JPH05280633A - Speed change control device for continuously variable transmission - Google Patents

Abstract

PURPOSE:To improve an engine brake effect in the total region from a low speed to a high speed by constituting a device so as to discharge a control oil pressure in an oil path to an engine brake actuator by a low shift valve by switching a shift lever to an L range and an operating oil pressure in a main pulley side servo device in no relation to a throttle opening. CONSTITUTION:When a shift lever 70 is shifted to an L range, an end part of a valve unit 69 of a low shift valve 63 is placed in a recessed part 71a of a shift cam 71, to open a drain hole 68. Thus, a control oil pressure relating to an engine brake actuator 64 is discharged through a supply oil path 61. Accordingly, a piston rod 73 of the actuator 64 is moved by energizing force of a spring 74, to move an arm 48a to the right. Thus, a control part 48 of a speed change control valve 44 is moved to right, and a spool 46 is moved to right to open a little a drain port 45d in no relation to a throttle cam 51. In this way, a line pressure from a main pulley side servo chamber 27b is discharged not to an extent of shift down, to generate an engine brake.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for a belt type continuously variable transmission for a vehicle, and particularly to an L for engine braking.
The present invention relates to a shift control device that can obtain an appropriate engine braking effect when switching to a range.

[0002]

2. Description of the Related Art Conventionally, there is a prior art disclosed in, for example, Japanese Patent Laid-Open No. 54-157930 for the shift control of a belt type continuously variable transmission for a vehicle. It is shown that the line pressure is constantly introduced to the other side and the other side is continuously stepped by supplying and discharging the line pressure by the shift control valve that operates according to the relationship between the engine speed and the accelerator depression amount.

By the way, in such a structure, as in the case of the automatic transmission with a torque converter, since the shift position is on the high speed stage side during deceleration of the vehicle, the effect of engine braking is poor. Therefore, in addition to the D range, which has no limit and continuously variable transmission, the L range, which is effective for engine braking, is added, and when the L range is switched to, the shift control valve is adjusted by spring force or hydraulic pressure according to the engine speed. It has been proposed to forcibly exhaust the pressure against the Pitot pressure to perform downshift control.

[0004]

However, in such an L range, the spring that works against the Pitot pressure of the speed change control valve is compressed by an actuator that is operated by a spring or hydraulic pressure regardless of the depression of the accelerator, and the engine speed is increased. Since the shift control is configured to be higher than a certain level, the effectiveness of the engine brake changes depending on the magnitude of the engine speed before the engine brake is activated. That is, as shown in FIG. 5, at low vehicle speed V1, the engine speed is also low, so the engine speed changes significantly from n1 to n0, and a strong engine brake is obtained. On the other hand, at high vehicle speed V2, the engine speed is high, so the engine speed only slightly changes from n2 to n0, and the engine braking effect can hardly be expected.

In view of the problem of the shift control of the L range for engine braking, the present invention provides a shift control device for a continuously variable transmission that can obtain an optimum engine braking effect in the entire range from low vehicle speed to high vehicle speed. The purpose is to do.

[0006]

To this end, according to the present invention, a main shaft connected to an engine side and a sub shaft connected to a wheel side are arranged in parallel, and a main pulley having variable pulley groove widths is provided on both shafts. And a sub-pulley and a drive belt wound between both pulleys, and the effective diameter of the pulley is changed by the hydraulic pressure supplied to the servo device of both pulleys to continuously change the gear ratio between the main and sub-axes. The continuously variable transmission to be controlled has a hydraulic circuit that communicates from each hydraulic source to each servo device of the main and sub-pulleys, and the hydraulic circuit changes the line pressure from the hydraulic source according to the relationship between the gear ratio and the engine speed. A low-speed stage having a large ratio increases the line pressure, and a higher engine speed lowers the line pressure, and a hydraulic pressure from the pressure control valve is used as a main pulley in relation to the throttle opening and the engine speed. Side servo device A control oil pressure supply oil passage communicating with the line pressure oil passage of the hydraulic circuit, a low shift valve for controlling the exhaust pressure of the control oil pressure of the supply oil passage, and a predetermined low shift valve. L range switching shift lever for controlling the exhaust pressure in the operating region, and when the control hydraulic pressure is exhausted by the low shift valve, the movable member engages with the control member of the speed change control valve to move the speed change control valve to the main pulley side. A first actuator for engine braking, which is operated to discharge the operating hydraulic pressure of the servo device, is provided so as to be linked to the first actuator, and the movable amount changes according to the level of the line pressure in the hydraulic circuit. And a second actuator that restricts the movable amount of the first actuator within a small range by moving the control hydraulic pressure higher than the line pressure. That the pressure reducing control valve, and a means to become configured communicating with the line pressure passage through an orifice to restrict the flow of control pressure to said first actuator and Roshifuto valve.

