JPS6231737Y2 - - Google Patents

Description

[Detailed description of the invention] This invention installs a wet multi-disc brake for vehicle braking on the outer surface of a transmission case housing a hydraulic clutch-type vehicle speed change device, and also supplies oil to the hydraulic clutch in the vehicle speed change device. This invention relates to a cooling device for cooling the above-mentioned wet multi-disc brake in a traveling working vehicle which is equipped with an inching valve in the circuit for selectively reducing the hydraulic pressure applied to the hydraulic clutch with variable pressure reduction degree. be.

The above-mentioned inching valve is for selectively driving the vehicle at low speed or stopping it.
By operating this inching valve and reducing the clutch action hydraulic pressure, slip operation of the hydraulic clutch in the vehicle speed change system and an increase in the slip ratio are achieved, allowing the vehicle to run at a low speed and decelerate within the low speed range. In this case, the vehicle can be stopped by reducing the pressure to a low oil pressure at which the hydraulic clutch is disengaged.

In addition, in order to drive the vehicle at low speeds, the wet multi-disc brake described above is operated in a slip state, and in this case, in order to prevent the engine from stalling due to the excessive load applied to the engine due to brake operation, the inching valve is It is often done to control the vehicle at low speed while avoiding excessive engine load by simultaneously operating the hydraulic clutch and slipping the hydraulic clutch, especially when the vehicle is repeatedly moving forward and backward.

Wet multi-disc brakes require sufficient cooling, especially when they are operated in slip conditions. However, in the past, the brake case of a wet multi-disc brake contained cooling oil that also served as lubricating oil up to a certain level, or the wet multi-disc brake was placed as low as possible on the outer surface of the transmission case and The wet multi-disc brakes were cooled by communicating the oil below the oil level in the transmission case, so the cooling oil was not replaced at all or was rarely replaced, resulting in insufficient cooling of the wet multi-disc brakes. Therefore, prevention of seizure and wear of the friction plates was insufficient.

The purpose of this invention is to provide a novel cooling device for a wet multi-disc brake in a traveling work vehicle of the type mentioned at the beginning, which eliminates the above-mentioned problems by using the above-mentioned inching valve. It is in.

This invention will be described in detail below with reference to the illustrated embodiments.

Figures 1 and 2 show a mission case 1 of a traveling work vehicle equipped with an embodiment of this invention, which is divided into two parts: a wide case part 1A and a narrow case part 1B. The transmission case 1 is equipped with an oil passage plate 2 having a function described later on its outer surface on the part 1B side, and includes an input shaft 3, two power shift shafts 4F and 4R, an intermediate shaft 5, and a gear shift shaft 6. Output shaft 7
It is equipped with. Inside the transmission case 1, a hydraulic clutch type main transmission 8 located at the front stage and a gear shift type auxiliary transmission 9 located at the rear stage are connected in series to each other as a vehicle speed change device. .

As shown in FIGS. 1 and 3, the main transmission 8 has gears 10 on each power shift shaft 4F, 4R.
These gears 10F and 10R are loosely installed.
10R and engage each other, the power shift shaft 4
The gear 10F on F meshes with the gear 11 attached to the input shaft 3, and each power shift shaft 4F, 4R
The gears 12F and 12R fitted on the shafts mesh with the gear 13 fitted on the intermediate shaft 5, and the gears 10F and 10F on the shafts 4F and 4R are arranged on each power shift shaft 4F and 4R.
Multi-plate hydraulic clutch 14F, 1 for selectively coupling 10R to power shift shaft 4F, 4R
It is configured with 4R. As described above, when the hydraulic clutch 14F is activated and the gear 10F is coupled to the power shift shaft 4F, the hydraulic clutch type main transmission 8 decelerates and transmits the rotation of the input shaft 3 to the intermediate shaft 5 in the forward direction of the vehicle. death,
Also, the hydraulic clutch 14R is operated and the gear 1
When 0R is coupled to the power shift shaft 4R, the rotation of the input shaft 3 is transmitted to the intermediate shaft 5 at a reduced speed in the direction of backward movement of the vehicle.

