JP2009185834A - Hydraulic travelling vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic travelling vehicle for preventing the occurrence of cavitation in a hydraulic circuit not only during normal travel with an engine in driving operation but also during traction with the engine stopped. <P>SOLUTION: The hydraulic travelling vehicle includes a travelling hydraulic pump 6 driven by the engine 2 to discharge operating oil, a travelling hydraulic motor 8 connected to the travelling hydraulic pump 6 via a closed circuit 30, and adapted to be driven by the hydraulic pressure of the operating oil discharged from the travelling hydraulic pump 6, a charge pump 12 driven by the drive of the travelling hydraulic pump 6 to resupply the operating oil to the closed circuit 30, an auxiliary hydraulic pump 16 driven by the rotation of driving wheels 50, 50 to discharge the operating oil sucked from an operating oil tank, a steering mechanism 18 operated by the supply of the operating oil discharged from the auxiliary hydraulic pump 16, and a resupply oil path 20 for carrying the operating oil discharged from the steering mechanism 18 after used in the steering mechanism 18 to the closed circuit 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic traveling vehicle.

  2. Description of the Related Art Conventionally, a hydraulic traveling vehicle using an HST traveling system in which a traveling hydraulic motor is driven by hydraulic pressure supplied from a traveling hydraulic pump driven by an engine and a driving wheel is rotated by driving the traveling hydraulic motor. Is known (see, for example, Patent Document 1).

In the hydraulic traveling vehicle disclosed in Patent Document 1, a traveling hydraulic pump and a traveling hydraulic motor are connected in a closed circuit, and hydraulic fluid is circulated in the closed circuit by the traveling hydraulic pump when the vehicle is traveling. The driving hydraulic motor is driven. The closed circuit is provided with various valves such as a flushing valve, and minute hydraulic oil leaks when the valve is operated or when the traveling hydraulic motor is driven. For this reason, a charge pump driven by the engine is connected to the closed circuit, and cavitation occurs in the closed circuit due to leakage of the hydraulic oil by supplying hydraulic oil from the charge pump to the closed circuit. Is to be prevented.
JP 2003-194182 A

  However, in the hydraulic traveling vehicle disclosed in Patent Document 1, cavitation may occur in the closed circuit when the engine stops and the traveling vehicle is towed by a towing vehicle.

  That is, in the hydraulic traveling vehicle of Patent Document 1, when the engine is stopped, the charge pump is also stopped, and the closed circuit is not supplied with hydraulic oil. On the other hand, when the driving wheel rotates by pulling the traveling vehicle, the traveling hydraulic motor is driven in accordance with the rotation, and hydraulic oil flows in the closed circuit, and a minute amount of hydraulic oil leaks from the closed circuit. Occurs. When the towing vehicle is towed for a long time, towed at a high speed, or towed many times, the total amount of hydraulic fluid leakage increases, and the closed circuit Cavitation occurs in Such cavitation may cause damage to each hydraulic device connected to the closed circuit.

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is not only during normal traveling when the engine is driven but also when the engine is stopped in a hydraulic traveling vehicle. This is to prevent cavitation from occurring in the hydraulic circuit even at times.

  In order to achieve the above object, the invention according to claim 1 is a traveling hydraulic pump that is driven by an engine and discharges hydraulic fluid, and is connected to the traveling hydraulic pump in a closed circuit, and the traveling hydraulic pump A traveling hydraulic motor that rotates the driving wheel by being driven by the hydraulic pressure of the hydraulic oil discharged from the vehicle, and a charge pump that is driven in accordance with the driving of the traveling hydraulic pump and replenishes the closed circuit with the hydraulic oil An auxiliary hydraulic pump that is driven as the drive wheel rotates and sucks and discharges hydraulic oil from a hydraulic oil tank, and hydraulic oil discharged from the auxiliary hydraulic pump An operating mechanism that operates by being supplied, and a replenishment oil passage for flowing the operating oil discharged from the operating mechanism to the closed circuit after being used in the operating mechanism. It is intended to.

  In the first aspect of the present invention, the hydraulic oil can be supplied from the charge pump to the closed circuit connected to the traveling hydraulic motor during normal traveling when the engine of the hydraulic traveling vehicle is driven. Occurrence of cavitation in the closed circuit due to leakage of hydraulic oil from the closed circuit due to driving of the traveling hydraulic motor or the like can be prevented. On the other hand, when a hydraulic traveling vehicle with the engine stopped is towed, an auxiliary hydraulic pump provided in the hydraulic traveling vehicle is driven as the drive wheel rotates to discharge the hydraulic oil sucked from the hydraulic oil tank. In addition, after the discharged hydraulic oil is used in the operating mechanism, it is allowed to flow through the replenishing oil passage to the closed circuit, and even when the hydraulic traveling vehicle in which the engine is stopped is towed. The closed circuit can be supplemented with hydraulic oil to prevent cavitation. Therefore, according to the first aspect of the present invention, in the hydraulic traveling vehicle, cavitation is prevented from occurring in the hydraulic circuit not only during normal traveling when the engine is driven but also during traction when the engine is stopped. be able to.