[0007]

In the present invention employing such means, the continuously variable transmission is basically gearshift-controlled according to the operation of the gearshift control valve. When the shift lever is switched to the L range while the vehicle is traveling, the low shift valve works in conjunction with this to discharge the control oil pressure of the oil supply passage leading to the first actuator for engine braking, thereby moving the first actuator. The member engages with the control member of the shift control valve to move the shift control valve to the side for discharging the hydraulic pressure of the servo device on the main pulley side regardless of the throttle opening, thereby forcibly driving the continuously variable transmission. Downshift control.

In this case, the operation amount of the first actuator for engine braking is regulated according to the operation amount of the second actuator, and the higher the line pressure, the larger the movement of the second actuator, so that the first actuator moves. Restrict the working amount to a small range.

As a result, when compared at the same gear stage, the engine speed is low at low vehicle speed and the line pressure regulated by the pressure regulating valve is high, so the operation amount of the first actuator is restricted to a small range, While the downshift control amount of the continuously variable transmission is correspondingly reduced, the engine speed is high and the line pressure regulated by the pressure regulating valve is low at high vehicle speeds. The operation amount increases, and the downshift control amount of the continuously variable transmission also increases accordingly.

Therefore, the excessive effect of the engine braking action at low vehicle speed is prevented, and the sufficient engine braking action is obtained at high vehicle speed, so that the optimum engine braking action can be obtained over the entire range from low vehicle speed to high vehicle speed.

Here, the control oil pressure supply oil passage has a hydraulic circuit through a pressure reducing adjustment valve for generating the control oil pressure from the line pressure and an orifice for restricting the flow rate of the control oil pressure to the first actuator and the low shift valve. Since it is configured to communicate with the line pressure oil passage, there is no risk of pressure drop or insufficient flow rate in the hydraulic circuit even when the shift lever is switched to the L range and the low shift valve is discharging control hydraulic pressure. ..

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. First, referring to FIG. 1, as an example of a continuously variable transmission to which the present invention is applied, a continuously variable transmission with an electromagnetic powder clutch will be described.
Is a continuously variable transmission, and the continuously variable transmission 2 is roughly composed of a forward / reverse switching unit 3, a pulley ratio conversion unit 4, a final reduction unit 5 and a hydraulic control unit 6.

In the electromagnetic powder clutch 1, a drive member 9 having a coil 8 built therein is integrally connected to a crankshaft 7 from the engine, while a driven member 11 is integrally splined in a rotational direction to a transmission input shaft 10. Combined,
The drive member 9 and the driven member 11 are loosely fitted through the gap 12, and the electromagnetic powder is accumulated in the gap 12 from the powder chamber 13. Further, a slip ring 15 is installed on the drive member 9 via a holder 14, and a brush 16 for power feeding is slidably contacted with the slip ring 15 so that a clutch current is passed through the coil 8.

When the clutch current is applied to the coil 8 in this manner, the magnetic powder generated between the drive member 9 and the driven member 11 causes the electromagnetic particles to be combined in a chain shape in the gap 12 between the members, and the magnetic powder is driven by the connecting force. The driven member 11 is slidably connected to the member 9 while being integrally connected.

On the other hand, when the clutch current is cut, the coupling force between the drive member 9 and the driven member 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, the P (parking) or N (neutral) range is set. When switching to the D (drive) or R (reverse) range, the clutch 1 is automatically connected and disconnected, and the clutch pedal operation becomes unnecessary.

Next, in the continuously variable transmission 2, the switching portion 3 is provided between the input shaft 10 from the clutch 1 and the main shaft 17 arranged coaxially therewith.
A reverse drive gear 18 integrally coupled to the main shaft 17 and a reverse driven gear 19 rotatably fitted to the main shaft 17 are meshed with each other through a counter gear 20 and an idler gear 21, and the main shaft 17 and the gears 18, 19 are A switching clutch 22 is provided between them. When the switching clutch 22 is engaged with the gear 18 side from the neutral position of the P or N range, the main shaft 17 is directly connected to the input shaft 10 and the forward state of the D or L range is established, and the switching clutch 22 is engaged with the gear 19 side. When they match, the power of the input shaft 10 is decelerated and reversed by the gear 18 or the gear 21, and the R range is in the reverse drive state.

