JPS628179Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission in a work vehicle such as a tractor, that is, a transmission that changes according to the load during traveling or work.

Conventionally, even when tractors are running at full throttle for normal plowing work, the wheels may sink when driving in the field, or the rotary or other working equipment may plow deeper than the specified plowing depth, creating excessive resistance. As a result, the engine may be overloaded, which may cause problems such as engine stalling or overheating. To prevent this, when the engine is overloaded and the engine speed drops, manually remove the
It has been proposed to perform deceleration operation on the PTO section, but this operation is also complicated and difficult to operate accurately because it is manual.

Therefore, the present invention provides a rotational speed detection device on the main shaft connected to the engine, switches the clutch by the rotational speed detection device, and thereby automatically switches the transmission path to obtain a speed change state that immediately responds to the load. , by operating the clutch based on two limit switches operated at different rotational speeds, the switching to the high speed side is configured to be performed at a higher rotational speed than when switching to the low speed side. It is an object of the present invention to provide a transmission device for a tractor, etc., which prevents frequent gear changes and maintains a stable traveling working state.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

As shown in FIG. 1, the tractor 1 has an engine 2 mounted at the front of the body, a transmission case 3 at the rear of the body, and a clutch housing 4 connecting the two in the middle. The fuselage is supported by a front wheel 5 at the front and a rear wheel 7 connected to a running shaft 6 (see Fig. 2) inside the mission case 3 at the rear. It is connected to the PTO shaft 8 (see Figure 2) and towed and
It has a supported rotary part 11. As shown in detail in FIG. 2, in the clutch housing 4, a main shaft 13 is rotatably supported by a bearing 12, and a transmission shaft 15 is coaxially fixed to the transmission case 3 behind the main shaft 13. It is supported by bearings 17, 17 held in a holder 16. The main shaft 13 has a main clutch 18 at its front, an electromagnetic clutch 20 at its rear, and a rotational speed detecting device 21 between them. The electromagnetic clutch 20 includes a friction plate 23 connected to the main shaft 13 by a key 22, a solenoid 24 supported by the housing 4, and a driven member 25 loosely fitted to the main shaft 13. One end of the driven member 25 is connected to a high-speed gear. 25a. Rotation speed detection device 21
A weight 28 is pivotally supported by a pin on a holder 26 fixed to the main shaft 13, and a spring 30 is in contact with one end 28a of the weight.
The lever 34 includes a sleeve 31 which is biased by a sleeve 31 and a lever 34 which has one end rotatably connected to the sleeve 31 via a bearing 32 and is pivotally supported to the housing 4 by a pin 33. The other end of the lever 34 is arranged so that its actuators 36a, 37a face two limit switches 36, 37 which are arranged out of alignment.
6 and 37 are solenoid 38 as shown in FIG.
a, a normally closed switch 38b, and a self-holding switch 38c. The limit switch 36 is configured to be turned off when the lever 34 comes into contact with the actuator 36a, and turned on when the lever 34 is separated from the actuator 36a, and the limit switch 37 is turned on when the lever 34 comes into contact with the actuator 37a, and turned off when the lever 34 is separated from the actuator 37a. has been done. Furthermore, the aforementioned high-speed gear 2 is provided at the rear end of the main shaft 13.
A low speed gear 40 is spline-coupled adjacent to the transmission shaft 15, and a bearing 4 is connected to the tip of the transmission shaft 15.
1, a gear 42 is connected to the main shaft 13 by a spline so as to fit loosely into the main shaft 13. Above these, a shaft 44 is connected to the housing 4 via a holder 43.
An intermediate gear 46 with a gear 45 integrally fixed to the shaft 44 is rotatably supported.
The gear 46 meshes with the high speed gear 25a, and the gear 45 meshes with the gear 42. Both gears 45, 4
A floating gear 48 is provided between the gears 6 and 6 via a one-way clutch 47, and the gear 48 meshes with the low speed gear 40. The one-way clutch 47 operates only when the intermediate gear 46 is transmitted from the idler gear 48, and does not transmit rotation in the opposite case. These high speed gears 25a and intermediate gears 4
6, a low-speed gear 48, a one-way clutch 47, gears 45, 42, etc. constitute a gear transmission mechanism 49 which is switched between a high-speed transmission path and a low-speed transmission path by connecting and disconnecting the electromagnetic clutch 20. Further, the rear end of the transmission shaft 15 protrudes into the transmission case 3, and a gear 50 is fixed to the protrusion. The gear 50 is appropriately connected to the traveling shaft 6 and the PTO shaft 8 via a gear train within the case 3.

Since the present embodiment has the above-described configuration, when the tractor 1 is running at the rated rotation speed (2800 rpm), the weight 28 of the rotation speed detection device 21 connected to the main shaft 13 has its center of gravity. Since it is located outside the pin, it expands outward due to centrifugal force, and slides the sleeve 31 to the left in the drawing against the spring 30. As a result, the lever 34, which is only rotatably connected to the sleeve 31, is swung in the direction of the arrow (R), comes into contact with the actuator 36a of the limit switch 36, and is separated from the actuator 37a of the limit switch 37. Therefore, both switches 36 and 37 are off, and solenoid 24 of electromagnetic clutch 20 is energized. The friction plate 23 and the driven member 2 are energized by the solenoid 24.
5 is connected, and the rotation of the main shaft 13 is controlled by a high-speed gear 25a.
and is transmitted to the transmission shaft 15 via the intermediate gear 46 and gears 45 and 42. Therefore, the running shaft 6 and the PTO shaft 8 are rotating at high speed via the gear 50 of the transmission shaft 15 and the gear train inside the transmission case 3. In addition, at this time, the low speed gear 4 is
The rotation is also transmitted to the idler gear 48 via the idler gear 48, but since the intermediate gear 46 rotates at a higher speed than the idler gear 48, the one-way clutch 47 does not operate and the idler gear 48 is spinning idle. .

