JP2911930B2 - Control device for continuously variable transmission - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for controlling a speed ratio in a continuously variable transmission, and more particularly to a measure for improving the re-startability when the vehicle stops in a neutral state.

2. Description of the Related Art Conventionally, as a control device of a speed ratio of a continuously variable transmission, as disclosed in, for example, Japanese Utility Model Publication No. Sho 63-1079, a drive pulley and a driven pulley having a variable effective radius are used. A continuously variable transmission mechanism comprising a belt wound between both pulleys, and a forward / reverse switching mechanism, a speed ratio control valve is provided, and the speed ratio control valve applies hydraulic pressure to a hydraulic cylinder of a drive pulley. There has been known an apparatus in which the speed ratio is steplessly controlled by continuously adjusting the effective radius by supplying and discharging.

(Problems to be Solved by the Invention) In this conventional device, when the shift range is switched to the neutral range, the speed ratio of the continuously variable transmission mechanism is switched to the minimum. But,
When the gear ratio is minimized in the neutral state, there is no problem when the vehicle decelerates and stops in a normal state, but, for example, the rotation of the wheels is stopped in a short time by a sudden brake (panic brake) in the neutral state. Then, since the wheels, that is, the driven pulleys do not rotate thereafter, the speed ratio is not shifted to the increasing side, and the vehicle stops with the speed ratio kept small. For this reason, there is a problem that the starting drive force is insufficient at the time of restart, and starting becomes difficult.

The present invention has been made in view of the above points, and an object of the present invention is to change the speed change control at the time of neutral to quickly change the speed ratio to the increasing side when suddenly stopping in the neutral state, thereby improving the response. Another object is to facilitate restarting after a sudden stop.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, the gear ratio is switched to the increasing side when in neutral.

That is, as shown in FIG. 1, the solving means of the present invention comprises a driving and driven pulley 41, 42 comprising a variable pulley.
And a continuously variable transmission mechanism 4 including a belt 43 wound between the pulleys 41 and 42.
It is assumed that a continuously variable transmission in which a shift range including a low speed range, a neutral range, and a reverse range is set.

Then, neutral range detecting means 120 for detecting that the shift range has been selected to the neutral range.
Shift control means 121 which receives the output of the detection means 120 and controls the speed of the continuously variable transmission mechanism 4 so that when the neutral range is selected, the drive-side rotational speed NP is higher than the low-speed side line in the low-speed range. Are provided.

Here, in the invention of claim 2, it is assumed that a forward / reverse switching mechanism is connected to the input side of the continuously variable transmission mechanism of claim 1.

According to a third aspect of the present invention, when the neutral range is selected, the shift control means according to the first or second aspect provides a low-speed range of a low-speed range in which the target drive-side rotational speed is set in the shift map from the shift map. It is assumed that a map value larger than the side line is read out, and the shift control is performed based on the map value.

According to a fourth aspect of the present invention, the shift control means according to any one of the first to third aspects, when the neutral range is selected,
The target drive-side rotation speed is determined based on the shift map in the low-speed range, and feedback control is performed so that the actual drive-side rotation speed becomes the calculated target drive-side rotation speed.

According to a fifth aspect of the present invention, when the neutral range is selected, the shift control means according to any one of the first to third aspects includes a target drive side rotation based on a fully open line when the throttle opening is fully open from a shift map. The number is calculated, and feedback control is performed so that the actual driving-side rotation speed becomes the obtained target driving-side rotation speed.

Further, in the invention according to claim 6, the shift control means according to claim 1 changes the target drive-side rotation speed when the neutral range is selected, when the drive side of the continuously variable transmission mechanism is reversely driven from the wheel side in the neutral range. , And the feedback control is performed so that the actual drive-side rotation speed becomes the guaranteed rotation speed.

(Operation) According to the first to sixth aspects of the present invention, when the neutral range is selected from the shift ranges,
The selection is detected by the detecting means 120, and the detecting means 1
The transmission control means 121 receiving the output of 20 controls the drive-side rotational speed NP of the continuously variable transmission mechanism 4 to be higher than the low-rotation side line in the low-speed range, and the speed ratio of the continuously variable transmission mechanism 4 is reduced. The transmission is controlled to increase. For this reason, even if the vehicle suddenly stops in the neutral state, the gear ratio is quickly switched to the increasing side until the rotation of the wheels, that is, the driven side is stopped, and the starting drive force is reduced when the vehicle restarts thereafter. Can be secured, and the recurrence can be improved.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

FIG. 2 shows the overall structure of the hydraulic continuously variable transmission according to the first embodiment of the present invention. The transmission shown in the figure is basically a torque converter 2 connected to an output shaft 11 of an on-vehicle engine 1.
, A forward / reverse switching mechanism 3, a continuously variable transmission mechanism 4, a speed reduction mechanism 5, and a differential mechanism 6 (differential mechanism).

