JP2008221861A - All-wheel hydraulic drive riding-type lawn mower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically switch an "all-wheel drive system" and a "front wheel drive system" when mowing a lawn while descending a slope, in a riding-type lawn mower which is driven by a hydraulic motor individually installed at each wheel by using a single hydraulic pump. <P>SOLUTION: In this lawn mower of a riding type for driving all the wheels hydraulically and driving each hydraulic motor MF, MB provided at each wheel WF, WB individually by one hydraulic pump A incorporated in a position for forming one driving loop circuit in a main pipe passage L<SB>0</SB>, a check valve V<SB>1</SB>, an automatic selector valve V<SB>2</SB>, and a relief valve V<SB>3</SB>are incorporated in a hydraulic circuit C<SB>1</SB>to switch the "all-wheel drive system" and the "front-wheel drive system" alternately by using a time immediately before the ground contact pressure of the rear wheel WB is reduced and the slip of the rear wheel WB is generated and a time when the slip of the rear wheel WB is not generated due to an increase of the ground contact pressure of the rear wheel WB as a reference. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a riding lawn mower that drives each hydraulic motor individually provided on all wheels by a single hydraulic pump. When performing lawn mowing work on a slope, all the wheels of the airframe are driven. And the method in which only the front wheels are driven (hereinafter referred to as “front wheel drive method”), the time immediately before the ground pressure of the rear wheel is reduced and the slip occurs, and The present invention relates to an all-wheel hydraulically driven riding lawn mower that is automatically switched to each other when the oil pressure acting on the front wheels changes from the holding pressure to the driving pressure.

The configuration and problems of an all-wheel hydraulically driven riding lawn mower that drives each hydraulic motor individually provided on all wheels by one hydraulic pump will be described. FIG. 11 is a diagram showing a conventional hydraulic circuit C ₂ of a four-wheel structure all-wheel hydraulically-driven riding lawn mower. In a four-wheel structure all-wheel hydraulically driven riding lawn mower, the two front wheels WF are each driven by a separate hydraulic motor MF, and the two rear wheels WB are each driven by a separate hydraulic motor MB. All wheels are driven by individual hydraulic motors. Four motor conduit relative to the main lines L ₀ to the effect of the pressure of one hydraulic pump A (parallel _{line) L 1, L 2, L} 3, L 4 are connected in parallel, main line L ₀ One hydraulic pump A is incorporated so as to form one “drive loop circuit” as a whole, and is composed of two hydraulic motors MF for front wheels and two hydraulic motors MB for rear wheels. Each of the four hydraulic motors MF, MB is incorporated in each of the motor pipelines L ₁ , L ₂ , L ₃ , L ₄ .

For this reason, when traveling straight forward or immediately on a flat ground, for example, if the front wheels and rear wheels have the same diameter and the hydraulic motor capacity is the same, the peripheral speeds of all the wheels must be the same. The flow rate Q of the pressure oil supplied from the hydraulic pump A is equally divided into (Q / 4) to each of the motor lines L ₁ , L ₂ , L ₃ , and L ₄ for a total of four hydraulic motors. MF and MB are rotated at the same rotation speed. As a result, the riding lawn mower moves forward or immediately. On the other hand, when turning in a forward or reverse state on a flat ground, the inner wheel needs to have a lower peripheral speed than the outer wheel, and in turns other than circular turning, the circumference of each front and rear wheel on the same side is required. The speeds need to be slightly different, and a total of four hydraulic motors MF and MB are supplied from the hydraulic pump A to select the number of revolutions necessary for smoothly turning the riding lawn mower. The flow rate of the pressure oil is unevenly distributed to the motor lines L ₁ , L ₂ , L ₃ and L ₄ . For this reason, an all-wheel hydraulically-driven riding lawn mower equipped with a hydraulic circuit that drives all four hydraulic motors MF and MB by one hydraulic pump A has all wheels turned when turning on the turf surface. Since it is always rotated by the required number of revolutions and a specific wheel does not over or under rotation, there is an advantage that the turning is always smooth and the lawn is not damaged by the wheel.

However, in the case of performing lawn mowing work on a turf surface having a mountain part and a valley part, as shown in FIGS. 13 and 14, the ground pressures of the two front wheels WF are compared with those on a flat ground. As (P ₁₁ ) increases, the ground pressure (P ₁₂ ) of the two rear wheels WB decreases, and as the gradient increases, the ground pressure (P ₁₁ ) of the front wheels WF and the ground pressure (P _Since the difference from ₁₂ ) becomes large, the following problems have occurred. 14 (a) and 14 (b) are graphs showing the relationship between the contact pressure and the holding pressure of the front and rear wheels of the aircraft with respect to the slope of the slope, respectively. The machine body is stopped or the discharge amount of the hydraulic pump is zero. That is, each hydraulic motor MF of the front wheel WF having a large ground pressure (P ₁₁ ) is driven and rotated by the front wheel WF when the slope of the slope increases beyond the limit, so that it not only functions as an original hydraulic motor, Since each hydraulic motor MB of the rear wheel WB having a small ground pressure also functions as a hydraulic motor that rotates only by the supplied hydraulic oil, the hydraulic motor of the front wheel WF has a function as a hydraulic pump. The relationship between the pressure (P ₁ ) on the discharge side of MF and the pressure (P ₂ ) on the inflow side is reversed, and the latter becomes larger than the former. The pressure (P ₂ ) on the inflow side of the hydraulic pump A having such a relationship is an oil pressure that keeps the current state by preventing the aircraft from going down a steep slope due to its own weight (gravity action). , Referred to as “holding pressure”. That is, the inflow side pressure (P ₂ ) that is larger than the discharge side pressure (P ₁ ) acts to reversely rotate the hydraulic motors MF and MB of both the front wheel WF and the rear wheel WB. For this reason, when the ground pressure of the rear wheel MB decreases and the frictional resistance against the turf surface decreases, the rotational speed of the rear wheel WB becomes smaller than the rotational speed of the front wheel WF, and further, the gradient increases and the ground pressure decreases. The rear wheel WB stops rotating and then rotates backward. As a result, since the rear wheel WB cannot follow the inclined surface and rotate, the rear wheel is dragged with respect to the inclined surface (hereinafter referred to as “locked state”), and the body is in the rear wheel steering. However, there was a problem that the steering wheel could not be operated and the airframe would run away, so that the lawn mowing work could not be performed on the original route, and the lawn could be seriously damaged by slipping of the rear wheels.

