JP5957735B2 - Hydraulic circuit for lifting the harvesting part of the combine - Google Patents

Description

  The present invention relates to a hydraulic circuit for raising and lowering a harvesting portion of a combine.

  Conventionally, a combine is generally equipped with a reaper that can be raised and lowered at the front of the body. For example, there is a demand for the mowing unit to move up and down at a low speed when setting the cutting height and to move up and down at a high speed after the work is finished or before the work is started. For this reason, a hydraulic circuit has been proposed that makes it possible to change the speed of a hydraulic cylinder that raises and lowers the cutting part (for example, Patent Document 1).

  The hydraulic circuit disclosed in Patent Document 1 controls the flow rate of hydraulic oil discharged from a hydraulic cylinder by selecting and operating electromagnetic open / close valves with different flow rates connected in parallel when lowering the cutting unit. When raising the part, the full flow rate of hydraulic oil from the pump is supplied to the hydraulic cylinder when rising at high speed, and bleed-off that releases part of the hydraulic oil from at least one of the electromagnetic on-off valves when rising at low speed. Switching to the circuit controls the flow rate of hydraulic oil supplied to the hydraulic cylinder.

  However, since the hydraulic circuit of Patent Document 1 controls the hydraulic cylinder by a so-called bleed-off circuit in order to raise the cutting part at a low speed, when the load applied to the cutting part increases, the pressure of the hydraulic oil is correspondingly increased. As a result, the escape flow rate increases, and as a result, the ascending flow rate decreases significantly and the ascending speed decreases significantly.

  Further, in the above hydraulic circuit, the temperature of the hydraulic oil drained from the hydraulic cylinder when rising at a low speed rises due to friction when passing through an electromagnetic on-off valve that limits the flow rate. Since the viscosity of the hydraulic oil decreases as the temperature increases, the viscosity resistance of the hydraulic oil decreases as the temperature increases, and the hydraulic oil easily passes through the electromagnetic on-off valve. On the other hand, when the load is applied to the cutting part, the pressure of the hydraulic oil also increases, so when the load is applied to the cutting part with the temperature rising, the more the load is increased, the easier it is to pass through the oil passage of the electromagnetic on-off valve. As a result, the more the load is applied to the cutting part, the greater the escape flow rate of the hydraulic oil and the less the flow rate supplied to the hydraulic cylinder. Therefore, the rising speed of the cutting part becomes slow, and the variation in the rising speed due to the load on the cutting part is large. .

  In addition, when the engine is rotating at low speed, such as when idling, the bleed-off circuit has a low discharge flow rate from the hydraulic pump, so the flow rate exceeding the escape flow rate cannot be secured and the low speed increase I can't let you.

  Furthermore, it is a configuration that changes the lifting speed of the mowing unit by selecting two electromagnetic on-off valves with different flow rates. Since the throttle for low-speed rise and low-speed drop is used in common, it is difficult to match the combine machine. There are cases.

  Therefore, in order to solve the above problems, a supply oil amount restriction throttle is connected in parallel with an openable / closable switching valve provided in the supply oil passage, and the changeover valve provided in the supply oil passage is switched to a closed state at the time of low speed rise. Thus, there has been proposed a hydraulic circuit capable of switching the hydraulic oil supplied to the hydraulic cylinder to a meter-in circuit controlled by a supply oil amount restriction throttle (Patent Document 2).

JP-A-6-113603 Japanese Patent No. 4994296

  According to the hydraulic circuit disclosed in the above-mentioned Patent Document 2, fluctuations in the ascending speed of the cutting part due to the escape flow rate of the hydraulic oil are suppressed, and an excellent effect is achieved in that the ascending speed can be increased even when the engine rotates at a low speed. However, depending on the circuit configuration, especially when idling, etc., when the hydraulic oil flow rate is low and the oil temperature is high, etc. There was a slight time lag before it started.

  Therefore, the present invention provides a hydraulic circuit for raising and lowering a harvesting part of a combine that can further improve the hydraulic circuit disclosed in Patent Document 2 and reduce a time lag that occurs when the harvesting part is lowered at high speed. Is the main purpose.

