JP2002047965A - Hydraulic controller for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic controller for construction equipment capable of preventing engine overheat and maintaining the operability and work efficiency without increasing cooling capacity of a radiator set to an optimum condition under normal operation conditions. SOLUTION: A governor controller 8 receives a temperature signal from a detection means 22 detecting a temperature of cooling water or hydraulic fluid of an engine 1 to output a signal for increasing the number of revolutions of the engine by the predetermined number to an engine control means when a temperature of cooling water or hydraulic fluid exceeds the predetermined temperature, and a pump controller 12 outputs a signal for changing a matching point with engine torque of absorption torque of a hydraulic pump 2 to a control means 16 of the hydraulic pump 2 simultaneously when the governor controller 8 increases the number of revolutions of the engine by the predetermined number.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a construction machine such as a hydraulic shovel, and more particularly to a hydraulic control device capable of preventing overheating of a construction machine having a variable displacement hydraulic pump directly connected to an engine. About.

[0002]

2. Description of the Related Art Conventionally, as a cooling device for an engine of a construction machine, a method of driving a cooling fan by a transmission means such as a pulley and a V-belt directly connected to the crankshaft of the engine has been often used. In this method, since the rotation speed of the cooling fan depends on the rotation speed of the engine and is substantially fixed, the size (cooling capacity) of the radiator and the rotation speed of the cooling fan in a steady state are adjusted in accordance with the maximum ambient temperature level. Set the number. In other words, the cooling capacity and the air volume that are always equal to or more than the predetermined amount are ensured so that the engine does not overheat even at the maximum atmospheric temperature under the operating conditions.

In a construction machine having such a cooling fan directly connected to the engine and having a variable displacement hydraulic pump driven by the engine, there are several hydraulic control devices capable of preventing overheating without increasing the cooling capacity of the radiator. For example, Japanese Patent Laid-Open Publication No.
There is one disclosed in JP-A-8666. According to the publication, the cooling water temperature of the prime mover is detected, and when the temperature becomes equal to or higher than a predetermined temperature, the discharge amount of the variable displacement hydraulic pump is reduced to reduce the load on the prime mover. It is described that this makes it possible to prevent overheating under any condition without increasing the cooling capacity of the radiator.

[0004] For example, there is one disclosed in Japanese Patent Application Laid-Open No. 7-71253. According to the publication, the engine cooling water temperature is detected, and when the temperature exceeds a specified value, the engine speed is reduced and the discharge amount of a variable displacement hydraulic pump driven by the engine is reduced to reduce the engine speed. The load is reduced and overheating is prevented. At the same time, it is described that the matching point between the engine torque and the absorption torque of the variable displacement hydraulic pump can be changed to a region with high fuel efficiency to save energy.

[0005]

However, the above-mentioned prior art has the following problems. Under normal (steady-state) operating conditions, the cooling capacity is more than necessary, so that not only energy is wasted but also component (radiator, cooling fan, etc.) costs are high. Further, there is a problem that ambient noise due to rotation of the engine and rotation of the cooling fan is also large in a steady state. Further, in the techniques disclosed in Japanese Patent Application Laid-Open Nos. 6-248666 and 7-71253, when the cooling water temperature exceeds a predetermined value, the discharge amount of the variable displacement hydraulic pump is reduced. However, there is a problem that the output of the hydraulic pump is reduced and the working efficiency is reduced.

The present invention focuses on the above-mentioned conventional problems and can prevent engine overheating without increasing the cooling capacity of a radiator which is optimally set under normal operating conditions, and maintain operability and work efficiency. It is an object of the present invention to provide a hydraulic control device for a construction machine that can be used.