  In the first aspect of the invention, the closed circuit is supplied with hydraulic oil supplied from the auxiliary hydraulic pump to the operating mechanism and used for operating the operating mechanism through the supply oil passage. Thus, both the operation of the operating mechanism and the replenishment of the operating oil to the closed circuit can be performed with the operating oil discharged from the auxiliary hydraulic pump during traction when the engine is stopped. That is, while simplifying the configuration, the hydraulic pump for operating the operating mechanism during traction when the engine is stopped and the hydraulic pump for supplying hydraulic oil to the closed circuit are simplified, Both the operation of the operating mechanism during towing and the supply of hydraulic oil to the closed circuit can be performed.

  According to a second aspect of the present invention, in the hydraulic traveling vehicle according to the first aspect, the replenishing oil passage joins with an oil passage for flowing hydraulic oil discharged from the charge pump to the closed circuit. The replenishing oil passage is provided with a check valve for preventing the backflow of the hydraulic oil from the oil passage side.

  According to the second aspect of the present invention, it is checked that the hydraulic oil discharged from the charge pump and replenished to the closed circuit during the normal traveling of the hydraulic traveling vehicle driven by the engine flows back into the replenishment oil passage. Can be prevented with a valve.

  According to a third aspect of the present invention, in the hydraulic traveling vehicle according to the first or second aspect, a predetermined amount of the hydraulic oil that is discharged from the operating mechanism and flows to the replenishing oil passage is supplied to the hydraulic oil tank. It is characterized by comprising return oil means for allowing the return to return.

  According to the third aspect of the present invention, a predetermined amount of hydraulic oil that does not flow to the closed circuit side among the hydraulic oil that is discharged from the operating mechanism and flows into the replenishing oil passage can be returned to the hydraulic oil tank by the return oil means. it can.

  According to a fourth aspect of the present invention, in the hydraulic traveling vehicle according to the third aspect, the return oil means includes a return oil path for flowing hydraulic oil from the replenishment oil path to the hydraulic oil tank, and a return thereof. And a back pressure valve that is provided in the oil passage and generates a back pressure on the supply oil passage side.

  According to the fourth aspect of the present invention, a predetermined amount of hydraulic oil that does not flow to the closed circuit side out of the hydraulic oil that is discharged from the operating mechanism and flows to the replenishing oil path can be returned to the hydraulic oil tank through the return oil path. In addition, back pressure can be generated on the replenishment oil passage side by a back pressure valve provided in the return oil passage. For this reason, the hydraulic pressure in the replenishment oil passage decreases while allowing a predetermined amount of hydraulic oil that does not flow to the closed circuit side to escape to the hydraulic oil tank when the hydraulic oil discharged from the operating mechanism is replenished to the closed circuit through the replenishment oil passage. Thus, it is possible to prevent the hydraulic oil from flowing from the replenishment oil path to the closed circuit side.

  According to a fifth aspect of the present invention, in the hydraulic traveling vehicle according to the fourth aspect of the present invention, the hydraulic traveling vehicle according to the fourth aspect is provided in a bypass path provided in the return oil path so as to bypass the back pressure valve. A switching valve configured to be switchable between a distribution position that allows distribution and a blocking position that blocks distribution of hydraulic oil is provided.

  According to the fifth aspect of the present invention, when the hydraulic traveling vehicle with the engine stopped is pulled, the bypass valve is shut off with the switching valve as the shut-off position, and the back pressure by the back pressure valve is generated in the replenishing oil passage to replenish. A predetermined amount of hydraulic oil that does not flow to the closed circuit side while replenishing hydraulic oil from the oil path to the closed circuit can be returned to the hydraulic oil tank through the return oil path and back pressure valve, while the hydraulic drive that the engine is driving During normal driving of the vehicle, the bypass valve is set to a flow position so that the hydraulic oil can flow, and the bypass oil is discharged from the operating mechanism and flows into the replenishment oil path without applying back pressure by the back pressure valve. Can be returned to the hydraulic oil tank. For this reason, while returning a predetermined amount of hydraulic fluid that does not flow to the closed circuit side when towing a hydraulic traveling vehicle with the engine stopped, the hydraulic pressure of the replenishment oil passage decreases and the closed oil circuit is closed to the closed circuit. When the hydraulic traveling vehicle driven by the engine normally travels, back pressure from the back pressure valve is always applied to the hydraulic fluid that is discharged from the operating mechanism and flows to the replenishment oil path. State can be avoided and power loss can be suppressed.

  According to a sixth aspect of the present invention, in the hydraulic traveling vehicle according to any one of the first to fifth aspects, the operating mechanism is operated by hydraulic pressure, and the drive wheel is steered according to a steering operation. This is a steering mechanism to be operated.

  According to the sixth aspect of the present invention, since the hydraulic pressure discharged from the auxiliary hydraulic pump can be supplied to the steering mechanism when the hydraulic traveling vehicle with the engine stopped is pulled, the steering mechanism can be operated. The steering wheel can be steered by operating the steering wheel when towing the hydraulic traveling vehicle.

  As described above, according to the present invention, in a hydraulic traveling vehicle, cavitation is prevented from occurring in the hydraulic circuit not only during normal traveling when the engine is driven but also during traction when the engine is stopped. be able to.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a drive system of a hydraulic traveling vehicle according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing the structure of the transmission portion 10a of the transmission mechanism 10 of the hydraulic traveling vehicle shown in FIG. First, the configuration of a hydraulic traveling vehicle according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  The hydraulic traveling vehicle according to the present embodiment uses an HST traveling system, and the traveling hydraulic motor 8 is driven by the hydraulic pressure supplied from the traveling hydraulic pump 6 driven by the engine 2. The vehicle travels by rotating the driving wheels 50 and 50 with a driving force.