To solve the problems described above, by using the switching valve, incorporating a switching valve V ₁₀ for switching manually between "front wheel drive system" in which the "all wheel drive system" that drives all wheels driving only the front wheels A hydraulic circuit (C ₃ ) is employed. FIGS. 12A and 12B are diagrams showing the hydraulic circuit C ₃ in the “all-wheel drive system” and “front-wheel drive system” of a four-wheel structure all-wheel hydraulically-driven riding lawn mower, respectively. In the conventional hydraulic circuit (C ₁ ) shown in FIG. 11, the switching valve V ₁₀ for switching the driving system includes motor lines L ₁ and L _{2 in} which the hydraulic motors MF for the front wheels WF are incorporated, and the rear wheels. The WB hydraulic motor MB is incorporated at a position where the motor pipelines L ₃ and L ₄ into which the hydraulic motor MB is incorporated are divided.

For this reason, in the case of the “front wheel drive system” shown in FIG. 12 (a), it is the same as the hydraulic circuit described above, and it is a case where the vehicle moves forward or immediately on a flat ground. On the other hand, when performing mowing down the slope of the steep switches the switching valve V ₁₀ driver manually so that the circuit shown in FIG. 12 (b). As a result, the main pipeline L ₀ forming one “drive loop circuit” is a “drive loop on the front wheel side including the motor pipelines L ₁ and L _{2 in} which the hydraulic motors MF for the front wheels WF are incorporated. The circuit is divided into two “loop circuits”, that is, an “idle loop circuit” on the rear wheel side including the motor lines L ₃ and L _{4 in} which the hydraulic motors MB for the rear wheels WB are incorporated. As a result, the pressure oil of the hydraulic pump A is supplied only to the hydraulic motors MF for the front wheels WF, and the “idle loop circuit” on the rear wheel side is not supplied with the pressure oil of the hydraulic pump A, so that the rear wheels The low pressure oil inside circulates in the “idle loop circuit” by the driven rotation of WB. In other words, only each front wheel WF is driven to rotate, and each rear wheel WB is switched to the “front wheel drive system” in which it is driven to rotate.

For this reason, the problem that each rear wheel WB becomes “locked” and cannot be steered is solved. However, since the operation of the switching valve V ₁₀ is performed by the operator's judgment, the switching operation is delayed. When the vehicle is lowered on a steep slope by the “drive system”, the above-described problem that the rear wheel WB is “locked” occurs. On the other hand, when the switching operation is accelerated, the cutting length by the “front wheel drive method” in which the speed of the airframe is increased is lengthened, and the unsightly part (the rotational speed of the rotary blade remains constant) When the speed is increased, there is a problem that the length of the lawn is cut roughly compared to before the speed increase). Thus, it is very difficult timing of the operation of the switching valve V _10, yet each time it reaches the slope of the descending slope, there is a need to perform a switching operation, there is a problem that it is extremely troublesome.

Further, in the hydraulic circuit C ₃ provided with the manual switching valve V ₁₀ , it is detected that the lawn mower has reached the downhill slope and “holding pressure” is generated, and the switching valve V _{10 is} detected by this detection signal. A hydraulic circuit improved to automatically open and close is also adopted. The hydraulic circuit according to the improvement automatically switches between the “all wheel drive system” and the “front wheel drive system” by operating the switching valve V ₁₀ in response to a generation signal of “holding pressure” in the circuit.

  However, in the hydraulic circuit according to the above improvement, since the “holding pressure” generation in the circuit is used as a reference for switching the driving method, it can be switched to the “front wheel driving method” even on a downward slope where the rear wheel does not slip. In addition, the cutting length of the "front wheel drive system", which increases the traveling speed of the fuselage, becomes longer, and the area of the cut surface looks worse, and the "all wheel drive system" and "front wheel drive system" Are frequently switched to each other, and as a result, the speed of the airframe is frequently increased or decreased, and there is a problem of traveling in a state where the airframe is “cracked” by a small impact force acting on the airframe. This problem occurs not only when the aircraft is moving forward but also when moving backward. As described above, the hydraulic circuit that switches the driving method when the “holding pressure” is generated has a fatal problem that the reference for switching the driving method cannot be changed by the operator. There is no prior patent document related to the present invention.

  In the riding lawn mower of the type in which each hydraulic motor individually provided on all wheels is driven by a single hydraulic pump, the ground pressure of the rear wheel is reduced when performing lawn mowing work on a slope. Based on the time immediately before the rear wheel slips and the time when the hydraulic pressure acting on the front wheel changes from the holding pressure to the driving pressure, the `` all wheel drive system '' and the `` front wheel drive system '' are mutually By switching, the cutting length of the front wheel drive system that occurs when performing lawn mowing work on an inclined ground is shortened as much as possible to improve the cutting condition, and the number of times of switching the drive system is reduced, and the body at the time of switching It is an object to reduce the impact force acting on the hill so that the lawn mowing work can be carried out smoothly down the slope.

  According to the first aspect of the present invention for solving the above-described problems, the same number of motor lines as the number of wheels are connected in parallel to the main line, and each motor line includes a hydraulic motor for a front wheel and a rear wheel. Are incorporated in a form divided into two along the direction in which the pressure oil flows in the main pipeline, and each wheel is provided by a single hydraulic pump incorporated in a position where one drive loop circuit in the main pipeline can be formed. An all-wheel hydraulically-driven riding lawn mower of a type that individually drives each provided hydraulic motor, wherein the hydraulic oil discharged from a hydraulic pump flows in the main line when the vehicle is moving backward, and for front wheels And a check valve that allows only the flow of pressure oil from the rear wheel side toward the front wheel side, and is discharged from the hydraulic pump in the main line. The motor lines for front wheels and rear wheels are divided into two along the direction of oil flow, and they are incorporated in the switching valve lines connected in parallel with the motor lines at positions closer to the rear wheels than the check valve. And an automatic switching valve that opens and closes by each pilot pressure taken from both sides of the check valve, and each motor pipe line at the rear wheel side with respect to the check valve in the main pipe line And a relief valve incorporated in the relief valve pipe connected in parallel to the switching valve pipe.

