in the forward state of the D or L range, and the switching clutch 22 is moved to the gear 19 side.
When engaged, the power of the input shaft 10 is decelerated and reversed by the gears 18 to 21, resulting in a reverse traveling state in the 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 shafts 17 and 23, respectively, and the main pulley 24 and the sub-pulley 25 are connected to each other. An endless drive belt 26 is wound between them. The main pulley 24 and the sub pulley 25 are both divided into two parts, with movable pulley halves 24a and 2
Hydraulic servo devices 27 and 28 are attached to 5a to make the pulley groove width variable. In this case, the main pulley 24 brings the movable pulley half 24a closer to the fixed pulley half 24b to gradually narrow the pulley groove width, and conversely, the sub pulley 25 moves the movable pulley half 24a closer to the fixed pulley half 24b. By moving the pulley halves 25a away from each other and gradually widening the pulley groove width, the drive belt 26 for the main pulley 24 and the sub pulley 25 is
By changing the ratio of the winding diameters, continuously variable speed output power is output to the subshaft 23. The final reduction section 5 has an intermediate reduction gear 29 on the subshaft 23.
The output gear 31 of the output shaft 30 connected through the gear meshes with a large-diameter final gear 32, and transmission is configured from the final gear 32 to the axles 34, 35 of the left and right drive wheels via a differential mechanism 33. . Further, the hydraulic control unit 6 has a pump drive shaft 36 on the main pulley 24 side, which passes through the main shaft 17 and the input shaft 10 and is directly connected to the engine crankshaft 7, as a hydraulic power source so as to constantly generate hydraulic pressure during engine operation. An oil pump 37 is provided. Then, this pump oil pressure is controlled by a hydraulic control circuit 38 based on the gear ratio (pulley ratio), the throttle opening according to the accelerator depression, the rotation speed of the main pulley 24 according to the engine rotation speed, etc. ,40
It is supplied to each hydraulic servo device 27, 28 on the main pulley 24 and sub pulley 25 side via the main pulley 24 and the sub pulley 25, and is configured to perform continuously variable speed control of the pulley ratio converter 4. To explain the speed change control system of the hydraulic control unit 6 in FIG. 2, in the hydraulic servo device 27 on the main pulley 24 side, the movable pulley half 24a serves as a piston and fits into the cylinder 27a, supplying the oil to the servo chamber 27b. In the hydraulic servo device 28 on the sub-pulley 25 side, the movable pulley half 25a fits into the cylinder 28a, and the servo chamber 28
In this case, the pulley half 24a has a larger line pressure receiving area than the pulley half 25a. And sub-pulley servo chamber 28
A line pressure oil passage 40 connected to b communicates with an oil reservoir 42 via an oil pump 37 and a filter 41,
A pressure regulating valve 43 and a speed change control valve 44 are provided in a line pressure oil passage 39 that branches from the oil pump discharge side of this line pressure oil passage 40 and communicates with the main pulley servo chamber 27b. The speed change control valve 44 includes a valve body 45, a spool 46, a spring 47 biased against one of the spools 46, and a control member 48 that changes the spring force.
Pitot pressure from a rotation sensor 49 provided on the main pulley 24 side and detecting its rotation speed (engine rotation speed) is introduced to the port 45a on the opposite side of the spring 47 of the spool 46 via an oil passage 50. A throttle cam 51 that rotates in accordance with the throttle opening is in contact with the control member 48. Also, the port 45b of the valve body 45 is connected to the spool 46.
The lands 46a and 46b 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 an oil passage 39a, which is a line pressure oil passage. The port 45c communicates with the pressure regulating valve 43 side through an oil passage 39b which is a line pressure oil passage, and the drain port 45d communicates with an oil passage 52a on the drain side.