In the pulley ratio conversion section 4, a sub shaft 23 is arranged in parallel with the main shaft 17, a main pulley 24 and a sub pulley 25 are provided on both the shafts 17 and 23, respectively, and the main pulley 24 and the sub pulley 24 are provided. An endless drive belt 26 is wound around the belt 25.

The main pulley 24 and the sub-pulley 25 are both divided into two parts, and the movable pulley halves 24a, 25 are formed.
Hydraulic servo devices 27 and 28 are attached to a to make the pulley groove width variable. In this case, the main pulley 24 is moved toward the movable pulley half 24b with respect to the fixed pulley half 24b.
a is brought closer to reduce the pulley groove width, and the auxiliary pulley 25
On the contrary, the movable pulley half 25a is moved away from the fixed pulley half 25b, and the pulley groove width is gradually increased. As a result, the drive belt 26 for the main pulley 24 and the auxiliary pulley 25 is moved.
The power of stepless speed change by changing the winding diameter ratio of the auxiliary shaft 23
It is designed to be taken out.

In the final reduction gear unit 5, an output gear 31 of an output shaft 30 connected to the auxiliary shaft 23 via an intermediate reduction gear 29 meshes with a final gear 32 having a large diameter. Left and right drive wheel axle 3 via
It is configured to transmit to 4,35.

Further, the hydraulic control unit 6 is provided on the main pulley 24 side.
An oil pump 37 as a hydraulic pressure source is provided so as to constantly generate hydraulic pressure during engine operation by a pump drive shaft 36 that penetrates the main shaft 17 and the input shaft 10 and is directly connected to the engine crankshaft 7. The pump hydraulic pressure is controlled by the hydraulic control circuit 38 by the gear ratio (pulley ratio), the throttle opening degree according to the depression of the accelerator, the rotational speed of the main pulley 24 according to the engine rotational speed, etc.
It is supplied to the respective hydraulic servo devices 27 and 28 on the main pulley 24 and the auxiliary pulley 25 side via 9, 40, and the pulley ratio conversion unit 4
Is configured to perform the continuously variable shift control.

Referring to FIG. 2, the shift control system of the hydraulic control unit 6 will be described. The hydraulic servo device 2 on the main pulley 24 side.
7, the movable pulley half 24a is fitted into the cylinder 27a also as the piston, and is operated by the working hydraulic pressure (regulated line pressure) supplied to the servo chamber 27b. Also in the hydraulic servo device 28, the movable pulley half body 25a is fitted in the cylinder 28a and operated by the regulated line pressure supplied to the servo chamber 28b. In this case, the pulley half body 24a The line pressure receiving area is larger than that of the pulley half 25a. The line pressure oil passage 40 connected to the sub-pulley servo chamber 28b communicates with the oil sump 42 via the oil pump 37 and the filter 41, and branches from the oil pump discharge side of the line pressure oil passage 40 to the main pulley servo chamber. 27b
A pressure adjusting valve 43 and a shift control valve 44 are provided in a line pressure oil passage 39 communicating with the.

The speed change control valve 44 comprises a valve body 45, a spool 46, a spring 47 biased to one side of the spool 46, and a control member 48 for changing the spring force. The port of the spool 46 on the opposite side of the spring 47. Four
The pitot pressure from a rotation sensor 49, which is provided on the main pulley 24 side and detects the rotation speed (engine speed) of the main pulley 5a, is guided through the oil passage 50 to the control member 48 according to the throttle opening. The rotating throttle cam 51 is in contact.

The port 45b of the valve body 45 is selectively connected to one of the line pressure supply port 45c and the drain port 45d by the lands 46a and 46b of the spool 46, and the port 45b is connected to the line pressure. Of the oil passage 39a, which is the oil passage of the above, communicates with the servo chamber 27b, the port 45c is communicated with the side of the pressure adjusting valve 43 through the oil passage 39b, which is the oil passage of the line pressure, and the drain port 45d is connected through the drain side oil passage 52a. It communicates with the oil sump 42 side.