  According to the first aspect of the present invention, when the lawn mowing operation is performed down the slope, the synergistic action of the holding pressure of the front wheel and the holding pressure of the rear wheel blocked by the check valve and the ground pressure of the lowered rear wheel is achieved. The relief valve is opened by the holding pressure immediately before the rear wheel starts to slide, the holding pressure of the rear wheel is released, and each of the front wheel side and the rear wheel side acting on the automatic switching valve immediately after the opening is opened. By opening the automatic switching valve due to an increase in the pilot pressure difference, an "idle loop circuit" of low-pressure oil is formed in each motor circuit on the rear wheel side, the switching valve circuit, and the main line on the rear wheel side, The all-wheel drive system is automatically switched to the front wheel drive system. As described above, the pressure difference at which the relief valve is opened is equal to the holding pressure just before the rear wheel slips (more precisely, the difference between the holding pressure and the pressure of the pressure oil discharged from the hydraulic pump). Therefore, immediately before the rear wheel slips due to an increase in the slope of the slope, the rear wheel side is closed by the check valve with the holding pressure of the front wheel. Since an “idle loop circuit” is formed, the rear wheels are driven to rotate and no slip occurs. On the other hand, when the “idle loop circuit” is formed on the rear wheel side, if the oil pressure acting on the front wheel changes from the holding pressure to the driving pressure, the flow of pressure oil in the hydraulic circuit changes in the reverse order. Thus, the front wheel drive system is automatically switched to the all-wheel drive system.

  For this reason, the cutting operation by the front wheel drive method in which the airframe speeds up relative to the all-wheel drive method is only the part where the slope of the descending slope is large and the rear wheel slips (that is, the front wheel drive on the descending slope) Since the method is indispensable only at a large portion of the slope), the cutting length by the front wheel driving method is shortened, and the cutting state on the slope with the downward slope is improved. In addition, the automatic switching valve is opened, and the “idle loop circuit” is formed on the rear wheel side after the relief valve is opened and the pilot pressures on the front wheel side and the rear wheel side acting on the automatic switching valve are reduced. After the difference increases to a certain level or more, and after the relief valve is activated until the automatic switching valve is activated, the driving force of the rear wheels decreases for a predetermined time and all wheels are driven. Since the system can be switched from the front-wheel drive system, damage to the lawn when switching the drive system can be minimized, and there is almost no impact force acting on the fuselage when switching the drive system. Since it is performed smoothly, driving operation becomes easy.

  Further, in the invention of claim 2, when the lawn mowing work is carried out backward, such as when going up or down on an inclined ground, or going backward on a flat ground, by the action of the check valve, The pressure oil discharged from the hydraulic pump has a configuration that does not reach the hydraulic motor for the rear wheel, so it is always the front wheel drive system regardless of the change in the slope of the slope, and by switching the drive system during traveling There is an advantage that there is no change in the lawn mowing state.

  The invention of claim 3 is the portion of the invention of claim 1 or 2 in which the pressure oil discharged from the hydraulic pump flows when the vehicle moves forward in the main pipeline, and each motor for front wheels and rear wheels A first manual switching valve incorporated in a position that bisects the pipeline, and a first manual switching valve that transmits to and shuts off the automatic switching valve using the pressure at the rear wheel side as a pilot pressure with reference to the check valve in the main pipeline. And 2 manual switching valves.

  According to the invention of claim 3, during the non-turf cutting operation, the first and second manual switching valves are both closed so that the main lines on the front wheel side and the rear wheel side are checked with the first manual switching valve. While being blocked by the valve and the pressure of the main pipe line on the rear wheel side does not act as a pilot pressure on the automatic switching valve across the check valve, a `` drive loop circuit '' is formed on the front wheel side, An “idle loop circuit” is formed on the rear wheel side, so that the front wheel drive system is adopted, and the traveling speed of the aircraft is increased. On the other hand, if the first and second manual switching valves are both opened and the first and second manual switching valves are not incorporated at the time of lawn mowing, for the reason described above, the downward slope is reduced. In an inclined place, the all-wheel drive method and the front wheel drive method are automatically switched according to the gradient.

  According to a fourth aspect of the present invention, in the third aspect of the invention, the first manual switching valve is configured such that either an open passage or a check valve is selected. Since the main pipe line is closed by putting the check valve into the operating state, there is an advantage that oil leakage from the first manual switching valve portion is reduced when the main pipe line is closed.

  According to the present invention, in a riding lawn mower of a type in which each hydraulic motor individually provided on all wheels is driven by one hydraulic pump, when performing lawn mowing work on a slope, it responds to a change in descending slope. Based on the time immediately before the rear wheel contact pressure decreases and the rear wheel slips, and the time when the slip does not occur due to the increase in the rear wheel contact pressure, the "all wheel drive system" And “front wheel drive system” are automatically switched between each other, so that the cutting length by the front wheel drive system that occurs during lawn mowing work on downhill slopes can be shortened as much as possible to improve the cutting condition. In addition, the number of times of switching the drive system is reduced, and the impact force acting on the airframe at the time of switching is alleviated, so that mowing work can be performed smoothly on uphill and downhill terrain.

Hereinafter, the present invention will be described in more detail with reference to the best mode. FIG. 1 is a hydraulic circuit diagram of an all-wheel hydraulically driven riding lawn mower having a drive system automatic switching function according to the present invention. First, the configuration of the hydraulic circuit C ₁ according to the present invention will be described in relation to the conventional hydraulic circuits C ₂ and C _3, and then various lawn mowers related to the combination of flat ground or sloping ground and forward or reverse of the airframe. The driving method in the cutting state will be described step by step. In the description of the hydraulic circuit C ₁ , the same reference numerals are used for the same parts as those of the conventional hydraulic circuits C ₂ and C ₃ .