This communicates with the oil sump 42 side. As a result, in the spool 46 of the speed change control valve 44, the pitot pressure corresponding to the main pulley rotation speed (engine rotation speed) of the port 45a and the spring force corresponding to the throttle opening degree caused by the rotation of the throttle cam 51 oppose each other. It operates based on the relationship between these two. That is, when the pitot pressure increases with the increase in the main pulley rotation speed (engine rotation speed), the ports 45b and 45c communicate with each other, supplying line pressure to the main pulley servo chamber 27b, and supplying line pressure to the high speed stage side where the pulley ratio is small. Continuously variable shifting is started, and the larger the pressing force of the spring 47 according to the throttle opening is, the more the shifting start point is shifted to the side where the main pulley rotational speed (engine rotational speed) is higher. The pressure regulating valve 43 includes a valve body 53, a spool 54, and a spring 55 biased against one of the spools 54.
The pitot pressure of the oil passage 50 and the line pressure of the oil passage 39c, which is a line pressure oil passage, are introduced to the ports 53a and 53b on the opposite side, respectively, and the spring 55 is guided to the movable pulley half 24a of the main pulley 24. A feedback sensor 56 is connected via a bush 57 to detect the actual gear ratio. Further, the line pressure oil passage 39c on the discharge side of the oil pump 37 is always connected to the speed change control valve 44 regardless of the position of the spool 54.
b, and the oil passage 52 on the drain side also communicates with the port 53d. The spool 54 moves slightly from side to side due to the pitot pressure and the pressing force of the spring 55, and communication between the line pressure port 53c and the drain side oil passage 52 is controlled by the notch in the land 54a of the spool 54. It is designed to regulate line pressure. As a result, pitot pressure or the like acts on the spool 54 of the pressure regulating valve 43 in the direction of draining the line pressure and decreasing it, and in response, the feedback sensor 56
The pressing force of the spring 55 according to the gear ratio acts in the direction of increasing the line pressure. As shown in Fig. 3, in the low speed gear where the pulley ratio is large and the transmitted torque is large, the force of the spring 55 is large, so the line pressure is set high, and as the gear shifts to the high speed gear where the pulley ratio is small, the line pressure is reduced. The pulley pressing force is controlled so as to decrease and always maintains a pulley pressing force that does not cause belt slip. In addition, in addition to the D range that performs speed change control over the entire range without restriction as a forward gear stage, in order to obtain an L range for engine braking in a predetermined operating range, a ball check valve 60 is provided on the upstream side of the ball check valve 60 provided in the middle of the drain oil passage 52. A secondary side oil pressure supply oil passage 61 branching from is configured to communicate with a low shift valve 63 and a first actuator 64 for engine braking via an orifice 62, and is further connected to the first actuator 64 to change engine braking characteristics. A second actuator 65 is provided, and a line pressure oil passage 66 branching from the line pressure oil passage 39c of the line pressure circuit, for example, is connected to this second actuator 65. The low shift valve 63 is constructed by inserting a valve element 69 having a drain hole 68 inside a valve body 67, and making contact with a shift cam 71 that rotates in response to the operation of a shift lever 70, and shifts to the L range. When the drain hole 68 is opened to the atmosphere by the recess 71a at the corresponding position, the secondary hydraulic pressure is exhausted. First actuator 64 for engine brake
The piston rod 73, which is a movable member inserted into the cylinder 72, is normally in an inoperative state with the spring 74 compressed by the secondary oil pressure, and the drain hole 68 of the low shift valve 63 is opened to the atmosphere. When the secondary hydraulic pressure is discharged, the movable member piston rod 73 moves in the direction of extension of the spring 74 due to the biasing force of the spring 74. During this movement, the shift control valve 44
The control member 48 is engaged with an arm 48a that is integral with the control member 48, and is configured to compress and bias a spring 47 provided in the speed change control valve 44 in accordance with the amount of movement of the arm 48a. Further, the second actuator 65 has a control piston rod 77 slidably inserted into the main body 75 communicating with the line pressure oil passage 66, on which the line pressure and the pressing force of the return spring 76 act oppositely. This control piston rod 7
