JPH0798457B2 - Hydraulic circuit for switching drive of four-wheel drive type vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a traveling switching hydraulic circuit for a four-wheel drive traveling vehicle such as a tractor to which a front loader and a rotary cultivator can be mounted.

(Prior Art) For example, in a four-wheel drive type agricultural tractor, when a front loader is mounted, forward and reverse movements are frequently changed, and high speed reverse movement is required, so that a traveling power transmission system is provided with a forward and reverse movement switching device. In addition, when a rotary cultivator is installed, high work performance in the field is required. Therefore, a front wheel speed switching device that increases the front wheel peripheral speed to be smaller than the rear wheel and reduces the turning radius is provided.

A wet clutch of each of the switching devices is provided, and forward and backward and high and low speeds are switched by the operation of the hydraulic clutch, and those hydraulic circuits have their own hydraulic pumps, or for power steering or work. Whether it is connected in series to a hydraulic circuit for raising or lowering the machine or for attitude control.

(Problems to be solved by the invention) However, when the former unique pump is provided, the cost is increased, and the latter is not expensive, but the front wheel speed switching device should be used simultaneously with power steering or work machine operation. If a shunt valve is installed and oil is shunted, the flow rate on the mainstream side may decrease when the engine rotates at low speed, resulting in insufficient pressure, resulting in a decrease in operating speed or inoperability. Or a pressure reducing valve needs to be provided because the operating pressure is different, so that the pump pressure may change, heat may be generated, horsepower may be lost, and the like.

By the way, the forward-reverse switching device and the front wheel speed switching device are rarely used at the same time, that is, since it is dangerous to make a sharp turn during the work of the front loader, the front wheel speed switching device is not used and the rotary work device is not used. Since there is almost no need to go backward, the forward / reverse switching device is not used, and
The circuit pressures of both devices are set to be substantially equal.

Therefore, the present invention is a four-wheel drive system in which the hydraulic circuit of the front wheel speed switching device is connected in series to the relief valve discharge side of the hydraulic circuit of the forward / reverse switching device to enable cost reduction and normal operation of each device. An object of the present invention is to provide a traveling switching hydraulic circuit for a model traveling vehicle.

(Means for Solving the Problem) A specific structure for solving the problem in the present invention is a forward / reverse switching for switching between forward and reverse between the engine 1 and a transmission such as a main transmission in a traveling power transmission system. A device 18 and a front wheel speed switching device 14 that switches the drive speed of the front wheels 8 between the transmission and the front wheels 8 are provided.
18 is equipped with a hydraulic clutch AC for switching between forward and reverse, and a front wheel speed switching device
14 are provided with front wheel speed switching hydraulic clutches BC respectively, and a relief valve 53 is provided on the hydraulic pump 52 side of the hydraulic circuit A for controlling the forward / reverse switching hydraulic clutch AC, and the front wheel speed switching is provided on the discharge side of the relief valve 53. The hydraulic circuit B for controlling the hydraulic clutch for use BC is connected in series.

(Operation) The pressure oil from the hydraulic pump 52 is sent to the forward / reverse switching device 18 via the switching valve A1 of the forward / backward switching hydraulic circuit A, and the hydraulic clutch AC is normally or reversely operated to change the traveling power to the forward power or the forward power. It is used as reverse power and transmitted to the rear. This hydraulic clutch for switching between forward and reverse
When AC is in the forward direction, the pressure oil flows through the relief valve 53 to the lubricating oil passage 31, and pressure is also established in the front wheel speed switching hydraulic circuit B connected in series to this, and the on / off valve B2 and the front wheel are connected. When the speed switching valve B1 is operated, it is sent to the hydraulic clutch BC, and the hydraulic clutch BC is activated without time loss,
The front wheels 8 are changed from substantially the same peripheral speed as the rear wheels 6 to about double speed.

This front wheel speed switching hydraulic clutch BC is not operated at the same time as the forward / reverse switching hydraulic clutch AC.
There is no problem even if it is connected in series from 52.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 2 shows a traveling power transmission system of a four-wheel drive type tractor to which a front loader, a rotary tiller and the like can be mounted,
The power of the engine 1 is transmitted to the transmission 3 via the main clutch 2.

The transmission 3 includes a forward / reverse switching device 18, which will be described later, as a main transmission,
A rear wheel drive system in which power is transmitted from a bevel pinion shaft 4 which is an output shaft thereof to a rear wheel 6 via a rear wheel differential device 5 , A front wheel drive system in which power is transmitted to the front wheels 8 via the transmission gear 7 is branched.

The power of the front wheel drive system is transmitted from the transmission gear 7 to the first transmission shaft 10 via the gear 9, and is transmitted from the first transmission shaft 10 to the second transmission shaft 12 via the two-wheel / four-wheel switching clutch 11. It A front wheel propulsion shaft 13 is provided in parallel with the second transmission shaft 12, and a front end speed switching device 14 is provided between the two shafts 12, 13.

