JPS59103066A - Control method of automatically controlled power transmission for vehicle - Google Patents

Abstract

PURPOSE:To improve safety at the time the neutral range by disengaging a friction clutch and shifting the transmission to the neutral position when the manual shift range is set to the neutral range. CONSTITUTION:When the engine is started, with the manual shift range in the neutral or parking range, an oil pump is driven to generate an oil pressure to supply an ON signal from a control device to an electromagnetic switch valve, a clutch disc member 35 is separated from a flywheel 23. When this disengagement is detected by the first clutch sensor, and when the second clutch comprising the flywheel 23 and a clutch disc member 45 is detected to be separated by the second clutch sensor, the control device verifies whether or not a speed gear shifting apparatus 2 is in the neutral position, and when it is not in the neutral position, a control is made so that electrification of all the solenoid valves may be terminated to shift into the neutral position. Thus, safety at the time of the neutral range is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatically controlled power transmission device used in vehicles such as automobiles, and particularly to a control method when a manual shift range is set to a neutral range.

a friction clutch, a transmission that selectively inputs the rotational power of the prime mover via the friction clutch and switches between a neutral gear position and a plurality of gear positions, a manual shift range determined by the driver, and an output state of the prime mover. An automatically controlled power transmission device for a vehicle has been proposed in the past, which has a control device that controls the engagement of the friction clutch and controls the switching of the transmission according to the running state of the vehicle.

In the above-mentioned automatically controlled vehicle power transmission system, transmission of the rotational power of the prime mover to the drive wheels of the vehicle stops when the friction clutch is disengaged or the transmission is switched to a neutral gear. As a result, the vehicle is no longer driven by the prime mover, and a so-called neutral range is achieved.

An object of the present invention is to provide a control method that further enhances the safety in the neutral range of the above-mentioned automatic restraint type vehicle power transmission system, and this purpose, according to the present invention, This is achieved by a control method such as disengaging the friction clutch and switching the transmission to the neutral gear when the range is set to the neutral range.

According to the present invention, even if either the friction clutch or the transmission malfunctions in the neutral range, the neutral range state is maintained, and the friction clutch is disengaged or the transmission is shifted to the neutral gear. Safety in the neutral range is higher than in the case where only

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing one embodiment of an automatically controlled vehicle power transmission device suitable for implementing the control method according to the present invention, and FIG. 2 is a longitudinal sectional view of the vehicle power transmission device shown in FIG. It is a skeleton diagram. In these figures, 1 indicates a friction clutch, and 2 indicates a gear transmission.

The gear transmission 2 includes a first hollow input shaft 3 which is rotatably supported in the gear case 52 by a bearing 5354, and a second input shaft which is provided through the hollow part of the input shaft 3. A first continuous drive gear 5, a third speed drive gear 6, and a reverse drive gear 7 are fixed to the first input shaft 3, and a second input shaft 4 The 23rd! The driving gear 8 and the fourth driving gear 9 are fixed.

The gear transmission 2 has one output shaft 10 provided in a gear case 52 parallel to the input shaft and rotatably supported by the gear case 52 by bearings 55,56.

The output shaft 10 includes a first speed driven gear 11, a second speed driven gear 12, a third speed driven gear 13, and a fourth speed driven gear 14.
and are provided rotatably, respectively, and an output gear 15
is fixed. 1st speed to 4th speed driven gear 11~
14 are always in mesh with the first to fourth gears.

The output shaft 10 is equipped with a first speed-third speed synchronizer 16 and a second speed synchronizer 16.
A speed-fourth speed synchronizer 17 is provided. These synchronizers are of a well-known inertia lock type known as a Borgwana synchromesh device, and include clutch hubs 16a, 17a, cone members 16b, 16c and 171), 17C, and a synchronizer ring. 16d, 16e and 17d, 17e,
It includes synchronizer sleeves 16f and 17f and shifting keys 16g and 17g. The first speed-third speed synchronizer 16 selectively connects either the first speed driven gear 11 or the third speed driven gear 13 to the output shaft 10 in a torque transmission relationship, and and third gear are selectively achieved. Further, the second speed-fourth speed synchronizer 17 selectively connects either the second speed driven gear 12 or the fourth speed driven gear 14 to the output shaft 10.
- are connected in a torque transmission relationship to selectively achieve either the second gear or the fourth gear.

