JPH05312084A - Controller of hydraulic driving machine - Google Patents

Abstract

PURPOSE:To keep off any damage to a device due to high temperature as well as to prevent any possible overheat from occurring by controlling an absorption torque in a hydraulic pump, namely, engine load so as to be reduced in proportion as engine cooling water temperature is rising so high as nearer to the overheating one. CONSTITUTION:Pressure oil is fed to a hydraulic actuator 14 driving working machinery or the like from a variable displacement hydraulic pump 10 which is driven by an engine 3 and, in turn, this engine 3 is controlled by a controller 1 according to each input out of an engine speed setting switch 2 and so on. This engine 3 is provided with a governor 5 being driven and controlled by the controller via a governor actuator 4 and an injection pump 6 combinedly. In this case, the controller 1 controls an absorption torque in the hydraulic pump 10, namely, engine load so as to be reduced in proportion as engine cooling water temperature detected by a temperature sensor 7 is rising so high as nearer to the overheating one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for hydraulically driven machines such as power shovels, and more particularly to control of absorption torque of a hydraulic pump with respect to engine coolant temperature.

[0002]

2. Description of the Related Art A control device for a hydraulically driven machine such as a power shovel inputs a set rotation speed signal from an engine rotation speed setting switch and a rotation signal from a rotation detector to determine the rotation speed of the engine. The engine speed is controlled so that the rotation speed is set by the speed setting switch.

On the other hand, the control device controls the absorption torque of the hydraulic pump based on the following equation.

Tcontrol = Ttarget−α × (Nset−Nreal) (1) where Tcontrol: control torque Ttarget: target torque determined by Nset shown in FIG. 5 Nset: rotational speed Nreal set by an engine rotational speed setting switch : Rotational speed α detected by the rotation detector: Coefficient FIG. 5 shows the corresponding characteristics of the engine set rotational speed Nset and the target torque Ttarget of the hydraulic pump. According to this, the target torque Ttarget is as follows. Like

In the range (0 <Nset ≦ Nmin) where the engine set speed Nset reaches the predetermined minimum speed Nmin, the target torque Ttarget of the hydraulic pump is set to the minimum limit torque Tmin, and the engine set speed Nset is set to the predetermined minimum speed. Number N
The target torque Ttarget of the hydraulic pump is gradually increased from the minimum limit torque Tmin to the maximum limit torque Tmax within the range (Nmin <Nset ≤ Nr) exceeding the minimum rated speed Nr of the engine, and further the engine set speed is exceeded. N
When the set exceeds the specified rated speed Nr (Nset> Nr
) The target torque Ttarget of the hydraulic pump is set to the maximum limit torque Tmax.

Further, when the cooling water temperature of the engine (hereinafter referred to as engine water temperature) exceeds a predetermined overheat temperature, the control device suppresses the output of the engine to prevent overheat.
In order to prevent the device from being damaged by the engine speed control, the engine speed is forcibly reduced to a predetermined minimum speed Nmin.

[0007]

However, according to this prior art, in order that the engine water temperature does not exceed the predetermined overheat temperature, the engine speed is lowered to the minimum speed Nmin. The control is not performed, and the absorption torque of the hydraulic pump that maximizes the output of the engine is controlled by the equation (1). Therefore, there has been a problem that if the engine water temperature is in the state immediately before the overheat temperature for a long time, the engine and other devices are significantly damaged. In addition, the engine is over
It has a drawback that it easily causes heat.

The present invention has been made in view of the above circumstances, and the load on the engine is reduced as the engine water temperature approaches the overheat temperature, and damage to the device and the overheating due to the high engine water temperature occur. -An object of the present invention is to provide a control device for a hydraulic drive machine that prevents heat.

[0009]

The structure of the present invention comprises an engine, a hydraulic pump driven by the engine, and
Rotation speed detection means for detecting the rotation speed of the engine, water temperature detection means for detecting the cooling water temperature of the engine, rotation speed setting means for setting the rotation speed of the engine, and swash plate of the hydraulic pump are operated. In a control device for a hydraulic drive machine having a torque control means for matching the output torque of the engine with the absorption torque of the hydraulic pump, the absorption torque of the hydraulic pump is a maximum torque until the cooling water temperature of the engine reaches a predetermined water temperature. The cooling torque is gradually increased from the maximum torque until the cooling water temperature rises to the overheat water temperature after the cooling water temperature exceeds the predetermined water temperature. The cooling water temperature of the engine and the absorption torque of the hydraulic pump that maintain the absorption torque at the minimum torque when the overheat water temperature is exceeded. Storage means for presetting / storing the corresponding characteristic, and reading means for reading out the stored absorption torque of the storage means corresponding to the water temperature signal from the water temperature detection means from the storage means and outputting this as the first absorption torque. Calculating means for calculating a second absorption torque of the hydraulic pump based on a rotation speed signal from the rotation speed detecting means and a rotation speed setting signal from the rotation speed setting means; and a calculating means for calculating the first and second absorption torques. The smaller one is selected, and the control means for controlling the absorption torque of the hydraulic pump according to the selected absorption torque value is provided.