  Specifically, the hydraulic traveling vehicle includes an engine 2, a power divider 4, a traveling hydraulic pump 6, a traveling hydraulic motor 8 (hereinafter simply referred to as a hydraulic motor 8), a transmission mechanism 10, and a charge. A pump 12, a steering pump 14, a steering mechanism 18, and an auxiliary hydraulic pump 16 are provided.

  The driving hydraulic pump 6 and the steering pump 14 are connected to the drive shaft of the engine 2 via the power divider 4. With this configuration, the driving force of the engine 2 is distributed to the traveling hydraulic pump 6 and the steering pump 14 by the power divider 4, and both the pumps 6 and 14 are driven.

  The traveling hydraulic pump 6 is of a variable capacity type and is configured to be a bidirectional discharge type, and has a supply / discharge port 6a on one side and a supply / discharge port 6b on the other side. The traveling hydraulic pump 6 is driven by the engine 2 to discharge hydraulic oil from the supply / discharge port 6a on one side or the supply / discharge port 6b on the other side.

  The hydraulic motor 8 is a variable displacement hydraulic motor, and is driven by the hydraulic pressure of the hydraulic oil discharged from the traveling hydraulic pump 6 to generate a driving force for rotating the driving wheels 50 and 50 of the traveling vehicle. . The hydraulic motor 8 is connected to the drive wheel output shaft 9, and the drive wheel output shaft 9 is rotated by driving the hydraulic motor 8, and the rotation is further transmitted to the drive wheels 50 and 50 via the transmission mechanism 10. Thus, the drive wheels 50 are rotated.

  The traveling hydraulic pump 6 and the hydraulic motor 8 are connected by a closed circuit 30. The closed circuit 30 includes a pair of supply / discharge paths 30a and 30b.

  One end of one supply / discharge path 30a of the pair of supply / discharge paths 30a, 30b is connected to one supply / discharge port 6a of the traveling hydraulic pump 6, while the other end is one of the hydraulic motor 8. It is connected to the supply / discharge port 8a. One end of the other supply / discharge passage 30 b is connected to the other supply / exhaust port 6 b of the traveling hydraulic pump 6, and the other end is connected to the other supply / exhaust port 8 b of the hydraulic motor 8. .

  With this configuration, for example, when hydraulic oil is discharged from one supply / exhaust port 6a of the traveling hydraulic pump 6, the hydraulic oil passes through the one supply / discharge passage 30a and is supplied to one supply / discharge port 8a of the hydraulic motor 8. The hydraulic motor 8 is rotated. Then, the return oil is discharged from the other supply / discharge port 8b of the hydraulic motor 8, and the return oil is returned to the other supply / discharge port 6b of the traveling hydraulic pump 6 through the other supply / discharge channel 30b. In this way, the hydraulic oil discharged from the traveling hydraulic pump 6 drives the hydraulic motor 8 while circulating through the closed circuit 30. When hydraulic oil is discharged from the other supply / discharge port 6b of the traveling hydraulic pump 6, the hydraulic motor 8 rotates in the reverse direction.

  Further, the closed circuit 30 is provided with a connection path 31 connecting the supply / discharge paths 30a, 30b, and a first check for preventing the backflow of hydraulic oil from one supply / discharge path 30a to the connection path 31. A valve 32 and a second check valve 33 for preventing the backflow of hydraulic oil from the other supply / discharge passage 30b are provided. A first relief valve 34 is provided so as to bypass the first check valve 32, and a second relief valve 35 is provided so as to bypass the second check valve 33.

  The transmission mechanism 10 transmits the driving force of the hydraulic motor 8 to both the drive wheels 50 and 50 and the auxiliary hydraulic pump 16, while transmitting the rotation of the drive wheels 50 and 50 to the auxiliary hydraulic pump 16 and the hydraulic motor 8. Is.

  Specifically, the transmission mechanism 10 includes a transmission unit 10a and a wheel drive unit 10b.

  The transmission unit 10a transmits the driving force of the hydraulic motor 8 transmitted through the drive wheel output shaft 9 to the wheel drive unit 10b. As shown in FIG. 2, a first shaft 11 c that is rotatably supported by a pair of bearings 11 a and 11 b and is connected to the drive wheel output shaft 9 is provided in the transmission portion 10 a. A first gear 11d is externally fitted to the first shaft 11c, and the first gear 11d has a first external gear portion 11e and a second external tooth that are spaced apart in the axial direction. And a gear portion 11f.

  Further, a second shaft 11i that is rotatably supported by a pair of bearings 11g and 11h is provided in the transmission portion 10a. The second shaft 11i is connected to the drive shaft 10c of the wheel drive unit 10b. A second gear 11j that meshes with the first external gear portion 11e is externally fitted to the second shaft 11i.

  Further, the third gear 11m is fitted on the second shaft 11i via a bearing (not shown). The third gear 11m includes a third external gear portion 11n that meshes with the second external gear portion 11f, and a fourth external gear portion 11p having a smaller diameter than the third external gear portion 11n. Yes. A fourth gear 11q is meshed with the fourth external gear portion 11p, and the fourth gear 11q is connected to the drive shaft 16a of the auxiliary hydraulic pump 16.

