JPH06228986A - Cooling device for service car - Google Patents

Abstract

PURPOSE:To reduce engine load torque at the time of operation requiring high horse power by providing a detecting signal outputting a high load signal and a control means interrupting power transmission to a compressor for a prime mover regardless of the presence of a compressor operation command by the high load signal. CONSTITUTION:A pressure switch 62 is used for a detecting means and a one- shot multivibrator IC 63, an integrating circuit 64 and a relay 65 are used for control means. When soil and sand loading operation is effected, a directional control valve 53 for a boom is changed over to the position U of elevation, and a boom cylinder 32 is elongated, and lifted together with the boom 31. A heavy load is exerted to the bottom chamber of a boom cylinder 33 by the weight of soil and sand, etc., in a bucket 32, the pressure of a duct 72 is increased, and the switch 62 is turned on. A high level signal is input to the input terminal A of the IC 63 from a low voltage circuit 61, and the high level signal is output from an output terminal Q, and the relay 65 is turned off. The supply of electricity to the electromagnetic clutch 1a of a compressor 1 is interrupted, and a power interrupting state is brought about, thus stopping the compressor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device mounted on a work vehicle such as a wheel loader, and more particularly to a compressor for controlling a compressor according to the state of a working machine.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional cooling device mounted on a wheel loader (FIG. 7). In the figure,
Reference numeral 1 is a compressor that is driven by an unillustrated engine (motor) to pump the refrigerant, 2 is a blower fan driving motor (hereinafter, blower fan motor) that sends air into the vehicle interior, and 3 is a condenser (condenser) cooling fan It is a driving motor (hereinafter referred to as a cooling fan motor).

Now, when the ignition switch 11 is turned on in the state shown in the figure, an engine (not shown) is driven and both the battery relay 14 and the air conditioner relay 15 are turned on, and then the air conditioner switch 12 is turned on (a compressor operation command is issued). Output), relay 14,
The electromagnetic clutch 1a of the compressor 1 is excited via 15, the air conditioner switch 12, the thermostat 16 and the refrigerant pressure switch 17. As a result, the electromagnetic clutch 1
When a is in the power transmission state, the power of the engine is transmitted to the compressor 1, the compressor 1 operates, and the refrigerant flows through a circulation passage (not shown). Also, the fan switch 19 is L
When it is switched to any one of the o position, the Me position, and the Hi position, the blower fan motor 2 is energized to drive the blower fan, and the air passes through an evaporator (not shown) connected to the circulation passage to pass through the vehicle interior. Be blown to.

When the compressor 1 is driven,
The refrigerant in the circulation passage is vaporized by the evaporator, whereby the air from the blower fan is cooled by the evaporator and blown into the vehicle compartment, thereby cooling the vehicle compartment. The voltage applied to the blower fan motor 2 increases in the order of Lo → Me → Hi, and the blower fan air volume increases accordingly. The condenser relay 18 is turned on in accordance with the turning on of the air conditioner switch 12, whereby the cooling fan motor 3 is energized to drive the cooling fan and cool the condenser. Further, the thermostat 16 automatically turns off when the temperature related to the evaporator falls below a predetermined value to stop the compressor 1, thereby preventing freezing of the evaporator. Further refrigerant pressure switch 17
Automatically turns off when the refrigerant pressure exceeds a predetermined value to stop the compressor 1, thereby preventing damage to the compressor 1 and the like.

[0005]

By the way, in this type of wheel loader, a working hydraulic pump (not shown) driven by an engine and a boom cylinder 33 (FIG. 7) driven by oil discharged from the hydraulic pump. And a bucket cylinder 34, and these cylinders 33, 3
The boom 31 and the bucket 32 (work machine) are driven by 4 to perform excavation work and the like. FIG. 7 shows a state in which the boom 31 is lowered, scooping earth and sand into the bucket 32, and
And then dump the dirt in the bucket 32 into the dump truck D.
The work of loading in C is shown. In this type of work, in order to shorten the work cycle time, the operation of moving the vehicle forward toward the dump truck DC and the operation of raising the boom 31 are performed at the same time when loading sand.

However, in the conventional cooling device shown in FIG. 6, the drive control of the compressor 1 is performed without taking into consideration the drive state of the working machine, so that there is the following problem. That is, as described above, when loading the earth and sand, the vehicle is traveling and the boom 31 is raised at the same time, and particularly, the raising operation of the boom 31 requires high horsepower. However, if the compressor 1 is operating at this time, not only the vehicle traveling speed decreases because the load torque of the engine increases, but also the discharge amount of the hydraulic pump decreases and the ascending speed of the boom 31 decreases. Therefore, there is a problem that working efficiency is reduced.