[0007]

In order to achieve the above object, a first invention of a hydraulic control device for a construction machine according to the present invention comprises an engine and an engine control means for controlling the number of revolutions of the engine. A cooling fan directly connected to the engine, a variable displacement hydraulic pump driven by the engine to supply hydraulic oil to the work machine actuator, pump control means for controlling the absorption torque of the hydraulic pump, Detecting means for detecting the temperature of the cooling water or hydraulic oil, a governor controller for outputting a signal to the engine control means to control the number of revolutions of the engine, and outputting a signal to the pump control means to control the absorption torque of the hydraulic pump The governor controller receives a temperature signal from the detection means. Then, when the temperature of the engine cooling water or hydraulic oil becomes equal to or higher than a predetermined temperature, a signal for increasing the engine speed by a predetermined amount is output to the engine control means,
The pump controller is configured to output a signal for changing a matching point of the absorption torque of the hydraulic pump with the engine torque to the pump control means at the same time that the governor controller increases the engine speed by a predetermined amount.

According to the first aspect, a sign of overheating is detected based on the temperature of engine cooling water or hydraulic oil,
It is determined that overheating is close when the temperature is equal to or higher than a predetermined temperature before the temperature at which overheating occurs,
Only at this time, the engine speed is increased by a predetermined amount from the steady state, whereby the airflow of the cooling fan directly connected to the engine is increased, so that overheating can be prevented. For this reason, the engine and the cooling fan speed can be kept low during a steady state, so that energy loss and noise can be reduced. Also, when the overheating is near, the engine rotational speed is increased by a predetermined amount, and at the same time, the matching point of the absorption torque of the hydraulic pump for the work equipment actuator with the engine torque is changed. It does not hinder the operability and work efficiency of the work machine actuator.

A second invention is based on the first invention, wherein the matching point is maintained on a constant horsepower line of the engine.

According to the second aspect of the present invention, the engine output horsepower and the absorption horsepower of the working machine actuator hydraulic pump are constant even if the engine speed is increased during overheating prevention, so that the working efficiency can be maintained without any change. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. The first embodiment will be described with reference to FIGS. First, the configuration of the hydraulic control device of the present embodiment will be described with reference to FIG. The engine 1 drives a variable displacement hydraulic pump 2 and a control pump 3 for generating pilot pressure. The direction switching valve 4 controls the flow of the hydraulic oil discharged from the hydraulic pump 2 and supplies the hydraulic oil to the hydraulic actuator 5, and the hydraulic actuator 5 drives a load 6 such as a working machine. A cooling fan 20 is connected to an output shaft of the engine 1 via a transmission means such as a pulley and a V-belt. The cooling fan 20 blows air to a radiator 21 disposed downstream of the cooling fan 20 in the cooling air flow. Then cool the cooling water.

The throttle dial 7 is for setting the rotation speed of the engine 1 in a steady state, and outputs a set rotation speed signal corresponding to the stroke to the governor controller 8. The engine 1 is provided with a temperature sensor 22 for detecting an engine coolant temperature, and a coolant temperature signal from the temperature sensor 22 is input to the governor controller 8.

The governor controller 8 is constituted mainly by a central processing unit such as a microcomputer, and receives a stroke signal of the throttle dial 7 and a cooling water temperature signal of the temperature sensor 22 to perform a predetermined calculation as described later. Perform processing. Then, based on the result of the arithmetic processing, a command signal corresponding to the magnitude of the stroke signal of the throttle dial 7 and a predetermined engine set speed corresponding to the cooling water temperature is output to the governor motor 9, and the governor motor 9 is output. A fuel injection amount is controlled by controlling the rotation of a fuel injection lever of an injection pump 10 connected to the pump 9, and a set rotation speed signal is output to a pump controller 12 described later. The operation amount of the governor motor 9 is detected by the potentiometer 11 as a fuel injection amount, and this detection signal is fed back to the governor controller 8.

FIG. 1 shows an example in which a fuel injection control unit including a governor motor 9 and an injection pump 10 and a mechanical governor are mounted on the engine 1, but the present invention is not limited to this, and so-called electronic A formula governor may be attached. In the case of an electronic governor, the control rack position and the timer advance angle are controlled by an actuator (not shown) based on the control rack position, engine speed, cooling water temperature, and the like detected by a detection sensor (not shown).

