JPH0575679B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lift control device having a locking function for a load lifting lift in a cargo handling forklift and similar working machines (hereinafter simply referred to as a forklift).

[Conventional technology]

The lifting and lowering of the cargo handling fork of the forklift mentioned above is carried out by hydraulic pressure. When ascending, pressure oil is sent into the lift cylinder, and when descending, the pressure oil in the cylinder is pushed out by the weight of the load, etc. A structure has been adopted that returns the Therefore, by operating the switching valve even when the engine is stopped, the pressure oil in the lift cylinder is discharged and the lift cylinder moves downward, so if the switching valve is operated for some reason when the operator is not present, the load will be lowered. and is extremely dangerous.

Therefore, as a safety measure, there is a method of mechanically locking the switching valve, or a solenoid-type two-position two-way valve is installed in the circuit between the switching valve and the shift cylinder, and when the engine ignition switch is on, the solenoid valve is closed. is turned on, the circuit between the switching valve and the lift cylinder is connected, and the above switch is turned on.
When the solenoid valve is turned off, the solenoid valve is also turned off, closing the circuit and attempting to prevent the cargo from descending even if the switching valve is operated.

However, this method requires the addition of a separate device in addition to the switching valve, resulting in high costs and problems with installation space.

For this reason, the present inventors previously proposed an operating valve having a structure in which a lift lock valve is provided within the lift lifting/lowering operating valve (Japanese Patent Application Laid-open No. 223798/1982). This is designed to have a lock function that prevents pressure oil from returning from the lift cylinder when the supply of pressure oil to the operation valve is stopped, regardless of the operation of the operation valve.

[Problem that the invention seeks to solve]

That is, this lift operation valve has a lift lock valve installed in the passage between the lift spool and the lift cylinder, and this lift lock valve has the function of a load check valve and is operated by pressure oil sent from a pump. The circuit is opened by the valve, allowing return oil from the lift cylinder to flow to the tank. When the pump is stopped, pressure oil is not supplied to the pilot valve, and therefore the logic valve does not operate, so the lift spool cannot be moved. Pressure oil is prevented from being discharged from the lift cylinder.

However, in this case, the oil pressure for operating the pilot valve increases to its maximum value during work (when the lift is raised) and constantly fluctuates. Moreover, the above-mentioned lift lock valve needs to operate a pilot valve to allow the circuit to open not only when the lift is lowered but also when the lift is raised, so that leaks do not occur even at the highest pressure (for example, 200 kgf/cm ² ), and the pump pressure The pilot valve operates even during idling operation when the pilot valve is close to 0, and it is necessary to open the lock valve and lower the pilot valve, which poses problems in the structure and durability of the pilot valve.

In view of this, an object of the present invention is to form a comparatively low-pressure hydraulic circuit with priority, operate the pilot valve using this circuit, and solve the above-mentioned problems.

[Means for solving problems]

To achieve the above object, the present invention disposes a priority type flow divider on the inlet side of a center bypass type 3-position lift operation spool valve, and this flow divider always prioritizes a predetermined low pressure pressure oil to a priority circuit. A logic valve is interposed in the spool valve, the lift cylinder, and the cylinder circuit to prevent backflow, and a pilot check valve is removably disposed in the pilot passage of the logic valve,
The check valve is opened and closed by low pressure hydraulic pressure generated in the priority circuit by operating the spool valve.

[Effect]

The pilot valve uses relatively low pressure hydraulic pressure in the priority circuit to generate a required pressure of at least 6 kg/ ^cm2 only during load processing, reducing energy loss in the hydraulic system and increasing reliability with less shock. It is durable and can be expected to have a long life.

〔Example〕

1 to 6 relate to embodiments of the present invention.

In this embodiment, a lift control device 1, a tail (back and forth tilting of a fork) operation valve 2, and an end cover 3 are combined to form a composite valve A, and the tail operation valve 2 is a well-known center bypass type 3-position manual spool. It is a valve, and its explanation will be omitted.

The lift control device 1 of the present invention includes a pressure oil inlet hole 5 connected to a pump P in a valve body 4,
A spool valve 6 for lift operation, and a pressure oil supply passage 7 connecting the inlet hole 5 and the spool valve 6.
A priority flow divider 8 is provided. The lift operation spool valve 6 is a center bypass type 3-position manual spool valve like the tail operation valve 2, and the pressure oil sent out from the center bypass passage 9 of the lift operation spool valve 6 is transferred to the center of the tail operation valve 2. Bypass passage 2
a and the exhaust passage 3a of the ent cover 3 to be discharged into the tank T.