  As a result of intensive studies by the present inventors, the time lag that occurs when lowering the cutting part at high speed is the amount of hydraulic oil supplied from the hydraulic pump for lowering the speed when lowering the cutting part at high speed. It has been found that this is due to the construction of a path that drains through the restriction aperture (first aperture).

  Therefore, in order to achieve the above object, the harvesting part raising / lowering hydraulic circuit according to the present invention drives a hydraulic cylinder that raises and lowers the harvesting part of the combine with hydraulic oil sent from an oil tank via a hydraulic pump. A pilot operated check valve that allows the backflow of hydraulic oil from the hydraulic cylinder using a pilot pressure, and a supply pressure primary side port and a hydraulic cylinder hydraulic oil passage secondary side port are opened. A first position to be opened, and a second position to open the supply pressure primary side port and the secondary port for the pilot pressure hydraulic fluid passage, and to open the secondary port for the hydraulic cylinder hydraulic fluid passage and the tank port. And a first switching valve that can be switched to a third position that closes the supply pressure primary side port and the hydraulic cylinder hydraulic oil passage secondary port. A first throttle connected in parallel with the first switching valve, for limiting a flow rate of hydraulic oil supplied from the hydraulic pump to the hydraulic cylinder, and connected in series with the first throttle; A resistance valve for restricting hydraulic fluid passing through the first throttle when the first switching valve is in the second position to ensure a pilot pressure of the pilot operated check valve; and the pilot operated type A second throttle for limiting the flow rate of the hydraulic oil drained by flowing back through the check valve; and a flow passage cross-sectional area smaller than the second throttle, for limiting the flow rate of the drained hydraulic oil And a third switching valve, and a second switching valve capable of selectively switching an oil passage for drained hydraulic oil to an oil passage for draining hydraulic fluid through the third throttle. To do.

  The pilot operated check valve includes a check valve body, a seat from which the check valve body can be separated, a spring that presses and urges the check valve body against the seat, and the check valve body and the seat. It is preferable to provide a pilot piston which is slidably disposed opposite to each other.

  According to the present invention, the hydraulic oil from the hydraulic pump is drained through the first throttle by connecting the resistance valve in series with the first throttle that restricts the hydraulic oil flow rate and raises the cutting part at a low speed. The pilot-operated check valve is opened by pilot operation before starting operation, so pilot pressure can be quickly supplied to the pilot-operated check valve even when the flow rate of hydraulic oil is low, such as when idling. Since the operation type check valve is opened, the time lag at the time of the high-speed lowering operation of the cutting part can be reduced.

It is a side view which shows the principal part of a general combine. 1 is a hydraulic circuit diagram showing one embodiment of a hydraulic circuit for raising and lowering a harvesting part of a combine according to the present invention. It is principal part sectional drawing which shows the hydraulic circuit block unit in which the hydraulic circuit of FIG. 2 was integrated. It is a hydraulic circuit diagram which shows the change aspect of the harvesting part raising / lowering hydraulic circuit of the combine which concerns on this invention. It is a hydraulic circuit diagram which shows the other change aspect of the hydraulic circuit for the harvesting part raising / lowering of the combine which concerns on this invention.

  DESCRIPTION OF EMBODIMENTS Embodiments of a hydraulic circuit for lifting and lowering a harvesting portion of a combine according to the present invention will be described below with reference to FIGS. In addition, the same code | symbol was attached | subjected to the same component through all the figures and all the Examples.

  First, the general configuration of the combine will be described. As shown in FIG. 1, a general combine includes a cutting unit 1 at the front, and the cutting unit 1 moves up and down by driving a hydraulic cylinder 2. The hydraulic cylinder 2 can be a single-acting hydraulic cylinder.

  FIG. 2 is a hydraulic circuit diagram showing an embodiment of the hydraulic circuit for raising and lowering the harvesting part of the combine according to the present invention.

  The hydraulic circuit basically supplies hydraulic oil from the oil tank 3 to the piston chamber 2a of the hydraulic cylinder 2 by the hydraulic pump 4, moves the piston 2b, and is connected to the piston rod 2c (see FIG. 1). 1), the piston 2b is returned to its original position and the cutting part 1 is lowered by draining the hydraulic oil in the piston chamber 2a to the oil tank 3.