As shown in detail in FIG. 3, the torque converter 2 includes a pump cover 21 connected to an engine output shaft 11.
A pump impeller 22 fixed to one side of the pump cover 21 and rotating integrally with the engine output shaft 11, and rotatably provided inside the pump cover 21 so as to face the pump impeller 22. A turbine runner 23, a stator 24 interposed between the turbine runner 23 and the pump impeller 22 to increase the torque, and a turbine runner 23
And a turbine shaft 25 fixed to the shaft. The stator 24 includes a one-way clutch 26 and a cylindrical stator shaft 27.
Through the transmission case 7. A turbine shaft is provided between the turbine runner 23 and the pump cover 21.
Lock-up piston 28 slidably mounted on 25
A lock-up clutch 28 having a is provided,
The lock-up clutch 28 is engaged and released by introducing and discharging hydraulic pressure to a lock-up engagement chamber 29a and a lock-up release chamber 29b formed on both sides of the lock-up piston 28a.

The forward / reverse switching mechanism 3 includes a ring gear 35 spline-coupled to the turbine shaft 25 of the torque converter 2, pinions 32, 32,.
, And a sun gear 34 that is spline-coupled to a primary shaft 411 of the continuously variable transmission mechanism 4 described below and meshes with the pinion gear 32. A forward clutch 36 for connecting and disconnecting the ring gear 35 and the carrier 31 is disposed between the ring gear 35 and the carrier 31, and a retreat for selectively fixing the carrier 31 to the transmission case 7 between the carrier 31 and the transmission case 7. Brake 37 is provided. When the forward clutch 36 is engaged and the reverse brake 37 is released, the ring gear 35 and the carrier
And the rotation of the turbine shaft 25 is transmitted to the primary shaft 411 of the continuously variable transmission mechanism 4 while the reverse brake 37 is engaged and the forward clutch 36 is released. Is fixed to the case 7 so that it cannot rotate, and the rotation of the ring gear 35 is changed to the pinion gears 32, 32,.
To the sun gear 34 to reverse the rotation of the turbine shaft 25 and transmit the rotation to the primary shaft 411 of the continuously variable transmission mechanism 4. When both the forward clutch 36 and the reverse brake 37 are released, a neutral state and a parking state in which the driving force of the engine is not transmitted from the turbine shaft 25 to the primary shaft 411 of the continuously variable transmission mechanism 4.

The continuously variable transmission mechanism 4 includes a primary pulley 41 as a drive pulley, a secondary pulley 42 as a driven pulley, and a V wound around these pulleys 41 and 42.
And a belt 43. The above primary pulley 41
Are a primary shaft 411 as a drive shaft disposed coaxially with the turbine shaft 25, a fixed sheave 412 fixed to the primary shaft 411 in a rotationally integrated manner, and a primary shaft 411 disposed facing the fixed sheave 412. 411 has a movable sheave 413 which is rotatably integrated and slidably supported,
The movement of the movable sheave 413 changes the pitch line of the V-belt 43, so that the effective pitch diameter (effective radius) changes. That is, when the movable sheave 413 approaches the fixed sheave 412, the effective pitch diameter increases, and when the movable sheave 413 separates from the fixed sheave 412, the effective pitch diameter decreases.

On the other hand, the secondary pulley 42 has basically the same configuration as the primary pulley 41 described above. That is, it has a secondary shaft 421 as a driven shaft arranged in parallel with the primary shaft 411, a fixed sheave 422 fixed to the secondary shaft 421, and a movable sheave 423 slidably supported. , The effective pitch diameter changes.

Hydraulic cylinders 414 and 424 for sliding the respective movable sheaves 413 and 423 are provided at the backs of the respective movable sheaves 413 and 423 in the respective pulleys 41 and 42. The configuration of the hydraulic cylinder 414 of the primary pulley 41 will be specifically described. The hydraulic cylinder 414 includes a first oil chamber 14a formed on the back side of the movable sheave 413, and a connecting member at the outer end of the movable sheave 413. A movable piston 14c connected integrally with the movable piston 14b, and a second oil chamber 14d formed on the back side of the movable piston 14c, and hydraulic pressure is applied to both the first and second oil chambers 14a and 14d. The movable sheave 413 is supplied to move the movable sheave 413 rightward in FIG.