The tip of the piston rod 7 can freely move in and out of the cylinder 72 of the first actuator 64 in order to regulate the amount of operation of the piston rod 73 of the first actuator 64. The movable amount of the second actuator 65 configured as described above changes depending on the level of the line pressure, and the higher the line pressure, the more the control piston rod 77 penetrates into the cylinder 72 of the first actuator 64. The amount of operation of the piston rod 73 of the first actuator 64 is regulated within a small range. Next, the operation of one embodiment configured as described above will be explained. First, when the shift lever 70 is shifted to the D range while driving forward, the valve body 69 of the low shift valve 63
is pushed by the shift cam 71 and the drain hole 68 is closed, so that the secondary hydraulic pressure communicated with the drain oil passage 52 of the hydraulic circuit is supplied to the cylinder 72 of the first actuator 64 for engine brake. As a result, the piston rod 73 (movable part) of the first actuator 64 protrudes out of the cylinder 72 to the maximum extent and enters a non-operating state in which it does not engage with the control arm 48a of the speed change control valve 44. Therefore, the line pressure regulated by the pressure regulating valve 43 is always introduced into the sub-pulley servo chamber 28b, and the pitot pressure according to the main pulley rotation speed (engine rotation speed) and the spring force according to the throttle opening degree are combined. In this regard, the regulated line pressure is supplied to and drained from the main pulley servo chamber 27b by the speed change control valve 44, thereby changing the belt winding diameters of the main pulley 24 and the sub pulley 25. As a result, the continuously variable transmission is continuously variable in the entire range between the low speed stage with the maximum pulley ratio shown by the curve 11 in FIG. 4 and the high speed stage with the minimum pulley ratio shown by the curve 12 in FIG. On the other hand, when the shift lever 70 is shifted to the L range, the end of the valve body 69 of the low shift valve 63 enters the recess 71a of the shift cam 71 and opens the drain hole 68, thereby connecting the low shift valve 63 to the first actuator 64 for engine braking. The supplied secondary hydraulic pressure is exhausted. Therefore, in the first actuator 64, the piston rod 73 is moved by the biasing force of the spring 74, and the end engages with the arm 48a that is integral with the control member 48 of the speed change control valve 44, and the first actuator 64 moves according to the amount of movement. The control member 48 is connected to the throttle cam 51.
The spring 47 is pushed in the direction in which the spring 47 is biased, regardless of this. Here, in a low-speed vehicle with a vehicle speed of V1 at a relatively high gear of curve 13 shown in FIG. 4, the engine speed is low, so the line pressure regulated by the pressure regulating valve 43 is correspondingly high. It is becoming. Therefore, the main body 7 of the second actuator 65
5, high line pressure is introduced through the line pressure oil passage 66, and the control piston rod 77 plunges into the cylinder 72 of the first actuator 64 to restrict the amount of movement of the piston rod 73 to a small range. Therefore, in the speed change control valve 44, since the pushing stroke of the control member 48 is small, the increase in the force of the spring 47 is small, and the land 46b of the spool 46 only slightly opens the drain port 45d, so that the main pulley side servo chamber 27b is The downshift amount of the continuously variable transmission due to line pressure being drained is also relatively small, and the engine speed is reduced from n1 to
It only increases to n'0, and as a result, a moderate engine braking effect can be obtained. On the other hand, at a high vehicle speed of V2 in the high gear position of curve 12 shown in FIG. 4, the engine speed is high, so the line pressure regulated by the pressure regulating valve 43 is correspondingly low. It's summery. Therefore, the main body 7 of the second actuator 65
5, a low line pressure is introduced through the line pressure oil passage 66, and the amount by which the control piston rod 77 protrudes into the cylinder 72 of the first actuator 64 becomes smaller, reducing the amount of movement of the piston rod 73 of the first actuator 64. becomes larger. Therefore, in the speed change control valve 44, the pushing stroke of the control member 48 becomes large, and the spring 47
The land 46b of the spool 46 widens the drain port 45d.