  With such a configuration, when the drive wheel output shaft 9 rotates by driving the hydraulic motor 8, the rotation is caused by the first external gear portion of the first gear 11d via the first shaft 11c and the first gear 11d. 11e is transmitted to the 2nd gear 11j, the 2nd axis | shaft 11i is rotated, and the drive shaft 10c of the wheel drive part 10b is rotated. The rotation of the drive wheel output shaft 9 is transmitted from the second external gear portion 11f of the first gear 11d to the third external gear portion 11n of the third gear 11m, and further the fourth external gear of the third gear 11m. When the rotation is transmitted from the portion 11p to the fourth gear 11q, the drive shaft 16a rotates and the auxiliary hydraulic pump 16 is driven.

  On the other hand, when the rotation of the drive wheels 50 and 50 is transmitted to the wheel drive unit 10b and the drive shaft 10c rotates, the rotation is the first external gear of the first gear 11d via the second shaft 11i and the second gear 11j. Rotation is transmitted from the second external gear portion 11f of the first gear 11d to the third external gear portion 11n of the third gear 11m and the fourth external gear of the third gear 11m. The rotation is transmitted from the portion 11p to the fourth gear 11q. Thereby, the drive shaft 16a rotates and the auxiliary hydraulic pump 16 is driven. Further, the rotation of the drive shaft 10c is transmitted to the first gear 11d via the second shaft 11i and the second gear 11j, whereby the first shaft 11c rotates and the drive wheel output shaft 9 rotates, so that the hydraulic motor 8 is driven.

  The wheel drive unit 10b transmits the rotation transmitted from the transmission unit 10a to the drive shaft 10c to both the drive wheels 50 and 50 to rotate the drive wheels 50 and 50. Conversely, when the driving wheels 50 and 50 are rotated when the traveling vehicle is towed, the wheel driving unit 10b transmits the rotation from the driving shaft 10c to the second shaft 11i of the transmitting unit 10a.

  The charge pump 12 is a constant-capacity hydraulic pump that is driven when the traveling hydraulic pump 6 is driven to replenish hydraulic fluid to the closed circuit 30 when the engine 2 is driven. The charge pump 12 is provided so that the driving force of the traveling hydraulic pump 6 is transmitted, is driven by the transmission of the driving force, and sucks and discharges the hydraulic oil from the hydraulic oil tank.

  An oil passage 13 for flowing hydraulic oil discharged from the charge pump 12 to the closed circuit 30 is connected to the discharge port of the charge pump 12. The end of the oil passage 13 opposite to the charge pump 12 is connected to a portion of the connection passage 31 between the first check valve 32 and the second check valve 33. In addition, a third relief valve 36 is connected to the oil passage 13, and when the pressure of the hydraulic oil flowing through the oil passage 13 exceeds the set pressure of the third relief valve 36, a part of the hydraulic oil is changed to the first. The oil is passed through the three relief valve 36 to the hydraulic oil tank. As a result, the hydraulic oil discharged from the charge pump 12 and flowing into the oil passage 13 is introduced into the connection passage 31 at a pressure equal to or lower than the set pressure by the third relief valve 36, and the low pressure side of the both supply and discharge passages 30a and 30b It is replenished through the first check valve 32 or the second check valve 33 corresponding to the supply / discharge path.

  The steering pump 14 supplies hydraulic oil to the steering mechanism 18 and comprises a constant capacity hydraulic pump. The steering pump 14 is driven by the driving force of the engine 2 being transmitted through the power divider 4 and sucks and discharges the hydraulic oil from the hydraulic oil tank. A steering supply oil passage 15 connected to a steering system 18b (described later) of the steering mechanism 18 is connected to the discharge port of the steering pump 14, and hydraulic oil discharged from the steering pump 14 is supplied to the steering supply oil passage 15. Through the steering system 18b.

  The auxiliary hydraulic pump 16 is driven by transmitting the driving force of the hydraulic motor 8 or the rotation of the driving wheels 50 and 50 to the driving shaft 16a (see FIG. 2) in the transmission mechanism 10 as described above. This is a constant capacity hydraulic pump that sucks and discharges hydraulic oil from a tank. A supply oil passage 17 connected to a steering system 18b (to be described later) of the steering mechanism 18 is connected to the discharge port of the auxiliary hydraulic pump 16. The hydraulic oil discharged from the auxiliary hydraulic pump 16 is supplied to the supply oil passage 17. Through the steering system 18b.

  The steering mechanism 18 is included in the concept of the operating mechanism of the present invention. When the operating oil discharged from the steering pump 14 or the operating oil discharged from the auxiliary hydraulic pump 16 is supplied, Actuated by hydraulic pressure of hydraulic oil, the drive wheels 50 and 50 are steered in accordance with the operation of a steering (not shown) by the driver.

  Specifically, the steering mechanism 18 includes a steering device 18a and a steering system 18b.

  The steering device 18a is driven by the hydraulic pressure of the hydraulic oil sent from the steering system 18b to steer the drive wheels 50 and 50. The steering device 18a has a double-acting hydraulic cylinder 18d connected to the steering system 18b by a steering circuit 18c, and hydraulic oil is supplied to a supply / discharge port on one side of the hydraulic cylinder 18d. As a result, the hydraulic oil is discharged from the supply / discharge port on the other side, and the hydraulic cylinder 18d is operated to steer the drive wheels 50, 50 to the left and right.