On the other hand, similarly to the above, the configuration of the hydraulic cylinder 424 of the secondary pulley 42 includes a first oil chamber 15a formed on the back side of the movable sheave 423 and a connecting member 15 at the outer end of the movable sheave 423.
b, a second oil chamber 15d formed on the back side of the movable piston 15c, and a second oil chamber
A spring 15e, which is compressed in the inside of the oil chamber 15d and urges the movable piston 15c to the left in FIG. 3, and the first and second oil chambers 15a and 15d.
The movable sheave 423 is moved leftward in FIG.

The hydraulic cylinder 414 of the primary pulley 41
The total pressure receiving area of the first oil chamber 14a and the second oil chamber 14b is equal to the first oil chamber 15a of the hydraulic cylinder 424 of the secondary pulley 42 and the second oil chamber 14b.
The area is set to approximately twice the total pressure receiving area of the oil chamber 15d, and when hydraulic pressure is introduced into the hydraulic cylinder 414 of the primary pulley 41, the movable sheave 413 moves rightward in the drawing to move to the fixed sheave 412. , The pitch line of the V-belt 43 in the primary pulley 41 moves to the outer peripheral side, the effective pitch diameter of the primary pulley 41 increases, and the displacement of the V-belt 43 accompanying this causes the movable sheave 423 of the secondary pulley 42 to move. Move to the right in the figure to move away from the fixed sheave 422, the pitch line of the V belt 43 in the secondary pulley 42 moves to the inner circumference side, the effective pitch diameter of the secondary pulley 42 decreases, and the primary and secondary shafts
The gear ratio between 411 and 421 changes small (that is, in the speed increasing direction). Conversely, when the hydraulic pressure is discharged from the hydraulic cylinder 414, the movable sheave 413 of the primary pulley 41 moves to the left in the figure and moves away from the fixed sheave 412, and its effective pitch diameter decreases. The movable sheave 423 also moves to the right in the figure and approaches the fixed sheave 422,
The effective pitch diameter becomes large, and the gear ratio between the primary and secondary shafts 411 and 421 changes greatly (that is, in the deceleration direction).

The reduction mechanism 5 and the differential mechanism 6 have a known structure, and transmit the rotation of the secondary shaft 421 to the axle 61, although not described in detail here.

Next, the lock-up clutch 28 of the torque converter 2 in the above-described continuously variable transmission, the forward clutch 36 and the reverse brake 37 of the forward / reverse switching mechanism 3, the primary pulley 41 and the secondary pulley 42 of the continuously variable transmission mechanism 4, The hydraulic circuit for controlling each of the above operations will be described with reference to FIG.

The hydraulic circuit shown in FIG. 1 has an oil pump 81 driven by the engine 1. The hydraulic oil discharged from the oil pump 81 is first adjusted to a predetermined line pressure by a line pressure adjusting valve 82, and then supplied to a hydraulic cylinder 424 of the secondary pulley 42 via a line 101, Finally, it is supplied to a hydraulic cylinder 414 of the primary pulley 41 via a line 102 branched from the main pulley 41.

The line pressure adjusting valve 82 has a spool 820 composed of a main spool 821 and a sub spool 822 arranged in series. The main spool 821 and the sub spool 822 constituting the spool 820 are provided at one end of the main spool 821 with the sub spool 82.
It is connected so that one end of 2 is in contact. At the other end of the sub spool 822, a large-diameter portion 822a having a cross-sectional area larger than the contact area with the main spool 821 (cross-sectional area of the connection portion) is provided. At a position corresponding to the center of the main spool 821, there are provided a pressure adjusting port 823 through which oil discharged from the oil pump 81 is guided, and a drain port 824 communicating with the suction side of the oil pump 81.
Is shifted to the left in the figure, the connection between the pressure adjustment port 823 and the drain port 824 is shut off. When the main spool 821 is shifted to the right in the figure, the connection between the pressure adjustment port 823 and the drain port 824 is shut off, and the main spool 821 is shut off. On the other hand, when it is shifted to the right side in the figure, communication between the pressure adjustment port 823 and the drain port 824 is established. A first pilot chamber 825 is formed at a position corresponding to a connection portion between the main spool 821 and the sub spool 822, and a spring 826 for urging the main spool 821 to the left in the drawing is interposed in the first pilot chamber 825. Have been. Also, the secondary spool 822
A second pilot chamber 827 communicating with the first pilot chamber 825 is formed in the large diameter portion 822a. The first pilot room 825 and the second pilot room 827 have a line 102
After the hydraulic oil is reduced to a predetermined pressure by the reducing valve 83 while passing through the line 103 and then passing through the pilot passage 103a, the first duty solenoid valve
It is introduced as pilot pressure adjusted at 91. And this pilot pressure is
While acting in the same direction as the biasing force of 826, this spring 8
The hydraulic pressure in the line 101 acts on the other end of the main spool 821 so as to correspond to the urging force of 26 and the pilot pressure. The line pressure is controlled to a value corresponding to the pilot pressure regulated by the first duty solenoid valve 91 by communicating and shutting off the gap.