The flow divider 8 forms an inner hole 10 with a bottom, and a spring 12 is inserted between the flow divider 8 and a relief valve 11 attached to the valve body 4, and the tip thereof is connected to the flow regulator 13 side, which is also attached to the valve body 4. press against. An orifice 15 that opens to the pressure oil supply passage 7 and communicates with the inner hole 10 is bored on the outer periphery, and a pressure introduction hole 17 that is out of phase with this and communicates with the center hole 16 at the tip is bored at the center of the spool valve 6 for lift operation. The bypass passage 9 and the pressure oil supply passage 7 are cut off by a flow divider 8.

As a result, when the amount of oil sent from the pump P is less than the priority flow rate, the oil enters the inner hole 10 from the passage 7 via the orifice 15 and flows into the priority circuit 18 communicating with the inner hole 10. This priority circuit 18 is connected to the second left land 43 side of the lift operation spool valve 6, which will be described later, together with the relief valve 11, and to the load check valve 21 via a passage 20. The passage is not blocked by the land 43 and is connected to the check valve 23 via the passage 22.

The load check valve 21 and the check valve 23 have a well-known structure, and a circuit diagram thereof is shown in FIG. 4. The pressure oil that has passed through each of these check valves 21 and 23 is supplied to, for example, a power steering PS.

The flow divider 8 is pushed out between the pressure introduction hole 17 and the flow regulator 13,
Retraction is restricted by a spring 12, and the pump P
As the amount of oil supplied increases, the flow divider 8 moves backward against the spring 12, and the pressure oil supply passage 7 communicates with the center bypass passage 9 of the lift operation spool valve 6.

The relief valve 11 has a horizontal hole 31 in the outer periphery of the socket 30 that communicates with the priority passage 18, and when the pressure oil flowing from the horizontal hole 31 into the inner hole 32 reaches the maximum pressure set in the priority circuit 18, Poppet 3
3 against the spring 34, and open the horizontal discharge hole 3.
5 to the tank passage 36. This set maximum pressure is the limit necessary for operating the power steering PS, and is set to, for example, 100 kg/cm ² .

The spool 40 of the spool valve 6 for lift operation has first, second, third, and fourth lands 42, 43, 44, 45 on the left side of the center land 41, and first and second lands 46, 47 on the right side. Equipped with a spool of 40
When in the neutral position, the priority circuit 18 is activated as described above.
is open between the first left land 42 and the second left land 43 with respect to the spool fitting hole 48 .

The lift operating spool valve 6 has an operating passage 50 formed on the right side of the center bypass passage 9. At the neutral position of the spool 40, the center bypass passage 9 and the operating passage 50 are cut off by the right first land 46, and the spool 40 is located on the left side. When moving in this direction, both passages 9 and 50 are communicated. However, 46a is a notched groove. Conversely, when moving the spool 40 to the right, the operating passage 50 communicates with the tank passage 36. However, 47a is a notch groove provided in the second right land 47.

The operating passage 50 is connected to a logic valve 51. This logic valve 51 includes a stepped spool 52 facing the passage 50 and a spring 54 that presses the spool 52 against the valve seat 53. Normally, an outer valve chamber 55 is formed on the outer periphery of the spool by the spool 52.
and the operating passage 50 are cut off. This extra-valve chamber 55 communicates with a horizontal groove 61 formed on the outer periphery of the flow regulator 13 through a passage 60, and the supplied pressure oil passes from this horizontal groove 61 through a horizontal hole 63 of a regulator piston 62. It then enters the inner chamber 64, passes through the orifice 65, reaches the cylinder passage 66, and is supplied to the lift cylinder B via the connecting pipe 67.

The inner hole 56 housing the spool 52 of the logic valve 51 is connected to a pilot check valve 70 via a pilot passage 57. This check valve 70 has a valve chamber 72 formed in a case 71 that is detachably attached to the valve body 4.
A poppet 73 is housed in the valve seat 73, and a spring 74 presses the poppet 73 against a valve seat 75 to shut off the valve chamber 72 and the lower chamber 76, and the pilot passage 57 communicates with the valve chamber 72.

A piston 77 is housed in the lower chamber 76 facing the poppet 73, and is biased by a spring 78 in a direction away from the poppet 73. In addition, at the bottom of the lower chamber 76, there is a small hole 7 with a short and small length located at the axis center.
9 and an orifice 80 that communicates with it, a hydraulic fluid introduction hole 81 is provided coaxially with the orifice 80 that communicates with the orifice 80. At a position facing the left third land 44 , the introduction hole 81 is located between the left second land 43 and the left third land 44 and opens into the fitting hole 48 .

In the figure, reference numeral 82 is a drilled hole that communicates the outer chamber 83 that communicates with the lower chamber 76 and the tank passage 36 .

Further, the downward convex portion of the piston 77 does not come out of the small hole 79 even in the raised position, and
9 communicates with orifice 80.