A reverse driven gear 18 is integrally provided on the synchronizer sleeve 16f of the first-third speed synchronizer 16. As shown in FIG. 2, the gear transmission 2 has a reverse intermediate gear 20 attached to a shaft 19 so as to be slidable and rotatable in its axial direction. 2
0 is the reverse drive gear 7 by moving to the left in the figure.
and the reverse driven gear 18 at the same time to selectively achieve the reverse gear.

The gear transmission 2 includes two fork shafts 58 that are provided in a gear case 52 parallel to the input shaft 3.4 and the output shaft 10 and supported by the gear case 52 so as to be movable in the axial direction thereof.
．． It has 59. The fork shaft 58 has 1st speed - 3rd speed.
A fork portion tJ60 that engages with the synchronizer sleeve 16f of the speed synchronizer 16 and drives it in the axial direction.
is fixed. An A-ri member 61 (which engages with the synchronizer sleeve 17f of the second-fourth speed synchronizer 17 to drive it in the axial direction) is fixed to the fork @59, and an intermediate gear 20 for reverse movement is fixed to the fork @59. A fork member 57 is provided so as to be movable in the axial direction. Three click stop grooves 62, -6, 1 and 65 to 67 are provided in each of the fork shafts 58 and 59, and these click stock grooves are provided with click stop grooves (not shown) provided in the gear case 52. The check ball is selectively engaged.This click-stop mechanism allows the fork @58.59 to be moved to the neutral position as shown in the figure and to the right side moved from the neutral position to the right in the figure. position and a left position, which is moved leftward in the figure from the neutral position, with a sense of moderation.

The first speed-third speed synchronizer 16 is in the neutral position when the fork shaft 58 is in the neutral position, and the first speed driven gear 1
Both the 1st and 3rd speed driven gears 13 are separated from the output shaft 10, and when the fork shaft 58 is on the right side, the synchronizer sleeve 16f is driven to the right in the figure, and the 1st speed driven gear 13 is separated from the output shaft 10. 11 is connected to the output shaft 1o in a torque transmission relationship, and when the free shaft 58 is in the left position, the synchronizer sleeve 16f is driven to the left in the figure, thereby outputting the third speed driven gear 13. axis 1
0 in a torque transmission relationship.

The second speed-fourth speed synchronizer 17 is in the neutral position when the fork shaft 59 is in the neutral position, and the second speed driven gear 1
When the fork shaft 59 is in the right position, the synchronizer sleeve 16f is driven to the right in the figure, and the second and fourth driven gears 14 are separated from the output shaft 10. 12 is connected to the output shaft 10 in a torque transmission relationship, and when the fork shaft 59 is in the left position, the synchronizer sleeve 17f is driven to the left, thereby connecting the fourth linked driven gear 14 to the output shaft 10 in a torque transmission relationship. It is supposed to connect.

The fork shafts 58 and 59 are each driven by a shift release cylinder device 68.6 between a neutral position, a right-hand position, and a left-hand position. The shift release cylinder devices 68, 69 are each attached to an end cover 70 fixed to one end of the gear case 52. When no oil pressure is introduced into either of the oil chambers 72, 73 provided on both sides of the piston 71, the shift release cylinder device 68 is in a neutral position as shown in the figure by the action of a spring 74, 75, and the shift release cylinder device 68 is in a neutral position as shown in the figure by the action of a spring 74, 75. - When hydraulic pressure is introduced into the oil chamber 72, the fork shaft 58 is driven to the right position, and when hydraulic pressure is introduced into the oil chamber 73, the fork shaft 58 is moved to the left position. It is designed to be driven to. The shift release cylinder device 69 has oil chambers 77 provided on both sides of the piston 76.
When hydraulic pressure is not introduced into any of the oil chambers 78, the fork shaft 59 is brought to the neutral position as shown in the figure, whereas when hydraulic pressure is introduced into the oil chamber 79, the fork shaft 59 is brought to the right position. and the oil chamber 7
When hydraulic pressure is introduced into the fork shaft 59, the fork shaft 59 is driven to the left position.

A shift release cylinder device 81 is attached to the fork member 57.
(see FIG. 3) are drivingly connected.