Therefore, as the line pressure is drained from the main pulley servo chamber 27b, the amount of downshift of the continuously variable transmission increases accordingly, and the engine speed increases from n2 to n″0, thereby achieving appropriate engine braking. Note that the line pressure acting on the control piston rod 77 of the second actuator 65 for changing engine braking characteristics is sufficiently high with respect to the force of the spring 74 of the first actuator 64 for engine braking. 73, there is no risk that the control piston rod 77 will move in the opposite direction, resulting in poor positioning of the piston rod 73.

【Effect of the invention】

As explained above, according to the present invention, when the shift lever is switched to the L range, the low shift valve displaces the secondary hydraulic pressure supplied to the first actuator for engine braking in conjunction with this, and the low shift valve discharges the secondary hydraulic pressure to be supplied to the first actuator for engine braking. The movable part engages with the control member of the speed change control valve regardless of the throttle opening and operates to forcibly downshift the continuously variable transmission, and in this case, the operating amount of the first actuator is is regulated by a second actuator whose movable amount changes depending on the level of line pressure, and the higher the line pressure is, the more the second actuator moves, thereby regulating the movable amount of the first actuator to a smaller range. This prevents the engine braking action from becoming too effective at low vehicle speeds, and provides sufficient engine braking action at high vehicle speeds.
Optimal engine braking action can be obtained over the entire range from low to high vehicle speeds.

[Brief explanation of drawings]

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 hydraulic circuit diagram showing an embodiment of the present invention, and Fig. 3 is a line pressure characteristic diagram in one embodiment. , FIG. 4 is an engine brake characteristic diagram in one embodiment, and FIG. 5 is an engine brake characteristic diagram in a conventional example. 2... Continuously variable transmission, 6... Hydraulic control section, 24...
...Main pulley, 25...Sub-pulley, 39, 39a,
39b, 39c, 40, 66... Line pressure oil path, 43... Pressure adjustment valve, 44... Speed change control valve,
48...Control member, 52...Oil passage, 61...Secondary side oil pressure supply passage, 63...Low shift valve, 64...
...First actuator for engine brake, 65
...Second actuator for engine brake.

Claims (1)

[Claims] 1. A main shaft connected to the engine side and a sub-shaft connected to the wheel side are arranged in parallel, and a main pulley and a sub-pulley with variable pulley spacing are mounted on these two shafts, and a winding is carried between the two pulleys. In a continuously variable transmission, the effective diameter of the pulley is changed by the hydraulic pressure supplied to the servo device of both pulleys, and the pulley ratio between the main and counter shafts is controlled steplessly. It has a hydraulic circuit that communicates with each servo device of the main and sub pulleys, and the hydraulic circuit uses line pressure from a hydraulic source to increase the line pressure in low speed gears where the pulley ratio is large, depending on the relationship between the pulley ratio and the engine rotation speed. A pressure regulating valve regulates the line pressure to a low level when shifting to a high speed gear, and the hydraulic pressure from the pressure regulating valve is controlled to be supplied to and discharged from the servo device on the main pulley side in relation to the throttle opening and engine speed. A shift control valve is provided, and a low shift valve is provided in a secondary hydraulic oil passage provided in communication with the drain oil passage of the hydraulic circuit for controlling the discharge pressure of the secondary hydraulic pressure, and the low shift valve is operated in a predetermined manner. When the secondary oil pressure is exhausted by the low shift valve, the movable member engages with the control member of the speed change control valve to operate the main pulley side servo device. A first actuator for engine braking that operates hydraulic pressure toward the exhaust pressure side, and a second actuator that is provided in conjunction with the first actuator and whose movable amount changes depending on the level of line pressure in the hydraulic circuit, Second
1. A speed change control device for a continuously variable transmission, characterized in that the actuator is configured to move more as the line pressure is higher, and to restrict the amount of movement of the first actuator to a smaller range.