The hydraulic pump 2 includes a pump controller 12
From the TVC valve 13 and LS valve 14
Control means 1 comprising a servo valve 15
Via 6, the absorption torque (displacement volume) is controlled. The pump controller 12 receives the actual rotation speed signal from the engine rotation sensor 17 for detecting the rotation speed (the rotation speed per unit time) of the engine rotation shaft and the set rotation speed signal from the governor controller 8 and receives the set rotation speed. A command signal of a predetermined pump discharge amount is output to the TVC valve 13 so as to set the absorption torque (displacement volume) of the hydraulic pump 2 according to the number. TVC valve 13
Controls the pump discharge amount in response to the command signal so that the pump does not discharge at a predetermined flow rate or more corresponding to the discharge pressure of the hydraulic pump 2 so that the absorption horsepower of the pump does not exceed the engine horsepower. The horsepower control is performed, and a command signal of a predetermined pump discharge amount is output to the LS valve 14. The LS valve 14 controls the pump discharge amount in accordance with the pressure difference between the discharge pressure of the hydraulic pump 2 and the load pressure (that is, the outlet pressure of the direction switching valve 4), and a pilot signal set by a solenoid valve 18. The control command for the pump discharge amount is output to the servo valve 15 so that the differential pressure becomes substantially constant based on the above. The servo valve 15 controls the discharge amount of the hydraulic pump 2 to control the absorption torque based on the control command. The solenoid valve 18 is connected to the pump controller 12
The pilot pressure from the control pump 3 is converted into a pilot signal in accordance with the differential pressure setting signal of the LS valve 14 from the above, and the pilot signal for setting the differential pressure is applied to the LS valve 14.

The pump controller 12, like the governor controller 8, is mainly composed of a central processing unit such as a microcomputer. Pump controller 1
2. When a set speed signal indicating that the cooling water temperature becomes equal to or higher than a predetermined value and the engine speed of the engine 1 is increased to a predetermined speed is input from the governor controller 8, the hydraulic pump is adjusted to an engine torque corresponding to the predetermined speed. A command signal of a predetermined pump discharge amount for changing the matching point of the absorption torque of No. 2 is output to the TVC valve 13. This gives T
The VC valve 13 controls the pump discharge amount in response to the command signal so that the pump does not discharge at a predetermined flow rate or more according to the discharge pressure of the hydraulic pump 2, and changes the matching point of the absorption torque of the hydraulic pump 2. Do. Since the TVC valve 13, the LS valve 14, and the servo valve 15 are well-known technologies, detailed description will be omitted.

Next, switching control of the engine speed at the time of preventing overheating will be described with reference to FIGS. FIG. 2 is a diagram showing the relationship between the engine speed and the coolant temperature, and FIG. 3 is a control flowchart of the engine speed. As shown in FIG. 2, the coolant temperature is controlled by switching the engine speed to N1, N2, N3 based on a predetermined coolant temperature t. That is, when the water temperature is low and steady, the engine speed N (rpm) is controlled to the speed N1 set by the throttle dial 7, and when the water temperature subsequently rises, the cooling water temperature t (° C.) becomes t ≧
At t1, the engine speed N (rpm) is changed from N1 to N2.
If t ≧ t2, switch from N2 to N3 and t> t
When it becomes 3, a predetermined alarm is displayed or an alarm is issued while N3 is kept.

However, when the water temperature falls and the engine speed N
To return the cooling water temperature t to a predetermined hysteresis width α (° C.), the engine speed N is changed from N3 to N2 and t ≦ t1 when t ≦ t2−α.
At the time of -α, each is switched from N2 to N1. Here, t1, t2, and t3 are previously set to t1 <t.
The predetermined water temperature is set to satisfy the relationship 2 <t3, and t3 is the maximum allowable temperature in this case. N1 is a rated rotation speed in a steady state (low temperature), and N3 is a rotation speed of the cooling fan 20 required to keep the cooling water temperature t below the maximum allowable temperature t3 at a preset maximum atmospheric temperature. This is a predetermined number of revolutions set based on this. N2 is a predetermined number of revolutions between N1 and N3.

