JP5284046B2 - Hydraulic circuit structure of steering device - Google Patents

Description

  The present invention relates to a hydraulic circuit structure in an all-hydraulic steering apparatus.

  Conventionally, a hydraulic circuit disclosed in Patent Document 1 is known as a hydraulic circuit in an all-hydraulic steering apparatus. In this all-hydraulic steering device, wheels attached to both ends of an axle via a king pin are steerable by interlocking a pair of left and right cylinders. Then, by controlling the supply and discharge of hydraulic pressure to the front wheel side cylinder and the rear wheel side cylinder by the switching valve, the steering system is switched between the front wheel steering, the saddle steering, and the four-wheel steering. .

  FIG. 6 shows a hydraulic circuit in an all-hydraulic steering apparatus in which the steering system of the above-described known example is further developed. That is, this is a steering system in which rear wheel steering is further added to front wheel steering, saddle steering, and four wheel steering. In order to realize such various steering systems, a steer mode valve 6 including a front rear selection valve 61 and a rear side direction switching valve 62 is provided.

  The front / rear selection valve 61 controls the steering of the front wheels, and is constituted by a four-port (j, k, m, n) two-position (position a, position b) switching electromagnetic valve. The oil passage L5 is connected to the port j of the selection valve 61, the oil passage L2 is connected to the port k, the oil passage L6 is connected to the port m, and the oil passage L7 is connected to the port n. Yes.

  Further, the oil passage L5 is connected to the second oil supply / discharge oil passage 35 via the port B1 for external connection, and the oil passage L7 is connected to the first oil supply / discharge oil passage 34 via the port A1. The first supply / discharge oil passage 34 is connected in parallel to the reduced oil chamber of the first steering cylinder 1 and the extended oil chamber of the second steering cylinder 2. The second supply / discharge oil passage 35 is connected in parallel to the extension oil chamber of the first steering cylinder 1 and the reduction oil chamber of the second steering cylinder 2.

  The rear side direction switching valve 62 controls the steering of the rear wheel, and is composed of a four-port (d to g) three-position (position a to position c) switching type solenoid valve. The oil passage L1 is connected to the port d of the valve 62, the oil passage L2 is connected to the port e, the oil passage L3 is connected to the port f, and the oil passage L4 is connected to the port g. In the neutral position c, the port d and the port e are communicated, and the port f and the port g are both closed.

  Further, the oil passage L3 is connected to the fourth supply / discharge oil passage 37 via the external connection port A2, and the oil passage L4 is connected to the third supply / discharge oil passage 36 via the port B2. The fourth oil supply / discharge oil passage 37 is connected in parallel to the extension oil chamber of the third steering cylinder 3 and the reduction oil chamber of the fourth steering cylinder 4. The third supply / discharge oil passage 36 is connected in parallel to the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4. A double pilot check valve 5 is interposed in the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37.

  The oil passage L1 and the oil passage L6 are connected to a hydraulic pump 10 driven by a motor prime mover 11 via a known steering valve unit 7.

  On the other hand, FIG. 7 shows a specific structure of the steer mode valve 6. As described above, the steer mode valve 6 includes the front / rear selection valve 61 and the rear side direction switching valve 62. The rear side direction switching valve 62 is configured by slidably inserting the spool 40 into the spool insertion hole 41, and the hydraulic flow direction is switched by the sliding displacement of the spool 40.

  The steering valve unit 7 is connected to a steering wheel (not shown), and selectively supplies hydraulic pressure corresponding to the operation direction and operation amount of the steering to the oil passage L1 and the oil passage L6.