The line 102 is provided with a gear ratio control valve 85. The speed ratio control valve 85 includes a spool 851, a spring 852 for urging the spool 851 rightward in the figure, a line pressure port 853 connected to an upstream portion of the line 102, a drain port 854, and a spring 852. Reverse port 8 opening to the installation side and connected via line 104 to shift valve 87
55, and a pilot chamber 856 formed on the side opposite to the side where the spring 852 is installed and into which pilot pressure is introduced. The pilot chamber 856 is provided with a second duty solenoid valve 92 via a pitot valve 86 and a pitot pressure generating means 90 for generating a pitot pressure of a pressure corresponding to the rotation speed of the engine 1.
It is connected to the. Therefore, the pitot pressure generated by the pitot pressure generating means 90 and the second duty solenoid valve 92
And the pressure adjusted by the pitot valve 86 can be selectively introduced as pilot pressure into the pilot chamber 856 by the pitot valve 86. Even if the second duty solenoid valve 92 fails, the pitot pressure generating means 90 85
The pitot pressure can be introduced as pilot pressure in 6.

The gear ratio control valve 85 is operated at the time of forward movement (shift valve
87 is in the D, 2,1 shift position)
Since the hydraulic pressure is drained from the reverse port 855 through the shift valve 87, the spool 851 moves due to the force relationship between the pilot pressure introduced into the pilot chamber 856 and the biasing force of the spring 852, and the line pressure port 853 and the drain port
854 is selectively communicated with the hydraulic cylinder 414 of the primary pulley 41. In this way, at the time of forward movement, by controlling the supply and discharge of the hydraulic pressure to the hydraulic cylinder 414 of the primary pulley 41 according to the pilot pressure introduced into the pilot chamber 856, the primary pulley 41 of the continuously variable transmission mechanism 4 The gear ratio with the secondary pulley 42 is configured to be variably adjusted.

On the other hand, when the vehicle is moving backward (when the shift valve 87 is in the R shift position), hydraulic pressure (operating pressure described later) is introduced from the reverse port 855, and the operating pressure pushes the spool 851 to the right side in the drawing. Fixed in state. Therefore,
During reverse travel, the hydraulic cylinder 414 of the primary pulley 41 and the drain port 854 are always in communication, and the speed ratio is fixedly held at the maximum speed ratio.

It should be noted that the state is the same as when the vehicle is traveling backward during parking (when the shift valve 87 is at each shift position of P) when the driving force of the engine 1 is not transmitted to the axle 61 by the forward / reverse switching mechanism 3.

The hydraulic oil regulated by the line pressure regulating valve 82 is:
In addition to the line 101, it is also transmitted to a line 105. Line 105
Is supplied to the line 106 and the line 107 after being adjusted to a predetermined operating pressure by the operating pressure adjusting valve 88.

The operating pressure adjusting valve 88 includes a spool 881, a pilot chamber 882 formed at one end of the spool 881, a spring 883 interposed in the pilot chamber 882, and a first pressure adjusting port 884 connected to the line 105. , A second pressure adjustment port 885 connected to the line 107, and a drain port 886. The pilot chamber 882 is connected to the first duty solenoid valve 91 via the pilot passage 103a. Therefore, the pilot chamber 882 is provided with hydraulic oil regulated by the first duty solenoid valve 91 at the pilot pressure. It has been introduced as. The pilot pressure acts in the same direction as the urging force of the spring 883, while the line 105 is connected to the other end of the spool 881 so as to oppose the urging force of the spring 883 and the pilot pressure.
The hydraulic pressure within the spool 88
1 moves and the communication between the first and second pressure adjusting ports 884, 885 and the drain port 886 is interrupted, and the operating pressure of the forward clutch 36 and the reverse brake 37 is increased by the first duty solenoid valve 91. The pressure is controlled to a value corresponding to the pilot pressure to be adjusted.