Referring to FIG. 3, a control procedure of the engine speed as described above will be described. In FIG. 3, it is determined in step S1 whether the cooling water temperature t is equal to or higher than a predetermined value t1.
In the case of O, it is determined in step S2 whether the current engine speed N is N = N2 (that is, whether the water temperature is increasing or decreasing). If NO in step S2, that is, if the water temperature is rising, the governor controller 8 outputs a command signal to the governor motor 9 so as to maintain the engine speed N at N1 in step R1. If YES in step S2, that is, if the water temperature is falling, it is determined in step S3 whether the cooling water temperature t is equal to or lower than a predetermined value (t1-α). N in step S3
In the case of O, the governor controller 8 controls the governor motor 9 so that the engine speed N is maintained at N2 in step R2.
In the case of YES, the governor controller 8 outputs a signal of the governor motor 9 so as to decrease the engine speed N from N2 to N1 in step R3.

If the cooling water temperature t is equal to or higher than the predetermined value t1 in step S1, it is determined in step S4 whether or not the cooling water temperature t is equal to or higher than the predetermined value t2. It is determined whether the engine speed N is N = N3 (whether the water temperature is rising or falling). NO in step S5
In other words, when the water temperature is rising, the governor controller 8 outputs a command signal to the governor motor 9 so as to increase the engine speed N from N1 to N2 in step R4. If YES in step S5, that is, if the water temperature is falling, it is determined in step S6 whether the cooling water temperature t is equal to or lower than a predetermined value (t2-α). If NO in step S6, step R
In step 5, the governor controller 8 outputs a command signal to the governor motor 9 so that the engine speed N is maintained at N3.
In the case of ES, the engine speed N is set to N3 in step R6.
The governor controller 8 outputs a signal of the governor motor 9 so as to reduce the pressure from N to N2. Thereafter, step S1
Return the process to

If YES in step S4, it is determined whether t> t3 in step S7, and if NO, the governor controller 8 controls the governor motor 9 to increase the engine speed N from N2 to N3 in step R7. A command signal is output, and if YES, an alarm signal is output in step R8.

Next, the matching point between the engine speed and the absorption torque of the hydraulic pump will be described with reference to FIG. FIG. 4 is a diagram showing the relationship between the engine torque Te and the absorption torque Tp of the hydraulic pump 2 with respect to the engine speed N when an electronic governor is used. In the figure, points P1, P2 and P3 indicate that the engine torque Te when the engine speed N is N1, N2 and N3 is T1 respectively.
, T2, T3, and at the same time a matching point with the absorption torque Tp of the hydraulic pump 2. That is, when the governor controller 8 controls the engine speed N to N1, N2, and N3, respectively, the maximum engine torque Te corresponding to the engine speeds N1, N2, and N3 is T1, T2, and N3 based on the engine characteristics. T3 is set so that the absorption torque Tp of the hydraulic pump 2 corresponding to the engine speeds N1, N2, N3 becomes T1, T2, T3, respectively, that is, the absorption torque Tp curve is changed to the points P1, P2.
, P3, the respective pump discharge amounts are set by the pump controller 12. Here, the engine torque characteristics are set so that the engine speed during high idling converges to N2, N2, N3. The points P1, P2, and P3 are set by the governor controller 8 so as to be maintained on the constant output horsepower (PS) line of the engine 1.

According to the embodiment applied to an engine having the above-described engine torque characteristics, the governor controller 8 receives the temperature signal from the temperature sensor 22 and changes the cooling water temperature t of the engine 1 to the predetermined temperature t1,. If t2 or more, the set value of the engine speed N is set to N
2 and N3 to increase the air volume of the cooling fan 20, so that the cooling capacity is increased. As shown in FIG. 2, the cooling water temperature t is equal to or less than the maximum allowable temperature t3 even when operating under the maximum atmospheric temperature. Is controlled. When increasing the number of revolutions N of the engine 1 to N2 and N3, respectively, the pump controller 12 sets the matching point P of the absorption torque Tp of the hydraulic pump 2 to P1 corresponding to N2 and N3 as shown in FIG.
Are changed to P2 and P3 having smaller absorption torque Tp.
For this reason, even if the rotation speed N of the engine 1 is increased, a sharp decrease in the absorption torque Tp of the hydraulic pump 2 is prevented, so that
The operability of the actuator 5 and the excavating force of the working machine do not decrease. Further, the governor controller 8 determines matching points P1, P2, and absorption torque Tp of the hydraulic pump 2.
Since the output horsepower of the engine 1 at P3 is kept constant, the absorption horsepower of the hydraulic pump 2 is also kept constant, whereby the working efficiency can be maintained without any change.