Here, the operation of the steering apparatus will be briefly described with reference to the circuit diagram of FIG.
(A) As shown in FIG. 6, when the front rear selection valve 61 is set to the position a and the rear side direction switching valve 62 is set to the neutral position c, the oil passage L1 from the steering valve unit 7 is set. Is supplied to the port k of the front / rear selection valve 61 through the oil passage L2, and further from the oil passage L7 through the first supply / discharge oil passage 34 to the first steering. Introduced into the reduced oil chamber of the cylinder 1 and the extended oil chamber of the second steering cylinder 2, both the front wheel 51 and the front wheel 52 (see FIG. 5) are steered to the right. The hydraulic pressure discharged from the extension oil chamber of the first steering cylinder 1 and the reduced oil chamber of the second steering cylinder 2 passes from the second supply / discharge oil passage 35 through the oil passage L5 and the oil passage L6. It is returned to the tank side and is not supplied to the third steering cylinder 3 and the fourth steering cylinder 4 side. That is, front wheel steering is realized.
(B) With the front rear selection valve 61 set to the position a and the rear side direction switching valve 62 set to the position a, when hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1, This hydraulic pressure is supplied from the oil passage L4 through the third supply / discharge oil passage 36 to the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4, and the rear wheel 53 and the rear wheel 54 ( Is steered to the left. The hydraulic pressure discharged from the extended oil chamber of the third steering cylinder 3 and the reduced oil chamber of the fourth steering cylinder 4 is transferred from the fourth supply / discharge oil passage 37 to the oil passage L3, the oil passage L2, and the oil passage L7. And is introduced into the reduced oil chamber of the first steering cylinder 1 and the extended oil chamber of the second steering cylinder 2, and the front wheel 51 and the front wheel 52 (see FIG. 5) are steered to the right. The hydraulic pressure discharged from the extended oil chamber of the first steering cylinder 1 and the reduced oil chamber of the second steering cylinder 2 passes through the oil passage L5 and the oil passage L6 from the second supply / discharge oil passage 35 and is tanked. Back to the side. That is, four-wheel steering is realized.
(C) In the state where the front rear selection valve 61 is set to the position b and the rear side direction switching valve 62 is set to the position a, when hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1, This hydraulic pressure is supplied from the oil passage L4 through the third supply / discharge oil passage 36 to the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4, and the rear wheel 53 and the rear wheel 54 ( Is steered to the left. The hydraulic pressure discharged from the extended oil chamber of the third steering cylinder 3 and the reduced oil chamber of the fourth steering cylinder 4 is transferred from the fourth supply / discharge oil passage 37 to the oil passage L3, the oil passage L2, and the oil passage L6. It is returned to the tank side through, and no steering on the front side is performed. That is, rear wheel steering is realized.
(D) In a state where the front direction switching valve 61 is set to the position a and the rear side direction switching valve 62 is set to the position b, when hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1, The hydraulic pressure is supplied from the oil passage L3 through the fourth supply / discharge oil passage 37 to the extension oil chamber of the third steering cylinder 3 and the reduction oil chamber of the fourth steering cylinder 4, and the rear wheel 53 and the rear wheel 54 ( Is steered to the right. The hydraulic pressure discharged from the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4 is supplied from the third supply / discharge oil passage 36 to the oil passage L4, the oil passage L2, and the oil passage. L7 is introduced into the reduced oil chamber of the first steering cylinder 1 and the extended oil chamber of the second steering cylinder 2 through the first supply / discharge oil passage 34, and the front wheel 51 and the front wheel 52 (see FIG. 5) are operated rightward. Be directed. The hydraulic pressure discharged from the extended oil chamber of the first steering cylinder 1 and the reduced oil chamber of the second steering cylinder 2 passes through the oil passage L5 and the oil passage L6 from the second supply / discharge oil passage 35 and is tanked. Back to the side. That is, the steering operation is realized.
(E) In the state where the front rear selection valve 61 is set to the position b and the rear side direction switching valve 62 is set to the position b, when hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1, The hydraulic pressure is supplied from the oil passage L3 through the fourth supply / discharge oil passage 37 to the extension oil chamber of the third steering cylinder 3 and the reduction oil chamber of the fourth steering cylinder 4, and the rear wheel 53 and the rear wheel 54 ( Is steered to the right. The hydraulic pressure discharged from the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4 is supplied from the third supply / discharge oil passage 36 to the oil passage L4, the oil passage L2, and the oil passage. It returns to the tank side through L6, and the steering on the front side is not performed. That is, rear wheel steering is realized in which the steering direction is opposite to that in the case of (C).

