JPH0813545A - Hydraulic circuit in construction machinery - Google Patents

Abstract

PURPOSE:To supply an amount of oil for two pumps to an actuator requiring a large quantity of oil, without adding any piping to the outside of a control valve unit of construction machinery. CONSTITUTION:Operating oil discharged out of a pair of main pumps 2 and 3 is distributed to two valve groups 1a and 1b containing each of symmetrical traveling control valves 11 and 12. In addition a traveling rectilinear value 21 securing a uniform flow supply of operating oil for these symmetrical traveling control valves 11 and 12 is installed in an interval between both these valve groups 1a and 1b. Likewise a two-pup confluent position 21c is installed in this traveling rectilinear valve 21, while those of the operating oil discharged out of the paired main pumps 2 and 3 are joined with each other into a traveling rectilinear valve spool in this position 21c, and a confluent passage 41 for supplying the operating oil to six control valves 13 to 18 available in a turning system and a working machine system is installed there. In succession, a selector valve 43 is selected by dint of pilot pressure of the working machine system control valves 14 and 16 where a large flow rate is required, then the traveling rectilinear valve 21 is selected to a two-pump confluent position 21c by dint of pressure out of a pilot pressure supply route 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a hydraulic excavator,
The present invention relates to a hydraulic circuit in a construction machine such as a loader, and is particularly characterized by a straight traveling valve.

[0002]

2. Description of the Related Art A conventional circuit is shown in FIG. This circuit is used for a control valve unit 1 in a hydraulic excavator as a construction machine.
On the other hand, a hydraulic pipe for supplying pressure oil from a pair of main pumps 2 and 3 is shown. The control valve unit 1 controls hydraulic oil supplied to and discharged from left and right traveling motors (hydraulic motors driving left and right crawler belts). Left and right traveling control valves 11 and 12, a swing control valve 13 for controlling hydraulic fluid supplied to and discharged from a swing motor (a hydraulic motor that swings an upper swing body), and a boom cylinder (boom). Boom first control valve 14 and boom second control valve 15 for controlling hydraulic oil supplied to and discharged from the hydraulic cylinder that rotates the stick, and supply and discharge to the stick cylinder (hydraulic cylinder that rotates the stick). First control valve 16 for sticks and second control valve 17 for sticks for controlling the hydraulic oil to be controlled, and bucket for controlling the hydraulic oil supplied to and discharged from the bucket cylinder (hydraulic cylinder for rotating the bucket) Control valve 18 for Consists of The boom, stick and bucket constitute a front working machine of the hydraulic excavator.

The various control valves 11 to 18 shown in FIG. 2 are switched and operated by pilot pressure oil controlled by an operating lever (not shown), and from the main pumps 2 and 3 to various hydraulic actuators (motors or cylinders). The supplied hydraulic oil is controlled and also the hydraulic oil returned from the actuator to the tank is controlled. However, the piping system for the pilot pressure oil and the piping system for returning the hydraulic oil are general, and therefore omitted.

As shown in FIG. 2, the left and right traveling control valves 11 and 12 are separated into two valve groups 1a and 1b, and the two valve groups 1a and 1b are supplied to the swing system and the working machine system. The other control valves 13 to 18 for controlling the discharged hydraulic oil are divided, and further, between the two valve groups 1a and 1b,
A travel straight valve 21 is provided to ensure equal supply of hydraulic oil to the left and right travel control valves 11 and 12 even when the travel system and the swing system or the working machine system are operated simultaneously.

The traveling straight-ahead valve 21 is for facilitating pipe laying and timber arranging work by causing the machine to move straight even if the turning system or working machine system is operated during traveling. The conventional straight-travel valve 21 has a neutral position 21a.
And straight driving position 21b.

The neutral position 21a is a position which is automatically controlled when only the traveling system, the turning system or the working machine system is operated, and the hydraulic oil discharged from the left and right main pumps 2 and 3 is left and right. Are supplied to the valve groups 1a, 1b directly or via internal passages 22, 23 at the neutral position 21a.

On the other hand, when the turning system and the working machine system are simultaneously operated during traveling, at the neutral position 21a, the amount of oil supplied from the left and right pumps 2, 3 to the left and right traveling systems cannot be maintained and the vehicle goes straight. In that case, the pilot pressure oil automatically supplied to the pilot pressure acting part 24 switches the traveling straight-travel valve 21 to the traveling straight-travel position 21b against the return spring 25 so that the vehicle travels straight. To control.