The gear transmission shaft 6 is rotated by the intermediate shaft 5 through the sub-transmission device 9 for changing speeds, and the small gear 15 thereon is
By meshing with the large gear 16 on the output shaft 7, the output shaft 7 is constantly connected to the output shaft 7, and the output shaft 7 is connected in the direction of the driving wheels of the vehicle. A wet multi-plate brake 17 for braking the vehicle is installed on the outer surface of the transmission case 1 on the above-mentioned gear shift shaft 6 and on the oil passage plate 2 in the illustrated case.
As shown in FIG. 1, this wet multi-plate brake 17 includes a friction plate for forward braking and a mating plate group 19 in a brake case 18 attached to the oil passage plate 2.
F, a friction plate for reverse braking, and a mating plate group 19R on the gear shift shaft 6, and each of these groups 19F, 19R.
The friction plates are provided so as to be slidably supported on the gear shift shaft 6, and both friction plates and the mating plate groups 19F and 19R are provided.
A pair of pressure plates 20F and 20R are in between.
It has a well-known structure in which a ball 21 is housed in a cam groove and interposed therebetween. An operating shaft 22 is rotatably supported in the brake case 18, and a link mechanism 2 is connected between the operating shaft 22 and the pressure plates 20F and 20R.
3, and when the operating shaft 22 is rotationally displaced, both pressure plates 20F, 20R are rotationally displaced, and as a result, both pressure plates 20F, 20R are caused by the ball 21 climbing up to the cam slope. are displaced in a direction away from each other against the force of the return spring 24. The wet multi-disc brake 17 is connected to the gear shift shaft 6
When the vehicle is moving forward, the friction plate and the mating plate group 19F are placed on the inner surface of the brake case 18 by the pressure plate 20F, and when the vehicle is moving backward, the friction plate and the mating plate group 19R are placed on the inner surface of the brake case 18 by the pressure plate 20R. By being pressed against the inner surface, the gear change shaft 6 is braked, thereby braking the vehicle.

Next, FIG. 4 shows a mechanism for supplying and discharging hydraulic pressure to the hydraulic clutches 14F, 14R in the main transmission 8. Hydraulic oil is supplied to the hydraulic clutches 14F, 14R from inside the transmission case 1, which also serves as an oil tank 25. This is carried out by a hydraulic pump 26, which is installed on the outer surface of the oil passage plate 2 with a pump shaft 26a connected to the input shaft 3, as shown in FIGS. This hydraulic pump 2
6 is connected by an oil supply circuit 28 to the primary side of a directional control valve 27 that controls the supply and discharge of hydraulic pressure to and from the hydraulic clutches 14F and 14R. A primary pressure regulating valve 30 for setting the clutch working pressure and a secondary pressure regulating valve 31 for setting the lubricating pressure are inserted in this order into a branch circuit 29 branched from the oil supply circuit 28. A lubricating oil supply circuit 32 for lubricating the friction element portions _Lc of the hydraulic clutches 14F and 14R is led out from the branch circuit 29 between them. The following inching valve 34 is inserted and installed on the rear stage side.

That is, to explain the same inching valve 34 with reference to FIGS. 5-8, the valve case 35 of the inching valve 34 has a cylindrical valve body 36 having a partition wall 36a in the middle part, a load piston 37, and a pair of compression pistons between them. It is fitted with springs 38 and 39 interposed therebetween. The load piston 37 is formed to have a through hole on the axis, and the operating shaft 40 fitted in the through hole is connected to the lid 3 of the valve case 35.
5a rotatably supported, and this operating shaft 40
A lever 41 is attached outside the valve case 35. A slot 4 along the axial direction is formed on the circumferential surface of the operating shaft 40.
0a is formed, and a pin 42 supported by the load piston 37 faces the slot 40a, so that the load piston 37 cannot rotate relative to the operating shaft 40 but can freely slide within the range of the slot 40a. It is connected to.