  The steering system 18b supplies the hydraulic oil supplied from the steering pump 14 or the auxiliary hydraulic pump 16 to a supply / discharge port on one side or the other side of the hydraulic cylinder 18d through a steering circuit 18c according to the steering operation of the driver. By supplying the hydraulic cylinder 18d, the hydraulic cylinder 18d is operated, and the hydraulic oil returned from the hydraulic cylinder 18d through the steering circuit 18c is discharged. When the engine 2 is driven, the steering system 18b supplies the hydraulic oil supplied from the steering pump 14 to the hydraulic cylinder 18d and unloads the hydraulic oil supplied from the auxiliary hydraulic pump 16. On the other hand, when the engine 2 is stopped, when hydraulic oil is supplied from the auxiliary hydraulic pump 16, the hydraulic oil is supplied to the hydraulic cylinder 18d.

  The steering system 18b is connected to a replenishment oil passage 20 for flowing hydraulic oil discharged from the steering system 18b to the closed circuit 30 after being used for operating the steering mechanism 18. The end of the replenishment oil passage 20 opposite to the steering system 18 b is connected to a portion of the connection passage 31 between the first check valve 32 and the second check valve 33. With this configuration, the hydraulic oil discharged from the steering system 18b and flowing into the replenishment oil passage 20 is introduced into the connection passage 31, and the first check corresponding to the supply / discharge passage on the low pressure side of the both supply / discharge passages 30a, 30b. Replenishment is made through the valve 32 or the second check valve 33.

  The replenishment oil passage 20 joins the oil passage 13 for flowing the hydraulic oil from the charge pump 12 to the closed circuit 30 at a portion connected to the connection passage 31. A third check valve 22 for preventing the hydraulic oil from flowing backward from the oil path 13 side when the engine 2 is driven and hydraulic oil is discharged from the charge pump 12 is supplied to the replenishment oil path 20. Is provided. This third check valve 22 is included in the concept of the check valve of the present invention.

  A return oil passage 24 and a back pressure valve 26 as an example of return oil means for allowing a predetermined amount of hydraulic oil to be returned from the steering system 18b and flowing into the replenishment oil passage 20 to the hydraulic oil tank, Is provided.

  The return oil passage 24 connects the replenishment oil passage 20 and the hydraulic oil tank, and allows the predetermined amount of hydraulic oil to flow from the replenishment oil passage to the hydraulic oil tank.

  The back pressure valve 26 is provided in the return oil passage 24 and generates a back pressure on the supply oil passage 20 side. When the opening pressure of the back pressure valve 26 exceeds the pressure of the hydraulic oil on the supply oil passage 20 side, a predetermined amount of the hydraulic oil on the supply oil passage 20 side passes through the return oil passage 24 and the back pressure valve 26. To escape into the hydraulic oil tank. As a result, a back pressure substantially equal to the valve opening pressure of the back pressure valve 26 is generated in the replenishment oil passage 20. The valve opening pressure of the back pressure valve 26 is set lower than the set pressure of the third relief valve 36 provided in the oil passage 13 through which the hydraulic oil from the charge pump 12 flows. As a result, as long as the hydraulic oil is discharged from the charge pump 12 when the engine 2 is being driven, the hydraulic oil that is discharged from the steering system 18b and flows into the replenishment oil path 20 is connected to the connection path more than the third check valve 22. Instead of being introduced to the side 31, the oil is returned to the hydraulic oil tank through the return oil passage 24 and the back pressure valve 26.

  Next, the operation of the drive system of the hydraulic traveling vehicle according to the present embodiment will be described.

  First, during normal running while the engine 2 is driven, the driving force of the engine 2 is transmitted to the traveling hydraulic pump 6 and the steering pump 14 via the power divider 4 to drive both the pumps 6 and 14.

  As a result, hydraulic oil is discharged from the traveling hydraulic pump 6, and the hydraulic oil drives the hydraulic motor 8 while circulating through the closed circuit 30. Then, the driving force of the hydraulic motor 8 is transmitted to the drive wheels 50 and 50 via the transmission mechanism 10, and the drive wheels 50 and 50 rotate. In this way, the hydraulic traveling vehicle of this embodiment travels normally.

  At this time, since hydraulic fluid leaks due to driving of the traveling hydraulic pump 6 and the hydraulic motor 8 and the like, cavitation may occur due to insufficient hydraulic fluid in the closed circuit 30. Therefore, during normal running when the engine 2 is driven, the hydraulic oil discharged from the charge pump 12 as the running hydraulic pump 6 is driven passes through the oil passage 13 and the connection passage 31 among the supply / discharge passages 30a and 30b. A reduction in the amount of hydraulic fluid that is replenished to the low-pressure side supply / discharge passage and circulates in the closed circuit 30 is suppressed. Thereby, the occurrence of cavitation in the closed circuit 30 is prevented.

  Further, during normal driving while the engine 2 is being driven, hydraulic oil is discharged from the steering pump 14 to the steering system 18b, and the steering device is turned from the steering system 18b through the steering circuit 18c according to the steering operation of the driver. The hydraulic oil is supplied to the hydraulic cylinder 18d of 18a, the hydraulic cylinder 18d is operated, and the drive wheels 50 and 50 are steered. In this manner, the steering operation of the drive wheels 50 and 50 during normal traveling of the hydraulic traveling vehicle is performed.