That is, at the straight traveling position 21b,
The hydraulic oil for the left pump 2 is used for the center bypass passage 31 on the left side.
And the center bypass passage 32 on the right side passing through the internal passage 26, the hydraulic oil of the right pump 3 is supplied only to the left and right traveling control valves 11 and 12, and the parallel feed passage 33 on the right side and the internal passage 27 are supplied. Via the parallel feeder passage on the left
It is supplied to the control valves 13 to 18 of the swing system and the working machine system through 34 and.

Moreover, since the turning system and the working machine system during traveling are moved at a low speed in order to maintain the stability of the machine, a large amount of flow rate is not required. Therefore, the surplus amount of hydraulic oil discharged from the right pump 3 is It is supplied to the left and right traveling systems via an internal passage 27, a check valve 28, an orifice 29 and an internal passage 26 provided at the straight traveling position 21b.

In the hydraulic pipe of this hydraulic excavator, the boom cylinder and the stick cylinder each require an oil amount for two pumps, so two hydraulic oil supply pipes are provided as shown in FIG. The output line of the first control valve 14 for sticks and the output line of the second control valve 15 for booms are connected by an external merging pipe 35. Similarly, the output line of the first control valve 16 for sticks and the second line for sticks are connected. Control valve
This is achieved by connecting the 17 output lines with an external merging pipe 36.

[0011]

As described above, the hydraulic pipe of the conventional control valve unit 1 has the merging pipe 3 outside the hydraulic pipe.
Since it is necessary to add 5, 36, the number of parts and the number of assembling steps increase correspondingly, resulting in cost increase, and there is a problem that the appearance is not clean.

The present invention has been made in view of the above circumstances, and supplies the oil amount for two pumps to an actuator that requires a large amount of oil without adding piping outside the control valve unit. It is an object of the present invention to provide a hydraulic circuit made possible.

[0013]

According to a first aspect of the present invention, hydraulic oil discharged from a pair of main pumps is distributed to two valve groups each including left and right traveling control valves. In a hydraulic circuit of a construction machine in which a straight traveling valve for ensuring equal supply of hydraulic oil to the left and right traveling control valves is provided between the valve groups, the traveling straight valve is provided with two pump merging positions. It is a hydraulic circuit in a construction machine having a structure in which a spool of a straight-ahead travel valve in a merging position is provided with a merging passage for merging hydraulic oil discharged from a pair of main pumps with each other and supplying the merging oil to two valve groups.

According to a second aspect of the present invention, in the hydraulic circuit of the construction machine according to the first aspect, the non-traveling mode is provided in the pilot pressure supply passage for the pilot pressure acting portion on the side for switching the traveling rectilinear valve to the two-pump merging position. A hydraulic circuit with a configuration in which the spool of the traveling linear valve is switched to the two-pump merging position in conjunction with the control valve of the actuator, which sometimes requires a large amount of oil, and a switching valve is provided to release the two-pump merging position during traveling. is there.

[0015]

According to the invention described in claim 1, since the original function of the traveling straight-ahead valve is not required when the vehicle is not traveling, the traveling straight-ahead valve is switched to the two-pump merging position, and the oil amount for two pumps is set by the inner merging passage. Are combined and supplied to an actuator that requires a large amount of oil.

According to the second aspect of the present invention, the pilot pressure supply path is opened by the switching valve that is interlocked with the control valve of the actuator that requires a large amount of oil when the vehicle is not traveling, and the traveling linear valve is switched to the two-pump merging position. , Supply 2 pumps of oil to the required actuator. When traveling, the two-pump merging position is released to maintain the original straight traveling function.

[0017]

The present invention will be described in detail below with reference to the embodiment shown in FIG. Since the basic circuit is the same as that of the conventional example shown in FIG. 2, the same parts are designated by the same reference numerals and the description thereof will be omitted. Further, in this circuit, a portion not related to the present invention is shown as a general parallel circuit.