Similar to the conventional hydraulic circuits C ₂ and C ₃ , the hydraulic circuit C _{1 according} to the present invention includes four motor pipes L ₁ , 4 for the main pipe L _{0 on} which the pressure of one hydraulic pump A acts. L ₂ , L ₃ , L ₄ are connected in parallel, and one reversible hydraulic pump A is incorporated in the main line L ₀ so as to form one “drive loop circuit” as a whole. The four hydraulic motors MF and MB, each consisting of two hydraulic motors MF and two rear-wheel hydraulic motors MB, are incorporated in the motor lines L ₁ , L ₂ , L ₃ and L ₄ , respectively. It is. The main line L ₀ that forms a loop is a first main line L _{01 that} is discharged from the hydraulic pump A and flows pressure oil to the inlets of the hydraulic motors MF and MB when the airframe moves forward, and the hydraulic lines MF and MB. It comprises a second main line L ₀₂ for flowing the pressure oil flowing out from the outlet to the inlet of the hydraulic pump A.

Flow pressure oil to the second main pipe line L ₀₂ two motors line L ₁ of, L ₂ and each motor line two for the rear wheels L _3, L ₄ for the front wheels in the second main pipe line L ₀₂ At the position that bisects along the direction, the flow of the hydraulic oil flowing out from the hydraulic motor MB on the rear wheel side toward the hydraulic pump A on the front wheel side with respect to the time of forward movement of the fuselage is allowed, A check valve V ₁ for preventing the reverse flow is incorporated. The check valve V ₁ moves behind an “idle loop circuit” that is different from the “drive loop circuit” formed in each of the motor lines L ₁ and L ₂ on the front wheel side when the slope of the slope becomes large. This is a valve that can be formed in each of the motor lines L ₃ and L ₄ on the wheel side. Further, the motor lines L ₁ , L ₂ , L ₃ , L ₄ for the front wheels and the rear wheels are arranged along the flow direction of the pressure oil discharged from the hydraulic pump A in the main line L ₀ forming the loop. a portion bisecting the, moreover downstream side of the first manual switching valve V ₄ of the check valve V ₁ and below the second main pipe line L ₀₂ through which the pressurized oil towards the hydraulic pump a at the time of forward movement of the aircraft Is connected to a switching valve line L _{5 in} parallel with each of the motor lines L ₁ , L ₂ , L ₃ , L _{4. The} switching valve line L ₅ is connected to the switching valve line L _5. An automatic switching valve V ₂ that opens and closes L ₅ is incorporated. Automatic switching valve V ₂ is allowed to act second main pipe line the pressure of the check both sides of the valve V ₁ of the L ₀₂ P _3, P _4, which are separated by the check valve V ₁ as a pilot pressure, with its own The valve selects either the open passage 1 or the closed passage 2 according to the relationship between the return pressure Ps of the return spring S and the pressures P ₃ and P ₄ .

Further, a portion of the main line L ₀ on the rear wheel side of the check valve V ₁ is in parallel with each of the motor lines L ₁ , L ₂ , L ₃ , L ₄ and the switching valve line L ₅ . The relief valve pipe L ₆ is connected, and the relief valve V ₃ is incorporated in the relief valve pipe L ₆ . Relief valve V _3, when the holding pressure of the rear wheel WB with gradient increases is greater in the downlink slope, the pressure of the portion of the rear wheel side of the check valve V ₁ in the second main pipe line L ₀₂ (holding pressure ) and P _3, Teisashiki relief opening when the pressure difference between the pressure P ₂ of the first manual switching part of the rear wheel side of the valve V ₄ will be described later in the first main pipe line L ₀₁ has exceeded the set value a valve is provided with an adjusting spring 3 for adjusting the pressure difference if the valve V ₃ is opened.

The hydraulic circuit C _{1 according} to the present invention incorporates first and second manual switching valves V ₄ and V _{5 for} manually switching between the “all-wheel drive system” and the “front wheel drive system”. ing. The first manual switching valve V ₄ is incorporated in the first main line L ₀₁ , and the check valve 4 that prevents the pressure oil discharged from the hydraulic pump A from flowing to the rear wheel side when the aircraft is moving forward, An open passage 5 that allows similar pressure oil to flow to the rear wheel side is provided, and either one is selected by electromagnetic force. Further, the second manual switching valve V ₅ is a pressure at a portion on the rear wheel side of the check valve V _{1 of} the second main pipe line L ₀₂ forming the “idle loop circuit” in the “front wheel drive system” state. with P ₃ is prevented from acting on the automatic switching valve V ₂ as the pilot pressure, in the state of "all wheel drive system", in the valve for the pilot pressure to switch to act on the automatic switching valve V ₂ Thus, a drain passage 7 and an open passage 8 communicating with the tank 6 are provided, and one of them is selected by electromagnetic force. In FIG. 1, P ₁ indicates the pressure in the front wheel side portion of the first main pipeline L ₀₁ relative to the first manual switching valve V ₄ . For each of the first and second manual switching valves V ₄ and V ₅ , the former check valve 4 and the latter drain passage 7 are simultaneously in an “operating state”, and the former opening passage 5 and the latter opening passage. At the same time, “8” is the “action state”. Further, the check valve 4 constituting the first manual switching valve V ₄ serves to shut off the first main pipeline L ₀₁ and has an advantage of less oil leakage when the pipeline is shut off. A valve (closed passage) may be used.

Next, with reference to FIG. 2 thru | or FIG. 10, the drive system in the case of performing a lawn mowing operation | work in the various driving | running | working state of a lawn mower regarding the combination of a flat ground or an inclined ground and the advance or reverse of a body is demonstrated one by one. 2 to 10, the magnitude of the pressure in each part of the pipeline of the hydraulic circuit C ₁ is indicated (distinguished) by the thickness of the line. The thickness of this line is the same in the drawing. Only the relative difference in size is displayed, and the difference in pressure is not considered in relation to other drawings, and the front wheel WF and the rear wheel WB are not shown. Absent.