An object of the present invention is to provide a cooling device for a work vehicle, which automatically stops the compressor during work requiring high horsepower to reduce the engine load torque.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 showing an embodiment, the present invention will be described. In the present invention, a working hydraulic pump 51 driven by a prime mover 41 and the hydraulic pump 51 are provided.
Mounted on a work vehicle equipped with a work machine hydraulic cylinder 33 that drives the work machine 31 by being driven by oil discharged from the engine, and transmits the power of the prime mover 41 to the cooling compressor 1 in response to a compressor operation command It is applied to a cooling device that operates the compressor 1. And
The detection means 62 that detects that the load of the work machine 31 has exceeded a predetermined value and outputs a high load signal, and when the high load signal is output, the compressor 1 of the prime mover 41 regardless of the presence or absence of a compressor operation command. Means 6 for cutting off power transmission to the vehicle
3 to 35 are provided to solve the above problems. In particular, claim 2 is to transmit the power of the prime mover 41 to the compressor 1 in response to a compressor operation command when a predetermined time has elapsed after the power transmission of the prime mover 41 to the compressor 1 was cut off. Claim 3
When the output of the high load signal is cut off after the power transmission of the prime mover 41 to the compressor 1 is cut off, the power of the prime mover 41 is transmitted to the compressor 1 in response to the compressor operation command. . Further, claim 4 further comprises command means for outputting a cancellation command for canceling the power cutoff to the compressor 1, and when the cancellation command is output, the compressor operation command is output even when the high load signal is output. In response, the power of the prime mover 41 is increased by the compressor 1
It is intended to be transmitted to.

[0009]

The detecting means 62 detects that the load of the work machine 31 has exceeded a predetermined value and outputs a high load signal. When the high load signal is output, the control means 63 to 65 cut off the power transmission from the prime mover 41 to the compressor 1 regardless of the presence or absence of a compressor operation command. As a result, the load torque of the prime mover 41 can be reduced and the prime mover speed can be increased.

Incidentally, in the section of means and action for solving the above problems for explaining the constitution of the present invention, the drawings of the embodiments are used for the purpose of making the present invention easy to understand. It is not limited to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the construction of a working hydraulic circuit of a wheel loader and a cooling device. The same parts as those in FIGS. 6 and 7 are designated by the same reference numerals. The power of the engine indicated by reference numeral 41 is transmitted to the axle 44 via the torque converter 42 and the transmission 43, whereby the vehicle travels. Further, the discharge oil of the working machine hydraulic pump 51 driven by the engine 41 passes through the bucket directional control valve 52 and the boom directional control valve 53, and then the bucket cylinder 3 is discharged.
4 and the boom cylinder 33, and the bucket 32 and the boom 31 are driven by expansion and contraction of the cylinders 34 and 33. The direction control valves 52 and 53 are switched by levers 52a and 53a provided on the driver's seat.

Next, the structure of the cooling device will be described.
Reference numeral 61 is a constant voltage circuit, which always holds the voltage of the battery at a constant voltage and outputs it. 62 is both control valves 52,
This is a pressure switch that turns on when the pressure in the pipe line 72 between 53 exceeds a predetermined value, and when the pressure switch 62 is turned on, the output (high level signal) of the low voltage circuit 61 is the input terminal A of the one-shot multi IC 63. Entered in. The one-shot multi IC 63 is composed of a flip-flop and, as shown in FIG. 2, outputs a high level signal from the output terminal Q in synchronization with the rising of the input terminal A from the low level to the high level.

Reference numeral 64 is a capacitor 64a and a register 64.
b is an integrating circuit composed of
By the action of, the high level signal from the output terminal Q is held for a predetermined time T. The predetermined time T is, for example, slightly longer than the time required for the boom 31 to rise from the lowest stage to the highest stage. Reference numeral 65 denotes a relay which is turned on when the output terminal Q of the one-shot multi IC 63 is low level, and is turned off when the high level signal is output from the terminal Q. When the relay 65 is turned off, the electromagnetic clutch 1a of the compressor 1 is de-energized regardless of whether the air conditioner switch 12 is turned on or off, and the power of the engine 41 is not transmitted to the compressor 2 and the compressor 1 is stopped.