Japanese Utility Model Publication No. 62-5422

  Incidentally, in the state where the front rear selection valve 61 is set to the position a and the rear side direction switching valve 62 is set to the neutral position c, that is, the front wheel steering state (the state shown in FIG. 5), FIG. As shown in FIG. 7, the port f and the port g are closed, and the port d and the port e are in communication. In this case, as shown in FIG. 7, the port f is closed by the first land portion 42 of the spool 40, and the port g is closed by the second land portion 43 and the third land portion 44, respectively. Even if oil pressure is supplied to the oil passage 1 or the oil passage 2, it should not be supplied to the port A2 and the port B2, that is, the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 side.

  However, as shown in FIG. 7, in the rear side direction switching valve 62, the spool 40 is slidably inserted into the spool insertion hole 41. There is always a gap between the first land portion 42, the second land portion 43, and the third land portion 44 of the spool 40 facing this. Therefore, as indicated by broken line arrows in FIG. 7, the hydraulic pressure leaks through the gaps to the ports f and g, and the leaked oil flows through the rear third supply / discharge passage 36 and the fourth supply / discharge passage. The oil passage 37 is in a state of being introduced.

  Here, for example, when the vehicle turns, external force due to tire slip acts on the rear wheel 53 and the wheel 54 that are originally fixedly held in the straight direction. For example, when an external force is applied in the direction indicated by the white arrow in FIG. 5, a force in the reduction direction acts on the third steering cylinder 3, and the oil pressure in the reduction oil chamber is lower than the oil pressure of the leak oil. Further, in the fourth steering cylinder 4, a force in the extending direction acts, and the oil pressure in the extending oil chamber is reduced to a lower pressure side than the oil pressure of the leak oil. Accordingly, in the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4 where the hydraulic pressure has been reduced, the leaked oil generated on the rear side direction switching valve 62 side is double pilot check valve. The rear wheel 53 and the rear wheel 54, which should be introduced through 5 and should be fixed and held in the straight direction, are slightly steered to the left.

  In this case, when the external force applied to each of the rear wheels 53 and 54 disappears, the leaked oil introduced into the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4 is discharged. Although there is no problem, the double pilot check valve 5 is interposed in the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37, and the double steering check valve 5 reduces the size of the third steering cylinder 3. Since the discharge of hydraulic pressure from the oil chamber and the extended oil chamber side of the fourth steering cylinder 4 is restricted, the leaked oil is the reduced oil chamber of the third steering cylinder 3 and the extended oil of the fourth steering cylinder 4. It will be in the state enclosed in the room.

  By repeating such a phenomenon, the amount of oil sealed in the reduced oil chamber of the third steering cylinder 3 and the extended oil chamber of the fourth steering cylinder 4 gradually increases, and the rear wheel 53 and the wheel 54 As a result, the left steering state becomes prominent. As a result, in the front wheel steering state, the rear wheel 53 and the rear wheel 54, which should not be steered, are steered, and the vehicle is skewed, so that stable running is achieved. The problem of being disturbed will occur.

  Contrary to the above case, the external force caused by the slipping of the tire on the rear wheel 53 and the wheel 54 that are originally fixedly held in the straight traveling direction is opposite to the direction indicated by the white arrow in FIG. Even when the oil acts on the rear side direction switching valve 62, the leaked oil is introduced into the extension oil chamber of the third steering cylinder 3 and the reduction oil chamber of the fourth steering cylinder 4, and is essentially in the straight direction. Needless to say, the rear wheel 53 and the rear wheel 54 to be fixedly held to the right are slightly steered to the right.