In the above configuration, the lift operation spool valve 6
When the spool 40 of is in the neutral position (Fig. 1),
When the pressure oil supplied from the pump P is relatively small, the priority type flow divider 8 is placed in the position shown in FIG. 1 by the spring 12, and pressure oil is supplied only to the priority circuit 18. The orifice 80 and introduction hole 81 for the pilot check valve 70 are connected to the priority circuit 18 by the left second land 43 of the spool 40.
is blocked.

When the amount of oil supplied from the pump P increases and reaches a predetermined amount, the oil pressure applied between the tip of the flow divider 8 and the flow regulator 13 increases due to the pressure drop at the orifice 15, and the flow increases. The divider 8 moves to the relief valve 11 side against the spring 12, the pressure oil supply passage 7 communicates with the center bypass passage 9, and the pressure oil flows from the center bypass passage 2a of the tail operation valve 2 to the discharge passage of the ent cover 3. It is returned to tank T via 3a.

Note that when the spool 40 is in the neutral position, the pilot check valve 70 is activated by the priority circuit 18 as described above.
and the piston 77 does not operate.
Therefore, the check valve 70 is in a closed state, and the stepped spool 52 of the logic valve 51 is in the outer valve chamber 55.
Even when pressure is applied from the lift cylinder B, the load does not move and remains pressed against the valve seat 53, and the cargo is not raised or lowered but is stopped.

Next, when supplying pressure oil to the lift cylinder B for lifting the load, the lift spool 40 is moved to the left as shown in FIG. As a result, the center land 41 and the first right land 46 block the outlet side of the center bypass passage 9, and the center bypass passage 9 communicates with the operating passage 50.

At the same time, the second left land 43 moves to the left, but the priority circuit 18 does not communicate with the introduction hole 81 for the pilot check valve 70, and the piston 77 and poppet 73 are the same as in the neutral position described above, and the logic valve chamber 56 is reliably closed by a check valve 73, and the pressure oil applied to the operating passage 50 simply acts as a check valve, pushing up the stepped spool 52 of the logic valve 51, reaching the valve outer chamber 55, and then stopping the flow. It is supplied to the lift cylinder B via the regulator 13 to lift the load.

Next, when lowering the load, the lift spool 40 is moved to the right (FIG. 6). in this case,
Although the center land 41 blocks one outlet of the center bypass passage 9, the left first land 42 does not block the outlet, so that the pressure oil flowing into the center bypass passage 9 flows out to the tail operation valve 2 side.

At the same time, the left second land 43 moves rightward, the priority circuit 18 and the introduction hole 81 communicate with each other, the piston 77 of the pilot check valve 70 is pushed up by the pressure oil of the priority circuit 18, and the poppet 73 is pushed up. This allows the pilot passage 57 to connect to the valve chamber 7.
2. It communicates with the tank passage 36 through the lower chamber 76 and the drilled hole 82, and the pressure in the inner hole 56 of the logic valve 51 decreases.

The outer diameter of the spool 52 of the logic valve 51 has a step, and the stepped spool 52 rises due to the pressure from the lift cylinder B, forming the outer valve chamber 55 and the operating passage 50.
communicate with. At this time, the right first land 46 of the lift spool 40 blocks the center bypass passage 9 and the operating passage 50, and the right second land 47 communicates the operating passage 50 with the tank passage 36, so that the lift cylinder The pressure oil in B is discharged to the tank T side, and the lift cylinder is lowered. In this case, the sudden backflow from the cylinder will cause the flow regulator 1
When the piston 62 of No. 3 is pushed back against the spring 68, the degree of overlapping between the lateral groove 61 and the lateral hole 63 is reduced, and the reverse flow speed, that is, the descending speed of the load is regulated.

Next, when the pump P is stopped, that is, when pressure oil is not supplied, no pressure is generated in the priority circuit 18, so the pilot check valve 70 does not operate regardless of the position of the lift spool 40. The poppet 73 is in complete contact with the valve seat 75, blocking the pilot passage 57, and therefore the logic valve 51 is also in a closed state. Therefore, even if the lift spool 40 is operated by mistake, the load will not be lowered.

In addition, 58 in the figure is an orifice that penetrates the inside and outside of the stepped spool 52, and when the stepped spool 52 is in contact with the valve seat 53 and the cargo is stopped at an arbitrary position, by providing this orifice 58, Since the inner hole 56 is maintained at the same pressure as the outer valve chamber 55, the spool 52 is seated in complete contact with the seat 53, and leakage into the passage 50 is suppressed to a negligible level.

Further, in Fig. 4, 90 is a main relief valve, which regulates the maximum working pressure of compound valve A.
For example, it is set to 200Kg/cm ² .

