Work vehicle

Abstract

To decrease an oil temperature in a transmission case efficiently in a work vehicle which utilizes an oil in the transmission case as a hydraulic oil.SOLUTION: A work vehicle includes a work machine lifting hydraulic mechanism 77 which uses an oil stored in a transmission case 12 as a hydraulic oil to move up or down a work machine. The work vehicle includes a radiator 108 in an engine hood 6, a main oil cooler 107 is disposed in front of the radiator 108, and a sub oil cooler 109 is disposed at the rear of a machine body. The main oil cooler 107 is provided in a reduction oil passage 106 from the work machine lifting hydraulic mechanism 77 to the transmission case 12, and the sub oil cooler 109 is provided at a branched oil passage 106a branched from the reduction oil passage 106.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a work vehicle such as an agricultural tractor that has a liftable work implement attached to the rear of the vehicle body, and more particularly to an oil cooler for a hydraulic mechanism that uses oil in a transmission case as hydraulic fluid. [Background technology]

[0002] In conventional agricultural tractors, a configuration is known in which multiple cooling devices are provided inside the hood, ahead of the engine, and the multiple cooling devices are arranged from the front of the hood in order of decreasing heat dissipation capacity (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-101813 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the temperature of the airflow drawn into the hood gradually rises, but the further back the cooling equipment is located, the greater its heat dissipation capacity, allowing for more efficient cooling, preventing equipment breakdowns and malfunctions and maintaining performance. However, there are limitations on the installation space within the hood. Therefore, when a tractor is continuously operated under heavy load in a warm climate, the oil temperature in the transmission tends to rise, causing rapid deterioration of the bushings and the oil itself.

[0005] In view of the above, an object of the present invention is to efficiently lower the oil temperature in a transmission case in a work vehicle that uses oil in the transmission case as hydraulic fluid. [Means for solving the problem]

[0006] The present invention provides the following technical means to solve the above problems.

[0007] The invention described in claim 1 is a work vehicle equipped with a work equipment lifting hydraulic mechanism (77) that uses oil stored in a transmission case (12) as hydraulic oil and lifts and lowers the work equipment, and is provided with a radiator (108) inside the hood (6), a main oil cooler (107) arranged in front of the radiator (108), and a sub-oil cooler (109) arranged at the rear of the vehicle body.

[0008] A second aspect of the present invention is the same as the first aspect, wherein the sub-oil cooler (109) includes a core (109a) and a blower fan (109b).

[0009] The invention as set forth in claim 3 is the same as the invention as set forth in claim 2, except that a mudguard cover (109c) is provided.

[0010] The invention described in claim 4 is the invention described in claim 1, in which a main oil cooler (107) is provided in a return oil passage (106) from the work machine lifting hydraulic mechanism (77) to the transmission case (12), and a sub-oil cooler (109) is provided in a branch oil passage (106a) branching off from the return oil passage (106). [Effects of the Invention]

[0011] According to the invention described in claim 1, if cooling equipment such as a radiator and oil cooler are installed together in one place, the overall cooling function will be reduced, which will have the opposite effect. However, by placing the radiator inside the hood, placing the main oil cooler in front of it, and placing the sub-oil cooler at the rear of the aircraft, it is possible to suppress the rise in hydraulic oil temperature and maintain it at an appropriate temperature without reducing the overall cooling effect.

[0012] According to the invention as set forth in claim 2, in addition to the effect of claim 1, the cooling of the sub-oil cooler can be improved by the cooling air taken in from the rear of the aircraft by the rotation of the blower fan.

[0013] According to the invention of claim 3, in addition to the effect of claim 2, the presence of the mud cover prevents the sub-oil cooler from being soiled by mud scattered from below.