Now, if the opposite side of the lever 41 is the front side when viewed in the valve axis direction, an annular slot 36b is formed on the outer circumferential surface of the valve body 36 over an appropriate width in the front-rear direction, and this slot 36b is always kept in place. A pump port 43P ₁ connected to the hydraulic pump 26 is formed in the valve case 35 at a facing position. Further, the hydraulic clutches 14F, 1 are connected via the directional control valve 27.
The clutch port 43C connected to the valve case 4R is located in the valve case 35, facing the slot 36b in a state where the valve body 36 is maximally displaced forward in the opposite direction to the load piston 37, as shown in FIG. It is arranged and formed as follows. The valve case 35 further includes a pump port 43P ₂ equipped with a throttle 44 that communicates with the back of the load piston 37 at all times, a drain port 43T 1 located in front of the pump port 43P ₂ by an appropriate amount, and a fifth drain port 43T ₁ . As shown in the figure, when the load piston 37 is retracted, it is opened and oil is drained from the valve case 35 between the valve body 36 and the load piston 37, but as shown in Figure 6, the load piston 37 is held constant. The drain port 43T ₂ is blocked by the load piston 37 when it is advanced beyond the amount, and the other two drain ports 43T ₃ ,
43T ₄ is formed.

On the other hand, throttle oil passages 45 and 46 are provided between the peripheral wall of the valve body 36 and the partition wall 36a, and the clutch port 43C is always connected to the valve case 35 between the valve body 36 and the load piston 37 through the oil passages 45 and 46. They are formed so that they can communicate with each other. Further, on the outer circumferential surface of the load piston 37, there is a cutout groove 47 having a shape shown in FIG. A notch groove 47 is formed. The load piston 37 is formed with a small diameter at its front end, and the drain port _43T3 is used to drain leaked oil from inside the valve case 35 at the outer periphery of the small diameter front end. Further, a load pin 48 for vibration prevention is fitted into the front end of the valve body 36 and the base end contacts the lid 35b of the valve case 35, and the drain port _43T4 is connected to the valve case 35 on the base end side of the load pin 48. It is said to be used to drain leaked oil from inside. Furthermore, the compression spring 3
8 and 39 are received by the load piston 37 via a spring bearing ring 49, and of these two compression springs 38 and 39, the compression spring 38 on the inner peripheral side is the fifth one.
The free length of the load piston 37 is set so that it has some slack in the fully retracted state shown in the figure.

Based on the structure described above, the inching valve 34 functions as follows. That is, first, the longitudinal position of the load piston 37 is changed according to the operating position of the lever 41. This is because when the lever 41 is operated and the load piston 37 is rotationally displaced via the operating shaft 40, the position of the notch groove 47 is changed in the circumferential direction of the piston 37, so that the pump port _43P2 acts on the back of the load piston 37. The load piston 37 is moved forward or backward by the action of the hydraulic pressure or the compression spring 39, and the inside of the valve case 35 behind the load piston 37 is brought into communication with the drain port _43T1 via the notch groove 47. The load piston 37 is stopped at this position, and the longitudinal position of the load piston 37 is ultimately determined by the operating position of the lever 41. By displacing the load piston 37 back and forth, the spring loads of the compression springs 38 and 39 are changed, and the load piston 37 is moved to a position where it blocks the drain port _43T2 as shown in FIG. In the state where it is moved forward to the point where it is moved forward, oil is not drained from the drain port _43T2 .

Now, looking at the state where the drain port _43T2 is not blocked by the load piston 37, the valve body 36 and the load piston 37
The hydraulic pressure inside the valve case 35 between the two, and therefore the hydraulic pressure that urges the valve body 36 in the forward direction, is connected to the drain port 4.
This is not true because the oil is drained from _3T2 , and on the other hand, the hydraulic pressure that acts on the front surface of the valve body 36 and urges the valve body 36 in the backward direction is
Although oil is drained from the front side to the back side, this is true because the oil drain is through the throttle oil passage 46. Therefore, the valve body 36 is urged forward by the compression springs 38 and 39.
Since oil is drained from the clutch port 43C via the throttle oil passages 45 and 46, the large diameter end 49 of the front end of the slot 36b vibrates back and forth.
While connecting the pump port 43P ₁ and the clutch port 43C intermittently, the hydraulic pressure corresponding to the spring loads of the compression springs 38 and 39 at that time is applied to the clutch port 43C.
It will be established. and compression spring 38,
39 is a hydraulic pressure (hydraulic pressure shown in FIG. 8) that is lower than the hydraulic pressure set by the primary pressure regulating valve 30 (hydraulic pressure P ₃ shown in FIG. 8) even when the drain port 43T ₂ is compressed to the maximum in a non-blocking state. ₂ ) is established at the clutch port 43C, and from the above, when the drain port _43T2 is in a non-blocking state, the hydraulic pressure set by the primary pressure regulating valve 30 is reduced by the inching valve 34, and each hydraulic clutch 14F , 14R.