Next, when lifting or lowering a load, depending on the purpose of use or other reasons, the above-mentioned locking action may not be necessary when the pump is stopped. Normally, the structure of the lift control device is different for a lift control device with a locking mechanism and one without a locking mechanism, and each lift control device is manufactured separately, and one of them is selected and installed. Therefore, for example, when a lift control device without a locking mechanism is installed and used, if it is desired to change the operation to one that requires a locking mechanism, the entire device must be replaced, which is a disadvantage.

According to the present invention, compatibility between the two can be achieved simply by replacing only the pilot check valve. FIG. 7 shows a case in which the locking action is removed in the above-mentioned lift control device with a lock, and FIG. 8 is a circuit diagram thereof.

That is, remove the pilot check valve 70,
In place of this, a pilot circuit regulating valve 100 (hereinafter simply referred to as a cartridge) is installed.

This cartridge 100 is installed in the pilot passage 5.
7, and a vertical hole 102 that communicates with the horizontal hole 101. The lower end of the vertical hole 102 opens to the lower surface, and when assembled to the valve body 4, opens into the small hole 79, and the introduction hole 81. is cartridge 1
00 is closed at the lower surface.

As a result, when the lift spool 40 is in the neutral position (FIG. 7), the orifice 80 connected to the small hole 79 is closed by the left third land 44 of the spool 40, and the logic valve 51 is connected to the cylinder. Even if pressure is applied from the B side, the circuit will not open and the cargo will be maintained in that position.

When pulling the lift spool 40 to the left when lifting the load (Fig. 5), the lift spool 40
The second left land 43 and the third left land 44 do not communicate with the tank passage 36, so the inner hole 56 of the logic valve 51 is maintained at the same pressure as the passage 55, and the stepped spool 52 is Pushed up by the pressure, it acts as a mere check valve, and the load rises in the same manner.

In addition, when descending, by pushing the lift spool 40 to the right (Fig. 6), the left third
Tank passage 3 is between land 44 and left fourth land 45
6, and the pressure of the priority circuit 18 is transmitted to the orifice 81, but it is blocked by the seal S and the orifice 80 is opened to the tank passage 36. Therefore, the cargo is lowered in the manner described above.

〔Effect of the invention〕

According to the present invention, a logic valve is provided in the operating circuit connecting the lift operation spool valve and the lift cylinder, and a pilot check valve for opening and closing the logic valve and the pilot passage is provided, and the lift operation spool valve is connected to the lift cylinder. A priority type flow divider is arranged on the inlet side, and the predetermined low-pressure pressure oil is always supplied to the priority circuit with priority, and the pilot check valve mentioned above supplies the minimum oil pressure to the priority circuit only when the lift operation spool is operated to the lowered position. (For example, 6Kg/
cm ² ), the hydraulic system energy loss is minimal. Moreover, the pilot pressure required to open the pilot check valve is the highest pressure in the priority circuit, and can be suppressed to a low pressure regardless of the highest pressure applied to the lift cylinder.
Therefore, heat generation and shock can be prevented, and damage to related parts can be prevented.
It has effects such as increasing durability.

Furthermore, since the pilot check valve is removably attached, it is possible to replace it with an appropriate valve if the user requests that a lift lock is not required when the pump is stopped.

[Brief explanation of the drawing]

1 to 6 relate to embodiments of the present invention, FIG. 1 is a vertical cross-sectional view, and FIG. 2 is an illustration of the X--
A cross-sectional view along the Y line, FIG. 3 is the Y- in FIG.
A sectional view taken along the Y line, Fig. 4 is a hydraulic circuit diagram, Fig. 5 is an explanatory diagram of the operation when the lift is raised, Fig. 6 is an explanatory diagram of the operation when the lift is lowered, and Figs. 7 and 8 omit the lift lock. In this case, FIG. 7 is an explanatory diagram thereof, and FIG. 8 is a hydraulic circuit diagram. 1 is a lift control device, 6 is a spool valve for lift operation, 8 is a priority type flow divider, 18 is a priority circuit, 51 is a logic valve, 51 is a pilot passage,
70 is a pilot check valve, and B is a lift cylinder.

Claims (1)

[Claims] 1. A priority type flow divider is disposed on the inlet side of a center bypass type 3-position lift operation spool valve, and this flow divider always supplies predetermined low-pressure pressure oil to a priority circuit with priority. A logic valve is interposed between the spool valve, the lift cylinder, and the cylinder circuit to prevent backflow, and a pilot check valve is removably disposed in the pilot passage of the logic valve, and the check valve is connected to the spool valve. A lift control device with a lock, characterized in that it is opened and closed by low pressure hydraulic pressure generated in the priority circuit when operated. 2. The lift control device with a lock according to claim 1, wherein the pilot check valve is detachable from the valve housing.