[0010]

According to the structure of the present invention, the absorption torque of the hydraulic pump is maintained at the maximum torque until the cooling water temperature of the engine reaches a predetermined water temperature, and the overheat is performed after the cooling water temperature exceeds the predetermined water temperature. -The absorption torque is gradually reduced from the maximum torque as the cooling water temperature increases until the cooling water temperature rises, and the absorption torque becomes the minimum torque when the cooling water temperature exceeds the overheat water temperature. Corresponding characteristics of the cooling water temperature of the engine to be maintained and the absorption torque of the hydraulic pump are stored in advance in the storage means. The reading means calculates the first absorption torque (limit torque) of the hydraulic pump corresponding to the water temperature signal from the water temperature detection means, using the corresponding characteristic stored in the storage means. On the other hand, the calculating means calculates the second absorption torque (control torque) of the hydraulic pump based on the rotation speed signal from the rotation speed detecting means and the rotation speed setting signal from the rotation speed setting means. The control means selects the smaller absorption torque of the calculated first and second absorption torques, and controls the absorption torque of the hydraulic pump according to the selected torque value.

[0011]

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

FIG. 1 is a block diagram showing the overall construction of an embodiment in which the present invention is applied to a power shovel. In this embodiment, a hydraulic actuator 14 for driving a power shovel working machine (not shown), a variable displacement hydraulic pump 10 for supplying pressure oil to the hydraulic actuator 14, and a hydraulic pump 10 for driving the hydraulic pump 10. The engine 3 mainly includes an engine speed setting switch 2, and a control device 1 that controls them.

The engine 3 is provided with a governor actuator 4 driven by a drive signal from the control device 1, a governor 5 driven by the governor actuator 4, and an injection pump 6, and the engine 3 is further provided. A temperature sensor 7 for detecting the temperature of the cooling water is provided. The engine 3 and the hydraulic pump 10 are connected by a drive shaft 8,
A rotation detection sensor 9 for detecting the rotation speed of the engine 3 is attached to the drive shaft 8. Further, the hydraulic pump 10 is provided with a movable swash plate 11, a servo actuator 12 for variably driving the inclination angle of the swash plate 11, and the swash plate 11 is inclined by the servo actuator 12. The amount of oil discharged from the hydraulic pump 10 per rotation is variable by changing the angle. Further, on the discharge side of the hydraulic pump 10, a hydraulic actuator 14 for driving an arm of a power shovel (not shown) is provided.
It is provided via an operation valve 13 for driving the.

When the water temperature signal from the temperature sensor 7 exceeds a predetermined overheat temperature to, the control unit 1 is forced to reduce the rotation speed of the engine 3 to a predetermined minimum rotation speed Nmin. A hydraulic pump 10 corresponding to the engine water temperature shown in FIG. 3 is provided with functions, and constants such as the overheat temperature to and the minimum speed Nmin are set and stored in the storage device of the control device 1. The limiting torque characteristic of
Remembered The limit torque Tlimit of the hydraulic pump 10 shown in FIG. 3 is the maximum limit torque Tmax in the temperature range (0 <t ≦ tc) where the engine water temperature is up to a predetermined cooling water temperature tc.
When the engine water temperature exceeds a predetermined cooling water temperature tc,
Temperature range approaching the bar heat temperature to (tc <t <t
o), the maximum limit torque Tmax to the minimum limit torque Tmi
It is gradually reduced to n so that the minimum limit torque Tmin is obtained at the overheat temperature to. Here, when the engine torque is set to an arbitrary engine water temperature t1 and t2 (t1 <t2), the limiting torques of the respective hydraulic pumps 10 are calculated to obtain the limiting torques T1 and T2 as shown in FIG. As is clear from the figure, as the engine water temperature exceeds the predetermined cooling water temperature tc and approaches the overheat temperature to and becomes higher, the maximum value of the limiting torque of the hydraulic pump 10 corresponding thereto decreases.

The operation of the embodiment of the present invention will be described below.
This will be described with reference to the block diagram of FIG. 1 and the operation flowchart of the control device of FIG.

When the operator operates the hydraulically driven machine by an operation lever (not shown) (step 101), the control device 1 causes the engine speed setting switch 2 to output the set speed signal (Ntarget signal) and the temperature sensor 7. Is input to determine whether or not the engine water temperature exceeds a predetermined overheat temperature to (step 102). If the engine water temperature exceeds the predetermined overheat temperature to in this determination result (t> t
o) The target engine speed Nset at this time is set to the minimum engine speed Nmin (step 104), and if the engine water temperature does not exceed the predetermined overheat temperature to (t≤to), Target engine speed Nset
Is the set speed Nta from the engine speed setting switch 2
rget (step 103). And the control device 1
Outputs a drive signal based on the target rotational speed Nset to the governor actuator 4 (step 105).

With this drive signal, the governor actuator 4
The governor actuator 4 operates the governor 5
Is driven, the injection amount of the injection pump is controlled by the governor 5, and the output torque of the engine 3 is controlled.
Further, the control device 1 controls the engine 3 from the rotation detection sensor 9.
The rotation speed signal Nreal is input to perform speed control so that the rotation speed of the engine 3 becomes the target rotation speed Nset.