  Then, the hydraulic oil that is used to operate the hydraulic cylinder 18d and returns to the steering system 18b is discharged from the steering system 18b to the replenishment oil passage 20. The hydraulic oil discharged to the replenishing oil passage 20 is such that the opening pressure of the back pressure valve 26 in the return oil passage 24 is the third relief during normal traveling when the hydraulic oil is discharged from the charge pump 12 to the oil passage 13. Due to being set to a pressure lower than the set pressure of the valve 36, it is not introduced to the connection path 31 side, that is, the closed circuit 30 side from the third check valve 22, and passes through the return oil path 24 and the back pressure valve 26. Returned to hydraulic oil tank.

  During this normal travel, the driving force of the hydraulic motor 8 is also transmitted to the auxiliary hydraulic pump 16 via the transmission unit 10a, and hydraulic oil is supplied from the auxiliary hydraulic pump 16 to the steering system 18b through the supply oil passage 17. However, this hydraulic oil is unloaded in the steering system 18b and returned to the hydraulic oil tank.

  On the other hand, when the engine 2 is stopped, the traveling hydraulic pump 6 and the steering pump 14 are also stopped, and hydraulic fluid is not discharged from both the pumps 6 and 14. For this reason, the hydraulic motor 8 also stops and the drive wheels 50 and 50 do not rotate. Further, since the hydraulic oil is not supplied to the steering mechanism 18, the steering operation of the drive wheels 50 and 50 cannot be performed.

  In this state, for example, when the hydraulic traveling vehicle is pulled, the drive wheels 50 and 50 rotate, and the rotation of the drive wheels 50 and 50 is transmitted to the hydraulic motor 8 and the auxiliary hydraulic pump 16 via the transmission mechanism 10. . As a result, the hydraulic motor 8 is driven, and hydraulic oil is discharged from the hydraulic motor 8 to the other supply / discharge passage 30b. At this time, by manually bypassing the second relief valve 35, the hydraulic oil discharged to the other supply / discharge passage 30 b passes through the connection passage 31 via the second relief valve 35 and passes through the first check valve 32. Flows through the one supply / discharge passage 30a and returns to the hydraulic motor 8 from the supply / discharge passage 30a. That is, at the time of this traction, the hydraulic motor 8 is driven and the hydraulic oil discharged from the hydraulic motor 8 circulates without being returned to the traveling hydraulic pump 6.

  Further, the rotation of the drive wheels 50, 50 is transmitted to the auxiliary hydraulic pump 16 through the transmission mechanism 10, so that the auxiliary hydraulic pump 16 is driven and the hydraulic oil is discharged to the supply oil passage 17. The hydraulic oil discharged to the supply oil passage 17 is introduced into the steering system 18b, and the steering operation of the drive wheels 50 and 50 is performed in the same manner as in the normal traveling. That is, in the present embodiment, the steering operation of the drive wheels 50 and 50 is possible even when the engine 2 is stopped and the traveling vehicle is towed.

  By the way, even when towing the engine 2 is stopped, the hydraulic motor 8 is driven and the working oil circulates as described above, so that a minute leakage of the working oil occurs and the towing is performed for a long time. When the traction is performed at a high speed or a large number of tractions are performed, the total amount of hydraulic fluid leakage increases, and as a result, cavitation may occur in the closed circuit 30. Therefore, during traction when the engine 2 is stopped, the hydraulic fluid discharged from the auxiliary hydraulic pump 16 and used by the steering mechanism 18 is discharged to the closed circuit 30 after being discharged from the steering system 18b.

  Specifically, the hydraulic oil supplied from the auxiliary hydraulic pump 16 to the hydraulic cylinder 18d through the steering system 18b, used for the operation of the hydraulic cylinder 18d, and then returned to the steering system 18b is discharged to the replenishment oil passage 20. Is done. A predetermined back pressure is generated in the hydraulic oil discharged to the replenishment oil passage 20 by the back pressure valve 26. When the engine 2 is stopped, the charge pump 12 is not driven, and hydraulic oil is not discharged from the charge pump 12 to the oil passage 13, so that the hydraulic oil discharged to the replenishment oil passage 20 is third due to the back pressure. While being introduced into the connection path 31 through the check valve 22, the supply / discharge path 30a on the low pressure side of the supply / discharge paths 30a, 30b is replenished. As a result, even when the engine 2 is stopped, a reduction in the amount of hydraulic fluid circulating in the closed circuit 30 is suppressed, and the occurrence of cavitation in the closed circuit 30 is prevented.

  A predetermined amount of hydraulic oil that does not flow to the closed circuit 30 side of the hydraulic oil that is discharged from the steering system 18 b and flows to the replenishment oil path 20 is returned to the hydraulic oil tank through the return oil path 24 and the back pressure valve 26.

  As described above, the operation of the drive system of the hydraulic traveling vehicle according to the present embodiment is performed.