By improving the traveling straight-travel valve 21, a two-pump merging position 21c for merging the amounts of oil discharged from the pair of pumps 2 and 3 is provided, and merging with the spool of the traveling straight-travel valve 21 at the two-pump merging position 21c. A passage 41 is provided.
The merging passage 41 connects the inner passage 41a corresponding to the left center bypass passage 31 and the parallel feeder passage 34, and the inner passage 41b corresponding to the right center bypass passage 32 and the parallel feeder passage 33. , The working oil discharged from the pair of main pumps 2 and 3 is joined to each other through the joining passage 41, and the two valve groups 1a and 1b are used for a boom cylinder, a stick cylinder or the like that requires a large amount of oil. Supply two pumps of oil.

By thus improving the spool of the straight-travel valve 21, the two pumps are allowed to communicate with each other, and the boom cylinder and the stick cylinder, which require a large amount of oil, have an oil amount of two pumps even in one path. To be able to supply. As a result, the boom second control valve 15 and the stick second control valve 17, which have been conventionally required, are left as a bypass cut valve that simply cuts a bypass oil passage having a simple structure, and a pipe for merging outside is provided. 35, 36 (Fig. 2)
Was unnecessary.

At both ends of the spool of the straight traveling valve 21,
Pilot pressure acting parts 24a, 24b and return springs 25a, 25b are provided. If no pilot pressure oil is applied to any of the pilot pressure acting parts 24a and 24b (only the traveling system operates), return spring
The neutral position 21a is maintained by 25a and 25b.

Further, pilot pressure oil is supplied to the pilot pressure acting portion 24a on the side where the traveling straight traveling valve 21 is switched to the traveling straight traveling position 21b when the traveling system and the swing system or the working machine system are simultaneously operated. The pilot pressure supply passage 42 is connected, and the pilot pressure acting portion 24b on the side for switching the traveling rectilinear valve 21 to the two-pump merging position 21c is connected to the pilot pressure supply passage 44 or the tank line by the switching valve 43.
A pilot pressure supply passage 46 that is selectively communicated with either one of the 45 is connected.

This switching valve 43 is a pilot operated two-position three-position valve for maintaining the original straight traveling function of the straight traveling valve 21.
This is a port switching valve, and the spool of the traveling straight valve 21 is switched by itself switching in conjunction with the operation of the control valves 14 and 16 of the actuator (boom cylinder or stick cylinder) that requires a large amount of oil when not traveling. Is switched to the 2 pump merging position 21c, and the 2 pump merging position 21c is released during traveling.

Therefore, a return spring 47 and one pilot pressure acting portion 48 are provided on one side of the switching valve 43, the other pilot pressure acting portion 49 is provided on the other side, and one pilot pressure acting portion 49 is provided. The pressure acting portion 48 is communicated with a pilot pressure supply passage 51 drawn out from one pilot pressure supply passage 42 of the straight-travel valve 21, and the other pilot pressure acting portion 49 is connected to the boom control valve 14. Pilot pressure supply passage 14a for supplying pilot pressure or pilot pressure supply passage for supplying pilot pressure to the stick control valve 16
16a is in communication via shuttle valve 52 and pilot pressure supply passage 53.

Next, the operation of this embodiment will be described. Only the traveling motor is controlled by the traveling control valves 11 and 12.
When the swivel system or work equipment system is not operated, the traveling straight-ahead valve 21 is located at the neutral position 21a shown in Fig. 1, so hydraulic oil is supplied from the left and right pumps to the left and right traveling control valves 11 and 12, respectively. The forward / backward movement, traveling direction, speed, etc. of the machine body traveling system are determined by the direction control and flow rate control of the traveling control valves 11, 12.

On the other hand, when the turning system and the working machine system are simultaneously operated during traveling, pilot pressure oil is automatically supplied from the pilot pressure supply passage 42 to the pilot pressure acting portion 24a of the traveling straight-travel valve 21, and the pilot pressure is also supplied. The changeover valve 43 is maintained at the position shown in FIG. 1 by the force of the pilot pressure oil supplied from the supply line 42 via the pilot pressure supply line 51 and the force of the spring 47, and the pilot pressure acting portion 24b of the straight travel valve 21 becomes the tank. Since the vehicle is in communication, the straight-travel valve 21 is in the straight-travel position 21.
When the vehicle is switched to b and the turning system and the working machine system are operated as described in the section of the conventional technique, the straight running performance of the vehicle is not affected.