  Between the hydraulic pump 4 and the hydraulic cylinder 2, in order from the hydraulic pump 4, an oil passage 5a, an electromagnetic switching valve 6, an oil passage 5b, a first switching valve 7, an oil passage 5c, and a pilot operated check valve 11 are arranged. The oil passage 5d, the slow return valve 12, and the oil passage 5e are connected, and the bypass oil passage 8 is connected to the oil passage 5b and the oil passage 5c, and the first switching valve 7 is interposed in the bypass oil passage 8. A first throttle 9 connected in parallel and a resistance valve 10 connected in series with the first throttle 9 are connected to the bypass oil passage 8.

  The resistance valve 10 is a kind of sequence valve, and opens the bypass oil passage 8 when the primary bypass oil passage 8 exceeds a set pressure. The pilot operated check valve 11 includes an external pilot port, and when hydraulic fluid having a predetermined pilot pressure is supplied to a pilot pressure hydraulic fluid passage 11a that communicates with the external pilot port, the check valve main body 11b of the pilot operated check valve 11 is provided. Open (see Fig. 3) and allow backflow of hydraulic oil. The set pressure of the resistance valve 10 is set higher than the pilot pressure of the pilot operated check valve 11. The slow return valve 12 includes a check valve 12a and a second throttle 12b connected in parallel to the check valve 12a.

  The term “throttle” refers to a mechanism that reduces the cross-sectional area of the flow and provides resistance in the oil passage or fluid passage, and includes a fixed throttle, a variable throttle, a throttle valve, a throttle switching valve, and the like.

  In the illustrated example, the electromagnetic switching valve 6 is an open center 4-port 3-position switching valve including a pair of solenoids 6a, 6b and springs 6c, 6d. In the non-excited state, the electromagnetic switching valve 6 is in the neutral position shown in FIG. 2 due to the balance of the springs 6c and 6d. In the neutral position, the hydraulic oil pumped from the hydraulic pump 4 to the oil passage 5a is drained to the oil tank 3 through the oil passages 13a, 13b, and 14. When one solenoid 6a is excited, the oil passages 5a and 5b are opened. When the other solenoid 6b is energized, the oil passage 5a and the oil passage 15 are opened, and the hydraulic oil pressure-fed from the hydraulic pump 4 to the oil passage 5a passes through the oil passage 15 through the Glen tank elevator or auger mounted on the combine. It is supplied to a hydraulic actuator (not shown) that drives other work equipment such as a lifting unit.

  In the illustrated example, the first switching valve 7 is a solenoid valve including a pair of solenoids 7a and 7b and a pair of springs 7c and 7d, and is used for a supply pressure primary side port P, a tank port T, and a pilot pressure hydraulic fluid path. It is a 4 port 3 position switching valve of a pump closed center provided with the secondary side port A and the secondary side port B for hydraulic-cylinder hydraulic fluid paths. When the solenoids 7a and 7b are not energized, the first switching valve 7 is biased to a neutral position (position shown in FIG. 2) that closes the port PB between the oil passages 5b and 5c by the springs 7c and 7d. Has been. By energizing one solenoid 7a, the first switching valve 7 is switched from the neutral position to a position where the oil path from the port P to the port B is opened between the oil paths 5b and 5c. When the other solenoid 7b is excited, the oil passage from the port P to the port A is opened and the oil passage from the port B to the port T is opened.

  A relief valve 16 as a pressure control valve is connected to an oil passage 5 a between the hydraulic pump 4 and the electromagnetic switching valve 6. The relief valve 16 drains part of the hydraulic oil to the oil tank 3 through the oil passages 17 and 14 when the hydraulic oil pumped from the hydraulic pump 4 to the oil passage 5a exceeds the set pressure, The pressure of the hydraulic fluid to be supplied is kept constant.

