JPH02153236A - Engine speed control device with supercharger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a rotation speed control device for a supercharged engine mounted on an industrial machine.

B. Prior Art FIG. 3 shows a hydraulic drive circuit using a conventional supercharged engine. A variable displacement hydraulic pump 2 and a fixed hydraulic pump 3 are driven by an engine 1 equipped with a supercharger, and a flow control valve 5 is switched and controlled by pilot pressure from a pilot valve 4 whose primary pressure is the discharge pressure of the fixed hydraulic pump 3. Then, the hydraulic cylinder 6 is driven to expand and contract with the discharge flow rate of the variable displacement hydraulic pump 2. The rotation speed detection sensor 7 detects the rotation speed of the supercharged engine 1.
The rotation speed signal N is detected and input to the control circuit 8, and when the rotation speed signal N becomes less than a predetermined first reference rotation speed NL, a drive signal EV is sent to the solenoid section 9S of the electromagnetic switching valve 9. When the second reference rotation speed NU is exceeded, the transmission of the drive signal EV is stopped and the electromagnetic switching valve 9 is switched to the b position.
switch to position a. As a result, when the engine speed is below the first reference speed NL, the discharge pressure of the fixed hydraulic pump 3 is guided to the pump regulator 10, and the discharge volume of the variable displacement hydraulic pump 2 is reduced, that is, the pump input horsepower is controlled to be small. . Furthermore, when the rotational speed signal becomes equal to or higher than a predetermined second reference rotational speed Nυ during the horsepower reduction control, the horsepower reduction control is canceled.

This type of horsepower reduction control is performed when the engine speed is in the medium to low speed range to prevent the engine from stalling due to a delay in the rise of boost pressure when the engine speed decreases due to load. , the first reference rotation speed mentioned above is a little higher than the rotation speed at which Ens I- occurs, and the second reference rotation speed is several hundred rpm higher than the first reference rotation speed.
Il+ is set to high rotation speed.

C0 Problems to be Solved by the Invention In this way, in the conventional device, as shown in FIG. Horsepower reduction control is executed to reduce the pump input horsepower by reducing the discharge volume of the hydraulic pump 2, and when the second reference rotation speed NO is exceeded, the horsepower reduction control is canceled.

Therefore, in the region below the first reference rotation speed NL or in the region between the first reference rotation speed NL and the second reference rotation speed NU, the boost pressure is high and the engine horsepower is higher than the predetermined value. Although there is no need to reduce the pump input horsepower (there is no need to execute horsepower reduction control) in this operating region, horsepower reduction control is executed in this operating region, and the engine horsepower is not used effectively. There was a problem in that the discharge capacity of the hydraulic pump 2 decreased and the working speed became slow. In particular, in order to prevent hunting due to execution/cancellation of horsepower reduction control, the first reference rotation speed N is set as described above.
L and a second reference rotation speed NLI are provided, and the rotation speed difference is several hundred R, P, M.

Therefore, once the horsepower reduction control is entered, the horsepower reduction control is not canceled unless the rotational speed increases relatively, which poses a particular problem. In addition, the work speed becomes slower due to reduced horsepower, so
Continuing unnecessary horsepower reduction control also had problems in terms of workability.

A technical object of the present invention is to perform horsepower reduction control in consideration of supercharging pressure in order to effectively utilize engine horsepower.

Means for Solving the Problems 00 To be explained with reference to FIG. Applies to control equipment.

The above-mentioned technical problem is solved by the following configuration.

A rotation speed detection sensor 7 that detects the rotation speed of the supercharged engine 1, a supercharging pressure detection sensor 21 that detects the supercharging pressure of the supercharged engine 1, and a horsepower reduction command that controls the discharge volume of the regulator 10. and control means 25 and 9 for reducing the amount. This control means 25.9 is configured such that ■the engine rotation speed is the first
When the engine speed is below the reference speed and the boost pressure is below the reference pressure, the regulator 10 reduces the discharge specific volume of the variable displacement hydraulic pump 2 to perform horsepower reduction control, and during this horsepower reduction control, the engine speed is The second reference rotation speed is higher than the first reference rotation speed.
(2) The horsepower reduction control is canceled when the reference rotation speed exceeds the reference rotation speed, and the horsepower reduction control is also canceled when the supercharging pressure exceeds the reference pressure during the horsepower reduction control.

Based on the E0 operating engine speed and boost pressure, the control means 25,
In step 9, execution and cancellation of the horsepower reduction control are controlled as described in (1) to (2) above. Therefore, instead of simply reducing horsepower when the engine speed is below the first reference speed as in the past, when the engine speed is below the first reference speed and the boost pressure is below the reference pressure, Horsepower reduction control is performed, and even if the engine speed is below the first reference speed, the horsepower is not reduced in an operating range where the supercharging pressure is higher than the reference pressure. Furthermore, once the horsepower reduction control is executed, conventionally the horsepower reduction was not canceled until the engine speed exceeded the second reference speed, but in the present invention, when the boost pressure exceeds the reference pressure, The horsepower reduction control is also canceled. As a result, in an operating region where the boost pressure is higher than the reference pressure and horsepower above a predetermined value is obtained, unnecessary horsepower reduction control is not executed, and the engine horsepower in this operating region can be used effectively. Work speed can also be improved.

In addition, in Section 2 and Section E of ``Detailed Explanation of the Present Invention'', figures of Examples are used to make the present invention easier to understand, but the present invention is not limited to the Examples. .