As a result, the spool 4 of the shift control valve 44 is
6, 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 accompanying the rotation of the throttle cam 51 act in opposition to each other. Works by relationship. That is, when the Pitot pressure rises as the main pulley rotation speed (engine rotation speed) rises, the ports 45b and 45c communicate with each other to supply a line pressure to the main pulley servo chamber 27b to the high speed stage side where the pulley ratio is small. The continuously variable transmission is started, and the larger the pressing force of the spring 47 according to the throttle opening is, the more the shift starting point is shifted to the side where the main pulley rotation speed (engine rotation speed) is higher.

The pressure adjusting valve 43 comprises a valve body 53, a spool 54, and a spring 55 biased to one side of the spool 54. The oil passages are provided in the ports 53a and 53b of the spool 54 on the side opposite to the spring 55, respectively. The pitot pressure of 50 and the line pressure of the oil passage 39c, which is an oil passage of the line pressure, are introduced, and the spring 55 is engaged with the movable pulley half 24a of the main pulley 24 to detect the actual gear ratio. 56 are connected via a bush 57.

The line pressure oil passage 39c on the discharge side of the oil pump 37 is always connected to the line pressure oil passage 39b which communicates with the speed change control valve 44 regardless of the position of the spool 54, and the oil passage 52 on the drain side is also connected. It communicates with the port 53d. The spool 54 is slightly moved to the left and right by the Pitot pressure and the pressing force of the spring 55.
Due to the notch in the land 54a, the line pressure port 53
The line pressure is adjusted by controlling the communication between c and the drain side oil passage 52.

As a result, the spool 5 of the pressure regulating valve 43
4, the pitot pressure or the like acts in the direction in which the line pressure is drained and reduced, whereas the pressing force of the spring 55 according to the gear ratio by the feedback sensor 56 acts in the direction in which the line pressure is increased. As shown in FIG. 3, in the low speed stage where the pulley ratio is large and the transmission torque is large, the spring 5
Since the force of No. 5 is large, the line pressure is set high, and the line pressure is controlled so as to decrease with the shift to the high speed side where the pulley ratio is small, and the pulley pressing force that does not always cause belt slip is maintained.

Here, in order to obtain the L range for performing the shift control limited to the low speed stage, in addition to the D range for performing the shift control over the entire range without limitation as the forward shift stage, the discharge side of the oil pump 37 in the line pressure circuit is provided. A control oil pressure supply oil passage 61 communicating with the line pressure oil passage 102 via the orifice 101 and the pressure reducing adjustment valve 100 is provided, and the low shift valve 6 communicating with the supply oil passage 61 via the orifice 62.
3 and a first actuator 64 for engine braking
Is provided. And this first actuator 64
A second actuator 65 for changing the characteristics of the engine brake is attached to this, and a line pressure oil passage 66 branching from, for example, the line pressure oil passage 39c of the line pressure circuit is connected to this.

The orifice 101 is for restricting the flow rate of the control oil pressure to the first actuator 64 and the low shift valve 63 to the necessary minimum, and the pressure reducing adjustment valve 100 is controlled by the line pressure of the line pressure oil passage 102. It is for generating a low control oil pressure.

In the low shift valve 63, a valve body 69 having a drain hole 68 is inserted inside a valve body 67.
9 is brought into contact with a shift cam 71 which rotates according to the operation of the shift lever 70, and the control hydraulic pressure is discharged when the drain hole 68 is opened to the atmosphere by the recess 71a at a position corresponding to the L range. It has become.

In the first actuator 64 for engine braking, the piston rod 73, which is a movable member inserted in the cylinder 72, is normally in the inoperative state in which the spring 74 is compressed by the control hydraulic pressure, and the low shift valve is used. When the drain hole 68 of 63 is opened to the atmosphere and the control hydraulic pressure is discharged, the piston rod 73, which is a movable member, is moved in the extension direction of the spring 74 by the urging force of the spring 74. At times, it is configured to engage an arm 48a that is integral with the control member 48 of the shift control valve 44, and compress and bias a spring 47 provided in the shift control valve 44 according to the amount of movement thereof.

Further, in the second actuator 65, the control piston rod 77, in which the line pressure and the pressing force of the return spring 76 oppose each other, is slidable inside the main body 75 communicating with the oil passage 66 of the line pressure. The control piston rod 77 has a tip end that can move in and out of the cylinder 72 of the first actuator 64 in order to regulate the operation amount of the piston rod 73 of the first actuator 64. .. The second actuator 65 configured as described above has a movable amount that changes according to the level of the line pressure. The higher the line pressure, the larger the control piston rod 77 is within the cylinder 72 of the first actuator 64. The amount of operation of the piston rod 73 of the first actuator 64, which plunges in, is restricted to a small range.