  An oil passage 14 connected to the oil tank 3 is connected to an oil passage 5 d connected to the secondary port (the hydraulic cylinder 2 side) of the pilot operated check valve 11. A third throttle 18 and a second switching valve 19 for opening and closing the flow of hydraulic oil drained from the third throttle 18 to the oil tank 3 are interposed in the oil passage 14. The third throttle 18 has a smaller channel cross-sectional area than the second throttle 12b built in the slow return valve 12. The second switching valve 19 is an electromagnetic two-position switching valve, and is energized to the position of a check valve that closes the oil passage 14 by a spring 19a when not energized, and the oil passage 14 is energized by exciting the solenoid 19b. Can be switched to the position to open.

  In the pilot operated check valve 11, the solenoid 6a of the electromagnetic switching valve 6 and the solenoid 7b of the first switching valve 7 are excited, and hydraulic oil from the oil passage 5b is supplied as pilot pressure through the pilot pressure hydraulic oil passage 11a. Then, the built-in check valve is pushed open to allow backflow of hydraulic oil. The hydraulic fluid that has flowed back through the pilot operated check valve 11 is drained to the oil tank 3 through the oil passage 5 c, the first switching valve 7 (ports B and T), the oil passage 20, and the oil passage 14.

  The hydraulic circuit is built in the hydraulic circuit block unit 21. FIG. 3 is a cross-sectional view showing a main part of the hydraulic circuit block unit 21 in which the hydraulic circuit is incorporated.

  As shown in FIG. 3, the resistance valve 10 is seated on a seat 8 a formed in a step portion in the oil passage 8 by a rod-shaped valve body 10 a being pushed by a spring 10 b. When hydraulic oil is supplied to the primary side of the oil passage 8 and the primary pressure exceeds the set pressure, the valve body 10a is separated from the seat 8a, and the hydraulic oil flows through the oil passage 8 to the oil passage 5c. When the valve body 10a is separated from the seat 8a, the separation distance from the seat 8a is regulated by the spring force of the spring 10b.

  Referring to FIG. 3, the pilot operated check valve 11 includes a check valve body 11b, a seat 11c, a spring 11d that presses the check valve body 11b against the seat 11c, and a pilot piston 11e. The pilot piston 11e is disposed so as to face the check valve main body 11b via the seat 11c, and is slidable in the left and right directions in FIG. When the hydraulic oil is supplied to the pilot pressure hydraulic oil passage 11a, the pilot piston 11e is pushed to the right in FIG. 3, and the rod portion 11g passes through the oil passage hole of the seat 11c and resists the pressing force of the spring 11d. Then, the check valve 11b is pushed to the right in FIG.

  When hydraulic oil is supplied to the oil passage 5b from a hydraulic pump (not shown), it is supplied to the oil passage 8 and the oil passage 11a. The resistance valve 10 provides resistance to the hydraulic oil passing through the oil passage 8 to ensure a pilot pressure necessary for opening the pilot operated check valve 11 even when the hydraulic oil supply flow rate is small, The pilot piston 11e is designed so that the valve body 10a of the resistance valve 10 is separated from the seat 8a after the check valve body 11b is separated from the seat 11c.

  In the hydraulic circuit of the first embodiment having the above-described configuration, when the cutting unit 1 is raised at high speed, the solenoid 6a of the electromagnetic switching valve 6 is excited to open between the oil passages 5a and 5b, and the first switching is performed. The solenoid 7a of the valve 7 is excited to open between the ports PB between the oil passages 5b and 5c. As a result, from the hydraulic pump 4, the oil passage 5a, the electromagnetic switching valve 6, the oil passage 5b, the first switching valve 7 (ports P and B), the oil passage 5c, the pilot operated check valve 11, the oil passage 5d, Hydraulic oil is supplied to the hydraulic cylinder 2 through the slow return valve 12 and the oil passage 5e. At this time, when the hydraulic oil reaches a predetermined pressure, the resistance valve 10 is opened and the bypass oil passage 8 also passes. However, since the flow rate is restricted by the first throttle 9, the hydraulic oil passes through the bypass oil passage 8. The flow rate of the working oil is smaller than the flow rate of the working oil passing through the first switching valve 7. At this time, the port AT connecting the oil passage 11a and the oil passage 20 is also opened. Referring to FIG. 3, the pilot piston 11e is pushed to the left in FIG. 3 by the hydraulic oil passing through the oil passage 5c. The hydraulic oil in the pilot pressure hydraulic oil chamber 11f of the pilot piston 11e is drained through the oil passage 11a and the oil passage 20.