The front wheel propulsion shaft 13 drives a front wheel differential device 16 via a bevel pinion 15, and a front wheel 8 via a front wheel final reduction mechanism 17.
Transmit power to.

1 and 2, the forward / reverse switching device 18, the front wheel speed switching device 14 and their hydraulic circuits A and B are shown.

The forward / backward switching device 18 is housed in a transmission case 22, and a forward drive pinion 24 and a reverse drive pinion 25 are fixed to a cylindrical propulsion shaft 23 to which power is transmitted from the main clutch 2.
A forward gear 27 and a reverse gear 28 are loosely fitted on the counter shaft 26, and power can be transmitted between the reverse pinion 25 and the gear 28 via a back idler gear (not shown). Therefore,
Transmissions such as a main transmission, an auxiliary transmission, and a super speed reducer are located rearward of the forward / reverse switching device 18 in the traveling power transmission direction, and the forward / reverse switching device 18 is provided between the engine 1 and the main transmission. Has been.

Forward / reverse gears 27 and 28 are alternatively provided on the counter shaft 26 as the shaft 2
A forward / reverse switching hydraulic clutch AC fixed to 6 is provided, and the counter shaft 26 is provided with a forward oil passage 29, a reverse oil passage 30 and a lubricating oil passage 31 for supplying pressure oil to the hydraulic clutch AC. There is.

The front wheel speed switching device 14 is arranged in the lower front portion of the mission case 22 and can be retrofitted from the outside. The front wheel 12a of the second transmission shaft 12 is divided into two parts and the front wheel propulsion shaft 13 is also divided into two parts. It has a rear shaft 13a.

A transmission case 33 is detachably attached to the front lower abdomen of the transmission case 22. The transmission case 33 supports the rear shaft 13a so as to project forward, and a bearing portion 34 projecting into the transmission case 22 is integrally formed. The front shaft 12a is rotatably supported by 34. Reference numeral 35 denotes a bottom lid of the transmission case 33.

Large and small pinions 36 and 37 are fixed to the front shaft 12a, and the rear shaft 13a
The large and small pinions 36 and 37, the constant speed constant gear 38 and the double speed gear 3
9, and a wet front wheel speed switching clutch BC is provided between the gears 38, 39.

The hydraulic clutch BC is a piston 412 that presses the clutch plate 40.
The shift gear 43 is connected to the rear shaft via a connecting rod 42.
When the supply oil passage 44 formed in 13a is not pressurized, the shift gear 43 meshes with the constant velocity gear 38, and the constant velocity gear 38
Is connected to the rear shaft 13a, and the rotation at which the peripheral speed becomes substantially the same as that of the rear wheel 6 is transmitted to the front wheel 8 and when pressure is applied to the oil supply passage 44, the piston 41
Is moved against the spring 45, the clutch plate 40 is pressed to connect the double speed gear 39 to the rear shaft 13a, and the front wheel 8 is transmitted with a rotation that is approximately twice the rear wheel 6 or a high peripheral speed before and after the rear wheel 6. To do.

The front wheel speed switching device 14 is assembled in advance so that it can be installed as an option, and is inserted into the cassette case from below the mission case 22, and a hand is put through an inspection window of the mission case 22 to set the second transmission shaft 12 The coupling 46 is moved to connect the front shaft 12a so as to be integrally rotatable.

This front wheel speed switching device 14 is unitized like a conventional front wheel drive transmission device having only one pair of gears,
It can be adopted selectively and can be adopted as a Dera option.

However, the mission case 22 can be divided into front and rear, and after the transmissions have been installed in each,
Before assembling 22, attach the front wheel speed switching device 14,
The front and rear of the second transmission shaft 12 may be connected by a coupling 46.

The leaf valve 53 of the hydraulic circuit A of the forward / reverse switching hydraulic clutch AC and the hydraulic circuit B of the front wheel speed switching hydraulic clutch BC are connected in series. That is, a lubricating oil passage 31 is formed by branching on the hydraulic pump 52 side of the hydraulic circuit A, a relief valve 53 is provided in the lubricating oil passage 31, and a hydraulic circuit B is connected to the discharge side of the relief valve 53. There is.

The hydraulic pump 52 is driven by the engine 1 and is supplied with oil from the hydraulic pump 52.
A forward / reverse switching valve A1, an inching valve A2, a modulating valve mechanism A3, and the like are incorporated in this.

Then, the pressure oil is supplied to the forward oil passage 29 or the backward oil passage 30 via the inching valve A2 by manually switching the forward / reverse switching valve A1, and the oil passage is operated by stepping on the inching valve A2. Quickly connect the oil sent to 29,30.

