JPH11173409A - Vehicle speed change control device - Google Patents

Abstract

(57) [Problem] Conventionally, like a tractor for agricultural use, the rotational power of an engine is transmitted to front and rear wheels via a hydraulic multi-plate clutch type forward / reverse switching device and a synchromesh gear type main transmission. In some cases, when the main transmission is switched, the hydraulic multi-plate clutch is once turned off to cut off the rotational power, and then the gear is switched by expanding and contracting a piston of a hydraulic cylinder for shifting. However, when the forward / reverse switching device is configured to switch on and off in the same pattern both at the time of shifting and at the time of starting, there is a problem that a shock occurs at the time of the original press-bonding between multiple plates or a long operation time is required. A branch passage (78) for connecting an accumulator (8) to a hydraulic circuit between a multi-plate clutch (2A) of the forward / reverse switching device of the vehicle and a control valve (75) for supplying pressure oil to the clutch (2A). A switching control valve 7 for connecting and disconnecting the connection 78 is provided, and the clutch press-up pattern at the time of shifting and at the time of starting can be changed by the switching operation of the switching control valve 7.

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 vehicle.

[0002]

2. Description of the Related Art Conventionally, as in an agricultural tractor disclosed in Japanese Patent Application Laid-Open No. 8-128529, a hydraulic multi-disc clutch type forward / backward switching device is used for rotating the engine. The transmission is transmitted to the front and rear wheels via the synchromesh gear type main transmission, and when switching the main transmission, the hydraulic multi-plate clutch is temporarily turned off to cut off the rotational power and then extend or retract the hydraulic cylinder piston for shifting. Some gears were configured to switch gears.

As described above, the forward / reverse switching device is constituted by a hydraulic multi-plate clutch and the clutch is turned off when the synchro gear is switched. In this case, a separate clutch is provided for the synchro gear. In comparison, the vehicle length is reduced and the manufacturing cost is reduced. However, if the clutch is pressurized in a fixed pattern between on / off during shifting and forward / backward switching, or on / off when starting the vehicle, the shifting time becomes longer or a shock occurs when multiple plates are crimped together. There were challenges.

[0004] In particular, it is desired that the clutch of the forward / reverse switching device be quickly pressurized when the multiple discs are engaged or disengaged at the time of shifting, but the clutch connection pressure is gradually increased during forward / reverse switching. It is desired to reduce connection shock.

[0005]

The present invention employs the following technical means in order to solve the above problems. That is, the rotational power of the engine 1 is transmitted to the drive wheels 1 via the forward / reverse switching device 3 and the gear type transmission 4 in the form of a multi-plate clutch.
4 (15), when the gear type transmission 3 is switched, in the vehicle speed change control device for temporarily turning off the power transmission by the multi-plate clutch, the multi-plate clutch 2 of the forward / reverse switching device 3 A hydraulic circuit between the control valve 75 and the control valve 75 for supplying pressure oil to the clutch 2 is provided with a branch path 78 for connecting the accumulator 8 and a connecting and disconnecting means 7 for connecting and disconnecting the branch path 78. 7. A shift control device for a vehicle, characterized in that the clutch press-up pattern at the time of shifting and at the time of starting can be changed by an on-off operation of the on-off switch 7. The on-off means 7 interrupts connection to the accumulator 8 during shifting. In addition, the present invention provides a shift control device for a vehicle, which communicates at the time of starting.

[0006]

In the vehicle constructed as described above, the connecting and disconnecting means 7 connects or disconnects the accumulator 8 when the power is switched on and off when the gear is switched using the hydraulic multiple disc clutch 2 of the forward / reverse switching device 3. By doing so, the pressure increase pattern of the clutch 2 can be changed.