When the lever 41 is fully operated in the forward direction of the load piston 37, the drain port _43T2 is blocked as shown in FIG. 6, and oil is not drained from behind the valve body 36. The hydraulic pressure acting on the front side of the valve body 36 and the hydraulic pressure acting on the rear side become equal, so that the valve body 36 assumes a position in which it is moved forward to the maximum extent by the force of the compression spring 39, as shown in FIG. , the pump port _43P1 and the clutch port 43C are communicated with each other without being restricted.
The hydraulic pressure _P1 acts directly on the clutch port 43C, and as a result, the hydraulic pressure set by the primary pressure regulating valve 30 is directly applied to each hydraulic clutch 14F, 14R.

FIG. 8 shows the relationship between the position D of the load piston 37 in the inching valve 34 and the clutch working oil pressure P. Regarding the position D of the load piston, the most retracted position shown in FIG. 5 is zero, and the position shown in FIG. The most advanced position is _D2 . At the most advanced position _D2 of the load piston 37, the oil pressure P
becomes the regular oil pressure _P3 set by the primary pressure regulating valve 30. While the load piston 37 is in the retracted position, the springs 38 and 39 at that time
A hydraulic pressure P lower than the normal hydraulic pressure _P3 is established depending on the load, and such a low hydraulic pressure can be changed by changing the operating position of the lever 41. In FIG. 8, P ₀ , which is established when position D is zero, corresponds to the initial spring load of the compression spring 39, and as position D increases from oil pressure P ₁ at position D ₁ , the rise of oil pressure P becomes steeper. This is because the compression spring 38 is between the positions D ₁ and D ₂ .
It is also shown that P is also involved in establishing the oil pressure P.

As shown in FIG. 4, the inching valve 34 described above has a lever 41 connected to a pedal 50 for operating the wet multi-disc brake 17.
It is supposed to be operated at the same time as the brake 17. That is, the brake lever 51 attached to the end of the operating shaft 22 shown in FIGS. 1 and 2 and the lever 41 of the inching valve 34 are connected to the common pedal 5.
It is linked and connected to 0. When the inching valve 34 is not depressed, the lever 41 assumes an operation position that advances the load piston 37 of the inching valve 34 to the maximum extent as shown in FIG. 6, and the pedal 50 is depressed. and the lever 41 is rotated in the direction of the position for retracting the load piston 37.
It is provided.

Based on the above, when the pedal 50 is depressed to a certain level or more, the hydraulic pressure shown in FIG.
By applying a controlled low oil pressure lower than P ₂ to each hydraulic clutch 14F, 14R, each hydraulic clutch 1
It is possible to slip the 4F and 14R, and when the pedal 50 is fully depressed, the wet multi-disc brake 17 transfers to the gear shift shaft 6, thereby completely braking the vehicle, and at the same time the load piston 37 of the inching valve 34 moves to the final position. By retracting, the hydraulic clutch 14F or 14R, which had been operating up until then, is designed to be in a disengaged state.

Therefore, the pedal 50 can be adjusted as necessary while the vehicle is running.
By stepping on the wet type multi-disc brake 17, the wet type multi-disc brake 17 is operated in a slip manner, and at the same time, the hydraulic clutch 14F or 14R, which is in the operating state, is operated in a slip manner. The system is designed to increase the slip rate of 14F or 14R, thereby controlling the vehicle's low-speed running, and to effectively cool the wet multi-disc brake 17 by using the inching valve 34. The following measures have been taken.