Reference numeral 67 is a selection switch for selecting whether or not to carry out the control according to the present invention, which is turned on / off by operating an operation button provided on either of the work levers 52a and 53a. When the selection switch 67 is turned off, the output terminal Q of the one-shot multi IC 63 and the relay 65 are disconnected, and the relay 65 always keeps the on state. Reference numeral 66 is a damper for protecting the pressure switch 62 by absorbing the pressure pulsation of the conduit 72.

Next, the operation of the embodiment will be described. (1) When the selection switch 67 is on: FIG. 1 shows a state where the thermostat 16 and the refrigerant pressure sensor 17 are on, and the ignition switch 11, the air conditioner switch 12 and the selection switch 67 are on. Therefore, the engine 41 is stopped, and the compressor 1 and the hydraulic pump 51 are stopped. Further, since the pressure switch 62 is also off, the output terminal Q of the one-shot multi IC 63 is low level and the relay 65 is on. In this state, turn on the ignition switch 11 to turn on the engine 41.
Is activated and the air conditioner switch 12 is turned on,
Both the battery relay 14 and the air conditioner relay 15 are turned on, and the electromagnetic clutch 1a of the compressor 1 is excited via the air conditioner switch 12, the thermostat 16, the refrigerant pressure switch 17 and the relay 65 to be in the power transmission state.

As a result, the power of the engine 41 is transmitted to the compressor 1 to operate the compressor 1 and the refrigerant flows through a circulation passage (not shown). When the fan switch 19 is switched to the Lo position, the Me position, or the Hi position in this state, the blower fan motor 2 is driven at a speed according to the position.
Is driven to operate the blower fan. Here, when the compressor is driven, the refrigerant is vaporized by an evaporator (not shown) provided in the circulation passage, whereby the air from the blower fan is cooled by the evaporator and blown into the vehicle interior. The condenser relay 18 is turned on along with the turning on of the air conditioner switch 12, whereby the cooling fan motor 3 is driven and the cooling fan (not shown) is driven.

On the other hand, the working hydraulic pump 51 is driven by the operation of the engine 41, and the pressure oil is discharged to the pipe 71. In the state of FIG. 1, since both control valves 52 and 53 are both in the neutral position, the oil discharged from the hydraulic pump 51 is discharged from the pipes 71 to 71.
It is returned to the tank through 73. Therefore, the pressure in the pipe line 72 is less than the predetermined value, and the pressure switch 62 maintains the off state. When the bucket directional control valve 52 is switched by the operation lever 52a while the compressor 1 is driven, the bucket cylinder 34 is extended or contracted by the oil discharged from the hydraulic pump 51 to drive the bucket 32. At this time as well, the pressure in the conduit 72 is less than the predetermined value, and the pressure switch 62 is off.

When carrying out the earth and sand loading work shown in FIG. 7, the lever 53 is operated while the vehicle is running.
When the boom directional control valve 53 is switched to the raised position U by a, the oil discharged from the hydraulic pump 51 is discharged from the boom cylinder 3
The boom cylinder 33 is extended by being guided to the bottom chamber of No. 3,
The boom 31 rises. At this time, the boom cylinder 33
A large load is applied to the bottom chamber by the total weight of the boom 31, the bucket 32, and the earth and sand in the bucket 32. Therefore, the pressure in the pipe 72 becomes a predetermined value or more. As a result, the pressure switch 62 is turned on, and the high level signal from the low voltage circuit 61 is input to the input terminal A of the one-shot multi IC 63 (time point t1 in FIG. 2A). A high level signal is output from the output terminal Q in synchronization with the rising of the input terminal A from the low level to the high level (FIG. 2B), and the relay 65 is turned off. Therefore, the power supply to the electromagnetic clutch 1a of the compressor 1 is cut off and the power is cut off (OFF) (FIG. 2 (c)), that is, the power of the engine 41 is not transmitted to the compressor 1 and the compressor 1 is stopped.

Here, for example, when the control valve 53 is returned to the neutral position at the time t2, the pressure switch 62 is turned off and the input terminal A of the one-shot multi IC 63 becomes low level. Since the high level signal from the output terminal Q is held for a predetermined time T, the relay 65 holds the off state until the time T elapses. Therefore, the power-off state of the electromagnetic clutch 1a also continues for the time T, and the compressor 1 stops only during this period. After that, when the time T elapses, the output terminal Q of the one-shot multi IC 63 becomes low level at time t3, and the relay 6
5 is turned on and the electromagnetic clutch 1a is in the power transmission state (on)
Then, the compressor 1 is driven. Further, even when the on time of the pressure switch 62, that is, the time when the input terminal A is held at the high level is between the time points t4 and t5 in FIG. 2, the off time of the compressor 1 is T. As described above, the time T is slightly longer than the time required for the boom 31 to rise from the lowermost stage to the uppermost stage (between time points t4 and t5). 1 will operate.