  As described above, according to the present embodiment, hydraulic oil is supplied from the charge pump 12 to the closed circuit 30 connected to the hydraulic motor 8 during normal driving when the engine 2 of the hydraulic traveling vehicle is driven. Therefore, it is possible to prevent the occurrence of cavitation in the closed circuit 30 due to leakage of hydraulic oil accompanying driving of the hydraulic motor 8 or the like. On the other hand, when the hydraulic traveling vehicle with the engine stopped is towed, the auxiliary hydraulic pump 16 is driven as the drive wheels 50 and 50 are rotated to discharge the hydraulic oil sucked from the hydraulic oil tank and to be discharged. After the hydraulic oil is used in the steering mechanism 18, it flows through the replenishment oil passage 20 to the closed circuit 30, and even when the hydraulic traveling vehicle in which the engine 2 is stopped is towed. The closed circuit 30 can be supplemented with hydraulic oil to prevent cavitation. Therefore, in the present embodiment, in the hydraulic traveling vehicle, it is possible to prevent cavitation from occurring in the closed circuit 30 not only during normal traveling when the engine 2 is driven but also during traction when the engine is stopped. .

  Further, in the present embodiment, the closed hydraulic circuit 30 is supplied with the hydraulic oil supplied from the auxiliary hydraulic pump 16 to the steering mechanism 18 and used for the operation of the steering mechanism 18 through the supply oil passage 20. When the engine 2 is towed while the engine 2 is stopped, the driving mechanism can be steered by operating the steering mechanism 18 with the hydraulic oil discharged from the auxiliary hydraulic pump 16 and the hydraulic oil can be supplied to the closed circuit 30. It can be carried out. That is, the configuration is simplified as compared with a case where a hydraulic pump for operating the steering mechanism 18 during towing when the engine 2 is stopped and a hydraulic pump for supplying hydraulic oil to the closed circuit 30 are separately provided. However, both the operation of the steering mechanism 18 at the time of towing and the replenishment of hydraulic oil to the closed circuit 30 can be performed.

  In this embodiment, the replenishment oil passage 20 joins the oil passage 13 for flowing the hydraulic oil discharged from the charge pump 12 to the closed circuit 30. Since the third check valve 22 for preventing the backflow of hydraulic oil from the oil passage 13 side is provided, the closed circuit 30 is discharged from the charge pump 12 during normal traveling of the hydraulic traveling vehicle driven by the engine 2. The third check valve 22 can prevent the hydraulic oil replenished to flow back to the replenishment oil passage 20 side.

  In the present embodiment, the return oil passage 24 and the back as a return oil means for allowing a predetermined amount of the hydraulic oil discharged from the steering system 18b and flowing into the replenishment oil passage 20 to return to the hydraulic oil tank. Since the pressure valve 26 is provided, a predetermined amount of hydraulic oil that does not flow to the closed circuit 30 side of the hydraulic oil that is discharged from the steering system 18 b and flows to the replenishment oil path 20 is returned through the return oil path 24 and the back pressure valve 26. Can be returned to the tank.

  In the present embodiment, since the back pressure valve 26 for generating the back pressure on the supply oil passage 20 side is provided in the return oil passage 24 for flowing the operation oil from the supply oil passage 20 to the operation oil tank. A predetermined amount of hydraulic oil that does not flow to the closed circuit 30 side among the hydraulic oil that is discharged from the system 18 b and flows to the replenishment oil passage 20 can be released to the hydraulic oil tank through the return oil passage 24, and the back pressure valve 26 supplies A back pressure can be generated on the side of the path 20. Therefore, when the hydraulic oil discharged from the steering system 18b is supplied to the closed circuit 30 through the supply oil path 20, a predetermined amount of hydraulic oil that does not flow to the closed circuit 30 side is released to the hydraulic oil tank, and the supply oil path 20 is discharged. It is possible to prevent the hydraulic oil from flowing down and the hydraulic oil from flowing from the replenishment oil passage 20 to the closed circuit 30.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, as in a modification of the above-described embodiment shown in FIG. 3, a switching valve 44 is provided in a bypass passage 42 provided in the return oil passage 24 so as to bypass the back pressure valve 26, and the engine 2 is driven by the switching valve 44. Back pressure by the back pressure valve 26 is applied to the hydraulic oil discharged from the steering system 18b to the replenishment oil passage 20 when the engine is driven and stopped, or the hydraulic oil bypasses the back pressure valve 26 and enters the hydraulic oil tank. You may comprise so that return can be switched.

  Specifically, in this modification, the bypass passage 42 is provided in the return oil passage 24 so as to bypass the back pressure valve 26 from the replenishment oil passage 20, and the switching valve 44 is provided in the bypass passage 42. .

  As shown in FIG. 3, the switching valve 44 can be manually switched between a flow position A that allows the hydraulic oil to flow in the bypass path 42 and a blocking position B that blocks the flow of hydraulic oil in the bypass path 42. It is configured. When the hydraulic traveling vehicle with the engine 2 stopped is driven, the driver operates the switching valve 44 to the shut-off position B to shut off the flow of hydraulic oil in the bypass passage 42 and flow through the replenishment oil passage 20. While a back pressure is applied to the oil by the back pressure valve 26, during normal traveling of the hydraulic traveling vehicle driven by the engine 2, the driver operates the switching valve 44 to the distribution position A and is discharged from the steering system 18 b. Thus, the hydraulic oil flowing through the replenishing oil passage 20 is returned to the hydraulic oil tank through the bypass passage 42 without applying back pressure by the back pressure valve 26.