Next, the operation of the embodiment thus constructed will be described. First, when the shift lever 70 is shifted to the D range during forward traveling, the valve body 69 of the low shift valve 63 is changed.
Is pushed by the shift cam 71 and the drain hole 68 is closed, so that the low pressure supplied from the line pressure oil passage 102 to the cylinder 72 of the first actuator 64 for engine braking through the orifice 101 and the pressure reducing adjustment valve 100. ,
A small amount of control hydraulic pressure is supplied through the supply oil passage 61.
As a result, the piston rod 7 of the first actuator 64 is
3 (movable member) projects to the outside of the cylinder 72 to the maximum extent, and is in a non-operating state in which it does not engage with the control arm 48a of the shift 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 according to the throttle opening degree. The line pressure adjusted to the main pulley servo chamber 27b by the speed change control valve 44 in relation to the force is supplied and drained, and the main pulley 24 and the sub pulley 2
Convert the belt winding diameter of 5. As a result, the continuously variable transmission is continuously variable in the entire range between the low speed stage having the maximum pulley ratio shown by the curve L1 in FIG. 4 and the high speed stage having the minimum pulley ratio shown by the curve L2.

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 projects into the concave portion 71a of the shift cam 71 and the drain hole 68 is opened, whereby the low shift valve 63 passes through the oil supply passage 61. The control hydraulic pressure supplied to the first actuator 64 for engine braking is discharged. Therefore, the first actuator 64 is connected to the spring 7
The piston rod 73 is moved by the urging force of No. 4 and the end portion of the arm 48a is integral with the control member 48 of the shift control valve 44.
The control member 48 is pushed in the biasing direction of the spring 47 irrespective of the throttle cam 51 according to the amount of movement.

At a low vehicle speed of V1 in the relatively high gear position of the curve L3 shown in FIG. 4, the engine speed is low, so the line pressure regulated by the pressure regulating valve 43 accordingly. It is expensive. Therefore, a high line pressure is introduced into the main body 75 of the second actuator 65 via the line pressure oil passage 66, and the control piston rod 77 largely protrudes into the cylinder 72 of the first actuator 64 and the piston rod 73 moves. Limit the amount of movement to a small range.

Therefore, in the shift control valve 44, the control member 48
Since the pushing stroke is small, the increase in the force of the spring 47 is small, the land 46b of the spool 46 only slightly opens the drain port 45d, and the line pressure is discharged from the main pulley side servo chamber 27b. The downshift amount of the transmission is also relatively small, and the engine speed only rises from N1 to No, which provides an appropriate engine braking action.

On the other hand, at a high vehicle speed of V2 in the high gear position of the curve L2 shown in FIG. 4, since the engine speed is high, the line pressure regulated by the pressure regulating valve 43 is accordingly low. It has become a thing. Therefore, a low line pressure is introduced into the main body 75 of the second actuator 65 via the line pressure oil passage 66, and the amount of the control piston rod 77 thrusting into the cylinder 72 of the first actuator 64 becomes small. The movable amount of the piston rod 73 of the 1-actuator 64 becomes larger.

Therefore, in the shift control valve 44, the control member 48
The pushing stroke of the spring 47 increases, and the pressure of the spring 47 increases.
b greatly opens the drain port 45d. Therefore, the downshift amount of the continuously variable transmission due to the line pressure being drained from the main pulley servo chamber 27b also increases accordingly, and the engine speed increases from N2 to No ', so that a more appropriate engine braking action is obtained. can get.

Since the line pressure acting on the control piston rod 77 of the second actuator 65 for changing the engine brake characteristic is sufficiently high with respect to the force of the spring 74 of the first actuator 64 for engine braking,
The control piston rod 7 is reversed by the piston rod 73.
There is no possibility that 7 will move and the piston rod 73 will be misaligned.