  Accordingly, the present invention has been made with the object of proposing a hydraulic circuit structure capable of reliably preventing the occurrence of a skew state of a vehicle and realizing stable traveling in an all-hydraulic steering device.

  In the present invention, the following configuration is adopted as a specific means for solving such a problem.

  In the first invention of the present application, the first and second steering cylinders 1 and 2 for steering the left and right front wheels 51 and 52 and the third and fourth steering cylinders for steering the left and right rear wheels 53 and 54 are provided. 3, 4, a first supply / discharge oil passage 34 for supplying and discharging hydraulic pressure to the reduced oil chamber of the first steering cylinder 1 and the extended oil chamber of the second steering cylinder 2, and the first A second oil supply / discharge oil passage 35 used for supplying and discharging hydraulic pressure to the extension oil chamber of the steering cylinder 1 and the reduction oil chamber of the second steering cylinder 2, the reduction oil chamber of the third steering cylinder 3, A third oil supply / discharge oil passage 36 for supplying and discharging hydraulic pressure to and from the extension oil chamber of the four steering cylinders 4, an extension oil chamber of the third steering cylinder 3, and a reduction oil chamber of the fourth steering cylinder 4. 4th supply / discharge for hydraulic supply / discharge A double pilot check valve 5 provided in the passage 37, the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 to restrict the discharge of hydraulic pressure from each of the supply / discharge oil passages 36, 37; A rear side direction switching valve 62 is connected to the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 to control the supply / discharge of the hydraulic pressure to the third steering cylinder 3 and the fourth steering cylinder 4. In the hydraulic circuit structure of the steering device constituted by the steering mode valve 6, the rear side direction switching valve 62 is set to the neutral position, and the hydraulic pressure is supplied to the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37. In the front wheel steering state in which hydraulic pressure supply to the first supply / discharge oil passage 34 and the second supply / discharge oil passage 35 is executed, the third supply / discharge oil passage 36 and the fourth supply / discharge passage The oil passage 37 is connected to the above double pie. Than Tsu preparative check valve 5 is characterized in that connected to the drain passage 23 in the rear side direction switching valve 62 side.

  In the second invention of the present application, in the hydraulic circuit structure of the steering device according to the first invention, the steering mode valve 6 is connected to the first supply / discharge oil passage 34 and the second supply / discharge oil passage 35. A front / rear selection valve 61 for controlling supply / discharge of hydraulic pressure to / from the first steering cylinder 1 and the second steering cylinder 2 is provided.

  In a third invention of the present application, in the hydraulic circuit structure of the steering device according to the first or second invention, the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 are connected to the rear side direction switching valve. It is characterized in that it is connected to the drain flow path 23 through leak oil discharge paths 31 and 32 provided in 62 spools 40.

  In a fourth invention of the present application, in the hydraulic circuit structure of the steering device according to the first or second invention, the double pilot check valve 5 in the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 is provided. Between the rear side direction switching valves 62, the drain passage 23 is connected via check valves 12 and 13.

  In the present invention, the following effects can be obtained.

  (A) According to the hydraulic circuit structure of the steering device according to the first invention of the present application, the rear side direction switching valve 62 is set to the neutral position, and the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage In the front wheel steering state in which the hydraulic pressure supply to the first supply / discharge oil passage 34 and the second supply / discharge oil passage 35 is executed, the third supply / discharge oil passage is blocked. 36 and the fourth oil supply / discharge oil passage 37 are connected to the drain flow path 23 on the rear side direction switching valve 62 side of the double pilot check valve 5, so that leak oil is generated in the rear side direction switching valve 62. Even if the vehicle is steered and the pressure in the extension oil chamber or the reduction oil chamber of the third steering cylinder 3 and the fourth steering cylinder 4 is reduced, the leak oil will remain on the drain channel 23 side. Since it is discharged, it does not flow into the third supply / discharge oil passage 36 or the fourth supply / discharge oil passage 37, and accordingly, the extension oil chambers of the third steering cylinder 3 and the fourth steering cylinder 4 or Occurrence of a situation in which the left and right rear wheels 53 and 54 are steered and the vehicle is skewed due to leakage oil being sealed in the reduced oil chamber is prevented in advance, and the vehicle is driven stably. Is realized.