On the other hand, the control device 1 calculates the control torque Tcontrol of the hydraulic pump 10 by the above equation (1) using the input rotation speed signal Nreal and the target rotation speed Nset (step 106).

Further, the control device 1 calculates the limiting torque Tlimit of the hydraulic pump 10 corresponding to the inputted water temperature signal t from the temperature sensor 7 from the limiting torque characteristic table shown in FIG. 3 (step). 107). Then, the control device 1 compares these calculated control torque Tcontrol and limit torque Tlimit (step 108),
Torque control of the absorption torque Tout of the hydraulic pump 10 is performed based on the following equation.

Tout = min (Tcontrol, Tlimit) (2) That is, if the control torque Tcontrol> the limit torque Tlimit, the absorption torque Tout of the hydraulic pump 10 is limited to the limit torque T.
When the control torque is set to the limit (step 109) and the control torque Tcontrol ≤ the limit torque Tlimit, the hydraulic pump absorption torque Tout is set to the control torque Tcontrol (step 110).

Then, the control device 1 uses the hydraulic pump 10 described above.
A drive signal is output to the servo actuator 12 on the basis of the absorption torque Tout (step 111). This allows
The servo actuator 12 operates and the servo actuator 12 variably drives the inclination angle of the swash plate 11 of the hydraulic pump 10 to control the amount of oil discharged from the hydraulic pump 10, that is, the absorption torque.

FIG. 4 shows the corresponding characteristics between the rotational speed of the engine 3 and the absorption torque of the hydraulic pump 10 controlled as described above, and the engine water temperatures t1 and t are arbitrary.
Absorption torque T1 of the hydraulic pump 10 when 2 (t1 <t2)
And T2 characteristics are shown. Also, the broken line in the figure is the absorption torque characteristic of the hydraulic pump 10 according to the conventional technique.
As is clear from the figure, the maximum value of the absorption torque of the hydraulic pump 10 at the engine water temperature t1 is T1, the maximum value of the absorption torque of the hydraulic pump 10 at the engine water temperature t2 is T2, and as the engine water temperature rises. (T1 <t2) The maximum value of the absorption torque of the hydraulic pump 10 at the engine water temperature is reduced (T1> T).
2).

That is, control is performed to reduce the load on the engine 3 as the engine water temperature rises. That is, as the engine water temperature rises, the output of the engine 3 is suppressed and the engine 3 is prevented from being damaged, and the engine 3 is less likely to overheat.

[0024]

As described above, according to the present invention, the absorption torque of the hydraulic pump, that is, the load on the engine is reduced as the engine water temperature rises and approaches the overheat temperature. Therefore, it is possible to prevent damage to the device due to high engine water temperature and prevent overheat.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment in which the present invention is applied to a hydraulic excavator hydraulic drive machine.

FIG. 2 is a flowchart showing the operation of the control device of FIG.

FIG. 3 is a characteristic diagram of correspondence between an engine water temperature and a limiting torque of a hydraulic pump stored in a storage device of the control device of FIG.

4 is a characteristic diagram showing the correspondence between the engine speed controlled by the control device of FIG. 1 and the absorption torque of the hydraulic pump.

FIG. 5 is a characteristic diagram showing a correspondence between an engine speed setting and a target torque according to a conventional technique.

[Explanation of symbols]

 1 Control Device 2 Engine Speed Setting Switch 3 Engine 4 Governor Actuator 7 Temperature Sensor 9 Rotation Detection Sensor 10 Hydraulic Pump 12 Servo Actuator

Claims (1)

[Claims] 1. An engine, a hydraulic pump driven by the engine, a rotation speed detecting means for detecting a rotation speed of the engine, a water temperature detecting means for detecting a cooling water temperature of the engine, and a rotation speed of the engine. In the control device for the hydraulically driven machine, there is provided a rotation speed setting means for setting the above, and a torque control means for operating the swash plate of the hydraulic pump to match the output torque of the engine with the absorption torque of the hydraulic pump. The absorption torque of the hydraulic pump is maintained at the maximum torque until the cooling water temperature reaches a predetermined water temperature, and the cooling water temperature is kept from the cooling water temperature exceeding the predetermined water temperature to the overheat water temperature. The absorption torque is gradually reduced from the maximum torque as the temperature rises, and the absorption torque is minimized when the cooling water temperature exceeds the overheat water temperature. A storage unit that presets and stores a corresponding characteristic between the cooling water temperature of the engine and the absorption torque of the hydraulic pump that is maintained at a level of R, and the storage absorption torque of the storage unit that corresponds to the water temperature signal from the water temperature detection unit. The reading means for reading from the storage means and outputting it as the first absorption torque, and the second absorption of the hydraulic pump based on the rotation speed signal from the rotation speed detecting means and the rotation speed setting signal from the rotation speed setting means. And a control unit that selects a smaller one of the first and second absorption torques and controls the absorption torque of the hydraulic pump according to the selected absorption torque value. Characteristic hydraulic drive machine control device.