This shift release cylinder device 81 is installed on one side of the piston 82 (when no oil pressure is introduced into the blocked oil chamber 83, it is located at the right side by the action of a spring 84).
The reverse intermediate gear 20 is brought to a position apart from the reverse drive gear 7 and the reverse driven gear 18 via the A-ribbon member 57, and on the other hand, when hydraulic pressure is introduced into the oil chamber 83, the fork member 57 is moved to the second position. Drives to the left as seen in Figure 1, intermediate gear 2
o is driven to a position where it meshes with the reverse driving gear 7 and the reverse driven gear 18 at the same time.

The output shaft 15 is always meshed with an input gear (ring gear) 86 of a differential gear device 85. The differential gearing 85 is of a type known per se and includes two pairs of bevel gears 87,88.
and 89.90, of which a pair of bevel gears 87.8
8 is rotatably supported by a case 92 by a shaft 91 and connected to an input gear 86, and the other pair of bevel gears 89 and 90
are meshed with bevel gears 87 and 88 at the same time, and are connected to left and right output shafts 93 and 94, respectively. The output shafts 93 and 94 are connected to left and right drive wheel axles.

The clutch 1 has a clutch housing 21, and a flywheel 23, which is an input member, is provided inside the clutch housing 21. The flywheel 23 is drivingly connected to an output member of a prime mover, such as an internal combustion engine (not shown), for rotation about the axis of the input shaft.

Further, the flywheel 23 supports the end of the second input shaft 4 by a bearing 24.

An annular first frictional engagement surface 25 is provided on one end surface of the flywheel 23 . Further, a clutch cover 27 is attached to one end of the flywheel 23 with bolts 26. Inside the clutch cover 27, a pressure plate 28 having an annular shape is disposed opposite to the first frictional engagement surface 25.
is provided so as to be movable in its axial direction. A diaphragm spring 3o is provided in the clutch force bar 27, and this diaphragm spring 3o is connected to the clutch cover 27 by a pin 29 at its intermediate portion, and is connected to the pressure plate by a connector 28a at its outer peripheral edge. 28, and engages with the clutch release bearing 31 at the tongue-shaped inner edge, biasing the pressure plate 28 toward the first friction engagement surface 25, that is, toward the right in FIG. The clutch release bearing 31 is slidably supported in the axial direction on the outer periphery of a sleeve member 33 attached to the tarlatch housing/g 21 by screws 32, and the clutch release fork 34 is attached to the clutch release bearing. One end is engaged.

This release fork 34 is pivoted to the clutch housing 21 by a pivot structure (not shown) at its intermediate portion, and the clutch release cylinder device 95 (third
(see figure), and is pivotally driven by the cylinder device. A clutch disc member 35 is provided between the flywheel 23 and the pressure plate 28. This clutch disc member 35 is spline-coupled to the first input shaft 3 /j
A hub member 36, a disc plate 38 provided with a facing 37 at a portion located between and facing the first frictional engagement surface 25 and the pressing surface 28b of the pressure plate 28, the hub member 36 and the disc plate. 38 and a torsion elastic member 39 that connects with the torsion elastic member 39. The structure of the clutch described above is the same as that of a known dry type clutch, and this clutch is designated as the first clutch in the flowchart shown in FIG.

The flywheel 23 has a cylindrical portion 40 whose one end is substantially closed by the flywheel at a portion inside the first frictional engagement surface 25, and this cylindrical portion has a second cylindrical portion 40 on one end surface. A frictional engagement member 42 having a frictional engagement surface 41 is fixed to close the other end of the cylindrical portion. Also, the cylindrical part 4
A pressure piston 43 is provided in the 0 so as to be movable in the axial direction, facing the second frictional engagement surface 41, and this pressure piston 43 has an oil chamber 44 on the side opposite to the frictional engagement member 42. It has a return spring of 50
It is urged in a direction away from the second frictional engagement surface 41, that is, to the right in the figure. A second input shaft 4 is provided in the oil chamber 44.
Hydraulic pressure is selectively supplied from an oil passage 51 provided in the.