[Advance on flat ground by driving two front wheels]
FIG. 2 is a hydraulic circuit diagram in the case of traveling forward with two-wheel drive of the front wheels without performing lawn mowing work on a flat ground. In the case of this flat ground traveling, the check valve 4 of the first manual switching valve V ₄ is set to the “operating state” and the drain passage 7 of the second manual switching valve V ₅ is set to the “operating state”. Drive. In this case, the pressure oil discharged from the hydraulic pump A is blocked by the check valve 4 of the first manual switching valve V ₄ in the first main line L ₀₁ , and on the side of each hydraulic motor MB for the rear wheels. The pressure oil that does not flow and that flows out from each front wheel hydraulic motor MF is blocked by the check valve V ₁ in the second main line L _{02 and} does not flow to each hydraulic motor MB on the rear wheel side. In the second manual switching valve V ₅ , the drain passage 7 is in the “operating state”, and the pressure P ₄ on the front wheel side of the check valve V ₁ in the second main pipeline L ₀₂ is the automatic switching valve V _2. However, the pressure P ₃ on the rear wheel side of the check valve V ₁ in the second main line L ₀₂ does not act as a pilot pressure on the automatic switching valve V ₂ . For this reason, since the relationship of (P ₃ > Ps) is established, the open passage 1 of the automatic switching valve V ₂ is in the “operating state”. In the check valve V ₁ portion of the second main line L ₀₂ , the pressure P ₃ on the rear wheel side is smaller than the pressure P ₄ on the front wheel side, so in the check valve V ₁ portion from the rear wheel side to the front wheel side. There is no low pressure oil flowing through.

As a result, each hydraulic motor MF is connected between the motor pipes L ₁ and L _{2 in} which the hydraulic motors MF for the front wheels are incorporated and the main pipe L ₀ on the front wheel side that generates the pressures P ₁ and P _4. As a result, a “drive loop circuit” for driving each front wheel WF is formed, and each motor line L ₃ , L ₄ and each switching valve line L _{5 in} which each rear wheel hydraulic motor MB is incorporated, and pressure An “idle loop circuit” is formed in which low-pressure oil in the pipeline is circulated by each rear wheel WB that is driven to rotate between the main pipeline L ₀ on the rear wheel side that generates P ₂ and P _3. The vehicle is driven forward by the two wheels of the front wheel WF. Note that the pressures P ₂ and P ₃ on the inflow side and the outflow side of each oil passage motor MB on the rear wheel side in the “idle loop circuit” are equal, and the respective pressures P ₂ and P ₃ and the discharge side of the hydraulic pump A , And the pressures P ₁ and P ₄ of the pressure oil on the inflow side have a relationship of (P ₁ > P ₄ > P ₂ = P ₃ ).

In this way, when the vehicle moves forward on a flat ground without driving the lawn mower, a “drive loop circuit” is formed only in the main pipeline L ₀ on the front wheel side, and the main pipeline L on the rear wheel side. _{Since an} “idle loop circuit” is formed at _0, when the rotational speed of the hydraulic pump A is the same, the speed is increased compared to the four-wheel drive described later. When traveling to a part, you can move at high speed.

[Advancing and descending a gentle slope by driving two front wheels]
FIG. 3 is a hydraulic circuit diagram in a case where the front wheel is driven by a two-wheel drive and a gentle slope with a gradient α is descended forward without performing lawn mowing work. In the case where the vehicle is moving forward by driving the two front wheels on a gently sloping ground with a slope α, the ground pressure P ₁₁ of the front wheel WF is larger than that on the flat ground as compared with the case of traveling forward on a flat ground. The only difference is that the pressure P ₄ ′ on the inflow side is slightly larger than the pressure P ₄ on the flat ground (P ₁ > P ₄ ′> P ₄ ).

[Reverse on flat ground by driving two front wheels]
FIG. 4 is a hydraulic circuit diagram in a case where the vehicle travels backward on a flat ground with two-wheel drive of the front wheels without performing lawn mowing work. In this reverse travel, since the hydraulic pump A rotates in the reverse direction, the pressure oil in the “drive loop circuit” and the low pressure oil in the “idle loop circuit” are both compared to the case of traveling forward on a flat ground. Circulates in the opposite direction, and in the “drive loop circuit”, the pressure P ₄ of the pressure oil in the second main line L ₀₂ is higher than the pressure P ₁ of the pressure oil in the first main line L ₀₁ (P ₄ > P ₁ > P ₂ = P ₃ ).

[Two front wheels drive back and forth on a gentle slope]
FIG. 5 is a hydraulic circuit diagram in a case where the front wheel is driven two-wheels and a gentle slope with a gradient α is descended backward without performing lawn mowing work. In the case where the vehicle travels backward by two-wheel drive on the front wheel on a gentle slope with a slope α, the hydraulic pump A rotates in the reverse direction. ”And the low pressure oil in the“ idle loop circuit ”circulate in the opposite direction, and the pressure P ₄ of the pressure oil in the second main line L ₀₂ in the“ drive loop circuit ” The only difference is the two points (P ₄ > P ₁ ′> P ₂ = P ₃ ) that are higher than the pressure P ₁ ′ of the pressurized oil in the one main line L ₀₁ . It should be noted that the ground pressure of the front wheel WF is smaller when traveling on a gentle slope with two front wheels driven than when traveling backward on a flat ground, so the pressure oil in the first main line L ₀₁ of the “drive loop circuit” is reduced. The pressure P ₁ ′ is slightly lower than the pressure P ₁ of the pressure oil in the first main line L ₀₁ when moving backward on the flat ground (P ₁ ′ <P ₁ ).

[Advance on flat ground with four-wheel drive]
FIG. 6 is a hydraulic circuit diagram in the case of performing lawn mowing work by moving forward on flat ground with four-wheel drive. When performing lawn mowing work, the open passage 5 of the first manual switching valve V ₄ is set to the “operating state”, and the open passage 8 of the second manual switching valve V ₅ is set to the “operating state”. Drive. In this case, the pressure oil discharged from the hydraulic pump A flows through the open passage 5 of the first manual switching valve V ₄ in the first main line L ₀₁ and flows to the side of each hydraulic motor MB for the rear wheels. At the same time, the pressure oil flowing out from each hydraulic motor MB for the rear wheels passes through the check valve V ₁ in the second main line L ₀₂ and flows toward the hydraulic pump A. Further, the second manual switching valve V ₅ has the open passage 8 in the “operating state”, and the pressures P ₃ and P ₄ on both sides across the check valve V ₁ in the second main pipeline L ₀₂ are equal. , acting as a pilot pressure to the automatic switching valve V _2. Between the pressures P ₁ and P _{2 of} the first main line L ₀₁ , the pressures P ₃ and P _{4 of} the second main line L ₀₂ , and the pressure Ps of the return spring S of the automatic switching valve V ₂ , Since the relationships (P ₁ = P ₂ > P ₃ = P ₄ ) and (P ₄ <P ₃ + Ps) are established, the automatic switching valve V ₂ has the closed passage 2 in the “operating state”. the automatic switching valve V ₂ is closed.