  (B) According to the hydraulic circuit structure of the steering device according to the second invention of the present application, the left and right front wheels 51 and 52 are steered or manipulated by switching the front / rear selection valve 61 provided in the steer mode valve 6. Although the direction stop is selected, when the steering of the left and right front wheels 51 and 52 is selected, the effect described in the above (a) is surely obtained.

  (C) According to the hydraulic circuit structure of the steering device according to the third aspect of the present invention, the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 are connected to the spool 40 of the rear side direction switching valve 62. Since it is connected to the drain passage 23 through the provided leak oil discharge passages 31 and 32, the leak oil is supplied to the drain passage 23 side in the rear side direction switching valve 62 that is a source of leak oil. Since the discharge process is performed, it is not necessary to add a special configuration to the other oil passages other than the rear side direction switching valve 62, and the vehicle can be prevented from skewing with a simple configuration and at a lower cost. realizable.

  (D) According to the hydraulic circuit structure of the steering device according to the fourth aspect of the present invention, the double pilot check valve 5 and the rear side direction switching in the third supply / discharge oil passage 36 and the fourth supply / discharge oil passage 37 are provided. Since the valve 62 is connected to the drain passage 23 via the check valves 12 and 13, the leakage oil can be discharged to the drain passage 23 only by adding the check valves 12 and 13. Thus, it is possible to prevent the skew of the vehicle.

  Hereinafter, the present invention will be specifically described based on preferred embodiments.

  An object of the present invention is to prevent the occurrence of a skew state of a vehicle in a front wheel running state in which the rear wheels 53 and 54 are not steered. In such a skew state of the vehicle, the leak oil generated in the rear side direction switching valve 62 is sealed in the third steering cylinder 3 and the fourth steering cylinder 4 on the rear side, and should not be steered originally. As described above, this occurs when 53 and 54 are in the steering state.

  Therefore, in order to prevent the occurrence of such a skew state of the vehicle, it is only necessary to prevent the leakage oil from being introduced into the third steering cylinder 3 and the fourth steering cylinder 4 side. . In the first and second embodiments described below, the leakage oil is prevented from being enclosed in the third and fourth steering cylinders 3 and 4 by the correspondence on the rear side direction switching valve 62 side. The third embodiment is realized by correspondence between the third and fourth steering cylinders 3 and 4 and the rear side direction switching valve 62. Hereinafter, the leakage oil sealing prevention structure will be specifically described for each of these embodiments.

I: First Embodiment FIG. 1 shows a hydraulic circuit of a steering apparatus according to a first embodiment of the present invention, and FIG. 2 shows a specific structure of a steering mode valve 6 shown in this hydraulic circuit diagram. Respectively.

  This hydraulic circuit diagram is a hydraulic circuit diagram of a vehicle equipped with an all-hydraulic steering device, for example, a rough terrain crane vehicle steering device, except for a part of the configuration unique to the present invention. It is the same as the hydraulic circuit diagram (see FIG. 6) of the above-described conventional steering device. Therefore, the same components are denoted by the same reference numerals corresponding to FIG. The description in is omitted. Further, the structure of the steer mode valve 6 shown in FIG. 2 is the same as that of the conventional steer mode valve 6 (see FIG. 7), except for a part of the structure peculiar to the present invention. The same components as those shown in FIG. 7 are assigned the same reference numerals as those in FIG.

  In the steering apparatus according to the first embodiment, the occurrence of the skew state of the vehicle is prevented by the correspondence on the rear side direction switching valve 62 side.