A clutch disc member 45 is provided between the frictional engagement member 42 and the pressure piston 43. The clutch disc member 45 includes a hub member 46 that is spline-coupled to the second input shaft 4 that extends through the frictional engagement member 42 and the pressure piston 43, and a second frictional engagement surface 4.
1 and the pressure surface 43a of the pressure piston 43, and a torsion spring 49 connects the hub member 46 and the disk plate 48. ing. This clutch is designated as the second clutch in the flowchart shown in FIG.

When oil pressure equal to or higher than a predetermined value is supplied to the oil chamber 96 of the clutch release cylinder device 95, the clutch release fork 34 pivots to release the clutch release fork 3.
4 moves to the right in the figure, the clutch release bearing 31 is guided by the sleeve member 33 and moves to the right in the figure, and as a result, the diaphragm spring 30 moves the pin 29. By elastically deforming as a pivot point, the pressure plate 28 moves to the left in the figure, and the facing 37 of the clutch disc member 35 engages the first frictional engagement surface 25 of the flywheel 23 and the pressing surface 28b of the pressure layer plate 28. The flywheel 23 and the first input shaft 3 are separated from each other. The end of the clutch release fork 34 moves to the left in the figure as the oil pressure in the oil chamber 96 of the clutch release cylinder device 95 decreases, and the clutch release bearing 31 is guided by the sleeve member 33 as shown in the figure. By moving the pressure plate 28 to the left, the diaphragm spring 30
When the hydraulic pressure drops below a predetermined value, the pressure plays 1 to 28 come into contact with the clutch disc member 35, and the facing 37 of the clutch disc member 35 is moved by the spring force of the diaphragm spring 30.
is sandwiched between the first engaging surface 25 of the flywheel 23 and the pressing surface 28a of the pressure plate 28, and is pressed by them, and the frictional force between them causes the flywheel 23 to
and the first input shaft 3 are drivingly connected. The clamping force, that is, the clutch engagement load is proportional to the amount of movement of the end of the clutch release fork 34 to the left in the figure as the oil pressure in the oil chamber 96 decreases, that is, the clutch stroke increases. increase The operation and clutch characteristics of this clutch are substantially the same as those of conventional dry clutches.

Oil room 4I! When the hydraulic pressure higher than a predetermined value is not supplied to I, the pressure piston 43 returns to the return spring 50.
As it is displaced to the right in the figure by the spring force, it moves away from the frictional engagement surface 41, and the facing 47 of the clutch disc member 45 and the second frictional engagement surface 41 of the frictional engagement member 42 and Since no substantial frictional force is generated between the pressure piston 43 and the suppression surface 43a, the flywheel 23 and the second input shaft 4 are separated.

On the other hand, when oil pressure is supplied to the oil chamber 44 from the oil passage 51, the pressure piston 43 moves to the left in the figure against the action of the return spring 50, thereby causing the facing of the clutch disc 45 to move. 47 is sandwiched between and compressed by the second frictional engagement surface 41 of the frictional engagement member 42 and the suppression surface 43a of the pressure piston 43, and the frictional force between them causes the flywheel 23 and the second input A shaft 4 is drivingly connected thereto. This clutch engagement load increases proportionally as the oil pressure in the oil chamber 44 increases.

Oil chamber 44 of clutch 1, oil chamber 96 of clutch release cylinder device 95, shift release cylinder device 68.6
Oil supply and drainage to and from the oil chambers 73, 74, 77, and 78 of No. 9 are controlled by a hydraulic circuit device as shown in FIG.

In FIG. 3, reference numeral 100 indicates an oil pump, and the oil pump 100 sucks hydraulic oil from an oil tank 101 and generates hydraulic pressure. This oil pressure is regulated by a pressure regulating valve 102 and supplied to a conduit 103 as a constant line oil pressure.

Conduit 103 is connected via conduits 104 to 110 to one port a of electromagnetic switching valves 111 to 117, respectively.