As described above, in this embodiment, the rise of the boom 31 is detected by the pressure switch 62, and until the predetermined time T elapses from the start of the rise, the compressor 1 is turned on regardless of whether the air conditioner switch 12 is on or off. Since the engine power transmission is cut off, the engine load torque can be reduced and the engine speed can be increased when the boom is raised, and a decrease in vehicle traveling speed and a decrease in the working machine rising speed can be prevented. This will be described in detail below. FIG. 3 is a diagram showing the relationship between the engine speed and the engine torque. In the figure, ET is the engine torque curve under no load, TT is the absorption torque of the torque converter 42, and ETA is the load torque Tp of the working hydraulic pump 51 and the absorption torque Tc of the compressor 1 are the engine torque. A torque curve subtracted from the curve ET is shown. According to this, the engine torque when the vehicle is running and the boom is raised at the same time when the compressor is operating as shown in FIG. 7 is the above ETA, but the static constant rotation speed of the engine 41 at this time is the torque curve ETA. Speed N at the intersection PA between the torque converter absorption torque TT and the torque converter TT
a. Further, when the discharge flow rate per one rotation of the hydraulic pump 51 is q and the bottom side area of the boom cylinder 33 is S, the rising speed V of the boom 31 when the engine speed is Na is:

## EQU1 ## V = q × Na / S In the present embodiment, when the boom is raised, the compressor 1 is stopped and the absorption torque Tc of the compressor 1 is increased.
Is zero, the engine load torque is reduced by that amount and the engine torque curve becomes ETB, and the static rotation speed of the engine 41 when the vehicle travels and the boom rises simultaneously is Nb (> Na). Become. Therefore, the engine speed is increased by Nb-Na compared to when the compressor is operating, and the vehicle traveling speed and the boom rising speed V can be increased.

When the boom directional control valve 53 is switched to the lowering position D or the floating position F, the boom 31 descends due to hydraulic pressure or its own weight. The pressure in line 72 remains below a predetermined value, so pressure switch 62 does not turn on and compressor 1 remains active. When the bucket 32 is not loaded with earth and sand, the pressure switch 62 does not turn on because the load is small even when the boom is raised, and the compressor 1 maintains the operating state. The pressure switch 62 may be configured so that it is always turned on when the boom is raised.

(2) When the selection switch 67 is off: In the above, the case where the vehicle travels and the boom is raised at the same time has been described. However, when the work for raising the boom 31 is performed while the vehicle is stopped, the compressor is used. Since the load torque of the engine 41 is not so large even when 1 is operating, the boom 31 can be driven at a relatively high speed. In this case, the selection switch 67 may be turned off. When the selection switch 67 is turned off, the output terminal Q of the one-shot multi IC 63 and the relay 65 are cut off, so that the relay 65 is always in the on state regardless of whether the pressure switch 62 is on or off. As long as it is turned on, the compressor 1 can maintain the operating state even when the boom is raised, and the cooling function can be secured.

In the configuration of the above embodiment, the engine 4
1 is a prime mover, the boom 31 is a working machine, the boom cylinder 33 is a working machine hydraulic cylinder, the pressure switch 62 is a detecting means, a one-shot multi IC 63, an integrating circuit 64.
The relay 65 constitutes a control means, and the selection switch 67 constitutes a command means. Also, air conditioner switch 1
2 is ON for output of compressor operation command, ON of pressure switch 62 is for output of high load signal, selection switch 67
Turning off corresponds to the output of the release command.

FIG. 4 shows another embodiment in which the same parts as those in FIG. 1 are designated by the same reference numerals. In the present embodiment, the one-shot multi IC 63 and the integrating circuit 64 are not provided, but the pressure switch 62 and the relay 65 are connected via the selection switch 67. According to this configuration,
When the pressure switch 62 is turned on (when a high load signal is output) while the compressor 1 is operating and the selection switch 67 is on, the relay 65 is turned off and the electromagnetic clutch 1a of the compressor 1 is in the power-off state. Then, the compressor 1 is stopped. The stopped state of the compressor 1 continues until the pressure switch 62 is turned off. When the pressure switch 62 is turned off, the relay 65 is turned on, the electromagnetic clutch 1a enters the power transmission state, and the compressor 1 operates. This also allows the compressor 1 to be stopped when the boom is raised, and the same effect as described above can be obtained.