In this way, the automatic switching valve V ₂ is closed, and the pressures P ₃ and P ₄ on both sides of the second main line L ₀₂ across the check valve V ₁ are equal, and the check valve V ₁ In order to allow only the flow of pressure oil from the rear wheel side toward the front wheel side, the pressure oil discharged from the hydraulic pump A is supplied to the motor lines L ₁ and L _{2 in} front of the first manual switching valve V _4. the flow with driving each hydraulic motor MF for the front wheels to drive the respective hydraulic motors MB for the rear wheels by a first manual switching valve V ₄ and passes through the respective motor line L _3, L ₄ flows, The pressure oil flowing out from each rear wheel hydraulic motor MB passes through the check valve V ₁ and is returned to the hydraulic pump A. For this reason, one “drive loop circuit” is formed as a whole, and four-wheel drive is performed. Due to the four-wheel drive, when the rotational speed of the hydraulic pump A is the same, the aircraft is decelerated compared to the front-wheel two-wheel drive, and the aircraft travels at a low speed suitable for lawn mowing work.

[Four wheel drive down a gentle slope]
FIG. 7 is a hydraulic circuit diagram in the case of performing lawn mowing work by moving down a gentle slope with a slope α by four-wheel drive. When a lawn mowing operation is performed with a four-wheel drive on a gentle slope with a slope α, the ground pressure P ₁₁ of the front wheel WF is larger than that on a plain compared with a case where the lawn mowing operation is performed on a flat ground. The pressures P ₃ ′ and P ₄ ′ of the second main pipeline L ₀₂ are slightly higher than the pressure P ₄ on the flat ground (P ₁ > P ₃ ′ = P ₄ ′> P ₃ = P ₄ ). However, everything else is the same as when mowing on a flat ground. Note that, on a gentle slope with a slope α, the pressure P ₁ on the discharge side of the hydraulic pump A is maintained higher than the pressure P ₄ ′ on the inflow side, as in the case of flat ground. No "holding pressure" has occurred.

[Four-wheel drive to move forward and down a steep slope]
FIG. 8A is a hydraulic circuit diagram in a state where the four-wheel drive is maintained when the lawn mowing operation is performed by moving forward on a steep slope with a slope β by four-wheel drive. When shifting from a gentle slope with a slope α to a steep slope with a slope β larger than the slope α, and moving forward with a four-wheel drive and going down the steep slope, the ground pressure P ₁₁ of the front wheel WF and the rear wheel Since the difference between the ground pressure P _{12 of} WB and the ground pressure P ₁₂ increases, and the action of lowering the steeply inclined surface due to its own weight (gravity action) increases, the discharge-side pressure P ₁ and the inflow-side pressure P of the hydraulic pump A The relationship with ₄ is reversed, the pressure P ₄ on the inflow side becomes larger than the pressure P ₁ on the discharge side, and “holding pressure” is generated in the hydraulic circuit. Even if this “holding pressure” is generated, the relationship in which the pressures P ₃ and P ₄ on both sides of the second main line L ₀₂ across the check valve V ₁ are equal is the same as before the “holding pressure” is generated. Therefore, while the “holding pressure” is small, the high-pressure oil that causes the generation of the “holding pressure” continues to flow from the rear wheel side toward the front wheel side of the check valve V ₁ .

Then, when the gradient of the steep slope is further increased to reach the gradient γ (α <β <γ), the “holding pressure” is further increased, and the second main pipe line L ₀₂ acting on the check valve V ₁ is increased. the pressure P ₄ is further increased, the pressure difference [P ₃ -P ₂ between the pressure P ₃ of the second main pipe line L ₀₂ acting on the relief valve V ₃ and the pressure P ₂ of the first main pipe line L ₀₁ (= P _1)] is, when the relief valve V ₃ reaches the set pressure P ₁₀ which starts operation, the relief valve V ₃ is opened. FIGS. 8B and 8C are hydraulic circuit diagrams before and after switching from four-wheel drive to front-wheel two-wheel drive when performing lawn mowing work by moving forward on a steep slope with a gradient γ by four-wheel drive. is there. Here, the “set pressure P ₁₀ ” at which the relief valve V ₃ starts operating increases the ground slope P ₁₂ of the rear wheel WB due to the increase in the slope of the steep slope, and the “slip” is applied to the rear wheel WB. Is the pressure difference between the pressure P ₃ in the second main line L ₀₂ (oil pressure acting on the rear wheel WB as a holding pressure) and the pressure P _{2 in} the first main line L ₀₁ immediately before the occurrence of “ In each riding lawn mower, the slope of the slope at the time when the rear wheels start “sliding” is determined in advance from known data such as the weight of the aircraft, the center of gravity of the aircraft, and the frictional resistance of the rear wheels against the grass surface. Therefore, the “set pressure” can be set corresponding to each lawnmower, and this “set pressure” can be adjusted by the adjustment spring 3 of the relief valve V ₃ .