F. Embodiment An embodiment of the present invention will be described based on FIGS. 1 and 2. Portions similar to those in FIG. 3 are given the same characteristics, and only the differences will be explained.

A supercharging pressure detection sensor 21 that detects the supercharging pressure of the supercharged engine 1 and outputs a supercharging pressure signal P proportional to the magnitude thereof is attached to the engine. Further, a first function generator 22 receives a boost pressure signal P and outputs a high level signal or a low level signal corresponding to the boost pressure signal P, and a first function generator 22 receives an engine rotation speed signal N and outputs a high level signal or a low level signal corresponding thereto. A control circuit 25 is constituted by a second function generator 23 that outputs a signal, and an ant gate 24 that takes the AND of the outputs of both function generators 22 and 23.

The output of the AND gate 24 is connected to the solenoid section 9S of the electromagnetic switching valve 9 as a drive signal EV.

The first function generator 22 outputs a high level signal when the supercharging pressure is in the range from O to the reference pressure Pr, and outputs a low level signal when the supercharging pressure exceeds the reference pressure Pr. The second function generator 23 outputs a high level signal in the range from 0 to the second reference rotation speed NU when the engine rotation speed increases after falling below the first reference rotation speed N. When the engine speed exceeds the reference speed NU, a low level signal is output and the engine speed decreases.
A low level signal is output in a region exceeding the first reference rotation speed NL (<NU), and a high level signal is output in a region below the first reference rotation speed NL. The above Pr and NLI Nu are predetermined values.

AND gate 24 connects first and second function generators 22
．． 23 outputs a high level signal, that is, a drive signal (horsepower reduction command) EV to the solenoid section 9s under operating conditions that both output high level signals. Therefore, horse power reduction control is performed as shown in Tables 1 and 2 below depending on whether the engine is accelerating or decelerating.

Specifically, horsepower reduction control is performed, for example, as shown in time chart 1- in FIG.

Table 1 Table 2 According to such a configuration, when the engine speed and boost pressure fluctuate as shown in Figure 2, conventionally, horsepower reduction control is performed in the operating ranges R1, R2, and R3 as shown by the broken lines. In contrast, in this embodiment, horsepower reduction control can be performed only in the operating region R1. Therefore, in the operating ranges R2 and R3, the engine horsepower can be used more effectively than before, and there is no reduction in the working speed in the operating ranges R2 and R3. Nmax is the no-load maximum rotation speed.

Note that the present invention executes horsepower reduction control when the engine speed is below the first reference speed NL and the boost pressure is below the reference pressure Pr, as in operating regions 1 and 5 of Tables 1 and 2, and the engine The present invention is characterized in that the horsepower reduction control is canceled when the rotational speed exceeds the second reference rotational speed Nυ or when the boost pressure exceeds the reference pressure Pr, and the configuration of the control circuit 25, etc. that realizes this. The operations shown in Tables 1 and 2 may be realized by various types of devices without being limited to the embodiments. Also, regulator 1
0 may be configured electrically such as a solenoid cylinder. Further, in the above description, the horsepower reduction is controlled on and off, but the horsepower reduction may be performed in multiple stages depending on the state of the boost pressure and the engine speed, thereby performing fine engine speed control. In this case, an electromagnetic proportional valve is used in place of the electromagnetic switching valve 9, and the regulator 10 is capable of changing the pump discharge volume in accordance with the electromagnetic proportional valve.

G0 Effect of the Invention According to the present invention, horsepower reduction control is performed when the engine speed is below the first reference speed and the boost pressure is below the reference pressure, and when the engine speed is below the second reference speed. Since the horsepower reduction control is canceled when the boost pressure exceeds the reference pressure or when the boost pressure exceeds the reference pressure, unnecessary horsepower reduction control is not performed when the boost pressure is still above a certain level of horsepower. This makes it possible to utilize engine horsepower more effectively than before, and to improve work speed in this operating range.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a configuration diagram of a device for driving a hydraulic circuit with an engine equipped with an engine speed control device according to the present invention, and FIG. is a time chart of engine speed, boost pressure, and pump input horsepower. FIG. 3 is a diagram showing the configuration of a conventional rotation speed control device, and FIG. 4 is a graph illustrating execution/cancellation of horsepower reduction control in the conventional example. 1: Engine with supercharger 2: Variable displacement hydraulic pump 7: Rotation speed detection sensor 9: Solenoid switching valve 10: Regulator 21: Supercharging pressure detection sensor 22.23: First and second function generator 24: AND Gate 25: Control circuit patent applicant Hitachi Construction Machinery Co., Ltd.

Claims (1)

[Scope of Claim] A rotation speed control device for a supercharged engine that drives a variable displacement hydraulic pump whose discharge volume is controlled by a regulator, comprising: a rotation speed detection sensor that detects the rotation speed of the supercharged engine; , a supercharging pressure detection sensor that detects the supercharging pressure of the supercharged engine; and based on the detection outputs from both the sensors, the engine rotation speed is equal to or less than the first reference rotation speed and the supercharging pressure is equal to or less than the reference. When the pressure is below the pressure, the regulator reduces the discharge volume of the variable displacement hydraulic pump to perform horsepower reduction control, and during this horsepower reduction control, the engine rotation speed is higher than the first reference rotation speed. The invention is characterized by comprising a control means that cancels the horsepower reduction control when the engine speed exceeds the rotational speed, and also cancels the horsepower reduction control when the boost pressure exceeds the reference pressure during the horsepower reduction control. Rotation speed control device for engines with superchargers.