The structure of the detecting means is not limited to the pressure switch 62 described above. For example, as shown in FIG. 5, a pressure switch 62 ′ that is turned on when the pressure in the pipeline 71 becomes a predetermined value or more, and a switch 81 that is turned on when the boom directional control valve 53 is switched to the raised position U are used. One-shot multi I only when switches 62 'and 81 are on (when the boom is raised and the load is above a predetermined value)
Power may be supplied to the C63 or the relay 65. According to this, the operation / non-operation of the compressor 1 can be controlled in consideration of the weight of the earth and sand loaded in the bucket 32. Alternatively, the pressure switch 62 'may not be provided, and power may be supplied to the one-shot multi IC 63 or the relay 65 without fail when the switch 81 is on (when the boom is raised).

Although the wheel loader has been described above, the present invention can be applied to other vehicles having a working machine. Therefore, the working machine is not limited to the boom and the bucket.

[0027]

According to the present invention, when it is detected that the load on the working machine exceeds a predetermined value, the power transmission to the compressor of the prime mover is cut off regardless of the presence or absence of the compressor operation command. For example, when performing work requiring high horsepower while the vehicle is traveling, it is possible to automatically cut off the power transmission of the prime mover to the compressor, reduce the load torque of the engine, and increase the engine speed. Therefore, it is possible to prevent the vehicle traveling speed from decreasing and the working machine ascending speed to decrease without performing the operation of releasing the compressor operation command during heavy work, thereby improving the work efficiency. In particular, according to the invention of claim 4, when the release command is output, the power of the prime mover is transmitted to the compressor in response to the compressor operation command even when the high load signal is output. When performing work requiring high horsepower without traveling, that is, when the engine load torque is not so large, work can be performed without shutting off power to the compressor, and cooling performance can be secured.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a cooling device of a wheel loader and a working hydraulic circuit according to an embodiment.

FIG. 2 is an input and output of a one-shot multi IC,
The time chart which shows the ON / OFF state of the electromagnetic clutch of a compressor.

FIG. 3 is a diagram showing a relationship between engine speed and torque.

FIG. 4 is a diagram showing a configuration of a cooling device of a wheel loader and a working hydraulic circuit according to another embodiment.

FIG. 5 is a diagram showing a modified example of the cooling device.

FIG. 6 is a diagram showing a conventional cooling device.

FIG. 7 is a diagram showing an example of work by a wheel loader.

[Explanation of symbols]

 1 Compressor 1a Electromagnetic clutch 12 Air conditioner switch 14 Battery relay 15 Air conditioner relay 18 Condenser relay 19 Fan switch 31 Boom 32 Bucket 33 Boom cylinder 34 Bucket cylinder 41 Engine 42 Torque converter 51 Working hydraulic pump 52 Directional control valve for bucket 53 Direction for boom Control valve 61 Constant voltage circuit 62 Pressure switch 63 One-shot multi IC 64 Integration circuit 65 Relay 67 Selection switch

Claims (4)

[Claims] 1. A working vehicle equipped with a working hydraulic pump driven by a prime mover and a working machine hydraulic cylinder driven by discharge oil from the hydraulic pump to drive the working machine, and a compressor operation command. In response to the above, in a cooling device configured to transmit the power of the prime mover to a cooling compressor to operate the compressor, a high load signal is output by detecting that the load of the working machine has exceeded a predetermined value. An air conditioner for a work vehicle, comprising: a detection unit; and a control unit that cuts off power transmission to the compressor of the prime mover regardless of the presence or absence of the compressor operation command when the high load signal is output. . 2. The control means transmits power of the prime mover to the compressor in response to the compressor operation command when a predetermined time elapses after power transmission to the compressor of the prime mover is cut off. The cooling device for a work vehicle according to claim 1, wherein the cooling device is for a work vehicle. 3. The control means, when the output of the high load signal is cut off after the power transmission of the prime mover to the compressor is cut off, the control means outputs the power of the prime mover in response to the compressor operation command. The cooling device for a work vehicle according to claim 1, wherein the cooling device is transmitted to a compressor. 4. A command means for outputting a cancel command for canceling the power cutoff to the compressor is further provided, and the control means, when the cancel command is outputted,
The cooling device for a work vehicle according to any one of claims 1 to 3, wherein power of a prime mover is transmitted to the compressor in response to the compressor operation command even when the high load signal is output.