The hydraulic oil supplied to the line 106 is supplied to the shift valve 87.
When the shift valve 87 is at the shift position of R, the shift valve 87 is at the shift position of R when the shift valve 87 is at the shift position of D, 2, 1 when the shift valve 87 is at the shift position of R.
Reverse brake 3 for forward / reverse switching mechanism 3 via line 108
7, and is supplied to the reverse port 855 of the speed ratio control valve 85 via the line 104. On the other hand, the hydraulic oil in the hydraulic chambers 36a, 37a of the forward clutch 36 and the reverse brake 37 of the forward / reverse switching mechanism 3 is discharged through the lines 109, 108 when the shift valve 87 is in the R, P shift position. It is supposed to be. Accordingly, the forward clutch 36 and the reverse brake 37 of the forward / reverse switching mechanism 3 are engaged and released in accordance with the shift position of the shift valve 87, and as described above, the stepless shift is performed in the R and P shift positions. The speed ratio of the speed change mechanism 4 is fixedly held at the maximum speed ratio.

The hydraulic oil supplied to the line 107 is supplied to a lock-up engagement chamber 29a or a lock-up release chamber 29b of the lock-up clutch 28 via a lock-up control valve 89. Lock-up control valve 89
The operation of the spool 891 is controlled by the pilot pressure regulated by the third duty solenoid valve 93. That is, when the pilot pressure decreases, the spool 891 moves to the right in the drawing,
, The hydraulic oil is supplied to the lock-up engagement chamber 29a, the hydraulic oil in the lock-up release chamber 29b is drained, and the lock-up clutch 28 is engaged.
On the other hand, when the pilot pressure increases, the spool 891 moves to the left in the drawing, and the hydraulic oil is supplied from the line 107 to the lock-up release chamber 29b, and the hydraulic oil in the lock-up fastening chamber 29a is drained. The engagement of the lock-up clutch 28 is released.

In the drawing, reference numeral 94 denotes a first duty solenoid valve 91.
Accumulator valves for preventing the pilot pressure in the pilot passage 103a from pulsating when the valve is turned ON / OFF.
Reference numeral 6 denotes an accumulator for alleviating a shock when the forward clutch 36 and the reverse brake 37 are engaged, and 97 denotes a relief valve. Reference numeral 98 denotes a pressure holding valve that holds a predetermined low constant pressure when draining the pressure oil in the hydraulic cylinder 414 of the primary pulley 41.

FIG. 5 shows an electric control circuit of the above-described continuously variable transmission. In this figure, a control unit 110 containing a microcomputer and the like includes a shift from a shift position sensor 111 for detecting a shift position (D, 1, 2, R, N, P) (shift range) by a driver's operation. The position signal, the primary pulley rotation speed signal from the primary rotation speed sensor 112 for detecting the primary rotation speed NP of the primary shaft 411, and the secondary pulley rotation from the secondary rotation speed sensor 113 for detecting the secondary rotation speed NS of the secondary shaft 421 A number signal, a throttle valve opening signal from a throttle opening sensor 114 for detecting the throttle valve opening TVO of the engine 1, and an engine speed signal from an engine speed sensor 115 for detecting the engine speed Ne. And a turbine speed signal from a turbine speed sensor 116 that detects the speed Nt of the turbine shaft 25 of the torque converter 2. It is adapted to be.

The control unit 110 controls the first to third duty solenoid valves 9 based on these input signals.
Duty control of 1, 92 and 93 is performed so that each pilot pressure introduced to the line pressure adjusting valve 82, the operating pressure adjusting valve 88, the speed ratio control valve 85 and the lock-up control valve 89 is adjusted. .

Next, the gear ratio control by the control unit 110 will be described based on the control flow of FIG. Start,
After reading the shift position, the primary rotational speed NP, the secondary rotational speed NS, and the throttle valve opening TVO in step S1, it is determined in step S2 whether the shift position is in the neutral range. If the shift position is in the D, 1, 2, R, or P range other than the neutral range, the process proceeds to step S3, where the engine speed (primary speed) / vehicle speed set in advance as shown in FIG. A shift map according to each of the shift ranges is selected from the (secondary rotation speed) / throttle opening degree map, and a target primary rotation speed NPt is searched and obtained based on the shift map.