In operation under the maximum atmospheric temperature,
The engine speed is N3 and the cooling water temperature t is the maximum allowable temperature t.
3 so that the cooling fan speed reduced at this time by the pulley ratio is n3.
The cooling fan speed n1 at normal temperature and steady state (engine speed N1) is expressed by the formula "n1 = n3 x N1 / N3" and is a value lower than the speed n3. Therefore, conventionally, the cooling fan was always rotated at a high rotation speed (corresponding to n3) even at room temperature.
To reduce energy loss,
Also, the noise of the engine and the cooling fan can be reduced.

Next, another embodiment applied to an engine using an electronic governor will be described with reference to FIG. FIG.
FIG. 5 is a diagram showing a relationship between the engine torque Te and the absorption torque Tp of the hydraulic pump with respect to the engine speed N in the present embodiment. This embodiment is completely the same as the first embodiment except for the regulation at the time of high idling shown in FIG. 5, and therefore, only different parts will be described. In FIG. 5, the engine speed N during high idling
Are set to converge to the same rotational speed N2.

Therefore, even if the engine speed N at the time of load is set to N1, N2, N3 to prevent overheating, the engine speed N at any setting when the load is light, that is, when the engine torque Te is small, is set. Is almost unchanged, the discharge flow rate of the hydraulic pump 2 does not change,
Therefore, the actuator 5 with respect to the operation amount of the direction switching valve 4
Are substantially equal at any setting. For this reason,
The operation feeling of the actuator 5 is good.

Next, an embodiment applied to an engine using a mechanical governor will be described with reference to FIG. FIG.
FIG. 4 is a diagram illustrating a relationship between an engine torque Te and an absorption torque Tp of a hydraulic pump with respect to an engine speed N in the embodiment. In the present embodiment, the point P shown in FIG.
4 and P5 are completely the same as in the first embodiment except for the regulation at the time of high idling, and therefore only different parts will be described. In FIG. 6, points P1, P4, P
5 indicates that the engine speed N is N1, N2, N3, respectively.
Is the point at which the engine torque Te is T1, T4, T5, and at the same time is the point of matching with the absorption torque Tp of the hydraulic pump 2. That is, the governor controller 8 sets the engine speed N to N1, N2, N3, and correspondingly, the engine torque Te becomes T1, T4, respectively.
, T5, the engine speeds N1, N2,
The pump discharge amount is controlled by the pump controller 12 so that the absorption torque Tp of the hydraulic pump 2 corresponding to N3 passes through points P1, P4 and P5, respectively. Here, the engine speeds at the time of high idling are N1a and N1, respectively.
4 and N5, where T4 and T5 are T2 of the first embodiment.
, T3.

Therefore, although the engine speed N5 at the time of high idling is larger than the corresponding engine speed N3 at the time of load, the engine torque Te when the engine speed N is switched to prevent overheating and the hydraulic pump 2
The pump absorption torque Tp is not sharply reduced by matching with the absorption torque Tp of the engine, or the engine speed and the cooling fan speed are set to low during steady state, and the temperature of the water rises and the overheating sign appears. By increasing only the rotation speed, it is possible to reduce the energy loss and the noise, and obtain the same effects as those of the first embodiment. Thereby, it can be suitably applied to a vehicle equipped with an engine having a mechanical governor.

In the above-described embodiments, an example is described in which the sign of overheating is determined based on the temperature of the engine cooling water. However, the present invention is not limited to this. For example, the determination is performed based on the temperature of the hydraulic oil. Alternatively, a plurality of levels of hydraulic oil temperature may be set in advance, and it may be determined whether or not to increase the engine speed based on whether or not the temperature level has been exceeded.