That is, when the forward / reverse switching device 3 itself is turned on at the time of starting, the accumulator 8 is connected so that a gradual pressure increase can be performed, and the shock at the time of clutch press-fitting is reduced. In addition, when the gears of the transmission 4 are switched, the hydraulic clutch 2 is stepped up without connecting the accumulator 8, and the shift can be completed quickly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings for an agricultural tractor (hereinafter, tractor 10). First, the overall configuration of the tractor 10 will be described. The tractor 10 is provided with an axle bracket 11 provided at a lower front portion of a vehicle body, an engine 1 mounted thereon, and a clutch housing, a transmission case 13F, a rear transmission case 13R, and the like integrally connected from the engine 1 and provided. It constitutes the main frame of the vehicle body.

A front axle housing is provided below the axle bracket 11 so as to be swingable, and front wheels 14, 14 are provided at the front end thereof so as to be steerable. Rear wheels 1 are provided on the left and right sides of the rear transmission case 13R.
5, 15 are provided. A handle post 18 is provided behind the bonnet 16 surrounding the engine 1, and a forward / reverse switching lever 19 is provided on a side of the handle post 18, and a steering handle 20 is provided above the post 18 so as to project therefrom. Further, a forward switch 21 and a reverse switch 22 are arranged at the rotation base of the forward / reverse switching lever 19, and a lever operation position of an operator is detected and transmitted to a controller 23 which is a control unit described later. . Further, the front wheel 14 is steered through a power steering device by rotating the steering handle 20. A clutch pedal 24 is provided below the handle post 18.

The vicinity of the cockpit 25 of the tractor 10 will be described. To the side of the cockpit 25, a shift lever 27 for switching between a main transmission 4 and a subtransmission 26, which will be described later, and a height of a working machine are set. Position lever 28 to change
And so on. A speed-up switch 29 and a deceleration switch 30 are provided on the gripping portion of the speed-change lever 27, and the main transmission 4 is stepped up or down by one step each time the switch 29 (30) is pressed. I have. In the vicinity of the guide of the lever 27, a PTO on / off switch 84 for turning on / off the rotation of a PTO shaft 38 described later is provided. The sub-transmission 26 is configured to move the lever 27 along an H-shaped lever guide, and to switch among four stages of a high speed H, a medium speed M, a low speed L, and a very low speed LL via a link mechanism.

The structure of the rear part of the tractor 10 will be described. At the rear upper part of the rear transmission case 13R, a cylinder case 36 containing a hydraulic cylinder 35 for lifting and lowering the work implement is provided. The lift arms 37, 37 supported on the left and right sides of the case 36 are vertically rotated by the expansion and contraction of the piston of the hydraulic cylinder 35. The rear of the rear transmission case 13R has a P
The TO shaft 38 is provided so as to protrude, and a three-point link mechanism including a top link 39 and left and right lower links 40, 40 is provided at a rear portion and a side portion, and a working machine can be connected to the rear end portion. I have. In the example of FIG. 2, the rotary working machine 41 is connected.

Next, the power transmission configuration of the tractor 10 will be described with reference to FIG. The rotational power of the engine 1 is interrupted by a main clutch 45 operated by the clutch pedal 24 and is input to the forward / reverse switching device 3. The forward / reverse switching device 3 includes a wet-type hydraulic multi-plate clutch 2A for forward movement and a wet-type multi-plate hydraulic clutch 2B for reverse movement provided in series on an output shaft 46. The power is switched between forward and reverse and transmitted to the output shaft 46.

The main transmission 4 is a synchromesh gear type transmission and is controlled by an energization command from the controller 23.
First hydraulic cylinder 47A for switching to third speed or third speed
And a second hydraulic cylinder 4 for switching to second speed or first speed
One of the two hydraulic cylinders 7B and 7B is extended or shortened, and the main transmission output shaft is provided via one of the first to fourth gear sets (reference numerals 48 to 51). 52 is configured to transmit power.