That is, as shown in FIG. 2, the flow sensing valve 33 is mounted on the outer surface of the oil passage plate 2 at a position above the wet multi-disc brake 17.
The inching valve 34 is the same flow sensing valve 34.
By fixing the valve case 35 on the outer surface of the lower half of 3 with the fixture 52, the wet multi-disc brake 17
The transmission case 1 is mounted on the outer surface of the transmission case 1 at a position directly above the transmission case 1. As shown in FIG. 5, each port 43P ₁ , 43P ₂ , 43C, 43T ₁ , 43T ₂ , 4 of the inching valve
3T ₃ and 43T ₄ are communicated with an oil passage formed in the valve case 53 of the flow sensing valve 33, but among the above-mentioned ports, three adjacent drain ports 43T ₁ , 43T ₂ , 43T ₃
is communicated with a common oil passage 54 of the valve case 53 of the flow sensing valve 33. Then, such an oil passage 54 is connected to the transmission case 1.
The latter oil passage 55 is connected to the oil passage 55 shown in FIG. It is opened to the target position. Furthermore, as shown in Figure 1,
The oil passages 56, 57, 58 that communicate the inside of the brake case 18 and the inside of the transmission case 1 are connected to the wall of the brake case 18, the oil passage plate 2, and the wall of the case part 1B, and the oil passage 56 on the wall of the brake case 18 is connected to the inside of the case 18. It opens into the brake case 18 at a level a suitable amount H above the inner bottom surface of the case part 1B.
The oil passage 58 in the wall is opened into the mission case 1 above the oil level OL inside the mission case 1.

As described above, the oil drained from the drain ports 43T ₁ , 43T ₂ , 43T ₃ of the inching valve 34 is applied to the friction plates and the mating plate group of the wet multi-disc brake 17 indicated by the symbol L _b in the circuit diagram of FIG. 19F,1
After cooling 9R, it is returned into the transmission case 1, which is the oil tank 25.

The primary pressure regulating valve 30 shown in FIG. 4 is configured as a hydraulic pressure gradually increasing type relief valve known from, for example, Japanese Utility Model Application Publication No. 52-98051, etc., and is connected to the oil supply circuit 28 on the secondary side of the inching valve 34. A back pressure circuit 59 for the primary pressure regulating valve 30 is led out from the back pressure circuit 59, and a throttle 60 for gradually increasing the oil pressure is inserted into the back pressure circuit 59. The directional control valve 27 is connected to both hydraulic clutches 14F and 14F, as usual.
The flow sensing valve 33 has the following functions: a neutral position N in which the hydraulic clutch 14R is inactive, and a forward position F and a reverse position R in which each hydraulic clutch 14, 14R is selectively activated. ing. That is, the flow sensing valve 33
A first position I in which the drain circuit 61 connected to the oil tank 25 is connected to the primary pressure regulating valve 30 side of the throttle 60 in the back pressure action circuit 59 is brought into conduction, and a second position I in which the drain circuit 61 is blocked. position, and the refueling circuit 2 only in the first position.
8, and is biased toward the first position by the hydraulic pressure on the primary side, and biased toward the second position by the hydraulic pressure on the secondary side and a weak spring 33b. There is. The displacement force of the spring 33b is set smaller than the displacement force caused by the initial pressure of the primary pressure regulating valve 30. Therefore, when the directional control valve 27 is moved from the forward position F or the reverse position R to the neutral position N and the hydraulic pressure on the secondary side of the flow sensing valve 33 is released, the valve 33 is moved to the first position. The oil is rapidly drained from behind the primary pressure regulating valve 30.
When the direction switching valve 27 is moved from the neutral position N to the forward position F or the reverse position R, the primary pressure regulating valve 3
0, the oil pressure is gradually increased and the oil pressure on the secondary side of the flow sensing valve 33 is also increased, so when the displacement force due to the oil pressure on the secondary side and the load of the spring 33b overcomes the oil pressure on the primary side. The flow sensing valve 33 is moved to the second position. Then, the directional control valve 27 is in the forward position F.
Alternatively, from the time when the flow sensing valve 33 is moved to the reverse position R until the flow sensing valve 33 is moved to the second position, the hydraulic clutch 14 is
Oil is gradually supplied to F or 14R, and the back pressure to the primary pressure regulating valve 30 is double throttle 33a, 6.
0, the engagement of the hydraulic clutch 14F or 14R progresses gradually, and at the end of the clutch engagement process, the flow sensing valve 33 is moved to the second position, so that the hydraulic clutch 14F or 14R is engaged. The engagement of 14R is completed rapidly. As described above, the flow sensing valve 33 is connected to the directional control valve 2.
7 is moved to the neutral position N, the oil is rapidly drained from behind the primary pressure regulating valve 30, and in the initial stage when the directional control valve 27 is moved to the forward position F or reverse position R and clutch engagement is performed. It is said to be equipped with a function to delay the progress of the engagement.