  According to the configuration of this modification, when the hydraulic traveling vehicle with the engine 2 stopped is pulled, the bypass valve 42 is shut off with the switching valve 44 as the shut-off position, and the back pressure by the back pressure valve 26 is generated in the replenishment oil passage 20. The predetermined amount of hydraulic oil that does not flow to the closed circuit 30 side while replenishing the hydraulic oil from the supply oil path 20 to the closed circuit 30 can be returned to the hydraulic oil tank through the return oil path 24 and the back pressure valve 26. During normal traveling of the hydraulic traveling vehicle 2 driven, the switching valve 44 is set as the flow position so that the hydraulic oil can flow through the bypass passage 42, and the hydraulic oil is discharged from the steering system 18b and flows into the replenishment oil passage 20. The oil can be returned to the hydraulic oil tank through the bypass passage 42 without applying a back pressure by the back pressure valve 26 to the oil. For this reason, while returning a predetermined amount of hydraulic oil that does not flow to the closed circuit 30 side to the hydraulic oil tank when the hydraulic traveling vehicle in which the engine 2 is stopped is returned to the hydraulic oil tank, the hydraulic pressure on the supply oil passage 20 side decreases and the supply oil The hydraulic oil is prevented from flowing from the road 20 to the closed circuit 30 side, and the hydraulic oil that is discharged from the steering system 18b and flows to the replenishment oil path 20 during normal running of the hydraulic traveling vehicle driven by the engine 2 is prevented. A state in which the back pressure by the back pressure valve 26 is constantly applied can be avoided, and power loss can be suppressed.

  In the above modification, the switching valve 44 is automatically switched so as to be in the shut-off position when the engine 2 is stopped and to be in the flow position when the engine 2 is driven. May be.

  Further, as a return oil means for allowing a predetermined amount of hydraulic oil to return to the hydraulic oil tank from the hydraulic oil discharged from the steering system 18b and flowing into the supply oil path 20, a return provided in the above-described supply oil path 20 is provided. It is not restricted to what consists of the oil path 24 and the back pressure valve 26, It is possible to apply various things other than the above about the structure and installation location.

  Further, the return oil passage 24 and the back pressure valve 22 as described above may not be provided, and the hydraulic oil discharged from the steering system 18b may be directly introduced into the closed circuit 30 through the replenishment oil passage. However, in this case, in order to release a predetermined amount of hydraulic oil from the closed circuit 30, a return oil path is connected to the closed circuit 30 via a relief valve, and the predetermined amount of oil is supplied from the return oil path to the hydraulic oil tank. It is preferable to let hydraulic oil escape.

  In addition, as an operating mechanism that operates when hydraulic oil discharged from the auxiliary hydraulic pump 16 is supplied, various operating mechanisms other than the steering mechanism 18 may be used.

It is a figure which shows the drive system of the hydraulic traveling vehicle by one Embodiment of this invention. It is the figure which showed schematically the structure of the transmission mechanism of the hydraulic traveling vehicle shown in FIG. It is a figure which shows the drive system of the hydraulic traveling vehicle by the modification of one Embodiment of this invention.

Explanation of symbols

2 Engine 6 Traveling hydraulic pump 8 Traveling hydraulic motor 12 Charge pump 13 Oil passage 16 Auxiliary hydraulic pump 18 Steering mechanism (actuating mechanism)
20 Supply oil passage 22 Third check valve (check valve)
24 Return oil path 26 Back pressure valve 30 Closed circuit 42 Bypass path 44 Switching valve 50 Drive wheel

Claims (6)

A traveling hydraulic pump that is driven by an engine and discharges hydraulic oil, and is connected to the traveling hydraulic pump in a closed circuit, and is driven by the hydraulic pressure of the hydraulic oil discharged from the traveling hydraulic pump. A hydraulic traveling vehicle comprising: a traveling hydraulic motor that rotates; and a charge pump that is driven in accordance with the driving of the traveling hydraulic pump and replenishes the closed circuit with hydraulic oil;
An auxiliary hydraulic pump that is driven in accordance with the rotation of the drive wheel and sucks and discharges hydraulic oil from a hydraulic oil tank;
An operating mechanism that operates when hydraulic oil discharged from the auxiliary hydraulic pump is supplied;
A hydraulic traveling vehicle, comprising: a replenishment oil passage for flowing hydraulic oil discharged from the actuation mechanism to the closed circuit after being used in the actuation mechanism. The replenishing oil passage is joined with an oil passage for flowing hydraulic oil discharged from the charge pump to the closed circuit,
2. The hydraulic traveling vehicle according to claim 1, wherein the replenishment oil passage is provided with a check valve for preventing a backflow of hydraulic oil from the oil passage side.   The return oil means for allowing a predetermined amount of the hydraulic oil discharged from the operating mechanism and flowing into the replenishment oil path to return to the hydraulic oil tank is provided. The hydraulic traveling vehicle described.   The return oil means includes a return oil path for flowing hydraulic oil from the supply oil path to the hydraulic oil tank, and a back pressure valve provided in the return oil path and generating a back pressure on the supply oil path side. The hydraulic traveling vehicle according to claim 3, wherein:   It is provided in a bypass passage provided in the return oil passage so as to bypass the back pressure valve, and can be switched between a passage position allowing the flow of hydraulic oil in the bypass passage and a blocking position blocking the flow of hydraulic oil. The hydraulic traveling vehicle according to claim 4, further comprising a switching valve configured.   The hydraulic traveling vehicle according to any one of claims 1 to 5, wherein the operating mechanism is a steering mechanism that is operated by hydraulic pressure and that steers the driving wheel in accordance with a steering operation. .

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