The auxiliary transmission 26 is provided with the transmission lever 2.
The transmission is a constant-mesh-gear transmission that is switched by the switching operation of No. 7, and is configured to further reduce the rotational power reduced by the main transmission 4 and transmit it to the rear wheel differential mechanism 53. That is, in the example of FIG. 3, when the shift lever 27 is set to the high speed H by the gears provided on the respective shafts, the rotational power is transmitted from the main shift output shaft 52, the auxiliary shift output shaft 54, and the rear wheel differential mechanism 53. Is communicated.

When the shift lever 27 is shifted to the medium speed M, the transmission is transmitted to the main transmission output shaft 52, the first transmission shaft 55, the auxiliary transmission output shaft 54, and the rear wheel differential mechanism 53. When the shift lever 27 is moved to the low speed L, the transmission is transmitted to the main transmission output shaft 52, the second transmission shaft 56, the auxiliary transmission output shaft 54, and the rear wheel differential mechanism 53. When the shift lever 27 is moved to the very low speed LL, the main transmission output shaft 52, the second transmission shaft 56, the third transmission shaft 5
7—Auxiliary transmission output shaft 54—Rear wheel differential mechanism 53 is transmitted.
It also branches to the front wheel drive shaft 58 to drive the front wheels 14,14. Reference numeral 59 denotes a hydraulic clutch for driving the front wheels, and reference numeral 60 denotes a transmission shaft that drives the PTO shaft 38.

Next, a hydraulic circuit for the forward / reverse switching device 3 and the main transmission 4 of the tractor 10 will be described with reference to FIG. The pump 65 sucks oil from the transmission case 13 which also serves as a hydraulic tank, and sends the pressure oil to a pressure reducing valve 66.
Through the main circuit 67. In the main circuit 67, a main transmission circuit 68 and a forward / reverse switching circuit 69 are sequentially branched from the upper side of the circuit, and a PTO circuit 70 is connected to the lowermost side.

The main transmission circuit 68 is provided with switching control valves 71A and 71B for supplying pressure oil to the first hydraulic cylinder 47A and the second hydraulic cylinder 47B, respectively, and is switched by a command from the controller 23. It has a configuration. The forward / reverse switching circuit 69 is provided with a lubrication circuit 7
2 and a forward circuit 73 and a reverse circuit 74 are provided on the downstream side of the circuit, and the forward clutch is provided via the proportional pressure control valves 75 and 76 on the downstream side of each of the branched circuits. 2A and the reverse hydraulic clutch 2B are connected respectively. Further, a switching valve 77 is provided in the reverse drive circuit 74, and the switching valve 77 is configured to be switched by the back pressure of the forward proportional pressure control valve 75. As a result, due to a trouble in the electric device such as the controller 23,
When the forward hydraulic clutch 2A is connected, the reverse hydraulic clutch 2B is restrained from being pressed.

A branch circuit 78 is provided between the forward proportional pressure control valve 75 and the forward hydraulic clutch 2A, and a switching control valve 7 serving as an interrupting means is provided on the lower side of the branch circuit 78. And an accumulator 8 connected thereto. The switching control valve 7 has a configuration in which an oil chamber 7a for communicating the pressure oil is located at normal times, and is switched to an oil chamber 7b for shutting off the pressure oil when the controller 23 is energized. Further, the pressure oil restricted by the accumulator 8 is configured to be released to the tank 13. Note that reference numeral 79 in the drawing denotes a stop.

On the lowermost side of the main circuit 67,
A PTO circuit 70 described later is connected and provided. As shown in FIG. 8, the pressure reducing valve 66 is attached to the inside of the axle bracket 11 below the engine 1 with bolts 64 through a flange for pipe connection. Thereby, the pressure reducing valve 66 is moved by the axle bracket 11.
Adhesion due to rotation of the front wheels 14, 14 and contact by obstacles can be prevented.