The modulating valve mechanism A3 is a relief valve provided in the lubricating oil passage 31 that is connected in parallel to the switching valve A1.
53, a cylinder 54 that adjusts the operating pressure of the relief valve 53, and a throttle portion 56 and a check portion 57 that are provided in an operation oil passage 55 that connects the cylinder 54 and the switching valve A1. .

When the switching valve A1 is in the neutral position, the modulating valve mechanism A3 supplies the pressure oil from the hydraulic pump 52 with low oil pressure to the hydraulic clutch AC as lubricating oil, and the switching valve A1 switches to the forward position or the reverse position. When the relief valve
The operating pressure of 53 is gradually increased from low pressure to high pressure, and the oil pressure of the oil supplied to the hydraulic clutch AC is increased to smoothly shift from the half-clutch state to the full-clutch state, and the traveling vehicle moves forward or backward. While in relief, the relief valve 53 is maintained at a high pressure to prevent the hydraulic clutch from slipping.

The front wheel speed switching hydraulic circuit B is connected in series to the discharge side of the relief valve 53, and has an input valve B2 and a front wheel speed switching valve B1 in series. The on / off valve B2 is manually operated, while the switching valve B1 is automatically operated by the steering operation member 59. Switching valve
B1 is connected to the supply oil passage 44 via the oil passage 61.

That is, the cam member 60 is attached to the steering operation member 59, for example, the pitman arm, and when the pitman arm is swung to steer the front wheels 8 to the left and right by about 35 °, the cam member 60 operates the switching valve B1. Then, the pressure oil is supplied to the hydraulic clutch BC.

Since the front wheel speed switching hydraulic circuit B is in series with the relief valve 53, the oil of the pressure set by the relief valve 53,
That is, the oil used to lubricate the hydraulic clutch AC is supplied, and a constant pressure is always maintained while the traveling vehicle is moving forward or backward, and if the on / off valve B2 is turned on, a sharp turn will occur. Sometimes the front wheel speed switching valve B1 operates and the hydraulic clutch BC operates without time loss.

In addition, when operating the forward / reverse switching valve A1,
Since B1 is not used, there is no problem even if pressure does not rise in the hydraulic circuit B, and even if the front wheel speed switching valve B1 is operated, the hydraulic circuit A does not cause a pressure drop. Therefore, the hydraulic circuit A does not require a pressure guarantee accumulator, a check valve, or the like.
Further, the hydraulic circuit A may be provided with only the relief valve 53 instead of the modulating mechanism A3. Further, when a relief valve is provided in the hydraulic circuit A other than the lubricating oil passage 31, the relief valve is provided to the hydraulic circuit B.
May be connected in series.

(Effects of the Invention) According to the present invention described in detail above, the relief valve 53 is provided on the hydraulic pump 52 side of the hydraulic circuit A that controls the forward / reverse switching hydraulic clutch AC, and the front wheel speed is provided on the discharge side of the relief valve 53. Since the hydraulic circuit B for controlling the switching hydraulic clutch BC is connected in series, the front wheel speed switching hydraulic clutch BC is always operated by using the discharge pressure of the relief valve 53 when the hydraulic circuit A is under pressure. The hydraulic circuit A does not cause a pressure drop even if it is operated, and there is no need for an accumulator or a check valve for ensuring the pressure.
Since AC and BC are not switched at the same time, they can be connected in series and do not require a shunt valve.There are few hydraulic pumps and valves, and piping is simplified, so heat generation, horsepower loss, etc. It can be manufactured easily and inexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing an embodiment of the present invention, and FIG. 2 is a diagram showing a traveling power transmission system of a four-wheel drive type traveling vehicle. 14 …… front wheel speed switching device, 18 …… forward / reverse switching device, 29…
… Forward oil passage, 30 …… Reverse oil passage, 31 …… Lubricating oil passage, 53 ……
Relief valve, A ... hydraulic circuit for switching between forward and reverse, B ...
Front wheel speed switching hydraulic circuit, AC, BC ... Hydraulic clutch, A1
…… Forward / reverse switching valve, B1 …… Front wheel speed switching valve.

Claims (1)

[Claims] 1. A traveling power transmission system, a forward / reverse switching device (18) for switching between forward and reverse between the engine (1) and a transmission such as a main transmission, and the transmission and front wheels (8). And a front wheel speed switching device (14) for switching the driving speed of the front wheels (8) between the front wheel and the rear wheel, and a forward / reverse switching hydraulic clutch (AC) and a front wheel speed switching device. A front wheel speed switching hydraulic clutch (BC) is provided in (14), and a relief valve (53) is provided on the hydraulic pump (52) side of the hydraulic circuit (A) that controls the forward-reverse switching hydraulic clutch (AC). A hydraulic circuit (B) for controlling a hydraulic clutch (BC) for switching the front wheel speed is connected in series to the discharge side of the relief valve (53), which is a hydraulic circuit for switching travel of a four-wheel drive type vehicle.