[0014] According to the invention described in claim 4, in addition to the effect described in claim 1, the sub-oil cooler is installed in a branched oil passage that branches off from the return oil passage in which the main oil cooler is installed, so malfunctions due to rising oil temperatures can be prevented in advance when working in warm climates. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic side view of a tractor according to an embodiment of the present invention. [Figure 2] 1 is a schematic rear view of a tractor according to an embodiment of the present invention. [Figure 3] 1 is a diagram showing a transmission mechanism of a transmission device of a tractor according to an embodiment of the present invention; [Figure 4] 1A is a plan view of a cylinder case portion of a tractor according to an embodiment of the present invention, and FIG. 1B is a partially cross-sectional side view thereof. [Figure 5] 1 is a diagram showing an example of a hydraulic circuit of a tractor according to an embodiment of the present invention; [Figure 6] 1 is a partially omitted perspective view showing a working machine coupling device at the rear of a transmission case of a tractor according to an embodiment of the present invention; [Figure 7] 1A and 1B are a side view and a rear view, respectively, of a working implement coupling device for a tractor according to an embodiment of the present invention. [Figure 8] 1 is a perspective view of the inside of a hood of a tractor according to an embodiment of the present invention. [Figure 9] FIG. 2 is a perspective view showing the arrangement of an oil cooler of the tractor according to the embodiment of the present invention. [Figure 10] FIG. 2 is a perspective view of the rear of the cabin of the tractor according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] The tractor 1 of this embodiment shown in FIGS. 1 to 4 is an agricultural tractor that performs work in a field or the like while propelled by power generated by a power source. The tractor 1 has front wheels 2, rear wheels 3, an engine 4 as a power source, and a transmission 5. Of these, the front wheels 2 are provided as wheels primarily used for steering, i.e., as steering wheels. The rear wheels 3 are primarily used as wheels primarily used for driving, i.e., as drive wheels. Rotational power generated by an engine 4 mounted inside a hood 6 at the front of the vehicle can be transmitted to the rear wheels 3 after being appropriately reduced in speed by the transmission 5, and the rear wheels 3 generate driving force using this rotational power. The transmission 5 can also transmit the rotational power generated by the engine 4 to the front wheels 2 as needed. In this case, the front wheels 2 and rear wheels 3 act as drive wheels, generating driving force. That is, the transmission 5 is capable of switching between two-wheel drive and four-wheel drive, and is capable of reducing the rotational power of the engine 4 and transmitting the reduced rotational power to the front wheels 2 and the rear wheels 3. The tractor 1 is also provided with a coupling device 7 at the rear of the body to which a work implement such as a rotary (not shown) can be attached. The coupling device 7 is, for example, a three-point link consisting of a top link 7a at the top center and lower left and right links 7b, 7b at the bottom, and connects the work implement to the rear of the body of the tractor 1. By hydraulically rotating the left and right lift arms 72L, 72R as described below, the tractor 1 can raise and lower the work implement via the lift rods and the lower links 7b connected to the lift rods.

[0018] The tractor 1 has a driver's seat 8 on the body of the vehicle, which is surrounded by a cabin 9. Inside the cabin 9, a steering wheel 11 is installed upright on a dashboard 10 in front of the driver's seat 8, and various operation pedals such as a clutch pedal, a brake pedal, and an accelerator pedal, as well as various operation levers such as a forward / reverse lever and a gear lever are arranged around the driver's seat 8.

[0019] 3 is a diagram showing the transmission mechanism 13 inside the transmission case 12 of the transmission 5. The transmission 5 is configured to include the transmission case 12 (see FIG. 1) and the transmission mechanism 13 that is disposed inside this transmission case 12 and transmits rotational power from the engine 4 to the rear wheels 3, etc. The transmission mechanism 13 transmits the rotational power from the engine 4 to the front wheels 2, the rear wheels 3, and the work implement attached to the machine body, and drives these with the rotational power from the engine 4.

[0020] The transmission mechanism 13 can transmit the rotational power generated by the engine 4 to the rear wheels 3 via the input shaft 14, forward / reverse switching mechanism 15, Hi-Lo transmission mechanism 16, main transmission mechanism 17, and auxiliary transmission mechanism 18 in this order. The transmission mechanism 13 can also transmit the rotational power generated by the engine 4 to the front wheels 2 via the input shaft 14, forward / reverse switching mechanism 15, Hi-Lo transmission mechanism 16, main transmission mechanism 17, auxiliary transmission mechanism 18, and 2WD / 4WD switching mechanism 19 in this order. The transmission mechanism 13 can also transmit the rotational power generated by the engine 4 to the work equipment via the input shaft 14 and PTO drive mechanism 20 in this order.

[0021] The forward / reverse switching mechanism 15 changes the transmission path of the rotational power transmitted to the input shaft 14 to either forward rotation or reverse rotation depending on the engaged / disengaged state of the forward / reverse hydraulic multi-plate clutches C1, C2, and transmits it to the counter shaft 21.