Then, when the relief valve V ₃ is opened and pressure oil flows into the relief valve pipe L ₆ from the second main pipe L ₀₂ toward the first main pipe L ₀₁ , the rear wheel side first main pipe L ₀₁ is reached. And the second main pipe line L ₀₂ communicate with each other, and the pressure P ₄ in the second main pipe line L ₀₂ on the front wheel side is kept at a high pressure by the check valve V ₁ , thereby generating a “holding pressure”. The high pressure P ₃ in the second main line L ₀₂ on the rear wheel side that has been reduced rapidly decreases to the pressure P ₂ in the first main line L ₀₁ on the rear wheel side (the pressure P ₂ is Equivalent to the pressure P _{1 of} the first main line L ₀₁ ). In this way, when the pressure P ₃ in the second main line L ₀₂ on the rear wheel side decreases, the check valve V ₁ acting as a pilot pressure on the automatic switching valve V ₂ is sandwiched between the second main lines L _{02 on} both sides. When the difference between the pressures P ₃ and P ₄ becomes large and the relationship of (P ₄ > P ₃ + Ps) is established, the open passage 1 of the automatic switching valve V ₂ becomes “active state”, The automatic switching valve V ₂ is opened to form an “idle loop” (see FIG. 8C).

As a result, the relationship of (P ₄ > P ₁ = P ₂ = P ₃ ) is established, and as shown in FIG. 8C, the “drive loop circuit” on the front wheel side and the “idle loop circuit on the rear wheel side” Until the point at which there is no risk of “slip” due to an increase in the ground pressure of the rear wheel WB due to a decrease in the slope γ of the slope (see FIG. 14B). The “circuit” and the “idle loop circuit” coexist and “front wheel two-wheel drive” is maintained. On the other hand, in the state of “front wheel two wheel drive”, when the slope of the slope becomes small and the oil pressure acting on the front wheel WF changes from the holding pressure to the driving pressure, [P ₄ <Ps + P ₃ (= P ₂ = P ₁ ) ] Is established, and the automatic switching valve V ₂ is closed. As a result, a flow of pressure oil from the rear wheel side to the front wheel side occurs in the check valve V ₁ , and the flow returns to “four-wheel drive”.

Thus, in the state of “4-wheel drive”, when performing lawn mowing work on a slope having a large gradient that causes “slip” of the rear wheel in a forward direction, immediately before “slip” occurs on the rear wheel. Automatically switches from “4-wheel drive” to “front-wheel 2-wheel drive”, and an “idle loop circuit” is formed on the rear wheel side, so that the rear wheel WB becomes smaller without slipping on a steep slope. The low pressure oil in the “idle loop circuit” is circulated by the ground pressure P ₁₂ and the slope of the slope is reduced in the “front wheel two-wheel drive” state, and the oil pressure acting on the front wheel WF is reduced. When the holding force changes to the driving force, it is automatically returned to “four-wheel drive”. In a state where the “idle loop” is formed on the rear wheel side, the rear wheel WF is steerable because it is driven and rotated by the ground pressure P ₁₂ without causing “slip”. For this reason, when a lawn mowing operation is performed by moving forward on a slope with a large gradient that causes a “slip” of the rear wheel, the “two front wheels” are selected only in the portion of the large gradient that causes the “slip” of the rear wheel. All parts that are driven by "drive" and are not likely to cause "slip" are driven by "four-wheel drive", so lawn mowing is performed by "front-wheel two-wheel drive", which is faster than "four-wheel drive" The length of the part where the work is performed can be reduced to the minimum necessary length, and the lawn on the slope can be cut off beautifully (see FIG. 15).

Also, the automatic switching valve V ₂ is opened, and the “idle loop circuit” is formed on the rear wheel side because the front wheel side pilot pressure acting on the automatic switching valve V ₂ after the relief valve V ₃ is opened. After the difference between P ₄ and the pilot pressure P ₃ on the rear wheel side increases to a certain level or more, and after the relief valve V ₃ operates until the automatic switching valve V ₂ operates, the rear wheel WB The driving force of the vehicle is gradually reduced within a short period of time and switched from “4-wheel drive” to “front-wheel 2-wheel drive”. As a result of being able to limit to the limit, it is possible to clean the lawn on the sloping ground, and there is almost no impact force acting on the fuselage at the time of switching the driving method, and the switching of the driving method is performed smoothly, The rolling operation also becomes easy.

[Going uphill on a four-wheel drive]
FIG. 9 is a hydraulic circuit diagram in the case of performing lawn mowing work by going up a gentle slope with a slope α by four-wheel drive. In this case, the pressure oil discharged from the hydraulic pump A is supplied to each motor line L ₃ in which the rear wheel side oil line motor MB is incorporated by the check valve V ₁ incorporated in the second main line L ₀₂ . Since it is not supplied to L ₄ , a “drive loop circuit” is inevitably formed on the front wheel side, and an “idle loop circuit” is formed on the rear wheel side, resulting in “front wheel two-wheel drive”. The pressure of each portion of the tube path, a relationship of _{(P 4> P 1 = P} 2 = P 3).

[Four-wheel drive, going down and down the slope]
FIG. 10 is a hydraulic circuit diagram in the case of performing lawn mowing work by going down a gentle slope with a slope α by four-wheel drive. In this case, as in the case of going up and down on a slope with four-wheel drive, the result is that “front wheel two-wheel drive” is the same, but compared to the case of going up and down on a slope with four-wheel drive. The pressures P ₁ ′, P ₂ ′, and P ₃ ′ of the respective parts of the pipe line are (P ₄ > P ₁ ′ = P ₂ ′ = P ₃ ′, P ₁ ′) because the ground pressure of the front wheel WF is reduced. > P ₁ , P ₂ > P ₂ ′, P ₃ > P ₃ ′).

As described above, when the vehicle is moved backward while the hydraulic circuit C _{1 is set} to “four-wheel drive”, “front-wheel two-wheel drive” is performed regardless of the slope of the slope including the flat ground. Therefore, there is an advantage that the airframe travels stably.

In the first aspect of the invention, the first and second manual switching valves are not indispensable. Therefore, the first and second manual switching valves V ₄ and V ₅ are not incorporated in the hydraulic circuit C ₁ of the above embodiment. The circuit is always “4-wheel drive”. In the circuit incorporating the first and second manual switching valves V ₄ and V ₅ as in the hydraulic circuit C ₁ of the above embodiment, “front wheel two-wheel drive” and “four wheel drive” can be manually switched. By selecting “front wheel two-wheel drive”, there is an advantage that high speed traveling is possible when traveling on a portion other than the lawn surface such as a road.