  In the first embodiment, as shown in FIGS. 1 and 2, the rear side direction switching valve 62 is constituted by a five-port, three-position switching type electromagnetic valve, and at its neutral position a, the oil passage L1. The port d connected to the oil passage L2 is connected to the oil passage L2 connected to the oil passage e, and the port f connected to the oil passage L3 and the port g connected to the oil passage L4 are both drained via the port h. Connected to the road 23.

  Specifically, as shown in FIG. 2, the spool A slidably inserted into the spool insertion hole 41 of the rear side direction switching valve 62 is inserted into the port A <b> 2 and the drain passage 23 at the neutral position. Are provided with a leak oil discharge passage 31 for connecting the port B2 and the drain flow passage 32 for connecting the drain passage 23 to each other.

  According to such a configuration, when the steering operation is performed by the operator in a state where the rear side direction switching valve 62 is set to the neutral position, hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1 or the oil passage L6. The For example, when hydraulic pressure is supplied to the oil passage L1, pressure is generated at the port d and the port e of the rear side direction switching valve 62. Then, as shown by broken line arrows in FIG. 2, this hydraulic pressure is generated in the fitting gap between the first land portion 42, the second land portion 43 and the third land portion 44 of the spool 40 and the spool fitting insertion hole 41. Intrusion occurs and the leaked oil can be introduced into the port A2 and the port B2.

  However, in this embodiment, since the leak oil discharge passage 31 and the leak oil discharge passage 32 are provided in the spool 40, the leak oil that enters the fitting gaps is the pressure of the oil passages L3 and L4. Since the pressure of the drain flow path 23 is lower than that, the oil is smoothly discharged to the drain flow path 23 side through the leak oil discharge paths 31 and 32.

  As a result, by introducing the oil from the port A2 and the port B2 to the oil passage L3 and the oil passage L4, leak oil is sealed in the third steering cylinder 3 and the fourth steering cylinder 4, and the rear parts The wheels 53 and 54 are steered to prevent the vehicle from entering a skew state in advance.

II: Second Embodiment FIG. 3 shows a specific structure of a steer mode valve 6 incorporated in a hydraulic circuit of a steering apparatus according to a second embodiment of the present invention.

  The steer mode valve 6 has the same basic configuration as that of the steer mode valve 6 of the first embodiment, and differs from the steer mode valve 6 of the first embodiment in that the port A2 and the port B2 In this embodiment, the leak oil that has entered each side is extracted by the leak oil discharge passages 31 and 32 and discharged to the drain flow path 23 side. Leakage oil that enters the fitting gap between the land portion 42, the second land portion 43, the third land portion 44, and the spool fitting insertion hole 41 is extracted before reaching the port A2 and the port B2 and is drained. This is the point that the liquid is discharged to the flow path 23 side.

  That is, in this embodiment, as shown in FIG. 3, the rear side direction switching valve 62 is connected to the leak oil discharge path 31 and the leak oil discharge path 32 of the leak oil discharge path 32 provided in the spool 40. In the state where the neutral position is set, the spool fitting insertion hole 41 and the first land portion 42, the second land portion 43, and the third land portion 44 of the spool 40 are within the fitting region on the leak oil intrusion side. The formation position is set so as to open.

  According to such a configuration, the steering operation is performed by the operator in a state where the rear side direction switching valve 62 is set to the neutral position, and hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1 or the oil passage L6. For example, when hydraulic pressure is supplied to the oil passage L1, pressure is generated at the ports d and e of the rear side direction switching valve 62, and the hydraulic pressure is increased by the first land portion 42, the second land portion 43 and the second land portion 43 of the spool 40. Even if it enters the fitting gap between the three land portions 44 and the spool fitting insertion hole 41, the leaked oil is directed to the leak oil discharge paths 31, 32 before reaching the ports A2 and B2. Extracted and smoothly discharged from the leak oil discharge paths 31, 32 to the drain flow path 23 side. Accordingly, it is ensured that the leak oil is sealed in the third steering cylinder 3 and the fourth steering cylinder 4 and the rear wheels 53 and 54 are steered to cause the vehicle to be skewed. It is to be prevented.