[0022] The Hi-Lo transmission mechanism 16 changes the transmission path of the rotational power transmitted to the countershaft 21 to either the Hi-side gear or the Lo-side gear depending on the engaged / disengaged state of the hydraulic multi-plate clutches C3, C4, and transmits it to the transmission shaft 22. The rotational power transmitted to the transmission shaft 22 is then transmitted to the transmission shaft 23 after being shifted through the first to sixth gears.

[0023] The auxiliary transmission mechanism 18 is capable of changing the speed of the rotational power transmitted from the engine 4 sequentially via the forward / reverse switching mechanism 15, the Hi-Lo transmission mechanism 16, and the main transmission mechanism 17. The auxiliary transmission mechanism 18 changes the speed of the rotational power transmitted to the transmission shaft 23, and transmits it to the transmission shaft 26 via a first auxiliary transmission 24, a second auxiliary transmission 25, etc.

[0024] The transmission mechanism 13 of the transmission 5 then transmits the rotational power transmitted to the speed change shaft 26 to the rear wheels 3 via a rear wheel differential 27, a rear axle 28, a planetary gear reduction mechanism 29 for speed reduction, etc. As a result, the rear wheels 3 of the tractor 1 are driven to rotate as drive wheels by the rotational power from the engine 4.

[0025] The 2WD / 4WD switching mechanism 19 switches whether or not the rotational power transmitted to the transmission shaft 26 is transmitted to the front wheels 2. The 2WD / 4WD switching mechanism 19 also functions as a front wheel speed increasing mechanism by including hydraulic multi-plate clutches C6 and C7.

[0026] The transmission mechanism 13 of the transmission 5 transmits the rotational power transmitted to the 2WD / 4WD switching mechanism 19 to the front wheels 2 via a front wheel differential 34, a front axle 35, a vertical shaft 36, a planetary gear reduction mechanism 37, etc. As a result, the front wheels 2 and rear wheels 3 are rotated and driven as drive wheels by the rotational power from the engine 4, and the tractor 1 can travel in four-wheel drive.

[0027] The PTO drive mechanism 20 changes the speed of the rotational power transmitted from the engine 4 and outputs it to the work equipment from a PTO shaft 40 (see Figures 2 and 3) at the rear of the machine body, thereby driving the work equipment with the power from the engine 4. The PTO drive mechanism 20 is composed of a PTO clutch mechanism 38, a PTO speed change mechanism 39, the PTO shaft 40, etc.

[0028] When the hydraulic multi-plate clutch C5 is engaged, the PTO clutch mechanism 38 enters a PTO drive state in which power is transmitted to the PTO shaft 40, and the rotational power transmitted from the input shaft 14 to the gear 38a via the gear 41 is transmitted to the transmission shaft 38b via the hydraulic multi-plate clutch C5.

[0029] The tractor 1 is provided with a gear pump 70, which is a hydraulic pump, via a gear that meshes with the gear of the PTO clutch mechanism 38. The gear pump 70 applies hydraulic pressure to the hydraulic system of the transmission mechanism 13 and the like.

[0030] A cylinder case 71 is attached to the upper rear surface of the transmission case 12, and forms a work machine lifting hydraulic mechanism 77. Specifically, a lift arm shaft 72 having a horizontal axis is rotatably supported in this cylinder case 71, and a piston is provided inside the cylinder case 71. A rod portion 73 connected to this piston and a rod receiving portion 72a at the center of the lift arm shaft 72 are linked together to rotate the lift arm shaft 72 in the direction of the arrow in Figure 4(B) by extending the piston mechanism. Lift arms 72L, 72R are attached to the left and right sides of the lift arm shaft 72, and the lift arm shaft 72, piston, rod portion 73, and lift arms 72L, 72R form the work machine lifting hydraulic mechanism 77, which is configured to be able to raise and lower the work machine in conjunction with the mechanism, as will be described later.

[0031] The work implement lifting hydraulic mechanism 77 is provided with a lift control valve 74 that controls the supply or discharge of pressurized oil to the cylinder case 71 to cause the piston to slide back and forth, and both the work implement lifting side 74U and the work implement lowering side 74D of the lift control valve 74 are arranged in parallel within the valve body as so-called proportional control valves and are attached to the top surface of the cylinder case 71.

[0032] As shown in Figure 6, a hitch mechanism 80 for a work machine such as a trailer is configured at the rear of the transmission case 12. This hitch mechanism 80 includes a hitch frame 82 consisting of a pair of upper and lower hitch plates 82a, 82a and left and right side plates 82b, 82b into which a connecting pin 81 can be inserted in the vertical direction, and a base member 83 that is firmly attached to the rear of the transmission case 12 with bolts or the like.