Next, the control configuration of the controller 23 which controls the speed change of the tractor 10 will be described. The controller 23 has a CPU for processing various signals, a RAM for temporarily storing the signal values, and a ROM for storing a control program. On the input side, the speed increase switch 29, the speed reduction switch 30, the forward switch 21, the reverse switch 22, and the first speed to the fourth speed for detecting the positions of the hydraulic cylinders 47A, 47B are provided on the input side. Detection switches 80 to 83 and P
A TO on / off switch 84 is provided. On the output side, a solenoid 2a of the forward proportional pressure control valve 75 is provided.
A solenoid 2b of a reverse proportional pressure control valve 2B,
Solenoid 7a of switching control valve 7 for interrupting the circuit to accumulator 8, and solenoid 85 to switching control valves 71A, 71B for sending pressure oil to hydraulic cylinders 47A, 47B.
88 and a solenoid 90a of a switching control valve 90 that switches on and off the hydraulic clutch 61 provided on the PTO transmission shaft 60.

The shift control of the tractor 10 configured as described above will be described with reference to the flowcharts shown in FIGS.
A description will be given based on the time chart shown in FIG. When the electric system of the tractor 10 is turned on, the controller 23
Are the forward / reverse switches 21 and 22 and the acceleration / deceleration switch 2
A detection value of a switch or a sensor such as 9, 30 or a connection state is read (STEP 1). Then, the shift process (S
Various processes such as STEP2), forward / reverse switching, and start process (STEP3) are sequentially performed.

The speed change process is performed by first setting the speed change switch 2
It is determined whether or not the operation of the forward / backward switch 9 and 30 has been performed. If the determination is YES, the energization of the proportional pressure control valve 75 (76) of the forward / reverse switching device 3 is stopped, and the switching of the branch circuit 78 is performed. The control valve 7 is energized to cut off the connection to the accumulator 8 (STEP2-2, STEP2-
3). Thereafter, the piston of the first hydraulic cylinder 47A or the second hydraulic cylinder 47B is actuated in response to the switch operation, thereby increasing the current shift position by one step or by 1 step.
Step down. When the position of the piston is detected by each of the shift position detection sensors 85 to 88, STEP
The energization is resumed to the proportional pressure control valve 75 (76) whose energization was stopped in 2-2. Then, the power supply to the switching control valve 7 is stopped, and the state becomes END (STEP 2-6).

At this time, as shown in FIG. 7A, when the energization is started, the pressure of the hydraulic clutch 2A (2B) rises, and the clutch connection pressure rises rapidly to reach the full pressure in a relatively short time T1. The start and forward / reverse switching process first determines whether or not the forward / reverse switching lever 19 has been operated.
When this is YES, the switching direction or the starting direction is determined (STEP3-1, STEP3-2),
If switching to forward or starting forward,
The energization of the forward proportional pressure control valve 75 that is currently energized is stopped, and the energization of the reverse proportional pressure control valve 76 is started instead. In the case of starting backward or switching to reverse, the power supply to the reverse proportional pressure control valve 76 that is currently energized is stopped, and the power supply to the forward proportional pressure control valve 75 is performed instead. Start.

As described above, when the vehicle starts moving forward or when the vehicle is switched forward, the branch circuit 78 to the accumulator 8 communicates with the accumulator 8, so that the clutch pressure is increased in the initial stage of energization as shown in FIG. It rises slowly and then rapidly (after the accumulator 8 is filled with pressurized oil)
The total pressure is reached over a time T2 longer than the time T1 described above.

Then, the above STEP 3-4 or 3-
When the processing of step 5 is completed, END is set. The shift control device of the tractor 10 configured as described above has a configuration in which the power is turned off by the forward / reverse switching device 3 when the main transmission 4 is switched. There is no need to provide a clutch, and the production cost of the tractor 10 can be reduced. Further, at the time of shifting, the connection pressure of the clutches 2A and 2B rapidly increases, and the shifting process ends in a short time. On the other hand, when the forward / reverse switching lever 19 is switched to the forward side, the clutch pressure rises more gently than at the time of the shift by the amount of the pressure oil sent to the accumulator 8, and the clutch plate on the engine side has an inertia force. As a result, it is possible to connect the rotating clutch plate as gently as possible to reduce the switching shock at the time of forward switching and starting.