Now, while the tractor 1 is running, the engine 2 is overloaded due to wheels 5 and 7 sinking or the rotary part 11 plowing deeper than the predetermined plowing depth, and the rotation speed of the main shaft 13 is reduced to a predetermined high speed rotation. number N ₁
(2600 rpm), the centrifugal force acting on the weight 28 decreases, and the spring 30 causes the sleeve 31 to slide to the right. As a result, the lever 34 slides in the direction of arrow A and separates from the actuator 36a of the limit switch 36. However, since the lever 34 has not yet come into contact with the actuator 37a of the limit switch 37, the limit switch 36 is turned on, but the limit switch 37 is turned on.
is still off. Therefore, the solenoid 38a of the relay 38 is not energized and the switch 38b remains closed, so that the electromagnetic clutch 2
0 is still operating and no gear changes are made.

The load further increases, the rotation speed of the engine 2 decreases, and the rotation speed of the main shaft 13 reaches the predetermined low speed N ₂
(2200r.pm), the centrifugal force acting on the weight 28 further decreases, so the lever 3
4 further swings in the direction of arrow A. As a result, the lever 34 is activated by the actuator 37a of the limit switch 37.
, and the limit switch 37 is also turned on.
Therefore, the solenoid 38a of the relay 38 is energized, the switch 38b is opened, the power to the electromagnetic clutch 20 is cut off, and the switch 38c is energized.
The relay 38 is self-held via the . As a result, the coupling between the friction plate 23 and the driven member 25 is released, the driven member 25 becomes in a free rotation state, and the rotation of the main shaft 13 is limited to the low speed gear 40, the floating gear 48, the one-way clutch 47, the intermediate gear 46, and the gear 4.
Low speed rotation and high torque are transmitted to the power transmission shaft 15 via 5 and 42.

Next, the tractor 1 passes through a high-load area, the rotation speed of the engine 2 increases, and when the rotation speed of the main shaft 13 reaches a predetermined low speed rotation speed N ₂ (2200 rpm), the weight 28 expands due to centrifugal force, and the lever 34 in the direction of arrow B. As a result, the lever 34 separates from the actuator 37a of the limit switch 37, turning the limit switch 37 off. However, since limit switch 36 is still on, solenoid 38a in relay 38 is self-holding and switch 38b remains open.

After a while, engine 2 of tractor 1
When the rotation speed of the main shaft 13 steadily increases and the rotation speed of the main shaft 13 reaches a predetermined high speed rotation speed N ₁ (2600r.pm), the lever 34 further swings in the direction of arrow B, causing the actuator 36a of the limit switch 36 to Upon contact, the limit switch 36 is also turned off. As a result, the self-hold of the solenoid 38a is released, and the relay 38
The inner switch 38b is closed and operates the electromagnetic clutch 20 again. Therefore, the transmission path is switched and high-speed rotation is transmitted to the transmission shaft 15.

In the above embodiment, the rotation speed detection device 21 is provided directly on the main shaft 13, but it goes without saying that the rotation speed detection device 21 may be provided on a shaft connected to the main shaft 13 by a gear or the like.

As explained above, according to the present invention, even if an overload occurs and the rotational speed of the engine 2 decreases while the tractor 1 is running, the engine 2 automatically responds to this by operating the low speed switch 37. By shifting the gears to Able to maintain proper running working conditions. Also,
When the tractor 1 passes through a high-load area and returns to normal working conditions, the high-speed side switch 36 is activated to automatically switch to the low-speed side at a higher rotation speed than when switching to the low-speed side, so that the load is still relatively high. , the engine 2 speed changes before it reaches a steady state, which immediately lowers the engine speed and switches to the low speed side again, which prevents frequent gear changes. It is possible to automatically maintain a stable running working condition without any trouble.

[Brief explanation of the drawing]

Fig. 1 is an overall side view showing a tractor to which the present invention can be applied, Fig. 2 is a diagram showing a transmission device according to the present invention, Fig. 3 is an electric circuit diagram thereof, and Fig. 4 is a diagram showing a switch and an electromagnetic clutch according to the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Tractor, 2... Engine, 13... Main shaft, 20... (Electromagnetic) clutch, 21... Rotation speed detection device, 36... High speed side switch, 37... Low speed side switch, 38... Relay, 46...Intermediate gear, 47...One-way clutch, 48...Idle gear, 49...Gear transmission mechanism, _N1 ...Predetermined high speed rotation speed, _N2 ...Predetermined low speed rotation speed.

Claims (1)

[Scope of utility model registration request] A main shaft connected to the engine, a rotation speed detection device and a clutch installed on the main shaft, a gear transmission mechanism that is switched between a high-speed transmission path and a low-speed transmission path by connecting and disconnecting the clutch, and the rotation speed detection device. It consists of two switches, one on the low speed side and one on the high speed side, which operate at different set rotation speeds, and when switching the gear transmission mechanism from the high speed transmission path to the low speed transmission path, the switch operates on the low speed side at a predetermined low speed of the main shaft. When operating a switch to change the clutch and switching the gear transmission mechanism from a low-speed transmission path to a high-speed transmission path, the high-speed side switch is operated at a predetermined high-speed rotation speed that is higher than the predetermined low-speed rotation speed of the main shaft. A transmission device for a tractor or the like configured to switch the clutch.