[0033] The three-point linkage device 7 is provided at the rear of the transmission case 12. As shown in FIG. 7 , the three-point linkage device 7 comprises an upper central top link 7a and lower left and right lower links 7b, 7b. The top link 7a is connected via a connecting pin to a link ball portion attached to the base end of one end of a top link bracket 90, which is detachably connected to the rear of the transmission case 12 by bolts, so that the top link 7a can rotate up and down. The other end of the top link 7a is provided with a through-hole for a pin for connecting a work machine. The lower links 7b, 7b are connected to the link ball portions at the tips of the lower links 7b, 7b by connecting pins formed integrally with lower link brackets (not shown) on the left and right lower rear parts of the transmission case 12 or rear axle cases 91, 91 connected to the left and right side surfaces of the transmission case 12. Link balls are attached to the rear ends of the lower links 7b, 7b, so that the work machine can be connected via connecting pins 92, 92. Lift rods 93, 93 are connected to the middle portions of the lower links 7b, 7b, respectively, and the lift rods 93, 93 are connected to the left and right lift arms 72L, 72R that constitute the work equipment lifting hydraulic mechanism 77 at the upper rear of the transmission case 12, and are configured to be able to be raised and lowered in conjunction with the work equipment lifting hydraulic mechanism 77.

[0034] As shown in Figure 7, an auxiliary cylinder mechanism 95 is added to the work machine lifting hydraulic mechanism 77. The lower end of the cylinder portion 95a of the auxiliary cylinder mechanism 95 is supported by utilizing the base member 83 of the hitch mechanism 80, and the upper end of the sliding shaft 95b is connected to one of the left and right lift arms 72L, 72R (the left lift arm 72L in the illustrated example). The auxiliary cylinder mechanism 95 receives a portion of the pressure oil supplied to the work machine lifting hydraulic mechanism 77 and extends, assisting the lift arms 72L, 72R in lifting the work machine.

[0035] Next, an overview of the hydraulic circuit of the tractor of this embodiment will be explained with reference to Figures 5 to 10. Pressurized oil from the gear pump 70 passes through an unload valve 100 and an auxiliary cylinder control unit 101 and enters an external hydraulic control valve 102 (four valves 102a to 102d in the illustrated example), and forms an oil passage 103 that bypasses the external hydraulic control valve 102 to the unloaded state. Pressurized oil is supplied via this oil passage 103 to a work implement horizontal control valve 104, and further to the work implement lift control valve 74.

[0036] The auxiliary cylinder control unit 101 and the external hydraulic control valve 102 are attached to the upper rear surface of the cylinder case 71.

[0037] Therefore, when the work implement is to be linked to be raised, the lift control valve 74, which is a hydraulic control valve for raising and lowering the work implement and which controls the supply and discharge of pressurized oil to the work implement lift hydraulic mechanism 77, supplies pressurized oil to the cylinder portion of the work implement lift hydraulic mechanism 77 to perform an extension operation, and at the same time, a portion of the pressurized oil is supplied to the auxiliary cylinder mechanism 95, which is provided in parallel therewith, to perform an extension operation. Note that with regard to the supply of hydraulic pressure from the lift control valve 74 to the cylinder portion of the work implement lift hydraulic mechanism 77 and the cylinder portion of the auxiliary cylinder mechanism 95, the control pressure oil controlled to the lift rotation side of the lift arms 72L, 72R by excitation of the work implement lift side 74U of the work implement lift control valve 74 is supplied to the work implement lift hydraulic mechanism 77 via the valve body and oil passage 74a (Fig. 5) formed in the cylinder case 71. An auxiliary cylinder 95 is connected to a branch oil passage 74b (shown in the figure) branching from the valve body oil passage 74a, and the auxiliary cylinder mechanism 95 is configured to be extendable.

[0038] In addition, for control of the downward rotation side of the lift arms 72L, 72R, the valve body oil passage 74a is switched to the return oil passage 74c by energizing the work equipment lowering side 74D of the work equipment lifting control valve 74, and the working pressure oil of the work equipment lifting hydraulic mechanism 77 and the working pressure oil for extension of the auxiliary cylinder mechanism 95 are discharged into the transmission case 12 which serves as a tank, thereby allowing the work equipment to be lowered.