  Next, when the mowing unit 1 is raised at a low speed, the solenoid 6a of the electromagnetic switching valve 6 is excited to open the port between the oil passages 5a and 5b, and the first switching valve 7 is not excited. As a neutral position, and the port PB between the oil passages 5b and 5c is closed. As a result, from the hydraulic pump 4, the oil passage 5a, the electromagnetic switching valve 6, the oil passage 5b, the first throttle 9 and the resistance valve 10 of the bypass oil passage 8, the oil passage 5c, the pilot operated check valve 11, the oil passage The hydraulic oil is supplied to the hydraulic cylinder 2 through 5d, the slow return valve 12, and the oil passage 5e. In this case, except for the amount drained from the relief valve 16, the entire flow rate of the hydraulic oil from the hydraulic pump 4 passes through the first throttle 9 via the bypass oil passage 8, so that the hydraulic oil supplied to the hydraulic cylinder 2 The flow rate is limited by the first throttle 9, and the ascending speed of the cutting unit 1 is reduced as compared with the case of the high speed increase.

  When the mowing unit 1 is lowered at high speed, the solenoid 6a of the electromagnetic switching valve 6 is excited to switch to a position where the oil passages 5a and 5b are opened, and the solenoid 7b of the first switching valve 7 is excited. The port PA is opened to communicate with the oil passage 5b and the pilot pressure hydraulic fluid passage 11a, and the port BT is opened to connect the oil passage 5c and the oil passage 20 to be drained to the oil tank 3. Switch to position. As a result, the hydraulic oil supplied to the pilot pressure hydraulic oil passage 11a acts as a pilot pressure through the oil passage 20, opens the check valve body 11b in the pilot operated check valve 11, and allows backflow of the hydraulic oil. To do. In this way, the hydraulic oil in the piston chamber 2a of the hydraulic cylinder 2 flows back through the oil passage 5e, the second throttle 12b of the slow return valve 12, the oil passage 5d, the pilot operated check valve 11, and the oil passage 5c. Then, the oil is drained from the first switching valve 7 (ports B and T) to the oil tank 3 through the oil passages 20 and 14. The drain flow rate of the hydraulic oil drained to the oil tank 3 is limited by the second throttle 12b.

  When lowering the cutting part 1 at a low speed, the solenoid 19b of the second switching valve 19 is excited to open the oil passage 14. As a result, the hydraulic oil accumulated in the piston chamber 2 a of the hydraulic cylinder 2 passes through the oil passage 5 e, the second throttle 12 b of the slow return valve 12, and the third throttle 18 interposed in the oil passage 14, so that the oil tank 3 is drained. Since the third throttle 18 has a smaller channel cross-sectional area than the second throttle 12 b, the flow rate flowing through the oil passage 14 is determined by the third throttle 18. The electromagnetic switching valve 6 is in a neutral position, and at this time, the hydraulic oil from the hydraulic pump 4 is drained to the oil tank 3 through the oil passages 13a, 13b, and 14.

  As described above, when the mowing unit 1 is raised at a low speed, the piston moving speed of the hydraulic cylinder 2 is reduced by limiting the flow rate of the hydraulic oil by the first throttle 9. Therefore, when the mowing unit 1 rises at a low speed, unlike the conventional bleed-off circuit, the hydraulic cylinder 2 can be driven by switching to the meter-in circuit, so that fluctuation due to the escape flow rate can be suppressed. Even if the flow rate of the hydraulic oil is limited by the first throttle 9, the pressure on the primary side of the first throttle 9 is adjusted by the relief valve 16, so that the hydraulic oil that passes through the first throttle 9 is adjusted. Flow rate fluctuations are prevented.