On the other hand, if the determination in step S2 is YES for the "neutral range", the process proceeds to step S5, where a map of a low speed range (Low range or Second range) is selected from the shift map, and a target is selected based on the shift map. The primary rotational speed NPt is searched for and obtained.

After the step S3 or the step S5, the feedback control amount for performing the feedback control of the gear ratio so that the target primary rotational speed NPt retrieved in the step S6 coincides with the read actual primary rotational speed NP is set. Then, in step S7, a duty value corresponding to the feedback control amount is determined.

In this embodiment, the neutral range detecting means 120 for detecting that the shift position of the transmission has been selected to the neutral range is constituted by the step S2.

Further, in steps S5 to S7, the output of the neutral range detecting means 120 is received, and when the shift range is selected to the neutral range, the above-mentioned non-rotating speed is set so that the primary rotational speed NP becomes larger than the low rotational speed side line in the low speed range. A shift control means 121 for controlling the speed of the step speed change mechanism 4 is provided.

Therefore, in the above embodiment, when the gear ratio is changed to a small value, the second duty solenoid valve
The pilot pressure introduced into the pilot chamber 856 of the gear ratio control valve 85 increases by 92, and the spool 851 moves to the left in FIG. The line pressure flows into the hydraulic cylinder 414 of the primary pulley 41, the amount of the flow increases, and the hydraulic pressure acting on the hydraulic cylinder 414 increases. For this reason, the effective pitch diameter of the primary pulley 41 increases, and the effective pitch diameter of the secondary pulley 42 decreases.
On the other hand, when the gear ratio is changed to a large value, the spool 851 moves to the right in FIG. 4, contrary to the above, the amount of line pressure flowing into the hydraulic cylinder 414 decreases, and the hydraulic pressure decreases. Therefore, the effective pitch diameter of the primary pulley 41 decreases, and the effective pitch diameter of the secondary pulley 42 increases.

During such control, when the shift range is in a range other than the neutral range, a shift map according to each of the shift ranges is selected from a preset shift map (see FIG. 7). A target primary rotational speed NPt is obtained based on the shift map, and feedback control is performed so that the actual primary rotational speed NP becomes the target value NPt.

On the other hand, when the shift position is in the neutral range, the low speed range (Low range or
The map of (d range) is selected, the target primary rotational speed NPt is determined based on the shift map, and feedback control is performed in the same manner as described above.

In this way, in the neutral range, the continuously variable transmission mechanism 4
Is controlled such that the primary rotation speed NP becomes higher than the low rotation side line in the low speed range, and the speed ratio of the continuously variable transmission mechanism 4 is controlled to increase, so that even when the vehicle suddenly stops in the neutral state, , Secondary shaft 42
Before the rotation of 1 is stopped, the gear ratio is quickly switched to the increasing side. For this reason, when the vehicle restarts afterwards, a large starting drive force can be secured, and the restartability can be improved.

FIG. 8 shows a second embodiment of the present invention. When the neutral range is selected, the throttle opening TVO in the shift map is selected.
The shift control is performed in accordance with the fully open line.

In this embodiment, since the control procedure in the control unit 110 is different, the same parts as those in FIG. 6 are denoted by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described. That is, when the shift position is determined to be YES in the neutral range in step S2, the throttle opening TVO is imitated and fixed to "fully open" in step S4, and then the process proceeds to step S'5, where the throttle opening TVO is determined from the shift map. A target primary rotational speed NPt is searched based on the fully open line when TVO is fully open, and then, in step S6, the target primary rotational speed N searched above is searched.
A feedback control amount for feedback-controlling the gear ratio is calculated so that Pt matches the actual primary rotational speed NP.

Therefore, in this embodiment, the shift control means 121 'is constituted by steps S4 to S7. The other configuration is the same as that of the first embodiment.

Therefore, in this embodiment, the same operation and effect as those of the first embodiment can be obtained. In addition, since the speed ratio is controlled in accordance with the fully open throttle line in the speed change map, the speed ratio in the neutral range can be controlled to the increasing side more quickly, and the responsiveness can be further improved.

FIG. 9 shows a third embodiment, in which the shift control is performed so that the primary rotation speed NP becomes equal to the primary system guarantee limit rotation speed Nl in the neutral range.