Each of the electromagnetic switching valves 111 to 117 is configured as a three-way switching valve, and has two ports b and C in addition to port a. Port b of the electromagnetic switching valve 111 is connected to the oil chamber 96 via a conduit 118, and port b of the electromagnetic switching valve 112 is connected to the conduit 119.
The port b of the electromagnetic switching valve 113 is connected to the oil chamber 72 via the conduit 120, and the port l of the electromagnetic switching valve 114 is connected to the oil chamber 44 through the conduit 120.
) is connected to the oil chamber 77 via a conduit 121, port b of the electromagnetic switching valve 115 is connected to the oil chamber 73 via a conduit 122, and the port b of the electromagnetic switching valve 115 is connected to the oil chamber 73 via a conduit 122.
The port b of the electromagnetic switching valve 117 is connected to the oil chamber 78 through a conduit 123, and the port b of the electromagnetic switching valve 117 is connected to the oil chamber 83 through a conduit 124. Ports C of the electromagnetic switching valves 111 to 117 are connected to the oil tank 10 through drain pipes 125 to 131, respectively.
Connected to 1.

Each of the electromagnetic switching valves 111 to 117, 132, and 133 connects port b to port a when energized, and connects port b to port C when not energized. Control of energization to these electromagnetic switching valves is performed by an electric control device 140.

The control device 140 includes a general microcomputer equipped with a CPU and a storage device, input/output circuits, etc., and controls the throttle opening of the prime mover detected by the throttle opening sensor 141 and the vehicle speed detected by the vehicle speed sensor 142. information regarding the manual shift range detected by the shift lever switch 143, the rotation speed of the prime mover detected by the rotation speed sensor 144, the shift state detected by the shift switch 145, and the first clutch and second clutch sensors. 146 and 147 regarding the disengaged state of the first and second clutches detected by the clutches 146 and 147.
An on/off signal or a pulse signal with a predetermined duty ratio is selectively output to each of the electromagnetic switching valves 111 to 117 so that the switching is performed on and off.

Next, the control procedure for the automatically controlled vehicle power transmission system constructed as described above will be explained with reference to the flowchart shown in FIG.

When the vehicle is left alone, the prime mover is not being driven, so the oil pump 100 is stopped and no oil pressure is generated. In addition, since the control device 141 is not energized, each electromagnetic switching valve is not energized, and the oil v72.73.7
Since 7, 78, 83 and 96, 44 are each connected to a drain conduit, no gear is achieved and the gear transmission 2 is in a neutral membrane state. Further, at this time, only the clutch disc member 35 is connected to the flywheel 23 because oil pressure is not supplied to the oil chamber 44 and the oil chamber 46.

When the manual shift range is set to the neutral range or the parking range, the prime mover is started, and the control device 140 is energized, the oil pump 100 is driven and line oil pressure is generated in the conduit 103. Further, a signal is applied to the electromagnetic switching valve 111 from the control device 140,
When this is energized, the port is connected to the boat a, and line oil pressure is supplied to the oil chamber 96. As a result, the clutch disc member 35 is separated from the flywheel 23. At this time, since the electromagnetic switching valve 112 is not energized, its port O remains connected to the boat C, and the clutch disc member 45
maintains a state separated from the flywheel 23.

In the neutral range or parking range, the first clutch sensor 146 detects that the first clutch between the flywheel 23 and the clutch disc member 35 is disengaged, and the first clutch between the flywheel 23 and the clutch disc member vJ45 is detected. When the second clutch sensor 147 detects that the second clutch is disengaged, the controller 140 determines whether the gear transmission 2 is actually in the neutral state based on the information regarding the shift state detected by the IJ shift switch 145. At this time, if the gear transmission 2 is not in the neutral membrane state, the electromagnetic switching valves 11 to
Control is performed so that the power supply to 117 is stopped and the gear transmission @2 is in the neutral gear.

For forward start, based on the manual shift range being set to a forward travel range such as the D range, the first speed driven tooth weight 11 is in a torque transmission relationship to the output shaft 10 by the first speed-third speed synchronizer M16. In other words, the first forward speed is achieved, after which the rotational speed of the prime mover becomes equal to or higher than a predetermined value,
The clutch disc member 35 is interposed between the pressure plate 28 and the flywheel 23, and rotational power is thereby transmitted from a prime mover (not shown) to the first input shaft 3.

When the vehicle is moving forward, the gear shift is performed in accordance with the first shift pattern determined in advance according to the throttle opening and the vehicle speed.
The synchronizer 16 for third speed and the synchronizer 17 for second speed and fourth speed connect the driven gears 11 to 14 to the output shaft 10 and connect and disconnect the first and second clutches included in the clutch 1. It will be done. During normal driving, only one of the first and second clutches is kept connected and the other is released (disconnected). When shifting gears, the clutch that has been in the released state starts to be connected, and at the same time, the clutch that has been in the released state starts to be connected. The clutch that was in the engaged state starts to be released, and the engaged states of the two clutches are reversed.