[0039] Furthermore, the hydraulic oil in the supply oil passage 74d from the work implement level control valve 104 to the work implement lift control valve 74 is configured to be returned to the transmission case 12 via a return oil passage 74e when the work implement lift side 74U of the work implement lift control valve 74 is in a non-excited state. More specifically, a relief valve 105 is provided on the side of the working pressure oil supply oil passage 74d of the work implement lift control valve 74, and when the relief pressure is reached, the supplied working pressure oil is returned to the transmission case 12 via the return oil passage 74e. The return oil passage 74e is configured to merge with a return oil passage 106 of a relief valve 100b arranged in the supply side oil passage 100a of the unload valve 100, and the outlet of the return oil passage 106 is configured to be able to supply return oil to a hydraulic multi-plate clutch C5 serving as a PTO hydraulic clutch of a PTO clutch hydraulic circuit 114 arranged in the transmission case 12.

[0040] An oil cooler (hereinafter referred to as a main oil cooler) 107 for cooling the hydraulic oil is interposed in the return oil passage 106. As shown in FIG. 8, the oil cooler 107 is appropriately installed near the location of a cooling water radiator 108 for the engine 4 inside the hood 6 that houses the engine 4. The main oil cooler 107 in the illustrated example is a vertically elongated water-cooled type, but it may also be an air-cooled type. A sub-oil cooler 109 is provided in a branch oil passage 106a that branches off from the return oil passage 106. This sub-oil cooler 109 is disposed on the upper rear surface of the transmission case 12, different from the location of the main oil cooler 107, to eliminate any influence on the radiator 108. The sub-oil cooler 109 is composed of a core portion 109a that is framed with bypass hydraulic oil tubes and plate fins or corrugated fins, and a blower fan 109b on its rear surface, and is attached to the lower rear surface of the cabin 9. The blower fan 109b is, for example, an electric fan. Further, the sub-oil cooler 109 is provided with a mud cover 109c that covers the entire sub-oil cooler 109.

[0041] If the cooling equipment is installed in one place, the overall cooling function will be reduced, which will have the opposite effect. By arranging the radiator 108 and main oil cooler 107 at the front of the aircraft and the sub-oil cooler 109 at the rear of the aircraft, it is possible to suppress the rise in oil temperature and maintain it at an appropriate temperature without reducing the overall cooling effect.

[0042] Furthermore, the rotation of blower fan 109b of sub-oil cooler 109 allows cooling air to be taken in from the rear of the aircraft, improving the cooling effect of sub-oil cooler 109. Furthermore, the presence of mud cover 109c prevents the main body of sub-oil cooler 109 from being soiled by mud scattered from below.

[0043] Sub-oil cooler 109 is installed in branched oil passage 106a branched from return oil passage 106 in which main oil cooler 107 is installed, so malfunctions due to rising oil temperature can be prevented in advance when working in warm climates.

[0044] In the hydraulic circuit diagram of FIG. 5, reference numeral 110 denotes a steering control hydraulic circuit, 111 denotes a main shift clutch hydraulic circuit (four-speed), 112 denotes a forward / reverse clutch hydraulic circuit, and 113 denotes a Hi-Lo shift clutch hydraulic circuit. [Explanation of symbols]

[0045] 6. Bonnet 12 Transmission case 77 Hydraulic mechanism for lifting and lowering work equipment 106 Reduction oil path 106a Branch oil passage 108 Radiator 109 Sub oil cooler 109a Core 109b Blower fan 109c Mudguard Cover

Claims

1. The work vehicle is provided with a working machine lifting hydraulic mechanism (77) that uses oil stored in a transmission case (12) as hydraulic oil and interlocks the lifting and lowering of the working machine, and is provided with a radiator (108) in the hood (6), a main oil cooler (107) disposed in front of the radiator (108), and a sub-oil cooler (109) disposed at the rear of the vehicle body.

2. 2. The work vehicle according to claim 1, wherein the sub-oil cooler (109) comprises a core portion (109a) and a blower fan (109b).

3. 3. A work vehicle according to claim 2, further comprising a mudguard cover (109c).

4. 2. The work vehicle according to claim 1, wherein a main oil cooler (107) is provided in a return oil passage (106) from a work machine lifting hydraulic mechanism (77) to a transmission case (12), and a sub-oil cooler (109) is provided in a branch oil passage (106a) that branches off from the return oil passage (106).

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