FIG. 7 (C) shows the value of the current flowing to each solenoid.
The current conduction pattern is also changed to rapidly boost during gear shifting,
A configuration may be adopted in which the pressure is gradually increased at the time of starting. Further, the hydraulic circuit shown in FIG.
Branch circuits 95, 9 are respectively provided from circuits between the respective reverse clutches 2A, 2B and the proportional pressure control valves 75, 76.
6 is provided, and both branch paths are connected to one accumulator 8 'via a switching control valve 7'. When the forward movement as described above and the start of the backward movement and the switching operation are detected in addition to this, the controller 2
The switching control valve 7 'is switched by 3 and a circuit is connected to the accumulator 8' to gradually increase the clutch connection pressure. Further, at the time of gear shifting, the state where the connection to the accumulator 8 ′ is cut off without energization is maintained, and the operation of the gear shift control is quickly completed.

As a result, the hydraulic circuit configuration of the transmission can be constructed at a lower cost than when an accumulator is connected to each of the forward and reverse circuits. Next, the PTO pressure circuit 70 will be described. The main circuit 6 branched from the forward / reverse circuit 69
7 is connected to a switching control valve 90 for turning on and off the PTO, and the hydraulic clutch 61 is connected to the lower side of the circuit via a switching valve 91 for manually connecting and disconnecting this circuit. Thereby, the controller 23 and the PTO
PTO due to trouble of electrical equipment such as ON / OFF switch 84
Even when the clutch 61 remains connected, the rotational power of the PTO shaft 38 can be cut off by manual operation.

[0028] In the claims, the reference numerals of the members corresponding to the configuration of the embodiment are attached, but the reference numerals do not limit the present invention to the embodiment.

[Brief description of the drawings]

FIG. 1 is a partial hydraulic circuit of a tractor.

FIG. 2 is an overall side view of the tractor.

FIG. 3 is a diagram of a transmission mechanism of a tractor.

FIG. 4 is a block diagram showing a connection state of a controller.

FIG. 5 is a control flowchart showing an outline of a shift control.

FIG. 6A is a control flowchart showing a shift process. (B) A control flowchart showing front and rear wheel switching processing.

FIG. 7A is a time chart showing a clutch connection pressure at the time of shifting. (B) A time chart showing the clutch connection pressure at the time of start and forward switching. (C) A time chart showing the current value to the solenoid.

FIG. 8 (A) is a side view showing the mounting of the pressure reducing valve. (B) Front view of mounting the pressure reducing valve.

FIG. 9 is a hydraulic circuit diagram showing another embodiment of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2A Multi-plate clutch for forward 2B Multi-plate clutch for reverse 3 Forward / reverse switching device 4 Main transmission 14 Front wheel 15 Rear wheel 75 Proportional pressure control valve 76 Proportional pressure control valve

Claims (2)

[Claims] 1. When the rotational power of an engine 1 is transmitted to drive wheels 14 (15) via a forward / reverse switching device 3 in the form of a multi-plate clutch and a gear type transmission 4, when the gear type transmission 3 is switched, In a shift control device for a vehicle in which power transmission by the multiple disc clutch is temporarily turned off, the hydraulic pressure between the multiple disc clutch 2 of the forward / reverse switching device 3 and a control valve 75 for supplying pressure oil to the clutch 2 is set. The circuit is provided with a branch path 78 for connecting the accumulator 8 and a connecting / disconnecting means 7 for connecting / disconnecting the connection of the branch path 78, and the switching operation of the connecting / disconnecting means 7 makes it possible to change the clutch pressure increase pattern during shifting and starting. A shift control device for a vehicle, comprising: 2. The shift control device for a vehicle according to claim 1, wherein the connecting / disconnecting means disconnects the connection to the accumulator at the time of shifting and communicates at the time of starting.