The directional switching valve 27 is built into the top wall of the case portion 1A of the mission case 1 at the position shown in FIG. A secondary pressure regulating valve 31 is also provided.
Although not shown, it is built into the wall of the mission case 1. The oil passage plate 2 forms an oil passage connecting the valves 27, 30, 31, 33, 34, the hydraulic pump 26, and the ends of the power shift shafts 4F and 4R with the case half 1B. It has been and is functional.

As shown in FIG. 1, the above-described sub-transmission device 9 has
The gears 63, 64, 65 loosely fitted on the intermediate shaft 5 and the gears 67, 68, 69 fitted on the gear change shaft 6 are meshed with each other, and the gears 63, 64, 65 are fitted on the intermediate shaft 5. Shift gears 71, 72, and 73 that can mesh with the inner teeth of the gears are provided to perform three-stage gear shifting.

Since the illustrated cooling device for the wet multi-disc brake 17 according to this invention is constructed as described above, the drain port 43 of the inching valve 34
The oil drained from T ₁ , 43T ₂ , and 43T ₃ is brought into the brake case 18 of the wet multi-disc brake 17 . In the brake case 18, oil is always secured from the inner bottom surface to the level H, and the oil passage 58 is opened in the transmission case 1 at a position above the oil level OL. Because of this, oil passages 56, 57,
Oil is constantly drained by overflow through 58 to ensure oil flow. From this, the friction plates of the wet multi-disc brake 17 and the mating plate groups 19F, 19
R will be cooled very effectively. Also, the friction plates and mating plate groups 19F and 19R generate a large amount of heat.
In the half brake state due to slip engagement,
The oil drained from the open drain port _43T2 at that time ensures a sufficient amount of cooling oil corresponding to the amount of heat generated.

In addition to the inching valve 34, the drain oil from one drain port 43T ₄ is also connected to the brake case 1.
Although it is possible to lead to within 8, the point of this idea is that
When the wet multi-disc brake 17 is operated in a slip state, the drain port 4 as described above in the inching valve is normally operated to reduce the pressure at the same time.
3T ₂ , that is, the drain port 43T ₂ for discharging drain oil during depressurization operation, is communicated with the inside of the brake case 18, so that the wet multi-disc brake 17
This is intended to ensure sufficient cooling of the brake 17 in the slip state. Further, the inching valve is not limited to the structure shown in the drawings, and other known pressure reducing valves may be used.

As is clear from the above description, the wet multi-disc brake cooling system of this invention has a wet multi-disc brake 17 for vehicle braking on the outer surface of the transmission case 1 housing the hydraulic clutch type vehicle speed change device 8. In addition, an inching valve 34 is provided in the oil supply circuit 28 for the hydraulic clutches 14F, 14R in the vehicle speed change device 8 to selectively reduce the working oil pressure for the hydraulic clutches 14F, 14R with a variable degree of pressure reduction. In the work vehicle, the inching valve 34 is installed on the outer surface of the transmission case 1, and a drain port 4 is provided for discharging drain oil when the inching valve operates to reduce pressure.
3T ₂ and the inside of the brake case 18 of the wet multi-disc brake 17 is provided near the outer surface of the transmission case 1, and the inside of the brake case 18 is set at a level H above the inner bottom surface thereof by an appropriate amount. The brake case 18 and the transmission case 1 are characterized in that oil passages 56, 57, and 58 are provided in the transmission case 1 to communicate with each other at a level above the oil level OL in the transmission case 1. It has the following advantages:

That is, in the cooling device of this invention, based on the above-described configuration, the drain oil from the inching valve 34 is guided into the brake case 18;
Cooling oil is always secured within the brake case 18 up to a suitable height H level, and the flow of the cooling oil is ensured within the brake case 18, so in order to obtain a half-brake state. The wet multi-plate brake 17, which has many chances of causing friction plates to slip, is sufficiently cooled. As shown in the embodiment, when the wet multi-disc brake 17 and the inching valve 34 are operated by the same operating means 50, as well as when they are operated by different operating means. In addition, when operating the wet multi-disc brake 17 in a slip state, the inching valve 34 is normally operated to reduce the pressure at the same time to perform slip operation of the hydraulic clutches 14F and 14R. The drain oil from the inching valve 34 used for slip operation, that is, the inching valve 34 which functions as a pressure reducing valve and increases the amount of oil drain when the hydraulic clutches 14F and 14R are in the slip operation state, is transferred to the brake 1.
7, the cooling device of this invention can extremely effectively cool the brake slip during operation, which generates a large amount of heat.

[Brief explanation of drawings]

Fig. 1 is a partially exploded longitudinal sectional side view showing the transmission case of a traveling work vehicle equipped with an embodiment of this invention, Fig. 2 is a front view of the transmission case, and Fig. 3
The figure is a schematic perspective view of only the essential parts inside the transmission case, Figure 4 is a circuit diagram showing the hydraulic circuit including the above embodiment, and Figures 5 and 6 are the outer surface of the transmission case. FIG. 7 is a perspective view of a part of the mechanism shown in FIGS. 5 and 6, and FIG. This is a graph to show the effect. 1...Mission case, 2...Oil road plate, 3...
...Input shaft, 4F, 4R...Power shift shaft, 5...
...Intermediate shaft, 6...Gear change shaft, 7...Output shaft, 8
...Hydraulic clutch type main transmission, 14F, 14R
... Hydraulic clutch, 17 ... Wet multi-disc brake,
18...Brake case, 19F, 19R...Friction plate and mating plate group, 26...Hydraulic pump, 27...
... Direction switching valve, 28 ... Oil supply circuit, 30 ... Primary pressure regulating valve, 33 ... Flow sensing valve, 34
... Inching valve, 35 ... Valve case,
36...Valve body, 36b...Slot hole, 37...Load piston, 38, 39...Compression spring, 40...Operation shaft, 41...Lever, 42...Pin, 43P ₁ ,
43P ₂ ... pump port, 43C ... clutch port, 43T ₁ , 43T 2 , 43T ₃ , 43T ₄ ... drain port, 45, ₄₆ ... throttle oil passage, 47 ...
...Notch groove, 50...Pedal, 51...Brake lever, 54...Oil passage, 55...Oil passage, 56,5
7,58...Oil road.

Claims (1)

[Scope of utility model registration request] A wet multi-disc brake 17 for braking the vehicle is installed on the outer surface of the transmission case 1 housing the hydraulic clutch type vehicle speed change device 8, and a refueling circuit 28 for the hydraulic clutches 14F and 14R in the vehicle speed change device 8 is installed. , hydraulic clutch 14F, 1
In a traveling work vehicle provided with an inching valve 34 for selectively reducing the working oil pressure for 4R with a variable pressure reduction degree, the inching valve 34
is installed on the outer surface of the transmission case 1 to connect the oil passage 54 that communicates the drain port 43T ₂ for discharging drain oil during decompression operation in the inching valve 34 with the inside of the brake case 18 of the wet multi-disc brake 17. The oil level OL inside the transmission case 1 is provided near the outer surface of the case 1, and the oil level OL inside the transmission case 1 is installed at a level a suitable amount H above the inner bottom surface of the brake case 18.
Oil passages 56, 57, which are communicated at a level above the
58 is provided in the brake case 18 and the transmission case 1.