Further, a control valve for a boom cylinder or a stick cylinder that requires a large amount of oil when not traveling
When 14 or 16 is operated by the pilot pressure, the pilot pressure is introduced from the pilot pressure supply passage 14a or 16a to the pilot pressure acting portion 49 of the switching valve 43 via the shuttle valve 52 and the pilot pressure supply passage 53, and the switching valve 43 is opened. Since the switching is performed, the pilot pressure oil supplied to the pilot pressure supply passage 44 communicates with the pilot pressure acting portion 24b of the traveling straight-travel valve 21 via the internal passage of the switching valve 43 and the pilot pressure supply passage 46, and the traveling straight-travel valve Switch 21 to 2 pump merge position 21c.

Since the traveling straight-ahead valve 21 when not traveling does not have to fulfill the original traveling straight-ahead function, if the boom control valve 14 is operated at the two-pump merging position 21c, the two pumps 2, 3 The hydraulic fluid discharged from the
And the oil amount for two pumps can be supplied to the boom cylinder through the boom control valve 14. Similarly, if the stick control valve 16 is operated,
The hydraulic oils discharged from the two pumps 2 and 3 are merged in the internal merge passage 41 and supplied to the parallel feeder passage 34,
The oil amount for two pumps can be supplied to the stick cylinder through the stick control valve 16.

In this way, when the vehicle is not traveling, the traveling rectilinear valve 21
Supplies the amount of oil for 2 pumps to the required actuator from 2 pumps, but when the traveling system operates, 2 pumps merge position 21c
Is automatically released, and the straight-travel valve 21 is in the neutral position 21.
It can be switched to a or straight driving position 21b.

As described above, by improving the spool of the straight-travel valve 21, the two-pump merging function can be obtained without adding a dedicated communication spool, and without adding external pipes or hoses. A maximum of 2 pumps of oil can be supplied to an actuator that requires a large amount of oil.

In the example of FIG. 1, the control valves 15 and 17 are
Has only the function of cutting the bypass line, so the structure is simple, and here, the boom and stick are explained as an example.For example, one valve group 1b has an attachment control valve. In some cases, by introducing the signal pressure of the attachment to the pilot pressure acting portion 49 via the shuttle valve, it is possible to cope with an attachment requiring a two-pump merging oil amount without external merging piping.

[0031]

According to the first aspect of the present invention, the traveling straight valve is provided with the two-pump merging position, and the spools have their hydraulic fluids discharged from the pair of main pumps merging with each other to form two valve groups. Since a merging passage for supplying oil to the
The external pipe for pump merging can be deleted, and the oil amount of 2 pumps can be merged in the spool of the traveling straight valve without newly adding a dedicated communication spool, for actuators that require a large amount of oil. Can supply the required amount of oil.

According to the second aspect of the present invention, by adding a switching valve to the traveling straight-ahead valve, the traveling straight-ahead valve has a two-pump merging function when the vehicle is not traveling and at the time of traveling, the original traveling straight-traveling function is provided. Can be maintained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a hydraulic circuit in a construction machine of the present invention.

FIG. 2 is a circuit diagram showing a hydraulic circuit in a conventional construction machine.

[Explanation of symbols]

 1a, 1b Valve group 2, 3 Main pump 11, 12 Travel control valve 21 Travel straight valve 21c 2 Pump merging position 24b Pilot pressure acting part 41 Merging passage 43 Switching valve 44 Pilot pressure supply passage

Claims (2)

[Claims] 1. The hydraulic fluid discharged from a pair of main pumps is distributed to two valve groups each including a left and right traveling control valve, and the left and right traveling control valves are distributed between the two valve groups. In a hydraulic circuit of a construction machine provided with a straight traveling valve for ensuring equal supply of hydraulic oil, the traveling straight valve is provided with a two-pump merging position, and a pair of mains are provided on the spools of the straight traveling valve at the two-pump merging position. A hydraulic circuit in a construction machine, comprising: a confluent passage that supplies hydraulic oil discharged from a pump to two valve groups. 2. A straight traveling straight line is interlocked with a control valve of an actuator, which requires a large amount of oil when not traveling, in a pilot pressure supply passage for a pilot pressure acting portion on the side where the straight traveling valve is switched to a two-pump merging position. 2 spools of valve
The hydraulic circuit for a construction machine according to claim 1, further comprising a switching valve that switches to a pump merging position and releases the two pump merging positions during traveling.