  Since the hydraulic pump 4 is driven by an engine (not shown), the discharge flow rate of the hydraulic pump decreases when the engine rotates at a low speed, for example, when idling or during wetland driving. Even when trying to raise the mowing part at a low speed when the engine is rotating at a low speed, the bleed-off circuit has a small discharge flow rate from the hydraulic pump, so it cannot secure a flow rate that exceeds the escape flow rate, and cannot rise at a low speed. In the present invention, when the engine is rotating at a low speed, even if a part of the hydraulic oil is drained from the relief valve 16, the relief pressure of the hydraulic oil is secured, so that the low speed increase is possible.

  In addition, since the first throttle 9 for limiting the amount of supply oil is separated from the second and third throttles 12b and 18 for limiting the drain flow rate, matching with the combine main unit is facilitated.

  Further, when the mowing unit 1 is lowered at a high speed as described above, in the conventional hydraulic circuit configuration that does not include the resistance valve 10 which is a characteristic part of the present invention, the hydraulic oil supplied from the hydraulic pump 4 to the oil passage 5b is Since a path for draining to the oil tank 3 through the oil path 8, the first throttle 9, the oil path 5c, the port BT of the first switching valve 7, the oil path 20, and the oil path 14 is formed, particularly the engine. When the flow rate of hydraulic fluid input at idling or the like is small, a time lag occurs when the pilot operated check valve 11 is opened. However, in the present invention, by providing the resistance valve 10, the pilot operated check valve 11 is provided. Since the pilot pressure required to open the valve can be generated immediately, the time lag can be reduced.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea of the present invention.

  For example, as shown in FIG. 4, instead of the slow return valve 12 of the first embodiment, a second throttle 12b can be provided in the oil passage 20, and further, as shown in FIG. A circuit configuration is also possible in which a second switching valve 19A is provided on the drain tank 3 side of the 20 second throttle 12b, and the third throttle 18 is connected in parallel with the second switching valve 19A.

DESCRIPTION OF SYMBOLS 1 Cutting part 2 Hydraulic cylinder 3 Oil tank 4 Hydraulic pump 7 1st switching valve 9 1st throttle 10 Resistance valve 11 Pilot operation type check valve 12b 2nd throttle 18 3rd throttle 19, 19A 2nd switching valve

Claims (2)

A hydraulic circuit for driving a hydraulic cylinder that raises and lowers a harvesting portion of a combine with hydraulic oil sent from an oil tank via a hydraulic pump,
A pilot operated check valve that allows the backflow of hydraulic oil from the hydraulic cylinder using pilot pressure; and
A first position for opening the supply pressure primary side port and the hydraulic cylinder hydraulic fluid passage secondary port, and opening the supply pressure primary port and the pilot pressure hydraulic passage secondary port and the hydraulic pressure Switching between the second position for opening the secondary port for the cylinder hydraulic fluid passage and the tank port and the third position for closing the secondary port for the hydraulic pressure hydraulic hydraulic fluid passage and the secondary port for the hydraulic cylinder hydraulic fluid passage A possible first switching valve;
A first throttle connected in parallel with the first switching valve for limiting a flow rate of hydraulic oil supplied from the hydraulic pump to the hydraulic cylinder;
When connected in series with the first throttle and the first switching valve is in the second position, the hydraulic oil passing through the first throttle is regulated to control the pilot pressure of the pilot operated check valve. A resistance valve to ensure,
A second throttle for limiting the flow rate of the drained hydraulic fluid by flowing back through the pilot operated check valve;
A third throttle for limiting the flow rate of the drained hydraulic oil, having a smaller channel cross-sectional area than the second throttle;
A second switching valve capable of selectively switching a drained hydraulic oil passage to a drained hydraulic fluid passage through the third throttle;
With
A hydraulic circuit in which a set pressure of the resistance valve is larger than a pilot pressure of the pilot operated check valve . The pilot operated check valve includes a check valve body, a seat from which the check valve body can be separated, a spring that presses and urges the check valve body against the seat, and the check valve body and the seat. The hydraulic circuit according to claim 1, further comprising a pilot piston that is slidably disposed opposite to the pilot circuit.

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