III: Third Embodiment FIG. 4 shows a hydraulic circuit of a steering device according to a third embodiment of the present invention. In both the first and second embodiments, the leak oil in the rear side direction switching valve 62 is sealed in the third steering cylinder 3 and the fourth steering cylinder 4 so that the rear wheels 53 and 54 are In contrast to the fact that the vehicle is steered and the vehicle is in a skewed state by extracting the leaked oil on the rear side direction switching valve 62 side and discharging it to the drain flow path 23 side. In this embodiment, the leak oil generated in the rear side direction switching valve 62 is extracted not in the rear side direction switching valve 62 side but in the oil passages L3 and L4 and discharged to the drain flow path 23 side. This is what we realized.

  Specifically, as shown in the hydraulic circuit diagram of FIG. 4, the rear side direction switching valve 62 has the same basic configuration as the hydraulic circuit of the conventional steering apparatus shown in FIG. The rear side direction switching valve 62 is composed of a four-port three-position switching type solenoid valve, and in its neutral position c, both the port f connected to the oil passage L3 and the port g connected to the oil passage L4 are closed. The check valve 12 and the check valve are arranged between the third steering cylinder 3 and the fourth steering cylinder 4 and the rear side direction switching valve 62 in the oil passages L3 and L4. A drain flow path 23 is connected via 13 and a normally open electromagnetic switching valve 14 is provided downstream of the check valves 12 and 13.

  According to such a configuration, the steering operation is performed by the operator in a state where the rear side direction switching valve 62 is set to the neutral position, and hydraulic pressure is supplied from the steering valve unit 7 to the oil passage L1 or the oil passage L6. For example, when hydraulic pressure is supplied to the oil passage L1, pressure is generated at the ports d and e of the rear side direction switching valve 62, and the hydraulic pressure is increased by the first land portion 42, the second land portion 43 and the second land portion 43 of the spool 40. Even if the oil enters the fitting clearance between the three land portions 44 and the spool fitting hole 41 and flows into the oil passage L3 and the oil passage L4 through the port A2 and the port B2, Before reaching the third steering cylinder 3 and the fourth steering cylinder 4, they are discharged to the drain flow path 23 side through the check valves 12, 13. Accordingly, it is ensured that the leak oil is sealed in the third steering cylinder 3 and the fourth steering cylinder 4 and the rear wheels 53 and 54 are steered to cause the vehicle to be skewed. It is to be prevented.

  The switching valve 14 is operated when the rear side switching valve 62 is switched from the neutral position to the position a or the position b (that is, the third steering cylinder 3 and the fourth steering cylinder 4 are operated). The oil passages L3 and L4 are controlled to be prevented from communicating with the drain passage 23 when the rear wheels 53 and 54 are steered).

1 is a hydraulic circuit diagram of a steering device according to a first embodiment of the present invention. FIG. 2 is a first structural explanatory view of a steer mode valve shown in FIG. 1. FIG. 3 is a second structural explanatory diagram of the steer mode valve shown in FIG. 1. FIG. 6 is a hydraulic circuit diagram of a steering apparatus according to a third embodiment of the present invention. It is structure explanatory drawing of a fully hydraulic type steering device. It is a hydraulic circuit diagram of the conventional steering device. FIG. 7 is an explanatory diagram of the structure of the steer mode valve shown in FIG. 6.