That is, in this embodiment, when the shift position is determined to be YES in the neutral range in step S2, the process proceeds to step S ″ 5, and the target primary rotational speed NPt is secured during reverse driving from the wheel side in the neutral range. The rotation speed Nl is set based on the reliability of the bearing for supporting the primary shaft 411 when the drive side of the continuously variable transmission mechanism 4 is reversely driven from the wheel side in the neutral range. Then, the speed is made constant as shown in Fig. 7. Thereafter, the process proceeds to step S6, in which the gear ratio is feedback-controlled so that the retrieved target primary rotational speed NPt matches the actual primary rotational speed NP. To calculate a feedback control amount for performing the control.

Therefore, in this embodiment, steps S5 to S7 constitute the speed change control means 121 ". The other configuration is the same as that of the first embodiment.

Therefore, in the case of this embodiment, the same operation and effect as those of the first embodiment can be obtained, and the responsiveness of the speed ratio in the neutral range to the increasing side can be further improved.

(Effects of the Invention) As described above, according to the invention of claim (1), when the neutral range is selected in the continuously variable transmission,
By controlling the gear ratio to the increasing side, the gear ratio can be quickly switched to the increasing side even if the vehicle suddenly stops in the neutral state due to panic brakes, etc. Power can be secured and re-startability can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of the present invention. 2 to 7 show a first embodiment of the present invention, FIG. 2 is a skeleton diagram showing an entire configuration of a continuously variable transmission, FIG. 3 is an enlarged sectional view of the same, and FIG. 4 is a hydraulic control circuit. FIG. 5, FIG. 5 is a block diagram of the electric control system, FIG. 6 is a flowchart of the speed ratio control in the control unit, and FIG. 7 is a characteristic diagram showing a map of the speed ratio control. FIG. 8 and FIG. 9 are views corresponding to FIG. 6 showing the second and third embodiments of the present invention, respectively. DESCRIPTION OF SYMBOLS 1 ... Engine 3 ... Forward / reverse switching mechanism 4 ... Continuously variable transmission mechanism 41 ... Primary pulley 42 ... Secondary pulley 43 ... Belt 91 ... Duty solenoid valve 411 ... Primary shaft 421 ... Secondary shaft 414,424 ... Hydraulic cylinder 120 ... Neutral range detecting means 121, 121 ', 121 "... shift control means NP ... drive side rotation speed

Claims (6)

(57) [Claims] 1. A continuously variable transmission mechanism having a driving and driven pulley composed of a variable pulley and a belt wound between the two pulleys. In a continuously variable transmission in which a shift range including a range, a low speed range, a neutral range, and a reverse range is set, a neutral range detecting means for detecting that the shift range is selected to be a neutral range, and an output of the detecting means. A transmission control means for controlling the speed of the continuously variable transmission mechanism so that, when the neutral range is selected, the drive-side rotational speed is higher than the low-speed side line in the low-speed range. Control device. 2. The control device for a continuously variable transmission according to claim 1, wherein a forward / reverse switching mechanism is connected to an input side of the continuously variable transmission mechanism. 3. The shift control means reads a map value from the shift map, when the neutral range is selected, in which the target drive-side rotational speed is greater than the low-speed line in the low-speed range set in the shift map. 3. The control device for a continuously variable transmission according to claim 1, wherein a shift control is performed based on the map value. 4. The shift control means calculates a target drive-side rotational speed based on a shift map in a low-speed range when the neutral range is selected, and the actual drive-side rotational speed becomes the calculated target drive-side rotational speed. The control device for a continuously variable transmission according to any one of claims 1 to 3, wherein the feedback control is performed as described above. 5. The shift control means calculates a target drive-side rotational speed based on a fully-opened line when the throttle degree is fully open from a shift map when a neutral range is selected, and obtains an actual drive-side rotational speed. The control device for a continuously variable transmission according to any one of claims 1 to 3, wherein feedback control is performed so as to reach a target drive side rotation speed. 6. The transmission control means, when the neutral range is selected, sets the target drive-side rotational speed to the guaranteed rotational speed on the drive side when the drive side of the continuously variable transmission mechanism is reversely driven from the wheel side in the neutral range. The control device for a continuously variable transmission according to any one of claims 1 to 3, wherein the control device performs feedback control so as to set the actual rotation speed on the driving side to the guaranteed rotation speed.