As described above, according to the hydraulic control apparatus for a construction machine according to the present invention, a sign of overheating is detected, and the engine speed is increased only when necessary.
Since the number of rotations of the cooling fan is increased to prevent overheating, the number of rotations of the cooling fan can be kept low at a steady state (normal temperature), so that energy loss can be reduced and noise due to the rotation of the fan can be reduced. When the engine speed is increased, the matching point of the absorption torque of the hydraulic pump driven by the engine is changed to the engine torque set corresponding to the engine speed, and the engine output horsepower at this matching point is Since it is made constant, the absorption horsepower of the hydraulic pump becomes constant, so that the operability of the actuator operated by the hydraulic oil of the hydraulic pump is not hindered, and the working efficiency can be maintained without any change.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a hydraulic control device for a construction machine according to an embodiment.

FIG. 2 is a diagram showing a relationship between an engine speed and a coolant temperature according to the present invention.

FIG. 3 is a control flowchart of an engine speed according to the present invention.

FIG. 4 is a diagram showing the relationship between engine torque and pump absorption torque with respect to engine speed when applied to an engine using an electronic governor.

FIG. 5 is a diagram illustrating a relationship between an engine torque and a pump absorption torque with respect to an engine speed according to another embodiment when applied to an engine using an electronic governor.

FIG. 6 is a diagram showing the relationship between engine torque and pump absorption torque with respect to engine speed when applied to an engine using a mechanical governor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Variable displacement hydraulic pump, 3 ... Control pump, 4 ... Direction switching valve, 5 ... Hydraulic actuator, 6 ... Load, 7 ... Throttle dial, 8 ... Governor controller, 9 ... Governor motor, 10 ... Injection pump , 1
1: Potentiometer, 12: Pump controller, 1
3 TVC valve, 14 LS valve, 15 servo valve, 16 pump control means, 17 engine rotation sensor, 18 solenoid valve, 20 cooling fan, 21
... a radiator, 22 ... a temperature sensor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F15B 11/00 F15B 11/00 EF Term (Reference) 2D003 AA01 AB05 AB06 BA05 BA07 DA03 DA04 DB03 DB04 DB06 DC02 FA02 3G084 AA01 AA07 BA03 BA35 DA37 EA13 FA13 FA20 FA33 3G093 AA10 AA15 BA08 CA05 DA01 DA05 DB22 EA03 FB01 3H089 AA81 AA85 BB15 BB21 DA03 DA13 DB43 EE35 FF01 FF10 GG02 JJ02

Claims (2)

[Claims] An engine (1) and the number of revolutions of the engine (1)
(N), the engine control means (9, 9A), and the engine
A cooling fan (20) directly connected to (1) and an engine
A variable displacement hydraulic pump (2) driven by (1) to supply hydraulic oil to the work equipment actuator, and a hydraulic pump
Pump control means (16) for controlling the absorption torque (Tp) of (2)
And a detection means (22) for detecting the temperature of the cooling water or hydraulic oil of the engine (1) and a signal to the engine control means (9, 9A) to control the rotation speed (N) of the engine (1). And a pump controller (12) that outputs a signal to a pump control means (16) to control the absorption torque (Tp) of the hydraulic pump (2). The governor controller (8) receives the temperature signal from the detection means (22), and when the temperature of the cooling water or the hydraulic oil of the engine (1) becomes equal to or higher than a predetermined temperature, the rotation of the engine (1). A signal for increasing the number (N) by a predetermined amount;
(9, 9A), and the pump controller (12) is a governor controller.
When (8) raises the number of revolutions (N) of the engine (1) by a predetermined amount, a signal to change the matching point (P) of the absorption torque (Tp) of the hydraulic pump (2) with the engine torque (Te) is simultaneously output. A hydraulic control device for a construction machine, wherein the hydraulic pressure control device outputs a signal to the pump control means (16). 2. The hydraulic control device for a construction machine according to claim 1, wherein the matching point (P) is maintained on a constant horsepower line of the engine (1).