Further, as described above, the control oil pressure supply oil passage 6 is provided.
Reference numeral 1 denotes a line pressure circuit in a line pressure circuit via a pressure reducing control valve 100 that generates a control hydraulic pressure lower than the line pressure and an orifice 101 that regulates the flow rate of the control hydraulic pressure to the first actuator 64 and the low shift valve 63 to a necessary minimum. Since it is configured to communicate with the line pressure oil passage 102 on the discharge side of the oil pump 37, even when the shift lever 70 is switched to the L range and the low shift valve 63 is discharging the control hydraulic pressure, the pressure is reduced in the hydraulic circuit. There is no risk of insufficient flow rate. Therefore, the operation of the continuously variable transmission is always maintained normally including the time of switching to the L range.

[0042]

As described above, according to the present invention, when the shift lever is operated to switch to the L range, the low shift valve interlocks with this to drain the control hydraulic pressure supplied to the first actuator for engine braking, and The movable member of the 1-actuator engages with the control member of the shift control valve irrespective of the throttle opening to operate to forcibly downshift control the continuously variable transmission. In this case, the operation amount of the first actuator described above is regulated by the second actuator whose movable amount changes according to the level of the line pressure, and the higher the line pressure, the larger the second actuator moves and the first actuator moves.
Since the actuator movement is restricted to a small range, the engine braking action is prevented from being overly effective at low vehicle speeds with high line pressure, and sufficient engine braking action is obtained at high vehicle speeds with low line pressure. hand,
It is possible to obtain optimum engine braking action over the entire range from low vehicle speed to high vehicle speed.

Here, the control oil pressure supply oil passage is provided with a hydraulic circuit through a pressure reducing valve for generating the control oil pressure from the line pressure and an orifice for restricting the flow rate of the control oil pressure to the first actuator and the low shift valve. Since it is configured to communicate with the line pressure oil passage, there is no risk of pressure drop or insufficient flow rate in the hydraulic circuit even when the shift lever is switched to the L range and the low shift valve is discharging control hydraulic pressure. .. Therefore, the operation of the continuously variable transmission can be normally maintained including the time of switching to the L range.

[Brief description 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.

FIG. 3 is a line pressure characteristic diagram in one example.

FIG. 4 is an engine brake characteristic diagram in one embodiment.

FIG. 5 is an engine braking characteristic diagram in the case of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electromagnetic powder type clutch 2 Continuously variable transmission 3 Forward / reverse switching section 4 Pulley ratio conversion section 5 Final reduction section 6 Hydraulic control section 24 Main pulley 25 Sub pulley 39, 39a, 39b, 39c, 40, 66 102
Oil line 43 for line pressure 44 Pressure adjusting valve 44 Shift control valve 48 Control member 61 Supply oil passage 63 Low shift valve 64 First actuator 65 Second actuator 100 Pressure reducing adjusting valve 101 Orifice

Claims (1)

[Claims] 1. A main shaft connected to an engine side and a sub shaft connected to a wheel side are arranged in parallel with each other, and a main pulley and a sub pulley having variable pulley groove widths are wound around these shafts. In a continuously variable transmission that is equipped with a drive belt that changes the effective diameter of the pulleys by the hydraulic pressure supplied to the servo devices for both pulleys to continuously control the gear ratio between the main and auxiliary shafts, There is a hydraulic circuit that communicates with each servo device of the sub-pulley, and in the hydraulic circuit, the line pressure from the hydraulic source is higher in the lower speed stage where the gear ratio is larger in relation to the gear ratio and the engine speed. A pressure control valve that regulates the line pressure lower as the number of revolutions increases, and a shift control valve that controls the supply and discharge of the operating oil pressure from the pressure control valve to the servo device on the main pulley side in relation to the throttle opening and the engine number of revolutions. And with A control oil supply oil passage communicating with a line pressure oil passage of a hydraulic circuit, a low shift valve controlling exhaust pressure of the control oil pressure of the supply oil passage, and an L range switching for controlling exhaust pressure of the low shift valve in a predetermined operation region. When the control hydraulic pressure is discharged by the shift lever and the low shift valve, the movable member engages with the control member of the shift control valve to move the shift control valve to the side for discharging the hydraulic pressure of the main pulley side servo device. A first actuator for engine braking, which is provided so as to be linked to the first actuator, and the movable amount changes according to the level of the line pressure in the hydraulic circuit. A second actuator for restricting the movable amount of the control pressure to a small range, and the oil supply passage for the control oil pressure has a pressure reducing valve for generating the control oil pressure from the line pressure and the first actuator. And the shift control device for a continuously variable transmission characterized by comprising configured communicating with the line pressure passage through an orifice to restrict the flow of control oil pressure to Roshifuto valve.