1 is a hydraulic circuit diagram of an all-wheel hydraulically driven riding lawn mower having a drive system automatic switching function according to the present invention. It is a hydraulic circuit diagram in the case of traveling forward with two-wheel drive of front wheels without performing lawn mowing work on a flat ground. FIG. 5 is a hydraulic circuit diagram in a case where the front wheel is driven by two wheels and is moved forward on a gentle slope with a gradient α without performing lawn mowing work. It is a hydraulic circuit diagram in the case of traveling backward on a flat ground with two-wheel front wheel drive without performing lawn mowing work. It is a hydraulic circuit diagram in the case of descending slowly on a gentle slope with a slope α by driving two front wheels without performing lawn mowing work. It is a hydraulic circuit diagram in the case of performing lawn mowing work by moving forward on flat ground with four-wheel drive. It is a hydraulic circuit diagram in the case of performing lawn mowing work by moving forward on a gentle slope with a gradient α by four-wheel drive. FIG. 5 is a hydraulic circuit diagram in a state where four-wheel drive is maintained when performing lawn mowing work by moving forward on a steep slope with a slope β by four-wheel drive. FIG. 4 is a hydraulic circuit diagram immediately before switching to front-wheel two-wheel drive in a case where lawn mowing work is performed by moving forward on a steep slope with a gradient γ by four-wheel drive. FIG. 5 is a hydraulic circuit diagram after switching to front-wheel two-wheel drive in a case where lawn mowing is performed by moving forward on a steep slope with a gradient γ by four-wheel drive. It is a hydraulic circuit diagram in the case of performing lawn mowing work by ascending backwards on a gentle slope with a gradient α by four-wheel drive. It is a hydraulic circuit diagram in the case of performing lawn mowing work by going down a gentle slope with a slope α by four-wheel drive. It is a diagram illustrating a conventional hydraulic circuit C ₂ of the total wheel hydraulic drive riding lawn mower for a four-wheel structure. (A), (b) is a diagram showing a hydraulic circuit C ₃ of the "all wheel drive system" and "front-wheel drive system" on all wheels hydraulic drive riding lawnmower respective four wheels structure. It is a diagram showing each contact pressure P _11, P ₁₂ of the front wheel WF and the rear wheel WB in the case of performing mowing down the slope in advance. (A) and (B) are graphs showing the relationship between the contact pressure and the holding pressure of the front and rear wheels of the aircraft with respect to the slope of the slope. Each part of “four-wheel drive” and “front-wheel two-wheel drive” in the case of performing lawn mowing work with a lawn mower having a hydraulic circuit C _{1 according} to the present invention and a conventional hydraulic circuit moving forward on a sloping ground is shown. FIG.

Explanation of symbols

A: Hydraulic pump
C ₁ : Hydraulic circuit
L ₀ : Main pipeline
L ₀₁ : First main pipeline
L _02: second main pipe line L ₁ ~L _4: Motor conduit
L ₅ : Switching valve pipeline
L ₆ : Relief valve pipeline
MF: Hydraulic motor for front wheels
MB: Hydraulic motor for rear wheels
P ₁ : Pressure in the first main pipe on the front wheel side
P ₂ : Pressure in the first main pipeline on the rear wheel side
P ₃ : Pressure in the second main pipeline on the rear wheel side
P ₄ : Pressure in the second main pipeline on the front wheel side
V ₁ : Check valve
V _2: automatic switching valve
V _3: relief valve
V ₄ : First manual switching valve
V ₅ : Second manual switching valve
WF: Front wheel
WB: Rear wheel

Claims (4)

The same number of motor pipelines as the number of wheels are connected in parallel to the main pipeline, and the hydraulic motors for front wheels and rear wheels are divided into two along the direction in which the pressure oil flows in the main pipeline. Each hydraulic motor provided on each wheel is individually driven by a single hydraulic pump that is incorporated in the above-described form and is incorporated at a position where one drive loop pipeline in the main pipeline can be formed. All-wheel hydraulically driven riding lawn mower
In the main line, the pressure oil discharged from the hydraulic pump flows when the vehicle moves backward, and is installed in a position that bisects the motor lines for the front wheels and the rear wheels, from the rear wheel side to the front wheel side. A check valve that only allows the flow of pressurized oil towards
The motor pipelines for the front wheels and the rear wheels are divided into two along the direction in which the pressure oil discharged from the hydraulic pump in the main pipeline flows, and each motor pipeline is located at a position closer to the rear wheels than the check valve. And an automatic switching valve that is opened and closed by each pilot pressure taken from both sides of the check valve with the check valve interposed therebetween,
A relief valve incorporated in a relief valve pipe connected in parallel to each motor pipe and a switching valve pipe in a portion on the rear wheel side with respect to the check valve in the main pipe;
When performing lawn mowing work on an incline, the rear wheel starts to slide due to the synergistic effect of the holding pressure of the front wheel and the holding pressure of the rear wheel blocked by the check valve and the ground pressure of the lowered rear wheel. The relief valve is opened immediately before to release the holding pressure of the rear wheel, and immediately after the opening, the automatic switching valve is increased by increasing the difference between the pilot pressures on the front wheel side and the rear wheel side that act on the automatic switching valve. All wheel hydraulically driven riding lawn mower characterized in that a low pressure oil idle loop circuit is formed on the rear wheel side by automatically opening from the all wheel driving method to the front wheel driving method. Machine.   2. The all-wheel hydraulically-driven riding lawn mower according to claim 1, wherein when driving the vehicle backward, the front-wheel drive system is always used due to the action of a check valve. A first manual switching valve which is a portion where pressure oil discharged from a hydraulic pump flows when the vehicle moves forward in the main pipeline, and which is incorporated at a position that bisects the motor pipelines for front wheels and rear wheels;
A second manual switching valve that transmits or shuts off the pressure of the rear wheel side portion as a pilot pressure to the automatic switching valve with reference to the check valve in the main pipeline;
The all-wheel hydraulically-driven riding lawn mower according to claim 1 or 2, characterized by comprising:   The all-wheel hydraulically-driven riding lawn mower according to claim 3, wherein the first manual switching valve is configured to select either an open passage or a check valve.

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