Explanation of symbols

1 ··· 1st steering cylinder 2 ··· 2nd steering cylinder 3 · · 3rd steering cylinder 4 · · 4th steering cylinder 5 · · Double pilot check valve 6 · · Steer mode valve 7 · · Steering valve Unit 10 ·· Hydraulic pump 11 ·· Motor 12 ·· Check valve 13 ·· Check valve 14 ·· Switch valve 23 ·· Drain flow channel 25 ·· Flow channel 31 ·· Leak oil discharge channel 32 ·· Leak oil discharge channel 34 .. First supply / discharge oil passage 35 .. Second supply / discharge oil passage 36 .. Third supply / discharge oil passage 37 .. Fourth supply / discharge oil passage 40 .. Spool 41 .. Spool fitting insertion hole 42 .. First land 43 ··· Second land 44 ··· Third land 51, 52 · · Front wheels 53, 54 · · Rear wheels 61 · · Front rear selection bar Sleeve 62 ... rear direction switching valve

Claims (4)

First and second steering cylinders (1) and (2) for steering left and right front wheels (51) and (52), and third and third for steering left and right rear wheels (53) and (54) No. 4 steering cylinders (3), (4), and a first hydraulic cylinder for supplying and discharging hydraulic pressure to the reduced oil chamber of the first steering cylinder (1) and the extended oil chamber of the second steering cylinder (2). The first supply / discharge oil passage (34), and the second supply / discharge for supplying / discharging hydraulic pressure to / from the extension oil chamber of the first steering cylinder (1) and the reduced oil chamber of the second steering cylinder (2). An oil passage (35), and a third supply / discharge oil passage (used to supply and discharge hydraulic pressure to and from the reduced oil chamber of the third steering cylinder (3) and the extension oil chamber of the fourth steering cylinder (4)). 36), the extension oil chamber of the third steering cylinder (3) and the fourth steering cylinder. A fourth supply / discharge oil passage (37) used for supplying / discharging hydraulic pressure to / from the reduced oil chamber of the dan (4), and the third supply / discharge oil passage (36) and the fourth supply / discharge oil passage (37). A double pilot check valve (5) which is provided and regulates the discharge of hydraulic pressure from each of the supply / discharge oil passages (36), (37), the third supply / discharge oil passage (36) and the fourth supply / discharge oil passage; A steering mode valve (6) provided with a rear side direction switching valve (62) connected to (37) and controlling supply and discharge of hydraulic pressure to and from the third steering cylinder (3) and the fourth steering cylinder (4). ) And a hydraulic circuit structure of the steering device,
The rear side direction switching valve (62) is set to a neutral position, and the hydraulic pressure supply to the third supply / discharge oil passage (36) and the fourth supply / discharge oil passage (37) is blocked, and the first supply / discharge oil passage (37) is blocked. Under the front-wheel steering state in which hydraulic pressure is supplied to the oil discharge passage (34) and the second oil supply / discharge oil passage (35), the third oil supply / discharge oil passage (36) and the fourth oil supply / discharge oil passage (37) are provided. ) Is connected to the drain flow path (23) on the rear side direction switching valve (62) side of the double pilot check valve (5). In claim 1,
The first steering cylinder (1) and the second steering cylinder (2) are connected to the first supply / discharge oil passage (34) and the second supply / discharge oil passage (35) to the steer mode valve (6). A hydraulic circuit structure of a steering device, comprising a front / rear selection valve (61) for controlling supply / discharge of hydraulic pressure to / from the hydraulic pressure. In claim 1 or 2,
The third oil supply / discharge oil passage (36) and the fourth oil supply / discharge oil passage (37) are leak oil discharge passages (31), (32) provided in the spool (40) of the rear side direction switching valve (62). The hydraulic circuit structure of the steering device is connected to the drain flow path (23) via In claim 1 or 2,
Check valves (12), (between the double pilot check valve (5) and the rear side direction switching valve (62) in the third supply / discharge oil passage (36) and the fourth supply / discharge oil passage (37). 13) A hydraulic circuit structure of a steering apparatus, wherein the hydraulic circuit structure is connected to a drain flow path (23) via 13).

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