For a reverse start, the fork member is driven by the shift release cylinder device 81 only when the shift lever switch 143 detects that the manual shift range is set to the reverse range and the vehicle speed detected by the vehicle speed sensor 142 at this time is approximately O. As a result, the reverse intermediate gear 20 simultaneously meshes with the reverse drive gear 7 and the reverse driven gear 18 to achieve the reverse gear, and after this, the rotational speed of the prime mover exceeds a predetermined value, and the clutch disc The member 35 is held between the pressure plate 28 and the flywheel 23, and rotational power is thereby transmitted from a prime mover (not shown) to the first input shaft 3.

Although the present invention has been described in detail above with reference to specific embodiments, it is understood that the present invention is not limited thereto and that various embodiments are possible within the scope of the present invention. This will be obvious to businesses.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of an automatically controlled vehicle power transmission device suitable for applying the control method according to the present invention, and FIG. 2 is a longitudinal sectional view of an automatically controlled vehicle power transmission device shown in FIG. 1. FIG. 3 is a skeleton diagram of the power transmission device, FIG. 3 is a control circuit diagram of a control device used to implement the control method according to the present invention, and FIG. 4 is a flowchart showing the procedure for implementing the control method according to the present invention. DESCRIPTION OF SYMBOLS 1... Clutch, 2... Gear transmission, 3... First input shaft, 4... Second input shaft, 5-9... Drive gear. 10... Output shaft, 11-14... Driven gear, 15.
...Output gear, 16.17...Synchronizer, 18...
Reverse driven gear, 19... Shaft, 20... Reverse intermediate gear, 21... Clutch housing, 23... Flywheel. 24... Bearing, 25... First friction engagement surface, 26...
...Bolt, 27...Clutch cover, 28...Pressure plate, 29...Bin, 30...Diaphragm spring, 31...Clutch release bearing,
32...Screw, 33...Sleeve member, 34...
Clutch release fork, 35... Clutch disc member, 36... Hub member, 37... Facing, 38... Disc plate, three... Torsion elastic member, 40... Cylindrical part, 41 . . . second friction engagement surface, 42 . . . friction engagement member, 43 . . . pressure piston, 44 . . . oil chamber. 45...Clutch disc member, 46...Hub member. 47...Facing, 48...Disc plate. 49... Torsion spring, 50... Return spring, 51... Oil path, 52... Gear case,
53-56 Bearing, 57 Fork member, 58
．． 59... Fork shaft, 60.61... Fork member, 62-67... Click stop groove, 68.69
-...Shift release cylinder device, 70...End cover. 71...Piston, 72.73...Oil chamber, 74.7
5... Spring, 76... Piston, 77.78...
Oil chamber, 79.80... Spring, 81... Shift release cylinder device, 82... Piston, 83... Oil chamber, 84... Spring. 85...Differential gear device, 86...Input gear, 87~
90...Bevel gear, 91...Shaft, 92...Case,
93.94... Output shaft, 95... Clutch release cylinder device, 96... Oil chamber, ioo... Oil pump, 101... Oil tank, 102... Pressure regulating valve, 103
~110... Conduit. 111-117...Solenoid switching valve, 118-124...
・Conduit, 125-131...Drain conduit, 140...
・Control device, 141... Throttle opening sensor, 14
2... Vehicle speed sensor, 143... Shift lever switch. 144... Rotation speed sensor, 145... Shift switch. 146...First clutch switch, 147...Second
clutch switch

Claims (1)

[Claims] a friction clutch, a transmission that selectively inputs the rotational power of the prime mover via the friction clutch and switches between a neutral gear position and a plurality of gear positions, a manual shift range determined by the driver, and an output of the prime mover. A control method for an automatically controlled vehicle power transmission device having a control device for controlling engagement of the friction clutch and controlling switching of the transmission according to a driving state of the vehicle and a driving state of the vehicle, wherein the manual shift range is a neutral range. A control method characterized in that when the friction clutch is set to 1, the friction clutch is disengaged and the transmission is switched to a neutral gear.